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diff --git a/old/44525.txt b/old/44525.txt new file mode 100644 index 0000000..bd8c154 --- /dev/null +++ b/old/44525.txt @@ -0,0 +1,65122 @@ +The Project Gutenberg eBook, Report on the Radiolaria Collected by H.M.S. +Challenger During the Years 1873-1876, First Part: Porulosa (Spumellaria +and Acantharia), by Ernst Haeckel + + +This eBook is for the use of anyone anywhere at no cost and with +almost no restrictions whatsoever. You may copy it, give it away or +re-use it under the terms of the Project Gutenberg License included +with this eBook or online at www.gutenberg.org + + + + + +Title: Report on the Radiolaria Collected by H.M.S. Challenger During the Years 1873-1876, First Part: Porulosa (Spumellaria and Acantharia) + Report on the Scientific Results of the Voyage of H.M.S. Challenger During the Years 1873-76, Vol. XVIII + + +Author: Ernst Haeckel + + + +Release Date: December 28, 2013 [eBook #44525] + +Language: English + +Character set encoding: ISO-646-US (US-ASCII) + + +***START OF THE PROJECT GUTENBERG EBOOK REPORT ON THE RADIOLARIA COLLECTED +BY H.M.S. CHALLENGER DURING THE YEARS 1873-1876, FIRST PART: PORULOSA +(SPUMELLARIA AND ACANTHARIA)*** + + +E-text prepared by Charlene Taylor, Adrian Mastronardi, Keith Edkins, and +the Online Distributed Proofreading Team (http://www.pgdp.net) from page +images generously made available by Internet Archive (https://archive.org) + + + +Note: Images of the original pages are available through + Internet Archive. See + https://archive.org/details/reportonradiolar01haecrich + + Project Gutenberg has the other two volumes of this work. + Second Part: Subclass Osculosa; Index + see http://www.gutenberg.org/ebooks/44526. + Plates + see http://www.gutenberg.org/ebooks/44527. + + +Transcriber's note: + + Text enclosed by underscores is in italics (_Actissa_). + + Text enclosed by hash marks is in "gesperrt" + (wide-spaced) type (#Larcoidea#). + + Page numbers enclosed by curly braces (example: {25}) have + been incorporated to facilitate the use of the Index in + Part II. + + Some typographical errors in the printed work have been + corrected. They are listed at the end of the text. + + The Addenda & Errata (Second Part, pp. 1763-4) have been + applied without further comment. + + + +REPORT ON THE SCIENTIFIC RESULTS OF THE VOYAGE OF H.M.S. CHALLENGER +DURING THE YEARS 1873-76 + +Under the Command of Captain George S. Nares, R.N., F.R.S. +and the Late Captain Frank Tourle Thomson, R.N. + +Prepared Under the Superintendence of +the Late Sir C. Wyville Thomson, KNT., F.R.S., &c. +Regius Professor of Natural History in the University of Edinburgh +Director of the Civilian Scientific Staff on Board +and Now of +John Murray +One of the Naturalists of the Expedition + +ZOOLOGY--VOL. XVIII. + +FIRST PART + +Published by Order of Her Majesty's Government + + + + + + + +Printed for Her Majesty's Stationary Office +and Sold by +London:--Eyre & Spottiswoode, East Harding Street, Fetter Lane +Edinburgh:--Adam & Charles Black +Dublin:--Hodges, Figgis, & Co. +1887 + +Price (in Two Parts, with a Volume of Plates) L5, 10s. + + + + +CONTENTS. + + + + +REPORT on the RADIOLARIA collected by H.M.S. CHALLENGER during the years +1873-1876. + +By ERNST HAECKEL, M.D., Ph.D., Professor of Zoology in the University of +Jena. + +FIRST PART.--PORULOSA. + +(#SPUMELLARIA AND ACANTHARIA.#) + + + +EDITORIAL NOTES. + + +The Report on the RADIOLARIA by Professor Ernst Haeckel of Jena occupies +the whole of the present Volume, the text being bound up in Two Separate +Parts and the Plates in a Third Part. The Report forms Part XL. of the +Zoological Series of Reports on the Scientific Results of the Expedition, +and is the largest single Report of the series which has up to this time +been published. + +The Manuscript of the Systematic Part was written by Professor Haeckel in +the English language, and was received by me in instalments on the 12th +August 1884, 13th July and 4th December 1885, and 3rd June 1886. The +Introduction was written in German and was translated into the English +language by Mr. W. E. Hoyle of the Challenger Editorial Staff; the German +text being received in instalments between the 15th July 1886, and the 25th +January 1887. + +The Challenger Naturalists found the representatives of this group of +animals to be universally distributed throughout ocean waters, and their +dead remains to be nearly equally widely distributed over the floor of the +ocean, the relative abundance and the species differing, however, with +change of locality, and their abundance or variety being intimately +connected with some of the most interesting and intricate problems of +general oceanography. + +It was a fortunate circumstance that so distinguished a Naturalist, with +such an intimate knowledge of the RADIOLARIA, should have been willing to +undertake the laborious examination and description of the extensive +collections made during the Expedition. Professor Haeckel has devoted ten +years of his life to this work, and this Report sets forth the results of +his labours, on the conclusion of which he will be congratulated by all +Naturalists. The entire literature of the RADIOLARIA (from 1834 to 1884) is +completely recorded, and the older species (both living and fossil) +redescribed, so that the Report is a complete Monograph, which will be an +invaluable aid to all future Investigators. + + + + CHALLENGER OFFICE, 32 QUEEN STREET, + EDINBURGH, _1st February 1887._ + + + + +THE + +VOYAGE OF H.M.S. CHALLENGER. + + + +#ZOOLOGY.# + + + + Report on the RADIOLARIA collected by H.M.S. Challenger during the Years + 1873-76. By ERNST HAECKEL, M.D., Ph.D., Professor of Zoology in the + University of Jena. + + + + +PREFACE. + + +The significance of the Radiolaria in regard to the relations of life in +the ocean has been increased in a most unexpected manner by the discoveries +of the Challenger. Large swarms of these delicate Rhizopoda were found not +only at the surface of the open ocean but also in its different +bathymetrical zones. Thousands of new species make up the wonderful +Radiolarian ooze, which covers large areas of the deep-sea bed, and was +brought up from abysses of from 2000 to 4000 fathoms by the sounding +machine of the Challenger. They open a new world to morphological +investigation. + +When ten years ago (in the autumn of 1876) I accepted the enticing +invitation of Sir Wyville Thomson to undertake the investigation of these +microscopic creatures, I hoped to be able to accomplish the task with some +degree of completeness within a period of from three to five years, but the +further my investigations proceeded the more immeasurable seemed the range +of forms, like the boundless firmament of stars. I soon found myself +compelled to decide between making a detailed study of a selection of +special forms or giving as complete a survey as possible of the varied +forms of the whole class; and I decided upon the latter course, having +regard both to the general plan of the Challenger Reports, and to the +interests of our acquaintance with the class as a whole. I must, however, +confess at the close of my work that my original intention is far from +having been fulfilled. The extraordinary extent and varied difficulties of +the undertaking must excuse the many deficiencies. + +The special examination of the Challenger collection was for the most part +completed in the summer of 1881; I collected its results in my Entwurf +eines Radiolarien-Systems auf Grund von Studien der Challenger-Radiolarien +(Jenaische Zeitschr. f. Naturw., Bd. xv., 1881). Since the manuscript of +this preliminary communication was completed only a few days before my +departure for Ceylon, and since I was unable to correct the proofs myself, +several errors have crept into the Prodromus Systematis Radiolarium +included in it. These have been corrected in the following more extensive +working out of it. Even at that time I had distinguished 630 genera and +more than 2000 species; but on the revision of these, which I undertook +immediately on my return from India, this number was considerably +increased. The total number of forms here described amounts to 739 genera +and 4318 species; of these 3508 are new, as against 810 previously +described. In spite of this large number, however, and in spite of the +astonishing variety of the new and marvellous forms, the riches of the +Challenger collection are by no means exhausted. A careful and patient +worker who would devote a second decade to the work, would probably +increase the number of new forms (especially of the smaller ones) by more +than a thousand; but for a really complete examination, the lifetime of one +man would not suffice. + +The richest source of the Challenger material is the Radiolarian ooze of +the central Pacific Ocean (Stations 265 to 274). This remarkable deep-sea +mud consists for the greater part of well-preserved siliceous shells of +Polycystina (SPUMELLARIA and NASSELLARIA). Not less important, however, +especially for the study of the ACANTHARIA and PHAEODARIA, are the +wonderful preparations stained with carmine and mounted in Canada balsam on +the spot by Dr. John Murray. One such preparation (_e.g._, from Station +271) often contains twenty or thirty, sometimes even fifty new species. In +many of these preparations the individual parts of the unicellular organism +are so well preserved that they show clearly the characteristic +peculiarities of the legions and orders. Since the material for these +preparations was taken with the tow-net, not only from the surface of the +sea but also from different bathymetrical zones, it furnishes valuable +conclusions regarding the chorology, as well as the physiology and +morphology of the group. For many new discoveries I am indebted to the +study of such preparations, of which I have examined about a thousand from +168 different Stations (compare s 240). In addition to these about 100 +bottles were handed to me, containing partly bottom-deposits, partly +tow-net gatherings. + +Sir Wyville Thomson, who directed the investigations of the Challenger with +so much devotion, and only partly saw its results, has laid me under a deep +debt of obligation; not less is this the case, however, with his successor, +Dr. John Murray. I am especially indebted to both gentlemen for the freedom +they have allowed me in the carrying out of my work, and especially for the +permission to include a description of all known Radiolaria in the +Challenger Report, which has thus become a second edition many times +enlarged of my Monograph published in 1862. Since all previous literature +of the subject has been consulted and critically revised, it is hoped that +this Report will form a useful foundation for future investigations. All +names of sufficiently described Radiolaria published during the first half +century of our knowledge of the class (from 1834 to 1884), are inserted in +alphabetical order in the index at the end of this work. + +In addition to the treasures of the Challenger, my own collection of +Radiolaria has yielded many new forms whose description is here included. +On my journeys to the Mediterranean (an account of which is given in the +introduction to my Monograph of the Medusae), I have given special +attention to these delicate microscopic organisms for more than thirty +years. Besides the various points on the Mediterranean, the Atlantic Ocean +at the Canaries (in the winter of 1866-67) yielded many interesting new +forms; whilst my voyage across the Indian Ocean, from Aden to Bombay, in +November 1881, thence to Ceylon and back by Socotra in March 1882, was +still more productive. In particular, some extended excursions which I had +the opportunity of making from Belligemma and Matura (at the southern +extremity of Ceylon) gave me an insight into the rich treasures of the +Indian Ocean. + +Most important, however, as regards the knowledge of the Indian Radiolaria, +are the collections which Captain Heinrich Rabbe of Bremen has so +beautifully preserved during his many voyages through that region. In the +neighbourhood of Madagascar and the Cocos Islands more especially, and also +in the Sunda Archipelago, he met with large swarms of Radiolaria, among +which were many new and remarkable forms. These were of special value for +completing the chorology, and the more so since the course of the +Challenger in the Indian Ocean lay very far to the southwards. I will +therefore take this opportunity of repeating my best thanks to Captain +Rabbe for the friendly donation of his valuable collection. + +The Radiolarian fauna of the North Atlantic Ocean, which was previously but +little known and only slightly increased by the investigations of the +Challenger, received a valuable increase from the interesting collections +made by Dr. John Murray on various expeditions to the Faeroee Islands (on +the "Knight Errant" in 1880 and on the "Triton" in 1882). A large number of +new Radiolaria were captured in the Faeroee Channel, partly at the surface +of the Gulf Stream, partly at various depths, and the proof was thus +furnished that at certain points in the North Atlantic Ocean Radiolaria are +very richly developed. I am further indebted to Dr. John Murray for the +free use of this important material as well as for much other assistance in +the carrying out of my work. Another rich source of Radiolaria I found in +the alimentary canal of pelagic animals from all seas. Medusae, +Siphonophorae, Salpae, Pteropoda, Heteropoda, Crustacea, &c., which live +partly at the surface of the sea and partly at various depths, and swallow +large masses of Radiolaria, often contain numbers of their shells +well-preserved in their intestine. The alimentary canal of Fishes and +Cephalopods too, which live upon these pelagic animal frequently contains +considerable quantities of siliceous shells; and another newly discovered +source has been found in the coprolites of the Jurassic period, which +consist largely of Radiolarian skeletons. + +In the investigation of this complicated system of organisms, I have +endeavoured on the one hand to give accurately the forms and dimensions of +the species observed, and on the other hand to present a survey of the +relationships of the different genera and families; and in this I have +striven especially to combine the phylogenetic aims of the natural system +with the essentially artificial divisions of a practical classification. +Being, however, a conscientious supporter of the theory of descent, I can +of course lay no stress upon the value of the categories, which are here +distinguished as Legions, Orders, Families, Genera, &c. All these +artificial systematic grades I regard as of merely relative value; and from +the same cause I attach no importance to the distinction of all the species +here described; many of them are probably only developmental stages, and +like my predecessors I have determined their boundaries on subjective +grounds. In the systematic working out of so much material one always runs +the risk of doing either too much or too little in the way of creating +species; but in the light of the theory of descent this danger is of no +consequence. + +In the carrying out of this extensive task the friendly aid of Dr. Reinhold +Teuscher of Jena was of the greatest benefit to me; at my request he was at +the trouble of making a large number of accurate drawings with the camera +lucida, and he also undertook a long series, amounting to some 8000, +accurate micrometric measurements, which were of the greatest value in the +attempt to settle the important question of the constancy of the various +species; I have alluded to this in a note at the conclusion of the Report +(p. 1760). My best thanks are due to Dr. Teuscher for the patient and +careful manner in which he discharged these tedious tasks. + +The figures of new species of Radiolaria (about 1600 in number) which +appear in the atlas of one hundred and forty plates accompanying this +Report, were nearly all drawn with the camera lucida, partly by Mr. Adolph +Giltsch and partly by myself. The names of the genera which appear at the +bottom of the plates have in many cases been changed since they were +printed off, as may be seen from the explanations which accompany them. Had +it been possible to complete the examination of the material before the +plates were commenced this might have been avoided, and in many cases a +better selection of figures might have been made. All the drawings have +been made upon the stone by the practised hand of Mr. Adolph Giltsch, in +his usual masterly manner, and his lithographic work, which has lasted +fully ten years, is the more valuable since he has himself microscopically +studied the greater part of the species figured. The fact that the atlas +presents so full a picture of the marvellous wealth of form of the +Radiolaria is especially due to his lively interest in the work, to his +unwearying care, and to his morphological acuteness. May it be the means of +inducing many naturalists to study more deeply this inexhaustible kingdom +of microscopic life, whose endless variety of wonderful forms justifies the +saying--_Natura in minimis maxima_. + + + + +CONTENTS. + + + + FIRST PART. + + GENERAL INTRODUCTION-- PAGE + + I. Anatomical Section (ss 1-140), i + Chapter I. The Unicellular Organism, i + " II. The Central Capsule, xxiv + " III. The Extracapsulum, li + " IV. The Skeleton, lxviii + + II. Biogenetical Section (ss 141-200), xciii + Chapter V. Ontogeny (Individual Development), xciii + " VI. Phylogeny (Genealogical Development), ci + + III. Physiological Section (ss 201-225), cxxviii + Chapter VII. Vegetative Functions, cxxviii + " VIII. Animal Functions, cxl + + IV. Chorological Section (ss 226-250), cxlvi + Chapter IX. Geographical Distribution, cxlvi + " X. Geological Distribution, clxiv + + V. Bibliographical Section (ss 251-254), clxxvi + + SYSTEMATIC PART, 1 + + I. Subclass PORULOSA, 6 + Legion I. SPUMELLARIA vel PERIPYLEA, 6 + Order 1. Colloidea, 10 + " 2. Beloidea, 28 + " 3. Sphaeroidea, 50 + " 4. Prunoidea, 284 + " 5. Discoidea, 402 + " 6. Larcoidea, 599 + + Legion II. ACANTHARIA vel ACTIPYLEA, 716 + Order 7. Actinelida, 728 + " 8. Acanthonida, 740 + " 9. Sphaerophracta, 795 + " 10. Prunophracta, 859 + + SECOND PART. + + II. Subclass OSCULOSA, 889 + Legion III. NASSELLARIA vel MONOPYLEA, 889 + Order 11. Nassoidea, 895 + " 12. Plectoidea, 898 + " 13. Stephoidea, 931 + " 14. Spyroidea, 1015 + " 15. Botryodea, 1103 + " 16. Cyrtoidea, 1126 + + Legion IV. PHAEODARIA vel CANNOPYLEA, 1521 + Order 17. Phaeocystina, 1542 + " 18. Phaeosphaeria, 1590 + " 19. Phaeogromia, 1642 + " 20. Phaeoconchia, 1710 + + Note on the Dimensions and Measurements, 1760 + + ADDENDA, 1761 + + ERRATA, 1763 + + INDEX, 1765 + + + + +GENERAL INTRODUCTION. + + +---- + + +ANATOMICAL SECTION. + +A SKETCH OF OUR KNOWLEDGE OF THE ORGANISATION OF THE RADIOLARIA IN THE YEAR +1884. + + +---- + + +CHAPTER I.--THE UNICELLULAR ORGANISM. + +(ss 1-50.) + +1. _Definition of the Radiolaria._--RADIOLARIA are marine Rhizopoda, whose +unicellular body always consists of two main portions, separated by a +membrane; an inner _Central capsule_ (with one or more nuclei) and an +_Extracapsulum_ (the external calymma, which has no nucleus, and the +pseudopodia); the endoplasm of the former and the exoplasm of the latter +are connected by openings in the capsule-membrane. The central capsule is +partly the general central organ of the Radiolarian cell, partly the +special organ of reproduction, since its intracapsular protoplasm, along +with the nuclei embedded in it, serves for the formation of flagellate +spores. The extracapsulum is partly the general organ for intercourse with +the outer world (by means of the pseudopodia), partly the special organ of +protection (calymma) and nutrition (sarcomatrix). The majority of +Radiolaria develop also a skeleton for support and protection, which +presents the utmost variety of form, and is generally composed of silica, +sometimes of an organic substance (acanthin). The Radiolarian cell usually +leads an isolated existence (Monozoa _vel_ Monocyttaria); only in a small +minority (of one legion) are the unicellular organisms united in colonies +or coenobia (Polyzoa _vel_ Polycyttaria). + + The extent of the Radiolaria, as limited by the above definition, which I + have made as compact as possible, differs in several important respects + from that allowed to the group by all previous diagnoses. The shortest + expression of its scope might perhaps be:--Rhizopoda with central capsule + and calymma; for the most important character of the Radiolaria, and that + by which they are distinguished from all other Rhizopoda, is the + differentiation of the unicellular body into two principal parts of equal + importance and their separation by a constant capsule-membrane. + + +2. _The Two Subclasses of the Radiolaria._--The systematic catalogue of the +Radiolaria, which forms the second part of this Report, and is brought up +to the year {ii}1884, contains 20 orders, 85 families, 739 genera, and 4318 +species. The consideration that but a small proportion of the ocean his yet +been investigated renders it likely, however, that even this large number +does not include the half of the recent species. The great progress which +our knowledge of the organisation of the Radiolaria has made, by means of +comparative study, renders it possible to arrange this enormous mass of +forms in four main divisions or legions, and these are again related in +pairs, so that two divisions of the highest rank or subclasses are +constituted, the _Porulosa_ (or _Holotrypasta_) and _Osculosa_ (or +_Merotrypasta_). + + The division of the Radiolaria into two subclasses and four legions (or + principal orders), I sought to establish in 1883 in a communication on + the Orders of the Radiolaria (Sitzb. Jena Gesellsch. Med. u. Naturwiss., + February 16, 1883). As a believer in the theory of descent, I regard all + the systematic arrangements of specialists as artificial, and all their + divisions as subjective abstractions, and hence I shall be guided in the + establishment of such groups as subclasses, legions, orders, &c., by + purely practical considerations, especially by the desire to give as + ready a survey as possible of the complex multitude of forms (compare ss + 154 to 156). + + +3. _Porulosa or Holotrypasta._--The subclass Porulosa or Holotrypasta +includes the two legions, PERIPYLEA or SPUMELLARIA, and ACTIPYLEA or +ACANTHARIA, which agree in the following constant and important +characters:--(1) The _Central Capsule_ is primitively a sphere, and retains +this homaxon form in the majority of the species. (2) The _Membrane_ of the +central capsule is everywhere perforated by very numerous minute pores, but +possesses no larger principal aperture (osculum). (3) The _Pseudopodia_ +radiate in all directions and in great numbers from the central capsule, +passing through its pores. (4) The _Equilibrium_ of the floating +unicellular body is in most Porulosa pantostatic (indifferent) or +polystatic (plural-stable), since a vertical axis is either absent, or, if +present, has its two poles similarly constituted. (5) The _Ground-forms_ of +the skeleton are therefore almost always either spherotypic or +isopolar-monaxon, very rarely zygotypic. The two legions of the Porulosa +are distinguished mainly by the skeleton of the SPUMELLARIA (or PERIPYLEA) +being siliceous, never centrogenous, nor composed of acanthin, whilst in +the ACANTHARIA (or ACTIPYLEA) it is always centrogenous and made up of +acanthin; hence in the former the nucleus is always central, in the latter +always excentric. + + +4. _Osculosa or Merotrypasta._--The subclass Osculosa or Merotrypasta +includes the two legions MONOPYLEA or NASSELLARIA, and CANNOPYLEA or +PHAEODARIA, which agree in the following constant and important +characters:--(1) The Central Capsule is originally monaxon (ovoid or +spheroidal) and retains this ground-form in most of the species. (2) The +_Membrane_ of the central capsule possesses a single large principal +aperture (osculum) at the basal pole of the vertical main axis. (3) The +_Pseudopodia_ radiate from a stream of sarcode which passes out from the +central capsule only on one side, namely, through the principal aperture. +(4) The _Equilibrium_ of the floating body is {iii}monostatic or unistable, +since the two poles of the principal axis are always more or less different +from each other. (5) The _Ground-forms_ of the skeleton are, therefore, for +the most part grammotypic (centraxon) or zygotypic (centroplan), rarely +spherotypic. The two legions of the Osculosa are distinguished chiefly by +the principal opening (osculum) being closed by a porous plate (porochora +with its podoconus) in the NASSELLARIA (or MONOPYLEA), and by a radiate +cover (operculum with its astropyle) in the PHAEODARIA (or CANNOPYLEA). + + +5. _The four Legions of Radiolaria._--The four principal groups of +Radiolaria, to which we have given the name "legions," are natural units, +since the most important peculiarities in the structure of the central +capsule are quite constant within the limits of the same legion, and since +all the forms in the same legion may be traced without violence to the same +phylogenetic stem. The four legions are, however, related to each other, in +so far as they all exhibit those characters which distinguish the +Radiolaria from other Protista. The two which compose the Porulosa (s 3) +seem somewhat more nearly related to each other than to the two which make +up the Osculosa (s 4). When, however, the attempt is made to bring them all +into a phylogenetic relationship, it undoubtedly appears that the +SPUMELLARIA (or PERIPYLEA) are the primitive stem, out of which the other +three have been developed as independent branches. All three have been +derived, probably independently, from the most ancient stem-form of the +SPUMELLARIA, the spherical _Actissa_. + + +6. _Peripylea or Spumellaria._--Those Radiolaria which we call "PERIPYLEA" +on account of the constitution of their central capsule, or "SPUMELLARIA" +on account of the nature of their skeleton, are separated from the other +three legions of the class by the combination of the following constant +characters:--(1) The _Membrane_ of the central capsule is single and evenly +perforated all over by innumerable fine pore-canals, but without any larger +principal opening (osculum). (2) The _Nucleus_ always lies centrally in the +SPUMELLARIA monozoa and is serotinous, for it divides only at a later +period into the nuclei of the spores; in the SPUMELLARIA polyzoa it is +precocious, and divides early into many small nuclei. (3) The _Pseudopodia_ +are exceedingly numerous and distributed evenly over the whole surface of +the central capsule. (4) The _Calymma_ contains no phaeodium. (5) The +_Skeleton_ is seldom wanting, is never centrogenous, and is always +siliceous. (6) The _Ground-form_ of the central capsule is originally +spherical (often modified); that of the skeleton is also spherical or, in +the majority of cases, derived in different ways from the sphere. + + +7. _Actipylea or Acantharia._--These Radiolaria which we call "ACTIPYLEA" +on account of the constitution of their central capsule, or "ACANTHARIA" +from the formation of their skeleton, are separated from the other three +legions by the combination of the following constant characters:--(1) The +_Membrane_ of the central capsule is single and {iv}perforated by numerous +fine pore-canals, which are regularly distributed in series or groups, but +without a larger principal opening (osculum). (2) The _Nucleus_ is always +excentric and generally precocious, since it divides early by a peculiar +process of budding into numerous small nuclei. (3) The _Pseudopodia_ are +very numerous and distributed regularly in groups (or series united into a +network). (4) The _Calymma_ contains no phaeodium. (5) The _Skeleton_ is +generally present, always centrogenous, and composed of acanthin. (6) The +_Ground-form_ of the central capsule is originally spherical (often +modified), that of the skeleton polyaxon (often modified). + + +8. _Monopylea or Nassellaria._--Those Radiolaria which we call "MONOPYLEA" +from the formation of their central capsule, or "NASSELLARIA" from the +nature of their skeleton, are distinguished from the other three legions of +the class by the combination of the following constant characters:--(1) The +_Membrane_ of the central capsule is single, and has only one large +principal opening (osculum) at the basal pole of the vertical main axis; +this osculum is closed by a perforated lid (porochora or operculum porosum) +from which there arises within the central capsule a peculiar cone of +threads or pseudopodia (podoconus). (2) The _Nucleus_ is usually excentric +and is always serotinous, since it only divides at a comparatively late +period into spore-nuclei. (3) The _Pseudopodia_ are not very numerous and +arise by division of a single stem or bundle of threads of sarcode, which +issues from the porochora. (4) The _Calymma_ contains no phaeodium. (5) The +_Skeleton_ (very rarely absent) is never centrogenous, but always +extracapsular and siliceous. (6) The _Ground-form_ of the central capsule +is always monaxon (with a vertical allopolar main axis), originally ovoid, +often modified; that of the skeleton is also generally monaxon, often +modified (triradial or bilateral). + + +9. _Cannopylea or Phaeodaria._--Those Radiolaria which we call "CANNOPYLEA" +from the constitution of their central capsule, or "PHAEODARIA" on account +of their peculiar phaeodium, are distinguished from the other three legions +by the combination of the following characters:--(1) The _Membrane_ of the +central capsule is double, consisting of a strong outer and delicate inner +capsule, and has only one principal opening (osculum) at the basal pole of +the vertical main axis; this osculum is closed by a radiate cover +(astropyle or operculum radiatum), from the centre of which arises an +external tubular spout (proboscis). Occasionally a few small accessory +openings (parapylae) are present besides the principal opening. (2) The +_Nucleus_ lies centrally or subcentrally in the capsule (in the vertical +main axis), and is serotinous, inasmuch as it only divides at a late period +into spore-nuclei. (3) The _Pseudopodia_ are usually very numerous and +arise from a thick sarcomatrix, formed by the spreading out of a thick stem +of sarcode, which issues from the astropyle. (4) The _Calymma_ always +contains a phaeodium or peculiar voluminous excentric mass of pigment. (5) +The _Skeleton_ (very rarely absent) is never centrogenous, always +extracapsular and formed of a silicate of carbon. (6) The {v}_Ground-form_ +of the central capsule is always monaxon (with a vertical allopolar main +axis) and generally spheroidal; that of the skeleton is very varied. + + +10. _Synopsis of the Subclasses and Legions:--_ + + +-----------------------------------------------------------------+ + | FIRST SUBCLASS. | + +-----------------------------------------------------------------+ + | PORULOSA vel HOLOTRYPASTA. | + | | + | Central capsule originally spherical, without osculum or | + | principal opening, with innumerable fine pores. | + +-----------------------------------------------------------------+ + | Legion I. | Legion II. | + | SPUMELLARIA. | ACANTHARIA. | + | (PERIPYLEA). | (ACTIPYLEA). | + +--------------------------------+--------------------------------+ + | _Central capsule_ | _Central capsule_ | + | originally spherical, | originally spherical, | + | homaxon. | homaxon. | + | | | + | _Capsule-membrane_ | _Capsule-membrane_ | + | single, | single, | + | pores innumerable, | pores numerous, | + | distributed all over. | regularly distributed. | + | | | + | _Nucleus_ central, | _Nucleus_ excentric, | + | originally spherical | (usually dividing early). | + | (usually dividing late). | | + | | | + |_Skeleton_ absent or siliceous, | _Skeleton_ always of acanthin, | + | never centrogenous. | always centrogenous. | + | | | + | _Calymma_ always | _Calymma_ always | + | without phaeodium. | without phaeodium. | + +-----------------------------------------------------------------+ + | SECOND SUBCLASS. | + +-----------------------------------------------------------------+ + | OSCULOSA vel MEROTRYPASTA. | + | | + | Central capsule originally monaxon, with an osculum at | + | the basal pole of the vertical main axis. | + +-----------------------------------------------------------------+ + | Legion III. | Legion IV. | + | NASSELLARIA. | PHAEODARIA. | + | (MONOPYLEA). | (CANNOPYLEA). | + +--------------------------------+--------------------------------+ + | _Central capsule_ | _Central capsule_ | + | originally ovoid, | always spheroidal, | + | monaxon. | monaxon. | + | | | + | _Capsule-membrane_ | _Capsule-membrane_ | + | single, | always double, | + | a porous area | an astropyle | + | (porochora) at the oral | (with radiate operculum) | + | pole of the main axis. | at the oral pole | + | | of the main axis. | + | | | + | _Nucleus_ excentric, | _Nucleus_ always spheroidal, | + | near the aboral pole | in the main axis | + | (dividing late). | (dividing late). | + | | | + | _Skeleton_ siliceous, | _Skeleton_ of a silicate, | + | usually monaxon, | always extracapsular. | + | extracapsular. | | + | | | + | _Calymma_ always | _Calymma_ always | + | without phaeodium. | with phaeodium. | + +-----------------------------------------------------------------+ + + +11. _Individuality of the Radiolaria._--Like other Protozoa the Radiolaria +are unicellular organisms, the whole fully developed organisation of which +falls under the category of a single cell, both morphologically and +physiologically. Since this view is based upon the composition of the +individual body out of two different morphological elements, nucleus and +protoplasm, it is at once justified in the case of the majority of +Radiolaria, in which the plasmatic body encloses only a single nucleus (the +so-called "Binnen-Blaeschen"); such is the case in all the SPUMELLARIA +monozoa, NASSELLARIA and PHAEODARIA. This aspect of the case might appear +doubtful in those Radiolaria in which the simple primary cell-nucleus +divides early into numerous small secondary nuclei, as is the case in the +SPUMELLARIA polyzoa and most ACANTHARIA. Strictly speaking, the +multinucleate central capsule should in such cases be regarded as a +syncytium; but since the individual unity of the unicellular organism is as +clearly defined in these precocious multinuclear Radiolaria as in the +ordinary serotinous forms, the former must be considered unicellular +Rhizopods just as are the latter. This mode of regarding {vi}the case is +the more necessary, inasmuch as the early division of the nucleus has no +further influence upon the organisation. Just as in many other classes of +the Protista there are monozootic (solitary) and polyzootic (social) forms, +so also in the Radiolaria there are in addition to the ordinary monozootic +or monobious forms certain families in which colonies or coenobia are +formed by the association of individuals; this distinction may be expressed +by the terms "Monocyttaria" and "Polycyttaria." + + The unicellular nature of the Radiolaria was first established by Richard + Hertwig in 1879 (L. N. 33),[1] and brought into conformity with our + present histiological knowledge and the new reform of the cell-theory. + Huxley, however, who was in 1851 the first to examine living Radiolaria + accurately, declared _Thalassicolla nucleata_ to be a unicellular + Protozoon, and the individual central capsules of _Sphaerozoum punctatum_ + to be cells, but, owing to the then condition of the cell-theory, he was + unable to give a conclusive demonstration of this view. Later, when + Johannes Mueller in 1858 and myself in 1862 recognised the peculiar + "yellow cells" which occur in large numbers in many Radiolaria as true + nucleated cells, it appeared impossible any longer to maintain the + unicellular nature of the Radiolaria; also the great complication which I + showed to exist in the structure of _Thalassicolla_ appeared to + contradict it. Only after Cienkowski (1871) and Brandt (1881) had shown + that the "yellow cells" do not belong to the Radiolarian organism, but + are symbiotic unicellular algae, was it possible to revive and + demonstrate anew the unicellular nature of the Radiolaria. + + +12. _Morphological Individuality._--From the morphological standpoint the +individuality of the unicellular elementary organism is obvious in the +ordinary solitary Radiolaria (Monobia), and is to be so regarded that the +whole body with all its constituent parts, and not merely the central +capsule, is to be regarded as _a cell_. Naturally the xanthellae or yellow +cells (ss 76, 90), which as independent algae live in symbiosis with many +Radiolaria, must be excluded. The unicellular organisation of the +Radiolaria is further to be distinguished from that of the other Protista, +inasmuch as an internal membrane (capsule-membrane) separates the central +(medullary) from the peripheral (cortical) portion. In the coenobia of the +social Radiolaria (or Polycyttaria), the morphological individuality +persists only as regards the medullary portions of the aggregated cells +(the individual central capsules), while the cortical portions fuse +completely to form a common extracapsulum. Hence in these SPUMELLARIA +polyzoa two different stages of morphological individuality must be +distinguished, the _Cell_ as a _Morphon of the first stage_, and the +_Coenobium_ as a _Morphon of the second stage_. + + +13. _Physiological Individuality._--From the physiological standpoint also +the individuality of the unicellular organism is immediately obvious in the +case of the ordinary solitary Radiolaria (Monobia); as in other Protista it +fulfils all the functions of life by itself alone. This physiological +individuality of the monobious Radiolarian cell is furthermore not +influenced by the xanthellae, which live as independent algae in symbiosis +with many Radiolaria; even though these often by the production of starch +assist in the {vii}nourishment of the Radiolaria, yet they are by no means +indispensable to them. On the other hand, the physiological individuality +offers more complicated relations in the social Radiolaria (Polycyttaria) +which live united in colonies or coenobia. Here the actual _Bion_ (or the +fully developed physiological individual) is not represented by the +individual cells, but by the whole multicellular coenobium, which in each +species has a definite form and size. In these coenobia, which are usually +spherical or cylindrical jelly-like masses, several millimeters in +diameter, numerous cells are so intimately united that only their medullary +portions (the central capsule with the endoplasm) remain independent; the +cortical portions (calymma and exoplasm) on the contrary uniting into a +common extracapsulum. This discharges, as a whole, the functions of +locomotion, sensation, and inception of nutriment, while the separate +central capsules act in the main only as reproductive organs (forming +spores) and partly also as the central organs of metastasis (digestion). +Each coenobium may also be regarded as a polycyttarium, _i.e._, a +"multicellular Radiolarian," whose numerous central capsules represent so +many sporangia or spore-capsules. + + On this head compare the section in my monograph of 1862 (L. N. 16), + entitled Die Organisation der Radiolarien-Colonien; _Polyzoen_ oder + _Polycyttarien?_ (pp. 116 to 126); and also R. Hertwig, Zur Histologie + der Radiolarien, 1876 (L. N. 26, p. 23). + + +14. _Monocyttaria_ and _Polycyttaria_.--In the majority of the Radiolaria +each unicellular organism passes its individual life in an isolated +condition (as a Monocyttarium). Only in a part of the SPUMELLARIA numerous +unicellular individuals are united into societies which are regarded as +coenobia or colonies (Polycyttaria). This is the case in three different +families belonging to the PERIPYLEA, in the Collozoida (without a skeleton, +Pl. 3), the Sphaerozoida (with a Beloid skeleton, Pl. 4), and the +Collosphaerida (with a Sphaeroid skeleton, Pls. 5-8). All three families of +Polycyttaria (or social Radiolaria), agree in their mode of forming +colonies, since the central capsules of the social individuals remain +separate and lie in a common jelly-like mass, which is formed by the fusion +of their extracapsulum. The chief part of the voluminous colonies, which +attain a diameter of several millimetres (sometimes more than 1 cm.), and +are generally spherical, ellipsoidal or cylindrical, consists therefore of +the jelly-like calymma, and this is penetrated by a sarcoplegma, to whose +meshes all the individual organisms contribute by means of the pseudopodia, +which radiate from their sarcomatrix. A further peculiarity in which the +social SPUMELLARIA differ from the solitary consists in the fact that the +former are precocious and the latter serotinous in the division of the +nucleus (s 64). Whilst in the solitary or monozootic SPUMELLARIA the middle +of the central capsule is occupied by the simple nucleus, and this divides +only at a late period (immediately before the formation of spores) into the +numerous spore nuclei, in the colonial or polyzootic SPUMELLARIA this +division takes place very early, and the middle of each central capsule is +usually occupied by an oil-globule. + + {viii}The colonial Radiolaria were described as early as the year 1834 by + Meyen, the first investigator of the class, under the name _Sphaerozoum_, + and, as _Palmellaria_, compared with the gelatinous colonies of the + Nostochineae. The first accurate observations upon their structure were, + however, made in 1851 by Huxley, who described examples of all three + families under the name _Thalassicolla punctata_. More extended, + however, were the investigations of Johannes Mueller, who in his + fundamental work (1858) divided the whole class Radiolaria into + _Solitaria_ and _Polyzoa_. The _Radiolaria solitaria_ he divided into + Thalassicolla, Polycystina and Acanthometra, the _Radiolaria polyzoa_ + into Sphaerozoa (without a shell) and Collosphaera (with a shell). The + most accurate delineation of the Polycyttaria was given by Hertwig in his + beautiful memoir, Zur Histologie der Radiolarien (1876). Quite recently, + however (1886), since the completion of my manuscript upon the Challenger + Radiolaria, a very complete Monograph of the Polycyttaria has appeared by + Karl Brandt, Die colonie-bildenden Radiolarien (Sphaerozoen) des Golfes + von Neapel und der angrenzenden Meeres-Abschnitte (276 pp., 8 pls., + Berlin). It contains in particular most valuable contributions to the + physiology and histology. + + +15. _The Central Capsule and Extracapsulum._--The special peculiarity of +the unicellular Radiolarian organism, by which it is clearly distinguished +from all other Rhizopoda (and indeed from most other Protista), is its +differentiation into two separate chief constituents, the central capsule +and extracapsulum, and the formation of a special membrane which separates +them. This, the capsule-membrane, is not to be compared with an ordinary +cell-membrane, as an external layer, but rather to be regarded as an +internal differentiated product. The extracapsulum or external (cortical) +portion of the body is in most Radiolaria more voluminous than the central +capsule or inner (medullary) portion. The exoplasm of the former (the +cortical or extracapsular protoplasm) is emphatically different from the +endoplasm of the latter (the medullary or intracapsular protoplasm). +Besides the most important vital processes are distributed by division of +labour so completely between them that they appear most distinctly +co-ordinated. The central capsule is on the one hand the general central +organ of the "cell-soul" for the discharge of its sensory and motor +functions (comparable to a ganglion-cell), on the other hand the special +organ of reproduction (sporangium). The extracapsulum, also, is not less +significant, since on the one hand its calymma acts as a protecting +envelope to the central capsule, as a support to the pseudopodia, and a +foundation for the skeleton or a matrix for the development of the shell, +and on the other hand its pseudopodia are of the utmost importance as +peripheral organs of movement and sensation as well as of nutrition and +respiration. The _central capsule_ and the _extracapsulum_ are therefore to +be regarded both morphologically and physiologically as the two +_characteristic co-ordinated principal parts_ of the unicellular +Radiolarian organism. + + In most of the more modern delineations of the Radiolaria the central + capsule is regarded as the "cell proper" and its membrane as the + "cell-wall." The following facts are opposed to the correctness of this + interpretation:--1. In most Radiolaria the exoplasm is clearly different + from {ix}the endoplasm, and the former is more voluminous than the + latter. 2. In all Radiolaria the division of labour is so carried out + between the central capsule and the extracapsulum, that the physiological + significance and independence of both principal parts of the cell is + almost equally great. 3. It is only in the ACANTHARIA that the formation + of the skeleton takes place within the central capsule; in all the other + three legions it is quite independent of it. + + +16. _The Malacoma and Skeleton._--Whilst the division of the unicellular +organism into central capsule and extracapsulum is undoubtedly the most +important character of the Radiolarian organism, the development of a +skeleton of peculiar and most varied form is of very striking significance. +This skeleton is _always a secondary product of the cell_, but is always +anatomically so independent, and so clearly marked off from the soft parts +or malacoma, that it seems advisable to regard both separately in a general +morphological survey. The skeleton stands in a different relation to each +of the two principal constituents of the malacoma. Only in the ACANTHARIA +is it centrogenous and developed from the central capsule outwards. In the +other three legions the skeleton never arises in the centre of the capsule; +in the NASSELLARIA and PHAEODARIA it is always extracapsular; in the +SPUMELLARIA it is also outside the central capsule originally, but +afterwards becomes often surrounded by it, and finally lies in most cases +partly within and partly without the central capsule. The chemical basis of +the skeleton in the ACANTHARIA is the curious acanthin (an organic +substance allied to chitin), in the PHAEODARIA a silicate of carbon, and in +the NASSELLARIA and SPUMELLARIA silica. + + +17. _Ground-Forms of the Radiolaria (Promorphology)._--The ground-forms of +the Radiolaria exhibit a greater variety than those of any other class in +the organic world, greater indeed than is to be found in all the remaining +groups together. For every conceivable ground-form which can be defined in +the system of promorphology is actually present in the Radiolaria; their +skeleton exhibits, as it were, in material existence, certain geometrical +ground-forms which are found in no other organisms. The cause of this +unexampled richness in different forms lies chiefly in the static relations +of the Radiolaria, which swim freely in the sea, partly also in the +peculiar plasticity of their protoplasm and the material of their +skeletons. + + Regarding the general system of ground-forms compare my Generelle + Morphologie (1866, Bd. i. pp. 375-552; Bd. iv., Allgemeine + Grundformenlehre). The ground-forms there proposed and systematically + defined have, however, found but little acceptance (chiefly, no doubt, + owing to the difficult and complicated nomenclature); but having now, + twenty years after their publication, anew carefully revised and + critically studied them, I can find no sufficient reason for abandoning + the principles there adopted. On the contrary the study of the Challenger + Radiolaria during the last ten years, with its incomparable wealth of + forms, has only confirmed the accuracy of my system of ground-forms. The + customary treatment of these in zoological and botanical handbooks (such + as those of Claus and Sachs) is quite insufficient. + + +{x}18. _The Principal Groups of Geometrical Ground-Forms._--The great +variety of the geometrical ground-forms which are actually realised in the +variously shaped bodies of the Radiolaria, renders it desirable to classify +these in as small a number as possible of principal groups and a larger +number of subdivisions. As extensive principal groups four at least must be +distinguished; the _Centrostigma_ or Sphaerotypic, the _Centraxonia_ or +Grammotypic, the _Centroplana_ or Zygotypic, and the _Acentrica_ or Atypic. +The natural centre of the body, about which all its parts are regularly +arranged, is in the first group a point (stigma), in the second a straight +line (principal axis), in the third a plane (sagittal plane), in the fourth +a centre is of course wanting. + + +19. _The Centrostigma or Sphaerotypic Ground-Forms._--The first group of +geometrical ground-forms, here distinguished as sphaerotypic or the +centrostigma, is undoubtedly the most important among the Radiolaria, +inasmuch as if these be considered monophyletic, it must be the original +one from which all the other ground-forms have been derived. The common +character of all these sphaerotypic ground-forms is that their natural +centre is a point (stigma); thus there is no single principal axis (or +protaxon) such as is characteristic of the two following groups. The +sphaerotypic ground-forms are subdivided into two important smaller groups, +the _spheres_ (Homaxonia) and the _endospherical polyhedra_ (Polyaxonia). +The spherical ground-forms, fully developed in the central capsule and +calymma of _Actissa_ and the #Sphaeroidea# as well as in many ACANTHARIA, +present no different axes; all possible axes passing through the centre of +the body are equal (Homaxonia). In the endospherical polyhedra, on the +contrary, numerous axes (three at least) may be distinguished, which are +precisely equal to each other and different from all the remaining axes +(Polyaxonia). If the extremities of these axes, or the poles, which are all +equidistant from the common centre, be united by straight lines, a +polyhedral figure is produced whose angles all lie in the surface of the +sphere. According as the poles of the axes are at equal, subequal, or at +different distances from each other, we may divide the endospherical +polyhedra into regular, subregular and irregular. (See Gener. Morphol., Bd. +i. pp. 404-416.) + + +20. _The Centraxonia or Grammotypic Ground-Forms._--The second principal +group of organic ground-forms, here called grammotypic or centraxonia, is +characterised by the fact that a straight line (gramma) or a single +principal axis (protaxon) forms the natural centre of the body. This +important and extensive group is divided into two subgroups, those with one +axis (Monaxonia) and those with crossed axes (Stauraxonia); in the latter +different secondary transverse or cross-axes may be distinguished, but not +in the former. In the Monaxonia, therefore, every transverse section of the +body perpendicular to the principal axis is a circle, in the Stauraxonia, +on the contrary, a polygon. The Monaxonia are further subdivided into two +groups, in one of which the two poles of the principal axis {xi}are equal +and similar (Isopolar), in the other of which they are different +(Allopolar); in the former the two halves of the body, which are separated +by the equatorial plane (or the largest transverse plane, perpendicular to +the principal axis), are equal, in the latter unequal. Among the isopolar +uniaxial ground-forms (Monaxonia isopola) may be mentioned the ellipsoidal, +spheroidal, lenticular, &c.; to the allopolar uniaxial forms (Monaxonia +allopola) belong the conical, hemispherical, ovoid, &c. In the same way the +pyramidal ground-forms with crossed axes are divisible into two groups, +according as the two poles of the principal axis are equal or not. The +ground-form of the former is the double pyramid, that of the latter the +single pyramid. Both the double and the single pyramids may again be +subdivided, each into two important lesser groups, the regular and the +amphithect. In the first division the equatorial plane of the double and +the basal plane of the single pyramid is a regular polygon (square, &c.), +whilst in the other division it is an elongated or amphithect polygon +(rhombus, &c.); the crossed axes are equal in the former, unequal in the +latter. (See Gener. Morphol., Bd. i. pp. 416-494.) + + +21. _The Centroplana or Zygotypic Ground-Forms._--The third principal group +of ground-forms includes those which are bilaterally symmetrical in the +ordinary sense, or zeugitic or zygotypic; the natural centre of their body +is a plane. These forms are the only ones in which the distinction between +right and left is possible, since their body is divided by the median plane +(planum sagittale) into two symmetrical halves (right and left). In all +these zeugites the position of every part is determined by three axes +perpendicular to each other, and of these three dimensive axes two are +allopolar, one is isopolar. The two unlike poles of the principal (or +longitudinal) axis are the oral and aboral, the two unlike poles of the +sagittal (or vertical) axis are the dorsal and ventral; the two similar +poles of the frontal (or transverse) axis, however, are the right and left. +This important group of zeugitic or bilateral forms may also be divided +into two clearly distinct lesser groups, the _Amphipleura_ and the +_Zygopleura_. In the Amphipleura (or bilaterally radial ground-forms) the +"radial two-sided" body is produced by modification of a regular pyramid +(as _Spatangus_ from _Echinus_), and hence is composed of several (not less +than three) antimeres. In the Zygopleura (or bilaterally symmetrical +ground-forms) on the other hand, the bodies consist of two antimeres (as in +all the higher animals, Vertebrata, Arthropoda, &c.). (See Gener. Morphol., +Bd. i. pp. 495-527.) + + +22. _The Acentrica or Atypic Ground-Forms._--Among the acentrica or +anaxonia are included all those ground-forms which are absolutely +irregular, and in which neither a definite centre nor constant axes can be +distinguished (_e.g._, most Sponges). These quite irregular ground-forms +are very rare among the Radiolaria, but nevertheless there may be referred +to them the amoeboid central capsule of some #Colloidea# (_Collodastrum_, +p. 27, Pl. 3, figs. 4, 5) among the SPUMELLARIA, the irregular shells of +many Collosphaerida {xii}(Pl. 8, fig. 2), and the absolutely irregular +shells of the Phorticida and Soreumida among the #Larcoidea#. (See Gener. +Morphol., Bd. i. p. 400.) + + +23. _The Subsidiary Groups of Geometrical Ground-Forms._--The four natural +principal groups of ground-forms, which have just been defined according to +the nature of the centre of their bodies, may be divided again into +numerous subsidiary groups, defined by the relations of the constant axes +and the two poles of each axis, as well as by the number of the axes and +the differentiation of the secondary with respect to the principal axis. +The most important of these subsidiary groups into which the principal ones +are immediately divided are the following:--(1) The _Centrostigma_ (or +sphaerotypic) are divided into spheres (Homaxonia) and endospherical +polyhedra (Polyaxonia). (2) The _Centraxonia_ (or grammotypic) into +uniaxial (Monaxonia) and those with crossed axes (Stauraxonia); among the +former of these may be distinguished the isopolar (phacotypic) and the +allopolar (conotypic); among the latter the double and single pyramids. (3) +The _Centroplana_ (or bilaterals) are divided into amphipleura (or +bilaterally radial) and zygopleura (or bilaterally symmetrical). (4) The +_Acentrica_ (or Anaxonia) or absolutely irregular ground-forms, present no +special subdivisions. + + For a complete system of the geometrical ground-forms and their relation + to promorphological classification, see Gener. Morphol., Bd. i. pp. + 555-558. + + +24. _The Spherical or Homaxon Ground-Form._--The spherical is the only +absolutely regular ground-form, since only in it are all axes which pass +through the centre equal; it is very often realised among the Radiolaria, +especially in the SPUMELLARIA and ACANTHARIA, where it furnishes the common +original ground-form, but it is often to be seen in the shells of many +PHAEODARIA (in most #Phaeosphaeria#); on the other hand, it is never found +among the NASSELLARIA. Geometrical spheres, in the strict sense of the +term, are only to be found among the SPUMELLARIA and ACANTHARIA, namely, in +the central capsule of many #Collodaria# (Pls. 1, 2) and all #Sphaeroidea# +(Pls. 11-30) as well as many Acanthometra and Acanthophracta (Pls. +128-138). Nevertheless, speaking generally, one includes those central +capsules and skeletons which have been distinguished here as endospherical +polyhedra. (On these ground-forms see Gener. Morphol., Bd. i. pp. 404-406.) + + +25. _The Endospherical Polyhedral Ground-Form._--The endospherical +polyhedron or polyaxon ground-form naturally follows the spherical or +homaxon. Under it are included all polyhedra whose angles fall in the +surface of a sphere; this ground-form is especially common among the +SPUMELLARIA, especially in the shells of #Sphaeroidea#, but is also found +among the ACANTHARIA (especially in the Astrolophida and #Sphaerophracta#), +as well as among the #Phaeosphaeria# (in most genera of the Orosphaerida, +Sagosphaerida, and Aulosphaerida). Strictly speaking, all those +lattice-shells which have {xiii}been incorrectly called "spherical" belong +to this category, for they are none of them true spheres in the geometrical +sense (like the central capsules of the #Sphaeroidea#), but rather +endospherical polyhedra, whose angles are indicated by the nodal points of +the lattice shell, or the radial spines which spring from them. These +endospherical polyhedra may be divided into three groups, the regular, +subregular, and irregular. Of _regular polyhedra_, properly so-called, it +may be shown geometrically that only five can exist, namely, the regular +tetrahedron, cube, octahedron, dodecahedron, and icosahedron. All these are +actually manifested among the Radiolaria, although but seldom. Much more +common are the _subregular endospherical polyhedra_, _e.g._, spherical +lattice-shells with regular hexagonal meshes of equal size; they are never +exactly equal nor perfectly regular, but the divergences are so +insignificant that they escape superficial observation (Pl. 20, figs. 3, 4; +Pl. 26, figs. 1-3). On the contrary in the _irregular endospherical +polyhedra_ the meshes of the lattice-sphere are more or less different in +size and often in form also (Pl. 28, figs. 4, 8; Pl. 30, figs. 4, 6). The +five truly regular polyhedra require separate notice on account of their +importance. (See Gener. Morphol., Bd. i. p. 406.) + + +26. _The Regular Icosahedral Ground-Form._--The ground-form whose +geometrical type is the regular icosahedron (bounded by twenty equilateral +triangles) is rarely exemplified, but it occurs among the PHAEODARIA in the +Circoporid genus _Circogonia_ (Pl. 117, fig. 1), and also in certain +Aulosphaerida, but, apparently, only as an accidental variation (_e.g._, +_Aulosphaera icosahedra_). Furthermore, this ground-form may also be +assumed to occur in those #Sphaeroidea# whose spherical lattice-shells bear +twelve equidistant radial spines (_e.g._, many species of _Acanthosphaera_, +_Heliosphaera_, and other Astrosphaerida); the basal points of these spines +indicate the twelve angles of the regular icosahedron. (See on this head +Gener. Morphol., Bd. i. p. 411.) + + +27. _The Regular Dodecahedral Ground-Form._--The ground-form whose +geometrical type is the regular dodecahedron (or pentagonal dodecahedron), +bounded by twelve equilateral and equiangular pentagons, is very rarely +found perfectly developed, as in _Circorrhegma dodecahedra_ (Pl. 117, fig. +2). This form is by no means so common among the Radiolaria as in the +pollen grains of plants (_e.g._, _Buchholzia maritima_, _Fumaria spicata_, +_Polygonum amphibium_, &c.). It can, however, be regarded as present in all +those #Sphaeroidea# whose spherical lattice-shells bear twenty equal and +equidistant radial spines (_e.g._, many species of _Acanthosphaera_, +_Heliosphaera_, and other Astrosphaerida); the basal points of these spines +mark out the twenty angles of the regular pentagonal dodecahedron. (See +Gener. Morphol., Bd. i. p. 412.) + + +28. _The Regular Octahedral Ground-Form._--The ground-form whose +geometrical type is the regular octahedron (bounded by eight equilateral +triangles), commonly appears among the SPUMELLARIA in the family +Cubosphaerida (p. 169, Pls. 21-25). In {xiv}these #Sphaeroidea# the typical +ground-form is usually indicated by six equal radial spines, which are +opposed to each other in pairs, and lie in three similar axes perpendicular +to each other; these are the three axes of the tesseral crystallographic +system; one of them is vertical, whilst the other two cross each other at +right angles in its centre. Occasionally, too, the spherical form of the +lattice-shell passes over into that of the regular octahedron (Pl. 22, +figs. 8, 10). The same form recurs in _Circoporus_ (Pl. 117, fig. 6) among +the PHAEODARIA. In the vegetable kingdom it is exhibited by the antheridia +of _Chara_. It is not found in the NASSELLARIA and ACANTHARIA. (See Gener. +Morphol., Bd. i. p. 412.) + + +29. _The Regular Cubic Ground-Form._--The ground-form whose geometrical +type is that of a die or cube, is actually presented in a very striking +manner by various Radiolaria. Among the SPUMELLARIA it occurs in certain +#Sphaeroidea#, _e.g._, in the Astrosphaerid genera _Centrocubus_ and +_Octodendron_ (Pl. 18, figs. 1-3); in these the central medullary shell is +a complete cube, bounded by six equal squares, from the eight angles of +which eight equal radial spines project. This form can also be regarded as +present in those #Sphaeroidea# whose spherical lattice-shell bears eight +equal and equidistant radial spines (many Astrosphaerida). Besides these +the cubic ground-form is to be seen in certain NASSELLARIA of the family +Tympanida, especially in _Lithocubus_ (Pl. 82, fig. 12; Pl. 94, fig. 13), +in many species of _Acrocubus_, _Microcubus_, &c.; the twelve bars of its +lattice-skeleton correspond often exactly to the edges of the cube. (See +Gener. Morphol., Bd. i. p. 413.) + + +30. _The Regular Tetrahedral Ground-Form._--The ground-form whose +geometrical type is the regular tetrahedron, bounded by four equilateral +triangles, occurs less frequently in the Radiolaria than the other four +regular polyhedra. Among the SPUMELLARIA it is found in the #Beloidea#, and +especially in those members of the Thalassosphaerida and Sphaerozoida whose +spicules bear four equal branches, diverging at equal angles from a common +centre. Precisely the same structure is seen also among the NASSELLARIA in +some #Plectoidea#, as in _Tetraplagia_ among the Plagonida, and +_Tetraplecta_ among the Plectanida. The skeleton of both these genera +consists of four equal rods, which radiate at equal angles from a common +centre, just as do the axes of the regular tetrahedron. The tetrahedral +form of these #Plectoidea# is the more important and interesting since on +the one hand it is related to the similar spicular form of the #Beloidea#, +and on the other perhaps furnishes the starting point from which _Cortina_ +among the NASSELLARIA may be derived (_Plagoniscus_, _Plectaniscus_). (See +Gener. Morphol., Bd. i. p. 415.) + + +31. _The Isopolar-Monaxon or Phacotypic Ground-Form._--The isopolar +uniaxial or phacotypic ground-form is characterised by the possession of a +vertical main axis with {xv}equal poles, whilst no transverse axes are +differentiated. All horizontal planes which cut the axis at right angles +are circles, and increase in size from the poles towards the equator. The +most important ground-forms of this group are the _phacoid_ (the lens or +oblate spheroid) and the _ellipsoid_ (or prolate spheroid). Phacoids (or +geometrical lenses with blunt margins) are very often presented by the +central capsules of the #Discoidea# and of many ACANTHARIA (Quadrilonchida +and Hexalaspida), but the lattice-shells of many SPUMELLARIA and ACANTHARIA +exhibit the same form, as also do a few PHAEODARIA (_e.g._, _Aulophacus_). +True geometrical ellipsoids are seen in the central capsules of many +#Prunoidea# among the SPUMELLARIA, and of many Amphilonchida and +Belonaspida among the ACANTHARIA. Furthermore, the lattice shells of many +species of these groups retain the same essential form, _e.g._, many +Ellipsida, Druppulida, and Spongurida (Pls. 13-17, and 39), as well as most +Belonaspida. (See Gener. Morphol., Bd. i. p. 422.) + + +32. _Allopolar-Monaxon or Conotypic Ground-Form._--The allopolar uniaxial +or conotypic ground-form is characterised by the possession of a vertical +main axis whose two poles are unlike, while no transverse axes are +differentiated. All horizontal planes cutting the main axis at right +angles are circles, and decrease more rapidly from the largest plane +towards the basal than towards the apical pole. The most important +ground-forms of this group are the ovoid, the cone, and the hemisphere. +They often occur (and in geometrical perfection) in the egg-shaped central +capsule and podoconus of the NASSELLARIA, as well as in the shells of +several groups of this legion, particularly in the Cyrtocalpida or +Monocyrtida eradiata (Pl. 51, figs. 10-13), and in many Stichocyrtida +eradiata; furthermore, they are also seen among the PHAEODARIA, _e.g._, +certain Challengerida (Pl. 99, figs. 19-22). (See Gener. Morphol., Bd. i. +p. 426.) + + +33. _The Regular Dipyramidal or Quadrilonchial Ground-Form._--The +ground-forms whose geometrical type is the regular double pyramid are +characterised by a vertical main axis which possesses equal poles, and +which is crossed at its centre by several equal transverse axes. The +horizontal equatorial plane is therefore a regular polygon, and divides the +body into two equal regular pyramids. The simplest and commonest form of +this group is the quadratic octahedron, the ground-form of the quadratic +crystallographic system; its equatorial plane is a square. This regular +dipyramidal ground-form occurs among the SPUMELLARIA in the shells of the +Staurosphaerida as well as of many #Discoidea#, in which several +equidistant radial spines or arms lie in the quadratic equatorial plane of +the body, and project from the margin of the lenticular disc (_e.g._, +_Sethostaurus_, Pl. 31; _Histiastrum_, Pl. 46, &c.). It is, however, among +the ACANTHARIA that the most important part is played by this ground-form +(and especially by the quadratic octahedron); it forms the basis of all +those #Acanthometra# and #Acanthophracta# in which twenty radial spines are +disposed according to the Muellerian Law, and in which {xvi}the four +equatorial spines are of equal dimensions (Icosacantha). (See Gener. +Morphol., Bd. i. p. 436-446.) + + +34. _The Amphithect Dipyramidal or Lentelliptical Ground-Forms._--The +ground-forms whose geometrical type is the lenticular or "triaxial" +ellipsoid, may also be designated amphithect double pyramids; they are +characterised by the possession of a vertical main axis which has similar +poles, and is crossed at its middle by two transverse axes, unequal but +isopolar. The horizontal equatorial plane of the body is therefore an +amphithect or elongated polygon (a rhombus in the simplest case possible), +and divides the whole body into two equal amphithect pyramids. The simplest +and commonest form of this group is the rhombic octahedron, which is also +the ground-form of the rhombic crystallographic system. It plays an +important part in those ACANTHARIA in which twenty radial spines are +disposed according to the Muellerian Law, but in which the two pairs of +equatorial spines are unequal (different geotomical and hydrotomical axes, +see p. 719); to this category belong the Amphilonchida (Pl. 132), +Belonaspida (Pl. 136), Hexalaspida (Pl. 139), and Diploconida (Pl. 140). A +form essentially identical obtains also among the SPUMELLARIA in the +majority of the #Larcoidea#, both in their triaxial lattice-shells, and in +their lentelliptical central capsules, which present geometrically accurate +triaxial ellipsoids, with three unequal isopolar axes at right angles to +each other. (See Gener. Morphol., Bd. i. p. 446-452.) + + +35. _The Regular Pyramidal Ground-Forms._--The ground-forms whose +geometrical type is the regular pyramid, and which are the most conspicuous +in the Medusae, Polyps, Corals, and regular Echinoderms (the Radiata of +earlier authors), are almost confined among the Radiolaria to the legion +NASSELLARIA; they occur, however, in the great majority of these, and +especially in those families which may be classed together as "#Cyrtoidea# +triradiata et multiradiata." Strictly speaking, however, almost all these +NASSELLARIA, at all events in their origin, are bilateral or dipleuric, +since the primary sagittal ring with its characteristic apophyses marks out +the sagittal median plane, and further, since the three feet of the basal +tripod are usually divided into an unpaired dorsal (pes caudalis) and two +paired ventral or lateral (pedes pectorales, dexter et sinister). On the +other hand, it is noteworthy, firstly, that among the primitive +#Plectoidea# there are perfectly regular radial forms, without any +indication of an original bilateral symmetry, and secondly, that similar +forms are also very common among the #Cyrtoidea#, probably as secondary +radial forms, developed from primitive bilateral ones. Similar cases also +occur in certain PHAEODARIA (_e.g._, the Medusettida and Tuscarorida, Pls. +100, 120), but they are entirely wanting among the ACANTHARIA and +SPUMELLARIA. The multiradial NASSELLARIA have arisen from the triradial by +the interpolation of three, six, nine, or more interradial and adradial +secondary apophyses between the three primary perradial ones. (See Gener. +Morphol., Bd. i. pp. 459-874.) + + +{xvii}36. _The Amphithect Pyramidal Ground-Forms._--The ground-forms whose +geometrical type is the amphithect pyramid, are distinguished from the +regular pyramidal forms, just discussed, chiefly by the form of the basal +plane, which is not a regular, but an amphithect or elongated polygon (in +the simplest case a rhombus). Hence in this case the allopolar main axis of +the body is crossed by two transverse axes which are isopolar and at right +angles, but are unequal; they cannot, however be distinguished as sagittal +and frontal axes as is the case in the zeugites. In the animal as well as +in the vegetable kingdom, an important part is played by this ground-form, +_e.g._, in the Ctenophora, where it is the rhombic pyramid. Among the +Radiolaria it is not common, though it is clearly expressed among the +NASSELLARIA in a number of #Stephoidea# (Stephanida and Tympanida), as well +as in many #Spyroidea# (_e.g._, the bipedal Zygospirida). It is very +accurately developed among the PHAEODARIA in the bivalved #Phaeoconchia# +(Pls. 121-128), where the two valves of the shell (dorsal and ventral) are +generally exactly alike, their median keels corresponding to the poles of +the sagittal axis. In the slit between the two valves lie the two secondary +openings (right and left) of the tripylean central capsule, corresponding +to the two poles of the frontal axis, and the main axis stands +perpendicularly to both these, its oral pole being indicated by the +astropyle, or principal aperture. (See Gener. Morphol., Bd. i. pp. +479-494.) + + +37. _The Amphipleural Ground-Forms._--By the term amphipleural ground-forms +are to be understood those usually defined as "bilaterally radial"; their +geometrical type is a half amphithect pyramid. The best known examples of +this form in the animal kingdom are the bilateral five-rayed Echinoderms +(_Spatangus_, _Clypeaster_), in the vegetable kingdom the symmetrical +five-rayed flowers (_Viola_, _Trifolium_). The three dimensive axes have +the same relation as in the zygopleura, to be next discussed, and which +also resemble them in being divisible only by one plane (the sagittal +median plane) into two equal halves. They differ, however, the amphipleural +body not being made up of two antimeres, but of at least three pairs of +antimeres (or three parameres), being therefore primitively radial. Hence +each of the symmetrical halves of the body contains more than one antimere. +Among the Radiolaria this form does not occur in the SPUMELLARIA, +ACANTHARIA, or PHAEODARIA; it is very common, however, among the +NASSELLARIA; many #Cyrtoidea# multiradiata and #Spyroidea# multiradiata +show this bilaterally radial ground-form, inasmuch as the body consists of +two symmetrical halves, and is also composed of numerous (usually three, +six, nine, or more) radial parameres. In the multiradiate Dicyrtida and +Tricyrtida the cephalis (the first joint) is usually bilateral, whilst the +thorax (the second joint) is multiradial. (See Gener. Morphol., Bd. i. pp. +495-506.) + + +38. _The Zygopleural Ground-Forms._--As zygopleural or dipleural +ground-forms, as opposed to the amphipleural, are classed those zeugites or +centroplana which are known {xviii}as "bilaterally symmetrical" in the +strictest sense of the term. This is the most important ground-form in the +animal kingdom, inasmuch as it obtains almost exclusively among the higher +animals (Vertebrata, Articulata, Mollusca, Vermes). The body consists of +only two antimeres, which correspond to the two symmetrical halves of the +body. Of the three dimensive axes two are allopolar, one isopolar; the oral +pole of the longitudinal main axis is different from the aboral; the dorsal +pole of the sagittal axis is different from the ventral; but the right pole +of the frontal axis is equal to the left. The right antimere is usually +precisely similar to the left (Eudipleura), more rarely it is slightly +dissimilar or asymmetrical (Dysdipleura). Among the Radiolaria this +ground-form is entirely wanting in the Porulosa or Holotrypasta +(SPUMELLARIA and ACANTHARIA), but on the contrary it is very common in the +Osculosa or Merotrypasta (NASSELLARIA and PHAEODARIA). In the NASSELLARIA +it is of special importance, for the typical _Cortina_ (the combination of +the primary sagittal ring with the basal tripod) exhibits the zygopleural +ground-form clearly sketched out; indeed it is usually clearly seen even in +the sagittal ring itself, for its ventral segment is more strongly curved +than the dorsal; its basal (or oral) pole is always different from the +apical (or aboral). Of the three feet of the basal tripod the unpaired +(caudal) one is directed dorsally and backwards, the two paired (pectoral) +ones ventrally and forwards. The majority of the NASSELLARIA may be +regarded as modifications of this original ground-form. Its relation to the +primitively triradiate tripod presents a still unsolved problem, and the +numerous relations of the zygopleural to the multiradiate ground-forms in +the NASSELLARIA are exceedingly complicated. The zygopleural ground-form is +less widely distributed among the PHAEODARIA, though it is very +characteristically developed in the rich and varied group of Challengerida +(Pl. 99). (See Gener. Morphol., Bd. i. pp. 507-527.) + + +39. _Synopsis of the Geometrical Ground-Forms:--_ + + Principal Groups of Ground-Forms. + Subsidiary Groups of Ground-Forms. + Geometrical Type. + Examples. + + I. CENTROSTIGMA. + The geometrical centre of the body is a point. Main axis wanting. + | + +-I. HOMAXONIA. + | All axes equal. + | | + | +-1. _Sphere_, + | + | Central capsule of the #Sphaeroidea# and of many ACANTHARIA. + | + +-II. POLYAXONIA. + Endospherical polyhedra. All the angles of the body lie on the surface + of a sphere. Numerous isopolar axes. + | + +-2. _Endospherical polyhedron_, + | + | Lattice-spheres of the #Sphaeroidea#, #Sphaerophracta#, and + | #Phaeosphaeria#. + | + +-3. _Icosahedron_, + | + | _Circogonia_. + | + +-4. _Dodecahedron_, + | + | _Circorrhegma_. + | + +-5. _Octahedron_, + | + | Cubosphaerida, _Circoporus_. + | + +-6. _Cube_, + | + | _Centrocubus_, _Lithocubus_, &c. + | + +-7. _Tetrahedron_, + + _Tetraplagia_, _Tetraplecta_, &c. + + II. CENTRAXONIA. {xix} + The geometrical centre of the body is a straight line (the vertical main + axis). + + Constant transverse axes (perpendicular to the main axis) are wanting in + the Monaxonia (which have circular transverse sections); on the contrary + they are differentiated in the Stauraxonia (which have polygonal + transverse sections). + | + +-III. MONAXONIA. + | Uniaxial ground-forms or centraxonia without transverse axes. The + | transverse planes (perpendicular to the main axis) are circles. + | | + | +-8. _Monaxonia isopola._ + | | (Spheroids and ellipsoids; both poles of the main axis similar.) + | | + | | Central capsule and lattice-shell of of many #Discoidea# (lenses) and + | | #Prunoidea# (ellipsoids), Belonaspida, &c. + | | + | +-9. _Monaxonia allopola._ + | (Cone, ovoid and hemisphere; the two poles of the axis dissimilar.) + | + | Central capsule and lattice-shell of many NASSELLARIA, especially + | the #Cyrtoidea# eradiata (Cyrtocalpida, &c.). + | + +-IV. STAURAXONIA. + Pyramidal ground-forms or centraxonia with transverse axes. The + transverse planes (perpendicular to the main axis) are either regular + or amphithect polygons. + | + +-10. _Dipyramides regulares._ + | (Quadratic octahedron, or quadrilonchial forms and regular double + | pyramids.) + | + | ACANTHARIA with twenty radial spines, the four equatorial being + | equal. Multiradial #Discoidea# and Staurosphaerida. + | + +-11. _Dipyramides amphithectae._ + | (Rhombic octahedron, lentellipsoid, and amphithect double pyramids.) + | + | ACANTHARIA with twenty radial spines, whose four equatorial spines + | are unequal but paired. Many #Larcoidea#. + | + +-12. _Pyramides regulares._ + | (Regular pyramids.) + | + | Many NASSELLARIA (triradial and multiradial). Medusettida and + | Tuscarorida. + | + +-13. _Pyramides amphithectae._ + (Rhombic pyramids.) + + #Phaeoconchia#. Bipedal #Spyroidea# and #Stephoidea#. + + III. CENTROPLANA. + The geometrical centre of the body is a plane (the sagittal plane). + Constant transverse axes (perpendicular to the main axis) are wanting in + the Monaxonia (which have circular transverse sections); on the contrary + they are differentiated in the Stauraxonia (which have polygonal + transverse sections). + | + +-V. BILATERALIA (or ZEUGITA). + Bilateral forms in the general sense, with right and left halves. + | + +-14. _Amphipleura_ + | (Bilaterally radial ground-form.) + | + | Many #Cyrtoidea# and #Spyroidea# multiradiata. + | + +-15. _Zygopleura._ + (Bilaterally symmetrical ground-form.) + + Most NASSELLARIA (primitively at least), many Challengerida. + + IV. ACENTRA. + There is no geometrical centre. + | + +-VI. ANAXONIA. + No definite axes can be determined. + | + +-16. _Irregularia._ + (Absolutely irregular ground-forms.) + + _Collodastrum_, _Collosphaera_, Phorticida, Soreumida. + + +40. _Mechanical Causes of the Geometrical Ground-Forms._--The great variety +of ground-forms exhibited by the Radiolaria is of special interest, since +in most instances their causes admit of recognition, and since they are so +intimately related to each other that even in the remaining cases the +assumption that they have arisen by purely mechanical _causae efficientes_ +seems justified. In this respect the first rank is taken by statical +conditions, especially the indifferent or stable equilibrium of the whole +organism, which floats freely in the water. With regard to these +fundamental statical relations, three principal groups of ground-forms may +be distinguished, pantostatic, polystatic, and monostatic. + + +41. _Pantostatic Ground-Forms._--By pantostatic or indifferently stable +ground-forms are meant those in which the centre of gravity coincides with +the centre of the body, so that they are in equilibrium in any given +position. Strictly speaking, the only form which possesses perfectly +indifferent equilibrium is the sphere, that being the only truly homaxon +and perfectly regular form. Nevertheless, in a somewhat wider sense many +Polyaxonia, especially the endospherical polyhedra with very numerous +sides, may be {xx}included in this category. Such indifferently stable +bodies are found among the SPUMELLARIA in many #Collodaria# and +#Sphaeroidea#, as well as in the Astrolophida among the ACANTHARIA. On the +contrary they are entirely wanting among the NASSELLARIA and PHAEODARIA, +since their central capsule constantly presents a main axis with a +differentiated basal pole, and determines the position of stable +equilibrium. + + +42. _Polystatic Ground-Forms._--Those ground forms are defined as +polystatic or multistable in which the body is in equilibrium in several +different positions (though not in an infinite number). The number of these +positions is usually twice as many as that of the constant equal isopolar +axes exhibited by the form. Hence the regular polyhedra have as many +positions of equilibrium as they have angles or sides, the icosahedron +twenty, dodecahedron twelve, octahedron eight, cube six, tetrahedron four. +The isopolar monaxon ground-forms (lens, ellipsoid, cylinder) and the +diplopyramidal ground forms (quadrilonchial and lentelliptical) have two +positions of stable equilibrium, since the two poles of the vertical axis +are equal and similar and the body is divided into equal halves by the +equatorial plane. This is the case in many SPUMELLARIA (especially +#Discoidea#, #Prunoidea#, and #Larcoidea#), as well as in the great +majority of ACANTHARIA. Perhaps the same holds good also in certain +NASSELLARIA (_e.g._, isopolar Tympanida) and PHAEODARIA (_e.g._, isopolar +#Phaeosphaeria#), though here unistable equilibrium appears to be +necessitated by the constant main axis of the central capsule and the +differentiated basal pole of the main axis. + + +43. _Monostatic Ground-Forms._--Those ground-forms are classed as +monostatic or unistable in which the body is in equilibrium only in one +position, since the centre of gravity of the body lies in a constant +vertical axis below its centre. This fixed position is only rarely and +exceptionally found among the SPUMELLARIA (_e.g._, in _Xiphostylus_, +_Sphaerostylus_, _Lithomespilus_, _Lithapium_) and among the ACANTHARIA +(_e.g._, in _Zygostaurus_ and _Amphibelone_). On the contrary it is quite +usual among the NASSELLARIA and PHAEODARIA (with but few exceptions); for +here a vertical main axis, with a differentiated basal pole, is determined +even by the formation of the central capsule, and usually also by the +corresponding structure of the skeleton. Among the NASSELLARIA this basal +pole, with the porochora of the central capsule, appears always to be the +lower; as also in most #Phaeogromia# among the PHAEODARIA. In the peculiar +bivalved #Phaeoconchia#, on the other hand, the basal pole with the +cannopyle is directed upwards; as also in the Challengerida and +Tuscarorida. The #Phaeosphaeria# and #Phaeocystina# are probably to a large +extent polystatic. In general unistable equilibrium may be assumed in the +following categories of ground-forms:--(1) Allopolar monaxon (conical and +ovoid); (2) pyramidal (regular and amphithect); (3) Centroplana +(amphipleura and zygopleura); (4) Anaxonia. + + +{xxi}44. _Principal Axes._--From the foregoing consideration of the +statical conditions and their direct causal connection with the geometrical +ground-forms of the Radiolaria, the great mechanical significance of the +differentiation of definite axes in these unicellular free-swimming +organisms will be manifest. The most important of these is the primary main +axis (axis principalis, or protaxon), which in all cases has a vertical +direction. It is wanting in the Centrostigma (spheres and endospherical +polyhedra), and in the Anaxonia (acentra). It is isopolar in the phacotypic +forms (Monaxonia isopola), and in the double pyramids (Stauraxonia +isopola). It is allopolar in all monastatic ground-forms, in the conotypic +forms (Monaxonia allopola), pyramids (Stauraxonia allopola), and the +Centroplana (or bilateral forms). + + +45. _Secondary or Transverse Axes._--In contrast to the vertical main axis +all the other constant axes differentiated in the body may be called +"secondary axes," or "transverse axes," since they cross the former at +definite points. All ground-forms whose vertical axis is crossed by a fixed +number of such axes at definite angles may be called "Stauraxonia." They +are divided into two groups, double pyramids and single pyramids; in the +former the two poles of the main axis (or the two halves of the body +separated by the equatorial plane) are similar (Stauraxonia homopola), in +the latter dissimilar (Stauraxonia heteropola). If all the secondary axes +be equal, the stauraxon ground-form is regularly radial. If some of them be +unequal they are arranged in certain relations towards two primary +transverse axes, perpendicular to each other, to which all the other +secondary axes are subsidiary; the ground-forms are then either amphithect +or bilateral. The two primary transverse axes, which may also be designated +"ideal transverse axes" (euthyni), divide the vertical main axis in its +centre; one of them is the sagittal, the other the frontal. These three +dimensive axes give the factors which accurately determine the ground-form +and the dimensions in most Radiolaria; the vertical main axis determines +the length (principal axis); one horizontal transverse axis determines the +thickness (sagittal axis), and the other the breadth (frontal axis). Those +ground-forms in which the transverse axes are isopolar are termed +"amphithect," and those in which the one (frontal or lateral) is isopolar +and the other (sagittal or dorso-ventral) is allopolar, are termed +"bilateral," or better "zeugitic." + + +46. _Primary and Secondary Ground-Forms._--The geometrical sphere must be +regarded as the original ground-form of the Radiolaria; it being understood +that its monophyletic derivation from a single stem-form, _Actissa_, is +correct. The simplest forms of _Actissa_ (_Procyttarium_, Pl. 1, fig. 1) +are in fact geometrically _perfect spheres_; indeed even the individual +parts which compose their unicellular bodies (nucleolus, nucleus, central +capsule and calymma) are concentric spheres. But in addition the central +capsules of most other SPUMELLARIA, especially the #Sphaeroidea#, as well +as of many ACANTHARIA {xxii}are true spheres. Furthermore the simple or +concentrically composed lattice-spheres of #Sphaeroidea#, #Sphaerophracta#, +and #Phaeosphaeria# may be regarded as spheres, although strictly speaking +they are endospherical polyhedra. From the primary spherical form of the +Radiolaria all other secondary forms may be derived in the following +order:--1. By the development of a main axis the Monaxonia arise. 2. By the +development of transverse axes the Stauraxonia arise. 3. In both groups +(Monaxonia and Stauraxonia) the two poles (or upper and lower halves of the +body) are at first similar (Isopola). 4. By differentiation in the two +poles or halves of the body (distinction between the basal pole and the +apical) the forms with different poles (Allopola) arise. 5. The transverse +axes of the Stauraxonia are at first equal (regular pyramids and double +pyramids). 6. By differentiation in the transverse axes (distinction +between the sagittal and the frontal axis) the amphithect pyramids and +double pyramids arise. 7. From the amphithect pyramids the Amphipleura +arise by differentiation of both poles of the sagittal axis. 8. The +zygopleural ground-form appears last, as the simplest form of the +Amphipleura. + + +47. _The Ground-Forms of the Spumellaria._--The SPUMELLARIA, being the +oldest and most primitive Radiolaria, have for the most part either +indifferent or multistable equilibrium; _e.g._, all #Colloidea# and +#Beloidea# which have a spherical central capsule, and also most +#Sphaeroidea#. Among these primitive Centrostigma true spheres and +endospherical polyhedra are represented in the utmost variety, and the +regular polyhedra in particular. By the development of a vertical main axis +these Centrostigma have also given rise to very numerous Centraxonia, which +are usually isopolar, very rarely allopolar. Sometimes they are Monaxonia +(circular in transverse section), sometimes Stauraxonia (polygonal in +transverse section). The vertical main axis is longer in the #Prunoidea#, +shorter in the #Discoidea# than any of the other axes. The #Larcoidea# are +distinguished by their lentelliptical or triaxial ellipsoid form; the three +different but isopolar axes corresponding with those of the rhombic +octahedron; but even among the #Sphaeroidea#, #Prunoidea#, and #Discoidea#, +this form is sometimes produced by the differentiation of two different +transverse axes at right angles to each other. Whilst these ground-forms +(Centraxonia and Centrostigma) occur in the utmost variety among the +SPUMELLARIA, the centroplanar (or true bilateral) ground-form is entirely +wanting. + + +48. _The Ground-Forms of Acantharia._--In the small family Astrolophida, +which contains the most archaic forms of the legion (_Actinelius_, +_Astrolophus_), the ACANTHARIA show a direct relation to the most primitive +SPUMELLARIA (_Actissa_), and like these have indifferent equilibrium; their +central capsule is a sphere, their calymma an endospherical polyhedron, +whose angles are indicated by the distal ends of the numerous {xxiii}equal +radial spines. In the great majority of ACANTHARIA, however (all +#Acanthonida# and #Acanthophracta#), twenty radial spines are present, +regularly distributed, according to Mueller's icosacanthan law, in five +parallel circles, each containing four crossed spines (p. 717). Usually the +twenty spines are equal, and the ground-form is the quadratic octahedron, +or a regular double pyramid with sixteen sides. But in some groups (the +Amphilonchida and Prunophracta) two opposite equatorial spines are much +more strongly developed than the other eighteen, and therefore the +hydrotomical axis in the equatorial plane is larger than the geotomical +axis (p. 719); the isopolar stauraxonian form passes over into the +allopolar, and the ground-form becomes the rhombic octahedron or the +amphithect double pyramid (compare ss 33 and 34, and p. 720). The +centroplanar ground-form is entirely wanting in the ACANTHARIA. + + +49. _The Ground-Forms of the Nassellaria._--The NASSELLARIA all possess +monostatic ground-forms, inasmuch as by the very structure of their +monopylean central capsule a vertical main axis is necessitated, whose +basal pole occupies the porochora. The same arrangement is also for the +most part clearly recognisable in the corresponding structure of the +skeleton, which is generally either centraxon or centroplanar. Among their +manifold skeletal forms different larger groups of ground-forms may be +recognised according as the vertical allopolar main axis is crossed by +differentiated transverse axes or not (Stauraxonia or Monaxonia); the +former are either triradial or multiradial. The triradial, with three +lateral or terminal radial apophyses, constitute the greater part of the +NASSELLARIA, and have probably been derived originally from the triradial +#Plectoidea# (_Triplagia_, _Triplecta_); a more careful examination, +however (especially with reference to the structure of the cortinar +septum), reveals the fact that the ground-form is not strictly regularly +pyramidal (with three equal radii), but amphipleural (with two paired +ventral and one unpaired dorsal radius), and that it usually passes over +into a distinctly zygopleural form. The same holds true of the multiradial +NASSELLARIA, where for the most part three interradial or six adradial +(sometimes more) apophyses are intercalated between the three primary +perradial ones; sometimes here also the ground-form is a quite regular +hexagonal or nonagonal pyramid, but usually it is more or less amphithect +or amphipleural. Among the eradial NASSELLARIA, which have no radial +apophyses, the ground-form is sometimes allopolar monaxon (conical, ovoid, +hemispherical, &c.), sometimes amphithect pyramidal (even in the simplest +Stephanida, _Archicircus_, &c.), or sometimes distinctly zygopleural or +bilateral (many #Plectellaria#). + + +50. _The Ground-Forms of the Phaeodaria._--The PHAEODARIA agree with the +NASSELLARIA in the possession of a primitively centraxon ground-form, and +like them are monostatic, since a vertical main axis whose basal pole +passes through the astropyle is present, owing to the characteristic +structure of their cannopylean central capsule. In {xxiv}the great majority +of PHAEODARIA the spheroidal central capsule also possesses a pair of +parapylae near the opposite apical pole of the main axis (Tripylea), and +these determine (as the right and left secondary openings) an isopolar +frontal axis. Hence, strictly speaking, in most PHAEODARIA the central +capsule has the geometrical ground-form of the amphithect pyramid (as in +the Ctenophora), with an allopolar vertical main axis, and two unequal, but +isopolar, horizontal transverse axes. In many PHAEODARIA the skeleton also +has this amphithect pyramidal ground-form, _e.g._, the bivalved +#Phaeoconchia# and part of the #Phaeogromia#. On the contrary, in the rest +of the PHAEODARIA the skeleton exhibits very various geometrical +ground-forms, independent of that of the central capsule. In the +#Phaeosphaeria# it forms preferably spheres or endospherical polyhedra, as +also in the Castanellida and Circoporida among the #Phaeogromia#; among the +Circoporida there are also seen with remarkable distinctness the regular +polyhedra (especially the dodecahedron and icosahedron). Isopolar monaxonia +are found among the Aulosphaerida (_Aulatractus_) and Orosphaerida; +allopolar monaxonia among the Challengerida (_Lithogromia_). The +Medusettida and Tuscarorida show various forms of regular pyramids +(allopolar Stauraxonia); and finally, the Challengerida are for the most +part centroplanar or bilateral. Thus the PHAEODARIA present a great wealth +of different geometrical ground-forms in the development of their skeleton, +not in that of their central capsule. + + + +CHAPTER II.--THE CENTRAL CAPSULE. + + +51. _Components of the Central Capsule._--In all Radiolaria without +exception, at some period of life or other, the central portion of the soft +body is separated from the peripheral portion by an independent, +anatomically recognisable membrane; this membrane with all its contents is +designated the central capsule, and is the peculiar central organ of the +unicellular body, which distinguishes the Radiolaria most clearly from the +other Rhizopoda. In the great majority of the Radiolaria the volume of the +central capsule is less than that of the surrounding peripheral soft body +which we place in opposition to it as "extracapsulum." The +"capsule-membrane," which separates these two constituents, arises very +early in most Radiolaria, and persists throughout their whole life. In some +species, however, the membrane only appears later, immediately before the +formation of the spores, and hence is absent for a considerable period. +Regarded as a whole, then, the capsule consists of the following +parts:--(1) the capsule-membrane; (2) the enclosed endoplasm, or +intracapsular protoplasm; (3) the nucleus. But in addition, many other +non-essential structures may be enclosed in the central capsule, especially +hyaline spheres (vacuoles), fatty spheres, pigment granules, crystals, &c. + + The central capsule was first described in my Monograph in 1862 (pp. + 69-82) as the most characteristic component of the Radiolarian organism, + and distinguished from the whole extracapsular {xxv}soft body. The fact + that it has recently been reported as absent by various authors is due to + their having observed young or unripe specimens, before the formation of + the spores. In some species of #Polycyttaria# and ACANTHARIA the membrane + persists only a very short time. + + +52. _The Primary Form of the Central Capsule._--The form of the central +capsule is originally a geometrical sphere; and if in accordance with our +monophyletic hypothesis all Radiolaria are to be derived from one common +stem-form (_Actissa_, see p. 12), then the central capsule of this common +stem-form must be regarded as perfectly spherical (_Procyttarium_, p. 13, +Pl. 1, fig. 1). Since, further, the enclosed nucleus and the surrounding +calymma of this primitive archaic form must also be spheres, and since the +nucleus lies in the centre of the body, and the protoplasm is evenly +distributed between it and the membrane, it follows that no axes or +excentrically differentiated parts are to be distinguished in this most +primitive Radiolarian. Rather in the primary central capsule all parts are +concentrically and evenly arranged round its centre. This primary spherical +form becomes modified in most Radiolaria into various secondary +ground-forms, which are correlated partly with the structure of the capsule +itself, and partly also with the development of openings in its membrane. +In general the ground-form of the central capsule is polyaxon in the +Porulosa (SPUMELLARIA and ACANTHARIA); but in the Osculosa centraxon forms +are more frequently observed; in the NASSELLARIA the ovoid (allopolar +monaxon) form is predominant, and in the PHAEODARIA the rhomboid or +amphithect pyramid. In these latter, the astropyle indicates the basal pole +of the vertical main axis, whilst the two parapylae (right and left) mark +the poles of the frontal transverse axis. In the NASSELLARIA the centre of +the porochora corresponds with the basal pole of the main axis, whilst no +transverse axes are originally present. + + +53. _The Secondary Forms of the Central Capsule._--The original purely +spherical form of the central capsule persists only in the minority of the +Radiolaria, namely, the greater part of the SPUMELLARIA and ACANTHARIA; it +passes over into various other secondary forms in the majority of the +class, in the whole of the NASSELLARIA and PHAEODARIA, and in a +considerable portion of the SPUMELLARIA and ACANTHARIA. These secondary or +derived forms may be divided into two quite distinct groups, which may be +designated endometamorphic and exometamorphic; in the former the cause of +the divergence of the secondary form from the sphere lies in the internal +structure of the central capsule; in the latter it lies in the external +influence exerted by the growth of the skeleton. Obviously the former +series of modifications is more significant than the latter. + + +54. _The Endometamorphic Forms of the Central Capsule._--The secondary +forms of the central capsule, which are due to internal causes connected +with its growth, are as follows:-- + + {xxvi}A. _The Ellipsoidal Central Capsule_, with one axis elongated, so + that it becomes the vertical main axis of the body. + + _a._ Among the SPUMELLARIA, _Actiprunum_ (p. 14), _Colloprunum_ (p. 25, + Pl. 3, fig. 9), most #Prunoidea# (p. 288). + + _b._ Among the ACANTHARIA, many Amphilonchida (p. 782, Pl. 132, figs. + 2, 6), and Belonaspida (p. 861). + + _c._ Among the NASSELLARIA, many #Plectoidea# (p. 905, Pl. 91, figs. 5, + 9), #Stephoidea# (p. 937, Pl. 81, fig. 16), Monocyrtida (Pl. 51, fig. + 3), &c. + + B. _The Cylindrical Central Capsule_, with considerable elongation of the + vertical main axis, which is several times as long as the horizontal + transverse axis. + + _a._ Amongst the SPUMELLARIA, _Collophidium_ (p. 26, Pl. 3, figs. 1-3) + and many #Prunoidea# (_Spongurus_, &c.). + + _b._ Among the ACANTHARIA, some Amphilonchida. + + C. _The Discoidal, Spheroidal, or Lenticular Central Capsule_, with one + axis shorter than the others, which becomes the vertical main axis. + + _a._ Among the SPUMELLARIA, _Actidiscus_ (p. 15), _Collodiscus_ (p. + 27), and the large group #Discoidea# (p. 408). + + _b._ Among the ACANTHARIA, many Quadrilonchida (p. 768, Pl. 131), and + most Hexalaspida (p. 874). + + _c._ Among the NASSELLARIA, certain #Stephoidea# and #Cyrtoidea#. + + _d._ Among the great legion PHAEODARIA the spheroidal central capsule + is almost always more or less flattened in the direction of the main + axis (p. 1525, Pls. 101-128). + + D. _The Lentelliptical Central Capsule_ (or triaxial ellipsoid), with + three unequal but isopolar axes at right angles to each other, the + sections in all three dimensions of space being ellipses. + + _a._ Among the SPUMELLARIA, _Actilarcus_ and the large group + #Larcoidea# (p. 604). + + _b._ Among the ACANTHARIA, certain Amphilonchida and Belonaspida. + + E. _The Polymorphic, Amoeboid or Irregular Central Capsule._ + + _a._ Among the SPUMELLARIA, _Collodastrum_ (p. 28, Pl. 3, figs. 4, 5), + and some #Larcoidea#. + + +55. _The Exometamorphic Forms of the Central Capsule._--The secondary forms +of the central capsule, which are brought about by external causes, chiefly +dependent on the formation of the skeleton, are very various and in many +cases devoid of special interest; in other instances, on the contrary, they +are of great importance, because of the clear relation of cause and effect +which can be traced between the development of the skeleton and of the +capsule. The most important phenomena to be recorded in this connection are +as follows:-- + + {xxvii}I. SPUMELLARIA.--(A) In many of the #Sphaeroidea#, the central + capsule of which is originally enclosed by a simple lattice-sphere, it + puts out protrusions through the meshes of the shell, thus forming + club-shaped processes, corresponding in number with the meshes of the + lattice (Pl. 11, figs. 1, 5; Pl. 20, fig. 1_a_; Pl. 27, fig. 3, &c.). The + whole surface of the spherical capsule may thus be covered with numerous + independent radial clubs of equal size, but usually they unite again + outside the shell to form a simple sphere with smooth surface. (B) In + many #Prunoidea# whose originally ellipsoidal body has become cylindrical + by the marked prolongation of the main axis, the central capsule is + divided by a series of constrictions into segments, which correspond with + the annular constrictions of the skeleton (Pls. 39, 40). (C) In most + #Discoidea# whose lentiform or discoidal shell develops radial arms at + its margin, the central capsule sends out processes into these arms, and + adapts itself to the stellate form of the skeleton (p. 409, Pl. 43, fig. + 15; Pl. 47, &c.) (D) In many #Larcoidea# whose growth is originally + lentelliptical, but later spiral or irregular, the central capsule + follows the mode of growth and develops irregular protuberances. + + + II. ACANTHARIA.--Whilst the central capsule of most ACANTHARIA retains + its primitive spherical form, in a minority of the group it passes over + into various secondary forms, which are directly determined by the growth + of the skeleton; especially common are lappet or club-shaped prominences + which follow the larger radial spines. Hence the central capsule may + assume the form of a violin, with two lobes corresponding to the two + poles of the elongated main axis, as in many Amphilonchida (p. 782, Pl. + 132, fig. 10), and the Diploconida (p. 884, Pl. 140). On the other hand + the central capsule becomes cruciform, with four lobes disposed at right + angles, as in Lithoptera and other Quadrilonchida (p. 768, Pl. 131, fig. + 10, &c.). + + + III. NASSELLARIA.--The primitive ellipsoid or ovoid form of the central + capsule persists only in a few NASSELLARIA, such as the simplest and most + archaic forms, the Nassellida, many #Plectoidea#, #Stephoidea#, + Monocyrtida, &c. In the great majority of the NASSELLARIA, on the + contrary, the ellipsoid or ovoid form passes over into a secondary form + which is usually characterised by the presence of lobes, and is obviously + dependent upon the previous development of the skeleton. In many + #Stephoidea# and #Spyroidea# (probably the majority), a bilobed central + capsule is formed (with symmetrically equal right and left lobes), since + the primary vertical sagittal ring interferes with the growth in the + median plane (Pl. 90, figs. 7-10). In other {xxviii}#Spyroidea#, on the + contrary, and the majority of the #Cyrtoidea#, the central capsule forms + at its basis rounded lobes, which protrude and hang down from the meshes + of the cortinar plate; and since this latter has usually three or four + large pores, the capsule similarly develops three or four processes (Pl. + 53, fig. 19; Pl. 55, figs. 4-11; Pl. 59, figs. 4-13; Pl. 60, figs. 3-7; + Pl. 65, fig. 1). + + +56. _The Membrane of the Central Capsule._--The capsule-membrane or +envelope of the central capsule is both morphologically and physiologically +one of the most important parts of the Radiolarian body, for it separates +its two main constituents, the capsule with its nucleus and endoplasm and +the extracapsulum with the calymma and exoplasm. The capsule-membrane is +invariably present at some time or other during the life of the organism, +even though in a few species it may persist only for a short time. It is +characterised in general by its power of resistance to chemical and +physical reagents, and appears to be related to the elastic tissues or +perhaps even more to the chitinous substances. Its thickness is usually +less than 0.0001, though in certain groups it ranges between 0.001 and +0.002, and in many of the larger Radiolaria (such as Collida and +PHAEODARIA) it may attain a thickness of 0.003 to 0.006 or more. In the +three legions SPUMELLARIA, ACANTHARIA, and NASSELLARIA the capsule-membrane +is single, while in the PHAEODARIA it is always double, being composed of a +firm outer and a delicate inner membrane, which are in contact at only few +points. Usually it is quite structureless, except for its apertures; the +thicker membrane showing occasionally a fine concentric lamination. In +certain large #Colloidea# (_e.g._, _Thalassicolla_, Pl. 1, fig. 5_b_) the +membrane is covered on the inner surface by a network of polygonal ridges, +and in some large PHAEODARIA with remarkable small curved rods (Pl. 114, +fig. 13). In all Radiolaria the membrane is perforated by definite openings +or pores, through which the intracapsular and extracapsular protoplasm are +in direct communication. These openings (or "pylae") show very +characteristic and constant differences in the four legions, which have +given rise to the names--PERIPYLEA, ACTIPYLEA, MONOPYLEA, CANNOPYLEA. + + The capsule-membrane was first indicated as the most important and + absolutely constant component of all Radiolaria, and as the differential + character of the class, in my Monograph (1862, pp. 69-71). The careful + investigations of R. Hertwig have confirmed this view and at the same + time have yielded the most important conclusions regarding the nature and + systematic significance of the openings in the capsule (_op. cit._, 1879, + pp. 105-107). On the contrary, Karl Brandt has recently propounded the + theory that the capsule-membrane is by no means a constant part of the + Radiolarian organism, but is lacking in certain species of _Collozoum_ + and _Sphaerozoum_ (1881, p. 392). This contradiction is explained by the + fact that in some #Collodaria# and #Acanthometra# the formation of the + central capsule takes place much later than in the other Radiolaria, in + some {xxix}species indeed only just prior to the development of the swarm + spores. I have recognised the presence of it in all species which I have + investigated (more than a thousand), and even in those in which Brandt + denies its existence. It is often very delicate and may easily be + overlooked, especially when the contents of the capsule are colourless, + but in all cases by the prudent application of staining fluids and other + reagents its presence may be demonstrated. Even in those cases in which + the contour of the capsule was not visible, and its contents appeared to + pass without definite boundary into the matrix of the extracapsulum, it + was possible by the use of appropriate stains or reagents, which would + not penetrate the capsule, or of those solvents which were capable of + dissolving its contents and of causing it to swell up like a distended + bladder, to recognise the existence of the membrane. Those Radiolaria in + which it is truly absent are young animals of species in which the + membrane is only formed immediately before sporification, and persists + but for a short time (_e.g._, species of _Collozoum_, _Sphaerozoum_, + _Acanthometra_, _Acanthochiasma_, &c.). + + +57. _The Capsule-Openings of the Peripylea (or Spumellaria)._--The +capsule-membrane of the PERIPYLEA is generally perforated by extremely fine +and numerous pores, which are distributed at equal distances over the whole +surface, and are precisely alike in all parts of the capsule. Hence the +SPUMELLARIA may be called "Holotrypasta" or "Porulosa"; they agree with the +ACTIPYLEA in being devoid of an osculum or operculum; they are +distinguished from the latter group mainly in that their pores are equally +distributed over the whole surface of the capsule, whilst in the ACTIPYLEA +the pores are disposed in definite groups or lines, separated by large +imporous areas. + + The central capsule of the SPUMELLARIA, with its innumerable fine and + evenly distributed pores, must be regarded as the primitive arrangement, + from which the different central capsules of the three other legions have + been developed. The central capsule of the ACTIPYLEA has been derived + from that of the PERIPYLEA by reduction in the number of the pores and + their distribution in definite, regularly disposed areas in the membrane. + The central capsule of the Osculosa is characterised by the formation of + a special main-aperture (osculum) at the basal pole, which is closed in + the MONOPYLEA by the porochora, and in the CANNOPYLEA by the astropyle; + the remaining pores, with the exception of the accessory openings of many + CANNOPYLEA, remain undeveloped in both these legions. In the same way + Hertwig regards the central capsule of the PERIPYLEA as the primitive + form (1879, L. N. 33, p. 107). + + +58. _The Capsule-Openings of the Actipylea (or Acantharia)._--The +capsule-membrane of the ACTIPYLEA is perforated by very numerous fine +pores, which are regularly distributed over the surface of the central +capsule, and separated by imporous intervals. Hence the ACANTHARIA belong +to the "Holotrypasta" or "Porulosa"; they have neither osculum nor +operculum, and agree in this particular with the PERIPYLEA; but they are +separated from these latter chiefly by the fact that their pores are much +less numerous, and marked off into regularly arranged groups or lines by +imporous intervals. In the PERIPYLEA, on the contrary, the pores are much +more numerous and are evenly distributed over the whole surface of the +capsule. + + {xxx}The central capsule of the ACANTHARIA has hitherto been for the most + part confounded with that of the SPUMELLARIA, and no clear distinction + has been drawn in this respect between the two legions of the Porulosa. + Hertwig, who in 1879 first discovered the remarkably different structure + of the Osculosa (NASSELLARIA and PHAEODARIA), recognised no distinction + between the structure of the capsules in the PERIPYLEA and ACTIPYLEA (his + Acanthometrea), and supposed that in both these legions "very fine pores + were evenly distributed in large numbers over the capsule-membrane" + (_loc. cit._, p. 106). I have, however, during the last few years + convinced myself, by the careful comparative investigation of numerous + ACANTHARIA, that in this respect they are quite distinct from the + SPUMELLARIA (with perhaps the exception of the Astrolophida, which are + nearly related to the primitive _Actissa_). The number of pores in the + ACTIPYLEA is usually very much smaller than in the PERIPYLEA, and they + are regularly arranged in groups. + + +59. _The Capsule-Openings of the Monopylea (or Nassellaria.)_--The +capsule-membrane of the MONOPYLEA always possesses a single large +main-opening, an osculum, which lies at the basal pole of the main axis, +and is closed by a circular perforated lid (operculum porosum). When seen +from the surface this lid appears as a clearly defined porous area +(porochora or area porosa), and forms the horizontal base of a peculiar +cone, which stands vertically in the interior of the capsule and may be +designated the "thread-cone" (podoconus). The NASSELLARIA may hence be +termed "Merotrypasta" or "Osculosa," like the CANNOPYLEA; the structure and +significance of the circular lid (operculum), which closes the main-opening +(osculum) is, however, quite different in the two legions. Whilst the lid +of the CANNOPYLEA (astropyle) is solid, traversed by radial ribs, and only +perforated in its centre by a short tube (proboscis), in the MONOPYLEA the +operculum (porochora) is always perforated by numerous vertical fine pores, +and is in connection with the peculiar internal "pseudopodial cone" +(podoconus, Pl. 51, figs. 5, 13; Pl. 81, fig. 16; Pl. 91, fig. 5; Pl. 98, +fig. 13). The pores are separated by small vertical, highly refractive rods +(opercular rhabdillae); these become intensely stained by carmine, and are +either evenly distributed over the surface of the porochora or arranged in +definite groups. The outer or distal end of each rod is rounded, sometimes +thickened like a club or split into lobes; the inner or proximal end is +usually pointed, and stands in connection with a myophane thread of the +podoconus (see s 79). The primary circular form of the porochora, in which +the opercular rhabdillae are evenly distributed in a horizontal plane, +undergoes various secondary modifications in many NASSELLARIA. The +triradial structure of the skeleton, which characterises the majority of +the legion, causes a splitting of the base of the central capsule into +three or four lobes; this division also affects the porochora, which lies +in the centre of the base, so that the rhabdillae become arranged in three +or four equal circles. If, however, the lobes of the central capsule become +larger and protrude through the three or four collar pores of the cortinar +septum, the central porochora may separate entirely into three or four +elongated tracts, which lie on the axial side of the magnified lobes; the +rhabdillae are then arranged over the whole surface of {xxxi}these tracts, +on the outer aspect of which run the longitudinal myophane fibrillae of the +podoconus (compare ss 79 and 99). + + The porous area of the MONOPYLEA was first described by Hertwig in 1879, + and shown to be the characteristic main-opening of the central capsule in + various families belonging to this legion (L. N. 33, pp. 71, 73, 83, 106, + Taf. vii., viii.). According to his view "the capsule-membrane in the + porous area becomes thickened around each pore into a rod, perforated by + a canal," and the intracapsular protoplasm passes outwards through these + fine canals (_loc. cit._, p. 106). I am not able to share this + interpretation, but think rather that I have convinced myself by the + examination of some living NASSELLARIA, and of many well-stained and + preserved preparations in the Challenger collection, that the rods are + _solid_, specially modified portions of the capsular wall, and that the + protoplasm does not pass through them but through pores which lie between + them. + + +60. _The Capsule-Openings of the Cannopylea (or Phaeodaria)._--The +capsule-membrane of the CANNOPYLEA always possesses only a single large +main-opening or osculum, which lies at the basal pole of the vertical main +axis, and is closed by a circular radiated lid (operculum radiatum). This +operculum appears, when seen from the surface, as a sharply defined +stellate area (astropyle), from the middle of which arises a shorter or +longer cylindrical tube, the proboscis. Hence the PHAEODARIA, like the +MONOPYLEA, belong to the "Merotrypasta" or "Osculosa"; the structure and +significance of the circular operculum, which closes the main-opening +(osculum), are, however, quite different in the two legions. Whilst the +operculum of the MONOPYLEA (porochora) is perforated by numerous fine +vertical pores, and connected with the peculiar internal pseudopodial cone +(podoconus), this structure is entirely wanting in the CANNOPYLEA, and +instead of it there is a solid operculum, with radial ribs which originate +at the base of its central tubular mouth; this tube (proboscis) is +cylindrical, often conical at the base, of very variable length and with a +round aperture at either end. In spite of the great difference which the +various families of CANNOPYLEA exhibit in the formation of their skeleton +and its appendages, the constitution of this characteristic stellate +main-opening (astropyle) is always essentially the same; both the stellate +operculum itself, and the proboscis which rises from its centre, show only +slight differences in the various groups. In addition to this large +main-opening most PHAEODARIA possess several small accessory openings +(parapylae); and usually two of these are present, placed symmetrically +right and left of the aboral pole of the main axis and in the frontal plane +(Pl. 101, figs. 2, 6, 10; Pl. 104, figs. 1, 2_a_). Sometimes there are more +numerous accessory openings (three to six or more) regularly arranged, as +in the two peculiar families, Circoporida and Tuscarorida; occasionally +also there is only a single parapyle, at the aboral pole of the main axis +(_e.g._, in _Tuscaridium_). The parapylae seem to be quite absent in the +families Challengerida, Medusettida, Castanellida, and perhaps also in +other PHAEODARIA. The form and structure of the small accessory openings +appear to be always the same. The {xxxii}outer capsule-membrane is elevated +in the form of a short cylindrical tube or "apertural ring" (collare +paraboscidis), the external margin of which bends inwards, and at the base +of the ring passes over into the delicate internal capsule membrane. Upon +this apertural ring is situated a longer or shorter "apertural cone" +(paraboscis), which is a tubular, cylindrical or conical, prolongation of +the membrane, open externally. + + The peculiar capsule-openings of the PHAEODARIA were first discovered and + carefully described by Hertwig in 1879 (L. N. 33, pp. 95, 107). He found + in all the six genera which he examined _three_ openings, a main-opening + at the basal pole of the main axis and two accessory openings, one on + either side of the apical pole; hence he named the whole group + "TRIPYLEA." This name, however, is not applicable to the numerous + PHAEODARIA mentioned above, which have only a main opening without any + accessory openings, nor to those genera in which the number of the latter + is variable. I have, therefore, replaced Hertwig's designation by the + term "CANNOPYLEA," which has reference to the peculiar tubular form of + the opening. This I find much more developed in many PHAEODARIA than + Hertwig has represented, and I must also, in certain particulars, dissent + from his delineation of the minute structure, although this is in the + main remarkably accurate. + + +61. _The Nucleus._--The nucleus, enclosed in the central capsule of all +Radiolaria, behaves in every respect like a true cell-nucleus, and thus +lies at the base of the now universal opinion, that the whole Radiolarian +organism, in spite of its varied development and remarkable variations, is +unicellular and remains throughout life a true individual cell. This +important theory is not invalidated by the fact that the nucleus undergoes +peculiar modifications in many groups, and in certain groups presents +appearances seldom or never seen elsewhere. + + +62. _Uninuclear and Multinuclear Radiolaria (Monocaryotic and +Polycaryotic)._--All Radiolaria present two different conditions in respect +of the behaviour of the nucleus, since in their young stages they are +uninuclear (_monocaryotic_), and in later stages multinuclear +(_polycaryotic_). This is readily explained by the fact that each +individual Radiolarian is developed from a simple unicellular swarm-spore, +and that afterwards, before the formation of swarm-spores, the single +nucleus divides into many small nuclei. Thus in the Radiolaria the nucleus +is pre-eminently the _organ of reproduction and inheritance_. The division +of the originally single nucleus into many small nuclei may take place, +however, at very different periods, so that the Radiolaria may be divided +in this respect into precocious and serotinous. + + +63. _Serotinous and Precocious Radiolaria._--In the great majority of the +Radiolaria the division of the nucleus takes place only at a late period, a +short time or even immediately before the process of spore formation; it +then breaks up rapidly into numerous small nuclei (always more than one +hundred, sometimes many thousands), and each of these {xxxiii}either +becomes itself the nucleus of a swarm-spore, or by repeated division gives +rise to a group of spore-nuclei. All those Radiolaria which are uninuclear +during the greater part of their existence, and in which the process of +division is late, and takes place rapidly, are called "serotinous" or +late-dividing forms. To this category belong all PHAEODARIA and +NASSELLARIA, as well as all the solitary or monozoic SPUMELLARIA and some +ACANTHARIA. On the other hand, the name "precocious," or early dividing, is +applied to those Radiolaria in which the division of the nucleus takes +place very early, and in which, therefore, the cell is multinuclear during +the greater part of its existence. This is the case in all the social or +polyzootic Radiolaria (Polycyttaria, Pls. 3-8), and also in the great +majority of the ACANTHARIA, both #Acanthometra# and #Acanthophracta#. In +the last two groups, however, there are numerous exceptions, and these are +seen in remarkably large species, characterised by the great size of the +central capsule. From a phylogenetic point of view, the conclusion is +allowable that the precocious forms are secondary, and have arisen by +adaptive modification from the primitive serotinous stem. In the +Polycyttaria (or social SPUMELLARIA, _i.e._, the three families Collozoida, +Sphaerozoida, and Collosphaerida), the cause of the adaptation lies most +probably in the formation of the colony itself, for all these three +families are so closely related to three corresponding families of +serotinous, monozootic Radiolaria (Thalassicollida, Thalassosphaerida, +Ethmosphaerida), that certain species of the latter are hardly to be +distinguished from isolated individuals of the former. Perhaps the +remarkable formation of the large central oil-globule, which particularly +characterises the Polycyttaria, is the prime cause of their early nuclear +division. In the ACANTHARIA the cause is most likely to be found in the +characteristic _centrogenous development_ of their acanthin skeleton, whose +radial bars first of all appear in the centre of the capsule. Hence arises +directly the excentric position of the nucleus, which in the archaic stem +of ACANTHARIA (_Actissa?_) was probably central. In any case, but little +weight is to be laid upon the precocious division of the nucleus in the +ACANTHARIA in general, inasmuch as in certain species (both #Acanthometra# +and #Acanthophracta#) the more usual serotinous division persists. + + +64. _Central and Excentric Nuclei._--The position of the nucleus in the +interior of the central capsule was no doubt primitively central, and this +situation in the geometrical centre of the original spherical central +capsule has been accurately retained in all monozootic SPUMELLARIA; in the +polyzootic families of this legion (Polycyttaria), on the contrary, it is +obscured by the precocious division of the nucleus. In the other three +legions, which may be phylogenetically derived from the SPUMELLARIA, the +position of the nucleus is rarely central, but usually excentric, or at +most subcentral. In the ACANTHARIA (both #Acanthometra# and +#Acanthophracta#) the central position of the nucleus is at once excluded +by the constantly centrogenous development of the skeleton; the nucleus is +therefore always excentric, and may lie at either side; it usually +{xxxiv}divides very early into numerous separate nuclei, which are usually +distributed in the peripheral portions of the central capsule. In the +NASSELLARIA the development of the porochora, and of the podoconus which +stands upon it, brings about the formation of a vertical axis, and in +consequence the central capsule assumes a monaxon form (usually ovoid or +conical); the nucleus then lies in the main axis, but excentrically between +the apex of the podoconus and the aboral pole. In many NASSELLARIA, +however, especially when the podoconus is so large that its apex approaches +the aboral pole of the central capsule, the nucleus is pressed to one side +and lies quite excentrically. The PHAEODARIA exhibit a different +arrangement; the large spheroidal nucleus is always subcentral, so that its +main axis corresponds with that of the concentric spheroidal central +capsule; but since the astropyle always occupies the oral pole of the +latter, and since the distance of the nucleus from this pole is always +somewhat different from its distance from the other, it follows that, +strictly speaking, the nucleus never lies accurately in the geometrical +centre. + + +65. _Homogeneous and Allogeneous Nuclei._--The nucleus of the Radiolaria +not only exhibits a similar structure and composition, and suffers similar +modifications to those which are found to occur in the case of other +cell-nuclei, but also to some extent shows very peculiar developmental +forms, which are seldom or never found in other cells. In the first place +the nuclei may be divided into homogeneous and allogeneous, the former are +structureless and consist of a uniform mass of nuclein, whilst the latter +are composed of different substances and show various structural relations. +_Homogeneous_ nuclei, whose whole mass is uniform and exhibits no +structural differentiation, are probably always to be found in the +swarm-spores; in the fully developed Radiolarian body they are found only +in the first legion, SPUMELLARIA, and that both in many Monozoa (especially +small #Sphaeroidea# and #Prunoidea#) and in the Polyzoa (or Polycyttaria). +The whole mass of these homogeneous nuclei, which are usually spherical or +ellipsoidal, consists of uniform, perfectly clear and transparent nuclein, +and becomes evenly stained by carmine, haematoxyline, &c. They may be +readily distinguished by these means from the clear vacuoles or "hyaline +vesicles," which are evenly distributed in the endoplasm of many +Radiolaria, and may be confused with the former. _Allogeneous_ nuclei, +which are always composed of different parts and often show complicated +structural relations, are found developed in the great majority of +Radiolaria. The most important differentiation exhibited by these secondary +forms is the separation of the nuclear mass into a firm nuclear substance +(caryoplasm) and a fluid nuclear juice (caryolymph). In addition in each +nucleus a nucleolus is visible, and often several or many may be seen (see +ss 67 to 70). + + +66. _The Form of the Nucleus._--The nucleus of the Radiolaria shows greater +variations in form and structure than are to be found in the majority of +cell-nuclei; {xxxv}exception must, however, be made in the case of many +animal ovicells, which, in their peculiar form and composition, often +recall large Radiolarian nuclei. With respect to the external shape two +main forms may be distinguished, as primary and secondary. The _primary +form_ of the Radiolarian nucleus is the sphere; it occurs not only in most +swarm-spores, but also in most adult forms belonging to the legion +SPUMELLARIA, and in individual instances in other groups; indeed the nuclei +of most SPUMELLARIA, as also the concentric central capsules in which they +lie, are true geometrical spheres. The _secondary forms_ of the nucleus are +found in the majority of adult Radiolaria, and arise from the primary +spherical forms in various ways, either by the elongation or contraction of +one axis, or by the formation of apophyses or processes. The most important +of these secondary forms are as follows:-- + + 1. _Ellipsoidal nuclei_, arising by elongation of one principal axis; + very common among the NASSELLARIA, as well as in many #Prunoidea# and + #Larcoidea# among the SPUMELLARIA; also in several ACANTHARIA. + + 2. _Discoidal nuclei_, arising by contraction of one principal axis, + sometimes lenticular or spheroidal, biconvex, sometimes shaped like a + disc or coin; especially common in the #Discoidea# among the SPUMELLARIA, + also in some ACANTHARIA; the large nucleus of the PHAEODARIA is always + spheroidal or almost spherical, with a slightly shortened main axis. + + 3. _Stellate nuclei_, spherical, and armed with evenly distributed radial + club-shaped or conical processes; rare but very characteristic, + especially in the two large Thalassicollida _Thalassopila_ (Pl. 1, fig. + 3), and _Thalassophysa_ (Monogr. d. Radiol., Taf. i.); also in some + #Sphaerellaria# (Pl. 11, fig. 5). + + 4. _Amoeboid nuclei_, with unequal processes irregularly arranged, in + certain irregular forms of SPUMELLARIA and ACANTHARIA. + + 5. _Lobate nuclei_, with several (usually two or three) large ovoid or + pyriform lobes, which protrude into corresponding larger lobes of the + central capsule, in many NASSELLARIA, especially the multiarticulate + #Cyrtoidea# (Pl. 59, figs. 12, 13). The budding nucleus of the ACANTHARIA + is also lobate (Pl. 129, figs. 6-11). + + +67. _The Nucleus of the Peripylea._--The nucleus of the SPUMELLARIA or +PERIPYLEA shows in certain groups a very primitive arrangement, indeed the +archaic structure from which the various forms of nuclei of other +Radiolaria may be derived; but on the other hand, in other groups it +exhibits very peculiar and remarkable differentiations. In the first place +it may be noted that the monozootic or solitary SPUMELLARIA usually possess +a single serotinous nucleus, which only divides into numerous swarm-spores +at a late period; {xxxvi}whilst, on the contrary, the polyzootic colonial +SPUMELLARIA (or Polycyttaria) are uninuclear only in the young state (Pl. +3, fig. 12), and speedily present numerous small homogeneous nuclei, which +have arisen by precocious division of a single nucleus; these are usually +spherical and 0.008 to 0.012 mm. in diameter. The serotinous nucleus of the +monozootic SPUMELLARIA, in many divisions of this large legion, and +especially in the simply constituted #Sphaeroidea#, is a homogeneous sphere +of nuclein, lying in the middle of the central capsule. In many other cases +it assumes the form of a spherical vesicle ("Binnen-Blaeschen"), whose +fluid or semi-fluid contents are enclosed by a more or less firm membrane. +This vesicle often contains a single central spherical _nucleolus_ (Pl. 1, +figs. 1_l_, 4_l_), but sometimes a variable number of small excentric +nucleoli (Pl. 1, figs. 1_a_, 2_a_). The nuclear membrane is often somewhat +thick, presenting a double contour, and in such cases may even exhibit a +fine radial striation, the expression of minute pores (Pl. 1, fig. 2_a_). +In the colossal nuclei (as much as 1 to 2 mm. in diameter) of certain large +Thalassicollida the nucleolus presents a very remarkable form, becoming +stellate by the protrusion of processes, which may again branch in a +dendritic fashion (as in the common _Thalassicolla nucleata_), or it may +develop into a very long cylindrical thread, which is disposed in +serpentine coils, and in _Thalassophysa pelagica_ passes into the different +caecal processes of the stellate nucleus. In many #Sphaeroidea#, whose +skeleton is composed of numerous concentric lattice spheres, the small +central spherical nucleus lies at first within the innermost of these (the +medullary shell); but afterwards it grows through the meshes of the +lattice-work, and the radiating club-shaped processes thus formed (Pl. 11, +fig. 5) unite with each other outside the medullary shell, and form an +external nuclear sphere which completely encloses the latter. In the +Polysphaerida (with several concentric lattice-shells) and in the +Spongosphaerida (with spongy lattice-spheres), this process may be several +times repeated, so that eventually the central spherical nucleus attains +considerable dimensions, and encloses two or more concentric lattice-shells +with their radial connecting rods. The nuclear membrane is in these cases +usually penetrated by radial bars, which connect the outermost of the +enclosed shells with the remaining cortical shells which surround the +central capsule. The same remarkable arrangement is also very common among +the #Discoidea#. The small spherical primary nucleus is in such instances +immediately surrounded by the innermost earliest developed lattice-shell, +around which the concentric rings are subsequently deposited; it then grows +out through the meshes, and the processes fuse outside the ring to form a +homogeneous lentiform nucleus (Pl. 43, fig. 15). The same process recurs in +certain #Prunoidea# and #Larcoidea#, whilst in other SPUMELLARIA of these +groups (_e.g._, Pylonida) the lobate processes of the nucleus remain free. + + Both the simple serotinous nucleus of the monozootic SPUMELLARIA, and the + numerous precocious nuclei of the Polycyttaria, were first described in + my Monograph in 1862, the former as the "endocyst" ("Binnen-Blaeschen"), + the latter as "spherical transparent vesicles" ("Kugelige + {xxxvii}wasserhelle Blaeschen"). I was in error, however, in regarding + the latter as identical with the so-called "hyaline spherules" in the + central capsule of many Monozoa, which rather belong to the category of + intracapsular vacuoles (see s 72). The credit of recognising, by the aid + of the modern methods of staining, the distinctness of these two + structures, which may readily be mistaken for each other, and of + demonstrating the true nature both of the serotinous and precocious + nuclei, belongs to Richard Hertwig (1879, L. N. 33). + + +68. _The Nucleus of the Actipylea._--The nucleus of the ACANTHARIA or +ACTIPYLEA shows very peculiar relations in respect of structure and +division, particularly special forms of lobular budding, which belong to +the characteristic peculiarities of this singular legion, and are not found +among other Radiolaria. The position of the nucleus is _always excentric_, +even in the youngest ACANTHARIA, for the centrogeneous formation of the +skeleton, the constant development of the earliest radial portions of it in +the middle of the central capsule, forces the nucleus from its normal +central position. The majority of the ACANTHARIA, like most Polycyttaria, +are precocious, the primary nucleus early dividing into numerous small +nuclei (see note A below). Nevertheless there are many exceptions to this +rule in different families, _e.g._, _Stauracantha_, _Xiphacantha_, +_Phatnacantha_, and _Pristacantha_ among the #Acanthometra#, and +_Stauraspis_, _Echinaspis_, _Dodecaspis_, and _Phatnaspis_ among the +#Acanthophracta#. In these instances the primary nucleus remains for a long +time as a simple excentric ellipsoidal or irregularly round body, even in +the fully developed stage, and only at a very late period (sometimes just +before the formation of the spores) divides into many small nuclei. Since +this serotinous division of the nucleus takes place in different genera of +very various groups, it can only be decided by further investigations how +widely it is spread among the ACANTHARIA, and upon what circumstances it is +dependent (see note B). The division of the nucleus appears to be +precocious in the majority of this legion, and a number of small nuclei +appear to be early formed by a peculiar process of budding; in most fully +developed ACANTHARIA these are disposed in one or two layers under the +surface of the central capsule, but if their numbers increase to any +considerable extent, the whole space between the skeletal rods becomes +filled with small nuclei; sometimes these are homogeneous, sometimes +vesicular, 0.002 to 0.012 mm. in diameter; usually they are spherical and +have a small nucleolus (compare Pl. 129, figs. 6-11, and note C). + + A. The numerous nuclei, which are to be found in the central capsule of + most mature ACANTHARIA, were first described in my Monograph (1862) as + "spherical, transparent vesicles, provided with a small dark granule" (p. + 374, Taf. xv. figs. 2, 5; Taf. xvi. figs. 2, 4; Taf. xxi. fig. 7, &c.). + Their more minute constitution and peculiar origin were first accurately + delineated by R. Hertwig (1879, _loc. cit._, pp. 11-24, Taf. i-iii.). + + B. The fact that in a number of ACANTHARIA the nucleus does not divide + early as in the majority of the legion, but only at a later period, was + first observed by R. Hertwig in a species of #Acanthometra# (_Xiphacantha + serrata_), and a species of #Acanthophracta# (_Phatnaspis + {xxxviii}muelleri_ = _Haliommatidium muelleri_) (_loc. cit._, pp. 11 and + 27). This serotinous division of the nucleus seems, however, to be rather + widely spread in both sublegions of the ACANTHARIA; I have found, not + only in the forms above mentioned, but also in several others belonging + to different genera, a single large excentric nucleus, even in those + individuals in which the skeleton was fully developed. + + C. The peculiar mode of nuclear budding, by which these small nuclei + arise, appears to proceed in the following manner (Pl. 129). The + vesicular primary nucleus, which, in consequence of the centrogeneous + development of the skeleton protrudes as it grows into irregular lobes + (Pl. 129, fig. 9), assumes a peculiar concavo-convex form, sometimes that + of a hood or dish, sometimes that of a kidney or sausage. The convex + surface is apposed to the capsule-membrane, while the concave is turned + towards the central star of the skeleton (fig. 6). There is now formed at + the centre of the convex surface of the strong, doubly-contoured, nuclear + membrane, a flask-shaped invagination with a narrow neck and expanded + base; the membrane now becomes disposed in peculiar folds, which at the + narrow aperture of invagination appear as folds, but on the expanded body + of the flask take the form of concentric rings, laid closely side by side + (Pl. 129, fig. 10). The convex bottom of the flask, which is directed + towards the concave proximal side of the nucleus, becomes again + invaginated by a central conical apophysis of the enlarged nucleolus, + which is situated between them. Usually the nucleolus has already become + flattened into a lentiform shape, and upon its distal face a conical + apophysis has been developed, which is divisible into a darker proximal + and clearer distal portion. The tip of the latter appears to be in direct + connection with the nuclear membrane at the centre of the base of the + flask-shaped invagination (figs. 6, 10). At this stage of development the + nucleus of the ACANTHARIA generally presents the characteristic form of a + hood-shaped, concavo-convex vesicle, whose radial axis is also the axis + of the flask-shaped distal invagination, and of the depressed conical + nucleolus, which lies between the latter and the concave side of the + nucleus. After this peculiar invagination has persisted for some time in + connection with the enlarged nucleolus, both disappear, and then a + remarkable growth of lobular processes takes place on the concave + proximal side of the hood or kidney-shaped nucleus; from four to eight + knobs of unequal size usually appear, and their thickened wall encloses a + variable number of small of nucleoli; these are at first few but + afterwards more numerous (fig. 7). Subsequently these knobs or lobes + become completely separated by constriction from the original central + mass of the nucleus, and appear as so many separate independent + "sausage-shaped bodies" in the hollow central capsule (fig. 8). Each of + the bodies now appears, and at first on its convex aspect, to form a + large number of small nucleoli, which either separate by constriction + from it or become free by its breaking up and lie in numbers in the + central capsule. Finally the buds or lobes of the nucleus break up + entirely into such nucleoli, which are evenly distributed in the central + capsule, and become the nuclei of the swarm-spores (fig. 11). Compare R. + Hertwig, L. N. 33, Taf. i.-iii. pp. 19-25. + + +69. _The Nucleus of the Monopylea._--The nucleus of the mature forms of the +NASSELLARIA or MONOPYLEA is generally simple or lobate, homogeneous or +vesicular and _excentric_, and appears only to divide into numerous small +nuclei just before the formation of the spores. Nevertheless I have +sometimes, though not often, seen in representatives of very various +families of the MONOPYLEA, the central capsule filled with many small +spherical homogeneous nuclei (Pl. 53, fig. 19). Hence all the families of +this legion appear to be serotinous, their simple primitive nucleus +persisting for a long period. It {xxxix}is commonly placed excentrically, +and most usually in the apical or aboral portion of the central capsule, +either between its apex and the podoconus, or quite excentrically on the +dorsal aspect. The simple nucleus of the NASSELLARIA usually appears to be +vesicular and to possess a somewhat firm membrane, clear contents, and a +rather large, dark coloured nucleolus. In many NASSELLARIA the nucleus is +spherical or ellipsoidal (Pl. 53, fig. 11); whilst in many #Stephoidea# and +#Spyroidea#, where the central capsule is constricted by the sagittal ring +and divided into two symmetrical lateral lobes, the nucleus partakes of the +same mode of growth and appears in the middle of the capsule as a +transversely placed ellipsoid or even as a short cylinder (Pl. 90, figs. 7, +9). The most remarkable modification in the form of the nucleus is to be +found in the multi-articulate #Cyrtoidea#. Here it is usually enclosed in +the cephalis and is spherical, ellipsoidal or spheroidal, often flattened +almost into a disc. If now the central capsule increase greatly in size and +put forth three or four clavate lobes which hang down through the pores of +the cortinar septum into the thorax (or even into the succeeding joints), +the nucleus usually undergoes similar modification, and three or four +finger-like apophyses are developed from its base, which project into the +corresponding lobes of the central capsule (Pl. 59, figs. 4, 12, 13). + + The numerous small, spherical, homogeneous nuclei which are to be found + in the central capsules of those NASSELLARIA, which are ripe and about to + develop spores, were described in 1862 in my Monograph, as "numerous, + small, transparent, spherical cells" in the case of various #Cyrtoidea# + (_Arachnocorys_, _Lithomelissa_, _Eucecryphalus_, _Eucyrtidium_, &c.) + (_loc. cit._, pp. 302, 305, 309, 321, &c.), and I find them of the same + form and dimensions, but deeply stained with carmine in many preparations + in the Challenger collection. R. Hertwig has delineated them very + accurately in the case of _Tridictyopus_ (1879, _loc. cit._, p. 84, Taf. + vii. fig. 3). He was also the first to recognise the uninucleate + condition of the NASSELLARIA, which is much more frequently observed than + the serotinous multinucleate condition, and he described very clearly the + peculiar lobed nuclei which arise in #Cyrtoidea#, owing to the protrusion + of the nucleus through the cortinar septum (_loc. cit._, p. 85, Taf. + viii. figs. 3-8). + + +70. _The Nucleus of the Cannopylea._--The nucleus presents the same +remarkable structures in all species of the PHAEODARIA or CANNOPYLEA which +have been examined, and closely resembles the germinal vesicle of an +amphibian ovum, being a large spherical or spheroidal vesicle with numerous +nucleoli. Its diameter usually amounts to half or two-thirds, sometimes +even three-quarters, that of the central capsule. The vertical main axis of +the latter is also that of the nucleus, which usually lies somewhat nearer +to the aboral pole. The nucleus is generally rather more strongly +compressed in the direction of the main axis than the capsule itself. The +membrane of the vesicular nucleus is thin, but firm, and encloses a clear +or finely granular mass of nuclein. The number and size of the contained +nucleoli are variable even in one and the same species, and stand in +inverse ratio to each other, an obvious result of the gradual process of +division. Commonly {xl}from twenty to fifty roundish or spherical, strongly +refracting nucleoli, are present; more rarely there are several hundred +very small ones. Sometimes the nucleus is penetrated by fine trabeculae, +in whose meshes lie the nucleoli (Pl. 101, fig. 2). In certain nuclei, +which contained a few large nucleoli, these were of irregular form, +probably the result of amoeboid movements (Pl. 101, fig. 1). In the +formation of spores in the CANNOPYLEA, the nucleus apparently becomes +dissolved, and its numerous nucleoli develop directly into the nuclei or +mother-nuclei, which produce the nuclei of the flagellate spores. +Furthermore, many PHAEODARIA seem to multiply by simple cell-division, +since very commonly (especially in the #Phaeocystina# and #Phaeoconchia#) +two large nuclei (right and left), may be met with in one central capsule; +sometimes also a single large nucleus, in which a sagittal constriction +marks the commencing division of the capsule (Pl. 101, figs. 2, 36; Pl. +104, fig. 3; Pl. 124, fig. 6, &c.). + + The large nucleus of the PHAEODARIA was first described in my Monograph + in 1862, in the case of _Aulacantha_ (p. 263), _Aulosphaera_ (p. 359), + and _Coelodendrum_ (p. 361), as a "large, spherical, thin-walled + endocyst," from 0.1 to 0.2 mm. in diameter. More detailed descriptions, + especially with respect to the behaviour of the nucleoli were given by R. + Hertwig in 1879 (L. N. 33, p. 97). + + +71. _The Endoplasm or Intracapsular Protoplasm._--In all Radiolaria the +intracapsular protoplasm, which, for the sake of brevity, may be termed +"endoplasm," constitutes originally, and especially in the earliest stages, +the only important content of the central capsule, except the nucleus. In +certain SPUMELLARIA and NASSELLARIA, of simple structure and of small +dimensions, this condition persists for a long period, and the endoplasm +then appears as a homogeneous, colourless, turbid or finely granular, +mucous, semi-solid mass, which cannot be distinguished from the ordinary +undifferentiated protoplasm of young cells; no definite structure, and in +particular, no fibrillar network, can be discovered in it even by the use +of the customary reagents. In the great majority of the Radiolaria, +however, this primitive homogeneous condition of the endoplasm is very +transient, and it soon undergoes definite modifications, becoming +differentiated into separate parts or producing new constituent contents. +Such products of the internal protoplasm are in particular hyaline spheres +(vacuoles and alveoles), oil-globules, pigment-bodies, crystals, &c. The +most important of the differentiations which take place in the endoplasm is +that into an internal, granular, _medullary_ substance and an external, +fibrillar, _cortical_ substance; although the various legions behave +somewhat differently in this respect (ss 77-80). + + +72. _Intracapsular Hyaline Spheres._--The central capsule of very many +Radiolaria contains in its endoplasm numerous spherical bodies of varying +size, which consist of watery or albuminous fluid, and have previously been +regarded as nuclei, or described as products of the internal protoplasm, +under various names, such as "spherical transparent {xli}vesicles" (see +note A, below), "albumen spheres" (see B), "gelatinous spheres" (see C), +"alveolar cells" (see D), &c. Some of these spheres are perfectly +transparent, structureless and of varying refractive power, producing the +impression of drops of fluid; others contain various formed constituents, +such as oil-globules, fat-granules, pigment-granules, concretions, +crystals, &c. From a morphological point of view they may all be divided +into two categories, membraneless vacuoles and vesicular alveoles. The +_vacuoles_ are simple spherical drops of fluid or of gelatinous material, +devoid of a special envelope, but immediately surrounded by the endoplasm. +The _alveoles_, on the other hand, are true vesicles with a thin spherical +envelope, enclosing a drop of fluid or jelly. This envelope is commonly +very thin, homogeneous, and often scarcely discernible, so that in practice +a sharp line of demarcation cannot be drawn between alveoles and vacuoles; +the former are usually somewhat larger than the latter. The fact is, +nevertheless, certain that the hyaline spheres, which may be isolated on +rupturing the central capsule of many Radiolaria, in certain cases, +particularly in large species, possess a clear, anatomically demonstrable +membrane, whilst in others no such appearance is presented. It may be +assumed that the vesicular alveoles are developed from the drop-like +vacuoles by increase in size, and by the precipitation of a delicate +envelope from the endoplasm. The character common to all these hyaline +spheres, whether vacuoles or alveoles, is found in their aqueous, not +adipose, constitution, and in their clear transparent appearance, which +allows of no structure (the above-mentioned contained bodies excepted) +being recognised. Their refractive power and consistency vary somewhat, and +probably their chemical constitution still more. Sometimes they are +strongly refractive and shining, and sometimes feebly refractive and pale; +their consistency shows all intermediate stages between a thin fluid, which +readily disappears in water, and a firm, insoluble jelly. As regards their +chemical composition (which is probably very variable), the hyaline spheres +may be best divided into two groups, the organic and inorganic. The +_inorganic hyaline spheres_ are simple drops of saline solution without any +carbonaceous constituent; the _organic_, on the other hand, contain a small +quantity of organic matter dissolved in the watery fluid, and may be either +albuminous or gelatinous spheres. The formed contents which are commonly +present are of very various natures, usually small fat-granules, more +rarely larger fat-granules or pigment-granules, sometimes concretions or +crystals. In many groups, especially among the large PHAEODARIA and +#Collodaria#, the numerous hyaline spheres are remarkable for their equal +size and even distribution throughout the endoplasm (Pl. 1, figs. 1, 4; Pl. +104, fig. 2, &c.). In some genera belonging to the Thalassicollida the +alveoles are of enormous size (Pl. 1, figs. 2, 3); they then become +flattened by mutual pressure into polyhedra and distend the central capsule +to unusual dimensions (in _Physematium_ and _Thalassolampe_ 8 to 12 mm.). + + A. The "_spherical hyaline vesicles_," which I described in my Monograph + (1862, p. 71) as among the most important and constant contents of the + central capsule, are partly vacuoles, {xlii}partly homogeneous nuclei. + Most recent investigators, Buetschli in particular (1882, L. N. 41), have + pointed out and rightly criticised this confusion. The criticism might, + however, have been more justly expressed by stating that, in the + preparation of my Monograph (1859-1862), I did not make use of modern + methods of demonstrating the nucleus by staining fluids, which were quite + unknown at the time, and only discovered a decade later. In fact, without + the aid of such reagents, it is quite impossible to distinguish between + the various "spherical transparent vesicles," of which those found in the + central capsule of the PHAEODARIA and many monozootic #Collodaria# are + simple vacuoles lying in the endoplasm, whilst, on the other hand, those + of the Polycyttaria and many other Radiolaria are true homogeneous + nuclei. For not only are the general appearance of the small clear + spheres, their refractive power, and regular distribution in the + endoplasm quite similar, but they are also of much the same size, for the + diameter ranges from 0.005 to 0.015 mm., being generally between 0.008 + and 0.012 mm. In addition to this there is generally in each hyaline + sphere a dark brightly shining granule, which, in the case of the + vacuole, is simply a fat-granule, whilst in the case of the nucleus, it + is a true nucleolus. The small hyaline spheres in the young uninucleate + capsules of the Polycyttaria are simple vacuoles (Pl. 3, fig. 12), whilst + in the ripe multinucleate capsules they are true nuclei (Pl. 3, figs. 3, + 8, 9), and it is quite impossible to discriminate between these two + conditions without the use of reagents. This has been expressly + recognised by R. Hertwig, who has the merit of having been the first to + clearly distinguish, by the aid of staining fluids, between these two + different constituents (1879, L. N. 33, p. 108). + + B. The "_albumen spheres_," which were first observed by A. Schneider in + 1858 in the common cosmopolitan _Thalassicolla nucleata_ (L. N. 13, p. + 40), and which appear to occur in only a few other Thalassicollida, are + distinguished from the ordinary hyaline spheres of about the same size by + their higher refractive power and by certain albuminoid reactions, + especially the coagulation of a membranous envelope under the influence + of certain reagents (see my Monograph, p. 250, and Hertwig, L. N. 26, + 1876, p. 46). They often enclose various formed contents, and require + further investigation. + + C. The _gelatinous spheres_ of various sizes, found in the endoplasm of + the Radiolaria, agree in their reactions (especially in staining by + certain reagents) with the common extracapsular jelly of the calymma, and + are hence distinguishable both from the true (coagulable) "albumen + sphere," and from the ordinary watery vacuoles. + + D. The _alveoles_, which are only accurately known in the case of certain + large monozootic #Collodaria#, but which also seem to occur in the + central capsule of other remarkably large Radiolaria, were described in + my Monograph in the case of _Thalassolampe margarodes_ and _Physematium + muelleri_, under the name "intracapsular alveolar cells" (1862, pp. 77, + 254, 257). They are not, however, true nucleated cells, and the body + described as a nucleus is not such in reality. Nevertheless these large + hyaline spheres do possess a special envelope, as I have recently + convinced myself by the examination of ruptured central capsules of + _Thalassolampe maxima_, _Thalassopila cladococcus_, and _Physematium + atlanticum_ (Pl. 1, figs. 2, 3). The central capsule of these + #Collodaria# becomes distended to most unusual dimensions (2 to 12 mm. in + diameter) by the great development of these large hyaline vesicles, each + of which measure from 0.1 to 0.5 mm. in diameter. + + +73. _The Intracapsular Fat-Globules._--Fat is present in the central +capsule of all Radiolaria in larger or smaller quantities, and generally +appears in the form of very {xliii}numerous, small, spherical granules, +which are either distributed evenly in the endoplasm (as an emulsion) or +enclosed in the vacuoles; the latter, in particular, is the case in most +PHAEODARIA, perhaps generally. In this group each vacuole contains as a +rule a single dark, shining fat-granule, and sometimes also an irregular +bunch composed of from two to five or more granules. In addition to these +small fat-granules (_granula adiposa_) which are always present, the +central capsule of many Radiolaria contains also larger fat-globules +(_globuli adiposi_). These appear to be generally wanting in the +PHAEODARIA, and are on the whole rare in the ACANTHARIA; whilst, on the +contrary, they are very common in the NASSELLARIA and SPUMELLARIA. The +Polycyttaria or social Radiolaria are as a rule distinguished by the +possession of a single large central oil-globule, which lies in the centre +of the central capsule, and is on an average about one-third of it in +diameter (Pl. 3, figs. 4, 5). This is absent, however, in those young +capsules of the Polycyttaria in which the primary nucleus is centrally +situated (Pl. 3, fig. 12). Those species of Polycyttaria whose central +capsule reaches a considerable size, often enclose numerous oil-globules, +and in _Collophidium_ (species of _Collozoum_ with an elongated cylindrical +capsule, Pl. 3, figs. 1, 3) the axis of each capsule is occupied by a row +of numerous oil-globules. In the monozootic SPUMELLARIA, in which the +nucleus is always centrally situated, the large oil-globules are, of +course, excentric, being in apposition to the inner surface of the +capsule-membrane (Pl. 1, fig. 3; Pl. 2, figs. 2, 5). In the #Discoidea# the +oil-globules, which are often present in large numbers, form elegant +concentric rings around the central nucleus, and in those species with +segmented arms, there are one or more transverse rows in each segment (Pl. +43, fig. 15). In the NASSELLARIA the number and distribution of the +oil-globules are dependent upon the form of the central capsule. When this +is simple, without lobes, and ovoid or conical, they generally lie in its +aboral half above the podoconus (Pl. 51, figs. 5, 13; Pl. 97, fig. 1). +When, on the contrary, the basal portion of the capsule sends out three or +four dependent processes (as in the majority of the #Cyrtoidea#), a large +globule may generally be seen in the swollen distal part of each conical or +ovoid lobe (Pl. 53, fig. 19; Pl. 60, figs. 4-7). In many #Stephoidea# and +#Spyroidea#, whose central capsule is separated into two lateral portions +by the constriction corresponding to the sagittal ring, each of these +contains either a single large globule or a group of small ones (Pl. 90, +figs. 7, 10). These oil-globules are usually colourless and highly +refractive; rarely they are yellow or brown, sometimes rose-coloured, or an +intense blood-red (_e.g._, in _Thalassophysa sanguinolenta_) or even orange +(in _Physematium muelleri_). In many SPUMELLARIA, and particularly in the +Polycyttaria, an albuminous substratum may be recognised in them, which is +sometimes disposed in layers, and after extraction of the fat presents the +appearance of a laminated sphere. The physiological significance of the +oil-globules is twofold; in the first place they tend to diminish the +specific gravity of the organism; in the second they may be utilised as a +reserve store {xliv}of nutriment. In the latter respect they are of special +importance in the process of spore-formation, each flagellate spore usually +containing a fat-granule. + + +74. _The Intracapsular Pigment-Bodies._--In the majority of Radiolaria when +observed alive, the central capsule is coloured, only in the minority is it +colourless. The colour is never diffuse, but always due to the formation +of definite pigment granules or vesicles, which are sometimes distributed +evenly throughout the endoplasm, sometimes aggregated in the central or +peripheral regions. Their form may be either spherical, irregularly +rounded, or polyhedral. They vary much in dimensions, but in most cases +are immeasurably small, and appear under a high magnifying power as fine +dust; occasionally, however, their diameter may amount to from 0.001 to +0.005 or more. The chemical constitution of the intracapsular pigment is +unknown in most Radiolaria, and is probably very various. In many instances +the pigment-granules consist of fat, in others not. The commonest colours +are yellow, red, and brown; violet and blue are rare, and green still +rarer. Sometimes a definite tone of colour prevails throughout a whole +group, and may then be attributed to inheritance, _e.g._, red is found in +most #Sphaeroidea#, and blue in the Polycyttaria (see note A). One colour +is almost always constant in the members of the same species. True +pigment-cells, belonging to the Radiolarian organism, do not occur within +the central capsule. The peculiar yellow cells which are found in the +central capsule of many ACANTHARIA are symbiotic xanthellae (see s 76). + + A. The number of Radiolaria whose pigment has been examined in the living + state, is too small to allow of any general conclusions being drawn. + Regarding the different colours known, see my Monograph, L. N. 16, p. 76. + + +75. _The Intracapsular Crystals._--The crystals found in the central +capsule of many Radiolaria may be divided into two groups, of very +different significance; small crystals, which are very widely distributed, +and large crystals, which occur in only a few genera. The _small crystals_ +may also be termed "spore-crystals," since each swarm-spore often contains +such a crystal. They are rod-like or spindle-shaped, and consist of an +organic substance which probably serves as a reserve of nutriment for the +developing spores. Such spore-crystals have been observed in numerous +SPUMELLARIA and ACANTHARIA belonging to various families, and are probably +present throughout the two legions which make up the Porulosa. On the other +hand, they have not been noticed in the Osculosa (NASSELLARIA and +PHAEODARIA), the few swarm-spores belonging to these groups which have been +observed not exhibiting any crystals. The _large crystals_, which occur in +small numbers in the endoplasm, have hitherto only been observed in a few +species of SPUMELLARIA, belonging to the Polycyttaria. They were first +noticed in the common _Collosphaera huxleyi_, and regarded as coelestin. +They are also found in the central capsule of many other Collosphaerida, +_e.g._, _Buccinosphaera_ (Pl. 5, figs. 11, 12). Crystal-masses, +crystal-sheaves, or spherical masses of radiating acicular crystals are +enclosed in {xlv}the vacuoles or "albumen globules" of _Thalassicola +nucleata_ and other Thalassicollida, as well as in the central capsule of +_Coelographis_ and some other PHAEODARIA (Pl. 127, figs. 4-7). All these +large crystals are probably to be regarded as excretory products. + + +75A. _The Intracapsular Concrements._--Concretions, either mineral or +organic, of varying form and constitution, are to be found in the endoplasm +of Radiolaria belonging to very different families. They are most abundant +and multiform in _Thalassicolla nucleata_, being usually circular or +elliptical discs, which are concentrically laminated and highly refractive, +resembling starch-grains. Among them twin forms may frequently be observed, +as though the concrements were in process of division (see note A). Similar +amyloid concretions are to be seen in the central capsule of different +SPUMELLARIA and NASSELLARIA, _e.g._, in _Cephalospyris triangulata_ (Pl. +96, fig. 28). Violin-shaped, highly refractive concrements have been +observed in the central capsule of numerous SPUMELLARIA, NASSELLARIA, and +ACANTHARIA, _e.g._, _Thalassosphaera_, _Spongosphaera_, _Plegmosphaera_, +_Cyrtocalpis_, _Peripyramis_, _Botryocella_, &c. (see note B). The chemical +constitution of these concrements is insufficiently known. + + A. The amyloid concretions of _Thalassicolla nucleata_ have been + described in detail in my Monograph (pp. 80, 250, Taf. iii. figs. 2, 3), + and by R. Hertwig in the Histologie der Radiolarien (1876, p. 47, Taf. + iii. figs. 9-13). + + B. The violin-shaped concretions of _Thalassosphaera bifurca_ have been + figured in my Monograph (pp. 80, 261, Taf. xii. fig. 1). + + +76. _The Intracapsular Xanthellae._--The xanthellae, zooxanthellae, or +symbiotic "yellow cells" are found within the central capsule only in the +ACANTHARIA, whilst in other Radiolaria they only occur in the +extracapsulum. They are most frequent in the #Acanthometra#, rarer in the +#Acanthophracta#, but even in the former they are often wanting. Their +number is very variable, but usually small, from ten to thirty in one +capsule. They lie for the most part immediately below the capsule membrane, +in the cortical layer of the endoplasm. The form of the yellow cells is +either spherical or ellipsoidal, often also spheroidal or even lentiform. +The diameter varies from 0.01 to 0.03 mm. They possess a distinct membrane +and an excentric nucleus, and contain numerous yellow pigment-granules in +the endoplasm. This yellow pigment dissolves in mineral acids to form a +green fluid, and in other respects also behaves somewhat differently from +the yellow pigment in the extracapsular yellow cells of the SPUMELLARIA and +NASSELLARIA. In both cases, however, the xanthellae are not integral +portions of the organism, but unicellular algae, living as parasites or +symbiontes in the body. + + A. The yellow cells in the central capsule of the ACANTHARIA were first + observed by Joh. Mueller (L. N. 12, pp. 14, 47). In my Monograph I + described them at greater length, and indicated their differences from + the extracapsular yellow cells of other Radiolaria (L. N. 16, pp. 77, + 86). Since then, R. Hertwig has demonstrated their cellular nature (L. N. + 33, pp. 12, 113), and still more recently {xlvi}Brandt has given further + accurate information regarding their occurrence, constitution, and + physiological significance (L. N. 39, ii. Art., p. 235, figs. 62-73). + + +77. _The Endoplasm of the Peripylea._--The intracapsular protoplasm of the +SPUMELLARIA or PERIPYLEA is usually distinguished by a more or less +complete radial arrangement, which does not occur in the same form in other +Radiolaria; it may be regarded as characteristic of this legion, for it +probably occurs in all the species at some period of life or other, and +stands in a direct causal relationship with the typical structure of the +capsule-membrane in all the "PERIPYLEA" (see note A). For as this is +commonly perforated by very numerous pores distributed at equal intervals +over the whole surface of the capsule, and since a communication between +the intra- and extracapsular sarcode takes place through these, the radiate +structure of the endoplasm may be readily explained as due to the influence +of radial currents which take place continuously or intermittently in the +endoplasm. This radiate structure is most obvious when the endoplasm +contains no secondary products or only an insignificant amount of these, +and thus appears colourless and almost homogeneous, or only finely +granular. Under these circumstances, an optical section of the central +capsule usually reveals a distinct radial striation; numerous narrow, +straight, dark streaks alternating regularly with still narrower clear +ones; the latter consist of homogeneous, the former of more or less +granular protoplasm (Pl. 20, fig. 1_a_). Often there may be distinguished +in each darker streak a single straight row of strongly refracting (fat?) +granules, sometimes several such rows. Occasionally the whole endoplasm +becomes divided up into a number of large "radial wedges," club-shaped, +conical or pyramidal masses of granular protoplasm, separated by clear +divisions of hyaline plasma (_e.g._, in _Actissa radiata_, p. 14, where in +the optical section of the central capsule, between the membrane and the +nucleus, twenty-five dark radial wedges of equal size were separated by +thick clear partitions of hyaline protoplasm). In the majority of the +SPUMELLARIA this radial striation is partially or entirely concealed by the +formation of pigment or of other products. Very often it is only visible in +the cortical layer, which lies immediately below the capsule-membrane (Pl. +1, figs. 1, 3). The remarkable "centripetal cones" which characterise the +Thalassicollid genus _Physematium_, and were formerly described as +"centripetal cell-groups," are probably a special development of these +cortical radial wedges; they are conical cortical bodies, regularly +distributed on the inner surface of the membrane of the central capsule, +and disposed with the apex turned towards the centre (see note B). More +rarely than in the cortical layer, a similar radial structure is to be +found in the innermost medullary layer immediately surrounding the nucleus. +Here the endoplasm sometimes breaks up into fine radial threads, which are +anatomically separable and hang down from the free nucleus as thin +processes (see note C). In some cases it is also possible to isolate radial +rods from the cortical layer of teased out central capsules. + + {xlvii}A. The radial structure of the endoplasm was first described in my + Monograph (1862, p. 74), though R. Hertwig (1879, p. 112) was the first + to indicate its typical significance in the case of the PERIPYLEA, and to + demonstrate its causal relation with the radial currents in the central + capsule of this legion. More recent investigations have led me to the + conviction that this phenomenon is more widespread, and often more + strongly developed, than was formerly imagined, and that it is probably + one of the typical characters of all SPUMELLARIA (at least of the + Monozoa). + + B. The centripetal cones of _Physematium_, which have hitherto been known + only in these colossal Thalassosphaerida, were fully described in my + Monograph under the name "conical centripetal cell-groups"; by their + first discoverer, A. Schneider (L. N. 13), they were termed "nests," and + compared with the "nests" (central capsules) of the Polycyttaria. In the + _Physematium muelleri_ of the Mediterranean (hitherto only observed by + Schneider and myself at Messina) it appeared as though each centripetal + cone were composed of a group of from three to nine (usually four or + five) slender wedge-shaped cells, whose common centripetal apex was + produced into a radial thread of sarcode (L. N. 16, p. 258, Taf. iii. + fig. 7). Since then (1866) I have observed at Lanzerote, in the Canary + Islands, a nearly related form, which I take to be _Physematium + atlanticum_, Meyen. In this, however, the "centripetal cell-groups" were + wanting, and the whole cortical layer of the endoplasm was cleft into + numerous radial portions, each enclosing a nucleus (probably the + mother-cells of flagellate spores, see p. 35). + + C. The radial fibres of the medullary endoplasm which cling to an + extracted nucleus have been observed by Hertwig in certain #Sphaeroidea# + (_Diplosphaera_, _Arachnosphaera_) (L. N. 33, p. 40). + + +78. _The Endoplasm of the Actipylea._--The intracapsular protoplasm of the +ACANTHARIA or ACTIPYLEA is often distinguished by a partial or complete +radial arrangement like that of the PERIPYLEA, but differing in the number, +size, form, and distribution of the radial portions into which the +endoplasm is differentiated. For since the pores of the capsule membrane +are distributed at equal distances all over the surface in the SPUMELLARIA, +whilst in the ACANTHARIA they are arranged in definite groups, and since +the number and arrangement of the pores has a direct influence upon the +internal currents of the endoplasm, it follows that the radial structure in +the latter legion must be very different from that in the former. In +addition to this there must not be forgotten the important influence which +the early centrogenous formation of the skeletal rods exercises upon the +disposition and growth of the intracapsular structures. Hence the endoplasm +of the ACANTHARIA does not separate into innumerable thin, closely packed +radial wedges or cortical radial rods, but into a small number of large +pyramidal portions between which run the radially disposed heterogeneous +portions of the contents of the capsule, viz., the radial bars of acanthin +and the peculiar intracapsular "axial threads." As a direct consequence of +the regular disposition of these heterogeneous radial portions, which is +often characteristic of the various families of the ACANTHARIA, a +corresponding differentiation of the endoplasm is brought about; it divides +into a number of conical or pyramidal portions (radial pyramids), whose +bases rest upon the capsule-membrane and whose apices are directed towards +the centre of {xlviii}the capsule (the central star of the skeleton). +These radial pyramids are, however, but rarely visible, being usually more +or less concealed by a dark pigment. + + The differentiations of the endoplasm in the central capsule of the + ACTIPYLEA have been but little investigated, but they appear to vary + somewhat in the different groups of this legion. In all ACANTHARIA in + which the twenty radial bars are regularly arranged according to the + Muellerian law (see p. 717) and in which axial threads constant in number + and disposition run between them from the central star to the + capsule-membrane, it obviously follows that the endoplasm must be divided + into more or less distinct radial pyramids, and this must the case + whether these take the form of continuous tracts or of actually separable + portions. The regular polygonal figures, often seen on the surface of the + central capsule (with special distinctness in _Acanthometron elasticum_ + and _Acanthometron pellucidum_) separated by a network of granular + threads, are the bases of such radial pyramids (see Hertwig, L. N. 43, p. + 12, Taf. i. figs. 1-7). + + +79. _The Endoplasm of the Monopylea._--The intracapsular protoplasm of the +NASSELLARIA or MONOPYLEA is distinguished from that of any of the other +three legions by the development of a quite peculiar fibrillar structure, +the axial "pseudopodial cone," which may shortly be termed the "podoconus" +(foot-cone). Since this is in direct correlation with the peculiar +structure of the capsular opening, the large "porochora," which is situated +at the basal pole of the main axis, it is quite as characteristic of the +legion as the latter itself (see note A). The podoconus is primitively a +vertical regular cone whose circular base occupies the horizontal porochora +or "basal porous area" of the central capsule, while its vertical axis +coincides with that of the latter. The apex of the cone, usually somewhat +rounded off, is therefore directed towards the aboral or apical pole of the +central capsule and separated from it by a larger or smaller interval. In +this interval the nucleus originally lies (as in Pl. 51, fig. 13; Pl. 98, +fig. 13); but it is usually displaced subsequently and lies excentrically. +The cone is of very variable height; on an average its vertical height is +about equal to the diameter of its horizontal base; these dimensions are, +however, dependent upon the form of the central capsule; the height being +greater in slender ovoid or conical capsules, and less in depressed +sphaeroidal or discoidal ones, than the diameter of the base. The podoconus +consists of differentiated endoplasm, which becomes more deeply stained by +carmine and offers greater resistance to solvents than the surrounding +finely granular protoplasm. The apex, especially, becomes very intensely +stained. It always exhibits a very characteristic fine but distinct +striation, numerous straight radial lines diverging from the apex of the +cone towards the base. The number of these striae appears to correspond +with that of the vertical rods in the porochora, and each of these latter +stands apparently in direct communication with the basal end of an apical +stria (s 59). These threads are probably differentiated constant +contractile threads of endoplasm, or even myophanes, comparable with the +contractile cortical threads of the CANNOPYLEA and the permanent axial +threads of the ACTIPYLEA. The numerous modifications, {xlix}undergone by +the form and contents of the central capsule in the different groups of +MONOPYLEA, especially those due to the formation of the skeleton, are not +without influence upon the podoconus. The most important divergencies from +the above described primary form are the following:--(1) The vertical axial +cone becomes oblique, its axis inclining in the sagittal plane and +approaching either the dorsal or the ventral wall of the capsule; the cause +of this appears to be usually the excentric development of the growing +nucleus or the formation of a large oil-globule. (2) The smooth mantle of +the podoconus becomes divided by three longitudinal furrows into three +equal prominent ridges, which correspond to three circular lobes in the +porochora; the cause of this basal triradial lobular formation lies +probably in the triradial development of the skeleton in many NASSELLARIA +or in the cortinar structure of the collar septum. (3) The simple podoconus +splits into three or four elongated lobes, which eventually become almost +completely separated and correspond to the lobes of the central capsule, in +the axial wall of which they lie as longitudinally striated bands. The +behaviour of these bands justifies the hypothesis that the podoconus is a +muscular differentiated portion of the endoplasm and is composed of +myophane fibrillae, whose contraction determines the opening of the central +capsule. + + A. The podoconus of the MONOPYLEA was first described by R. Hertwig in + 1879, and recognised as a characteristic component of the central capsule + in the most various groups of this legion (in #Plectoidea#, #Stephoidea#, + #Spyroidea#, and #Cyrtoidea#; see his figures, _loc. cit._, Taf. vii., + viii., and the description, pp. 71, 73, 83, 106). Hertwig called it the + "pseudopodial cone," and regarded it as a conical process of the + capsule-membrane, which is developed from this latter and projects from + the porous area into the interior of the central capsule; "it is + penetrated by fine canals which arise at the apex of the cone, diverge + towards the base, and terminate there in the rods of the pseudopodial + area. The intracapsular protoplasm penetrates at the apex of the + pseudopodial cone into its fine canals, runs along them and emerges from + the rods of the porous area in the form of slender threads" (_loc. cit._, + p. 19). I cannot agree with this view of Hertwig, although I have been + able to confirm the accuracy of his description by my own observations + upon numerous excellently stained and preserved preparations in the + Challenger collection. As I have proved by numerous teased out + preparations, and as Hertwig himself correctly states, "the cone is more + readily detached from the membrane than from the protoplasm, when the + capsule is teased" (_loc. cit._, p. 73). Hence I regard the podoconus not + as a differentiated portion of the capsule-membrane but as endoplasm, and + believe that it is composed of myophanes or "contractile muscular + fibrils" in the same manner as the cortical layer of the CANNOPYLEA. + Probably the contraction of these fibrils serves to raise the opercular + rods and hence to allow the exit of the endoplasm through the pores which + lie between these opercular rhabdillae (compare s 59). + + +80. _The Endoplasm of the Cannopylea._--The intracapsular protoplasm of the +PHAEODARIA or CANNOPYLEA is distinguished from that of the other three +legions by several characteristic peculiarities, which are very important, +since they stand in causal relation to the typical structure of the +capsule-membrane and in particular of its {l}remarkable aperture. In the +case of many and perhaps of all PHAEODARIA the endoplasm is differentiated +into a granular medullary and a thin fibrillar cortical layer, the former +of which usually encloses numerous small vacuoles, while the latter +contains muscular fibrillae. In the voluminous central capsule of large +PHAEODARIA the whole cortical layer of the endoplasm, which lies +immediately below the delicate inner capsule-membrane, sometimes appears +delicately and regularly striated, and most distinctly so under the +apertures, towards the centre of each of which the dark striae are radially +directed (see note A, below). These striae are probably contractile +muscular fibrillae; or "myophanes," by whose contraction the openings are +voluntarily widened. In the Tripylea this fibrillar star is much more +strongly developed under the astropyle (the main opening) than under the +parapylae (or accessory openings); and probably the peculiar radial +structure of the operculum of the former is due to the stronger development +of these radial fibrils (being their impression). In many PHAEODARIA, +indeed, the fine myophane fibrils are only visible under the apertures, +whilst in others they form a continuous fibrillar cortical layer on the +whole inner surface of the inner capsule-membrane; the fine fibrillae run +meridionally from one pole of the main axis to the other; perhaps the whole +central capsule may change its form in consequence of their contractions. +The medullary portion of the endoplasm, which lies below this thin cortical +layer, is usually finely granular in the PHAEODARIA, and permeated by +numerous spherical vacuoles, which are noteworthy from their equal size and +regular distribution. Each clear vacuole usually contains a dark shining +fat-granule, more rarely a group of such granules (see note B). Compare s +60, and Pl. 101, figs. 1-3; Pl. 104, figs. 1, 2; Pl. 111, fig. 2; Pl. 128, +fig. 2, &c. + + A. The fine fibrillae in the cortical layer of the endoplasm were first + described by Hertwig in 1879 (L. N. 33, p. 98, Taf x. figs. 6-10). He + found them, however, only below the three openings in the capsule of the + Tripylea, where they form three stellate groups of fibrils. I find them + very clearly shown, and with especial distinctness, under the astropyle + in most PHAEODARIA of which I have had the opportunity of examining + well-stained and preserved central capsules. In many cases, also, the + striation is not confined to the apertures, but spreads over the whole + cortical layer. Perhaps this constitutes in all PHAEODARIA a thin + myophane-sheet, whose contractile fibrils run from one pole of the main + axis to the other and cause by their contraction changes in the form of + the spheroidal central capsule. + + B. The granular medullary portion of the endoplasm of the PHAEODARIA, + with its numerous clear spherical vacuoles, was first described in my + Monograph (1862), in the case of _Aulacantha_ (p. 263), _Aulosphaera_ (p. + 359), and _Coelodendrum_ (p. 361) as a "finely granular, mucous substance + (intracapsular sarcode), packed more or less closely with clear spherical + vesicles from 0.005 to 0.015 mm. in diameter, each of which contains one + or two, rarely three, dark shining granules." That these clear spheres + are true vacuoles was first clearly proved by Hertwig (L. N. 33, p. 98). + As a rule all the vacuoles of the same central capsule are of equal size + (generally from 0.008 to 0.012 mm. in diameter), and are distributed at + equal intervals throughout the finely granular endoplasm. + + + +{li}CHAPTER III.--THE EXTRACAPSULUM. + +(ss 81-100). + +81. _The Components of the Extracapsulum._--The extracapsulum or +extracapsular malacoma, under which name are included all those parts of +the soft body which lie outside the central capsule, consists of the +following constant, and important constituents:--(1) The _calymma_ or +extracapsular jelly-veil; (2) the _sarcomatrix_ or layer of exoplasm +immediately surrounding the membrane of the central capsule; (3) the +_sarcodictyum_ or network of exoplasm, covering the surface of the calymma; +(4) the _pseudopodia_ or radial fibres of exoplasm, which may again be +subdivided into intracalymmar pseudopodia, uniting the sarcomatrix and +sarcodictyum, and extracalymmar pseudopodia, radiating freely into the +water outside the calymma. + + +82. _The Calymma._--The calymma or extracapsular jelly-veil of the +Radiolaria is always the most voluminous portion of the extracapsulum, and +in spite of its simple structureless constitution is of great morphological +and physiological importance. In all Radiolaria this gelatinous mantle +completely surrounds the central capsule, but is separated from its outer +surface by a continuous, though thin, layer of exoplasm, the sarcomatrix. +The pseudopodia radiating from the latter pierce the calymma, form the +sarcodictyum at its surface, and radiate from its nodal points freely into +the surrounding water. The calymma is rarely visible in living freshly +captured Radiolaria, examined in sea-water, for its gelatinous substance is +perfectly hyaline, colourless and pellucid, and possesses the same +refractive index as sea-water; but when the object is removed from this +fluid and transferred to carmine solution or some other colouring matter, +the extent and figure of the calymma become apparent, for the staining +fluid does not at first penetrate into the gelatinous material. When this +has taken place, however (after a longer or shorter time), and the +gelatinous material has become coloured, its form and size may be observed +by the converse experiment; the object is transferred once more to water +and the outlines of the calymma become as clear as those of the central +capsule. The same is the case with dead specimens in which the sticky +surface of the calymma has become covered with dust. + + The jelly-veil of the Radiolaria was recognised even by the earliest + observers of the group, Meyen (1834), and Huxley (1851), and compared + with that of the Palmellaria; the former noticed it in _Physematium_ and + _Sphaerozoum_ (L. N. 1, p. 283), and the latter in _Thalassicolla_ and + _Collosphaera_ (L. N. 5, p. 433). In all these SPUMELLARIA, both in the + monozootic _Thalassicolla_ and in the polyzootic _Sphaerozoum_ and + _Collosphaera_, the calymma is very voluminous and filled with large + alveoli. Meyen called them "muco-gelatinous masses, in the interior of + which are contained small equal-sized vesicles"; Huxley likewise found + clear vesicles in the jelly and compared them with Dujardin's vacuoles. + Johannes Mueller observed the jelly-veil in many different Radiolaria, in + particular in the #Acanthometra#, first discovered by him, but + erroneously believed that it only originated {lii}after death by + liquefaction of the sarcode (L. N. 12, p. 6). This mistake is, however, + easy to understand, since in living Radiolaria the calymma is usually + invisible on account of its perfect transparency, whilst in dead + specimens it is usually quite distinct on account of the dust clinging to + its adhesive surface. I myself believed that the formation of the + voluminous hyaline jelly-veil was only partially due to liquefaction + after death, but that it was to some extent present in the living + organism and that it might vanish and subsequently reappear by means of + imbibition (L. N. 16, pp. 109, 110). R. Hertwig was the first to + demonstrate, in 1879, that the jelly-veil is constantly present in living + Radiolaria, that it forms the basis of the extracapsular malacoma and + surrounds the central capsule as a second protective sheath (L. N. 33, p. + 114). + + +83. _The Structure of the Calymma._--The extracapsular jelly-veil appears +structureless in most Radiolaria, inasmuch as it represents a homogeneous +pellucid excretion of the exoplasm and contains neither fibres nor other +formed structures. In some groups, however, definite structural characters +become secondarily developed. The most common and striking of these is the +formation of alveoles, which takes place in the extracapsulum (see s 86). +In consequence of this the calymma assumes a remarkable frothy consistency +and appears to be composed of large, clear, thin-walled vesicles; this is +especially the case in the #Collodaria# (#Colloidea#, Pls. 1, 3, and +#Beloidea#, Pls. 2, 4), and in many large PHAEODARIA, especially among the +#Phaeocystina# (Phaeodinida and Cannorrhaphida, Pl. 101, and Aulacanthida, +Pls. 102-104). More rarely the calymma is not permeated by vacuoles, but +there appear in it fine striae parallel to the surface as though it were +composed of thin concentric laminae like an onion; perhaps these are the +expressions of a different quantity of water in the various layers. In the +calymma of many Radiolaria thin, straight, radial lines are to be seen, +which are probably pseudopodia, and not to be attributed to any structural +modification, or they may be slender canals which serve for the exit of the +pseudopodia. On the outer surface of the calymma of different Radiolaria, +and especially in the ACANTHARIA, a peculiar network of fibres is to be +found, composed of polygonal meshes, like elastic fibres, probably due to a +local thickening of the jelly. These polygonal meshes are often very +regularly distributed between the radial spines of the #Acanthometra#, and +stand in a definite relation to them. The fibres which form the meshes are +often rather strong, resembling elastic fibres, as above-mentioned, and +either simple or composed of bundles of very fine fibrillae (L. N. 33, p. +15, Taf. i. fig. 1, Taf. ii. fig. 4). + + +84. _The Consistency of the Calymma._--The gelatinous material of which the +calymma of the Radiolaria consists is a pellucid mass, rich in water and +usually quite hyaline and structureless; its consistency is very variable. +In the majority of the Radiolaria it may perhaps be about equal to that of +the jelly which composes the umbrella of most Medusae; but as in these +latter it may vary between very wide extremes, constituting on the one hand +a very soft jelly-mantle, offering but little {liii}resistance to +mechanical influences and almost disintegrating under the eyes of the +observer, and on the other hand forming a firm gelatinous shell, comparable +to cartilage in hardness, elasticity, and power of mechanical resistance. +In many Radiolaria of large dimensions with an alveolar calymma (especially +in numerous #Collodaria# and PHAEODARIA) this may be split by means of +dissecting needles and the central capsule extracted like the stone from a +cherry, and then it is easy to ascertain that the firmness and elasticity +of this jelly-veil are not less than those of a cherry. The different +degrees of consistency in the various Radiolaria may be dependent either +upon the relative amount of water which they contain, or upon qualitative +or quantitative variations in the organic substance of which the jelly +consists. Great importance is to be attached to the considerable +consistency of the calymma, because it furnishes the indispensable +groundwork for the deposition of many parts of the skeleton and +particularly of the lattice-shells. + + +85. _The Primary and Secondary Calymma._--In most Radiolaria the external +form and volume of the calymma are different at different stages of growth, +and this difference is mainly dependent upon the development of the +skeleton. Hence it is advisable to distinguish in general the primary from +the secondary calymma. The _primary calymma_ is in the great majority of +Radiolaria a perfect sphere, in the middle of which lies the concentric +central capsule; on the surface of this gelatinous plate the primary +spherical lattice-shell is secreted in most SPUMELLARIA and +#Acanthophracta#, as well as in those PHAEODARIA which possess a spherical +shell; in the remaining PHAEODARIA also and in the NASSELLARIA, where the +lattice-shell is not spherical but monaxon, it is secreted on the surface +of the primary calymma. This takes place at a definite time, very important +in the development of the Radiolarian, which for the sake of brevity we +shall term the "_lorication-period_." Since the firm surface of the primary +calymma furnishes the necessary foundation for the deposition of the +primary lattice-shell, it is of the greatest mechanical significance in all +shell-bearing Radiolaria. The _secondary calymma_ arises only after the +lorication-period by further growth of the primitive jelly-mantle and in +the fully developed Radiolarian usually encloses wholly or partially the +external parts of the skeleton, in consequence of which it assumes the most +various forms. Very often the secondary calymma is polyhedral, being +stretched between the radial spines of the skeleton, the distal ends of the +latter then forming the fixed points of the gelatinous polyhedron. + + +86. _The Extracapsular Vacuoles and Alveoles._--The calymma of the +Radiolaria usually appears completely homogeneous and hyaline without any +structure; sometimes it encloses numerous clear vesicles, vacuoles or +alveoles, and then assumes a frothy appearance, the expression of a more or +less distinct alveolar structure. {liv}The clear vesicles to which this is +due are either spherical, or polyhedral from mutual pressure, and like the +similar ones in the central capsule may be divided into membraneless +vacuoles and vesicular alveoles. The _vacuoles_ are simple drops of fluid, +without a special envelope, and immediately surrounded by the gelatinous +substance of the calymma, in which they appear as simple cavities. The +_alveoles_ on the contrary are true vesicles, with a thin envelope, which +encloses a drop of fluid or a globule of jelly; in the latter case its +contents are different in refracting power and amount of contained water +from the substance of the surrounding calymma. A sharp boundary between the +membraneless vacuoles and the vesicular alveoles cannot be drawn in the +case of the extracapsular hyaline spheres any more than in the +intracapsular; the envelope of the alveoles is sometimes very distinct and +even anatomically separable, whilst at other times it is very thin and +scarcely recognisable; it may occasionally arise and disappear within a +very short time (see note A). There is no doubt that in the calymma as in +the central capsule the vesicular alveoles are secondary products, which +have arisen from the vacuoles by the secretion of an enveloping membrane. +This membrane is either a delicate sheath of exoplasm, or a firmer and more +resistant skin, distinct from the exoplasm, and probably an excretion from +it (_e.g._, Pl. 4, figs. 2, 3). In many cases the outer surface even of the +vacuoles is covered by a network of pseudopodia, which form a sarcoplegma +similar to a fenestrated alveolar membrane. The colourless pellucid fluid +in the vacuoles and alveoles is usually simple sea-water, more rarely it +contains a small quantity of albumen ("albumen-spheres") or jelly +("gelatinous spheres"). The size of these spheres is very variable. Quite +small vacuoles may be found in the calymma of many Radiolaria. Large +vacuoles, on the other hand, producing the appearance of an alveolar +structure, are confined to but few groups, to a part of the SPUMELLARIA +(#Colloidea#, #Beloidea#, and a few #Sphaeroidea#), and to the +#Phaeocystina# (PHAEODARIA with incomplete skeleton); besides they occur +only rarely in individual genera, _e.g._, _Nassella_ among the skeletonless +NASSELLARIA. Since the volume of the calymma is much increased by the +development of vacuoles, and the power of mechanical resistance is at the +same time much increased, the fact is explained that the vacuoles occur +mainly in Radiolaria which have no skeleton or only an incomplete one (see +note B). Among the monozootic #Collodaria# the alveolar structure is +especially well developed in the following genera; _Thalassicolla_ (Pl. 1, +figs. 4, 5), _Thalassophysa_, _Thalassoplancta_, _Lampoxanthium_ (Pl. 2, +figs. 1, 2); among the PHAEODARIA in most genera of the Phaeodinida, +Cannorrhaphida and Aulacanthida (Pls. 101-104), and probably also in other +voluminous PHAEODARIA (_e.g._, #Phaeosphaeria#). The alveoles or vacuoles +in the calymma of these large Radiolaria lie usually in several layers, one +above another, and increase in size from within outwards. The Polycyttaria +or social Radiolaria (the three families Collozoida, Sphaerozoida and +Collosphaerida) without exception have an alveolar structure, and the +special form of {lv}their colonies or coenobia is to a great extent +determined by the development, number, size and arrangement of the alveoles +in their calymma (compare Pls. 3-8). In these cases there is not +unfrequently developed a large central alveole (see note C) whose thickened +wall encloses a globe of jelly and serves as the central support of the +whole colony (Pl. 5, fig. 1). Still more striking, however, is the +arrangement of certain Polycyttaria, where each individual of the colony +(or each central capsule with its calymma) is enclosed in a large alveole, +whose firm wall often attains considerable thickness (Pl. 4, figs. 2, 3). +The whole colony then appears as an aggregate of numerous cells, each of +which possesses two envelopes, the inner central capsule and the outer +alveolar membrane; between these lies in the Collosphaerida the siliceous +lattice-shell (Pl. 6, fig. 2). These pericapsular alveoles may be regarded +as an outer cell-wall more correctly than the membrane of the central +capsule itself, but the arrangement may also be compared to the temporary +encystation of other Protista (see note D). + + A. The extracapsular vacuoles in the calymma were first observed in 1851 + by Huxley, in _Thalassicolla_ and _Sphaerozoum_, and compared with + Dujardin's sarcode vacuoles (L. N. 5). Afterwards J. Mueller noticed that + generally these "large clear vesicles are covered by a fine membrane," + and hence he called them "alveoles" (L. N. 12, pp. 3, 7, &c.). In my + Monograph I have described them more in detail as "extracapsular + alveoles" (1862, p. 88, Tafs. i.-iii. xxxii.-xxxv.). Ever since then the + point has been debated whether these clear spaces are simple vacuoles in + the sense of Huxley or vesicular alveoles as stated by J. Mueller. This + contention is unnecessary, for both varieties are present, and often no + sharp line can be drawn between them. R. Hertwig has recently come to the + conclusion that they are as a rule "membraneless vacuoles," but that they + "sometimes become surrounded by a special envelope" (L. N. 33, p. 31). He + even succeeded "in extracting from a _Collosphaera_ the large vesicle + which lies in the centre of many colonies and removing its covering of + central capsules and jelly." + + B. The _mechanical importance_ of the alveolar structure, which certainly + increases the elasticity and mechanical resistance of the voluminous + calymma, has not yet been sufficiently realised; in the case of those + Radiolaria which have no skeleton, or at all events no lattice-shell, it + may take the place of this as a protective envelope. Furthermore, by + taking in and giving out water it may discharge a hydrostatic function, + causing the organism to rise or sink in the water. + + C. The _large central alveole_ found in the colonies of many Polycyttaria + (especially Collosphaerida) and first described in my Monograph (Taf. + xxxiv. fig. 1), has since then been observed by Hertwig, Buetschli, and + other investigators, and recognised as the "central support of the whole + colony, surrounded by a delicate membrane" (compare L. N. 33, p. 31, and + L. N. 41, p. 436). In a colony of _Trypanosphaera transformata_ (Pl. 5, + fig. 1), which I observed living while in Ceylon in 1881, the membrane of + the large central alveole was surrounded by a firm network of + sarcoplegma, and could be mechanically isolated from the central + jelly-sphere which it enclosed. + + D. The _pericapsular alveoles_, figured in Pl. 4, figs. 2, 3, from a + _Sphaerozoum_, and in Pl. 6, fig. 2, from a _Siphonosphaera_, were very + well preserved in some preparations in the Challenger collection; perhaps + their development coincides with the formation of spores, and may be + regarded as an encystation. + + +{lvi}87. _The Extracapsular Fat-Globules._--Fat is probably as widely +distributed in the exoplasm as in the endoplasm of the Radiolaria; a +considerable proportion of the small, dark, highly refractive granules +appear to consist of fat; most likely they are for the most part direct +products of metastasis. These widely-spread granules, which are sometimes +coloured, and which by their passive motion produce the phenomenon of +granular circulation in the exoplasm, are not the only fatty structures in +the extracapsulum; larger globules sometimes occur. In certain large +#Collodaria# (_e.g._, _Thalassicolla melacapsa_, Pl. 1, fig. 5; +_Thalassophysa sanguinolenta_, &c.) radial series of oil-globules are found +in the calymma, especially in its proximal portion; in others the central +capsule is surrounded by a layer of oil-globules (situated in the +sarcomatrix). In the PHAEODARIA a part of the phaeodium appears to consist +of fat-globules. + + +88. _The Extracapsular Pigment._--The formation of colouring matters in the +extracapsulum is on the whole rare in the Radiolaria, apart from the +"yellow cells" (see s 91) and from the peculiar phaeodium of the +PHAEODARIA, which will be separately treated of in the next paragraph. +Considerable masses of extracapsular pigment, usually black or blue, rarely +brown or red, are found only in a few Radiolaria belonging to the first +three legions; most often in the SPUMELLARIA. Some large #Collodaria#, +_e.g._, the common _Thalassicolla nucleata_ and a few other species of this +genus (Pl. 1, fig. 4), are characterised by a rich deposit of black or blue +pigment in the sarcomatrix and in the proximal portion of the calymma. +Brown pigment is deposited in the calymma of many #Sphaeroidea# and +#Discoidea#, as well as of some NASSELLARIA (_Cystidium_, _Tridictyopus_, +&c.). In a part of the ACANTHARIA red pigment granules are thickly strewn +in the sarcoplegma and pass along the free pseudopodia, as for example in +_Actinelius purpureus_ and _Acanthostaurus purpurascens_. The composition +and significance of these extracapsular pigments are not completely known. + + On the extracapsular pigment of _Thalassicolla nucleata_, compare my + Monograph, pp. 87, 251. On the red extracapsular pigment-granules of the + ACANTHARIA, see L. N. 19, pp. 345, 364, &c. + + +89. _The Phaeodium of the Phaeodaria._--The PHAEODARIA, which are +distinguished from the other three legions of Radiolaria by the double +membrane of the central capsule, and the peculiar structure of the +main-opening (astropyle), differ also in other points, the most important +of which is the constant presence of a voluminous mass of extracapsular +pigment. This possesses a peculiar constitution and special significance, +and is not to be confounded with the extracapsular pigment-granules of +other Radiolaria (_e.g._, _Thalassicolla_), and hence it has been +distinguished by the name "Phaeodium," and the individual granules which +compose it as "Phaeodella" (see note A). The phaeodium is always excentric +in position relatively to the central capsule, of which it {lvii}surrounds +the oral half in the form of a voluminous concavo-convex cap, hiding the +astropyle at its basal pole so completely that the latter is rarely visible +until the phaeodium has been removed (Pls. 99-104; Pl. 115, fig. 8; Pl. +123, &c.). The central capsule is generally almost completely embedded in +the phaeodium, so that only its aboral pole (with the two parapylae in the +TRIPYLEA) projects. In the #Phaeogromia#, in which the lattice-shell +possesses a special opening and the central capsule lies excentrically in +the aboral position of its interior, the phaeodium occupies the oral +aspect, between the capsule and the aperture (Pls. 99, 100, 118-120, &c.). +In the peculiar family Coelographida (Pls. 126-128) a special receptacle +(galea with its rhinocanna) for the phaeodium is developed outside the +bivalve shell, within which the central capsule lies. The proboscis, which +in all PHAEODARIA arises from the centre of the astropyle, lies in the +vertical axis of the phaeodium and is entirely surrounded by it. The volume +of the phaeodium in the majority of the PHAEODARIA may be said to be about +as great as that of the central capsule, although in some species it is +considerably larger. Its colour is always dark, usually between green and +brown, commonly olive-green or blackish-brown, rarely reddish-brown or +black. The phaeodellae or pigment-granules which make up the greater part +of the phaeodium (see note B) are irregular in form and unequal in size and +show no definite structure; usually they are spherical or ellipsoidal, and +exhibit fine parallel striae which run transversely or obliquely (Pl. 101, +fig. 3, 6, 10; Pl. 103, fig. 1, &c.). Between the larger granules is +usually found a thick dust-like mass of innumerable very small grains. The +physiological significance of this peculiar phaeodium is still unknown, but +is probably considerable, judging from its large size and especially from +its constant topographical relation to the astropyle; the latter +consideration would lead to the supposition that it plays an important part +in the nutrition and metastasis of the PHAEODARIA (see note C). + + A. The phaeodium of _Aulacantha_, _Thalassoplancta_, and _Coelodendrum_ + was first described in 1862, in my Monograph, as an excentric + extracapsular mass of pigment of blackish-brown or olive-green colour + (pp. 87, 262, 264, 361, Taf. ii. iii. xxxii.). Since then John Murray, + who investigated many living PHAEODARIA during the Challenger expedition, + has shown its general distribution in this legion (Proc. Roy. Soc. Lond., + vol. xxiv. p. 536, 1876). From the constancy of its presence I gave the + legion the name PHAEODARIA in 1879 (L. N. 34). + + B. With regard to the special composition of the phaeodium and the + constitution of the phaeodellae, see the general description of the + PHAEODARIA, pp. 1533-1537. + + C. Perhaps the phaeodellae are to some extent symbiontes with the + PHAEODARIA; the xanthellae present in most other Radiolaria are absent in + this legion. + + +90. _The Extracapsular Xanthellae._--Xanthellae or Zooxanthellae, symbiotic +"yellow cells," are very commonly found in the extracapsulum of the +Radiolaria, especially in many SPUMELLARIA and NASSELLARIA; whilst in the +ACANTHARIA similar yellow cells usually only occur within the central +capsule, and in the PHAEODARIA their {lviii}presence has not been certainly +demonstrated. The extracapsular Xanthellae are found most abundantly in the +#Collodaria#, both in the monozootic Thalassicollida and in the polyzootic +Sphaerozoida. They occur in smaller numbers in the #Sphaerellaria#, and in +many divisions of the latter they seem to be entirely absent. Also it +sometimes happens that, though present in large numbers in some +SPUMELLARIA, they are entirely absent in others nearly related to them; +indeed, this has also been observed in the case of different individuals of +the same species. This fact alone is sufficient to show that the Xanthellae +are not an integral part of the Radiolarian organism (as was formerly +believed) but parasites or more correctly symbiontes, which live as +inhabitants of the calymma. More recent investigations have shown, that +besides the yellow pigment-grains they contain starch or an amyloid +substance, that is to say, vegetable reserve materials, that their thin +envelope contains cellulose, and that their yellow colouring-matter +resembles chlorophyll and is related to that of the Diatomaceae +("Diatomin"). Hence they are now generally regarded as unicellular Algae, +nearly related to those which occur as symbiontes in other marine animals +(_Exuviella_, &c.). The starch, which they develop with the formation of +oxygen, may serve as nutriment to the Radiolaria, while the carbonic acid +yielded by the latter is also beneficial to the Xanthellae. The form of the +Xanthellae is usually spherical and elliptical, often also sphaeroidal or +discoidal. Their diameter is usually between 0.008 and 0.012 mm., rarely +more or less. The differences exhibited by Xanthellae which live in +different groups of Radiolaria demand further investigation, which will +perhaps lead to the establishment of several species of the genus +_Zooxanthella_. At present _Zooxanthella extracapsularis_, in the calymma +of SPUMELLARIA and NASSELLARIA, may be clearly distinguished from +_Zooxanthella intracapsularis_, in the central capsule of the ACANTHARIA. + + The "yellow cells" were first described in 1851 by Huxley, in the + #Collodaria#, and afterwards by J. Mueller (1858) in many SPUMELLARIA and + NASSELLARIA. In my Monograph (1862, pp. 84-87) I gave a detailed account + of their structure and increase by division, and laid special emphasis on + the fact that they are the only elements in the Radiolarian organism + which "are _undoubtedly cells_ in the strict histological sense of the + word." Afterwards, in my Beitraege zur Plastiden-Theorie, I showed the + constant presence of "starch in the yellow cells of the Radiolaria" + (1870, L. N. 21). Shortly afterwards Cienkowski observed that the yellow + cells live independently and reproduce themselves after the death of the + Radiolaria, and in consequence first put forth the hypothesis that they + do not belong to the Radiolarian organism, but that they are unicellular + Algae parasitic upon it (1871, L. N. 22). This view was ten years later + more fully established by Karl Brandt, and elucidated by comparison with + the symbiosis of the gonidia of Algae, and the hyphae of Fungi in the + formation of Lichens, which had in the meantime become known (1881, L. N. + 38). Brandt gave this unicellular yellow Alga the name _Zooxanthella + nutricola_, and afterwards gave fuller details regarding its remarkable + vital relations (L. N. 39). Patrick Geddes, who named it _Philozoon_, + supplemented this account and showed experimentally that it gives off + oxygen under the influence of sun-light (1882, L. N. 42, 43). In + consequence {lix}of this there is no doubt that all Xanthellae (the + _Zooxanthella extracapsularis_ of SPUMELLARIA and NASSELLARIA, and the + _Zooxanthella intracapsularis_ of the ACANTHARIA, and possibly also the + _Zooxanthella phaeodaris_ of the PHAEODARIA) do not originally belong to + the Radiolarian organism, as was believed up to the time of Cienkowski, + but penetrate actively into it from without, or are taken in passively by + means of the pseudopodia. In any case their symbiosis, when they are + associated with the Radiolarian cell in large numbers, may be of great + advantage to both parties, since the metastasis of the Xanthella is + vegetable, that of the Radiolarian animal in character. In any case their + symbiosis is to a large extent accidental, by no means as necessary as in + the case of the Lichens. See on these points in addition to Brandt and + Geddes (_loc. cit._) also Geza Enz, Das Consortial-Verhaeltniss von Algen + und Thieren, Biol. Centralbl., Bd. ii. No. 15, 1883, Oskar Hertwig, Die + Symbiose oder das Genossenschaftsleben im Thierreich, Jena, 1883, and + Buetschli, Die Radiolarien, in Bronn's Klass. u. Ord. d. Thierreichs, + 1882 (L. N. 41, pp. 456-462). + + +91. _The Exoplasm or Extracapsular Protoplasm._--The extracapsular +protoplasm, which may be shortly termed the "exoplasm" (or ectosarc), is +primitively in all Radiolaria (and especially in their earliest development +stages) the only important constituent of the extracapsulum, besides the +calymma. Although the extracapsular and intracapsular protoplasm of the +Radiolaria are everywhere in direct communication, and although the +openings in the membrane of the central capsule bring about an interchange +between them, still the two portions of sarcode show certain constant and +characteristic differences, which are due to the physiological division of +labour between the central and peripheral parts of the body and their +corresponding morphological differentiation. The extracapsular, like the +intracapsular, protoplasm is originally homogeneous, but may afterwards +become differentiated in various ways, producing the special constituents +of the extracapsulum. Such "external protoplasmic products" are vacuoles, +pigment-bodies, &c. More important, however, are the topographically +different sections into which the exoplasm may be divided according to its +relations to the central capsule and the calymma. In this respect the +following parts may be generally distinguished--(1) the _Sarcomatrix_, or +fundamental layer of the exoplasm, which surrounds the central capsule as a +continuous sheath of sarcode and separates it from the calymma; (2) the +_Sarcoplegma_, an irregular network of the exoplasm, which spreads +throughout the gelatinous material of the calymma; (3) the _Sarcodictyum_ +or network of sarcode on the outer surface of the calymma; and (4) the +_Pseudopodia_, which project outwards from the latter and radiate into the +water. + + +92. _The Sarcomatrix._--The sarcomatrix, being "the fundamental layer of +the pseudopodia" (or "matrix of the exoplasm"), constitutes the proximal +innermost section of the extracapsular sarcode, and in all Radiolaria forms +a thin continuous mucous layer, which covers the whole outer surface of the +central capsule and separates it from the surrounding calymma (see note A, +below). The sarcomatrix communicates internally {lx}through the openings of +the central capsule with the endoplasm, whilst externally the pseudopodia +or mucous threads arise from it, which by their union form the sarcoplegma. +The sarcomatrix is only interrupted in the SPUMELLARIA and ACANTHARIA by +those parts of the skeleton which perforate the membrane of the central +capsule. In all NASSELLARIA and PHAEODARIA, as in the #Collodaria#, it +appears as a perfectly continuous sarcode-envelope of the central capsule. +Its thickness is variable; in general it is most strongly developed in the +SPUMELLARIA and PHAEODARIA, less so in the NASSELLARIA, and is thinnest in +the ACANTHARIA. The thickness seems, however, to vary even in one and the +same individual, the difference depending partly upon the different stages +of development and partly upon nutritional conditions. After abundant +inception of nutriment the thin protoplasmic layer of the matrix is +thickened and turbid, rich in granules and irregular masses, which are +probably due to enclosed but only half-digested food; xanthellae also, as +well as foreign bodies taken up with the nutriment, such as frustules of +Diatoms and shells of smaller Radiolaria, and of pelagic infusoria, larvae, +&c., are often, especially in large individuals, aggregated in considerable +quantities in the matrix. After long fasting, on the contrary, this is poor +in these enclosed bodies and in granules; it then forms a thin colourless +more or less hyaline mucous coating to the central capsule. From a +physiological standpoint the sarcomatrix is to be regarded as the _central +organ of the extracapsulum_, and as of pre-eminent significance. Probably +it is not only the most important organ for the nutrition of the Radiolaria +(especially for digestion and assimilation in particular), but perhaps is +also the central organ of perception. On the other hand the sarcomatrix +belongs to those components of the Radiolarian organism which take no part +in the formation of the skeleton. + + A. The sarcomatrix was first described in my Monograph in 1862 (p. 110) + as the "Mutterboden der Pseudopodien," possessing a pre-eminent + physiological importance. Compare also my paper on the sarcode elements + of the Rhizopoda (Zeitschr. f. wiss. Zool., Bd. xv. p. 342, 1865). + + +93. _The Sarcoplegma._--By the name sarcoplegma, as distinguished from the +remaining extracapsular sarcode, is understood the intracalymmar web of +exoplasm or "ectosarcode network," which ramifies within the gelatinous +mass of the calymma. Internally it is in direct connection with the +continuous sheath (sarcomatrix), which encloses the central capsule, whilst +externally it is in contact with the superficial sarcode network +(sarcodictyum) which surrounds the calymma. The configuration of this +exoplasmic web, which penetrates the jelly-veil in all directions, is +exceedingly variable; in most Radiolaria it is extremely irregular in form, +like the protoplasmic network in the ground-substance of many kinds of +connective tissue. In some groups, however, it assumes a rather regular +shape which it appears to retain (_e.g._, in many ACANTHARIA). It must be +assumed also that in those instances where the consistency {lxi}of the +calymma approaches that of cartilage, the tracks of the exoplasmic threads +remain constant, but accurate observations are wanting as to how far the +configuration of the sarcoplegma is constant or variable in the different +groups, as well as regarding its peculiar behaviour in those Radiolaria +whose calymma is characterised by the formation of vacuoles or alveoles +(see s 86). Usually it envelops the larger alveoles in the form of a +reticulate veil. In many #Collodaria# the exoplasm is aggregated at certain +points of the intracalymmar web, so that large balls or amoeboid bodies +appear to be distributed between the alveoles, _e.g._, in _Thalassophysa +pelagica_ and _Thalassicolla melacapsa_ (Pl. 1, figs. 4, 5). The +sarcoplegma is metamorphosed directly into silex in the Radiolaria +spongiosa, or those genera which possess a spongy cortical skeleton, and +were formerly known as Spongurida; to this category belong the +Spongosphaerida (Pl. 18) and Spongodiscida (Pl. 47) as well as certain +NASSELLARIA and PHAEODARIA. The single siliceous spicules, which are +irregularly interwoven to form the spongy web, are to be regarded as the +silicified threads of the intracalymmar sarcode network. From a +physiological point of view the sarcoplegma is of importance both for the +nutrition and motion of the Radiolaria, since it brings the sarcomatrix and +the sarcodictyum, with the pseudopodia which radiate from it, into direct +communication. + + +94. _The Sarcodictyum._--The sarcodictyum may be defined as the +extracalymmar network of exoplasm, and is a reticular covering which lies +upon the outer surface of the gelatinous calymma. Internally, the +sarcodictyum is in direct communication with the sarcoplegma, or the web of +exoplasmic threads which ramifies in the gelatinous substance of the +calymma; externally, on the other hand, the pseudopodia radiate freely from +it; thus its relation to these is similar to that which the sarcomatrix +bears to the roots of the sarcoplegma. Relations similar to those which +have led to the separation of the primary from the secondary calymma, +induce us to distinguish also a primary and secondary sarcodictyum. The +original or _primary sarcodictyum_ ramifies over the surface of the +original or primary calymma, and like this is of pre-eminent importance in +the formation of the primary lattice-shell; if we regard the surface of the +primary calymma as the indispensable foundation for the deposition of this +latter, then the primary sarcodictyum furnishes the material from which it +is developed: silex in the SPUMELLARIA and NASSELLARIA, a silicate of +carbon in the PHAEODARIA, and acanthin in the ACANTHARIA. It may indeed be +said that the primary lattice-shell of the Radiolaria arises by a direct +chemical metamorphosis of the primary sarcodictyum, by a chemical +precipitation of the dissolved skeletal material (silex, silicate, or +acanthin), which was stored up in the exoplasm of the sarcodictyum. Hence a +deduction from the special conformation of the former to that of the latter +is permissible. The particular form of the primary lattice-sphere with its +regular or irregular meshes is due to the corresponding form of the primary +sarcodictyum; both regular and irregular forms of this {lxii}commonly +occurring. The form of the _regular sarcodictyum_ with circular or regular +polygonal, usually hexagonal, meshes is constantly maintained during the +formation of the regular lattice-shells (_e.g._, Pl. 12, figs. 5-10; Pl. +52, figs. 8-20; Pl. 96, figs. 2-6; Pl. 113, figs. 1-6). The form of the +_irregular sarcodictyum_, on the other hand, with irregular polygonal or +roundish meshes, persists during the development of the irregular +lattice-shells (_e.g._, Pls. 29, 70, 97, 106). All this is true also of the +_secondary sarcodictyum_, or the exoplasmic network which ramifies over the +surface of the secondary calymma. The secondary lattice-shells, which are +deposited on the surface of the latter, retain the configuration of the +secondary sarcodictyum, by the chemical metamorphosis of which they have +originated; this is the case in many SPUMELLARIA which develop several +concentric lattice-shells (Pl. 29), in some NASSELLARIA (Pl. 54, fig. 5), +in the Phractopeltida among the ACANTHARIA (Pl. 133), and in the +double-shelled PHAEODARIA, Cannosphaerida, and part of the Coelodendrida +and Coelographida (Pls. 112, 121, 128). In those Radiolaria which form no +lattice-shell whatever, the conformation of the sarcodictyum is usually +irregular, with meshes of irregular form and unequal size; sometimes, +however, they seem to be very regular, as in many #Acanthometra# (Pl. 129, +fig. 4). + + +95. _The Pseudopodia._--On the whole the pseudopodia or thread-like +processes of the exoplasm exhibit in the Radiolaria the same characteristic +peculiarities as in all true Rhizopoda; they are usually very numerous, +long and thin, flexible and sensitive filaments of sarcode, which show the +peculiar phenomena of granular movement. Their physiological significance +is in several respects very great, for they serve as active organs for the +inception of nutriment, for locomotion, sensation, and the formation of the +skeleton (see note A, below). The presence of a calymma, however, which +distinguishes the Radiolaria from the other Rhizopoda, brings about certain +modifications in the behaviour of the pseudopodia. If in general all the +threads, which arise from the sarcomatrix or fundamental layer and radiate +outwards, be called "pseudopodia," then that part of them which is included +in the gelatinous substance of the calymma and forms the sarcoplegma may be +termed the "collopodia" (or intracalymmar pseudopodia), and the remaining +portion, which passes outwards from the sarcodictyum freely into the water, +may be described as "astropodia" (or extracalymmar pseudopodia). In many +Radiolaria these two portions present some differences in morphological and +physiological respects, and certain distinctions are probably generally +present (see note B). Apart from this universal differentiation in the +different groups of the Radiolaria, specially modified forms of pseudopodia +may be recognised as the axopodia and myxopodia of the ACANTHARIA (see s +95, A), and the sarcode-flagellum of certain SPUMELLARIA (see note C). + + A. The pseudopodia of the Radiolaria have been so fully described in my + Monograph, in 1862, both morphologically and physiologically, that I need + only refer to the account there given {lxiii}(pp. 89-127); for + supplementary observations see R. Hertwig (1879, L. N. 33, p. 117) and + Buetschli (1882, L. N. 41, pp. 437-445). + + B. The _Astropodia_, or free radiating pseudopodia, are in many + Radiolaria more or less clearly distinguishable from the collopodia, + which form the sarcoplegma within the calymma; how far these distinctions + depend upon a permanent differentiation (especially in the ACANTHARIA and + PHAEODARIA) needs further investigation. + + C. The _sarcode-flagellum_ (perhaps better termed _axoflagellum_) was + first described in my Monograph (1862, p. 115) in the case of various + #Discoidea# (Taf. xxviii. figs. 5, 8; Taf. xxx. fig. 1). Hertwig has + given a substantially similar account of the organ in some other + #Discoidea# (L. N. 33, p. 67, Taf. vi. figs. 10, 11); probably this + peculiar structure is confined to the order #Discoidea# among the + SPUMELLARIA, but is widely distributed within its limits. The + axoflagellum is a thick cylindrical thread of sarcode, finely striated + and pointed towards its free end. It always lies in the equatorial plane + of the discoidal body, and always unpaired in one of its axes; in the + triradiate #Discoidea# it is in the axis of the unpaired principal arm + and opposite to it (Pl. 43, fig. 15). In the Ommatodiscida (p. 500, Pl. + 48, figs. 8, 19, 20) the axoflagellum probably passes out through the + peculiar marginal ostium of the shell. Perhaps it is always connected + with the central nucleus by intracapsular axial fibres, and is to be + regarded as a specially differentiated bundle of pseudopodia (or + axopodia?). + + +95A. _The Myxopodia and Axopodia._--The two forms of pseudopodia which we +distinguish as myxopodia and axopodia differ markedly from each other both +morphologically and physiologically. The _myxopodia_, or ordinary free +pseudopodia, which are found in large numbers in all Radiolaria, and +constitute their most important peripheral organs, are simple homogeneous +exoplasmic threads, which arise from the sarcodictyum or extracalymmar +sarcode network, and radiate freely into the water; here they may branch +and combine by anastomosis to form a changeable network, but they never +contain an axial thread. The _axopodia_, on the other hand, are +differentiated pseudopodia, which consist of a firm radial thread, and a +soft covering of exoplasm; they penetrate the whole calymma in a radial +direction and project freely from its surface, and generally (if not +always) they are produced inwards to the middle of the central capsule, +perforating its membrane; their proximal end is lost in a dark central heap +of granules. Such axopodia are at present known with certainty only in the +ACANTHARIA, where they are widely, and perhaps universally, distributed. +Their development in this legion probably stands in direct causal relation +to the peculiar structure of the central capsule and the centrogenous +formation of the skeleton. Since the radial skeletal rods of the +#Acanthometra# possess originally a thin coating of protoplasm, it may be +said that the centrogenous axopodia of this group became differentiated in +two ways, the firm axial threads of one section remaining very thin and +covered by protoplasm, whilst those of the other section became +metamorphosed into radial bars of acanthin. This hypothesis acquires more +probability from the regular distribution and arrangement of the axopodia +in the ACANTHARIA; they usually stand at fixed intervals {lxiv}between the +radial bars, singly or in groups; sometimes their number seems to be not +greater than that of the bars, whilst in other cases a circlet or group of +axopodia corresponds to each radial bar. Perhaps their fine axial thread +consists of acanthin. At all events the axopodia are constant organs +(probably sensory, like the "palpocils") and not retractile like the +movable myxopodia. + + The axial threads in the pseudopodia of the #Acanthometra# were first + discovered by R. Hertwig, who accurately described their peculiar + structure and arrangement (L. N. 33, pp. 16, 117). + + +96. _The Myophriscs of the Acanthometra._--The #Acanthometra# are +characterised by a very peculiar differentiation of the exoplasm, namely, +by the formation of myophriscs or contractile threads from the +sarcodictyum. In most (and perhaps in all) ACANTHARIA of this order each +radial bar is surrounded by a circlet of such contractile threads, which +was first described as a "ciliary corona" (see note A, below). The number +of contractile threads in each circlet usually amounts to from ten to +twenty, rarely being more than thirty and less than eight; it often appears +to be constant in the individual species (see note B). In the living state +the myophriscs are long, thin filaments, the pointed distal end of which is +inserted into the radial bar, whilst the thicker proximal end is attached +to the surface of the calymma, which is elevated round the base of each rod +into the form of a gelatinous cone or skeletal sheath (see note C). +Probably the myophriscs lie on the outer surface of the apical portion of +this gelatinous cone, and are hence to be regarded as exoplasmic threads +differentiated from the sarcodictyum. Sometimes, however (as in +_Acanthochiasma_), they fuse into a contractile membrane and form the +envelope of a cone, whose interior is occupied by a gelatinous papilla of +the calymma. On mechanical irritation the myophriscs contract rapidly and +suddenly, like muscle-fibrillae, becoming at the same time thicker, and +hence are very different from pseudopodia. Their distal point of insertion +being fixed to the firm acanthin rod, they raise by their contraction the +skeletal sheath, to which their bases are attached or in the surface of +which they lie. The result of their contraction is therefore a distention +and increase in volume of the calymma, with which is no doubt connected an +inception of water into the gelatinous mass, and hence a diminution in its +specific gravity. Probably the #Acanthometra# contract their myophriscs +voluntarily when they wish to rise in the water; when these relax the +calymma collapses owing to its elasticity, water is then expelled and the +specific gravity increases. From a physiological point of view, then, the +myophriscs are to be regarded as a hydrostatic apparatus, morphologically +as myophanes or muscular fibrillae, such as also occur in the intracapsular +protoplasm (see ss 77-80). On more violent irritation and after the death +of the #Acanthometra# the myophriscs separate from the radial bars and +remain attached to the distal ends of the conical gelatinous sheaths as +free "ciliary coronas." At the same time, {lxv}they melt into short, thick, +hyaline rods, the so-called "gelatinous cilia." The myophriscs are found +only in the order #Acanthometra#, and are wanting in the #Acanthophracta#, +as well as in the other three legions of Radiolaria. + + A. The "_ciliary coronas_" on the skeletal rods of dead #Acanthometra# + were first described by the discoverer of this order, Johannes Mueller, + and referred to as "the stumps of the contracted, thickened threads" (L. + N. 12, p. 11, Taf. xi.). + + B. The "_number of the gelatinous cilia_" I found constant in certain + species of #Acanthometra#, and stated in my Monograph (L. N. 16, p. 115) + "that here is to be found the first differentiation of the diffuse + sarcode into definite organs of regular definite number, size, and + position, which deserve the name tentacles rather than pseudopodia." + + C. The nature of the myophriscs as fibrillae allied to muscles was first + discovered by R. Hertwig, who described them as "structures of peculiar + nature," under the name of "contractile threads," and pointed out in + detail their histological and physiological peculiarities (L. N. 33, pp. + 16-19, Taf. i.). + + +97. _The Exoplasm of the Peripylea._--The extracapsular protoplasm of the +SPUMELLARIA or PERIPYLEA is in communication with the intracapsular sarcode +by the innumerable fine pores of the capsule-membrane, and like these pores +is evenly distributed over the whole surface. The sarcomatrix which +immediately surrounds the central capsule is moderately strong, and sends +out innumerable long, thin pseudopodia, which probably correspond to the +pores of the membrane. Their number is markedly greater in the SPUMELLARIA +than in the other three legions. The ramifications and communications which +the radiating fibres of the sarcomatrix undergo within the calymma, +apparently present the most manifold variations, so that the sarcoplegma or +intracalymmar network thus formed has very diverse forms. On the surface of +the calymma the exoplasmic threads constitute a variously disposed +sarcodictyum, a regular or irregular exoplasmic network, by the +silicification of which a primary lattice-shell arises in the majority of +the SPUMELLARIA. The free ends of the pseudopodia, which arise from this +extracalymmar network and radiate out into the water, appear in most +SPUMELLARIA to be relatively short, but exceedingly numerous. Specially +modified pseudopodia and axial threads in particular do not seem to occur +in this legion. Perhaps, however, among the latter may be reckoned the +remarkable pseudopodia which combine to form the sarcode flagellum in many +#Discoidea# (and perhaps in other SPUMELLARIA). This axoflagellum is a +particularly strong thread of sarcode, arising from a definite point in the +central capsule; it is cylindrical or slenderly conical in form, much +longer, stronger, and more contractile than the ordinary pseudopodia; it +contracts in a serpentine fashion on mechanical irritation and seems to +originate by the fusion of a bundle of pseudopodia (compare s 95, C). + + +98. _The Exoplasm of the Actipylea._--The extracapsular protoplasm of the +ACANTHARIA or ACTIPYLEA differs in several important respects from that of +other {lxvi}Radiolaria, and appears to undergo more significant +differentiations than that of the three other legions. Since the pores in +the wall of the central capsule are not distributed evenly and at equal +intervals over its whole surface (as in the PERIPYLEA), but rather exhibit +a regular disposition in groups at unequal intervals, the number of +projecting pseudopodia is much less and the law of their arrangement +different from that which obtains in the PERIPYLEA (s 58). In many and +probably in all ACANTHARIA they are divided into two groups, those which +arise from the centre of the capsule and possess firm axial threads, and +those which have not these characters (compare s 95, A). The axopodia, or +stiff pseudopodia with axial threads, arise from the centre of the capsule, +are present in much smaller numbers than the soft and flexible myxopodia, +and are regularly disposed between the radial bars of acanthin, usually so +that they are as far removed from them as possible, _i.e._, in the centre +between each three or four bars; these latter may indeed be regarded as +strongly developed axial threads, which have become changed into acanthin +(s 95, A). The soft myxopodia, or pseudopodia without axial threads, are +much more numerous than the others, and arise from the sarcodictyum or +exoplasmic network which ramifies over the surface of the calymma. Their +number and arrangement seem, however, in many (if not in all) ACANTHARIA to +be regular and not to possess the extraordinary variability seen in the +other three legions. In many #Acanthometra# the sarcodictyum exhibits a +symmetrical conformation, with regular or subregular, polygonal (mostly +hexagonal) meshes, and generally the stronger threads of the sarcodictyum +secrete a firm, homogeneous or fibrillar, striated substance, which forms a +network of ridges on the surface of the calymma. In the #Acanthophracta# +the place of this is taken by the acanthin network of the primary +lattice-shell. The axopodia of the #Acanthometra# are usually about as long +as the radial spines between which they stand; their stiff axial thread is +surrounded by a soft sheath of protoplasm, communicating with the thin +sarcomatrix which surrounds the central capsule. Numerous branches pass +into the calymma from the exoplasmic sheath of the axial threads, and form +by their interweaving a loose sarcoplegma. The most peculiar differentiated +products of the exoplasm of the ACANTHARIA, however, are the myophane +fibrillae of the #Acanthometra#, which have already been described under +the name of myophriscs (s 96). + + +99. _The Exoplasm of the Monopylea._--The extracapsular protoplasm of the +NASSELLARIA or MONOPYLEA arises only from the porochora, or the +intracapsular podoconus, the oral base of which is formed by this porous +area. The pseudopodia or protoplasmic threads which pass through the pores +of the latter, united into a bundle, are not very numerous (in most +NASSELLARIA probably between thirty and ninety), and unite just outside it +to form a thick discoid sarcomatrix; this covers the porochora completely +below, and spreads out in the form of a thin envelope of exoplasm over the +whole {lxvii}surface of the central capsule; at the apical portion of the +latter the sarcomatrix is often so thin that it can only be recognised by +the aid of reagents; it separates the membrane of the central capsule from +the surrounding calymma. The pseudopodia, which penetrate the latter and by +loose anastomoses from a wide-meshed sarcoplegma within it, are usually not +very numerous. The greater part of them radiate in a bunch downwards from +the basal disc of the sarcomatrix, and a smaller number arise from the +thinner envelope which covers the remainder of the central capsule (Pl. 51, +fig. 13; Pl. 65, fig. 1; Pl. 81, fig. 16). On the outer surface of the +calymma the collopodia, which have passed through it, unite to form the +sarcodictyum, and through the silicification of this the primary +lattice-shell arises in the great majority of the NASSELLARIA. From the +surface of the sarcodictyum arise the astropodia, or free pseudopodia which +radiate outwards into the water. Their number in most MONOPYLEA is +relatively small, but their length appears to be very great. + + +100. _The Exoplasm of the Cannopylea._--The extracapsular protoplasm of the +PHAEODARIA or CANNOPYLEA is much better developed as regards volume than in +the other three legions, and is connected with the intracapsular sarcode by +only a few apertures in the capsule-membrane. In most PHAEODARIA three of +these are present, the astropyle or main-opening at the oral pole of the +main axis, and the two lateral parapylae or accessory openings on either +side of the aboral pole (s 60). In several families the latter appear to be +wanting, whilst in others their number is increased; these families have +not yet, however, been observed during life. The protoplasm projects both +from the oral main-opening and from the two aboral accessory openings in +the form of a thick cylindrical rod; the tube into which each opening is +produced in many PHAEODARIA (longer in the case of the astropyle, shorter +in the parapylae) being regarded as an excretion from this protoplasmic +cylinder. The sarcode threads within the tube appear like a bundle of +fibrils, either quite hyaline or finely striated. After issuing from the +mouth of the aperture they pass over into a thick sarcomatrix, which +surrounds the central capsule entirely and separates it from the enclosing +calymma. In the neighbourhood of the basal astropyle the sarcomatrix is +usually swollen into a thick lenticular disc, which is in direct contact +with the peculiar phaeodium of this legion (s 89). The pseudopodia, which +radiate from the sarcomatrix, and form by anastomosis a wide-meshed +sarcoplegma within the calymma, are usually not very numerous in the +PHAEODARIA, but are very strong. Sometimes two stronger bundles of +collopodia may be distinguished at the two poles of the main axis, an oral +bundle (in the direction of the proboscis of the astropyle) and an aboral +bundle (at the opposite pole between the parapylae). The collopodia of the +sarcoplegma unite at the surface of the calymma into a regular or irregular +sarcodictyum, which, in most PHAEODARIA produces by the secretion of a +peculiar silicate the primary lattice-shell. {lxviii}The free astropodia, +which pass outwards from the sarcodictyum into the water, are in most +PHAEODARIA very numerous (Pl. 101, fig. 10). Since, however, only a few +species of this great legion have been observed in a living state, their +pseudopodia require further accurate examination. + + + +CHAPTER IV.--THE SKELETON. + +(ss 101-140). + +101. _The Significance of the Skeleton._--The skeleton of the Radiolaria is +developed in such exceedingly manifold and various shapes, and exhibits at +the same time such wonderful regularity and delicacy in its adjustments, +that in both these respects the present group of Protista excels all other +classes of the organic world. For, in spite of the fact that the +Radiolarian organism always remains merely a single cell, it shows the +potentiality of the highest complexity to which the process of skeleton +formation can be brought by a single cell. All that has been brought to +pass in this direction by single tissue-cells of animals and plants does +not attain the extremely high stage of development of the Radiolaria. Only +very few Rhizopoda of this very rich and varied class fail to exhibit the +power of forming this firm supporting and protecting organ--indeed, only +ten of the seven hundred and thirty-nine genera which are enrolled in the +list of the Challenger collection, namely, six genera of SPUMELLARIA (five +Thalassicollida, _Actissa_, _Thalassolampe_, _Thalassopila_, +_Thalassicolla_, _Thalassophysa_, Pl. 1, and one genus of Collozoida, +_Collozoum_, Pl. 3), and in addition two genera of NASSELLARIA (the +Nassellida, _Cystidium_ and _Nassella_, Pl. 91, fig. 1), and two genera of +PHAEODARIA (the Phaeodinida, _Phaeocolla_ and _Phaeodina_, Pl. 101, figs. +1, 2). These skeletonless forms of Radiolaria are, however, of extreme +interest, since they include the original stem-forms of the whole class as +well as of its four legions. All Radiolaria which form skeletons have +originated from soft and skeletonless stem-forms by adaptation, and that +polyphyletically, for the skeletal types of the four legions have been +developed independently of each other (s 108). + + +102. _The Chemical Peculiarities of the Skeleton._--The chemical +composition of the skeleton shows very marked variations in the different +legions of the Radiolaria. The two legions SPUMELLARIA and NASSELLARIA +(united formerly as "Polycystina") form their skeleton of pure silica (see +note A, below); the legion PHAEODARIA of a silicate of carbon (see note B), +and the ACANTHARIA of a peculiar organic substance--acanthin (see note C). +This explains the well-known fact that the deposits of fossil Radiolaria +(or Polycystine marls) are composed exclusively of the skeletons of +SPUMELLARIA and NASSELLARIA, those of the ACANTHARIA and PHAEODARIA being +entirely absent (in the case of the last group, however, exception must be +made in favour of the Dictyochida, or those PHAEODARIA {lxix}whose skeleton +is made up of isolated scattered tangential siliceous fragments). The +enormous deposits of Radiolarian skeletons in the deep sea of today, which +constitute the Radiolarian ooze, consist, like the fossil Polycystine +marls, almost exclusively of the shells of SPUMELLARIA and NASSELLARIA, +though here the acanthin skeletons of the ACANTHARIA may be present in very +small numbers, and the silicate skeletons of the PHAEODARIA, which offer +more resistance to the solvent action of sea-water, somewhat more +abundantly. Calcareous skeletons do not occur in the Radiolaria (see note +D). + + A. The pure siliceous skeletons of the Polycystina were first recognised + in 1833 by Ehrenberg in chalky marls (L. N. 2, p. 117). Since the two + legions ACANTHARIA and PHAEODARIA were entirely unknown to Ehrenberg, his + name Polycystina has reference only to the SPUMELLARIA and NASSELLARIA. + + B. The silicate skeleton of the PHAEODARIA was formerly taken by me for a + purely siliceous one. When I described the first PHAEODARIA in my + Monograph in 1862, I was only acquainted with five genera and seven + species, whilst the number of PHAEODARIA here described from the + Challenger amounts to eighty-four genera and four hundred and sixty-five + species. In the vast majority of these (though not in all) the skeleton + becomes more or less intensely stained by carmine, and is also more or + less charred at a red heat, in some even becoming of a blackish-brown. In + many PHAEODARIA, furthermore, the hollow skeletal tubes are destroyed by + the continued action of heat. They are also, for the most part, strongly + acted upon, or even destroyed by boiling caustic alkalis, whilst boiling + mineral acids have no effect upon them. The best method of cleaning the + skeletons of PHAEODARIA from their soft parts is to heat them in + concentrated sulphuric acid, and then add a drop of fuming nitric acid; + in this they are not dissolved even on prolonged heating. From these + facts it would appear that the skeletons of the PHAEODARIA consist of a + compound of organic substance and silica, or a "carbonic silicate." The + more intimate composition yet remains to be discovered, as also the + manifold differences which the various families of PHAEODARIA seem to + show in respect of its composition. The small skeletal fragments of the + Dictyochida (the only remains of PHAEODARIA which occur as fossils) + appear to consist of pure silica. + + C. The acanthin skeleton of the ACANTHARIA was first described as such in + my Monograph (1862, pp. 30-32). Johannes Mueller, the discoverer of this + legion, took them for siliceous skeletons and defined the #Acanthometra# + as "Radiolaria without lattice-shell, but with siliceous radial spines" + (L. N. 12, p. 46). I formerly supposed that the acanthin skeletons in + some of the ACANTHARIA were partially or wholly metamorphosed into + siliceous skeletons, but, according to the investigations of R. Hertwig, + this does not appear to be the case; he showed that the skeletons of the + most varied #Acanthometra# and #Acanthophracta# are completely dissolved + under the longer or shorter action of acids, and supposes that in all + ACANTHARIA, without exception, the skeleton is composed of acanthin + (1879, L. N. 33, p. 120). Quite recently Brandt has found that the + acanthin spines dissolve not only in acids, alkalis, and "liquor + conservativus" (as I had shown), but also in solutions of carbonate of + soda (1 per cent.), and even of common salt (10 to 20 per cent.); he + concludes from this that they consist of an albuminoid substance + (vitellin) (L. N. 38, p. 400). I am unable to share this view, for I have + never been able to see some of the most important reactions of albumen in + any of the skeletons which I have examined, such for example as the + xanthoproteic reaction, the red coloration with Millon's test, &c. They + do not become {lxx}yellow either with nitric acid or with iodine. In + dilute mineral acids they dissolve more rapidly than in concentrated. My + usual method of cleansing the skeleton of ACANTHARIA (which has been + practised with the same result on thousands of specimens) consists in + heating the preparation in a small volume of concentrated sulphuric acid + and then adding a drop of fuming nitric acid; all other constituents (the + whole central capsule and the calymma) are thus very rapidly destroyed; + the skeleton remains quite uninjured and withstands the combined action + of the mineral acids for a longer or shorter time, though on prolonged + heating it also is dissolved. I do not therefore regard acanthin as an + albuminous substance, but as one related to chitin. + + D. Calcareous skeletons have not been certainly demonstrated in the + Radiolaria, and probably do not occur. Sir Wyville Thomson in his + Atlantic (1877, L. N. 31, vol. i. p. 233, fig. 51) described under the + name _Calcaromma calcarea_, a Radiolarian which contained scattered in + its calymma numerous calcareous corpuscles "resembling the rowels of + spurs." These are identical with the "toothed bodies, recalling crystal + balls," which Johannes Mueller figured in the Mediterranean + _Thalassicolla morum_ so early as 1858, and compared with the "siliceous + asterisks of _Tethya_" (L. N. 12, p. 28, Taf. vii. figs. 1, 2). I + formerly regarded these peculiar calcareous corpuscles, whose solubility + in mineral acids I had observed, as spicules of a Thalassicollid, and + hence described the species in my Monograph as _Thalassosphaera morum_ + (L. N. 16, p. 260). I have, however, seen reason to change my view, and + am now led to suppose that those peculiar calcareous corpuscles, which + may be named "_Calcastrella_," are not formed by the Radiolarian itself, + but are foreign bodies which have been accidentally incorporated into the + calymma of a Thalassicollid (_Actissa_). These corpuscles occur, often in + large numbers, in many preparations in the Challenger collection, and in + the calymma of other Radiolaria, chiefly #Discoidea#, hence it would + appear that they are foreign bodies taken up by the pseudopodia and + carried into the calymma by the circulation of the sarcode. The + Radiolaria which Sir Wyville Thomson figured as _Calcaromma calcarea_, + and Mueller as _Thalassicolla morum_, I regard as species of _Actissa_ + (see p. 13), perhaps _Actissa radiata_ of the Pacific, and _Actissa + primordialis_ of the Mediterranean (compare the description of the + Thalassosphaerida of the Challenger collection, pp. 30, 31). + + +103. _The Physical Properties of the Skeleton._--The skeletons of all +Radiolaria are characterised pre-eminently by a high degree of _firmness_, +which fits them to serve as protective and supporting apparatus. This is +obvious in the case of the pure siliceous shells of the Polycystina; but +the acanthin framework of the ACANTHARIA also possesses a degree of +stiffness but little inferior, whilst the silicate skeletons of the +PHAEODARIA seem on the whole to be not so firm. The hollow skeletal tubes +of the last-named, which are filled with gelatinous material, are very +brittle on account of the delicacy of their walls. Their _elasticity_ also +is very small, whilst that of the acanthin spines is considerable. The thin +long needles of many ACANTHARIA are very elastic, as are also the +bristle-like siliceous spicules of many SPUMELLARIA. The _refractive power_ +of the skeleton in the various legions is very different, depending upon +the chemical constitution. The siliceous skeleton of the Polycystina +(SPUMELLARIA and NASSELLARIA) and the silicate skeleton of the PHAEODARIA +have the same refractive index as glycerine, and hence become invisible +when mounted in that fluid; they then become visible only on addition of +{lxxi}water, and are clearer in proportion to the quantity of water which +is added. The refractive index of acanthin is, however, very different from +that of glycerine, so that the skeletons of ACANTHARIA are readily visible +when mounted in this fluid. In water, the skeletons of all Radiolaria +appear about equally refractive, as also in Canada balsam. The substance of +the skeleton appears almost entirely hyaline, colourless, and transparent. +Very rarely it is faintly coloured (in some ACANTHARIA). A cloudy opaque +constitution is seen in some PHAEODARIA (especially in the "porcellanous +shells" of Tuscarorida and Circoporida, Pls. 100, 114-117); when dried, +these appear by reflected light milky-white or yellowish-white; the cause +of this opacity lies partly in the peculiar "cement-like structure" of +these porcellanous shells, partly in their fine porosity, and the minute +air-bubbles contained in their thick walls. + + +104. _The Elementary Structure of the Skeleton._--The general constitution +of the skeleton--or more accurately expressed, of the morphological +elements of which the skeleton consists--is of such a nature that it may be +termed structureless. Both the organic acanthin skeletons of the ACANTHARIA +and the silicate skeletons of the PHAEODARIA, as well as the inorganic +siliceous skeletons of the SPUMELLARIA and NASSELLARIA, appear under the +microscope perfectly homogeneous, transparent, colourless, and crystalline. +Only very rarely do they show traces of a concentric striation, which +arises from the deposition of the skeletal substance in layers; as, for +example, the thick spines of some PHAEODARIA (Pls. 105-107, &c.). Some of +the PHAEODARIA, however, form an exception to this rule, inasmuch as their +partially tubular skeletal elements possess a remarkable porcellanous +structure. In the tubular or Cannoid skeleton, which occurs in most +CANNOPYLEA, the lumen of the thin-walled flinty tube is filled with jelly, +and frequently a thin siliceous thread runs in its axis, and is connected +with the wall by transverse threads (ss 127, 139). The elementary structure +of the opaque porcellanous shells, which distinguish the two families +Circoporida (Pls. 114-117) and Tuscarorida (Pl. 100), is quite peculiar. +Numerous fine siliceous spicules lie scattered irregularly in a finely +granular or porous matrix. + + +105. _Complete and Incomplete Lattice-Shells._--In the great majority of +Radiolaria (in all four legions) the skeleton has the form of a delicate +lattice-shell or a receptacle in which the central capsule is enclosed. In +a small minority, however, this is not the case. The skeleton then consists +only of isolated rigid pieces (radial or tangential spicules), or of a +simple ring (sagittal ring of the #Stephoidea#), or of a basal tripod with +or without a loose tissue of trabeculae, &c. (#Plectoidea#); the central +capsule is then not surrounded by a special latticed receptacle, but only +rests upon the skeletal trabeculae. According to these different +arrangements, two principal groups or sublegions may be distinguished in +each legion, of which one set (Cataphracta) are characterised by a complete +{lxxii}lattice-shell, whilst the others (Aphracta) are without it. The +RADIOLARIA APHRACTA, then, or Radiolaria without a complete skeleton, are +the #Collodaria# (p. 9), the #Acanthometra# (p. 725), the #Plectellaria# +(p. 895), and the #Phaeocystina# (p. 1543). On the other hand, the +RADIOLARIA CATAPHRACTA, or Radiolaria with a complete skeleton, are the +#Sphaerellaria# (p. 49), the #Acanthophracta# (p. 791), the #Cyrtellaria# +(p. 1015), and the #Phaeocoscina# (p. 1590). + + Upon this basis the first subdivision of the Radiolaria was made by + Johannes Mueller, who recognised three groups:--"I. _Thalassicolla_, + without receptacle, naked or with spicules; II. _Polycystina_, with a + siliceous receptacle; III. _Acanthometra_, without receptacle, but with + siliceous radial spines" (L. N. 12, p. 16). + + +106. _The Ectolithia and Entolithia (Extracapsular and Intracapsular +Skeletons)._--The relation of the skeleton to the central capsule in the +Radiolaria is very various in many respects; in the first instance two +great groups, _Ectolithia_ and _Entolithia_ (see note A), may be +distinguished topographically by mere external observation; in the former +the skeleton lies entirely outside the central capsule; in the latter, +partially at all events, within it. The _Ectolithia_, with a completely +extracapsular skeleton, include all NASSELLARIA and PHAEODARIA, as well as +a great part of the SPUMELLARIA (all #Collodaria# and the most archaic +forms of #Sphaerellaria#); the _Entolithia_, on the other hand, in which +the skeleton lies partly within, partly without the central capsule, +include all ACANTHARIA and the majority of the SPUMELLARIA (most +#Sphaerellaria#, see note B). + + A. The difference between Ectolithia and Entolithia was applied in my + Monograph in 1862 (p. 222) to separate the Monocyttaria into two main + groups. The arrangement was, however, quite artificial, being contrary to + the natural relations of the larger groups, as was shown seventeen years + later by the discovery of the different structural relations of the + central capsule. + + B. Among the ACANTHARIA, which all possess primitively an intracapsular + and centrogenous skeleton, the remarkable _Cenocapsa_ (Pl. 133, fig. 11), + seems to furnish the single exception; in it the skeleton consists of a + simple spherical shell which encloses the concentric central capsule. The + exception is, however, only apparent; the twenty perspinal pores of the + shell show that they were originally in connection with twenty + centrogenous acanthin spines, and that those have disappeared by + retrograde metamorphosis. + + +107. _Perigenous and Centrogenous Skeletons._--Much more important than the +topographical relation of the skeleton to the central capsule, according to +which the Ectolithia and Entolithia are separated from each other (s 106), +is the original development of the skeleton within or without the central +capsule, which gives rise to the distinction between perigenous and +centrogenous skeletons. _Centrogenous skeletons_ are found only in the +ACANTHARIA, which are further distinguished from all other Radiolaria by +their skeleton being formed of acanthin; in all ACANTHARIA the formation of +the skeleton begins in the middle of the central capsule, from which twenty +(the number is inconstant only in the {lxxiii}small group #Actinelida#) +radial spines are centrifugally developed. The three other legions, on the +contrary, possess on the whole a _perigenous_ skeleton, which _originally_ +develops outside the central capsule and never in its middle. In the +NASSELLARIA and PHAEODARIA the skeleton retains this extracapsular +position, as also in the #Beloidea# and part of the #Sphaerellaria# among +the SPUMELLARIA; in the great majority of the latter, however, the primary +perigenous skeleton is subsequently enveloped by the growing central +capsule, so that it lies partially within it (s 109). + + +108. _Polyphyletic Origin of the Skeleton._--The skeleton of the Radiolaria +has undoubtedly originated polyphyletically, for it is impossible to derive +its manifold varieties from a single ground-form, or to regard them as +modifications of one type. It is much more probable that the different +skeletonless Radiolaria have entered upon different ways of skeleton +formation quite independently of each other. At the outset it is quite +clear that the skeletons of the _four legions have originated independently +of each other_. Further, it is certain that within the legion of the +SPUMELLARIA the Beloid skeletons of the #Collodaria# are not connected with +the Sphaeroid skeletons of the #Sphaerellaria# and the forms derived from +them (see s 109). In the same way the skeletons of the PHAEODARIA are +polyphyletic; probably in this legion the Beloid, Sphaeroid, Cyrtoid, and +Conchoid skeletons have been developed quite independently (see s 112). In +the NASSELLARIA, on the other hand, it is possible that all the skeletal +forms are to be derived monophyletically from a single simple primitive +form (either the sagittal ring or basal tripod?) (see s 111). Still more +probable is it that the ACANTHARIA have arisen monophyletically, for all +the forms of their acanthin skeleton may be derived without violence from +_Actinelius_ (see s 110). + + +109. _The Skeleton of the Spumellaria._--The skeletons of the SPUMELLARIA +or PERIPYLEA consist of silica, and are very different and of independent +origin in the two orders of this legion. The first order, #Collodaria#, +have either no skeleton whatever (#Colloidea#, p. 10, Pls. 1, 3), or their +skeleton is _Beloid_, a loose extracapsular envelope of spicules, +consisting of numerous unconnected portions; the separate parts are usually +disposed tangentially, either as simple or compound siliceous spicules +(#Beloidea#, p. 28, Pls. 2, 4). The second order of SPUMELLARIA, on the +other hand (#Sphaerellaria#, p. 49), develops a siliceous lattice-shell +which consists of a single piece, and is remarkable for the extraordinary +variety of its forms (pp. 50-715, Pls. 5-50). To this order belong not less +than three hundred genera and seventeen hundred species of the Challenger +Radiolaria (that is, about two-fifths of all the genera and species). In +spite of this extreme richness in different forms this large group must be +regarded as _monophyletic_, since all its forms may be quite naturally +derived from a common stem-form, a _simple lattice-sphere_ (_Cenosphaera_, +p. 61, Pl. 2). The twenty-eight families of #Sphaerellaria# may be +distributed in four suborders, among which the #Sphaeroidea# constitute the +{lxxiv}stem-forms, since they retain the original spherical shape (Pls. +5-8, 11-30). In the other three suborders a vertical main axis is +developed, which in #Prunoidea# is longer, in #Discoidea# shorter than the +other axes of the shell. Hence the shell of the #Prunoidea# (p. 284, Pls. +13, _bis_, 17, 39, 40) is ellipsoidal or cylindrical, that of the +#Discoidea#, on the other hand, lenticular or discoidal (p. 402, Pls. +31-38, 41-48). Finally, the shell of the fourth suborder, #Larcoidea#, is +lentelliptical; it has the ground-form of a triaxial ellipsoid, and is +characterised by the possession of three unequal dimensive axes, or three +isopolar axes of different lengths perpendicular to each other (p. 599, +Pls. 9, 10, 49, 50). + + +110. _The Skeleton of the Acantharia._--The skeletons of the ACANTHARIA or +ACTIPYLEA are distinguished from those of all other Radiolaria by two very +important peculiarities; in the first place, they consist not of silica but +of a peculiar organic substance, _Acanthin_, and secondly, their +development is centrogenous, numerous radial spines or acanthin spicules +being formed which are united in the middle of the central capsule. Hence +the ACANTHARIA are the only Radiolaria in which the skeleton originates +from the first in the middle of the central capsule. The number of radial +spines is primitively indefinite, variable, and often considerable (more +than a hundred), but in the great majority it is limited to twenty. In +accordance with this the legion may be divided into two orders, the more +archaic small group Adelacantha, with an indefinite number of spines, and +the more recent group, Icosacantha, which has been developed from them and +possesses twenty regularly disposed spines; of the three hundred and +seventy-two species of ACANTHARIA which have been hitherto described, about +five per cent. belong to the former, about ninety-five per cent. to the +latter division (see note A, below). The numerous genera of Icosacantha may +then be again divided into two suborders, of which the #Acanthonida# (p. +740, Pls. 130-132) produce no complete lattice-shell, and thus agree with +the #Actinelida#, with which they may be united as #Acanthometra# in the +broader sense (or ACANTHARIA without a lattice-shell). The +#Acanthophracta#, on the other hand (p. 791, Pls. 133-140), produce a +complete lattice-shell, usually by means of two opposite or four crossed +transverse processes, which arise from each radial spine and unite with +each other (see note B, below). In most #Acanthophracta# the lattice-shell +remains single; only in the Phractopeltida does it consist of two +concentric lattice-spheres (p. 847, Pl. 133, figs. 1-6). Furthermore, the +whole order #Acanthophracta# may be subdivided into two suborders according +to the different ground-form of the lattice-shell; this remains spherical +in the #Sphaerophracta# (the three families Sphaerocapsida, Dorataspida, +Phractopeltida, Pls. 133-138). On the other hand, it assumes another form +in the #Prunophracta#; it becomes ellipsoidal in the Belonaspida (Pl. 136, +figs. 6-9), discoidal or lentiform in the Hexalaspida (Pl. 139); and +finally takes the shape of a double cone in the Diploconida (Pl. 140). + + {lxxv}A. The group Adelacantha consists only of the suborder + #Actinelida#, with the three families Astrolophida, Litholophida, and + Chiastolida (p. 728, Pl. 129, figs. 1-3); the number of the radial spines + is very different and variable, sometimes only from ten to sixteen, but + usually from thirty to fifty, and often more than one hundred; they are + generally irregularly distributed, and not as in the second main + division. This latter, the Icosacantha, always possesses _twenty_ radial + spines, which are regularly disposed according to a constant law, the + so-called "Muellerian" or "Icosacanthan" law; the twenty spines are + always so placed between the poles of a spineless axis that they form + five zones each of four spines; the four spines of each zone are + equidistant from each other, and also from the same pole, and alternate + with those of the neighbouring zones, so that the whole twenty lie in + four meridian planes, which cut out an angle of 45d (compare pp. 717-722, + Pls. 130-140). In spite of the manifold variations in form which are + developed in the Icosacantha, they may all be derived from a common + stem-form, _Acanthometron_ (p. 742), since the law of distribution of the + twenty spines is constantly inherited. + + B. An exception is found in the peculiar family Sphaerocapsida (p. 797, + Pl. 133, figs. 7-11; Pl. 135, figs. 6-10). Here the shell is composed of + innumerable small, perforated plates, which arise on the surface of the + calymma independently of the spines. + + +111. _The Skeleton of the Nassellaria._--The skeletons of the NASSELLARIA +or MONOPYLEA consist of silica, and are never composed of separate +portions, but constitute always a single continuous piece. The ground-form +is originally monaxon, corresponding to that of the central capsule, with a +constant difference between the two poles of the vertical main axis. The +ground-form is never spherical or polyaxon as in the lattice-shells of the +SPUMELLARIA, and the skeleton never consists of hollow tubes, as in the +PHAEODARIA. The legion NASSELLARIA may be divided into two orders; in the +#Plectellaria# (three suborders #Nassoidea#, #Plectoidea#, #Stephoidea#) +the skeleton does not form a complete lattice-shell; in the #Cyrtellaria#, +on the other hand, which are derived from these, the siliceous skeleton +forms a complete lattice-shell enclosing the central capsule. The number of +forms thus developed is astonishingly great, so that among the NASSELLARIA +no less than two hundred and seventy-four genera and sixteen hundred and +eighty-seven species may be distinguished, almost as many as in the +#Sphaerellaria#. In spite of this great variety of forms the legion +MONOPYLEA is probably monophyletic; at least all the different skeletal +forms may be derived from three elements which are combined in the most +manifold fashion; (1) the _sagittal ring_, a simple siliceous ring, which +lies vertically in the sagittal plane of the body, encircles the central +capsule and comes into contact with it at the basal pole of the main axis +(s 124); (2) the _basal or oral tripod_, composed of three diverging radial +spines, which meet in the middle of the basal pole of the central capsule +(or in the centre of the porochora) (s 125); (3) the _cephalis_, or +lattice-head, a simple ovoid or subspherical lattice-shell, which encloses +the central capsule and stands in connection with it at the basal pole of +its main axis. Any one of these three important structural elements of the +NASSELLARIAN skeleton may possibly be the starting-point {lxxvi}for all the +remaining forms of the MONOPYLEA; the great difficulty in their +phylogenetic derivation lies in the facts that, on the one hand, any one of +the three elements may alone constitute the skeleton, and on the other +hand, in the great majority of the legion, two or three are united together +(compare ss 182-185). + + +112. _The Skeleton of the Phaeodaria._--The skeleton of the PHAEODARIA or +CANNOPYLEA is always extracapsular, usually consists of a silicate of +carbon (more rarely of pure silica), and in the majority of the legion is +composed of hollow cylindrical tubes, whose siliceous wall is very thin, +and whose lumen is filled with gelatinous material (s 127). The manifold +and remarkable skeletal forms occurring in this legion are not +monophyletic, since they cannot be derived from a common stem-form; they +are, on the contrary, polyphyletic, various skeletonless PHAEODARIA +(Phaeodinida) have independently acquired skeletons of different form and +composition. The legion PHAEODARIA can be subdivided into four orders, the +skeletons of which present the following important distinctions:--(1) The +#Phaeocystina# possess only incomplete Beloid skeletons (s 115), composed +of many separate pieces, sometimes tangentially (Cannorrhaphida, Pl. 101), +sometimes radially arranged (Aulacanthida, Pls. 102-105). (2) The +#Phaeosphaeria# form Sphaeroid skeletons (s 116), usually only a simple +lattice-shell without special aperture (Pls. 106-111); two concentric +shells united by radial bars occur only in the Cannosphaerida (Pl. 112). +(3) The #Phaeogromia# are distinguished by the formation of a simple +Cyrtoid skeleton (s 123) resembling that of the Monocyrtida; the +monothalamus lattice-shell is usually ovoid or helmet-shaped, more rarely +polyhedral or almost spherical; a vertical main axis can always be +distinguished, at the basal pole of which is an aperture usually armed with +teeth or spines (Pls. 99, 100, 113-120). (4) The #Phaeoconchia# are +distinguished from all other Radiolaria by the possession of a bivalved +shell like that of the Conchifera; the two valves of this Conchoid skeleton +must be distinguished as dorsal and ventral, as in the Brachiopoda (Pls. +121-128). The fifteen families of PHAEODARIA which are arranged in the four +orders just mentioned, present such great differences among themselves, +that the skeleton must be regarded as probably polyphyletic even within the +limits of each order. + + +113. _Types of Skeletal Formation._--No less than twelve different +principal forms may be distinguished as morphological types of the +formation of the skeleton in the Radiolaria; some of these are peculiar to +a single legion or even to a smaller group; but sometimes the same form +occurs in several legions. Some types occur only in an isolated manner, +independently of the others, but most exist in various combinations with +other types. Of the twelve described below the Conchoid and Cannoid occur +only in the PHAEODARIA; the Plectoid and Circoid only in the NASSELLARIA; +the Astroid only in the ACANTHARIA; the remaining seven types are found in +several legions in the same form and hence are polyphyletic. + + +{lxxvii}114. _The Astroid Skeleton._--Under the name "Astroid" we place the +peculiar star-shaped skeletons of the ACANTHARIA in opposition to those of +all other Radiolaria, for they are separated from them not only +fundamentally by reason of the chemical nature of their substance +(Acanthin, s 102), but also by their centrogenous origin, and the resulting +stellate form (Pls. 129-140). The ACANTHARIA are the only Radiolaria in +which the skeleton arises within the central capsule by the formation of +numerous rays or radial spines of acanthin which project on all sides from +the centre. Originally these are united at this point, their conical or +pyramidal points meeting and being supported one upon another. In the great +majority of ACANTHARIA this loose apposition is constant, so that when the +soft parts are destroyed the skeleton falls to pieces. Only in a few forms +in this legion are the central ends of the spines fused so that the whole +skeleton forms a connected star (_Astrolithium_). The small group +Chiastolida (or Acanthochiasmida) is characterised by the fact that the two +rays which are opposite to one another in each axis unite and form a +diametral bar. The skeleton is almost always composed of twenty radial +spines, which are regularly disposed (Icosacantha), only in the small +primitive group #Actinelida# is the number variable (Adelacantha, s 110). + + +115. _The Beloid Skeleton._--As Beloid or spicular skeletons are grouped +together all those which consist of several disconnected portions; these +always lie outside the central capsule, either within the calymma or on its +surface. Such extracapsular Beloid skeletons are entirely wanting in the +ACANTHARIA and NASSELLARIA; they occur only in the #Beloidea# among the +SPUMELLARIA, and in the #Phaeocystina# among the PHAEODARIA; the individual +Beloid portions of the former are solid, those of the latter hollow. In +both groups the simplest forms of the separate portions are simple +unbranched needles (_Thalassosphaera_, _Thalassoplancta_, _Physematium_, +_Belonozoum_, among the SPUMELLARIA; _Cannobelos_ and _Cannorrhaphis_ among +the PHAEODARIA); usually these spicules are disposed tangentially over the +surface of the calymma. Among the #Beloidea# branched spicules occur more +commonly than these simple ones; they are either stellate (with many rays +united in a centre) or twin-like, with a tangential bar, from each pole of +which two or three (seldom more) radial branches project (Pls. 2, 4). Among +the PHAEODARIA the subfamily Dictyochida is characterised by the annular +shape of its Beloid portions, either simple rings, or hat-shaped or +pyramidal bodies with a latticed cap over the ring (Pl. 101, figs. 3-14; +Pl. 114, figs. 7-13). The family Aulacanthida among the PHAEODARIA, alone +possesses hollow _radial tubes_, which penetrate the whole calymma, and +project distally over its surface, whilst their proximal ends rest upon the +surface of the central capsule. Although in these cases the enclosed +proximal end is always simple, the free distal end develops the most +various processes in adaptation to its prehensile functions (Pls. 102-105). + + +{lxxviii}116. _The Sphaeroid Skeletons or Lattice-Spheres._--The +"lattice-spheres" or sphaeroid skeletons are the simplest and most +primitive forms of lattice shells, and are widely distributed in the three +legions SPUMELLARIA, ACANTHARIA, and PHAEODARIA, whilst they are entirely +wanting in the NASSELLARIA. The round lattice-shell is either a true sphere +in the geometrical sense, or an endospherical polyhedron, _i.e._, a +polyhedron, all whose angles lie in the surface of a sphere (s 25). In +general, _primary_ and _secondary_ lattice-spheres may be distinguished, of +which the former are secreted on the outer surface of the primary, the +latter on that of the secondary calymma (s 85). Furthermore, _simple_ and +_compound_ lattice-spheres may be distinguished, the latter of which +consist of two or more concentric lattice-spheres firmly united by radial +bars; in such cases the innermost lattice-sphere is always to be regarded +as the oldest or primary, all the succeeding ones as secondary, and the +outermost as the youngest (s 129). The simple lattice-spheres are usually +to be regarded as primary; they may, however, occasionally be secondary, in +which case the primary shell, originally enclosed, has been lost by +degeneration (as, for example, in the case of the Aulosphaerida and some +#Sphaerellaria#). + + +117. _The Lattice-Spheres of the Spumellaria._--The lattice-spheres or +Sphaeroid skeletons of the SPUMELLARIA exhibit in spite of their simple +type of structure, an extraordinary variety in the formation of the +lattice-work and radial apophyses, so that in the systematic portion of +this work no less than one hundred and seven genera and six hundred and +fifty species are distinguished; these are united in one suborder, the +#Sphaeroidea# (pp. 50-284, Pls. 5-8, 11-30). It may be divided into two +main divisions, the _Monosphaerida_ with a single primary lattice-sphere +(Pls. 12-14, 21, 26, 27), and _Pliosphaerida_ (or Sphaeroidea concentrica) +whose skeleton consists of two or more concentric lattice-spheres united by +radial bars. The latter are subdivided into Dyosphaerida with two +concentric lattice-spheres (Pls. 16, 19, 20, 22, 28); Triosphaerida, with +three spheres (Pls. 17, 24, 29); Tetrasphaerida, with four (Pls. 23, 30); +Polysphaerida, with five or more (Pls. 15, 23); and Spongosphaerida, with +spongy lattice-spheres (Pls. 18, 25). A special group is made up of the +simple lattice-spheres of the social Collosphaerida (or Sphaeroidea +polyzoa) (Pls. 5-8); these are usually more or less irregular, and +characterised by the development of peculiar tubular processes; the latter +are generally wanting in the Sphaeroidea monozoa, whose lattice-shell is +very regularly formed. This distinction is interesting and important, +inasmuch as the regular lattice-spheres are explained by the independent +development of the free-swimming Monozoa, whilst the irregular spheres are +due to the mutual dependence of the social Polyzoa. + + +118. _The Lattice-Spheres of the Acantharia._--The lattice-shells or +Sphaeroid skeletons of the ACANTHARIA are immediately distinguishable from +those of all other Radiolaria by their centrogenous development and the +central union of the radial spines by which they are supported; the only +exception is furnished by the remarkable genus _Cenocapsa_ {lxxix}(Pl. 133, +fig. 11), in which the radial spines are absent, not primitively, however, +but in consequence of degeneration; for the twenty cross-shaped perspinal +pores, originally due to the twenty radial spines, are still present. In +the most nearly allied genera, _Porocapsa_ (Pl. 133, fig. 7) and +_Cannocapsa_ (Pl. 133, fig. 8), the proximal part of the twenty radial +spines is still present, while their distal portion has degenerated; hence +in this case they do not stand in direct communication with the spherical +shell. On the other hand, this primitive connection persists in the genera +_Astrocapsa_ (Pl. 133, figs. 9, 10), and _Sphaerocapsa_ (Pl. 135, figs. +6-10). The five genera just mentioned form the peculiar family +Sphaerocapsida (pp. 795-802); the spherical shell is in these cases +composed of very numerous small plates disposed like a pavement, each plate +or aglet being perforated by a pore canal; in addition to which there are +twenty larger (perspinal) pores (or twenty cross-shaped groups each of four +aspinal pores) at those important points where primitively the twenty +radial spines penetrate the calymma. This peculiar porous "pavement shell" +has probably been developed (independently of the twenty radial spines) +upon the calymma of the #Acanthonida# (_Acanthonia_, p. 749) by the action +of the sarcodictyum; it has, therefore, quite a different morphological +significance from the spherical lattice-shell of the Dorataspida, which is +composed of tangential apophyses of the twenty Acanthonid spines (pp. +802-847, Pls. 134-138). Each radial spine here forms either two opposite or +four crossed transverse processes, and since their branches spread over the +surface of the spherical calymma and are united suturally at their +extremities, the peculiar lattice-sphere of the Dorataspida arises. This +extensive family is again divided into two subfamilies:--the Diporaspida +(Pls. 137, 138) possess always only two opposite apophyses, and form by the +union of their branches two opposite primary apertures or aspinal meshes. +The Tessaraspida, on the other hand (Pls. 135, 138), have always four +crossed transverse processes, and form by their union four primary aspinal +meshes. From the Diporaspida are probably to be derived the Phractopeltida +(p. 847, Pl. 133, figs. 1-6), the only ACANTHARIA which possess a double +lattice-sphere; their double concentric spherical shell may be compared +with that of the Dyosphaerida. + + +119. _The Lattice-Spheres of the Phaeodaria._--The lattice-spheres or +Sphaeroid skeletons of the PHAEODARIA, which are generally developed quite +regularly, though occasionally in a modified form, fall in the order +#Phaeosphaeria# into two groups of very different structure, each of which +includes two families. The first group (_Phaeosphaeria inarticulata_) +contains the families Orosphaerida (Pls. 106, 107) and Sagosphaerida (Pl. +108); the lattice-work of the former consists of irregular polygonal meshes +and very coarse, partially hollow trabeculae; in the latter, on the other +hand, it consists of triangular meshes and very slender filiform +trabeculae; in both families the whole sphaeroid skeleton forms a single +unsegmented piece as in most #Sphaeroidea#. In the second group of +{lxxx}#Phaeosphaeria# (_Phaeosphaeria articulata_), on the other hand, the +lattice-sphere is segmented in quite a peculiar manner, and composed of +hollow cylindrical tangential tubes, which are separated by astral septa at +the nodal points of the network; this remarkable structure characterises +the two families, Aulosphaerida (Pls. 109-111) and Cannosphaerida (Pl. +112); the segmented lattice-sphere of the former is simple and hollow; +while that of the latter is connected by centripetal radial tubes with a +simple concentric inner shell, which is sometimes solid, sometimes +latticed, and provided with a main-opening corresponding to the astropyle +of the enclosed central capsule. Since in the Aulosphaerida also, hollow +centripetal radial tubes project from the segmented lattice-sphere, it is +possible that they have been derived from the Cannosphaerida by the loss of +the primitive internal shell. A special peculiarity of many #Phaeosphaeria# +(_Oroscena_, _Sagoscena_, _Auloscena_, &c.) consists in the fact that the +whole surface of the lattice-sphere is regularly covered with pyramidal or +tent-shaped prominences (Pl. 106, fig. 4; Pl. 108, fig. 1; Pl. 110, fig. +1). A simple lattice-sphere quite similar to that of most Monosphaerida +also constitutes the skeleton of the Castanellida (Pl. 113), but since it +possesses a special main-opening, it must be referred promorphologically to +the Cyrtoid shells of the #Phaeogromia#. + + +120. _The Prunoid Skeleton or Lattice-Ellipsoid._--The "lattice-ellipsoids" +or Prunoid skeletons have arisen from the lattice-spheres or Sphaeroid +skeletons by more energetic growth and elongation of one axis; this is the +main axis of the body and is probably always vertical; its two poles are +commonly equal. The Prunoid skeleton is either a true ellipsoid in the +geometrical sense or an "endellipsoidal polyhedron" (_i.e._, a polyhedron, +all the angles of which lie in an ellipsoidal surface). By further +elongation of the main axis, the ellipsoidal form passes over into the +cylindrical, the polar surfaces of the cylinder being usually rounded, +rarely truncated. The rich order #Prunoidea# (pp. 284-402) contains +numerous modifications of this form of shell which arise on the one hand by +the formation of transverse constrictions, on the other by the apposition +of concentric secondary shells. In respect of the latter, simple and +compound Prunoid shells can be distinguished as in the case of the +Sphaeroid shells. In the compound Prunoid shells either all the concentric +lattice-shells may be ellipsoidal or the inner may be spherical. More +important differences are found in the transverse annular constrictions, +which give the Prunoid skeleton a segmented appearance; in this respect, +three principal forms may be distinguished (p. 288):--(A) _Monoprunida_, +with unsegmented shell, having no transverse constriction (Pls. 15-17); (B) +_Dyoprunida_, having a shell with two segments and one (equatorial) +transverse constriction (Pl. 39); (C) _Polyprunida_, with three or more +parallel transverse constrictions, by means of which the shell is divided +into four or more segments (Pl. 40). In the same manner as the #Prunoidea# +have arisen from the #Sphaeroidea# among the SPUMELLARIA by greater +{lxxxi}development of the vertical main axis, the ellipsoidal Belonaspida +have arisen from the spherical Dorataspida among the ACANTHARIA (p. 859; +Pl. 136, figs. 6-9; Pl. 139, figs. 8, 9). The main axis of the ellipsoid in +this case is always occupied by the opposite equatorial spines of the +hydrotomical axis (pp. 719, 860). In the legion PHAEODARIA a similar +prolongation of the main axis rarely occurs; it is found, however, in +_Aulatractus_ (Pl. 111, figs. 6, 7), the lattice-shell of this Aulosphaerid +being sometimes truly fusiform, sometimes rather ellipsoidal or even +double-conical. + + +121. _The Discoid Skeletons or Lattice-Discs._--The "lattice-discs" or +Discoid skeletons are characteristic of the SPUMELLARIAN group #Discoidea#, +and have arisen from the lattice-spheres of the #Sphaeroidea# by a less +development of one axis, which is the main axis of the body, and is +probably usually vertical; its two poles are always equal. The Discoid +lattice-shell is either a biconvex lens (with a thin margin), or a plane +disc (a shortened cylinder with thick margin), or some form intermediate +between the two. All Discoid shells show a horizontal median plane or +equatorial plane, by which they are divided into two equal halves, an upper +and lower; the margin of the lens itself is originally the equator. The +main axis, the shortest of all the axes of the shell, stands vertically in +the centre of the equatorial plane. Among the PHAEODARIA Discoid shells +rarely occur (_Aulophacus_), as also among the ACANTHARIA (Hexalaspida). + + +122. _The Larcoid Skeleton or Lentelliptical Lattice-Shell._--The +lentelliptical lattice-shells, which may be shortly designated "Larcoid," +are especially characteristic of the #Larcoidea#, a large order of +SPUMELLARIA (pp. 599-715; Pls. 9, 10, 49, 50). In addition they recur among +the ACANTHARIA, in the small family Hexalaspida (p. 872, Pl. 139), and the +family Diploconida (p. 881, Pl. 140), which is derived from it. These +lentelliptical lattice-shells are all characterised by the clear +differentiation of three unequal, but isopolar dimensive axes, _i.e._, the +three geometrical axes, perpendicular to one another, which determine the +form of the shell, are of unequal length; the two poles of each are, +however, equal. The geometrical ground-form is, therefore, a triaxial +ellipsoid (s 34). In the rich order #Larcoidea# the lentelliptical +lattice-shell shows many variations in its development. + + +123. _The Cyrtoid Skeleton._--Cyrtoid skeletons are those lattice-shells +which possess a vertical main axis with two different poles (Monaxonia +allopola); the upper pole is usually termed the apical, the lower the +basal. Such Cyrtoid shells are characteristic of the great majority of the +NASSELLARIA or MONOPYLEA (and especially of the #Cyrtellaria#); they are +also found in a large division of the PHAEODARIA (the #Phaeogromia#), and +in some SPUMELLARIA. In general the manifold Cyrtoid shells may be divided +into two large groups, those with one and those with several chambers. The +_monothalamous_ Cyrtoid shells are usually ovoid, conical, cap- or +helmet-shaped; their {lxxxii}internal cavity is simple, without +constrictions or septa. Among the NASSELLARIA they occur in the Monocyrtida +(Pls. 51-54, 98), where they have received the name "Cephalis." A form of +shell, essentially the same, is found amongst the PHAEODARIA in the order +#Phaeogromia#, more especially in the Challengerida (Pl. 99), Medusettida +(Pls. 118-120), and Tuscarorida (Pl. 100), many of these latter closely +resembling many Monocyrtida. Such monothalamous Cyrtoid shells occur much +more rarely among the SPUMELLARIA (_e.g._, among the #Prunoidea# in +_Lithapium_, _Lithomespilus_, _Druppatractus_, Pls. 13, 14, &c.). +Polythalamous Cyrtoid shells (Pls. 55-80) occur exclusively in the +NASSELLARIA, and exhibit in this legion an astonishing variety of +structure; they are distinguished from the monothalamous forms by the +development of internal septa, or of annular incomplete diaphragms, which +usually correspond to the external constrictions; their interior is thus +divided into two or more communicating compartments. Among the +polythalamous Cyrtoid shells may be distinguished three principal groups, +the Stichocyrtid, Zygocyrtid, and Polycyrtid. Zygocyrtid shells are +characteristic of the #Spyroidea# (Pls. 84-90), and are distinguished by a +bilobate cephalis (cephalis bilocularis); the median sagittal ring, or a +corresponding constriction, divides the shell into right and left +compartments. Polycyrtid shells (Pl. 96) are peculiar to the #Botryodea#, +and characterised by a multilobate cephalis (cephalis multilocularis). +Stichocyrtid shells are those in which the primary cephalis remains simple, +and new joints are successively added to its basal pole; such shells occur +in the majority of the #Cyrtoidea#. Secondary chambers are sometimes added +in the other two groups (#Botryodea# and #Spyroidea#). When, as often +happens in these polythalamous Cyrtoid shells, two or three distinct joints +follow each other, the first is called the "cephalis," the second the +"thorax," and the third the "abdomen" (Tricyrtida Pls. 64-75). + + +124. _The Circoid Skeleton._--This is a very important and remarkable type +of skeletal formation, which occurs exclusively in the legion NASSELLARIA, +where it plays a very prominent part; its characteristic element is the +"sagittal ring," a simple, vertical, siliceous ring, which surrounds the +central capsule in its sagittal plane, and is specially differentiated in +its basal portion. This "primary sagittal ring" whose vertical allopolar +main axis coincides with that of the Monopylean central capsule embraced by +it, is characteristic of all members of the order #Stephoidea# (p. 931, +Pls. 81-83, 92-94); here it forms by itself the skeleton of the Stephanida +(Pl. 81); in the Semantida (Pl. 92) it is combined with a horizontal basal +ring, in the Coronida (Pls. 82, 93) with a vertical frontal ring and in the +Tympanida (Pls. 83, 94) with two horizontal rings, an upper mitral and a +lower basal. In the great majority of these #Stephoidea# there often +develop in definite places characteristic processes or apophyses, whose +branches combine to form a loose tissue or an incomplete lattice-shell. +This becomes complete in the #Cyrtellaria#, the majority of which retain +more or less {lxxxiii}distinct traces of the sagittal ring. Hence the +skeletons of all NASSELLARIA may be derived monophyletically (Hypothesis A, +p. 893) from a simple sagittal ring (_Archicircus_ and _Lithocircus_, Pl. +81). This theory, however, encounters the great difficulty that in many +#Stephoidea# (_Cortina_, _Cortiniscus_, &c.) it is combined in a remarkable +manner with the basal tripod of the #Plectoidea#, whilst in these latter it +is entirely wanting (compare p. 894). + + +125. _The Plectoid Skeleton._--Those forms are distinguished as Plectoid in +which three, four, or more radial siliceous spines proceed from a common +point, which lies excentrically outside the central capsule and at the +basal pole of its vertical allopolar main axis. This peculiar type of +skeletal formation only occurs in the legion NASSELLARIA, and is specially +characteristic of the order #Plectoidea# (p. 898, Pl. 91). But since the +essential elements of this remarkable skeleton also occur in many other +NASSELLARIA, sometimes combined with the Circoid, sometimes with the +Cyrtoid skeleton, it perhaps has a fundamental significance in this legion; +at all events it is possible to derive monophyletically all the other forms +of this legion from it (Hypothesis B, p. 893). The simplest form of the +Plectoid skeleton is a tripod, the three feet of which either lie in a +horizontal plane (_Triplagia_, Pl. 91, fig. 2), or correspond to the three +edges of a low pyramid (_Plagiacantha_). A fourth ray is sometimes added, +which stands vertically upon the summit of the pyramid (_Plagoniscus_, +_Plagiocarpa_, Pl. 91, figs. 4, 5). In other #Plectoidea# three secondary +rays are intercalated between the three primary (Hexaplagida, &c.); seldom +the number is greatly increased (Polyplagida, &c.). The rays are rarely +simple, but usually branched; in the Plagonida (Pl. 91, figs. 2-6) the +branches remain free; in the Plectanida (Pl. 91, figs. 7-13) they are +united to form a loose wicker-work. From such a web a perfect Cyrtoid shell +may arise. Several forms of Plagonida may also be readily confounded with +the isolated triradiate or quadriradiate spicula of many Beloid skeletons +(_Sphaerozoum_, _Lampoxanthium_, &c.). + + +126. _The Spongoid Skeleton._--From the simple lattice-skeleton which the +majority of Radiolaria possess, some of them develop a spongy shell; the +trabeculae of the lattice-work, situated in one plane in the former, are +developed in the latter in different planes and cross irregularly in all +directions; thus arises a kind of wicker-work of more or less spongy +structure, usually with very thin trabeculae and irregular meshes. Such +Spongoid shells are most common among the SPUMELLARIA, especially in the +#Sphaeroidea# (Spongosphaerida, Pl. 18) and #Discoidea# (Spongodiscida, +Pls. 41-47), more rarely in the #Prunoidea# and #Larcoidea#. Lattice-work +of similar spongy structure occurs very seldom among the NASSELLARIA, +_e.g._, in some #Plectoidea# (Pl. 91) and #Cyrtoidea# (_Spongocyrtis_, +_Spongopyramis_, _Spongomelissa_, &c., Pl. 56, fig. 10; Pl. 64, figs. 5-10, +&c.). Among the PHAEODARIA spongy skeletons are very rare; they {lxxxiv}are +to be seen in some #Phaeosphaeria# (_Oroplegma_, Pl. 107, fig. 1; +_Sagoplegma_, Pl. 108, fig. 2; _Auloplegma_, Pl. 111, fig. 8). No Spongoid +skeletons are known among the ACANTHARIA. + + +127. _The Cannoid Skeleton._--Cannoid or tubular skeletons are those which +are composed of hollow tubes; they occur exclusively in the PHAEODARIA or +CANNOPYLEA. Tubular processes, nevertheless, occur in some other +Radiolaria, as, for example, among the SPUMELLARIA in a portion of the +Collosphaerida (_Siphonosphaera_, _Caminosphaera_, Pls. 6, 7), and of the +#Prunoidea# (_Pipetta_, _Cannartus_, &c., Pl. 39, figs. 6-10, &c.), also +among the NASSELLARIA in _Theosyringium_ (Pl. 68, figs. 4-6), _Cannobotrys_ +(Pl. 96, figs. 3, 4, 8-11, 20-22), &c. In all these cases, however, the +tubes are direct processes of the cavity of the shell, the trabeculae of +the lattice-work being solid. Only in the CANNOPYLEA are the lattice-bars +themselves, the radial spines and appendicular organs, generally tubular +(hence the designation "Pansolenia"). The lumen of the thin-walled +siliceous tubes is filled with jelly, and hence the specific gravity of the +relatively large skeleton is considerably diminished. This peculiarity is +not found in all CANNOPYLEA; it is wanting in all Sagosphaerida and +Concharida, as well as in a part of the Orosphaerida and Castanellida; in +the latter there are found intermediate stages between hollow and solid +skeletal rods. Very often a fine siliceous thread runs in the axis of the +tubes, which is connected with its wall by lateral branches (Pl. 110, figs. +4, 6; Pl. 115, figs. 6, 7). More seldom the tubes are divided by horizontal +septa into a series of chambers (Medusettida, Pls. 118-120). The two +families Aulosphaerida (Pls. 109-111) and Cannosphaerida (Pl. 112) are +distinguished from all other PHAEODARIA by the fact that their tubes are +separated by astral septa in the nodal points of the lattice-shell (ss 112, +134). + + +128. _The Conchoid Skeleton._--By the name "Conchoid skeletons" are +distinguished the bivalved lattice-shells which occur exclusively in the +legion PHAEODARIA; they are quite characteristic of the #Phaeoconchia# or +_Phaeodaria bivalvia_, which embrace three families:--Concharida (Pls. +123-125), Coelodendrida (Pls. 121, 122), and Coelographida (Pls. 126-128). +The two valves of the lattice-shell of the Concharida are simple, +hemispherical, or boat-shaped, whilst in the Coelodendrida and +Coelographida tubes grow out from them, which branch and usually give rise +by anastomosis to a second external bivalved shell. In all #Phaeoconchia# +the two valves are so disposed about the central capsule that an open slit +remains between them, into which open the apertures of the central capsule; +and since all these _Phaeodaria conchoidea_ are TRIPYLEA, with three +typical openings in the central capsule, and since the two lateral +accessory openings lie at either side of the aboral pole, and the unpaired +main-opening at the oral pole of the main axis, it follows that the two +valves are to be regarded as dorsal and ventral as in the Brachiopoda (not +right and left as in the Lamellibranchiata). The dorsal and ventral +{lxxxv}valves are usually equal, but in a portion of the Concharida they +present constant differences. In this family the two valves are attached to +each other by their free edges, just as in the bivalved Mollusca and +Diatoms; and these edges may either be smooth (Conchasmida, Pl. 123, figs. +1-6), or dentate (Conchopsida, Pls. 124, 125); the valvular connection of +the latter is sometimes strengthened by a special ligament which unites the +two valves at the aboral pole (Pl. 123, figs. 8, 9). The form of the valve +is sometimes hemispherical, sometimes boat-shaped, with a sagittal keel. + + +129. _Medullary and Conical Shells._--In all Radiolaria whose skeleton +consists of a double shell or of two concentric lattice-shells united by +radial bars, an inner medullary shell (testa medullaris) and an outer +cortical shell (testa corticalis) may be distinguished (see note A, below). +The medullary shell is usually to be regarded as a primary, the cortical as +a secondary structure. Such double shells occur among the SPUMELLARIA in +the Dyosphaerida (Pls. 19, 20), as well as in many #Prunoidea# (Pls. 39, +40), #Discoidea# (Pls. 33, 34), and #Larcoidea# (Pls. 9, 10); among the +ACANTHARIA only in the family Phractopeltida (Pl. 133); among the +NASSELLARIA only in very few #Cyrtoidea# (_e.g._, _Periarachnium_, Pl. 55, +fig. 11), and finally among the PHAEODARIA in the Cannosphaerida (Pl. 112) +as well as in part of the Coelodendrida (Pl. 121) and Coelographida (Pls. +127, 128). In most cases (if not always?) the cortical shell arises by the +growth of radial spines from the surface of the medullary shell; these +become united at equal distances from the centre by transverse apophyses, +the surface of the secondary calymma furnishing the basis for their +secretion (s 85). Nevertheless, it seems that in many #Sphaerellaria# the +formation of the whole cortical shell proceeds simultaneously (at a +definite dictyotic period) like that of the primary medullary shell (see +note B). Whilst in the PHAEODARIA, ACANTHARIA, and NASSELLARIA, at most two +concentric shells are formed, in many SPUMELLARIA their number increases +continuously with additional growth; in many #Sphaerellaria# it rises to +four, eight, or even more, as well as in many #Discoidea# (if the +concentric, peripherally disposed rings of chambers be regarded as +incomplete flattened shells). In these cases either only the innermost +primary lattice-shell is to be styled "medullary shell," or at most the two +innermost (inner and outer medullary shells), all the others being +cortical. + + A. The distinction between medullary and cortical shells was originally + based in my Monograph (1862, p. 50) upon the topographical relation of + the lattice-shells to the central capsule, inasmuch as I regarded all + intracapsular shells as medullary, all extracapsular as cortical. + Hertwig, however (1879, p. 122), rightly pointed out that this + distinction is unpractical, "because the same lattice-shell in the same + species may lie within or without the central capsule, according to the + size of the latter." He proposes, therefore, to restrict the term + medullary shell to the innermost, and to call all the others cortical; a + course which seems justified by the special significance of the primary + innermost lattice-shell ("as the point of origin of the radial spines"). + But in most #Sphaerellaria# which form three or more concentric shells, + the two innermost, which lie near together within the {lxxxvi}central + capsule, are very different in size and dictyosis from all the others + which lie outside, and are separated by wider interspaces (compare Pls. + 17, 24, 29-32, 40, &c.). In these cases it appears better to regard the + two inner as inner and outer medullary shells, and all the others as + cortical shells. The character of the dictyosis in the intracapsular and + extracapsular shells is often so different that I have made it the basis + of separation of _Thecosphaera_ and _Rhodosphaera_ among the Liosphaerida + (p. 60), of Elatommatida and Diplosphaerida among the Astrosphaerida (p. + 208), &c. + + B.--R. Hertwig (1879, L. N. 33, pp. 40, 123) separates the true + (simultaneously formed) "cortical shells" (_e.g._, of _Actinomma_, + _Cromyomma_) from the arachnoid "siliceous networks" (_e.g._, of + _Diplosphaera_ and _Arachnosphaera_) which are formed by the successive + union of tangential apophyses of the radial spines. Whether this + principle is right in the theory or not, it cannot be carried out + practically. Compare also Pl. 25, fig. 4. + + +130. _Dictyosis or Lattice Formation of the Skeleton._--In the great +majority of Radiolaria the dictyosis or formation of lattice-work, and +especially the formation of a variously-shaped "lattice-shell," plays such +an important part that the whole class has long been popularly known in +Germany by the name "lattice animalcules" ("Gitterthierchen" or +"Gitterlinge") (_Protista dictyota_). The old name Polycystina also (1838), +although referring only to the SPUMELLARIA and NASSELLARIA, is derived from +the lattice-work of the siliceous skeleton. The extremely various forms in +which this is manifested furnish the means of distinguishing species. The +specific conformation of the skeletal lattice-work is usually caused by the +special disposition of the sarcodictyum (s 94), whose exoplasmatic threads +become silicified or (in the ACANTHARIA) converted into bars of acanthin. +In many cases, however, the form of the lattice is mainly dependent upon +the situation and form of the radial spines or of special processes from +them. With respect to their origin, two varieties of lattice may be +distinguished--simultaneous and successive. _Simultaneous dictyosis_ occurs +especially in the simple lattice-shells of the #Sphaerellaria# and +PHAEODARIA, where, at a given moment ("dictyotic moment") the _whole_ +lattice of the shell is excreted on the surface of the calymma. _Successive +dictyosis_, on the other hand, is found more particularly in the +lattice-shells of the ACANTHARIA (and in the concentric cortical shells of +many #Sphaerellaria#), which develop from the separate lattice-plates +formed by the apophyses of the radial spines, and hence not at the same +moment. The lattice-shells of the #Cyrtellaria#, which gradually grow out +from a sagittal ring or a basal tripod, arise by successive dictyosis. + + +131. _Dictyosis of the Spumellaria._--Siliceous lattice-structures are +wanting in the first section of the SPUMELLARIA, the #Collodaria#, but in +the second section, #Sphaerellaria#, they are developed in extraordinary +variety of details. In spite of this extreme richness in different forms, +the lattice-shells of the SPUMELLARIA may all be derived from one and the +same primitive ground-form, a simple lattice-sphere with regular hexagonal +meshes (_Phormosphaera_, p. 61, Pl. 12, figs. 9-11; _Heliosphaera_, &c.). +{lxxxvii}The siliceous bars which bound these regular and subregular meshes +are at first exceedingly then and filiform; afterwards they become thicker +or spread out laterally, whence the meshes often become round with a +hexagonal frame (Pl. 12, fig. 5; Pl. 28, fig. 1). If the latter vanish, a +lattice-shell with simple circular meshes is formed. Very commonly the +regular form of the meshes or pores becomes more or less irregular, +polygonal, or roundish. Hence, in general, four different principal forms +of dictyosis may be distinguished among the SPUMELLARIA; viz. (1) regular +or subregular _hexagonal_ meshes; (2) regular or subregular _circular_ +meshes; (3) irregular _polygonal_ meshes; (4) irregular _roundish_ meshes. +The three latter forms are to be regarded as secondary, derived from the +primary first form. In those SPUMELLARIA which possess several concentric +lattice-shells enclosed one within another, either these have all the same +form of dictyosis, or the lattice-work of the innermost primary shell is +different from that of the outer secondary shells (Pls. 19, 20); sometimes +these latter also differ more or less among themselves (s 129). + + +132. _Dictyosis of the Acantharia._--The lattice-structures of the +ACANTHARIA differ essentially from those of other Radiolaria in several +particulars. Firstly, they consist not of silica but of acanthin (s 102); +secondly, they are always secondary formations, usually developed from +transverse processes of the primary centrogenous radial spines; thirdly, +their formation is not simultaneous (at the same time over the same shell), +but successive (proceeding from the individual radial spines tangentially +towards the middle of the intervals); fourthly, the configuration of the +network is due to the relative position of the spines and the mode of union +of their transverse apophyses. Since they are at right angles to the +spines, and since the branches of the apophyses are at right angles to +them, the original ground-form of their dictyosis is a lattice-work with +quadrangular meshes; these are often quite regular and square (Pl. 130, +figs. 5, 6; Pl. 136, figs. 2, 9, &c.); more commonly they are rectangular +or irregularly quadrangular (Pl. 131, fig. 10; Pl. 133, figs. 2, 3, &c.). +In the majority of the ACANTHARIA the quadrangular form of the meshes +passes over into an irregularly polygonal or roundish one (Pls. 137, 138). +Very often the primary meshes of the lattice-shells, which immediately +surround the radial spines, are larger and more regular ("aspinal pores"), +whilst the numerous secondary meshes between them are smaller and irregular +("coronal pores"; Pl. 135, figs. 1-4, &c.). + + +133. _Dictyosis of the Nassellaria._--The siliceous lattice-structures of +the NASSELLARIA are formed on the whole like those of the SPUMELLARIA, with +which they were formerly united under the name "Polycystina." In this group +also there may be distinguished as two main forms the regular and +irregular. In the NASSELLARIA the regular lattice-structures generally +exhibit hexagonal or circular meshes, whilst the irregular are either +polygonal or roundish; the irregular forms are, however, much more abundant +than the {lxxxviii}regular, and a further distinction from the SPUMELLARIA +consists in the fact that the primary skeletal elements, from which the +lattice is secondarily developed, exercise a predominant influence upon +their form. These primary elements in the majority of the NASSELLARIA are +to be seen in two morphologically most important structures:--first, the +_primary sagittal ring_, which embraces the central capsule in the median +plane (s 124); and secondly, the _basal tripod_ (s 125), whose three +diverging rays proceed from the base of the central capsule, whilst +commonly a fourth vertical ray supports the dorsal side of latter (compare +Pls. 81-91, p. 892). In the majority of the NASSELLARIA these two primary +elements appear in combination, whilst in others only one of them is +recognisable. In addition there occur numerous monaxon lattice-shells in +which neither of these elements can be recognised, but a simple ovoid +lattice-shell (cephalis) alone forms the whole skeleton or its primary part +(Pl. 51, fig. 13; Pl. 98, fig. 13). The great difficulty in the +morphological interpretation and phylogenetic derivation of the +NASSELLARIAN skeleton lies in the fact that each of these three +elements--the primary sagittal ring, the basal tripod, and the latticed +cephalis--may form the whole skeleton by itself or be combined with one or +both of the others (p. 893). Even nearly related or at all events very +similar forms may differ very greatly in this respect. With regard to the +manifold forms of their dictyosis it follows that it is partly dependent +upon one of the two first elements, partly independent. In the +#Plectellaria# (or those NASSELLARIA which do not possess a complete +lattice-shell) the lattice-work is usually irregular and arises by union of +the ramifications, which proceed either from the primary sagittal ring +(Pls. 81, 82, 92-94) or from the basal tripod (Pl. 91). In the +#Cyrtellaria# (or NASSELLARIA with a complete lattice-shell, Pls. 51-80), +on the other hand, the lattice-work is sometimes regular, sometimes +irregular, being often very different in the different joints of a +segmented shell (Pl. 72); a great part of it arises independently of the +two chief morphological elements, and develops according to laws similar to +those which regulate the dictyosis of the SPUMELLARIA. + + +134. _Dictyosis of the Phaeodaria._--The lattice-structures of the +PHAEODARIA, which consist of a silicate of carbon (s 102), are on the whole +not developed in such variety as those of the other Radiolaria, but exhibit +several essentially different types of structure, not reducible to a common +primitive type of lattice-work. In one portion of this legion there occurs +an ordinary simple lattice-work (as in SPUMELLARIA and NASSELLARIA), with +solid trabeculae; of these the Castanellida (Pl. 113) and Concharida (Pls. +123-125) have usually regular or subregular, circular meshes, sometimes +hexagonally framed; the Orosphaerida (Pls. 106, 107) large irregular +polygonal meshes with thick trabeculae, the Sagosphaerida (Pl. 108) large +triangular meshes with thin filiform trabeculae. The Challengerida (Pl. 99) +are characterised by a very delicate regular lattice-work, with minute +hexagonal pores, like a Diatomaceous frustule. The Medusettida (Pls. +118-120) {lxxxix}show a peculiar alveolar structure, numerous small +compartments being enclosed between two parallel plates. In the Circoporida +(Pls. 114-117) and Tuscarorida (Pl. 100) the opaque porcellanous shell has +a peculiar cement structure (s 104), and the lattice-structure is confined +for the most part to characteristic rings of pores at the base of the +hollow tubes, which arise from the shell. The most peculiar lattice-work, +however, appears in the segmented shell of the Aulosphaerida (Pls. 109-111) +and Cannosphaerida (Pl. 112). In the former the large meshes of the +lattice-work are usually subregular and triangular, in the latter +polygonal; the trabeculae are hollow cylinders, filled with jelly, and +containing usually a central axial thread. In each nodal point of the +lattice, in which three or more tangential tubes meet, these are separated +by stellate or astral septa. + + +135. _Radial Spines of the Skeleton._--The skeleton in the great majority +of Radiolaria is armed with radial spines, which are of great importance in +the development of their general form and of their vital functions. From a +morphological point of view the number, arrangement, and disposition of the +spines is usually the determining factor as regards the general form of the +skeleton. Physiologically they discharge distinct functions, as organs of +protection and support; they act also, like the tentacles of the lower +animals, as prehensile organs, since their points, lateral branches, barbed +hooks, &c. serve to hold fast nutritive materials. In general main-spines +and accessory spines may be distinguished in most Radiolaria; the former +are of pre-eminent importance in determining the figure of the skeleton; +the latter are merely appendicular organs. The main-spines present such +characteristic and important differences in the various legions of +Radiolaria that they must be considered separately. + + +136. _Radial Spines of the Spumellaria._--The radial spines, which exhibit +most manifold variations in the large order #Sphaerellaria#, present +characteristic differences in its four suborders. In the #Sphaeroidea# +their number and disposition serve for the separation into families (p. +59); the Cubosphaerida (Pls. 21-25) always possess six radial main-spines, +which stand opposite to each other in pairs and lie in three diameters of +the shell, which are at right angles to each other and correspond to the +axes of the regular crystallographic system. The Staurosphaerida (Pl. 15) +have four spines, which form a regular cross and stand opposite to each +other in pairs, in two axes at right angles. The Stylosphaerida (Pls. +13-17) show only two main-spines, which are opposed to each other in the +vertical main axis of the body. Finally, the Astrosphaerida (Pls. 18-20, +26-30) are characterised by a larger and variable number of radial spines +(eight, twelve, twenty or more), sometimes regularly, sometimes irregularly +arranged. Among the other #Sphaerellaria# the #Prunoidea# (Pls. 13-17, 39, +40) are most allied to the Stylosphaerida with two opposite main-spines; +the #Discoidea# (Pls. 31-47), on the other hand, to the Staurosphaerida +with four crossed spines; there exist, however, #Discoidea# with two +opposite, three marginal, or numerous radial main-spines; it is +{xc}characteristic of this suborder that they all usually lie in the +horizontal median plane of the lenticular shell, arising from its +equatorial margin. The #Larcoidea# (Pls. 9, 10, 49, 50) show a great +variety in the number and arrangement of their radial main-spines, which in +the different families of this suborder stand in direct causal relation to +the various forms of growth of the shell; usually the primary main-spines +lie either in the three different dimensive axes, at right angles to each +other, whose differentiation is characteristic of the lentelliptical +Larcoid shell (ss 34, 122) or in definite diagonal axes, which cut the +former obliquely. The radial spines of the SPUMELLARIA are _never_ united +in the centre of the body, but arise separately from the surface of the +primary central lattice-shell (medullary shell), more rarely from one of +the secondary (cortical) shells, which enclose it. Their form is originally +three-edged (sometimes pyramidal, sometimes prismatic); the cause of this +is to be found in their origin from the nodal points of the lattice-shell, +whose meshes are primitively hexagonal; hence three trabeculae unite in +each nodal point, and are produced into three edges of the spine. Very +commonly, however, the spines are round (conical or cylindrical), more +rarely polygonal. The three edges are often delicately toothed, not +unfrequently spirally twisted around the axis of the spine (Pl. 21, figs. +1, 12). + + +137. _Radial Spines of the Acantharia_.--The radial spines of this legion +have a much greater significance than in the other three classes of +Radiolaria, since here alone they are the primary determining factors in +the skeletal structure, and grow outwards from the middle of the central +capsule. This centrogenous origin of the radial spines is as characteristic +of the ACANTHARIA as their chemical constitution, which is not siliceous +but acanthinic (s 102). Furthermore, their form is in most cases so +peculiar that even an isolated ACANTHARIAN spine can be generally +distinguished from one belonging to either of the other three legions. In +the great majority of the ACANTHARIA (all #Acanthonida# and +#Acanthophracta#) twenty radial spines are constantly present, which, +disposed according to a definite geometrical law, make up the skeleton +(compare s 110 above and p. 717). The twenty spines are generally simply +apposed to each other in the centre (either by the surfaces or the edges of +their pyramidal base); more rarely they are completely united and form a +single star-like piece of acanthin (_Astrolithium_). Very rarely +(_Acanthochiasma_) each two opposite spines are united so that ten +diametric bars cross in the middle of the central capsule. Whilst in the +great majority of ACANTHARIA these twenty radial spines are present, the +small group #Actinelida# is characterised by the possession of an +inconstant, often very large number, sometimes over one hundred. Among +these #Actinelida# are probably to be found the stem-forms of the whole +legion. The variously modified spines of the ACANTHARIA may be grouped in +three main categories: (1) round (cylindrical or conical); (2) four-edged +(prismatic or pyramidal); (3) two-edged (leaf- or sword-shaped). The latter +very commonly bear two {xci}opposite transverse processes, the former four +crossed ones. By ramification and union of these apophyses arise the +lattice-shells of the #Acanthophracta# (excepting the Sphaerocapsida). + + +138. _Radial Spines of the Nassellaria._--The radial spines in this legion +show as great a variety in their form as in the SPUMELLARIA, and, as in +them, are solid, siliceous bars, usually three-edged (prismatic or +pyramidal), or round (cylindrical or conical); more seldom they are +polygonal in section. The great majority of the NASSELLARIA are, however, +distinguished by a triradial structure, three primary radial bars diverging +from the base of the central capsule (usually from the centre of the +porochora); there is usually in addition a fourth apical spine, which +passes upwards vertically or obliquely on the dorsal aspect of the central +capsule. These three or four typical radial spines of the NASSELLARIA may +be derived with great probability from the basal tripod of the #Plectoidea# +(_Plagoniscus_, _Plectaniscus_, &c., Pl. 91); and since this tripod is very +characteristically combined in _Cortina_ and _Cortiniscus_ with the primary +sagittal ring of the #Stephoidea#, the three typical rays may be generally +designated "cortinar feet," in contradistinction to the other radial +processes of the NASSELLARIAN skeleton. One of the three descending basal +feet ("pes caudalis," Pls. 91-95, C) is always unpaired, and lies in the +vertical median plane (or sagittal plane), just as does the vertically +directed apical spine, which originally forms the dorsal bar of the +sagittal ring, and is produced upwards into the "apical horn," (marked _a_ +on the plates). The other two basal feet are paired, and diverge right and +left, forwards and downwards ("pedes pectorales," _p.p._). Six-rayed +NASSELLARIA, in which three secondary (interradial) feet are intercalated +between the three primary (perradial) cortinar feet, are less common than +the three-rayed forms. In some groups the number rises still higher, nine, +twelve, or even more secondary feet being intercalated between the three +primary. Besides, accessory radial spines may be developed on different +parts of the shell, which have sometimes a definite relationship to the +typical radial spines, sometimes not. Their form and ramification are very +various (Pls. 51-98). + + +139. _Radial Spines of the Phaeodaria._--The radial spines of the +PHAEODARIA are very clearly distinguished from those of other Radiolaria by +the fact that they are usually hollow tubes, rarely solid bars. As a rule, +the tubes are cylindrical, often slightly fusiform or conical, their +siliceous wall is very thin, and their lumen filled with jelly; a fine +thread of silica usually runs in the axis, and in several families is +connected by fine transverse threads with the wall of the tube (Pl. 110, +figs. 4, 6; Pl. 115, figs. 6, 7). The peculiar family Medusettida is +characterised by a very remarkable segmentation of the hollow spines (Pls. +118-120). Each tube is divided by a series of septa into chambers, which +communicate by a central or excentric opening in each septum, an +arrangement resembling the siphuncle of the chambered Cephalopod shells. +The number and {xcii}arrangement of the radial tubes in most PHAEODARIA is +indefinite and very variable; only in a few families is the number constant +in each species and genus, and the disposition regular. The Medusettida +(Pls. 118-120) resemble the NASSELLARIA, inasmuch as equal radial feet +diverge from the base of their shell, sometimes three in number +(_Cortinetta_, Pl. 117, fig. 9), sometimes four (_Medusetta_, Pl. 120, +figs. 1-4), sometimes six (_Gazelletta_); _Gorgonetta_ is specially +distinguished by the possession of six ascending and six descending spines +regularly alternating (Pl. 119). The Tuscarorida (Pl. 100) usually have +three or four equidistant feet. The Circoporida (Pls. 115-117), on the +other hand, rather approach the #Sphaeroidea#, their spherical or regular +polyhedral shell having a definite number of tubular radial spines, which +arise at regular intervals from their angles; _Circoporus_ has six, +_Circospathis_ nine, _Circogonia_ twelve, and _Circorrhegma_ twenty radial +tubes. Very rarely the tubes of the PHAEODARIA are angular, usually they +are round, more or less cylindrical, though they are often bifurcated or +even ramified, and exhibit a great wealth of the most delicate appendages; +siliceous hairs, bristles, spines, barbed or anchor-like hooks, spathillae, +brushes, circlets, &c. (compare Pls. 99-128). + + +140. _Main-Spines and Accessory Spines._--As accessory spines (Paracanthae) +we oppose to the main-spines (Protacanthae), just described, all those +processes which have no determining influence upon the formation of the +skeleton as a whole, but are to be regarded as secondary constituents of +the skeleton, or appendicular organs of inferior significance. They are +developed in the utmost variety, sometimes as hairs or bristles, sometimes +as thorns or clubs, either straight or curved (often zigzag), smooth or +barbed; sometimes standing vertically upon the shell, or directed towards +the centre, sometimes obliquely, or rising at a definite angle. In those +SPUMELLARIA whose lattice-shell consists of several concentric spheres, the +accessory spines generally arise from the outermost, the main-spines, on +the contrary, from the innermost. In the NASSELLARIA, multifarious forms of +accessory spines are especially developed in the order #Plectellaria#. In +the PHAEODARIA they are often furnished with delicate appendages, _e.g._, +anchor-hooks, spathillae, coronets, &c. Among the ACANTHARIA the accessory +spines which arise from the surface of the shell in the #Acanthophracta# +are very characteristic. They are not radially disposed (like the similar +superficial spines of the SPUMELLARIA), but parallel to the radial +main-spines from whose transverse processes they arise. Since in all these +#Acanthophracta# the twenty radial main-spines are opposite to each other +in pairs, all the accessory spines (often several hundred) are parallel to +ten different regularly disposed axes of the lattice-shell (Pls. 134-138). + + The skeletons of the Radiolaria, in addition to the general relations + which have been discussed above, present numerous and important special + differences in the various larger and smaller groups. These are indicated + in detail in the descriptions of the legions, orders, and families in the + systematic portion of this Report. + + + + +{xciii}BIOGENETICAL SECTION. + +A SKETCH OF OUR KNOWLEDGE OF THE DEVELOPMENT OF THE RADIOLARIA IN THE YEAR +1884. + + +---- + + +CHAPTER V.--ONTOGENY OR INDIVIDUAL DEVELOPMENT. + +(ss 141-152.) + +141. _Individual Developmental Stages._--The germinal history of the +Radiolaria presents great obstacles to direct observation, and hence is +very incompletely known. The fragmentary observations, however (having been +made on Radiolaria of very various groups and supplemented by comparative +anatomical considerations), allow us to draw a general picture of the +essential developmental processes in this great class. It may probably be +assumed that in all Radiolaria, after maturation, the central capsule +discharges the function of a sporangium, and its contents are broken up +into numerous flagellate swarm-spores (zoospores). After these flagellate +swarm-spores (resembling _Astasia_) have emerged from the ruptured central +capsule, they probably pass over into a _Heliozoan_-stage (_Actinophrys_) +and then after the formation of a jelly-veil into the condition of +_Sphaerastrum_. Afterwards, when a membrane is formed between the outer +jelly-veil and the inner nucleated cell-body, an _Actissa_-stage arises, +which exhibits in its simplest form the differentiation of the spherical +unicellular body into the central capsule and calymma. _Actissa_ thus +represents both ontogenetically and phylogenetically the primitive +condition of the Radiolarian organism, and may thus be regarded as the +point of departure of all other forms. + + +142. _The Astasia-Stage._--The formation of flagellate zoospores in the +mature central capsule is probably to be regarded as the common form of +individual development in all Radiolaria; since the whole contents are +utilised in the formation of these swarm-spores, and since the +extracapsulum takes no share in the process and perishes after they are +evacuated, the _central capsule_ may be regarded as a _sporangium_ (see +note A, below). The zoospores of the Radiolaria generally arise in the +following way:--the nucleus of the unicellular organism, sometimes early, +sometimes late (and in several different ways, ss 63-70) breaks up into +numerous small nuclei, and each of these surrounds itself with a small +portion of the endoplasm. Very often, perhaps generally, this endoplasm +contains one or several fat-granules and sometimes also a small oblong +crystal; from the protoplasm {xciv}of the small roundish or ovoid cells +protrudes one or more vibratile flagella. The fully developed spores, which +commence their vibrations even within the central capsule, emerge when it +ruptures, and swim about freely in the surrounding water by means of the +flagellum. At this stage of its existence the young Radiolarian represents +essentially the simplest form of the Flagellata, such as _Astasia_ or +_Euglena_; the unicellular body is for the most part ovoid or +subcylindrical, sometimes fusiform or reniform, usually from 0.004 to 0.008 +mm. in diameter (Pl. 1, fig. 1_c_; Pl. 129, fig. 11). In the anterior part +of the flagellate cell, immediately behind the base of the flagellum, lies +a homogeneous, spherical nucleus, whilst in the posterior part are usually +several small fat-granules and often also a small oblong crystal (hence the +name "crystal-spore," "Krystall-Schwaermer"). The number of vibrating +flagella, which are extremely long and fine, seems to be variable, usually +one, sometimes two, occasionally perhaps three, or even four or more (see +note B). + + A. The formation of the motile spores in the central capsule was first + observed by J. Mueller in _Acanthometra_ (1856, L. N. 10, p. 502), then + by A. Schneider in _Thalassicolla_ (1858, L. N. 13, p. 41), and finally + by myself in _Sphaerozoum_ (1859, L. N. 16, p. 141). These older + observations were, however, incomplete, for the origin of the motile + corpuscles from the contents of the central capsule was not observed. The + first complete and detailed observations upon the formation of spores in + the Radiolaria were published in 1871 by Cienkowski (L. N. 22, p. 372, + Taf. xxix.); they relate to two different Polycyttaria, _Collosphaera_ + and _Collozoum_. These investigations were supplemented by R. Hertwig on + _Collozoum_ and _Thalassicolla_ (1876, L. N. 26, pp. 28, 43, &c.); on + _Collozoum_ he made the important discovery that the Polycyttaria form + two kinds of spores, one with and the other without crystals, and that + the latter are divided into macrospores and microspores (compare the + chapter on "Reproduction," ss 212-216). Quite recently Karl Brandt has + confirmed these observations, and has extended them to all the genera of + Polycyttaria (1881, L. N. 38, p. 393, and 1885, _loc. cit._). + + B. The number of flagella, projecting from each spore, is very difficult + to determine, owing to their extraordinary length and slenderness. It + appeared to me that in the majority of those Radiolaria whose spores I + investigated only a single flagellum could be demonstrated with + certainty, although sometimes two, springing from a common base, seemed + to be present. Compare the chapter on "Reproduction," (s 215) and the + recent work of Karl Brandt on Sphaerozoea (1885, L. N. 52, pp. 145-174). + + +143. _The Actinophrys-Stage._--The fate of the flagellate zoospores which +emerge from the mature central capsule of the Radiolaria has not hitherto +been decided by actual observation; all attempts to rear the swarming +zoospores have been in vain, for they have soon died. From what we know, +however, of the comparative morphology of the Protista, the hypothesis is +fully justified, that between the _Astasia_-stage of the flagellate +swarm-spores, and the well-known _Actissa_-stage of the simplest +Radiolaria, there lies an intermediate developmental stage, which may be +regarded as being essentially the simplest Heliozoan form, _Actinophrys_ or +_Heterophrys_. The swarm-spore is very probably converted directly in to a +simple floating _Heliozoon_ by its elongated or ovoid body {xcv}becoming +spherical and by fine pseudopodia protruding all round instead of a single +flagellum; the nucleus at the same time assuming a central position. + + +144. _The Sphaerastrum-Stage._--The _Actinophrys_-stage of the young +Radiolaria, which proceeds immediately from the flagellate zoospore, is +probably connected with the _Actissa_-stage by an intermediate form, which +may be regarded as a simple skeletonless _Heliozoon_ with a jelly-veil; a +well-known example of such a form is _Sphaerastrum_ (in the solitary, not +the social condition) and _Heterophrys_. This important intermediate form +has arisen from the simple _Actinophrys_-stage by the excretion of an +external structureless jelly-veil, such as is formed in many other Protista +(_e.g._, in the encystation of many Infusoria). The young Radiolarian in +this second _Heliozoon_-stage becomes a simple cell with pseudopodia +radiating on all sides; its body consists of three concentric spheres, the +central nucleus, the protoplasmic body proper, and the surrounding calymma +or jelly-veil. When a firm membrane is developed between the last two +spheres this _Sphaerastrum_-stage passes over into the _Actissa_. + + The gap in our empirical knowledge which still exists between the + flagellate stage (s 142) and the simplest Radiolarian stage (_Actissa_, s + 145), can be filled hypothetically only by the assumption of several + _Heliozoon_-stages following one upon another. It is possible also that + the capsule-membrane is not formed between the endoplasm and exoplasm (as + here supposed), but that the membrane was formed first outside the cell + and the extracapsulum subsequently secreted around it. + + +145. _The Actissa-Stage._--The first SPUMELLARIAN genus, _Actissa_, is not +only the simplest form actually observed among the Radiolaria, and the true +prototype of the whole class, but also the simplest form under which the +Radiolarian organisation can be conceived. It is therefore extremely +probably that _Actissa_ not only forms the common stem-form of the whole +class in a phylogenetic sense, but is also its common ontogenetic or +germinal form. Probably in all Radiolaria the _Sphaerastrum_-stage develops +immediately into the typical _Actissa_-stage, by the formation of a firm +membrane between the protoplasmic body of the spherical Heliozoan cell and +its jelly-veil. Thus arises the characteristic central capsule, which is +wanting in the nearly related Heliozoa. It is further probable that all +Radiolaria in their early stage will so far conform to the state of things +in _Actissa_ as to have the capsule-membrane of the spherical skeletonless +cell perforated everywhere by fine pores. This structure is retained in all +SPUMELLARIA, whilst in the other three legions those structural relations +of the capsule which are characteristic of each develop from the +_Actissa_-stage. + + +146. _The Ontogeny of the Spumellaria._--In the simplest case the +individual development in the SPUMELLARIA ceases with the _Actissa_-stage. +In all other genera of this legion diverging forms proceed from this, of +which the different growth of the three dimensive {xcvi}axes on the one +hand (ss 44, 45), and the differentiation of the various parts of the +unicellular organism with the formation of the skeleton on the other, are +of pre-eminent significance. Even in the varying growth of the central +capsule in the different dimensions of space in the skeletonless +#Colloidea#, four different modes may be distinguished, which further, in +the corresponding development of the skeleton, furnish the basis for the +origin of the four orders of #Sphaerellaria#. The most primitive and +simplest form of growth, equal extension in all directions, is found in the +spherical central capsule and the concentric spherical skeletons +(_Procyttarium_, #Sphaeroidea#). When the growth of the central capsule +proceeds more rapidly in the direction of the vertical main axis than in +any other direction, the ellipsoidal or cylindrical central capsule +(_Actiprunum_) arises, and the vertically elongated skeleton of the +#Prunoidea#, which is derived from it. When, on the contrary, the growth of +the central capsule and lattice-shell is less in the direction of the +vertical main axis than in any other direction, the lenticular or discoid +central capsule (_Actidiscus_) arises, and the corresponding lenticular +shell of the #Discoidea#. Finally, even quite early in many SPUMELLARIA, +the growth of the central capsule and of the corresponding lattice-shell in +the three dimensive axes is different, and hence arise the lentelliptical +forms whose geometrical type is the triaxial ellipsoid or the rhombic +octahedron (_Actilarcus_, #Larcoidea#). Thus the origin of the four orders +of #Sphaerellaria# is simply explained by a varying growth in the different +dimensive axes. The _primary_ (innermost) lattice-shell is in this legion +always _simultaneously_ developed (suddenly excreted at the moment of +lorication from the sarcodictyum). The _secondary_ lattice-shells, on the +other hand, which surround the former concentrically, and are united with +it by radial bars, arise _successively_ from within outwards. + + +147. _The Ontogeny of the Acantharia._--The individual development of the +ACANTHARIA in the simplest case (_Actinelius_) stops at a point which +differs from the _Actissa_-stage only in the change of radial axial threads +into acanthin spines. In the small group #Actinelida#, their number remains +variable and usually indeterminate (Adelacantha), whilst in the great +majority of the legion (#Acanthonida# and #Acanthophracta#) the number is +constantly twenty, and those spines are regularly arranged according to the +Muellerian law in five parallel circles, each containing four crossed +spines (Icosacantha). The simplest form among these latter is +_Acanthometron_, which may be regarded both ontogenetically and +phylogenetically as the common starting-point of all the Icosacantha. +Within this extensive group variations in the length of the dimensive axes +appear, similar to those observed in the SPUMELLARIA. In the Astrolonchida +and #Sphaerophracta# the central capsule remains spherical, extending +equally in all directions; and correspondingly the lattice-shell, which is +excreted on the surface of the spherical calymma, remains spherical. In the +Belonaspida (just as in the #Prunoidea#) {xcvii}this form passes over into +an ellipsoid by prolongation of one axis; on the contrary, in the +Hexalaspida (as in the #Discoidea#) the discoidal or lenticular form arises +by shortening of an axis. Finally, in the Diploconida, and in some +Hexalaspida in which the growth is different in all three dimensive axes +(as in the #Larcoidea#), both the central capsule and the shell assume the +lentelliptical form. The lattice-shell of the #Acanthophracta# is usually +successive in its development, since from each of the twenty radial spines +two or four tangential apophyses proceed, whose branches subsequently unite +and combine to form the lattice-shell. Only in the peculiar Sphaerocapsida +can the pavement-like shell arise simultaneously or in a moment of +lorication. + + +148. _The Ontogeny of the Nassellaria._--The individual development of the +NASSELLARIA in the simplest instance remains stationary at the skeletonless +Nasselid stage (_Cystidium_, _Nassella_), which can be immediately derived +from the foregoing _Actissa_-stage by the disappearance of the pores in the +upper (apical) hemisphere of the central capsule, whilst in the lower +(basal) portion they are modified to form a porochora; the podoconus is +developed within the endoplasm upon this latter. Usually the spherical form +of the central capsule passes over into an ovoid or ellipsoidal one, the +vertical axis which passes through the centre of the porochora being +elongated. From the skeletonless Nassellida the other NASSELLARIA may be +derived both ontogenetically and phylogenetically by the excretion of an +extracapsular siliceous skeleton. Unfortunately, the earliest stages in the +formation of this skeleton are unknown, and hence no answer can at present +be given to the important question, in what order the three primary +skeletal elements of the NASSELLARIA (the basal tripod, sagittal ring, and +latticed cephalis) appear (compare ss 111 and 182). If, for example, in +_Cortina_ and _Tripospyris_ the basal tripod were to appear first in the +ontogeny, and the sagittal ring were developed from this, then the +#Plectoidea# would be rightly considered to be the oldest forms in the +phylogeny of the skeleton-forming NASSELLARIA; and in the contrary case the +#Stephoidea# would be so regarded. The relations of growth in the three +dimensive axes are very variable in the NASSELLARIA; the three most +important factors in this respect (partly separately and partly in +combination) are; (1) the development of the basal tripod to a triradial +stauraxon form (the ground-form being a three-sided pyramid); (2) the +development of the sagittal ring in the median plane of the body (the +vertical axis having the poles different); (3) the development of the +latticed cephalis outside the central capsule (the poles of the vertical +axis being again different). Since the development both of the skeleton and +of the malacoma is characterised in most NASSELLARIA by the stronger growth +of the vertical axis and the differentiation of the two poles, the +allopolar monaxon ground-form acquires a predominant significance in this +legion (s 32); the starting point of most of the further modifications is +the basal pole of the vertical main axis. Next to this the sagittal axis is +usually the most important determining factor (its dorsal and ventral poles +being {xcviii}usually different), more rarely the frontal axis (with equal +right and left poles). In the zygothalamous #Spyroidea# (as in the +#Stephoidea#) the formation of the shell proceeds from the sagittal ring, +whilst in the polythalamous #Cyrtoidea# the latticed cephalis is always the +starting point, from which a series of joints (thorax, abdomen, and in the +Stichocyrtida, the numerous post-abdominal joints) successively arise +(unipolar growth). + + +149. _The Ontogeny of the Phaeodaria._--The individual development of the +PHAEODARIA in the simplest case stops with the skeletonless condition of +the Phaeodinida (_Phaeodina_, _Phaeocolla_), which can be immediately +derived from the foregoing _Actissa_-stage by the disappearance of the +pores in the greater part of the central capsule, the characteristic +astropyle being developed at the basal pole (s 60). Since this particular +form and structure of the spheroidal central capsule remains the same in +all PHAEODARIA, whilst the formation of their skeleton follows very +different directions, it follows that further common paths of development +are excluded both ontogenetically and phylogenetically. What will be laid +down in this respect as regards the phylogeny of the different groups of +PHAEODARIA (ss 194-199) holds true also of their ontogeny. The relations of +growth in the three dimensive axes are hence very different in the +skeletons of the various groups of PHAEODARIA. This difference is best +marked in the #Phaeoconchia#, whose bivalved lattice-shells have as their +ground-form the rhomboid pyramid of Ctenophora. In most #Phaeogromia# the +monaxon lattice-shell may develop simultaneously by sudden excretion at a +particular moment of lorication; this is also the case with the polyaxon +lattice-shells of the #Phaeosphaeria#. In their future growth the +development of basal or radial apophyses is of special importance. In the +majority of the PHAEODARIA these apophyses are tubes of silicate filled +with jelly (often provided with an axial siliceous thread); thus their +development is distinguished by complications which are absent in the case +of the other three legions. + + +150. _Growth._--The growth of the body in the Radiolaria, as in all other +organisms, is the fundamental function of individual development (see note +A). All structural relations which this richest class of the Protista +exhibits may be referred to different forms of growth, either of the +unicellular malacoma or of the skeleton which it produces. In general the +special development of the skeleton is dependent upon that of the central +capsule, and of the sarcodictyum on the surface of the calymma; in the +further growth, however, the conditions are reversed, and the condition of +the skeleton already formed directly determines the further development of +the central capsule and of the calymma with its sarcodictyum. The four +legions of Radiolaria show, speaking generally, certain characteristic +differences in growth, which are due in great part to the different +structure and ground-form of their central capsule. In the two legions of +the Porulosa (SPUMELLARIA and ACANTHARIA), in which the central capsule is +originally spherical and {xcix}the ground-form of the skeleton either +polyaxon or isopolar monaxon, two fundamental and variously combined +directions of growth are recognisable; firstly, the _concentric_ growth +(equal increase of volume in all directions), and secondly, multipolar or +_diametral_ growth (hypertrophy of certain parts in the direction of +definite pairs of radii). A different state of things obtains, however, for +the most part, in the two legions of the Osculosa (NASSELLARIA and +PHAEODARIA), in which the central capsule possesses a vertical main axis +with different poles, and the structure of the skeleton is determined by +this allopolar monaxon ground-form. The two fundamental directions of +growth here combined in the most various ways are, firstly, _unipolar_ +growth (starting from the basal pole of the vertical main axis), and +secondly, radial or _pyramidal_ growth (characterised by the different +development of separate parts in the direction of definite radii). Whilst +the growth of the _malacoma_ is dependent on intussusception (as in most +organic structures capable of imbibing), the growth of the _skeleton_ in +all Radiolaria takes place by apposition (see note B). + + A. The earliest investigations into the modes of growth in the Radiolaria + are due to J. Mueller (L. N. 12, pp. 21-33). More detailed communications + I gave myself in my Monograph (L. N. 16, pp. 150-159). The relations + there sketched have now, in consequence of the examination of the + Challenger collection, undergone many important additions, and in some + divisions, important modifications; these are for the most part treated + of in the general account of the separate families. + + B. The view here maintained, that the skeleton of all Radiolaria grows + only by apposition, appeared formerly to have certain exceptions. I + thought I had shown that in _Coelodendrum_ the thin-walled tubes grew not + only in length but also in thickness, with continuous increase in the + lumen (L. N. 16, pp. 152, 360). Further K. Brandt concluded, from the + varying size of the median bars in the twin-spicules of _Sphaerozoum_, + that these siliceous structures grow by intussusception (L. N. 38, p. + 401). Both suppositions have been proved erroneous and I have come to the + opinion that in all Radiolaria the skeleton grows by apposition. + + +151. _Regeneration._--Whilst the general course of individual development +(perhaps without any exception in the Radiolaria), begins with the +formation of zoospores in the central capsule, there yet occurs in some +groups a different form of ontogeny, introduced by simple division of the +unicellular organism, and coming under the term "regeneration" in its wider +sense. This spontaneous division occurs quite commonly in the Polycyttaria +(or social SPUMELLARIA), and produces their colonies (compare the chapter +on Reproduction, s 213). On the contrary, it has not been observed in the +solitary SPUMELLARIA, nor in the ACANTHARIA and NASSELLARIA; possibly, +however, the peculiar ACANTHARIAN family, Litholophida, has arisen by the +division of Acanthonida (compare p. 734). Among the PHAEODARIA division is +commonly observed in the order #Phaeocystina# (which have an incomplete +Beloid skeleton or none), and also in the #Phaeoconchia#. In all these +cases the increase by division is nothing else than an ordinary case of +cell-division, in which bisection of the nucleus precedes that of the +central capsule. The regeneration by {c}which each of the two +daughter-cells develops to a complete mother-cell depends upon simple +growth. Another form of regeneration, different from this, has been +observed in _Thalassicolla_. If the central capsule be extracted +artificially from the large concentric calymma, the enucleated central +capsule produces a new extracapsulum, with sarcomatrix, pseudopodia, and +calymma. This experiment may be repeated several times with the same +result. (Compare A. Schneider, 1867, L. N. 20.) + + +152. _The Formation of Colonies._--The individual development of colonies +takes place in all three families of the Polycyttaria (Collozoida, +Sphaerozoida, Collosphaerida) in the same simple way, by the repeated +division of a single monozootic SPUMELLARIAN. Since these divisions only +affect the central capsule and not the extracapsulum, the sister-cells, +which arise by repeated division of the mother, remain enclosed in a common +rapidly growing calymma. Probably in all Polycyttaria the commencement of +the formation of colonies immediately follows the _Actissa_-stage of the +monozootic mother-cell (or takes place in the _Thalassicolla_-stage, which +arises from the former by the development of alveoles in the calymma). The +simple central nucleus separates (by direct nuclear division) into two +halves, and the central capsule follows this process of bisection, becoming +constricted in the middle between the two daughter nuclei (Pl. 3, fig. 12). +In the further growth of the colony the process of division proceeds in the +older, now multinucleate, central capsules, in which an oil-globule has +taken the place of the original nucleus; then the division of the +oil-globules precedes that of the central capsule (Pl. 5, fig. 1). Another +mode of growth of the colonies is the multiplication of the central +capsules by gemmulation, or the formation of the so-called "extracapsular +bodies" (Gemmulae, s 214). The characteristic skeletal structure of the +different species appears at a later stage. Whether ripe central capsules +can emerge from the social bond of a coenobium, and, having become +isolated, establish the formation of a new colony, is very doubtful. The +various forms which the coenobium assumes in the different species of +Polycyttaria, are due partly to simple growth, partly to the development of +large vacuoles in the calymma. + + The _form and size_ of the coenobia appear in many fully developed + Polycyttaria to exhibit specific differences, which require further + investigation; in the young stage, on the contrary, they are simple + spheres or ellipsoids, often cylindrical or sausage-shaped (Pl. 3, figs. + 1, 4, 6, 11). In some species the cylindrical gelatinous bodies become + moniliform, and separated by transverse constrictions into many segments, + each of which encloses a large alveole (Pl. 3, fig. 10). The rare + ring-shape (Pl. 4, fig. 1) which I figured in 1862 in the case of + _Collozoum_ (L. N. 16, p. 522, Taf. xxxv. fig. 1), I have recently + observed in different species of Polycyttaria; it is capable of a very + simple mechanical explanation, both ends of a sausage-shaped colony + having been accidentally brought into contact by a wave and having united + by agglutination. Quite recently Brandt has given a very complete account + of the development, form, and growth of Polycyttarian colonies in his + work on the colonial Radiolaria of the Bay of Naples (1885, L. N. 52, pp. + 71-85). + + + +{ci}CHAPTER VI.--PHYLOGENY OR GENEALOGICAL DEVELOPMENT. + +(ss 153-200.) + +153. _Sources of Phylogenetic Knowledge._--For the purpose of constructing +a hypothetical genealogical tree of the Radiolaria, as of all other +organisms, three sources of information are open to us, viz., +palaeontology, comparative ontogeny, and comparative anatomy. In the +present case, however, these three sources are of very different value; the +first two are at present only very inadequately known and have only been +partially investigated, hence they can only be utilised to a very slight +extent. The comparative anatomy of the Radiolaria, on the other hand, is so +completely known, and affords such certain glimpses into the morphological +relations of the related groups, that by its aid we are in a position at +all events to lay down the general features of their phylogeny with some +probability, and to lay the foundation of a natural system. + + +154. _Natural and Artificial Systems._--Although in the classification of +the Radiolaria, as in the case of all other organisms, the natural system +must be regarded as the goal of systematic classification, our phylogenetic +knowledge of the Radiolaria is too fragmentary and inadequate to admit of +the systematic arrangement here adopted being regarded as a thoroughly +consistent natural system, that is, as representing the true genealogical +tree of the class. Owing, however, to the extraordinary variety of form of +the Radiolaria, and the complicated relationships of the larger and smaller +groups, a synoptical grouping of the different categories and the erection +of a complete, even if to some extent artificial, system, becomes a logical +necessity. Under these circumstances, and regard being had to both these +conditions, the following systematic treatment of the Radiolaria will +appear as a _compromise between the natural and artificial systems_, like +all other zoological and botanical classificatory attempts. On the one +hand, the attempt is made to arrange the larger and smaller groups as +nearly as possible according to their phylogenetic relationships, whilst, +on the other hand, the practice of circumscribing each by a definition as +clear and logical as possible has been carried out. Since these two efforts +naturally often come into contact, the insufficiency of many parts of the +arrangement is obvious, hence its hypothetical and provisional character is +emphatically stated. + + +155. _Systematic Categories._--The categories or different orders of +divisions have in the Radiolaria, as in all other organisms, no _absolute_ +significance, but only a _relative_ value. In itself it is quite +unimportant whether the whole group be regarded, as at first, as a _family_ +(Ehrenberg, 1847), or as an _order_ (J. Mueller, 1858), or as a _class_ +(Haeckel, {cii}1881). These different views are regulated, on the one hand, +by the known extent of the group and by the amount of our acquaintance with +it, and on the other, by comparison with related groups and by reference to +their conventional disposition. When, therefore, the whole class, +Radiolaria, is here divided into two subclasses, four legions, eight +orders, eighty-five families, &c., these artificial categories are drawn up +only in the conviction that by this means the easiest survey and most +thorough insight into the system as a whole may be attained; this latter +will indeed approach as far as possible the ideal of a natural system, but +must on numerous practical grounds always remain more or less artificial. +Since it is to be expected that with the progress of our systematic +knowledge the rank of the various categories will rise, it is possible that +in the future the arrangement of the group may be somewhat as +follows:--_Phylum_, RADIOLARIA; _Four Classes_, SPUMELLARIA, NASSELLARIA, +ACANTHARIA, PHAEODARIA; _Eight Legions_ (Nos. I.-VIII. in the following +Table); _Twenty Orders_ (Nos. 1-20 in the Table), &c. + + Four Legions. Eight Sublegions. Twenty Orders. Typical Families. + { {1. Colloidea, { 1a. Thalassicollida. + {I. COLLODARIA { { 1b. Collozoida. + { (Spumellaria { + { palliata) {2. Beloidea, { 2a. Thalassosphaerida. + { { { 2b. Sphaerozoida. + I. Legion { + (or Subclass){ { { 3a. Ethmosphaerida. + SPUMELLARIA { {3. Sphaeroidea, { 3b. Collosphaerida. + (PERIPYLEA) { { + { {4. Prunoidea, { 4a. Ellipsida. + [Porulosa {II. SPHAERELLARIA { { 4b. Zygartida. + peripylea.] { (Spumellaria { + { loricata) {5. Discoidea, { 5a. Phacodiscida. + { { { 5b. Porodiscida. + { { + { {6. Larcoidea, { 6a. Larnacida. + { { { 6b. Pylonida. + + { {7. Actinelida, { 7a. Astrolophida. + { { { 7b. Litholophida. + {III. ACANTHOMETRA { { 7c. Chiastolida. + { (Acantharia { + II. Legion { palliata) { { 8a. Astrolonchida. + (or Subclass){ {8. Acanthonida, { 8b. Quadrilonchida. + ACANTHARIA { { { 8c. Amphilonchida. + (ACTIPYLEA) { + { { { 9a. Sphaerocapsida. + [Porulosa { {9. Sphaerophracta,{ 9b. Dorataspida. + actipylea.] {IV. ACANTHOPHRACTA { { 9c. Phractopeltida. + { (Acantharia { + { loricata) { {10a. Belonaspida. + { {10. Prunophracta, {10b. Hexalaspida. + { { {10c. Diploconida. + { {11. Nassoidea, 11. Nassellida. + { { + {V. PLECTELLARIA {12. Plectoidea, {12a. Plagonida. + { (Nassellaria { {12b. Plectanida. + { palliata) { + { {13. Stephoidea, {13a. Stephanida. + { { {13b. Tympanida. + { + III. Legion { {14. Spyroidea, {14a. Zygospyrida. + (or Subclass){ { {14b. Androspyrida. + Nassellaria { { + (MONOPYLEA) { { {15a. Cannobotryida. + {VI. CYRTELLARIA {15. Botryodea, {15b. Lithobotryida. + [Osculosa { (Nassellaria { {15c. Pylobotryida. + monopylea.] { loricata) { + { { {16a. Monocyrtida. + { {16. Cyrtoidea, {16b. Dicyrtida. + { { {16c. Tricyrtida. + { { {16d. Stichocyrtida. + + { { {17a. Phaeodinida. + { {17. Phaeocystina, {17b. Cannorrhaphida. + { { {17c. Aulacanthida. + {VII. PHAEOCYSTINA { + IV. Legion { (Phaeodaria { {18a. Orosphaerida. + (or Subclass){ palliata) {18. Phaeosphaeria,{18b. Aulosphaerida. + Phaeodaria { { {18c. Cannosphaerida. + (CANNOPYLEA).{ + { { {19a. Challengerida. + [Osculosa { {19. Phaeogromia, {19b. Castanellida. + cannopylea.]{VIII. PHAEOCOSCINA { {19c. Circoporida. + { (Phaeodaria { + { loricata) { {20a. Concharida. + { {20. Phaeoconchia, {20b. Coelodendrida. + { { {20c. Coelographida. + + +156. _Formation of Species._--The totality of similar forms, which we unite +in one species, and which in the earlier dogmatic systems was regarded as a +category of absolute value, possesses only a _relative value_ like all +other systematic categories (s 155). According to the individual views of +the systematist and the general survey which he has attained of the smaller +and larger systematic groups, the conception of a species adopted in his +practical work will be wider or narrower. In the present systematic +arrangement a medium extent has been adopted. It is shown that in the +Radiolaria, as in all other extensive groups of organisms, the constancy of +the species is very variable in the different groups. Many families of +Radiolaria are very rich in "bad species," _i.e._, very _variable_ forms, +in which the process of the formation of species is seen in progress; such, +for example, are--among the SPUMELLARIA, the Sphaerozoida, Stylosphaerida, +Phacodiscida and Pylonida; among the ACANTHARIA, the Amphilonchida and +Phractopeltida; among the NASSELLARIA, the #Stephoidea# and #Botryodea#; +and among the PHAEODARIA, the Aulacanthida, Sagosphaerida, Castanellida and +Concharida. On the {civ}other hand, in some families numerous "good +species" may be distinguished, since the intermediate connecting forms are +no longer present and the forms have become _relatively constant_. As +instances of such families may be mentioned, among the SPUMELLARIA, the +Astrosphaerida, Cyphinida, Porodiscida and Tholonida; among the ACANTHARIA +the Quadrilonchida and Dorataspida; among the NASSELLARIA, the #Spyroidea# +and #Cyrtoidea#; among the PHAEODARIA, the Challengerida, Medusettida, +Circoporida and Coelographida. The more carefully the different groups are +studied, the more numerous the individuals of each species under +comparison, the greater becomes the number of "bad" species among the +Radiolaria, and the smaller the number of good ones. Originally, no doubt, +all "species bonae" were "malae." There may be observed in the manifold +skeletal forms of the Radiolaria, on the one hand, the utmost accuracy of +configuration, and on the other, the greatest variability, and hence a +careful comparative study of them leads to a firm conviction of the gradual +"Transformation of Species," and of the truth of the "Theory of Descent." + + +157. _Palaeontological Development._--The palaeontology of the Radiolaria +already offers very considerable material for study; but in consequence of +its incompleteness this is of little value for the study of the phylogeny +of the class. By far the larger portion of the fossil Radiolaria belong to +the Tertiary period; only quite recently have numerous well-preserved +fossil Radiolaria been described from the Mesozoic period, and especially +from the Jura. Of Palaeozoic Radiolaria (from the coal measures) only +slight traces are known. Moreover, the fossil Radiolaria hitherto known +have been found only in very circumscribed and widely separated localities. +The majority of all the species belong to the small island of Barbados. +Although our palaeontological acquaintance with the Radiolaria must +necessarily be incomplete for this reason, it is still more so since at +least thirty out of the eighty-five families (that is more than a third) +could not possibly leave any fossil remains, either because they possess no +skeleton, or because of its chemical composition. + + Of the four legions of the Radiolaria, the ACANTHARIA (on account of the + solubility of their astroid acanthin skeletons) have entirely vanished + and have never been found fossil. Of the PHAEODARIA, whose silicate + skeleton is not as a rule capable of fossilisation, only one section + (Dictyochida) of a single family (Cannorrhaphida) has been observed + fossil. Hence the fossil remains of the Radiolaria belong almost + exclusively to the two legions, SPUMELLARIA and NASSELLARIA, which were + formerly united under the term "Polycystina." Among these, however, the + skeletonless Thalassicollida, Collozoida, and Nassellida could leave no + traces. Hence there only remain fifty-five families of which we might + expect to find fossil siliceous skeletons. Even of these, however, + scarcely the half are certainly known in the fossil condition, whilst of + the remainder nothing certain is known; for example, of the large order + #Larcoidea# (among the SPUMELLARIA) and of the #Stephoidea# (among the + NASSELLARIA) with a few isolated exceptions, no fossils are known. The + great majority of fossil Radiolaria belong to the two NASSELLARIAN orders + #Cyrtoidea# and #Spyroidea# (two relatively very highly developed + groups); next to these follow the orders {cv}#Discoidea# and + #Sphaeroidea# among the SPUMELLARIA. From these palaeontological facts it + is obvious that our present very incomplete acquaintance with the fossil + Radiolaria is quite insufficient to warrant us in drawing any conclusions + from it regarding the phylogenetic development or palaeontological + succession of the individual groups. + + +158. _Origin of the Four Legions._--The agreement of all Radiolaria in +those constant and essential characters of the unicellular body, which +distinguish them from all other Protista (especially the differentiation of +the malacoma into a central capsule and extracapsulum), justifies the +conclusion that all members of this class have been developed from a common +undifferentiated stem-form. Only the simplest form of the SPUMELLARIA, a +skeletonless spherical cell with concentric spherical nucleus and calymma, +can be regarded as such. The simplest form of the Thalassicollida which is +now extant (_Actissa_, _Procyttarium_, p. 12), corresponds so exactly to +the morphological idea of that hypothetical stem-form that it may +unhesitatingly be regarded in a natural system as the common point of +origin of the whole class. On the other hand, _Actissa_ is so closely +related to the simple Heliozoa (_Actinophrys_, _Actinosphaerium_, +_Heterophrys_, _Sphaerastrum_, &c.) that its origin from this group of +Rhizopoda is exceedingly probable. The three legions ACANTHARIA, +NASSELLARIA, and PHAEODARIA are to be regarded as three main diverging +branches of the genealogical tree, which have been developed in different +directions and are only connected by their simplest stem-forms +(_Actinelius_, _Nassella_, _Phaeodina_) with the stem-form of the +SPUMELLARIA, the primordial _Actissa_. + + +159. _Phylogeny of the Spumellaria._--The legion SPUMELLARIA or PERIPYLEA +is to be regarded as the common stem-group of the Radiolaria, and its +simplest form, _Actissa_, as the primitive genus or radical form of the +whole class; for it possesses in the simplest and most undifferentiated +form all those characters by which the Radiolaria are distinguished from +other Protista; all the other genera of the class may be derived from it by +successive modifications. Considered as a legion the whole group +SPUMELLARIA is undoubtedly monophyletic, for all its members possess those +essential characters by which it is distinctively marked off from the other +three legions, more especially a simple capsule-membrane, which is +everywhere evenly perforated by innumerable small pores; the nucleus lies +originally in the centre of the spherical central capsule. Furthermore, all +SPUMELLARIA lack those positive characters which distinguish the three +remaining legions--the centrogenous acanthin skeleton of the ACANTHARIA, +the basal porochora and the monaxon podoconus of the NASSELLARIA, the +astropyle and phaeodium of the PHAEODARIA. + + +160. _Origin of the Spumellaria._--The genus _Actissa_ (p. 12, Pl. 1, fig. +1) presents the Radiolarian type in its simplest and most primitive form--a +spherical central capsule, which encloses in its middle a spherical +nucleus, and which is surrounded by a spherical calymma. The whole +unicellular body consists, therefore, of three concentric spheres, {cvi}and +possesses neither skeleton nor alveoles, nor other differentiated parts. +The innumerable fine pseudopodia, which issue from the central capsule +through the evenly distributed pores in its membrane, radiate in all +directions through the calymma and pass out over its surface. _Actissa_ +can, therefore, be directly derived phylogenetically from the simplest +skeletonless Heliozoa (_Actinophrys_, _Heterophrys_, _Actinosphaerium_, +_Sphaerastrum_). The only essential difference between the two consists in +the development of the _central capsule_, which in _Actissa_ separates as a +distinct membrane the endoplasm from the exoplasm. This differentiation +which we regard is the most important distinguishing character of the +Radiolaria, has been transmitted by inheritance, along with the formation +of flagellate spores in the central capsule, from _Actissa_, the primitive +parent to all the other Radiolaria. + +{cvii}161. _Hypothetical Genealogical Tree of the Spumellaria_:-- + + + LARCOIDEA DISCOIDEA + ~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~~~~ + Streblonida PHACODISCARIA + | Coccodiscida + | THOLONIDA | + | | | + PRUNOIDEA | | | + ~~~~~~~~~~~~~~~~~~ Soreumida| | | + | | | | + Zygartida | | | | + | | | | | + | | |Zonarida| | + | |Lithelida| | SPHAEROIDEA |CYCLODISCARIA + | | | | |~~~~~~~~~~~~~ | Spongodiscida + | | | | |Stylosphaerida|Pylodiscida| + | Phorticida| | | | | | | + | | | | | | | | | + Panartida | | | | | | | | + | Artiscida| +----+---+ | | | | + | | | | | | | | + | | | | | Phacodiscida| | + |Spongodruppida | | | | | | | + | | | | | Staurosphaerida| +-----+ + | | | | Pylonida | | | + | | | | | | | | + Cyphinida | | +---------+ | | | + | | | | | | Porodiscida + | | | |Astrosphaerida| | | + +-----+ | | | | | | + | | | | | Cenodiscida | + |Spongellipsida| Larnacida | | | | + | | | | | | | Archidiscida + | | | | |Cubosphaerida | | + Druppulida | | | | | +--------+ + | | | | | | | + | | | | | |Collosphaerida| + | | | | | | | | + | | | LARNACILLA +-----+-----+ | + | | | (Trizonium) | | + | Spongurida | | | | + +------+-------+ | | | + | | | | + Ellipsida Larcarida Liosphaerida Cenodiscida + (CENELLIPSIS) (CENOLARCUS) (CENOSPHAERA) (CENODISCUS) + | | | | + [Actiprunum?] [Actilarcus?] [Procyttarium] [Actidiscus?] + | | | | + +---------------+------+-------+--------------+ + | + CENOSPHAERA (Common stem-form of all Sphaerellaria?) + | | + | | POLYCYTTARIA + | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + |Collosphaerida Collozoida Sphaerozoida } + | | | | } BELOIDEA + +-----+ | Thalassosphaerida } + | | | + Ethmosphaerida | | + | | | + +----------------+----------+ + | + COLLOIDEA + | + Thalassicollida + | + ACTISSA + + +{cviii}162. _Collodaria and Sphaerellaria._--Whilst in all SPUMELLARIA the +malacoma agrees in possessing the characteristic features of the legion, +and thus justifies its derivation monophyletically from the common +stem-form _Actissa_, the different forms of skeleton, on the other hand, +cannot all be referred to the same fundamental form. More especially the +_spherical lattice-shell_, from which all the numerous skeletal forms of +the #Sphaerellaria# may be derived, cannot have arisen from the incomplete +Beloid skeleton which characterises the #Beloidea# among the #Collodaria#. +It is probable rather that the formation of the skeleton has taken place +independently in those two groups of SPUMELLARIA. From the skeletonless +#Colloidea#, as the common stem-group of the SPUMELLARIA, two different +main groups have diverged, on the one hand the #Beloidea#, whose skeleton +consists of separate spicules scattered in the extracapsulum, and on the +other hand, the #Sphaerellaria#, which have formed a simple lattice-sphere +around the central capsule; from this the manifold forms of the remaining +SPUMELLARIA may be derived. + + +163. _Descent of the Sphaerellaria._--The extensive order #Sphaerellaria#, +which includes all SPUMELLARIA with a complete lattice-shell, develops an +extraordinary variety of skeletal structures; these may, nevertheless, all +be derived without violence from a common stem-form, or simple spherical +lattice-shell, _Cenosphaera_. The main stem of the order, the extensive +suborder #Sphaeroidea# (Pls. 5-30), is derived immediately from +_Cenosphaera_ (p. 61, Pl. 12); three diverging branches of it being +represented by the other three suborders, the #Prunoidea# (Pls. 16, 17, 39, +40) being developed by elongation, and the #Discoidea# (Pls. 31-48) by +shortening of the vertical main axis, whilst the #Larcoidea# (Pls. 9, 10, +49, 50) have originated by the modification of the spherical lattice-shell +into a lentelliptical or triaxial ellipsoidal one. Although the +monophyletic derivation of all #Sphaerellaria# from _Cenosphaera_ is +exceedingly probable, the possibility of a polyphyletic origin for the +group is by no means excluded. For even in the skeletonless primitive genus +of all the SPUMELLARIA, _Actissa_ (as well as in the social _Collozoum_), +there are found, in addition to the usual spherical types, other species +(or subgenera, p. 12) whose central capsule is not spherical but a +modification of the sphere; in _Actiprunum_ ellipsoidal; in _Actidiscus_ +lenticular; in _Actilarcus_ lentelliptical; if such modified forms of +_Actissa_ were to develop their lattice-shells independently, then their +form would correspond to that of the central capsule; and such simple +ellipsoidal, discoidal, and lentelliptical lattice-shells might have been +the primitive forms of the #Prunoidea#, #Discoidea# and #Larcoidea#. + + +164. _Genealogical Tree of the Sphaeroidea._--_Cenosphaera_, the simplest +form of the spherical lattice-shell, may be unhesitatingly regarded as the +common stem-form of all the #Sphaeroidea# (pp. 50-284, Pls. 5-30). +_Cenosphaera_ (p. 61, Pl. 12) arose directly from _Actissa_ simply by the +silicification of the spherical exoplasmatic network of the sarcodictyum +around the central capsule, on the surface of the concentric calymma. From +this simple siliceous extracapsular lattice-sphere all other forms of +#Sphaeroidea# have arisen, in the main by the manifold combination of two +simple processes, first by the formation of radial spines on the surface of +the lattice-sphere, and second, the addition of concentric spherical +lattice-shells. Both processes may be utilised as the foundation for a +systematic treatment of the #Sphaeroidea# (compare pp. 52-58). + + If in the #Sphaeroidea# the characteristic number and disposition of the + _radial spines_ be regarded as the most important heritable peculiarity + of the different families, then we have the following natural + arrangement:--(1) Liosphaerida, without radial spines; (2) Cubosphaerida, + with six radial spines (opposite in pairs in three axes perpendicular to + each other); (3) Staurosphaerida, with four radial spines (in two axes + crossed at right angles); (4) Stylosphaerida, with two opposite radial + spines (in the vertical main axis); and (5) Astrosphaerida, with numerous + regularly or irregularly distributed radial spines (eight to twenty or + more). If, on the contrary, more stress be laid upon the number of the + concentric lattice-shells, then we have the following artificial + grouping:--(1) Monosphaerida, with one simple lattice-sphere; (2) + Dyosphaerida, with two concentric lattice-spheres; (3) Triosphaerida, + with three; (4) Tetrasphaerida, with four; (5) Polysphaerida, with + numerous (five to twenty or more) concentric lattice-shells; (6) + Spongosphaerida, with a spongy spherical shell. In general the former + arrangement appears more natural than the latter, since the number of + primary radial spines, which grow out from the primary lattice-sphere, + determines their ground-form from the outset, whatever may be the number + of secondarily added shells. Strictly speaking, according to the view + adopted, these Liosphaerida which have several shells, on the outer + surface of which there are no radial spines, ought to be classified + according to the number and arrangement of their internal radial + connecting beams and distributed among the other families. The practical + application of this correct principle meets, however, with great + difficulties. Also in many cases the phylogenetic relations of the + different #Sphaeroidea# are more complicated than would appear from both + these classificatory principles. In general their phylogeny will quite + correspond with their ontogeny, since from the innermost first formed + {cix}lattice-shell (primary medullary shell) a number of radial spines + arises, and upon these the secondary shells are formed from within + outwards. + + +165. _Genealogical Tree of the Prunoidea._--The suborder #Prunoidea# is +very closely related to the #Sphaeroidea#, and is distinguished from it by +the elongation of one axis; from the simple lattice-sphere (_Cenosphaera_) +is developed a latticed ellipsoid (_Cenellipsis_, Pl. 39, fig. 1). The +development of this vertical isopolar main axis is foreshadowed even among +the #Sphaeroidea#, in that family in which two opposite radial spines grow +out of the primary lattice-sphere at the two poles of the vertical main +axis (Stylosphaerida, Pls. 13, 14). These latter pass over without any +sharp boundary into those forms of #Prunoidea# whose ellipsoidal +lattice-shell bears two opposite main-spines (Stylatractida, Pls. 15, 16). +Other very intimate relationships between the #Sphaeroidea# and #Prunoidea# +are indicated in certain of the latter by the fact that of the two +concentric lattice-shells the inner (medullary) shell is spherical, the +outer (cortical) shell ellipsoidal (Pl. 39, figs. 3, 7, 8, 14, 19); often +three concentric lattice-shells are present, of which the two inner are +spherical intracapsular medullary shells, whilst the outer is an +extracapsular cortical shell, ellipsoidal or cylindrical in form (Pl. 39, +figs. 4, 12, 17, 18). Owing to the manifold nature of these phylogenetical +relations and the variety of their combinations, the derivation of the +individual #Prunoidea# from the #Sphaeroidea# is rendered very difficult; +in addition to which it is possible that the simplest #Prunoidea# +(_Cenellipsis_, _Ellipsidium_) have been directly developed from the +skeletonless _Actiprunum_ (a form of _Actissa_ with ellipsoidal central +capsule, p. 14) by the excretion of a simple ellipsoidal lattice-shell on +the surface of their calymma. + + The phylogeny of the #Prunoidea# is especially complicated by the + formation of peculiar transverse constrictions, perpendicular to the + longitudinal axis. They are wanting only in the Monoprunida (Ellipsida, + Druppulida, and Spongurida); the Dyoprunida (Artiscida and Cyphinida, Pl. + 39, figs. 9-19) possess only one such constriction (in the equatorial + plane); the Polyprunida, on the other hand, have three, five, or more + parallel constrictions (Panartida and Zygartida, Pl. 40). The chambers, + which are separated off by these constrictions, may be regarded as polar + sections of incomplete cortical shells. + + +166. _Genealogical Tree of the Discoidea._--The suborder #Discoidea# is +closely related to the #Sphaeroidea#, but separated from it by shortening +of one axis; from a simple lattice-sphere (_Cenosphaera_) a latticed lens +or flattened spheroid is developed, whose circular equatorial plane is +larger than any other section (_Cenodiscus_, Pl. 48, fig. 1). The formation +of this horizontal equatorial plane is perhaps indicated in that family of +#Sphaeroidea# in which four crossed radial spines, lying in one plane, are +developed (Staurosphaerida, Pls. 15, 31, 42). The morphological and +phylogenetical relations of the #Discoidea# to the #Sphaeroidea# are +precisely the converse of those of the #Prunoidea#; in the latter the +vertical axis appears longer, in the former shorter than any {cx}other axis +of the body. The #Discoidea# are probably polyphyletic, having originated +from several different groups of #Sphaeroidea#; at least two essentially +different main groups may be distinguished among them; of these the one is +characterised by the formation of a large extracapsular lenticular cortical +shell (Phacodiscaria), whilst in the other this typical "Phacoid shell" or +lattice-lens is wanting (Cyclodiscaria, compare pp. 403-409). + + The Phacodiscida (Pls. 31-35) perhaps constitute the primitive group of + the Phacodiscaria, their lenticular or Phacoid cortical shell being + connected by radial bars with one or two concentric spherical medullary + shells; they may have originated directly from the Dyosphaerida or + Triosphaerida by flattening of the spheroidal cortical shell. From the + Phacodiscida the Cenodiscida (if indeed they be not the primitive + stem-form) have been developed by retrogression and loss of those + medullary shells. The Coccodiscida (Pls. 36-38), on the other hand, have + been developed from the Phacodiscida by the addition of concentric rings + of chambers, which may be regarded as incomplete cortical shells, only + the equatorial portion of which is developed. Perhaps the Porodiscida, + the primitive group of the Cyclodiscaria, have arisen in a similar way; + they lack, however, the typical Phacoid shell, the concentric rings of + chambers being directly applied to a small spherical medullary shell in + the equatorial plane (Pls. 41-46). If those rings from the commencement + be interrupted by three interradial gaps (gates) the family Pylodiscida + arises (Pl. 38, figs. 6-20). If, on the contrary, the concentric radially + divided chambers of the Porodiscida become quite irregular and spongy, + they pass over into the Spongodiscida (Pls. 46, 47). It is not, however, + impossible that part of the #Discoidea# (especially the Cenodiscida) have + originated directly from skeletonless #Collodaria# with a lenticular + central capsule, such as are found in a subgenus of _Actissa_ + (_Actidiscus_, p. 15). + + +167. _Genealogical Tree of the Larcoidea._--The suborder #Larcoidea# +presents in the structure, composition, and development of its variously +formed lattice-shells much more complicated relations than the other +#Sphaerellaria#; it is essentially distinguished from them by the +characteristic ground-form of its lattice-shells, which is a "lentellipsis" +or a triaxial ellipsoid (also the ground-form of the rhombic +crystallographic system, the rhombic octahedron). Hence all parts of the +body are regularly disposed with respect to three different dimensive axes; +all three axes, perpendicular one to another, are isopolar but of different +lengths; the longest is the vertical main axis, the mean the horizontal +frontal axis, the shortest the horizontal sagittal axis. In the great +majority of the #Larcoidea# the lentelliptical ground-form is indicated in +the central capsule, even when it is not at once obvious in the skeleton. +Since such lentelliptical central capsules are developed even in _Actissa_ +(_Actilarcus_, p. 16), it is possible that the simplest #Larcoidea# may +have arisen directly from these by deposition of a simple lentelliptical +lattice-shell in the sarcodictyum, on the surface of the calymma +(_Cenolarcus_, Pl. 50, fig. 7). It is more probable, however, that these +simplest forms (_Cenolarcus_, _Larcarium_) have been developed from the +simplest #Sphaeroidea# (_Cenosphaera_), by the spherical body growing +unequally in the three dimensions of space. It appears especially likely +{cxi}from a study of the concentrically disposed lattice-shells of some +#Larcoidea# (_Coccolarcus_, _Larcidium_, Pl. 50, fig. 8), in which the +inner medullary shell is spherical, the outer cortical shell more or less +elliptical. In the great majority of #Larcoidea# the latter arises in quite +a peculiar manner, three broad lattice-zones, which are developed in three +planes at right angles to each other, growing out from a small spherical or +lentelliptical medullary shell, _Trizonium_, _Larnacilla_ (compare pp. 600, +615, 628, &c.). + + The trizonal _Larnacilla_-shell commences by the formation of a + transverse girdle, by the union of two lateral latticed processes, which + spring right and left in the equatorial plane from the poles of the + frontal axis of a lentelliptical medullary shell (_Monozonium_, p. 633, + Pl. 9, fig. 1). This is followed by a second lateral girdle, which lies + in the frontal plane and proceeds from its lateral poles (_Dizonium_, p. + 634, Pl. 9, figs. 2, 3). Finally the sagittal girdle is formed, lying in + the sagittal plane and arising from the lateral girdle on the two poles + of the main axis (_Trizonium_, p. 637, Pl. 9, fig. 4). Whilst the gaps + between the three zones of this trizonal shell remain open in the + Pylonida, in _Larnacilla_, the important primitive form of the Larnacida, + they are closed by lattice-work (Pl. 50, figs. 3-8). From this trizonal + _Larnacilla_-shell the great majority of Larcoid shells may be derived. + Such a system of zones may be repeated (Diplozonaria) or even developed a + third time (Triplozonaria, p. 632). In most #Larcoidea# the zones are + secondarily connected by lattice-work. In the Tholonida (Pl. 10) each of + the two opposite latticed wings of a zone becomes a closed dome. In the + Zonarida (Pl. 50, figs. 9-12) these domes are partially or wholly + bisected by constrictions or latticed septa which are developed in the + three dimensive planes. The Lithelida (Pl. 49, figs. 1-7) are + characterised by the fact that one of each pair of opposite latticed + processes (or half zones) grows more strongly than the other, and that + the larger completely embraces the smaller so as to form a complicated + spiral. Whilst in this case the spiral lies in a plane, in the + Streblonida (Pl. 49, figs. 8, 9) it becomes turbinoid like a gastropod + shell and forms an ascending spiral. Finally, two small families of + #Larcoidea# are characterised by quite irregular growth (a very rare + occurrence among the Radiolaria); these are the simple-chambered + Phorticida (Pl. 49, figs. 10, 11) and the many chambered Soreumida (Pl. + 49, figs. 12, 13). The phylogenetic relationship of these families of + #Larcoidea# is probably very complicated and demands closer investigation + (compare pp. 599-604). + + +168. _Descent of the Polycyttaria._--The polyzootic or colonial Radiolaria, +which we unite in the group Polycyttaria (sometimes known as +"Sphaerozoea"), belong without doubt to the legion SPUMELLARIA, for they +possess all the peculiarities by which these PERIPYLEA are distinguished +from the other legions of the Radiolaria. Only the morphological position +of the Polycyttaria in that legion, and their phylogenetic relation to the +monozootic or solitary SPUMELLARIA, can be variously interpreted. The three +families which we distinguish among the Polycyttaria are so closely related +to three different families of the Monocyttaria, that they may be directly +derived from them by the formation of colonies. According to this +_triphyletic hypothesis_ the social skeletonless Collozoida (Pl. 3) would +be descended from the solitary Thalassicollida (Pl. 1), the polyzootic +Sphaerozoida with a Beloid skeleton (Pl. 4) from the monozootic +{cxii}Thalassosphaerida (Pl. 2), and the colonial Collosphaerida with a +Sphaeroid skeleton (Pls. 5-8) from the solitary Ethmosphaerida (Pl. 12, +&c.). Many species of monozootic and polyzootic forms in all three groups +are so alike that they can only be distinguished by the fact that the one +series are colonial, the others solitary. On the other hand, there are some +reasons which would justify a monophyletic hypothesis for the Polycyttaria, +_e.g._, the precocious nuclear division; in this case it would be most +natural to hold that the Sphaerozoida and Collosphaerida have arisen as two +diverging branches from the Collozoida, whilst the latter are nothing else +than colonial Thalassicollida. + + +169. _Phylogeny of the Acantharia._--The legion ACANTHARIA or ACTIPYLEA is +distinguished by its peculiar acanthin skeleton, which develops +centrogenously, as well as by the disposition in groups of the pores in its +central capsule, and its excentric usually precocious nucleus; it is thus +so different from all other Radiolaria as undoubtedly to furnish, +phylogenetically considered, an independent stem (s 7). This stem is only +connected at the root by _Actinelius_ with the primitive form of the +SPUMELLARIA, _Actissa_. The stem is monophyletic, since all the forms +belonging to it may be derived without violence from _Actinelius_ as a +common primitive form. + + +170. _Origin of the Acantharia._--The genus _Actinelius_ (p. 730, Pl. 129, +fig. 1), which may naturally be regarded as the common primitive form of +all ACANTHARIA, possesses a spherical central capsule, which in consequence +of the early division of the nucleus (s 63), encloses numerous small +nuclei; from its centre arise many simple radial spines of equal size, +which penetrate the central capsule. A large number of radial pseudopodia +issue between the spines from the sarcomatrix which surrounds the capsule. +_Actinelius_ may have been directly derived from _Actissa_, the common +stem-form of all Radiolaria, by the division of the pseudopodia into two +groups, myxopodia, which remained soft, and axopodia, which became firm (s +95A). As the latter became changed into strong acanthin rods, and touched +each other in the centre, they forced the nucleus from its originally +central position and brought about its early division. _Actinelius_ is also +of all Radiolaria the form which, next to _Actissa_, most nearly approaches +the Heliozoa. If the stiff axial threads of _Actinosphaerium_ be conceived +of as partially converted into acanthin spines, and its nucleated medullary +substance as separated from the alveolar cortical layer by a membrane +(central capsule), then _Actinelius_ would be produced. + + +{cxiii}171. _Hypothetical Genealogical Tree of the Acantharia_:-- + + Diploconida + | + | + Phractopeltida Hexalaspida Cenocapsida + | | | + | Phatnaspida | Lychnaspida | + | | | | | + | | | | Porocapsida + | | Coleaspida | | + | | | | | + | Ceriaspida +-----+-----+ | | + | | | | | + +--+--+ | | | + | Belonaspida | | + | | | | + Phractaspida | Stauraspida | + | | | | + | | | Astrocapsida + | | | Sphaerocapsida + +-------+----------+ ------+------ | + | | | + Diporaspida Tessaraspida | + (Dorataspida dipora) (Dorataspida tetrapora) | + | | | | | + | +--------+--------+ | | + | | | | + | [Dorataspida] | | + | | | + | | | + | Quadrilonchida | | + | | | | + Phractacanthida | Stauracanthida | + | | | | + | Amphilonchida | +--+--+ + | | | | + | | | Acanthonia + | | | | + +---------+--------+--+------------------+ + | + Astrolonchida + | + Litholophida | Chiastolida + | | | + | Zygacanthida | + | Acanthonida Actinastrum + | Acanthometron | + Astrolophida | | | Acanthochiasmida + | | | | | + | | | | Acanthometron + | | | | | + +----------+-----------------+-------------------+---------+ + | + Actinelida + Actinelius + | + | + Actissa + + +{cxiv}172. _Adelacantha and Icosacantha._--The numerous forms of +ACANTHARIA, here disposed in twelve families and sixty-five genera, may be +divided phylogenetically into two main groups of very different +extent--_Adelacantha_ and _Icosacantha_. The more primitive group, +_Adelacantha_, have an indefinite and variable number of radial spines, +which are always quite simple in form and usually irregularly distributed; +this main division includes only the one order #Actinelida#, with six +genera, among which is _Actinelius_, the common stem-form of all the +ACANTHARIA. The more recent group, Icosacantha, includes all the other +ACANTHARIA (fifty-nine genera), and is very markedly distinguished from the +Adelacantha by the fact that the radial spines are always twenty in number, +and arranged according to Mueller's law (compare pp. 717-725, and s 110). +Since this regular disposition (in five alternating zones each of four +spines) has been retained by inheritance in the whole of the Icosacantha, +it is probable that this large group has been developed monophyletically +from a twig of the Adelacantha; _Actinastrum_ (p. 732) and _Chiastolus_ (p. +738) still present connecting links between the former and the latter, +between _Actinelius_ and _Acanthometron_. + + +173. _Acanthonida and Acanthophracta._--The extensive main division +Icosacantha (s 110), which embraces all ACANTHARIA with twenty radial +spines, disposed according to Mueller's law, may be subdivided into two +large groups or orders:--the #Acanthonida# (p. 740, Pls. 130-132) and the +#Acanthophracta# (p. 791, Pls. 133-140). The latter possess a complete +extracapsular lattice-shell, which the former have not. The more recent +#Acanthophracta# may be derived phylogenetically from the more primitive +#Acanthonida# simply by the development of this lattice-shell, with which +process are usually (perhaps always) connected certain alterations in the +malacoma, _e.g._, degeneration of the myophriscs (s 96). The most primitive +form of all Icosacantha is the genus _Acanthometron_ (p. 324), in which all +the twenty acanthin spines are of the simplest constitution and of equal +dimensions. + + +174. _Differentiation of the Acanthonida._--The order #Acanthonida#, which +embraces all Icosacantha which have no complete lattice-shell, divides +early into three main branches, the three families Astrolonchida, +Quadrilonchida, and Amphilonchida (p. 727, Pls. 130-132). The first of +these constitutes the common stem-group from which the other two as well as +the whole group #Acanthophracta# have been developed; the common stem-form +of all is _Acanthometron_ (s 173). All the Astrolonchida (p. 740, Pl. 130) +have twenty radial spines of equal size and similar form. On the other +hand, in the Quadrilonchida (p. 766, Pl. 131) the four equatorial spines +differ from the others in size and sometimes also in form. In the +Amphilonchida (p. 781, Pl. 132) two opposite equatorial spines (lying in +the hydrotomical axis) are much larger than the other eighteen and of a +different shape. Of the three families of the #Acanthonida# the most +important is the primitive group Astrolonchida, for from this the various +stem-forms of the #Acanthophracta# arise. They are subdivided according to +the formation of the spines into three subfamilies: the Zygacanthida, with +simple spines without apophyses (or transverse processes); the +Phractacanthida, with two opposite apophyses on each radial {cxv}spine, and +the Stauracanthida, with four crossed apophyses on each radial spine. The +three genera of the Zygacanthida represent the stem-forms of the three +families, since the radial spines in _Acanthometron_ (the most primitive +form of #Acanthonida#) are cylindrical, in _Zygacantha_ two-edged, and in +_Acanthonia_ four-edged (p. 741). + + +175. _Capsophracta and Cladophracta._--The extensive order +#Acanthophracta#, which embraces all ACANTHARIA with a complete +lattice-shell, is polyphyletic, its main subdivisions have been developed +independently from different branches of the #Acanthonida#. The whole order +may be divided directly into two main groups, the #Capsophracta# and +#Cladophracta# (p. 793), which differ in the structure and the origin of +their lattice-shell. The group (or suborder) #Capsophracta# includes only +the single family Sphaerocapsida (p. 795, Pl. 133, figs. 7-11; Pl. 135, +figs. 6-10); the lattice-shell arises independently of the twenty radial +spines, being made up like a pavement of innumerable small acanthin plates, +united by a kind of cement; each plate being perforated by a fine pore. In +addition twenty larger main pores (or groups of four pores each) are +present, corresponding to the twenty radial spines; these are always equal, +quadrangular prismatic, without transverse processes as in _Acanthonia_. In +the #Cladophracta#, which include the five remaining families of the +#Acanthophracta#, the structure and origin of the lattice-shell are quite +different; the lattice-shell is here made up of the branches of the +transverse processes, which radiate tangentially from the twenty radial +spines and are only united secondarily. + + +176. _Ascent of the Dorataspida._--The group #Cladophracta#, or those +ACANTHARIA whose lattice-shell arises by the union of transverse +processes of the twenty radial spines, includes five different +families, whose stem-group is the family Dorataspida, with a simple +spherical lattice-shell. This family itself is, however, diphyletic in +origin, being composed of two essentially and originally different +subfamilies--Diporaspida and Tessaraspida (p. 803). The Diporaspida (p. +808, Pls. 137, 138) have been developed from the Phractacanthida, and as +each radial spine of the latter bears two opposite apophyses, so the +lattice-shell of the former has forty primary aspinal pores (two on the +base of each spine). On the other hand, the Tessaraspida (p. 830, Pls. 135, +136) have been developed from the Stauracanthida, and as each radial spine +of the latter bears four crossed apophyses, so the lattice-shell of the +former has eighty primary aspinal pores (four at the base of each spine). + + +177. _Descent of the Diporaspida._--Whilst the Tessaraspida (s 176) have +given rise to no new groups which could take rank as independent families, +no less than four separate families of ACANTHARIA have arisen from the +Diporaspida. The Phractopeltida (Pl. 133, figs. 1-6) are distinguished from +all other ACANTHARIA by the possession of two concentric spherical +lattice-shells, and have probably been developed from the {cxvi}Diporaspida +in the same way as the Dyosphaerida from the Monosphaerida among the +#Sphaeroidea#; in that case the smaller inner lattice-sphere (medullary +shell) would be the primary, and the larger outer sphere (cortical shell) +the secondary; this latter shows forty primary aspinal pores like those of +the Diporaspida. The possibility is not excluded, however, that the small +inner lattice-sphere of the Phractopeltida is a secondary product. The +three remaining families, which must be regarded as descendants of the +Diporaspida, form together a single phylogenetic series, and are separated +from the primitive group mainly by the fact that the original spherical +form of the lattice-shell has been modified into one distinguished by an +elongated equatorial axis (the hydrotomical axis); hence the #Prunophracta# +(pp. 794-859). The ellipsoidal Belonaspida have arisen directly by +hypertrophy of the two opposite equatorial spines of this hydrotomical axis +(p. 859, Pl. 136, figs. 6-9; Pl. 139, figs. 8, 9; perhaps they have also +arisen directly from the Amphilonchida). In the lentelliptical Hexalaspida +(Pl. 139) all six spines which lie in the hydrotomical meridian plane (two +equatorial and four polar) are very strongly developed, the remaining +fourteen being rudimentary. Finally, in the Diploconida the two conical +sheaths of the two opposite hydrotomical equatorial spines are so +predominant that they take the chief part in the formation of the +hour-glass-shaped shell. + + +178. _Phylogeny of the Nassellaria._--The legion NASSELLARIA or MONOPYLEA +is so clearly characterised by the peculiar porochora, which closes the +osculum at the oral pole of the monaxon central capsule, and by the +podoconus connected with it, that there can be no doubt that +phylogenetically it represents an independent stem (s 8). This stem is only +connected at its base by means of _Cystidium_ and _Nassella_ with _Actissa_ +and _Thalassicolla_, the stem-forms of the SPUMELLARIA. This stem is +monophyletic, inasmuch as all its members may be derived without violence +from the skeletonless Nassellida (_Nassella_, _Cystidium_, p. 896, Pl. 91, +fig. 1). + + +179. _Origin of the Nassellaria._--The Nassellida (p. 896), which may +naturally be considered as the common stem-group of the NASSELLARIA, are +most nearly related among other Radiolaria to the Thalassicollida, and in +both these skeletonless families the simplest forms, _Cystidium_ and +_Actissa_ correspond; on the other hand, those which have arisen from them +by the formation of alveoles in the calymma (_Nassella_ and +_Thalassicolla_) also correspond. The origin of the simplest Nassellida +from these primitive Thalassicollida may be explained by supposing that the +numerous (formerly evenly distributed) pores of the capsule membrane became +obliterated in the upper (apical) half of the central capsule, whilst in +the lower (basal) half they became correspondingly more strongly developed; +hence the porochora was formed at the oral pole of the vertical main axis, +and a differentiation of the endoplasm proceeding from this gave rise to +the characteristic podoconus. Both these organs still at present exhibit +very various degrees of progressive development. + + +{cxvii}180. _Hypothetical Genealogical Tree of the Nassellaria._ + + CYRTOIDEA. + ~~~~~~~~~~~~~~~~~~~~~~~~~ + BOTRYODEA _Triradiata_ + ~~~~~~~~~~~~~ + Pylobotryida Podocampida + | | + | _Eradiata_ | _Multiradiata_ SPYROIDEA + | | | ~~~~~~~~~~~~~~~~~ + | Lithocampida | Phormocampida Androspyrida + | | | | | + Lithobotryida | Podocyrtida | | + | | | | | + | Theocyrtida | Phormocyrtida | + Tholospyrida + | | | | | | + Cannobotryida | Tripocyrtida | Phormospyrida | + | | | | | | + | Sethocyrtida | Anthocyrtida | | + | | | | | | + | | Tripocalpida | | | + | | | | | | + | Cyrtocalpida | Phaenocalpida +---+----+ + | | | | | + STEPHOIDEA | +---------+------------+ Zygospyrida + ~~~~~~~~~~~~ | | (Spyroidea + triradiata) + Tympanida | Tripocalpida | + | | (Cyrtoidea triradiata monocyrtida) | + | | | | + Coronida | +------------------+-----------------------------+ + | | | + | Semantida | + | | | + +--+---+ Cyrtellaria + | | + | Cortiniscus | + | | | + Stephanida | | + | | | + +-----+------+ | + | | + Cortina *--------- Cortinida (PLECTELLARIA) + (Cortina) + | + Plectaniscus ---- Plagoniscus ---- } + | } + Tetraplecta ---- Tetraplagia ---- } PLECTOIDEA + | } Plectanida + Plectophora ---- Plagiacantha ---- } | + | } | + Triplecta ---- Triplagia ---- } Plagonida + | } + Nassoidea + (Nassellida) + | + Nassella + (Cystidium) + | + Actissa + + +{cxviii}181. _Plectellaria and Cyrtellaria._--The extensive legion +NASSELLARIA far surpasses the other three legions in the endless variety of +its skeletal structures, and owing to the complicated relationships of its +numerous families presents no lack of difficult phylogenetic problems. All +NASSELLARIA may be divided first into two main groups or sublegions, +#Plectellaria# and #Cyrtellaria#; the latter having a complete +lattice-shell, the former not. Probably the #Cyrtellaria# have been +polyphyletically developed from several different groups of #Plectellaria#. +These groups are, however, connected in such manifold ways that a +monophyletic origin of all the NASSELLARIAN skeletons from one original +element is possible. Such a primitive element may have been furnished by +any one of three different skeletal parts, the sagittal ring, the basal +tripod, and the latticed cephalis (compare pp. 891-895, Buetschli, L. N. +40, 41). + + +182. _Phylogenetic Skeletal Elements of the Nassellaria._--The multiform +skeleton of the NASSELLARIA may be referred in different ways to one of the +three above-mentioned structural elements. Each of these (p. 891) may by +itself form the skeleton; the sagittal ring in the simplest #Stephoidea# +(_Archicircus_, _Lithocircus_), the basal tripod in the simplest +#Plectoidea# (_Triplagia_, _Plagiacantha_), the latticed cephalis in the +simplest #Cyrtoidea# (_Cyrtocalpis_, _Archicapsa_). In the great majority +of the NASSELLARIA, however, two of these elements, or even all three, are +found combined. In most #Cyrtellaria#, more especially, both the sagittal +ring and the basal tripod may be recognised in the lattice-shell, though +often only in slight rudiments or scarcely perceptible traces. In the +#Plectellaria# also (which possess no latticed cephalis) there are +individual genera with complete development both of the sagittal ring and +basal tripod; this important combination is especially well represented in +the Cortinida (_Cortina_, _Cortiniscus_, _Stephanium_, _Stephaniscus_, +_Tripocoronis_, &c.). The greatest difficulty as regards the phylogeny of +the NASSELLARIA lies in the fact that the most various combinations of the +three elements are presented by closely related or very similar forms. If, +in spite of this, a monophyletic hypothesis as to the origin of the +NASSELLARIA seems essential all sides of the three possible hypotheses must +receive full consideration and critical comparison (ss 183-191). + + +183. _Ascent of the Nassellaria from the Plectoidea._--The monophyletic +hypothesis (No. 2, p. 893) which regards the basal tripod as the common +origin of the skeleton of all NASSELLARIA, starts from the simplest forms +of the #Plectoidea# (_Triplagia_, _Plagoniscus_, _Triplecta_, +_Plectaniscus_, &c., Pl. 91). All #Plectoidea# may be immediately derived +as diverging twigs of these, as well as all triradial and multiradial forms +of #Cyrtoidea# and #Spyroidea#; for in all these cases the distinctive +triradial (or the derived multiradial) form of skeleton appears directly +derivable from the simple basal tripod of the former. The same is perhaps +also true of many #Botryodea#. {cxix}Furthermore, certain important forms +of #Stephoidea# (_Cortina_, _Cortiniscus_, _Stephanium_, _Stephaniscus_, +&c.), which have a characteristic combination of the sagittal ring and +basal tripod, may be immediately derived from such forms of #Plectoidea# as +_Plagoniscus cortinaris_, _Plagiocarpa procortina_, _Plectaniscus +cortiniscus_, &c. On the contrary, those #Stephoidea# and #Cyrtoidea# in +which the basal tripod is wanting can only be derived from the #Plectoidea# +by the assumption that this structure has disappeared in consequence of +phylogenetic degeneration. The monophyletic derivation of the NASSELLARIA +from the #Plectoidea# has more internal probability than that from the +#Stephoidea#, since it is easier to suppose that the Cortinida (_Cortina_, +_Stephanium_, &c.) have been derived from the #Plectoidea# (_Plagoniscus_, +_Plagiocarpa_) than the converse. This view is the basis of the +hypothetical tree shown in s 180. + + +184. _Ascent of the Nassellaria from the Stephoidea._--The monophyletic +hypothesis (No. 1, p. 893) which regards the primary sagittal ring as the +common starting point of the skeleton in all NASSELLARIA, starts from the +simplest forms of #Stephoidea# (_Archicircus_, _Lithocircus_, &c., Pl. 81). +All #Stephoidea# and #Spyroidea# may be immediately derived from these, as +also the majority of the #Cyrtoidea# and probably of the #Botryodea#. Those +numerous forms of the last two groups, however, which possess no trace of a +sagittal ring, can only be derived from the former by the supposition that +the latter has completely disappeared in in consequence of gradual +phylogenetic degeneration. The same holds true also of the #Plectoidea#, +although certain forms (_e.g._, _Plagiocarpa procortina_, Pl. 91, fig. 5; +_Plectaniscus cortiniscus_, Pl. 91, fig. 9) appear to indicate the +commencing formation of the sagittal ring by the concrescence of two +branches, which approach each other from the upper part of the apical rod +and the ventral part of the basal rod. In any case, it is a fact of great +phylogenetic significance, that the primary sagittal ring in the cephalis +of the #Cyrtoidea# shows all conceivable stages of degeneration (compare +Buetschli, L. N. 40, 41, as well as the general account of and critical +comparison of the NASSELLARIA, pp. 889-895, &c.). + + +185. _Ascent of the Nassellaria from the Cyrtoidea._--The monophyletic +hypothesis (No. 3, p. 894) which regards the latticed cephalis as the +common point of origin of all the skeletons of the NASSELLARIA, starts from +the simplest forms of the #Cyrtoidea#, that is, from the Cyrtocalpida or +eradial Monocyrtida (_Archicorida_, _Archicapsida_, Pls. 51, 52, 98). All +#Cyrtoidea# and #Botryodea# may be regarded as divergent forms of these +monothalamous #Cyrtoidea#; the polythalamous simply by the addition of +fresh joints at the basal pole, the triradiate and multiradiate by the +development of three or more apophyses. The origin of the sagittal ring +(which presents every stage of development and degeneration in the +#Cyrtoidea#) may be regarded as a mechanical thickening of the latticed +plate in the sagittal circumference of the cephalis. By stronger +{cxx}development of this ring and coincident sagittal constriction of the +cephalis the order #Spyroidea# may be derived from the #Cyrtoidea#. On the +other hand, the #Plectellaria#, which possess no cephalis, and indeed no +complete lattice-shell whatever, may be derived from the Monocyrtida by the +assumption of a degeneration of this structure; the sagittal ring having +been preserved in the #Stephoidea#, and the tripod of the Tripocalpida in +the #Plectoidea#. Although such a monophyletic derivation of the +NASSELLARIA from the Cyrtocalpida is possible, and though here, too, the +Cortinida play an important part as connecting links, this hypothesis has +less internal probability than that of the derivation from the #Stephoidea# +(s 184) or #Plectoidea# (s 183). + + +186. _Genealogical Tree of the Plectoidea._--The order #Plectoidea# +includes those NASSELLARIA whose rudimentary skeleton does not contain the +characteristic sagittal ring of the #Stephoidea#, but consists of several +(at least three) radial spines, which proceed from a point in the centre of +the porochora. The branches of these radial spines remain free in the +Plagonida, whilst in the Plectanida they unite with each other to form a +loose meshwork (not, however, a complete lattice-shell). The number and +arrangement of the radial spines, which serve for generic distinctions, are +the same in both families, so that each genus of the Plectanida has arisen +from a corresponding genus of the Plagonida. The simplest Plagonida, which +possess a basal tripod (_Triplagia_ or _Plagiacantha_ with three rays, +_Tetraplagia_ with four rays) are probably to be regarded as forming the +common origin of the whole order. These agree with certain three- and +four-rayed skeletal pieces of the #Beloidea# (Thalassosphaerida and +Sphaerozoida); and also the four and six-rayed twinned pieces of the latter +(spicula bigemina and trigemina) repeat in the same fashion the skeleton of +the former (_Plagonidium_, _Plagonium_). This similarity, however, is a +mere analogy and possesses no phylogenetic significance. On the other hand, +certain Plagonida (_Plagoniscus_, _Plagiocarpa_), and the corresponding +genera of Plectanida (_Plectaniscus_, _Periplecta_) seem to have important +phylogenetic relations to certain #Stephoidea# (_Cortina_, _Cortiniscus_, +&c.); the sagittal ring of the latter having perhaps arisen by the vertical +apical spine of the former having been connected with their horizontal +basal rod by two ventral apophyses growing out opposite to each other +(compare pp. 902, 914, _Plagiocarpa procortina_, Pl. 91, fig. 5). In this +case the Plectanida would belong to the simplest stem-forms of the +NASSELLARIA. + + +187. _Genealogical Tree of the Stephoidea._--The order #Stephoidea# +includes all those NASSELLARIA whose skeleton does not form a complete +lattice-shell, but consists of one or more rings, and often of a loose +meshwork which arises by the union of branches of the rings. A _vertical +sagittal ring_ is constantly present, embracing the central capsule in the +median sagittal plane, and forming at its basal pole various processes, the +starting point for other skeletal forms. The most important of these is the +tripodal _Cortina_ {cxxi}(p. 950, s 182). The Stephanida are the most +archaic family among the #Stephoidea# (p. 937, Pl. 81), perhaps indeed +among all the NASSELLARIA (s 184); in them the sagittal ring and its +processes alone constitute the skeleton; secondary rings and meshes are +wanting. Two diverging families, the Semantida and Coronida, have been +developed from the Stephanida, and from one of them the family Tympanida +has arisen. + + The Semantida (p. 953, Pl. 92) develop a horizontal basal ring at the + oral side of the vertical sagittal ring; the basal meshes or lattice + gates, which remain between the former and the latter, are the important + cortinar pores (one pair jugular, one pair cardinal, p. 954); they + usually appear inherited in the cortinar septum of the #Cyrtellaria#. In + the Coronida (p. 967, Pls. 82, 94) a second vertical ring (the frontal + ring) appears in addition to the sagittal ring; it lies in the frontal + plane at right angles to the latter. Finally the Tympanida (p. 987, Pls. + 93, 94) have probably arisen from the Semantida by the formation of a + second horizontal ring (mitral ring) parallel to the basal and attached + to the upper portion of the sagittal ring. + + +188. _Genealogical Tree of the Spyroidea._--The extensive order #Spyroidea# +is of especial interest in connection with the phylogeny of the +NASSELLARIA, since all its members show two well-developed skeletal +elements in combination, the sagittal ring of the #Stephoidea# and the +latticed cephalis of the #Cyrtoidea#; the majority possess also the basal +tripod of the #Plectoidea# (or a radial skeleton derived from it). Hence +there is a possibility of deriving the stem-forms of the #Spyroidea# from +each of these three groups. The four families of this order exhibit similar +relationships to those of the four families of #Cyrtoidea#; the common +stem-group is the family Zygospyrida; from this the Tholospyrida have +arisen by the development of a galea on the apical pole, the Phormospyrida +by the addition of a thorax on the basal pole. The Androspyrida may be +derived either from the Tholospyrida by the formation of a basal thorax, or +from the Phormospyrida by the development of an apical galea. Some groups, +however, such as the peculiar Nephrospyrida (Pl. 90) have probably been +developed directly from the #Stephoidea#. + + +189. _Genealogical Tree of the Botryodea._--The peculiar order #Botryodea# +(p. 1103), which is both difficult to investigate and insufficiently known, +presents great phylogenetic difficulties both as to its ascent and descent. +Probably the different genera of this order have been polyphyletically +developed from different groups of #Cyrtoidea# (perhaps also to some extent +of #Spyroidea#) by the formation of lobes in the cephalis. The three +families of #Botryodea# are related to each other in the same way as are +the three first families of the #Cyrtoidea#. From the single-jointed +Cannobotryida (corresponding to the Monocyrtida), the two-jointed +Lithobotryida (corresponding to the Dicyrtida), may be derived by the +development of a basal thorax, and from the latter the three-jointed +Pylobotryida (like the Tricyrtida) by the addition of an abdomen. In the +last two families the forms with an open basal mouth {cxxii}(Botryopylida +and Botryocyrtida) are to be regarded as primitive: the Botryocellida and +Botryocampida have arisen by the closure of this mouth with a basal +lattice-plate. + + +190. _Genealogical Tree of the Cyrtoidea._--The multiform and extensive +group #Cyrtoidea# presents the greatest difficulties to be found in the +phylogeny of the NASSELLARIA, because their morphological relations are +most complicated, and because similar forms very often appear to be of +quite different origin. The great majority of the #Cyrtoidea# show more or +less clearly a combination of the three structural elements: sagittal ring, +basal tripod, and latticed cephalis (p. 891). There are also, however, +numerous #Cyrtoidea#, whose skeleton no longer shows any trace of the +sagittal ring. Many of these show as the basis of the skeleton a strong +basal tripod with an apical spine, around which the cephalis has obviously +been secondarily developed, _e.g._, the remarkable Euscenida (p. 1146, Pls. +53, 97) and the interesting Callimitrida (p. 1217, Pls. 63, 64). These may +have been derived immediately from the #Plectoidea# without any relation to +the #Stephoidea#. There are also numerous true Monocyrtida, whose shell +consists of a simple latticed cephalis without a trace of the sagittal ring +or basal tripod (Cyrtocalpida, Pl. 51, figs. 9-13; Pl. 98, fig. 13); these +may have been developed directly from the skeletonless Nassellida by the +formation of a simple ovoid _Gromia_-like shell, and may have no relation +either to the #Stephoidea# or #Plectoidea#. On these grounds, as well as +from the complicated relationships of the many smaller groups of +#Cyrtoidea#, it is probable that the whole order has been developed +polyphyletically from different divisions of the #Plectellaria#. + + +191. _Systematic Arrangement of the Cyrtoidea._--Although for the reasons +just given no systematic arrangement of the #Cyrtoidea# can at present, or +for a long time in the future, be regarded as other than artificial, yet +some general principles of classification for this extensive group can be +laid down, which may serve as starting points for some future natural +disposition. This is especially true of the relations which in an +artificial system (p. 1129) were primarily utilised for the distinction of +twelve families and twenty-four subfamilies; the number of segments in the +shell, the number of radial apophyses (and parameres), and the constitution +of the basal aperture of the shell. + + As regards the _number of segments_, separated by transverse + constrictions, of which the shell is composed, it is dependent upon the + secondary addition of new joints at the basal pole of the main axis. + Hence all many-jointed #Cyrtoidea# are to be derived from single-jointed + ones, and the four sections thus distinguished (Monocyrtida, Dicyrtida, + Tricyrtida, Stichocyrtida) form a phylogenetic series. Very often, + however, the primary cephalis disappears owing to retrograde + metamorphosis; and in such cases the single joint of the apparent + Monocyrtida is formed of the thorax (_e.g._, {cxxiii}Pls. 52, 54, &c.). + As regards the _number of radial apophyses_, three sections of + #Cyrtoidea# may be distinguished; the Pilocyrtida with three, the + Astrocyrtida with numerous apophyses, and the Corocyrtida with none (p. + 1129). The last two may in general be regarded as two divergent branches + from the first, for the eradiate Corocyrtida have probably been formed + from the triradial Pilocyrtida by entire loss of the radial apophyses, + whilst on the other hand the multiradiate Astrocyrtida have arisen from + them by additions to the primary apophyses (interpolation of interradial + between the perradial ones). As regards the _constitution of the + shell-aperture_, the #Cyrtoidea# may be divided into Cyrtaperta and + Cyrtoclausa (p. 1129); in general the Cyrtoclausa (with latticed + shell-aperture) have arisen from the Cyrtaperta (with simple open mouth); + in many Monocyrtida the converse may be supposed, the simple basal mouth + having been formed by degeneration of a basal lattice. + + +192. _Phylogeny of the Phaeodaria._--The legion PHAEODARIA or CANNOPYLEA is +so clearly marked off from other Radiolaria by the double membrane of the +central capsule and the astropyle at its oral pole, as well as by the +extracapsular phaeodium, that it must be regarded phylogenetically as an +independent stem (s 9). This stem is only connected at its root by +_Phaeodina_ with the stem-form of the SPUMELLARIA, _Actissa_. The stem +itself is monophyletic, inasmuch it its members may be derived without +violence from the skeletonless Phaeodinida (_Phaeodina_, _Phaeocolla_). On +the other hand, the formation of the skeleton of the PHAEODARIA is +undoubtedly polyphyletic, different Phaeodinida having independently +commenced the formation of a skeleton and having carried it out in very +different ways. + + +193. _Origin of the Phaeodaria._--The Phaeodinida (p. 1544, Pl. 101), which +may naturally be regarded as the common stem-group of the PHAEODARIA, have +their nearest relations among other Radiolaria in the Thalassicollida (p. +10); and since this family is to be regarded as the primitive group of all +Radiolaria, they may be directly derived from them phylogenetically. The +essential modifications by which the primitive Phaeodinida have arisen from +the more archaic Thalassicollida are of three kinds; (1) the doubling of +the membrane of the central capsule; (2) the reduction of the numerous fine +pores in the membrane and the formation of an osculum, and of an astropyle +closing it, at the oral pole of the main axis; (3) the production of an +extracapsular phaeodium. This last may, perhaps, be regarded as a +unilateral hypertrophy of the voluminous pigment masses which are deposited +in the sarcomatrix of certain Thalassicollida. Of the two genera of +Phaeodinida hitherto known, probably _Phaeodina_ (Pl. 101, fig. 2) +approaches the original stem of the PHAEODARIA more nearly than +_Phaeocolla_ (Pl. 101, fig. 1), for the latter exhibits only the large main +opening of the central capsule (astropyle), whilst the former possesses +also a pair of accessory openings (parapylae). The hypothetical stem-form +(_Phaeometra_) presumably had a larger number of small parapylae (like many +Circoporida and Tuscarorida), and the astropyle was probably but little +differentiated from them. + + +{cxxiv}194. _Hypothetical Genealogical tree of the Phaeodaria:_-- + + PHAEOCONCHIA + ~~~~~~~~~~~~~~~~~~~~ + PHAEOSPHAERIA Coeloplegmida PHAEOGROMIA + ~~~~~~~~~~~~~~~~~~~ | ~~~~~~~~~~~~~~~~~~ + Aularida | Tuscarorida + | | | + |Aulonida | Coelodrymida | + | | | | | + +---+ Coelotholida | | + | Coelographida | | Haeckelinida + | | | | | + | Conchopsida | Coelodorida | | + Aulosphaerida | | Coelodendrida |Circogonida| + | | +----+---+ | | | + | Conchasmida | | | | + | Concharida | | | | + | Sagmarida +-----------+ | +--+--+ + | | | | | + Cannosphaerida| |Castanellida | Circoporida + | | | | | | + | |Oroscenida Concharida| +------+-+ + | | | | | | + | Sagenida | | | | + | Sagophaerida | | |Gazellettida | + | | | | | | | + | | Oronida | | |Pharyngellida| + | |Orosphaerida | | | | | + | | | | | | | | + +--------+-----+ | | | | | + | | | | | | + +--------------+-+ | | | | + | |Euphysettida| | + | |Medusettida | | + | | | | | + | | |Lithogromida | + | | |Challengerida| + Phaeodinida | | | | + | | | | | + PHAEOCYSTINA | +-----+-+----+ | + ~~~~~~~~~~~~~~~~~~~~ | | | + Aulacanthida | | | + |Cannobelida Catinulida | +------+----+ + | | | | | + | | Dictyochida | | | + | | | | | | + | +-----+-------+ | | + | | | Phaeodinida + | Cannorrhaphida | Phaeodinida | + | | | | | + +----------+------------+----+------+----------+ + | + Phaeodina + | + (Phaeometra) + | + Actissa + + +{cxxv}195. _Phaeocystina and Phaeocoscina._--Whilst the malacoma of all +PHAEODARIA possesses the characteristics of the legion, and hence justifies +the assumption of a monophyletic origin, the skeleton, on the other hand, +shows in the different groups such manifold and fundamental variations that +a polyphyletic origin of the latter is indubitable. Different Phaeodinida +have commenced the formation of the skeleton independently, and it has +progressed in different directions. In the #Phaeocystina# it remained +incomplete and led to the formation of various Beloid skeletons, whilst the +#Phaeocoscina# developed complete lattice-shells. Both of these divisions +too are to be regarded as polyphyletic, since the skeletal forms of the +different groups cannot be derived without violence from a common primitive +form. + + +196. _Phaeocystina with a Beloid Skeleton._--The order #Phaeocystina# +includes all PHAEODARIA which have no complete lattice-shell; it contains, +firstly, the skeletonless Phaeodinida (the common stem-group of the +legion), and secondly, the Phaeacanthida, or PHAEODARIA with a Beloid +skeleton (s 115). The latter are divisible into several very different +groups (at least two or three) which are probably different in origin. The +Aulacanthida (Pls. 102-105) form radial tubes which perforate the calymma, +their proximal end resting upon the surface of the central capsule, whilst +the distal extremity projects freely outwards. The skeleton of the +Cannorrhaphida, on the other hand, is composed of many separate portions +which are never radially arranged but are either placed tangentially to the +surface of the calymma or scattered irregularly in its gelatinous mass. +Furthermore, in the three subfamilies of which this family is composed, the +individual skeletal portions are so different that they have probably +arisen independently of each other; in the Cannobelida they form +cylindrical tangential tubes (Pl. 101, figs. 3-5), in the Catinulida flat +basin or cap-like structures (Pl. 117, fig. 8), in the Dictyochida hollow +rings, from which small pyramids are developed by unilateral formation of +lattice-work (Pl. 101, figs. 9-14; Pl. 114, figs. 7-12). + + +197. _Phaeosphaeria with a Sphaeroid Skeleton._--The order #Phaeosphaeria# +includes those PHAEODARIA which possess a spherical (sometimes slightly +modified) lattice-shell without the characteristic aperture of the +#Phaeogromia#. They have probably arisen independently of these, though +they may have been derived from the Castanellida by loss of the +shell-aperture, which was present originally. The four families which we +have distinguished among the #Phaeosphaeria#, are so different in the +structure of their lattice-shell that their phylogenetic connection is +doubtful. In the Orosphaerida (Pls. 106, 107) and the Sagosphaerida (Pl. +108) the whole lattice-shell consists of a single piece and is unjointed +(without astral septa); in the former it is very firm and massive, with +thick laminated trabeculae and polygonal meshes; in the latter it is very +delicate and brittle, with filiform trabeculae and large {cxxvi}triangular +meshes. On the other hand, the voluminous shell of the Aulosphaerida (Pls. +109-111), and of the Cannosphaerida (Pl. 112), is characterised by a very +peculiar system of joints; it is composed of numerous separate cylindrical +tubes, which are placed tangentially and united at the nodes by stellate +partitions or astral septa. The Cannosphaerida possess further a simple +central Cyrtoid shell, connected with the outer jointed shell by hollow +radial trabeculae. Since many Aulosphaerida possess rudiments of such +centripetal trabeculae it is possible that these latter have been derived +from the former by the loss of the central Cyrtoid shell; the formation of +this monaxon shell perhaps indicates descent from the #Phaeogromia# +(Castanellida). + + +198. _Phaeogromia with a Cyrtoid Skeleton._--That order of the PHAEODARIA +which we designate #Phaeogromia#, contains many very different forms, all +agreeing in the possession of a Cyrtoid skeleton, or a monaxon +lattice-shell, which has a large aperture at one pole of its vertical main +axis (s 123). This Cyrtoid skeleton is sometimes ovoid or conical, +sometimes lentiform or helmet-shaped, sometimes polyhedral or almost +spherical. Although the principle of its structure is simple and often like +that of the Monocyrtida among the NASSELLARIA, yet the structure of the +wall and of the apophyses is so different in the various groups of the +#Phaeogromia#, that the order is probably polyphyletic, and its Cyrtoid +shells have arisen independently of each other. Only in the Castanellida +(Pl. 113) does the shell-wall usually consist of simple lattice-work; in +the Challengerida, on the other hand (Pl. 99), it has an extremely fine +Diatom-like structure; in the Medusettida (Pls. 118-128) a peculiar +alveolar structure, and in the Circoporida (Pls. 114-117) and Tuscarorida +(Pl. 100) it possesses a characteristic porcellanous constitution (with +tangential spicules in a porous cement-mass); in the latter of these groups +the surface is smooth, in the former peculiarly tabulate; the two families +have also different stem-forms. + + +199. _Phaeoconchia with a Conchoid Shell._--The order #Phaeoconchia# (Pls. +121-128) is separated not only from all other PHAEODARIA, but also from all +other Radiolaria, by the possession of a bivalved shell resembling that of +a Lamellibranch; the two valves of this Conchoid skeleton are to be +interpreted as dorsal and ventral (s 128). Probably these bivalved shells +are independent products, but possibly they may have been formed by the +bisection of a simple spherical lattice-shell; in the former case the +#Phaeoconchia# would be directly descended from the Phaeodinida, in the +latter from the Castanellida. The three families which we have +distinguished among the #Phaeoconchia#, probably constitute a connected +stem, the most primitive group of which are the Concharida (Pls. 123-125). +From these the Coelodendrida (Pls. 121, 122) have next arisen by the +formation of a "galea" upon the apex of each valve, and the growth of +hollow tubes from this helmet-like structure. Finally, the Coelographida +{cxxvii}(Pls. 120-128) have been developed from the Coelodendrida by the +formation of a basal nasal tube (rhinocanna) from each galea, and the +formation of a median or paired frenulum, which connects the opening of the +nasal tube with the apex of the galea. In the Coelodendrida, as well as in +the Coelographida, there are two different subfamilies, of which the more +primitive (Coelodorida, Coelotholida) have free branches from the hollow +radial tubes, whilst the more recent (Coelodrymida, Coeloplegmida) form an +outer bivalved shell by anastomosis of the branches of the tubes. + + +200. _The Fundamental Biogenetic Law._--The causal connection between +ontogeny and phylogeny, which finds its most precise statement in the +fundamental biogenetic law, holds in general for the Radiolaria as for all +other organisms. In order to furnish direct proof of this, however, a +complete empirical knowledge both of individual and of palaeontological +development would be necessary. In both these directions, as has been shown +in the foregoing chapters, our knowledge of the Radiolaria is very +incomplete and fragmentary, but still we are able to convince ourselves +indirectly of the validity of the law as applied to Radiolaria by the aid +of comparative anatomy. This is now so fully known to us (ss 1-140) that we +are able not only to draw a complete and satisfactory picture of their +morphology, but also to arrive at most important conclusions regarding the +ontogeny and phylogeny of the individual groups. As regards the formation +of the multiform skeleton of the Radiolaria, most of the ontogenetic series +of forms, with which we have become acquainted by comparative anatomy, are +of _palingenetic_ nature; that is, they are primarily due to inheritance +and thus of direct phylogenetic significance. On the other hand, among the +ontogenetic phenomena of the Radiolaria, as far as they have yet been +investigated, only very few are _cenogenetic_, that is, brought about by +adaptive modification and without direct significance as regards phylogeny. + + + + +{cxxviii}PHYSIOLOGICAL SECTION. + + +---- + + +CHAPTER VII.--VEGETATIVE FUNCTIONS. + +(ss 201-217.) + +201. _Mechanism of the Functions._--The vital phenomena of the Radiolaria +are dependent upon the mechanical functions of their unicellular body, and +like those of all other organisms, are to be referred to physical and +chemical natural laws. All processes which appear in the life of the +Radiolaria are, therefore, ultimately to be explained by the attraction and +repulsion of the smallest particles, which compose the different portions +of their unicellular body; and the sensation of pleasure or the opposite is +in its turn the exciting cause of these elementary movements. Many adaptive +arrangements in the Radiolarian organism may produce the appearance of +being the premeditated result of causes working towards an end +("zweckthaetig," _causae finales_), but as opposed to this deceptive +appearance it must here be expressly stated that these may be recognised in +accordance with the developmental theory as the necessary consequence of +mechanical causes (_causae efficientes_). + + Our _physiological_ acquaintance with the Radiolaria has by no means + progressed so far as our _morphological_, so that the incomplete + communications which are placed here for the sake of completeness must be + regarded merely as preliminary fragments, not as fully elaborated + results. Since my recent investigations have been mainly in the direction + of morphology, I can add but little to the physiological conclusions, + which I stated at length in my monograph twenty-four years ago (L. N. 16, + pp. 127-165). Recently the vegetative physiology of the Radiolaria has + been much advanced by the recognition of the symbiosis with the + Xanthellae (s 205, L. N. 22, 39, 42). In addition Karl Brandt has + recently (1885) published several important contributions to the + physiology of the Polycyttaria or Sphaerozoea (L. N. 52). + + +202. _Distribution of Functions._--The distribution of the functions among +the various parts of the unicellular organism of the Radiolaria corresponds +directly to their anatomical composition, so that physiologically as well +as morphologically the central capsule and the extracapsulum appear as the +two coordinated main components. On the one hand the _central capsule_ with +its endoplasm and enclosed nucleus is the central organ of the "cell-soul" +(Zellseele), the unit regulating its animal and vegetative functions, and +the special organ of reproduction and inheritance. The _extracapsulum_ +forms, on the other hand, by its calymma the protective envelope of the +central {cxxix}capsule, the support of the soft pseudopodia and the +substratum of the skeleton; the calymma acts also as a hydrostatic +apparatus, whilst the radiating pseudopodia are of the greatest importance +both as organs of nutrition and adaptation, as well as of motion and +sensation (s 15). If, however, the vital functions as a whole be divided in +accordance with the usual convention into the two great groups of +_vegetative_ (nutrition and reproduction) and _animal_ (motion and +sensation), then the central capsule would be mainly the organ of +reproduction and sensation, and the extracapsulum the organ of nutrition +and motion. + + The numerous separate vital phenomena, which by accurate physiological + investigation may be distinguished in the unicellular Radiolarian + organism, may be distributed in the above indicated conventional fashion + into a few larger and several smaller groups; it must always be borne in + mind, however, that these overlap in many respects, and that the division + of labour among the different organs in these Protista is somewhat + complicated, notwithstanding the apparent simplicity of their unicellular + organization. A general classification of the groups of functions is + difficult, because each individual organ discharges several different + functions. Thus the central capsule is pre-eminently the organ of + reproduction and inheritance, but not less (though less conspicuous) is + its importance as the psychical central organ, the unit regulating the + processes of sensation, motion, and also nutrition. In this last respect + it is comparable to the nerve-centres of the Metazoa, whilst the + peripheral nervous system of the latter (including the organs of sense + and the muscles) are in the present instance represented by the + pseudopodia, which are at the same time the most important organs of + nutrition and adaptation. In the calymma also in similar fashion several + different physiological functions are united. + + +203. _Metastasis._--The functions of metastasis and nutrition have in all +Radiolaria a purely animal character, so that these Rhizopoda from the +physiological standpoint are to be regarded as truly _unicellular animals_, +or Protozoa ("Urthiere"). Since they do not possess, like plants, the power +of forming synthetically the compounds (protoplasm, carbohydrates, &c.) +necessary for their sustenance, they are compelled to obtain them +ready-formed from other organisms. Like other true animals they evolve +carbon dioxide by the partial oxidation of those products, and hence they +successively take up the oxygen necessary to their existence from their +environment. + + The question whether the Radiolaria are to be regarded as true animals I + discussed fully from various points of view in 1862, and finally answered + in the affirmative (L. N. 16, pp. 159-165). Afterwards, when in my + Generelle Morphologie (1866) I sought to establish the kingdom Protista, + I removed the Radiolaria along with the other Rhizopoda from the animal + kingdom proper and placed them in the kingdom Protista (Bd. i. pp. + 215-220; Bd. ii. p. xxix). Compare also my Protistenreich (L. N. 32) and + my Natuerliche Schoepfungsgeschichte (vii. Aufl., 1879, p. 364). Both + these steps appear fully justified when considered in the light of our + present increased knowledge. From the _physiological_ standpoint the + Radiolaria appear as unicellular _animals_, for in this respect the + animal character of their metastasis (that proper to an oxidising + organism) furnishes the sole {cxxx}criterion. On the other hand, from the + morphological standpoint, they are to be classed as neutral Protista, for + in this respect their unicellular character is the prominent feature, and + distinguishes them from all true multicellular animals (Metazoa). Compare + my Gastraea Theorie (1873, Jena. Zeitschr. fuer Naturwiss., Bd. viii. pp. + 29, 53). + + +204. _Nutrition._--The nutritive materials which the Radiolaria require for +their sustenance, especially albuminates (plasma) and carbohydrates +(starch, &c.), they obtain partly from foreign organisms which they capture +and digest, and partly directly from the Xanthellae or Philozoa, the +unicellular Algae, with which they live in symbiosis (s 205). _Zooxanthella +intracapsularis_, found in the ACANTHARIA (s 76), is probably of the same +significance in this respect as _Zooxanthella extracapsularis_ of the +SPUMELLARIA and NASSELLARIA (s 90); and perhaps the same is true also of +_Phaeodella extracapsularis_ (or _Zoochlorella phaeodaris_?) of the +PHAEODARIA (s 89). The considerable quantity of starch or amyloid bodies, +elaborated by these inquiline symbiontes, as well as their protoplasm and +nucleus, are available, on their death, for the nutrition of the Radiolaria +which harbour them. Nutrition by means of other particles obtained by the +pseudopodia from the surrounding medium is by no means excluded; indeed it +may be regarded as certain that numerous Radiolaria (especially such as +contain no symbiotic Algoid cells) are nourished for the most part or +exclusively by this means. Diatoms, Infusoria, Thalamophora (Foraminifera) +as well as decaying particles of animal and vegetable tissues can be seized +directly by the pseudopodia and conveyed either to the sarcodictyum (on the +surface of the calymma) or to the sarcomatrix (on the surface of the +central capsule) in order to undergo digestion there. The indigestible +constituents (siliceous shells of Diatoms and Tintinnoidea, calcareous +shells of small Monothalamia and Polythalamia, &c.) are here collected +often in large numbers and removed by the streaming of the protoplasm. + + The inception and digestion of nutriment, as it usually appears to take + place by the pseudopodia, has already been so fully treated in my + Monograph (L. N. 16, pp. 135-140), and since then in my paper on the + sarcode body of the Rhizopoda (L. N. 19, p. 342), that I have nothing of + importance to add. Quite recently Karl Brandt has expressed a doubt as to + whether the taking up of formed particles by the pseudopodia and their + aggregation in the calymma be really connected with the process of + nutrition. He is disposed rather to believe that these foreign bodies are + usually only accidentally and mechanically brought into the calymma, and + that the nourishment of the Radiolaria is derived exclusively or + pre-eminently from the symbiotic Xanthellae (L. N. 52, pp. 88-93). I + must, however, maintain my former opinion, which I have only modified + insomuch that I now regard the sarcodictyum (on the outer surface of the + calymma, s 94) rather than the sarcomatrix (on the outer surface of the + central capsule, s 92) as the principal seat of true digestion and + assimilation. From the sarcodictyum the dissolved and assimilated + nutritive matters may pass by the intracalymmar pseudopodia (or + sarcoplegma, s 93) into the sarcomatrix, and hence may reach the + endoplasm through the openings in the central capsule. To what an extent + the Radiolaria are capable of taking up even large formed bodies into the + calymma, is shown by the {cxxxi}striking instance of _Thalassicolla + sanguinolenta_, which becomes so deformed by the inception of numerous + coccospheres and coccoliths, that I described it as a special genus under + the name _Myxobrachia_ (compare pp. 23, 30; also L. N. 21, p. 519, Taf. + xviii., and L. N. 33, p. 37). + + +205. _Symbiosis._--Very many Radiolaria, but by no means all members of +this class, live in a definite commensal relation with yellow unicellular +Algae of the group Xanthellae. In the ACANTHARIA they live within the +central capsule (_Zooxanthella intracapsularis_, s 76), in the SPUMELLARIA +and NASSELLARIA, on the other hand, within the calymma but outside the +central capsule (_Zooxanthella extracapsularis_, s 90); in the PHAEODARIA a +special form of these symbiotic unicellular Algae appears to inhabit the +phaeodium in the extracapsulum, and to compose a considerable portion of +the phaeodellae (_Zooxanthella phaeodaris_, s 90, or better perhaps +_Zoochlorella phaeodaris_, s 89). Undoubtedly this commensal life is in +very many cases of the greatest physiological significance for both the +symbiontes, for the animal Radiolarian cells furnish the inquiline +Xanthellae not only with shelter and protection, but also with carbon +dioxide and other products of decomposition for their nutriment; whilst on +the other hand the vegetable cells of the Xanthellae yield the Radiolarian +host its most important supply of nutriment, protoplasm and starch, as well +as oxygen for respiration. Hence it is not only theoretically possible, but +has been experimentally proved, that Radiolaria which contain numerous +Xanthellae can exist without extraneous nutriment for a long period in +closed vessels of filtered sea-water, kept exposed to the sunlight; the two +symbiontes furnish each other mutually with nourishment, and are +physiologically supplementary to each other by reason of the opposite +nature of their metastasis. This symbiosis is not necessary, however, for +the existence of the Radiolaria; for in many species the number of +Xanthellae is very variable and in many others they are entirely wanting. + + The symbiosis of the Radiolaria and Xanthellae, or "yellow cells" (ss 76, + 90) was first discovered by Cienkowski in 1871 (L. N. 22). Ten years + later this important and often doubted fact was established by extended + observations and experiments almost simultaneously by Karl Brandt (L. N. + 38, 39) and Patrick Geddes (L. N. 42, 43). This commensal life may be + compared with that of the lichens, in which an organism with vegetable + metastasis (the Algoid gonidia) and an organism with animal metastasis + (the Fungoid hyphae) are intimately united for mutual benefit. But the + symbiosis of the Xanthellae and Radiolaria is not as in the lichens a + phenomenon essential for their development, but has more or less the + character of an accidental association. The number of the inquiline + Xanthellae is so variable even in one and the same species of Radiolaria, + that they do not appear to be exactly essential to its welfare; and in + many species they are entirely wanting. Their significance is + questionable in the case of those numerous deep-sea Radiolaria which live + in complete darkness, and in which, therefore, the Xanthellae, even if + present, could excrete no oxygen on account of the want of light. + Nevertheless it is possible that the phaeodellae of the PHAEODARIA + (usually green, olive, or brown in colour), which are true cells, + represent vegetable symbiontes, {cxxxii}which in the absence of sunlight + are able to evolve oxygen by the aid of the phosphoresence of other + abyssal animals. Since the PHAEODARIA are, for the most part, dwellers in + the deep-sea, and since the voluminous phaeodium must be of great + physiological importance, a positive solution of this hypothetical + question would be of no small interest (compare s 89). + + +206. _Respiration._--The respiration of the Radiolaria is animal in nature, +since all Protista of this class, like all other true Rhizopoda, take in +oxygen and give off carbon dioxide. Probably this process goes on +continuously and is tolerably active, as may be inferred from the fact that +Radiolaria cannot be kept for long in small vessels of sea-water unless +either they contain numerous Xanthellae or the water is well aerated. The +oxygen is obtained from two sources, either from the surrounding water or +from the enclosed Xanthellae, which in sunlight evolve considerable +quantities of this gas. Correspondingly, the carbon dioxide which is formed +during the process of oxidation of the Radiolaria is either given up to the +surrounding water or to the inquiline Xanthellae, which utilise it for +their own sustenance (ss 204, 205). + + The significance of the symbiotic Xanthellae for the respiration of the + enclosing Radiolaria may be shown experimentally in the following way. If + two Polycyttarian colonies of equal size, both of which contain numerous + Xanthellae, be placed in equal quantities of filtered sea-water in sealed + glass tubes, and if one tube be placed in the dark the other in the + light, the colony in the former rapidly perishes, but not that in the + latter; the Xanthellae excrete only under the influence of sunlight the + oxygen necessary for the life of the Radiolarian (compare Patrick Geddes, + L. N. 42, p. 304). + + +207. _Circulation._--In the protoplasm of all Radiolaria, both inside and +outside the central capsule, slow currents may be recognised which fall +under the general term circulation, and have already been compared to the +cyclosis in the interior of animal and vegetable cells, as well as to the +sarcode streams in the body of other Rhizopoda. These plasmatic currents or +"plasmorrheumata" probably continue throughout the whole life of the +Radiolaria, and are of fundamental importance for the performance of their +vital functions. They depend upon slow displacements of the molecules of +the plasma (plastidules or micellae) and cause a uniform distribution of +the absorbed nutriment and a certain equalisation of the metastasis. +Furthermore they are of great importance also in the inception of +nutriment, the formation of the skeleton, locomotion, &c. Sometimes the +circulation is directly perceptible in the plasma itself; but usually it is +only visible owing to the presence of granules (sarcogranula), which are +suspended in the plasma in larger or smaller numbers. The movements of +these granules are usually regarded as passive, due to the active +displacement of the molecules of the plasma. Although the intracapsular +protoplasm is in communication with the extracapsular through the openings +in the capsule membrane, nevertheless the currents exhibit certain +differences {cxxxiii}in the two portions of the malacoma. It is sometimes +possible, however, to recognise the direct connection between them and to +observe how the granules pass through the openings in the capsule-membrane. + + +208. _Currents in the Endoplasm._--Intracapsular circulation or a certain +slow flowing of the plasma within the central capsule is probably just as +common in the Radiolaria as without it, but it is not so easy to observe in +the former case as in the latter. A more satisfactory proof of these +endoplasmatic currents is furnished by the arrangement of the protoplasm +within the central capsule, since this is (at all events in part) an effect +produced by them. In this respect the two main divisions of the class show +characteristic differences. In the Porulosa (the SPUMELLARIA, s 77, and the +ACANTHARIA, s 78) the endoplasm is in general distinguished by a more or +less distinct radial structure, which is to be regarded as the effect of +alternating centripetal and centrifugal radial streams. In the Osculosa, on +the other hand, this radial structure is absent and the intracapsular +plasmatic streams converge or diverge towards the osculum or main-opening +in the central capsule which lies at the basal pole of its main axis, and +through which the mass of the endoplasm issues into the calymma. The two +legions of the Osculosa, however, present differences in this respect. In +the NASSELLARIA (s 79) the endoplasmatic currents appear to unite in an +axial main stream at the apex of the monaxon central capsule, and this +apical stream seems to split into a conical bundle, the individual threads +of which pass diverging between the myophane fibrillae of the podoconus +towards the basis of the central capsule, and issue through the pores of +the porochora. In the PHAEODARIA (s 80), on the other hand, meridional +currents of endoplasm are probably present on the inner surface of the +capsule, which flow from the aboral pole of the vertical main axis to its +basal pole, and return in the reverse direction. + + +209. _Currents in the Exoplasm._--Extracapsular circulation, or a distinct +flowing of the plasma outside the central capsule, may be readily observed +in all Radiolaria which are examined alive; this is most readily seen in +the astropodia, or those free pseudopodia which radiate from the +sarcodictyum on the surface of the calymma into the surrounding water. The +granular movement is often quite as clear in the sarcodictyum itself, and +may be recognised in the collopodia, which compose the irregular plasmatic +network within the calymma. More rarely it is possible to follow the +granular stream thence through the sarcomatrix, and further into the +interior of the central capsule. In general the direction of the +extracapsular protoplasmic streams is radial, and it is frequently +possible, even in a single free astropodium, to observe two streams +opposite in direction, the granules on one side of the radial sarcode +thread moving centripetally, those on the other side centrifugally. If the +threads branch, and neighbouring ones {cxxxiv}become united by connecting +threads, the circulation of the granules may proceed quite irregularly in +the network thus formed. The rapidity and character of the extracapsular +currents are subject to great variations. + + The different forms of extracapsular sarcode currents have been already + very fully described in my Monograph (L. N. 16, pp. 89-126), and in my + critical essay on the sarcode body of the Rhizopoda (L. N. 19, p. 357, + Taf. XXVI.). + + +210. _Secretion._--Under the name _secretions_, in the strict sense, all +the skeletal formations of the Radiolaria may be included. They may be +divided according to their chemical composition into three different +groups: pure silica in the SPUMELLARIA and NASSELLARIA, a silicate of +carbon in the PHAEODARIA, and acanthin in the ACANTHARIA (compare s 102). +It may indeed be assumed that these skeletons arise directly by a chemical +metamorphosis (silicification, acanthinosis, &c.) of the pseudopodia and +protoplasmic network; and this view seems especially justified in the case +of the Astroid skeleton of the ACANTHARIA (s 114), the Spongoid skeleton of +the SPUMELLARIA (s 126), the Plectoid skeleton of the NASSELLARIA (s 125), +the Cannoid skeleton of the PHAEODARIA (s 127), and several other types. On +closer investigation, however, it appears yet more probable that the +skeleton does not arise by direct chemical metamorphosis of the protoplasm, +but by secretion from it; for when the dissolved skeletal material (silica, +acanthin) passes from the fluid into the solid state, it does not appear as +imbedded in the plasma, but as deposited from it. However, it must be borne +in mind that a hard line of demarcation can scarcely, if at all, be drawn +between these two processes. In the ACANTHARIA the intracapsular sarcode is +the original organ of secretion of the skeleton; in the other three +legions, on the other hand, the extracapsulum performs this function (ss +106, 107). In addition to the skeleton, we may regard as secretions (or +excretions) the intracapsular crystals (s 75) and concretions (s 75A), and +perhaps certain pigment-bodies (ss 74, 88); and further, the calymma (s 82) +may be considered to be a gelatinous secretion of the central capsule, and +perhaps also the capsule-membrane, in so far as it represents only a +secondary excretory product of the unicellular organism. + + +211. _Adaptation._--The innumerable and very various adaptive phenomena +which we meet with in the morphology of the Radiolaria, and especially in +that of their skeleton, are like other phenomena of the same kind, to be +ultimately referred to altered nutritional relations. These may be caused +directly either by the influence of external conditions of existence +(nutrition, light, temperature, &c.), or by the proper activity of the +unicellular organism (use or disuse of its organs, &c.), or, finally, by +the combined action of both causes in the struggle for existence. In very +many cases the cause to which the origin of a particular form of Radiolaria +is due may be directly perceived or at least guessed at with considerable +probability; thus, for example, the lattice-shells {cxxxv}may be explained +as protective coverings, the radial spines as defensive weapons, and the +anchor-hooks and spathillae as organs of prehension, which are of advantage +to their possessors in the struggle for existence; the regular arrangement +of the radial spines in the Radiolaria may also be explained on hydrostatic +grounds, it being advantageous that the body should be maintained in a +definite position of equilibrium, &c. The well-known laws of _direct_ or +_actual adaptation_, which we designate cumulative, correlative, divergent +adaptation, &c., here explain a multitude of morphological phenomena. The +connection is less distinct in the case of the laws of _indirect_ or +_potential adaptation_, although this must play as important a part in the +formation of the Radiolaria as in that of other organisms (compare on this +head my Generelle Morphologie, Bd. ii. pp. 202-222). + + +212. _Reproduction._--The most common form of reproduction in the +Radiolaria is the formation of spores in the central capsule, which in this +respect is to be regarded as a sporangium (s 215). In many Radiolaria +(Polycyttaria and PHAEODARIA), however, there occurs in addition an +increase of the unicellular organism by simple division (s 213); upon this +the formation of colonies in the social Radiolaria is dependent (s 14). +Reproduction by gemmation is much less common, and has hitherto been +observed only in the Polycyttaria (s 214). In this group alone there also +occur at certain times two different forms of swarm-spores which copulate, +and thus indicate the commencement of sexual reproduction (Alternation of +Generations, s 216). The general organ of reproduction is in all cases the +central capsule, whilst the extracapsulum never takes an active part in the +process. + + +213. _Cell-Division._--Increase by cell-division among the Radiolaria in +the early stage, before the formation of the skeleton, is widely +distributed (perhaps even general?); in the adults of this class it is +rather rare and limited to certain groups. It is most readily observed in +the Polycyttaria; the growth of the colonies in this social group depends +mainly (and in many species exclusively) upon repeated spontaneous division +of the central capsule; all the individuals of each colony (in so far as +this has not arisen by the accidental fusion of two or more colonies) are +descendants of a single central capsule, which has arisen from an asexual +swarm-spore (s 215) or from the copulation of two sexual swarm-spores (s +216). Whilst the central capsules of the colonies continually increase by +division, their calymma remains a common gelatinous sheath. Among the +SPUMELLARIA reproduction by simple cell-division probably occurs also in +many monozootic #Collodaria#. Among the ACANTHARIA the peculiar group +Litholophida has perhaps arisen by the spontaneous division of +#Acanthonida# (see p. 734). Among the PHAEODARIA increase by cell-division +seems to occur commonly in many groups, as in the #Phaeocystina#, which +have no skeleton (Phaeodinida, Pl. 101, {cxxxvi}fig. 2), or only an +incomplete Beloid skeleton (Cannorrhaphida, Pl. 101, figs. 3, 6, and +Aulacanthida, Pl. 104, figs. 1-3). The #Phaeosphaeria# also (Aulosphaerida, +Coelacanthida) and the #Phaeogromia# (Tuscarorida, Challengerida) appear +sometimes to divide; at all events, their central capsule often contains +two nuclei. Of special interest is the spontaneous division of the +#Phaeoconchia#, especially the Concharida (Pl. 124, fig. 6). In all +monozootic Radiolaria, the nucleus first divides by a median constriction +into two equal halves (usually by the mode of direct division); then the +central capsule becomes constricted in the middle (in the PHAEODARIA in the +vertical main axis), and each portion of the capsule retains its own +nucleus. In the #Phaeoconchia# each half or daughter-cell corresponds to +one valve of the shell, dorsal or ventral, so that probably on subsequent +separation each daughter-cell retains one valve of the mother-cell, and +forms a new one for itself by regeneration (as in the Diatoms). In the +polyzootic Radiolaria, which already contain many small nuclei, but usually +only a single central oil-globule in each central capsule, the division of +the latter is preceded by that of the oil-globule. In many Polycyttaria the +colony as a whole multiplies by division. + + The increase of the central capsule by division was first described in + 1862 in my Monograph (L. N. 16, p. 146); since then R. Hertwig (L. N. 26, + p. 24) and K. Brandt (L. N. 52, p. 144) have confirmed my statement. In + the PHAEODARIA the division of the central capsule appears always to take + place in the main axis; in the bilateral sometimes in the sagittal, + sometimes in the frontal plane. In the Tripylea each daughter-cell seems + to retain one parapyle and half the astropyle (compare the general + description of the PHAEODARIA, Pl. 101, figs. 1-6, Pl. 104, figs. 1-3, + and also Hertwig, L. N. 33, p. 100, Taf. x. figs. 2, 11). Regarding the + spontaneous division of colonies of the Polycyttaria, see K. Brandt, L. + N. 52, p. 142. + + +214. _Cell-Gemmation._--Reproduction by gemmation has hitherto been +observed only in the social Radiolaria, but in them it appears to be widely +distributed, and in very young colonies is perhaps almost universally +present. The gemmules or capsular buds (hitherto described as +"extracapsular bodies") are developed on the surface of young central +capsules before these had secreted a membrane. They grow usually in +considerable numbers, from the surface of the central capsule, which is +sometimes quite covered with them. Each bud usually contains a +raspberry-like bunch of shining fatty globules, and by means of reagents a +few larger or a considerable number of smaller nuclei may be recognised in +them; the naked protoplasmic body of the bud is not enclosed by any +membrane. As soon as the buds have reached a certain size they are +constricted off from the central capsule and separated from it, being +distributed in the meshes of the sarcoplegma by the currents in the +exoplasm. Afterwards each bud becomes developed into a complete central +capsule by surrounding itself with a membrane when it has attained a +definite size. From the special relations of the process of nuclear +formation, which take place in the multiplication of the {cxxxvii}social +central capsules by gemmation and by cell-division, it would appear that +the capsules produced by the former method afterwards produce anisospores, +whilst those in the latter way yield isospores (s 216). + + The gemmules or capsular buds of the Polycyttaria were first accurately + described by Richard Hertwig (L. N. 26, pp. 37-39), under the name + "extracapsular bodies," and their significance rightly indicated; earlier + observers had incidentally mentioned and figured them, but had not seen + their origin from the central capsule. Quite recently Karl Brandt has + given a very painstaking account of them in the different Polycyttarian + genera (L. N. 52, pp. 179-198). In the Monocyttaria such a formation of + buds has not yet been observed. The basal lobes of the central capsule, + which occur in many NASSELLARIA, are not buds, but simple processes of + the capsule, due to its protrusion through the collar pores of the + cortinar septum (s 55). + + +215. _Sporification._--Asexual reproduction by the formation of movable +flagellate spores has been hitherto observed only in a very small number of +genera; but since these belong to very different groups, and since the +comparative morphology of the capsule appears to be similar throughout as +regards the structure and development of its contents, it may be safely +assumed that this kind of reproduction occurs quite generally in the +Radiolaria. In all cases it is the contents of the central capsule, from +which the swarm-spores are formed, both nucleus and endoplasm taking an +equal share in the process; in all cases the spores produced are very +numerous, small, ovoid or reniform, and have one or two very long slender +flagella at one extremity (see ss 141, 142). Since the whole contents of +the mature central capsule are used up in the formation of these flagellate +zoospores, it discharges the function of a sporangium. The division of the +simple primary nucleus into numerous small nuclei, which usually +(serotinous Radiolaria) takes place only shortly before sporification, but +sometimes (precocious Radiolaria, s 63) happens very early, is the +commencement of the often repeated process of nuclear division, which +terminates with the production of a very large number of small +spore-nuclei. The nucleolus often divides very peculiarly (s 69, C). Each +spore nucleus becomes surrounded by a portion of endoplasm and usually +receives in addition one or more fatty granules, and sometimes also a small +crystal (hence the "crystal-spores"). The size of the flagellate zoospores +which emerge from the ruptured central capsule and swim freely in the water +by means of their flagellum, varies generally between 0.004 and 0.008 mm. +The extracapsulum is not directly concerned in the sporification, but +undergoes degeneration during the process and perishes at its conclusion. + + The first complete and detailed observations on the formation of spores + in the Radiolaria were published by Cienkowski in 1871 and related to two + genera of Polycyttaria, the skeletonless _Collozoum_ and the + spherical-shelled _Collosphaera_ (L. N. 22, p. 372, Taf. xxix.). These + were subsequently continued and supplemented by R. Hertwig (1876, L. N. + 26, pp. 26-42, and L. N. 33, p. 129), and a general summary of these + results has been given by Buetschli (L. N. 41, pp. 449-455). + {cxxxviii}Recently Karl Brandt has given a very detailed and fully + illustrated account of the sporification of the Polycyttaria (L. N. 52, + pp. 145-178). I have also had the opportunity during my sojourn in the + Canary Islands (1866), in the Mediterranean at Corfu (1877), and + Portofino (1880), as well as in Ceylon (1881), of observing the + development of flagellate zoospores from the central capsule of + individuals of all four legions: among the SPUMELLARIA in certain + #Colloidea#, #Beloidea#, #Sphaeroidea#, and #Discoidea#, among the + ACANTHARIA in several #Acanthometra# and #Acanthophracta#, among the + NASSELLARIA in individuals belonging to the #Stephoidea#, #Plectoidea#, + and #Cyrtoidea#, and among the PHAEODARIA in one Castanellid. In most + zoospores I could distinctly observe only a single long flagellum; + sometimes, however, two or even three appeared to be present, but the + determination of their number is very difficult. + + +216. _Alternation of Generations._--A peculiar form of reproduction, which +may be designated "alternation of generations," appears to occur generally +in the Polycyttaria, but has not yet been observed in the Monocyttaria. All +#Collozoida#, #Sphaerozoida#, and Collosphaerida which have hitherto been +carefully and completely examined with respect to their development, are +distinguished by the production of two different kinds of swarm-spores, +isospores and anisospores. The _Isospores_ (or monogonous spores) +correspond to the ordinary asexual zoospores of the Monocyttaria (s 215); +they possess a homogeneous, doubly refracting nucleus of uniform +constitution and develop asexually, without copulation. The _Anisospores_ +(or amphigonous spores), on the other hand, are sexually differentiated and +possess a heterogeneous, singly refracting nucleus of twofold constitution; +they may therefore be distinguished as female macrospores and male +microspores. The _Macrospores_ (or gynospores, comparable with the female +macrogonidia of many Cryptogams) are larger, less numerous, and possess +larger nuclei, which are less easily stained, and have a fine filiform +trabecular network. On the other hand the _Microspores_ (or _androspores_, +comparable with the male microgonidia) are much smaller and more numerous, +and are distinguished by their smaller nuclei, which have thicker +tuberculae and become stained more intensely. The gynospores and +androspores are developed in the #Collozoida# and #Sphaerozoida# in the +same individual, but not in the Collosphaerida. It is very probable that +these two forms of anisospores copulate with each other after their exit +from the central capsule and thus produce a new cell by the simplest mode +of sexual reproduction. But, since the same Polycyttaria, which produce +these anisospores, at other times give rise to ordinary or asexual +isospores, it is further possible that these two forms of reproduction +alternate with each other, and that the Polycyttaria thus pass through a +true alternation of generations. This has not yet been observed in the +Monocyttaria, and hence these latter seem to bear to the Polycyttaria a +relation similar to that in which the sexless solitary Flagellata +(Astasiea) stand to the sexual social Flagellata (Volvocinea). In the two +analogous cases the sexual differentiation may be regarded as a consequence +of the social life in the gelatinous colonies. + + {cxxxix}The _sexual differentiation of the Polycyttaria_ was first + discovered in 1875 by R. Hertwig, and accurately described in the case of + _Collozoum inerme_ as occurring in addition to the formation of the + ordinary crystal-spores (L. N. 26, p. 36); compare also the general + discussion of Buetschli (L. N. 41, p. 52). Recently Karl Brandt has + demonstrated the formation of both homogeneous isospores (crystal-spores) + and heterogeneous anisospores (macro- and microspores) in seven different + species of Polycyttaria, and has come to the conclusion that in all + social Radiolaria there is a regular alternation between the former and + latter generations. Compare his elaborate account of the colonial + Radiolaria of the Gulf of Naples (L. N. 52, pp. 145-178). + + +217. _Inheritance._--Inheritance is to be regarded as the most important +accompaniment to the function of reproduction, and especially in the +present case, because the comparative morphology of the Radiolaria +furnishes abundant instances of the action of its different laws. The laws +of _conservative inheritance_ are illustrated by the comparative anatomy of +the larger groups; thus, in the four legions the characteristic +peculiarities of the central capsule are maintained unaltered in +consequence of continuous inheritance, although great varieties appear in +the skeleton in each legion. The individual parts of the skeleton furnish +by their development on the one hand and their degeneration on the other, +especially in the smaller groups, examples of _progressive inheritance_. +Thus in the SPUMELLARIA the constant formation of the primary lattice-shell +(a central medullary shell) and its ontogenetic relation to the secondary +one, which is developed concentrically round it, can only be explained +phylogenetically by conservative inheritance, whilst on the other hand the +characteristic differentiation of the axes in the various families of +SPUMELLARIA is to be explained by progressive inheritance. In the +ACANTHARIA the arrangement of the twenty radial spines (in accordance with +Mueller's law, ss 110, 172) was first acquired by a group of the most +archaic #Actinelida# (Adelacantha) through hydrostatic adaptation, and has +since been transmitted by inheritance to all the other families of the +legion (Icosacantha). The morphology of the NASSELLARIA is not less +interesting, because here several different heritable elements (the primary +sagittal ring and the basal tripod) combine in the most manifold ways in +the formation of the skeleton (compare ss 123, 124, 182). The affinities of +the genera in the different families yield an astonishing variety of +interesting morphological phenomena, which can only be explained by +progressive inheritance. The same is true also of the PHAEODARIA. In this +legion the primary inheritance is especially manifested in the constant and +firm structure of the central capsule with its characteristic double wall +and astropyle, whilst the formation of the skeleton in this legion proceeds +in different directions by means of divergent adaptation. The morphology of +the Radiolaria thus proves itself a rich source of materials for the +physiological study of adaptation and inheritance. + + + +{cxl}CHAPTER VIII.--ANIMAL FUNCTIONS. + +(ss 218-225.) + +218. _Motion._--In addition to the internal movements which appear +generally in the unicellular Radiolaria and have already been mentioned as +plasmatic currents in treating of the circulation (ss 207-209), two +different groups of external motor phenomena are to be observed in this +class: first, the _contraction_ of individual parts, which brings about +modifications of form (s 220), and secondly, voluntary or reflex +_locomotion_ of the whole body (s 220). These movements are partly due to +changes in form of undifferentiated plasmatic threads or sarcode filaments, +partly to the actual contraction of differentiated filaments which are +comparable to muscle fibrillae, and must therefore be distinguished as +myophanes. In addition to this, endosmose and exosmose probably play an +important part in some of the locomotive phenomena, but nothing is yet +certainly known regarding these osmotic processes. We are at present +equally ignorant whether all the movements of the Radiolaria are simply +reflex (direct consequences of irritation) or whether they are in part +truly spontaneous. + + +219. _Suspension._--From direct observation of living Radiolaria, as well +as from deductive reasoning, based upon their morphology (and especially +their promorphology, ss 17-50), the conclusion appears justified that all +Protista of this class in their normal condition float suspended in the +sea-water, either at the surface or at a definite depth. A necessary +condition of this hydrostatic suspension is that the specific gravity of +the Radiolarian organism must be equal to, or but slightly greater than +that of sea-water. The increase in specific gravity brought about by the +production of the siliceous skeleton, is compensated by the lighter fatty +globules, and partly perhaps by the calymma, especially when the latter +contains vacuoles or alveoles. The fluid or jelly contained in the latter +appears to be for the most part lighter than sea-water (containing no salt, +or only a very small quantity?). But if the specific gravity of the whole +body should be generally (or perhaps always) slightly greater than that of +sea-water, then the organism would be prevented from sinking, partly by the +increased friction, due to the radiating pseudopodia and the radial spines +usually present, and partly perhaps by active (if only feeble) movements of +the pseudopodia. + + +220. _Locomotion._--Active locomotion of the whole body, which is very +probably to be regarded as voluntary, occurs in the Radiolaria in three +different modes; (1) the vibratile movement of the flagellate swarm-spores; +(2) the swimming of the floating organisms; (3) the slow creeping of those +which rest accidentally upon the bottom. {cxli}The _vibratile_ movement of +the swarm-spores is the result of active sinuous oscillation of the single +or multiple flagellum, and is not essentially different from that of +ordinary flagellate Infusoria (see note A). Of the active swimming of +mature Radiolaria, only that form is known which is vertical in direction +and causes the sinking and rising in the sea-water. This is probably, for +the most part (perhaps exclusively), due to increase or diminution in the +specific gravity, which is perhaps brought about by the retraction or +protrusion of the pseudopodia; slow, oscillating, sinuous motions of these +organs have been directly observed to take place (though very slowly) in +suspended living Radiolaria. The most important hydrostatic organ is +probably the calymma, by the contraction of which the specific gravity is +increased, while it is diminished by its expansion; the contraction is +probably brought about by active contraction of the sarcodictyum, and is +connected with exosmosis, while the expansion is probably due to the +elasticity of the calymma and the inception of water by endosmosis. In the +#Acanthometra# (s 96) the peculiar myophriscs appear to be charged with the +duty of distending the gelatinous envelope, and thus diminishing the +specific gravity; the latter increases again when the myophriscs are +relaxed, and the calymma contracts by virtue of its own elasticity (see +note B). The slow _creeping locomotion_ exhibited by Radiolaria on a glass +slide under the microscope, does not differ from that of the Thalamophora +(Monothalamia and Polythalamia), but can only occur normally when the +animal accidentally comes into contact with a solid surface or sinks to the +bottom of the sea. Whether this actually occurs periodically is not known +(see note C). The slow or gliding locomotion exhibited by creeping Monozoa +on a glass slide is due to muscle-like contractions of bundles of +pseudopodia, just as in the case of the social central capsules of Polyzoa, +which live together in the same coenobium and are able to move within their +common calymma sometimes centrifugally to its surface, sometimes towards +the centre where they aggregate into a roundish mass (see note D). + + A. Regarding the movement of the flagella in mature swarm-spores compare + L. N. 22, p. 375; L. N. 26, pp. 31, 35; L. N. 41, p. 452, and L. N. 52, + p. 170. + + B. On the active vertical swimming movements of mature Radiolaria, + especially the cause of sinking and rising, see L. N. 16, p. 134; L. N. + 41, p. 443, and L. N. 52, pp. 97-102. + + C. On the active horizontal creeping movements of mature Radiolaria on a + firm ground, compare L. N. 12, p. 10, and L. N. 16, pp. 132-134. + + D. Regarding the motion of social central capsules within the same + coenobium and the changes thus brought about in the structure of the + calymma, see L. N. 16, pp. 119-127, and L. N. 52, pp. 75-82. + + +221. _Contraction._--Motions, which are due to the contraction of +individual portions and cause changes in volume or form, have been partly +already spoken of under the head of locomotion (s 220) and are partly +connected with other functions. Examples may be seen in the contraction of +the central capsule and of the calymma. A certain {cxlii}contraction of the +central capsule is probably brought about by the myophanes, which arise by +differentiation of the endoplasm and hence may assume different forms in +the four legions. In the SPUMELLARIA, where numerous radial fibrillae run +from the central nucleus to the capsule membrane (s 77), the endoplasm is +probably driven out evenly through all the pores of the capsule membrane by +their simultaneous contraction, and hence the volume of the capsule is +diminished in all directions. The ACANTHARIA probably behave similarly, +but are different, inasmuch as the number of their contractile radial +fibrillae is less, and special axial threads (s 78) are already +differentiated. In the NASSELLARIA it is probable that owing to the +contraction of the divergent myophane fibrillae in the podoconus the +vertical axis of the latter is shortened, the opercular rods of the +porochora are lifted, and the endoplasm driven out of its pores, so that +the volume of the monaxon central capsule is diminished (s 79). In the +PHAEODARIA the same result is probably brought about by the contraction of +the cortical myophane fibrillae, which run meridionally along the inside of +the capsule membrane from the apical to the basal pole of the vertical main +axis, where they are inserted into the periphery of the astropyle; since +the volume of the capsule is diminished by their contraction (their +spheroidal figure becoming more nearly spherical) the endoplasm will be +driven out through the proboscis of the astropyle. Whilst these +contractions of the central capsule are largely due to differentiated +muscle-like threads of endoplasm (myophanes), this appears to be but rarely +the case with the contractions of the extracapsulum (_e.g._, the myophriscs +of the #Acanthometra#, s 96). Most of the phenomena of contraction which +can be observed in the calymma and pseudopodia depend upon exoplasmatic +currents (s 209). + + +222. _Protection._--Of the utmost importance, both for the physiology and +for the morphology of the Radiolaria are their manifold protective +functions, which we now consider under the heading "protection." From the +physiological point of view the consideration of the exposed situation in +which the delicate, free-swimming Radiolarian organism lives, and the +numerous dangers which beset it in the struggle for existence, would lead +_a priori_ to the expectation, that many special protective adaptations +would be developed by natural selection. On the other hand, morphological +experience shows us that this latter has been in action for immeasurable +periods, and has gradually produced an abundance of the most remarkable +protective modifications. Examples of these may be found in the formation +of the voluminous calymma, as a gelatinous protective covering for the +central capsule, and further, the formation of the capsule membrane itself, +which separates the generative contents of the central capsule from the +nutritive exoplasm. The phosphorescence of the central capsule, too (s +223), may be regarded as a useful protective arrangement; as also the +radiating of the numerous pseudopodia in all directions from the surface of +the calymma; for they are of great significance to the {cxliii}well-being +of the organism, both as sensory organs and as prehensile organs. By far +the most important and most varied means for the actual defence of the soft +body is to be seen in the endless modifications of the skeleton; first, in +the production of the enclosing lattice-shells and projecting radial +spines, but especially also in the very varied structure of the individual +parts of the skeleton, and in the special differentiation of the small +appendicular organs which grow out from it (hairs, thorns, spines, scales, +spathillae, anchors, &c.). Finally "mimicry" possesses a considerable +significance among the different forms of adaptation which are to be +observed in this class. + + +223. _Phosphorescence._--Many Radiolarians shine in the dark, and their +phosphorescence presents the same phenomena as that of other luminous +marine organisms; it is increased by mechanical and chemical irritation, or +renewed if already extinguished. The light is sometimes greenish, sometimes +yellowish, and appears generally (if not always) to radiate from the +intracapsular fatty spheres (s 73). Thus these latter unite several +functions, inasmuch as they serve, firstly, as reserve stores of nutriment, +secondly, as hydrostatic apparatus, and thirdly, as luminous organs for the +protection of the Radiolaria; probably the light acts by frightening other +animals, for the phosphorescent animals are provided with spines, +nettle-cells, poison glands or other defensive weapons. The production of +the light depends probably, as in other phosphorescent organisms, upon the +slow oxidation of the fat-globules, which combine with active oxygen in the +presence of alkalis. Phosphorescence is very likely widely distributed +among the Radiolaria. + + The shining of the Radiolaria in the dark has been noticed by the + earliest observers of the class (see L. N. 1, p. 163, L. N. 16, p. 2, and + L. N. 52, pp. 136-139). In the winter of 1859 I observed the production + of light in the case of many monozootic and polyzootic Radiolaria, but + inadvertently omitted to record the fact in my Monograph. I made more + accurate observations in the winter of 1866 at Lanzerote in the Canary + Islands, and convinced myself the the light emanates from the central + capsule, and in particular from the fat-globules contained in it. In most + Polycyttaria (both #Collosphaerida# and #Sphaerozoida#), when each + central capsule contains a large central oil-globule the light radiates + from it. In _Collozoum serpentinum_ (Pl. 3, figs. 2, 3) each cylindrical + central capsule contains a row of luminous spherules like a string of + beads. In _Alacorys friderici_ (Pl. 65, fig. 1) the four-lobed central + capsule contains four shining points. Karl Brandt has recently made more + detailed communication on this point (L. N. 52, p. 137). + + +224. _Sensation._--The general irritability which we ascribe to all +organisms, and as the basis of which we regard the protoplasm, remains at +an inferior stage of development in the Radiolaria. For although they are +subject to various stimuli, and certainly possess a power of +discrimination, special sensory organs are not differentiated; the +peripheral portions of the protoplasm, and especially the pseudopodia, +rather act both as organs of the different kinds of sensation and various +modes of motion. That different Radiolaria have attained different degrees +of development in this respect may be seen {cxliv}partly by direct +observation of the reaction of the living organism towards various stimuli, +and partly by the comparison of the different conditions of existence under +which Radiolarians exist, both in the most various depths of the ocean and +in all climatic zones (see note A). In general the Radiolaria seem to be +sensitive to the following stimuli; (1) pressure (see note B); (2) +temperature (see note C); (3) light (see note D); (4) chemical composition +of the sea-water (see note E). The reaction towards these stimuli, +corresponding to the sensation of pleasure or dislike which they call +forth, is shown in various forms of motion of the protoplasm, changes in +the currents in it, contraction of the central capsule, changes in the +size, position, and form of the pseudopodia, changes in the volume of the +calymma (by the evocation of water), &c. Among the sensory functions of the +Radiolaria must be especially mentioned their remarkably developed +perception of hydrostatic equilibrium (see note F), as well as their +perception of distances, so clearly shown in the production of equal +lattice-meshes and other regularly formed skeletal structures (see note G). + + A. I can add but little to the communication which I made twenty-four + years ago regarding sensation in the Radiolaria (L. N. 16, pp. 128-131). + The most important point would be the great difference in irritability + which must obtain between the pelagic, zonarial and abyssal Radiolaria, + which may be assumed from a consideration of their very different + conditions of existence as regards pressure, light, warmth, nutrition, + &c. It is natural to suppose that the numerous abyssal Radiolaria, + discovered by the Challenger, which live at great depths (2000 to 4500 + fathoms) in complete darkness, in icy cold and under an enormous + pressure, must have quite different sensations of pleasure from their + pelagic relatives which live at the surface of the sea under an + equatorial sun. Karl Brandt has recently added much to our knowledge + regarding the special action of different vital conditions upon the + various Polycyttaria and the degrees of their irritability (L. N. 52, pp. + 113-132). + + B. Regarding the sensation of pressure or sensation of touch of the + Radiolaria and the various degrees of their mechanical irritability, see + L. N. 16, p. 129; L. N. 41, p. 464. + + C. Regarding the sensation of warmth or temperature-sense and its + dependence upon different climatic relations, see L. N. 16, p. 129; L. N. + 52, pp. 114-129. + + D. Regarding the sensation of light, compare L. N. 16, p. 128; L. N. 42, + p. 304; L. N. 52, pp. 102-104, 114. + + E. Regarding the sense of taste of the Radiolaria or their peculiar + sensitiveness towards the different chemical composition of the water, + change in its salinity, presence of organic impurities, &c., see L. N. + 16, p. 130; L. N. 52, pp. 103, 113. This chemical irritability seems to + be the most highly developed sense in the Radiolaria, even more so than + their mechanical irritability. + + F. The perception of hydrostatic equilibrium among the Radiolaria is + immediately visible from the position which their bodies, floating freely + in the water, assume spontaneously, and from the symmetrical development + of the skeleton, which by its gravitation necessitates a definite + position. It may be assumed that the development of the various + geometrical ground forms which correspond to a definite position of + equilibrium, is the result of this particular kind of perception (compare + ss 40-45). + + {cxlv}G. The plastic perception of distance of the pseudopodia is shown + by the symmetry with which the forms composing the regular skeletal + structures (_e.g._, the ordinary lattice-spheres with regular hexagonal + meshes, the radial spines with equidistant branches) are excreted from + the exoplasm. Both this form of sensation and the one first mentioned + (note F) have hitherto received scarcely any attention, but are deserving + of a thorough physiological investigation. + + +225. _The Cell-Soul (Zellseele)._--The common central vital principle, +commonly called the "soul," which is considered to be the regulator of all +vital functions, appears in the Radiolaria as in other Protista in its +simplest form, as the cell-soul. By the continual activity of this central +"psyche" all vital functions are maintained in unbroken action, and in +uniform correlation. It is also probable that by it the stimulations which +the peripheral portions of the cell receive from the outer world are first +transmitted into true sensation, and that, on the other hand, the volition, +which alone calls forth spontaneous movements, proceeds from it. The +central capsule is most likely the sole organ of this cell-soul or central +psychic organ, and the active portion may be either the endoplasm or the +nucleus, or both. The central capsule may thus (apart from its function as +a sporangium, s 215) be regarded as a simple ganglion cell, physiologically +comparable to the nervous centre of the higher animals, whilst the exoplasm +(sarcomatrix and pseudopodia) are to be compared to the peripheral nervous +system and sense organs of the latter. The great simplicity of the +functions of the cell-soul which appear in the Radiolaria, and the intimate +connection of their different psychic activities, give to these unicellular +Protista a special significance for the comprehension of the monistic +elements of a natural psychology. + + Regarding the theory of the cell-soul as the only psychological theory + which is able to explain naturally the true nature of the life of the + soul in all organisms as well as in man, see my address on cell-souls and + soul-cells ("Zellseelen und Seelenzellen") in Gesammelte populaere + Vortraege aus dem Gebiete der Entwickelungslehre, Heft 1, p. 143; Bonn, + 1878. + + + + +{cxlvi}CHOROLOGICAL SECTION. + + +---- + + +CHAPTER IX.--GEOGRAPHICAL DISTRIBUTION. + +(ss 226-240.) + +226. _Universal Marine Distribution._--Radiolaria occur in all the seas of +the world, in all climatic zones and at all depths. Probably under normal +conditions they always float freely in the water, whether their usual +position be at the surface (pelagic), or at a certain depth (zonarial), or +near to the bottom of the sea (abyssal). This appears both from numerous +direct observations, as well as from conclusions which may be drawn from +their organisation (and especially their promorphology) regarding their +floating life (compare ss 40-50, 219, 220). Hitherto no observation has +been recorded, which justifies the assumption that Radiolaria live anywhere +upon the bottom of the sea (on stones, Algae, or other firm substances), +either sessile or creeping. They perform the latter action, however, when +they fall accidentally upon a firm basis or are accidentally placed upon +it, but they seem normally always to float freely in the water with +pseudopodia radiating in all directions. Active free-swimming movements are +only met with in the case of the flagellate zoospores (s 142). The +development of Radiolaria in large masses is very remarkable (see note A), +and in many parts of the ocean is so great that they play an important part +in the economy of marine life, especially as food for other pelagic and +abyssal animals (see note B). Medium salinity of the water seems to be most +favourable to their development in masses, although it is not unknown in +seas of high and low salinity (see note C). There are no Radiolaria in +fresh water (see note D). + + A. The development of Radiolaria takes place in many parts of the ocean + in astonishingly large masses on the surface, in different strata, and + near the bottom. The #Collodaria# (and especially the Sphaerozoida) often + cover the surface of the sea in millions, and form a shining layer, + phosphorescent in the dark like the _Noctilucae_, as I observed in 1859 + in the Strait of Messina, in 1866 at the Canaries, and in 1881 in the + Indian Ocean. Similar masses of _Sphaerozoum_ and _Acanthometron_ were + seen by Johannes Mueller on the French and Ligurian coasts (L. N. 12), + and John Murray found another in the Gulf Stream, off the Faeroee + Islands, from the surface to a depth of 600 fathoms; considerable masses + of large PHAEODARIA live there also. + + B. The alimentary canal of Medusae, Salpae, Crustacea, Pteropoda, and + many other pelagic animals is a rich field for the discovery of + Radiolaria, and many of the species hereinafter described are from such + sources. Fossil coprolites too (_e.g._, those from the Jura) often + contain many Polycystina. + + C. Some ACANTHARIA (#Acanthometra#) and PHAEODARIA (species of _Mesocena_ + and _Dictyocha_) {cxlvii}live in the Baltic; I found their skeletons in + the alimentary canal of _Aurelia_, Ascidians and Copepods. + + D. The so-called "fresh-water Radiolaria," which have been described by + Focke, Greeff, Grenacher and others, are all Heliozoa, without either + central capsule or calymma. + + +227. _Local distribution._--As regards their local distribution and its +boundaries the Radiolaria show in general the same relations as other +pelagic animals. Since they are only to a very slight extent, if at all, +capable of active horizontal locomotion, the dispersion of the different +species from their point of development (or "centre of creation") is +dependent upon oceanic currents, the play of winds and waves and all the +accidental causes which influence the transport of pelagic animals in +general. These passive migrations are here, however, as always, of the +greatest significance, and bring about the wide distribution of individual +species in a far higher degree than any active wanderings could do. Any one +who has ever followed a stream of pelagic animals for hours and seen how +millions of creatures closely packed together are in a short time carried +along for miles by such a current, will be in no danger of underestimating +the enormous importance of marine currents in the passive migration of the +fauna of the sea. Such constant currents may, however, be recognised both +near the bottom of the sea and at various depths, as well as at the +surface, and are therefore of just as much significance for the abyssal and +zonarial as for the pelagic Radiolaria. It is easy to explain by this means +how it is that so many animals of this class (probably indeed the great +majority) have a wide range of distribution. The number of _cosmopolitan_ +species which live in the Pacific, Atlantic and Indian Oceans is already +relatively large. In each of these three great ocean basins, too, many +species show a wide distribution. On the other hand, there are very many +species which are hitherto known only from one locality, and probably many +small local faunas exist, characterised by the special development of +particular groups. The observations which we at present possess are too +incomplete, and the rich material of the Challenger is too incompletely +worked out, to enable any definite conclusions to be drawn regarding the +local distribution of Radiolaria. + + The statements made in the systematic portion of this Report regarding + the distribution of the Challenger Radiolaria are very incomplete. In + most cases only one locality is mentioned, and that is the station (s + 240) in the preparations or bottom deposit from which I first found the + species in question. Afterwards I often found the same species again in + one or more additional stations (not seldom in numerous preparations both + from the Pacific and Atlantic), without the possibility of adding them to + the habitat recorded under the description. The necessary accurate + determination and identification of the species (measuring the different + dimensions, counting the pores, &c.), would have occupied too much time, + and the writing of this extensive Report would have lasted not ten but + twenty or thirty years. + + +228. _Horizontal Distribution._--From the extensive collections of the +Challenger and from the other collections which have furnished a welcome +supplement to them, it appears {cxlviii}that Radiolaria are distributed +throughout all seas without distinction of zones and physical conditions, +even though these latter may be the cause of differences in their +qualitative and quantitative development. In the case of the Radiolaria as +well as of many other classes of animals, the law holds good that the +richest development of forms and the greatest number of species occurs +between the tropics, whilst the frigid zones (both Arctic and Antarctic) +exhibit great masses of individuals, but relatively few genera and species +(see note A). In the Challenger collection the greatest abundance of +species of Radiolaria is exhibited by those preparations which were +collected at low latitudes in the immediate neighbourhood of the equator; +this is true both of the Atlantic (Stations 346 to 349) and of the Pacific +(Stations 266 to 274); in the former the richest of all is Station 347 +(lat. 0d 15' S.), in the latter Station 271 (lat. 0d 33' S.) (see note B). +From the tropics the abundance of species seems to diminish regularly +towards the poles, and more rapidly in the northern than in the southern +hemisphere; the latter also appears, considered as a whole, to possess more +species than the former. A limit to the life of the Radiolaria towards the +poles has not yet been found; the expeditions towards the North Pole (see +note C), like those towards the South (see note D), have obtained +bottom-deposits and ice enclosures which contained Radiolaria; in some of +the most northerly and most southerly positions which were reached the +number of Radiolaria enclosed in the ice was relatively great. + + A. The greater abundance of Radiolaria in the tropical seas is probably + to be explained by the more favourable conditions of existence, and in + particular the larger quantity of nutritive material (especially of + decayed animals) and not by the higher temperature of the surface, for at + depths of from 2000 to 3000 fathoms where the abyssal Radiolaria live, + the temperature is but little above the freezing point or even below it + (compare the bottom temperatures in the list of Challenger Stations, s + 240). + + B. Station 271 of the Challenger Expedition, situated almost on the + equator in the Mid Pacific (lat. 0d 33' S.), exceeds all other parts of + the earth, hitherto known, in respect of its wealth in Radiolaria, and + this is true of the pelagic as well as of the zonarial and abyssal forms. + In the Station List the deposit at this point is stated to be + "Globigerina ooze"; but after the calcareous matter has been removed by + means of acid, the purest Radiolarian ooze remains, rich in varied and + remarkable species. More than one hundred new species have been described + from this Station alone. + + C. Regarding the Arctic Radiolaria compare the contributions of Ehrenberg + (L. N. 24, pp. 138, 139, 195) and Brady on the English North Polar + Expedition, 1875-76 (Ann. and Mag. Nat. Hist., 1878, vol. i. pp. 425, + 437). + + D. Regarding the Antarctic Radiolaria, compare s 230, note A, and + Ehrenberg, Mikrogeologie (L. N. 6, Taf. xxxv., A.), also L. N. 24, pp. + 136-139. + + +229. _Fauna of the Pacific Ocean._--From the splendid discoveries of the +Challenger, and the supplementary observations obtained from other sources, +the Pacific seems to be the ocean basin which is richest both +quantitatively and qualitatively in Radiolarian life, {cxlix}excelling both +the Indian and Atlantic Oceans in this respect. It may be assumed with +great probability that by far the largest portion of the Pacific has a +depth of between 2000 and 3000 fathoms, and that its bottom is covered +either with Radiolarian ooze (s 237) or with a red clay (s 239), which +contains many SPUMELLARIA and NASSELLARIA, and has probably been derived +for a great part from broken down and metamorphosed Radiolarian ooze (see +note A). Pure Radiolarian ooze was found by the Challenger eastwards in the +Central Pacific (over a wide area between lat. 12d N. and 12d S., Stations +265 to 274), and also westwards in the latitude of the Philippines, twenty +degrees to the east of them (between lat. 5d N. and 15d N.). The great +abundance of Radiolaria present in the neighbourhood of the Philippines and +in the Sunda Sea was already known from other investigations (note B). The +red clay also, which covers a great part of the bottom of the North +Pacific, and which was obtained of very constant composition by the +Challenger between lat. 35d N. and 38d N., from Japan to the meridian of +Honolulu (from long. 144d E. to 156d W.), is so pre-eminently rich in +Radiolaria that it often approaches in composition the Radiolarian ooze, +and has probably been derived from it. The track of the Challenger through +the tropical and northern parts of the Pacific describes nearly three sides +of a rectangle, which includes about half of the enormous Pacific basin, +and from this as well as from other supplementary observations it may with +great probability be concluded that by far the largest part of the bed of +the Pacific (at least three-fourths) is covered either with Radiolarian +ooze or with red clay, which contains a larger or smaller amount of the +remains of Radiolaria. With this agrees also the important fact that the +numerous preparations of pelagic materials and collections of pelagic +animals, which were collected by the Challenger in the Pacific, almost +always indicate a corresponding amount of Radiolarian life on the surface. +This is true in particular also of the South Pacific, between lat. 33d S. +and 40d S. (from long. 133d W. to 73d W., Stations 287 to 301); the surface +of this southern region and the different bathymetrical zones were rich in +new and peculiar species of Radiolaria. + + A. Many specimens of bottom-deposits from the Pacific, which are entered + in the Challenger lists either as "red clay" or "Globigerina ooze," + contain larger or smaller quantities of Radiolaria, and the number of + different species of SPUMELLARIA and NASSELLARIA which they contain is + often so great that the deposit might have been almost as appropriately + termed "Radiolarian ooze," _e.g._, Stations 241 to 245, and 270, 271 + (compare ss 236-239). + + B. Pacific Radiolarian ooze was first obtained by Lieutenant Brooke (May + 11, 1859) between the Philippines and Marianne Islands, from a depth of + 3300 fathoms (lat. 18d 3' N., long. 129d 11' E.). Ehrenberg, who first + described it, found seventy-nine different species of Polycystina in it, + and reported "that their quantity and the number of different forms + increased with the depth" (Monatsber. d. k. preuss. Akad. d. Wiss. + Berlin, 1860, pp. 466, 588, 766). + + +230. _Fauna of the Indian Ocean._--As regards its Radiolarian fauna the +Indian Ocean is the least known of the three great basins. Still the few +limited spots, regarding which {cl}investigations are forthcoming, indicate +a very rich development of Radiolarian life. Probably it approaches more +nearly the fauna of the Pacific than that of the Atlantic, both as regards +the abundance and the morphological characters of its species. The +researches of the Challenger are very limited and incomplete as regards the +Indian Ocean, for the expedition only just touched upon this great ocean +basin (2000 to 3000 fathoms deep) at its two extremities (westwards at the +Cape of Good Hope and eastwards at Tasmania), its course lying for the most +part south of lat. 45d S. and extending beyond lat. 65d S. (from Station +149 to 158, south of lat. 50d S.). It is true that this portion of the +South Indian Ocean was shown to contain Radiolaria everywhere, but these +were more plentiful in individuals than in species. Only from Station 156 +to Station 159 (between lat. 62d and 47d S., and long. 95d and 130d E.) was +the bottom, which consisted partly of Diatom ooze and partly of Globigerina +ooze, richer in species (see note A). The gaps left by the Challenger in +the investigation of the Indian Ocean, have, however, been to some extent +filled from other sources. As early as 1859 the English "Cyclops" +expedition had shown that the bottom of the Indian Ocean to the east of +Zanzibar (lat. 9d 37' S., long. 61d 33' W.) is covered with pure +Radiolarian ooze (see note B). Also since the Tertiary rocks of the Nicobar +Islands are for the most part of the same composition, and since a great +abundance of Radiolaria has been shown to be present both in the east part +of the ocean, between the Cocos Islands and the Sunda Archipelago (see note +C), and in the northern part or Arabian Sea between Socotra and Ceylon (see +note D); it may be assumed with great probability that the greater part of +the basin of the Indian Ocean, like that of the Pacific, is covered either +with Radiolarian ooze or with the characteristic red clay. With this agrees +the richness of the surface of the Indian Ocean in Radiolaria of the most +various groups, which has been more extensively demonstrated. + + A. The Radiolarian fauna collected by the Challenger on the voyage from + the Cape to Melbourne, shows in part, namely, from Station 156 to Station + 158, very peculiar and characteristic composition; in particular, the + Diatom ooze of Station 157 passes over in great part into a Radiolarian + ooze, mainly composed of #Sphaerellaria#. This is worthy of a more + thorough investigation than I was able, owing to lack of material and + time, to give it. + + B. The remarkably pure Radiolarian ooze of Zanzibar, discovered by + Ehrenberg in 1859, was the earliest known recent example of that deposit. + It was brought up by Captain Pullen of the English man-of-war "Cyclops," + from a depth of 2200 fathoms, between Zanzibar and the Seychelles, and + "under a magnifying power of 300 diameters, showed at the first glance a + mass of almost pure Polycystina, such as no sample of a deep-sea deposit + has hitherto shown. It is very noticeable that in the whole of this mass + of living forms, no calcareous shells are to be seen" (Ehrenberg, L. N. + 24, pp. 148, 149). + + C. For the most important material from the Indian Ocean, I am indebted + to Captain Heinrich Rabbe of Bremen, who during many voyages in the + Indian Ocean, in his ship "Joseph Haydn," made numerous collections in + different localities with the tow-net and the trawl, and admirably + preserved the rich collections thus made. The greatest abundance of + Radiolaria was found in those {cli}obtained to the east of Madagascar, + and next in those from the neighbourhood of the Cocos Islands. I take + this opportunity of expressing my thanks to Captain Rabbe for the + liberality with which he placed all this valuable material at my + disposal. + + D. On my voyage from Aden to Bombay, and thence to Ceylon (1881), and + especially on my return journey from Ceylon, between the Maldive Islands + and Socotra (1882), I carried on a number of experiments with a surface + net, which yielded a rich fauna of pelagic animals, and among them many + new species of Radiolaria, for observation. On several nights when the + smooth surface of the Indian Ocean, unrippled by any wind, shone with the + most lovely phosphorescent light, I drew up water from the surface with a + bucket, and obtained a rich booty. A number of other new species of + Radiolaria from very various parts of the Indian Ocean I obtained from + the alimentary canal of pelagic animals, such as Medusae, Salpae, + Crustacea, &c. Although the total number of Radiolaria known to me from + the Indian Ocean is much less than from the Atlantic and Pacific, there + are several new genera and numerous species among them, which show that a + careful study of this fauna will be of wide interest. + + +231. _Fauna of the Atlantic Ocean._--The Atlantic Ocean in all parts, of +which the pelagic fauna has been examined, has shown the same constant +presence of Radiolaria, and in certain parts of its abyssal deposits a +larger or smaller quantity of different types belonging to this class; on +the whole, however, its Radiolarian fauna is inferior to that of the +Pacific, and probably also to that of the Indian Ocean, both in quantity +and quality. Pure Radiolarian ooze, such as is so extensively found on the +floor of the Pacific, and in certain places in that of the Indian Ocean, +has not yet been found in the Atlantic (see s 237). The red clay, too, of +the deep Atlantic does not seem to be so rich in Radiolaria as that of the +Pacific; nevertheless, the number of species peculiar to the Atlantic is +very large, and at certain points the abundance of species as well as of +individuals seems to be scarcely less than in the Pacific. This is +especially true of the eastern equatorial zone not far from Sierra Leone, +Stations 347 to 352 (see note A); also of the South Atlantic between Buenos +Ayres and Tristan da Cunha, Stations 324, 325, 331 to 333 (see note B); +and, lastly, in the North Atlantic in the Gulf Stream and near the Canary +Islands (see note C). The fauna of the latter agrees for the most part with +that of the Mediterranean (see note D). In addition to the material +collected by the Challenger, other deep-sea investigations have furnished +bottom-deposits from different parts of the ocean, which have proved very +rich in Radiolaria (see note E). Furthermore, since the island of Barbados +consists for the most part of fossil Radiolarian ooze, it is very probable +that at certain parts of the tropical Atlantic true Radiolarian ooze, like +that of the Pacific and Indian Oceans, will eventually be found in depths +between 2000 and 3000 fathoms, perhaps over a considerable area. + + A. The tropical zone of the eastern Atlantic seems to be especially rich + in peculiar Radiolaria of different species. This is shown by numerous + preparations from the surface, and from various depths (between lat. 3d + S. and 11d N., and long. 14d W. to 18d W.), which were made towards the + {clii}end of the cruise. Unfortunately no bottom-deposits were obtained + from the most important stations (except Nos. 346 and 347, depths 2350 + and 2250 fathoms) in this region; at these the deposit was a Globigerina + ooze containing numerous different species of Radiolaria. + + B. In the South Atlantic, between Buenos Ayres and Tristan da Cunha + (between lat. 35d S. and 43d S., long. 8d W. and 57d W.) there appears to + be a long stretch covered partly with Globigerina ooze (Stations 331 to + 334), or red clay (Stations 329, 330), partly with blue mud (Stations 318 + to 328), which contains not only large masses of individuals but numerous + peculiar species of SPUMELLARIA and NASSELLARIA. The preparations from + the surface-takings of this region are also rich in these, as well as in + peculiar PHAEODARIA. + + C. The northern part of the Atlantic appears on the whole to be inferior + to the tropical and southern portions as regards its richness in + Radiolaria, and from the western half more especially, only few species + are known. From my researches at Lanzerote in 1866-67, it appears that + the pelagic fauna of the Canary Islands is very rich in them, as is also + the Gulf Stream in the neighbourhood of the Faeroee Channel, according to + the investigations of John Murray (see his Report on the "Knight-Errant" + Expedition, Proc. Roy. Soc. Edin., vol. xi., 1882). + + D. The Radiolaria of the Mediterranean are of special interest, because + almost all our knowledge of these organisms in the living conditions and + of their vital functions has been derived from investigations conducted + on its shores. Johannes Mueller laid the foundation of this knowledge by + his investigations at Messina, and on the Ligurian and French coasts at + Nice, Cette, and St. Tropez (L. N. 10). The many new Radiolaria which I + described in my Monograph (L. N. 16, 1862), were for the most part taken + at Messina, the place which possesses a richer pelagic fauna than any + other, so far as is yet known, in the Mediterranean. Other new species I + found afterwards at Villafranca near Nice, in 1864 (L. N. 19), at + Portofino near Genoa (1880), at Corfu (1877), and at other points on the + coast. In Messina also, Richard Hertwig collected the material for his + valuable treatise on the Organisation of the Radiolaria (L. N. 33), after + he had previously made investigations into their histology at Ajaccio in + Corsica (L. N. 26). Lastly, at Naples, Cienkowski (L. N. 22) and Karl + Brandt (L. N. 38, 39, 52) carried out their important investigations into + the reproduction and symbiosis of the Radiolaria. With respect to the + character of its Radiolaria, the Mediterranean fauna is to be regarded as + a special province of the North Atlantic. + + E. Among the smaller contributions which have been made towards our + knowledge of the Atlantic Radiolarian fauna, the communications of + Ehrenberg on the deposits obtained in sounding for the Atlantic cable, + and on the Mexican Gulf Stream near Florida, deserve special mention (L. + N. 24, pp. 138, 139-145). + + +232. _Vertical Distribution._--The most important general result of the +discoveries of the Challenger, as regards the vertical or bathymetrical +distribution of the Radiolaria, is the interesting fact that numerous +species of this class are found living at the most various depths of the +sea, and that certain species are limited to particular bathymetrical +zones, _i.e._, are adapted to the conditions which obtain there. In this +respect three different Radiolarian faunas may be distinguished, which may +be shortly termed "pelagic," "zonarial," and "abyssal." The _pelagic_ +Radiolaria swim at the surface, and when they sink (_e.g._, in a stormy +sea), only descend to a small depth, probably not more than from {cliii}20 +to 30 fathoms (s 233). The complicated conditions of existence created by +the keen struggle for existence at the surface of the sea, give rise to the +formation of very numerous pelagic species, especially of Porulosa +(SPUMELLARIA and ACANTHARIA). The _abyssal_ Radiolaria are very different +from those just mentioned; they live at the bottom of the deep-sea, not +resting upon nor attached to it, but probably floating at a little distance +above it, and are adapted to the conditions of existence which obtain there +(s 235). Here the Osculosa (NASSELLARIA and PHAEODARIA) seem to +predominate. The _zonarial_ Radiolaria live floating at various depths +between the pelagic and abyssal species (s 234). In their morphological +characters they gradually approach the pelagic forms upwards and the +abyssal downwards. + + The views which have hitherto been held regarding the bathymetrical or + vertical distribution of the Radiolaria have been entirely altered by the + magnificent discoveries of the Challenger, and especially by the + important observations of Sir Wyville Thomson (L. N. 31) and John Murray + (L. N. 27). These two distinguished deep-sea explorers have, as a result + of their wide experience, been convinced that Radiolaria exist at all + depths of the ocean, and that there are large numbers of true deep-sea + species which are never found at the surface of the sea nor at slight + depths (L. N. 31, vol. i. pp. 236-238; L. N. 27, pp. 523, 525). The + result of my ten years' work upon the Challenger Radiolaria, and the + comparative study of more than a thousand mountings from all depths, has + only been to confirm this opinion, and I am further persuaded that it + will some day be possible by the aid of suitable nets (not yet invented) + to distinguish different faunistic zones in the various depths of the + sea. In this connection may be mentioned the specially interesting fact + that the species of Radiolaria of one and the same family present in the + different depths characteristic morphological distinctions, which + obviously correspond to their different physiological relations in the + struggle for existence. Owing to those extensive discoveries, the + representation which I gave in my Monograph (1862, L. N. 16, pp. 172-196) + of the vertical distribution of the Radiolaria, and of their life in the + greatest depths of the sea, has been entirely changed. Compare also + Buetschli (L. N. 41, p. 466). + + +233. _The Pelagic Fauna._--The surface of the open ocean seems everywhere, +at a certain distance from the coast at least, to be peopled by crowds of +living Radiolaria. In the tropical zone these pelagic crowds consist of +many different species, whilst in the frigid zones, on the other hand, they +are made up of many individuals belonging to but few species. Most of these +inhabitants of the surface may be regarded as truly pelagic species, which +either remain always at the surface or descend only very slightly below it. +Probably most Porulosa (both SPUMELLARIA and ACANTHARIA) belong to this +group; whilst but few Osculosa occur in it, and fewer PHAEODARIA than +NASSELLARIA. In general the pelagic Radiolaria are distinguished from the +abyssal by the more delicate and slender structure of their skeletons; the +pores of the lattice-shells are larger, the intervening trabeculae thinner; +the armature of spines, spathillae, anchors, &c., is more various and more +highly developed. Numerous forms are to be found among the pelagic +{cliv}Radiolaria which have either an incomplete skeleton or none at all. +When the pelagic forms leave the surface on account of unfavourable +weather, they appear only to sink to slight depths (probably not below 20 +or 30 fathoms). Within the limits of the same family the size of the +pelagic species seems to be on an average greater than that of the related +abyssal forms. + + +234. _The Zonarial Fauna._--Between the pelagic fauna living at the surface +of the open sea and the abyssal, which floats immediately over the bottom, +there appears to be usually a middle fauna, which inhabits the different +bathymetrical zones of the intermediate water, and hence may be shortly +called the "zonarial" fauna. The different species of Radiolaria which +inhabit these different strata in the same vertical column of water present +differences corresponding to those of the plants composing the several +zones of vegetation, which succeed each other at different heights on a +mountain; they correspond to the different conditions of existence which +are presented by the different strata of water, and to which they have +become adapted in the struggle for existence. The existence of such +bathymetrical zones has been shown by those important, if not numerous, +observations of the Challenger, in which the tow-net was used at different +depths at one and the same Station. In several cases the character of the +Radiolarian fauna at different depths presented characteristic differences. + + For the present, and until we are better acquainted with the characters + of the Radiolarian fauna at different depths, we may distinguish + provisionally the following _five bathymetrical zones_:--(1) The + _pelagic_ zone, extending from the surface to a depth of about 25 + fathoms; (2) the _pellucid_ zone, extending from 25 to 150 fathoms, or as + far as the influence of the sunlight makes itself felt; (3) the _obscure_ + zone, extending from 150 to 2000 fathoms, or from the depth at which + sunlight disappears to that at which the influence of the water + containing carbonic acid begins and the calcareous organisms vanish; (4) + the _siliceous_ zone, extending from 2000 or 2500 to about 3000 fathoms, + in which only siliceous not calcareous Rhizopoda are found, and in which + the peculiar conditions of the lowest regions have not yet appeared; (5) + the _abyssal_ zone, in which the accumulation of the oceanic deposits, + and the influence of the bottom currents, create new conditions of + existence. So far as our isolated and incomplete observations of the + zonarial Radiolarian fauna extend, it appears that the subclass Porulosa + (SPUMELLARIA and ACANTHARIA) predominates in the two upper zones, and as + the depth increases is gradually replaced by the subclass Osculosa + (NASSELLARIA and PHAEODARIA), so that the latter predominates in the two + lowest zones. The obscure zone which lies in the middle is probably the + poorest in species. In general, the morphological characters of the + zonarial fauna appear to change gradually upwards into the delicate form + of the pelagic and downwards into the robust constitution of the abyssal; + so also the average size of the individuals (within the limits of the + same family) appears to increase upwards and decrease downwards. + + +235. _The Abyssal Fauna._--The great majority of Radiolaria which have +hitherto been observed, and which are described in the systematic portion +of this Report, have been obtained from the bottom of the deep-sea, and +more than half of all the species have been {clv}derived from the pure +Radiolarian ooze, which forms the bed of the Central Pacific at depths of +from 2000 to 4000 fathoms (s 237). Many of these abyssal forms were brought +up with the malacoma uninjured, and they show, both when mounted +immediately in balsam, and when preserved in alcohol, all the soft parts +almost as clearly as fresh preparations of pelagic Radiolaria. These +species are to be regarded as truly abyssal, _i.e._, as forms which live +floating only a little distance above the bottom of the deep-sea, having +become adapted to the peculiar conditions of life which obtain in the +lowest regions of the ocean. Probably the majority of the PHAEODARIA belong +to these abyssal Radiolaria, as well as a large number of NASSELLARIA, but +on the other hand, only a small number of ACANTHARIA and SPUMELLARIA are +found there. A character common to these abyssal forms, and rarely found in +those from the surface or from slight depths, is found in their small size +and their heavy massive skeletons, in which they strikingly resemble the +fossil Radiolaria of Barbados and the Nicobar Islands. The lattice-work of +the shell is coarser, its trabeculae thicker and its pores smaller than in +pelagic species of the same group; also the apophyses (spines, spathillae, +coronets, &c.), are much less developed than in the latter. From these true +abyssal Radiolaria must be carefully distinguished those species whose +empty skeletons, devoid of all soft parts, occur also in the Radiolarian +ooze of the deep-sea, but are clearly only the sunken remains of dead +forms, which have lived at the surface or in some of the upper zones. + + +236. _Deposits containing Radiolaria._--The richest collection of +Radiolaria is found in the deposits of ooze which form the bed of the +ocean. Although the pelagic material skimmed from the surface of the sea, +and the zonarial material taken by sinking the tow-net to various depths, +are always more or less rich in Radiolaria, still the number of species +thus obtained is, on the whole, much less than has hitherto been got merely +from deep-sea deposits. Of course the skeletons found in the mud of the +ocean-bed, may belong either to the abyssal species which live there (s +235), or to the zonarial (s 234), or to the pelagic species (s 233), for +the siliceous skeletons of these latter sink to the bottom after their +death. Almost all these remains found in the deposits belong to the +siliceous "Polycystina" (SPUMELLARIA and NASSELLARIA); PHAEODARIA occur but +sparingly, and ACANTHARIA are entirely wanting, for their acanthin skeleton +readily dissolves. The abundance of Radiolaria varies greatly according to +the composition and origin of the deposits. In general marine deposits may +be divided into two main divisions, terrigenous and abyssal, or, more +shortly, muds and oozes. The _terrigenous_ deposits (or muds) include all +those sediments which are made up for the most part of materials worn away +from the coasts of continents and islands, or brought down into the sea by +rivers. Their greatest extent from the coast is about 200 nautical miles. +They contain varying quantities of Radiolaria, but much fewer than those of +the next group. The _abyssal_ deposits (or oozes) usually commence at a +distance of from 100 to 200 nautical miles {clvi}from the coast. In general +they are characterised by great uniformity, corresponding to the constancy +of the conditions under which they are laid down; they may be divided into +three categories, the true Radiolarian ooze (s 237), Globigerina ooze (s +238), and red clay (s 239). Of these three most important deep-sea +formations the first is by far the richest in Radiolaria, although the +other two contain often very many siliceous shells. + + The marvellous discoveries of the Challenger have thrown upon the nature + of marine deposits an entirely new light, which justifies most important + conclusions regarding the geographical distribution and geological + significance of the Radiolaria. Since Dr. John Murray and the Abbe Renard + will treat fully of these interesting relations in a forthcoming volume + of the Challenger series (Report on the Deep-Sea Deposits), it will be + sufficient here to refer to their preliminary publication already + published (Narrative of the Cruise of H.M.S. Challenger, 1885, vol. ii. + part ii. pp. 915-926); see also the earlier communications by John Murray + (1876, L. N. 27, pp. 518-537), and by Sir Wyville Thomson (The Atlantic, + L. N. 31, vol. i. pp. 206-246). In the Narrative (_loc. cit._, p. 916) + the following table of marine deposits is given:-- + + {Shore formations, } Found in inland + {Blue mud, } seas and along the + {Green mud and sand, } shores of + {Red mud, } continents. + Terrigenous deposits.{ + {Volcanic mud and sand, } Found around oceanic + {Coral mud and sand, } islands and along the + {Coralline mud and sand, } shores of continents. + + {Globigerina ooze, } Found in the abysmal + {Pteropod ooze, } regions of the + Abysmal deposits. {Diatom ooze, } ocean basins. + {Radiolarian ooze, } + {Red clay, } + +237. _Radiolarian Ooze._--By Radiolarian ooze, in the strict sense of the +term, are understood those oceanic deposits, the greater part of which +(often more than three-quarters) is composed of the siliceous skeletons of +this class. Such _pure_ Radiolarian ooze has only been found in limited +areas of the Pacific and Indian Oceans. It is most conspicuous in the +Central Pacific, between lat. 12d N. and 8d S., long. 148d W. to 152d W., +the depth being everywhere between 2000 and 3000 fathoms (Stations 266 to +268 and 272 to 274). In the deepest of the Challenger soundings (Station +225, 4475 fathoms) the bottom is composed of pure Radiolarian ooze, as well +as at the next Station in the Western Tropical Pacific (Station 226, 2300 +fathoms), the latitude varying from 12d N. to 15d N., and the longitude +from 142d E. to 144d E. In the Indian Ocean also, pure Radiolarian ooze was +found in the year 1859 between Zanzibar and the Seychelles, this being the +first known example of it (s 230). On the other hand, it has not yet been +found in the bed of the Atlantic; but the Tertiary formations of Barbados +(Antilles, s 231) like those of the Nicobar Islands (Further India), are to +be regarded as pure Radiolarian {clvii}ooze in the fossil condition. +_Mixed_ Radiolarian ooze is the name given to those deposits in which the +Radiolaria exceed any of the other organic constituents, although they do +not make up half the total mass. To this category belong a large number of +the Challenger soundings which are entered in the Station list either as +red clay or Globigerina ooze. Such mixed Radiolarian ooze has been +discovered (A) in the North Pacific in an elongated area of red clay +extending from Station 241 to Station 245 (perhaps even from Station 238 to +Station 253), that is, at least, from long. 157d E. to 175d E., between +lat. 35d N. and 37d N.; (B) in the tropical Central Pacific in the +Globigerina ooze of Stations 270 and 271. The ooze from the latter station, +situated almost on the equator (lat. 0d 33' S., long. 151d 34' W.), is +specially remarkable, for it has yielded more new species of SPUMELLARIA +and NASSELLARIA than any other Station, not excluding even the neighbouring +Stations 268, 269, and 272. Probably such mixed Radiolarian ooze is very +widely distributed in the depths of the ocean, as, for example, in the +South Pacific (Stations 288, 289, 300, and 302), and in the Southern Ocean +(Stations 156 to 159); also in the South Atlantic (Stations 324, 325, 331, +332) and in the tropical Atlantic (Stations 348 to 352). When carefully +purified and decalcified by acids, Radiolarian ooze appears as a fine +shining white powder; in the raw state it is yellowish or reddish, +sometimes reddish-brown or dark brown in colour, according to the quantity +of oxides of iron, manganese, &c., which it contains. Calcareous skeletons +(especially the tests of pelagic Foraminifera) do not occur at all or only +in very minute quantities in _pure_ Radiolarian ooze from more than 2000 +fathoms, whilst specimens of _mixed_ ooze often contain considerable +quantities of them. + + Pure Radiolarian ooze was first described by Dr. John Murray as regards + its peculiar nature and composition under the name "Radiolarian ooze" + (1876, L. N. 27, pp. 525, 526); compare also Sir Wyville Thomson (The + Atlantic, L. N. 31, vol. i. pp. 231-238), and John Murray (Narr. Chall. + Exp., L. N. 53, vol. i. pt. ii. pp. 920-926, pl. N. fig. 2). The + different specimens of pure Radiolarian ooze obtained by the Challenger + from the Pacific, and handed to me for investigation, are from depths of + from 2250 fathoms to 4475 fathoms, and may be divided according to their + composition into three different groups:--I. The Radiolarian ooze of the + Western Tropical Pacific, Stations 225 and 226, from depths of 4475 and + 2300 fathoms (lat. 11d N. to 15d N., and long. 142d E. to 144d E.). II. + The Radiolarian ooze of the northern half of the Central Pacific, + Stations 265 to 269, from depths of 2550 to 2900 fathoms. III. The + Radiolarian ooze of the southern half of the Central Pacific, Stations + 270 to 274, from depths of 2350 to 2925 fathoms. A fourth group would be + constituted by the Radiolarian ooze from the Philippines, which was + brought up by Brooke in 1860 near the Marianne Islands from 3300 fathoms, + and described by Ehrenberg (Monatsber. d. k. preuss. Akad. d. Wiss. + Berlin, 1860, p. 765). The Diatom ooze, too, found by the Challenger in + the Antarctic regions (Stations 152 to 157) is in some parts so rich in + Radiolaria that it passes over into true Radiolarian ooze. Regarding the + Radiolarian ooze from Zanzibar, obtained by Captain Pullen in 1859 from + 2200 fathoms (s 230), we have only the incomplete communications of + Ehrenberg (L. N. 24, p. 147). A more accurate knowledge of these deposits + from the Indian Ocean, and of {clviii}those which we may with probability + expect from the tropical eastern Atlantic, will be sure to increase very + widely our knowledge of the class. + + +238. _Globigerina Ooze._--Next to the Radiolarian ooze proper the +Globigerina ooze is the deposit which is richest in the remains of +Radiolaria. Often these are so abundant that it is doubtful to which +category the specimen should be referred (_e.g._, Stations 270 and 271, see +s 237). In fact, the two pass without any sharp boundary into each other, +and both present transitions to the Diatom ooze. Next to red clay (s 239), +Globigerina ooze is the most widely distributed of all sediments, and forms +a large part of the bed of the ocean at depths of 250 to 2900 fathoms +(especially between 1000 and 2000 fathoms). It covers extensive areas at +depths below 1800 fathoms, and in still deeper water is replaced by red +clay. It is a fine-grained white, grey, or yellowish powder, which +sometimes becomes coloured rose, red, or brown owing to the admixture of +oxides of iron and manganese. True Globigerina ooze consists for the most +part of the accumulated calcareous shells of pelagic Foraminifera, +principally _Globigerina_ and _Orbulina_, but also _Hastigerina_, +_Pulvinulina_, &c. It contains usually from 50 to 80 per cent. of calcium +carbonate, the extreme values being 40 and 95 per cent. After this has been +removed by acids, there remains a residue, which consists partly of the +siliceous shells of Radiolaria and Diatoms, and partly of mineral particles +identical with the volcanic elements of the red clay. + + Regarding the composition and significance of the Globigerina ooze, see + John Murray (L. N. 27, pp. 523-525, and L. N. 53, vol. i. p. 919). + Recently this author has separated from the Globigerina ooze (_sensu + stricto_), the _Pteropod ooze_, distinguished from the former by the + greater abundance of Pteropod shells and calcareous shells of larger + pelagic organisms which it contains. It is found in moderate depths (at + most 1500 fathoms), and contains fewer Radiolaria. + + +239. _Red Clay._--This is quantitatively the most important of all deep-sea +deposits, covering by far the greatest extent of the three great ocean +basins at depths greater than 2200 fathoms. It thus far surpasses in area +the other deposits, both Radiolaria and Globigerina oozes, and commonly +forms a still deeper layer beneath them. Probably these three deep-sea +deposits together cover about three-eighths of the whole surface of the +earth, that is, about as much as all the continents together, whilst only +two-eighths are covered by the terrigenous deposits. Red clay is +principally composed of silicate of alumina, mixed in various proportions +with other finely granular substances; its usual red colour, which +sometimes passes over into grey or brown, is more especially due to +admixture of oxides of iron and manganese. Calcareous matter is usually +entirely wanting, or present only in traces, whilst free silica is found in +very variable, often considerable quantities. The chief mass of the red +clay consists of volcanic ashes, pumice, fragments of lava, &c., whilst a +large part of it is generally composed of shells of Radiolaria or fragments +of {clix}them; in many places the number of well-preserved skeletons +contained in the red clay is very considerable, so that it passes over +gradually into the Radiolarian ooze (_e.g._, in the North Pacific, Stations +238 to 253, see s 237). Hence it may be supposed that a large part of the +red clay consists of decomposed Radiolarian ooze. + + The characteristic composition and fundamental significance of the red + clay in the formation of the deep-sea bed were first made known by the + discoveries of the Challenger (compare John Murray, 1876, L. N. 27, p. + 527, and Narr. Chall. Exp., L. N. 53, vol. i. pt. ii. pp. 920-926, pl. N; + also Wyville Thomson, The Atlantic, L. N. 31, vol. i. pp. 226-229). The + mineral components of the red clay are for the most part of volcanic + origin, due to the decomposition of pumice, lava, &c. Among the organic + remains found in it, the siliceous skeletons of Radiolaria are by far the + most important, and their number is often considerable. A large portion + of the red clay appears to me to consist of broken down Radiolarian + shells, in which a peculiar metamorphism probably has taken place. Sir + Wyville Thomson was of opinion that a considerable proportion of it + consisted of the remains of Globigerina ooze, the calcareous constituents + of which had been removed by the carbon dioxide in the deep-sea water (L. + N. 31, _loc. cit._). Among these remains, however, the siliceous + skeletons of the Radiolaria play a significant and often the most + important part. Furthermore, John Murray has called attention to the fact + that in many deep-sea deposits yellow and red insoluble particles remain, + which unmistakably present the form of Radiolarian shells (L. N. 27, p. + 513). At Station 303 he found "amorphous clayey matter, rounded yellow + minerals, many Radiolaria-shaped;" at Station 302 there was sediment + "consisting almost entirely of small rounded red mineral particles; many + of these had the form of both Foraminifera and Radiolaria; and it seemed + as if some substance had been deposited in and on these organisms." + Similar transitions from well-preserved Radiolarian shells into amorphous + mineral particles I have found in several other specimens of Challenger + soundings, and consider them a further argument for the supposition that + the Radiolaria often take an important share in the formation of the red + clay. + + +240. _List of Stations at which Radiolaria were observed on the Challenger +Expedition._--The 168 Stations recorded below, in soundings or surface +preparations from which I found Radiolaria, belong to the most various +parts of the sea which the Challenger traversed during her voyage round the +world; they constitute about half of the (364) observing Stations contained +in the official list published in the Narrative of the Cruise (Narr. Chall. +Exp., vol. i. part ii. Appendix ii.). + + In addition to the particulars given in the list regarding the + geographical position of the Station, depth, temperature, and composition + of the bottom deposit, I have added the result of my investigations as + regards the relative abundance of the Radiolaria in each. The five + letters (A to E) denote the following degrees of frequency:--A, abundant + Radiolaria (AI, pure Radiolarian ooze; AII, mixed Radiolarian ooze); B, + very numerous Radiolaria (but not a predominating quantity); C, many + Radiolaria (medium quantity); D, few Radiolaria; E, very few Radiolaria + (as they occur almost always). In using these symbols regard has been had + to abundance of the abyssal as well as of the zonarial and pelagic forms + (s 232); sometimes also the estimated number of Radiolaria has been + inserted, based upon information given by John Murray in his Preliminary + Report (L. N. 27), and in the Narrative of the Cruise (L. N. 53), as well + as by Henry B. Brady in his Report on the {clx}Foraminifera (Zool. Chall. + Exp., part xxii., 1884). From Stations 348 to 352 in the Eastern Tropical + Atlantic no specimens of the bottom were obtained, but a rich pelagic + Radiolarian fauna was demonstrated by numerous preparations from the + surface. The depths are given in fathoms and the temperature in degrees + Fahrenheit. In the column describing the nature of the bottom the + following abbreviations are used:-- + + rad. oz. = Radiolarian ooze (s 237). + gl. oz. = Globigerina ooze (s 238). + r. cl. = red clay (s 239). + pt. oz. = Pteropod ooze (see p. clviii). + di. oz. = Diatom ooze (see p. clvii). + bl. m. = blue mud, } terrigenous deposits + gr. m. = green mud, } (see p. clvi). + volc. m. = volcanic mud, } + r. m. = red mud. + + +----------+-----------+--------+------------+-----------+--------------+ + | | | | Bottom | | Relative | + |Challenger| Locality. |Depth in|Temperature,| Nature of | Abundance of | + | Station. | |Fathoms.| d F. | Bottom. | Radiolaria. | + +----------+-----------+--------+------------+-----------+--------------+ + | | | | | | | + | 1. | N. Atl. | 1890 | 36.8 | gl. oz. | D few | + | 2. | " | 1945 | 36.8 | gl. oz. | E very few | + | 5. | " | 2740 | 37.0 | r. cl. | D few | + | 9. | " | 3150 | 36.8 | r. cl. | E very few | + | 24. | Tr. Atl. | 390 | ... | pt. oz. | D few | + | | | | | | | + | 32. | N. Atl. | 2250 | 36.7 | gl. oz. | E very few | + | 45. | " | 1240 | 37.2 | bl. m. | E " | + | 50. | " | 1250 | 38.0 | bl. m. | E " | + | 64. | " | 2700 | ... | r. cl. | D few | + | 76. | " | 900 | 40.0 | pt. oz. | D " | + | | | | | | | + | 98. | Tr. Atl. | 1750 | 36.7 | gl. oz. | C many | + | 106. | " | 1850 | 36.6 | gl. oz. | C " | + | 108. | " | 1900 | 36.8 | gl. oz. | C " | + | 111. | " | 2475 | 33.7 | gl. oz. | C " | + | 120. | " | 675 | ... | r. m. | D few | + | | | | | | | + | 132. | S. Atl. | 2050 | 35.0 | gl. oz. | C many | + | 134. | " | 2025 | 36.0 | gl. oz. | C " | + | 137. | " | 2550 | 34.5 | r. cl. | D few | + | 138. | " | 2650 | 35.1 | r. cl. | D " | + | 143. | S. Ind. | 1900 | 35.6 | gl. oz. | E very few | + | | | | | | | + | 144. | " | 1570 | 35.8 | gl. oz. | E " | + | 145. | " | 140 | ... | volc. s. | D few | + | 146. | " | 1375 | 35.6 | gl. oz. | C many | + | 147. | " | 1600 | 34.2 | di. oz. | C " | + | 148. | " | 210 | ... {| gravel, } | D few | + | | | | {| shells } | | + | | | | | | | + | 149H. | " | 127 | ... | volc. m. | D " | + | 150. | " | 150 | 35.2 | gravel | D " | + | 151. | " | 75 | ... | volc. m. | D " | + | 152. | " | 1260 | ... | di. oz. | C many | + | 153. | " | 1675 | ... | bl. m. | C " | + | | | | | | | + | 154. | " | 1800 | ... | bl. m. | C " | + | 155. | " | 1300 | ... | bl. m. | C " | + | 156. | " | 1975 | ... | di. oz. | B numerous | + | 157. | " | 1950 | 32.1 | di. oz. | B " | + | 158. | " | 1800 | 33.5 | gl. oz. | B " | + | | | | | | | + | 159. | " | 2150 | 34.5 | gl. oz. | B " | + | 160. | " | 2600 | 33.9 | r. cl. | C many | + | 162. | " | 38 | ... | sand | E very few | + | 163. | S. Pac. | 2200 | 34.5 | gr. m. | E " | + | 164A. | " | 1200 | ... | gr. m. | E " | + | | | | | | | + | 165. | S. Pac. | 2600 | 34.5 | r. cl. | D few | + | 166. | " | 275 | 50.8 | gl. oz. | D " | + | 169. | " | 700 | 40.0 | bl. m. | D " | + | 175. | Tr. Pac. | 1350 | 36.0 | gl. oz. | E very few | + | 181. | " | 2440 | 35.8 | r. cl. | E " | + | | | | | | | + | 193. | " | 2800 | 38.0 | bl. m. | D few | + | 195. | " | 1425 | 38.0 | bl. m. | C many | + | 197. | " | 1200 | 35.9 | bl. m. | D few | + | 198. | " | 2150 | 38.9 | bl. m. | C many | + | 200. | " | 250 | ... | gr. m. | B numerous | + | | | | | | | + | 201. | " | 82 | ... | st. & gra.| C many | + | 202. | " | 2550 | 50.5 | bl. m. | B numerous | + | 205. | " | 1050 | 37.0 | bl. m. | C many | + | 206. | " | 2100 | 36.5 | bl. m. | B numerous | + | 211. | " | 2225 | 50.5 | bl. m. | B " | + | | | | | | | + | 213. | " | 2050 | 38.8 | bl. m. | C many | + | 214. | " | 500 | 41.8 | bl. m. | C " | + | 215. | " | 2550 | 35.4 | r. cl. | C many | + | 216A | " | 2000 | 35.4 | gl. oz. | B numerous | + | 217. | " | 2000 | 35.2 | bl. m. | C many | + | | | | | | | + | 218. | " | 1070 | 36.4 | bl. m. | C " | + | 220. | " | 1100 | 36.2 | gl. oz. | C " | + | 221. | " | 2650 | 35.4 | r. cl. | B numerous | + | 222. | " | 2450 | 35.2 | r. cl. | B " | + | 223. | " | 2325 | 35.5 | gl. oz. | B " | + | | | | | | | + | 224. | " | 1850 | 35.4 | gl. oz. | B " | + | 225. | " | 4475 | 35.2 | rad. oz. | A very many | + | 226. | " | 2300 | 35.5 | rad. oz. | A " | + | 230. | N. Pac. | 2425 | 35.5 | r. cl. | C many | + | 231. | " | 2250 | 35.2 | bl. m. | C " | + | | | | | | | + | 232. | " | 345 | 41.1 | gr. m. | C " | + | 234. | " | 2675 | 35.8 | bl. m. | B numerous | + | 235. | " | 565 | 38.1 | gr. m. | D few | + | 236. | " | 775 | 37.6 | gr. m. | C many | + | 237. | " | 1875 | 35.3 | bl. m. | C " | + | | | | | | | + | 238. | " | 3950 | 35.0 | r. cl. | B numerous | + | 239. | " | 3625 | 35.1 | r. cl. | B " | + | 240. | " | 2900 | 34.9 | r. cl. | B " | + | 241. | " | 2300 | 35.1 | r. cl. | A very many | + | 242. | " | 2575 | 35.1 | r. cl. | AII " | + | | | | | | | + | 243. | " | 2800 | 35.0 | r. cl. | AII " | + | 244. | " | 2900 | 35.3 | r. cl. | AII " | + | 245. | " | 2775 | 34.9 | r. cl. | AII " | + | 246. | " | 2050 | 35.1 | gl. oz. | B numerous | + | 247. | " | 2530 | 35.2 | r. cl. | C many | + | | | | | | | + | 248. | " | 2900 | 35.1 | r. cl. | C " | + | 249. | " | 3000 | 35.2 | r. cl. | B numerous | + | 250. | " | 3050 | 35.0 | r. cl. | B " | + | 251. | " | 2950 | 35.1 | r. cl. | B " | + | 252. | " | 2740 | 35.3 | r. cl. | B " | + | | | | | | | + | 253. | " | 3125 | 35.1 | r. cl. | B " | + | 254. | " | 3025 | 35.0 | r. cl. | C many | + | 255. | " | 2850 | 35.0 | r. cl. | C " | + | 256. | " | 2950 | 35.2 | r. cl. | B numerous | + | 257. | " | 2875 | 34.9 | r. cl. | C many | + | | | | | | | + | 258. | " | 2775 | 35.2 | r. cl. | C " | + | 259. | Tr. Pac. | 2225 | 34.9 | r. cl. | C " | + | 261. | " | 2050 | 35.2 | volc. m. | C many | + | 262. | " | 2875 | 35.2 | r. cl. | C " | + | 263. | " | 2650 | 35.1 | r. cl. | B numerous | + | | | | | | | + | 264. | " | 3000 | 35.2 | r. cl. | C many | + | 265. | " | 2900 | 35.0 | r. cl. | A very many | + | 266. | " | 2750 | 35.1 | rad. oz. | A " | + | 267. | " | 2700 | 35.0 | rad. oz. | A " | + | 268. | " | 2900 | 34.8 | rad. oz. | A " | + | | | | | | | + | 269. | " | 2550 | 35.2 | rad. oz. | A " | + | 270. | " | 2925 | 34.6 | gl. oz. | A " | + | 271. | " | 2425 | 35.0 | gl. oz. | A " | + | 272. | " | 2600 | 35.1 | rad. oz. | A " | + | 273. | " | 2350 | 34.5 | rad. oz. | A " | + | | | | | | | + | 274. | " | 2750 | 35.1 | rad. oz. | A " | + | 275. | " | 2610 | 35.0 | r. cl. | B numerous | + | 276. | " | 2350 | 35.1 | r. cl. | C many | + | 280. | " | 1940 | 35.3 | gl. oz. | D few | + | 281. | " | 2385 | 34.9 | r. cl. | C many | + | | | | | | | + | 282. | S. Pac. | 2450 | 35.1 | r. cl. | C " | + | 283. | " | 2075 | 35.4 | gl. oz. | D few | + | 284. | " | 1985 | 35.1 | gl. oz. | C many | + | 285. | " | 2375 | 35.0 | r. cl. | D few | + | 286. | " | 2335 | 34.8 | r. cl. | D " | + | | | | | | | + | 287. | " | 2400 | 34.7 | r. cl. | D " | + | 288. | " | 2600 | 34.8 | r. cl. | B numerous | + | 289. | " | 2550 | 34.8 | r. cl. | B " | + | 290. | " | 2300 | 34.9 | r. cl. | C many | + | 291. | " | 2250 | 34.6 | r. cl. | C " | + | | | | | | | + | 292. | " | 1600 | 35.2 | gl. oz. | C " | + | 293. | " | 2025 | 34.4 | gl. oz. | C " | + | 294. | " | 2270 | 34.6 | r. cl. | D few | + | 295. | " | 1500 | 35.3 | gl. oz. | C many | + | 296. | " | 1825 | 35.3 | gl. oz. | D few | + | | | | | | | + | 297. | " | 1775 | 35.5 | gl. oz. | D " | + | 298. | " | 2225 | 35.6 | bl. m. | C many | + | 299. | " | 2160 | 35.2 | bl. m. | C " | + | 300. | " | 1375 | 35.5 | gl. oz. | B numerous | + | 302. | " | 1450 | 35.6 | gl. oz. | B " | + | | | | | | | + | 303. | " | 1325 | 36.0 | bl. m. | D few | + | 304. | " | 45 | ... | gr. m. | E very few | + | 318. | S. Atl. | 2040 | 33.7 | bl. m. | C few | + | 319. | " | 2425 | 32.7 | bl. m. | C " | + | 323. | " | 1900 | 33.1 | bl. m. | C " | + | | | | | | | + | 324. | " | 2800 | 32.6 | bl. m. | B numerous | + | 325. | " | 2650 | 32.7 | bl. m. | B " | + | 326. | " | 2775 | 32.7 | bl. m. | C many | + | 327. | " | 2900 | 32.8 | bl. m. | C " | + | 328. | " | 2900 | 32.9 | bl. m. | B numerous | + | | | | | | | + | 329. | " | 2675 | 32.3 | r. cl. | C many | + | 330. | " | 2440 | 32.7 | r. cl. | C " | + | 331. | " | 1715 | 35.4 | gl. oz. | B numerous | + | 332. | " | 2200 | 34.0 | gl. oz. | B " | + | 333. | " | 2025 | 35.3 | gl. oz. | B " | + | | | | | | | + | 334. | " | 1915 | 35.8 | gl. oz. | C many | + | 335. | " | 1425 | 37.0 | pt. oz. | D few | + | 338. | Tr. Atl. | 1990 | 36.3 | gl. oz. | D few | + | 340. | " | 1500 | 37.6 | pt. oz. | E very few | + | 341. | " | 1475 | 38.2 | pt. oz. | E " | + | | | | | | | + | 342. | " | 1445 | 37.5 | pt. oz. | D few | + | 343. | " | 425 | 40.3 | volc. s. | E very few | + | 344. | " | 420 | ... | volc. s. | E " | + | 345. | " | 2010 | 36.8 | gl. oz. | D few | + | 346. | " | 2350 | 34.0 | gl. oz. | C many | + | | | | | | | + | 347. | " | 2250 | 36.2 | gl. oz. | B numerous | + | 348. | " | (2450) | ... | (Pelag.) | B " | + | 349. | " | ... | ... | (Pelag.) | B " | + | 350. | " | ... | ... | (Pelag.) | B " | + | 351. | " | ... | ... | (Pelag.) | B " | + | | | | | | | + | 352. | " | ... | ... | (Pelag.) | B " | + | 353. | N. Atl. | 2965 | 37.6 | r. cl. | C many | + | 354. | " | 1675 | 37.8 | gl. oz. | D few | + +----------+-----------+--------+------------+-----------+--------------+ + + +----------+--------+-----------------------+---------------------------+ + | | | | | + |Challenger| Date. |Latitude and Longitude.| Nearest Land. | + | Station. | | | | + +----------+--------+-----------------------+---------------------------+ + | | 1873. | | | + | 1. |Feb. 15|27d 24' N., 16d 55' W.|S. of Tenerife. | + | 2. | " 17|25d 52' N., 19d 22' W.|S.W. of the Canary Islands.| + | 5. | " 21|24d 20' N., 24d 28' W.|S.W. of the Canary Islands.| + | 9. | " 26|23d 23' N., 35d 11' W.| (Ocean). | + | 24. |Mar. 25|18d 38' N., 65d 5' W.|Culebra (Antilles). | + | | | | | + | 32. |April 3|31d 49' N., 64d 55' W.|Bermuda. | + | 45. |May 3|38d 34' N., 72d 10' W.|S. of New York. | + | 50. | " 21|42d 8' N., 63d 39' W.|S. of Halifax. | + | 64. |June 20|35d 35' N., 50d 27' W.| (Ocean). | + | 76. |July 3|38d 11' N., 27d 9' W.|Azores. | + | | | | | + | 98. |Aug. 14| 9d 21' N., 18d 28' W.|W. of Sierra Leone. | + | 106. | " 25| 1d 47' N., 24d 26' W.| (Ocean). | + | 108. | " 27| 1d 10' N., 28d 23' W.| (Ocean). | + | 111. | " 31| 1d 45' S., 30d 58' W.| (Ocean). | + | 120. |Sept. 9| 8d 37' S., 34d 28' W.|Pernambuco. | + | | | | | + | 132. |Oct. 10|35d 25' S., 23d 40' W.|Tristan da Cunha. | + | 134. | " 14|36d 12' S., 12d 16' W.|Tristan da Cunha. | + | 137. | " 23|35d 59' S., 1d 34' E.| (Ocean). | + | 138. | " 25|36d 22' S., 8d 12' E.| (Ocean). | + | 143. |Dec. 19|36d 48' S., 19d 24' E.|Cape of Good Hope. | + | | | | | + | 144. | " 24|45d 57' S., 34d 39' E.| (Ocean). | + | 145. | " 27|46d 43' S., 38d 4' E.|Prince Edward Island. | + | 146. | " 29|46d 46' S., 45d 31' E.| (Ocean). | + | 147. | " 30|46d 16' S., 48d 27' E.|W. of the Crozet Islands. | + | | 1874. | | | + | 148. |Jan. 3|46d 47' S., 51d 37' E.|E. of the Crozet Islands. | + | | | | | + | 149H. | " 29|48d 45' S., 69d 14' E.|Kerguelen Island. | + | 150. |Feb. 2|52d 4' S., 71d 22' E.|N. of Heard Island. | + | 151. | " 7|52d 59' S., 73d 33' E.|Heard Island. | + | 152. | " 11|60d 52' S., 80d 20' E.|(Ocean). | + | 153. | " 14|65d 42' S., 79d 49' E.|Antarctic Ice. | + | | | | | + | 154. | " 19|64d 37' S., 85d 49' E.|Antarctic Ice. | + | 155. | " 23|64d 18' S., 94d 47' E.|Antarctic Ice. | + | 156. | " 26|62d 26' S., 95d 44' E.| (Ocean). | + | 157. |Mar. 3|53d 55' S., 108d 35' E.| (Ocean). | + | 158. | " 7|50d 1' S., 123d 4' E.| (Ocean). | + | | | | | + | 159. | " 10|47d 25' S., 130d 22' E.| (Ocean). | + | 160. | " 13|42d 42' S., 134d 10' E.| (Ocean). | + | 162. |April 2|39d 10' S., 146d 37' E.|Bass Strait. | + | 163. | " 4|36d 57' S., 150d 34' E.|Port Jackson. | + | 164A. |June 13|34d 9' S., 151d 55' E.|W. of Sydney. | + | | | | | + | 165. | " 17|34d 50' S., 155d 28' E.| (Ocean). | + | 166. | " 23|38d 50' S., 169d 20' E.|W. of New Zealand. | + | 169. |July 10|37d 34' S., 179d 22' E.|E. of New Zealand. | + | 175. |Aug. 12|19d 2' S., 177d 10' E.|Fiji Islands. | + | 181. | " 25|13d 50' S., 151d 49' E.|Louisiades. | + | | | | | + | 193. |Sept. 28| 5d 24' S., 130d 37' E.|Banda Sea. | + | 195. |Oct. 3| 4d 21' S., 129d 7' E.|Banda Sea. | + | 197. | " 14| 0d 41' N., 126d 37' E.|E. of Celebes. | + | 198. | " 20| 2d 55' N., 124d 58' E.|N. of Celebes. | + | 200. | " 23| 6d 47' N., 122d 28' E.|W. of Mindanao. | + | | | | | + | 201. | " 26| 7d 3' N., 121d 48' E.|W. of Mindanao. | + | 202. | " 27| 8d 32' N., 121d 55' E.|W. of Mindanao. | + | 205. |Nov. 13|16d 42' N., 119d 22' E.|W. of Luzon. | + | | 1875. | | | + | 206. |Jan. 8|17d 54' N., 117d 14' E.|W. of Luzon. | + | 211. | " 28| 8d 0' N., 121d 42' E.|W. of Mindanao. | + | | | | | + | 213. |Feb. 8| 5d 47' N., 124d 1' E.|S. of Mindanao. | + | 214. | " 10| 4d 33' N., 127d 6' E.|N. of Gilolo. | + | 215. | " 12| 4d 19' N., 130d 15' E.|N. of Gilolo. | + | 216A. | " 16| 2d 56' N., 134d 11' E.|S. of Pelew Islands. | + | 217. | " 22| 0d 39' S., 138d 55' E.|N. of New Guinea. | + | | | | | + | 218. |Mar. 1| 2d 33' S., 144d 4' E.|N. of New Guinea. | + | 220. | " 11| 0d 42' S., 147d 0' E.|N. of New Guinea. | + | 221. | " 13| 0d 40' N., 148d 41' E.| (Ocean). | + | 222. | " 16| 2d 15' N., 146d 16' E.| (Ocean). | + | 223. | " 19| 5d 31' N., 145d 13' E.|Carolines. | + | | | | | + | 224. | " 21| 7d 45' N., 144d 20' E.|Carolines. | + | 225. | " 23|11d 24' N., 143d 16' E.|Ocean } | + | 226. | " 25|14d 44' N., 142d 13' E.|Ocean } North-West Pacific,| + | 230. |April 5|26d 29' N., 137d 57' E.|Ocean } between Carolines | + | 231. | " 9|31d 8' N., 137d 8' E.|Ocean } and Japan. | + | | | | } | + | 232. |May 12|35d 11' N., 139d 28' E.|Ocean } | + | 234. |June 3|32d 31' N., 135d 39' E.|S. of Japan. | + | 235. | " 4|34d 7' N., 138d 0' E.|S. of Japan. | + | 236. | " 5|34d 58' N., 139d 29' E.|S. of Japan. | + | 237. | " 17|34d 37' N., 140d 32' E.|S. of Japan. | + | | | | | + | 238. | " 18|35d 18' N., 144d 8' E.|Ocean } | + | 239. | " 19|35d 18' N., 147d 9' E.|Ocean } | + | 240. | " 21|35d 20' N., 153d 39' E.|Ocean } | + | 241. | " 23|35d 41' N., 157d 42' E.|Ocean } | + | 242. | " 24|35d 29' N., 161d 52' E.|Ocean } | + | | | | } | + | 243. | " 26|35d 24' N., 166d 35' E.|Ocean } North Pacific, | + | 244. | " 28|35d 22' N., 169d 53' E.|Ocean } between Japan and | + | 245. | " 30|36d 23' N., 174d 31' E.|Ocean } San Francisco | + | 246. |July 2|36d 10' N., 178d 0' E.|Ocean } (35d-38d N. lat., | + | 247. | " 3|35d 49' N., 179d 57' W.|Ocean } 144d-156d W. long.)| + | | | | } | + | 248. | " 5|37d 41' N., 177d 4' W.|Ocean } | + | 249. | " 7|37d 59' N., 171d 48' W.|Ocean } | + | 250. | " 9|37d 49' N., 166d 47' W.|Ocean } | + | 251. | " 10|37d 37' N., 163d 26' W.|Ocean } | + | 252. | " 12|37d 52' N., 160d 17' W.|Ocean } | + | | | | } | + | 253. | " 14|38d 9' N., 156d 25' W.|Ocean | + | 254. | " 17|35d 13' N., 154d 43' W.|Ocean } | + | 255. | " 19|32d 28' N., 154d 33' W.|Ocean } North Pacific | + | 256. | " 21|30d 22' N., 154d 56' W.|Ocean } (35d-23d N. lat., | + | 257. | " 23|27d 33' N., 154d 55' W.|Ocean }154d-156d W. long.).| + | | | | } | + | 258. | " 24|26d 11' N., 155d 12' W.|Ocean } | + | 259. | " 26|23d 3' N., 156d 6' W.|Ocean } | + | 261. |Aug. 12|20d 18' N., 157d 14' W.|Sandwich Islands. | + | 262. | " 20|19d 12' N., 154d 14' W.|Sandwich Islands. | + | 263. | " 21|17d 33' N., 153d 36' W.|Ocean } | + | | | | } | + | 264. | " 23|14d 19' N., 152d 37' W.|Ocean } | + | 265. | " 25|12d 42' N., 152d 1' W.|Ocean } | + | 266. | " 26|11d 7' N., 152d 3' W.|Ocean } Tropical Central | + | 267. | " 28| 9d 28' N., 150d 49' W.|Ocean } Pacific, between | + | 268. | " 30| 7d 35' N., 149d 49' W.|Ocean } Sandwich and | + | | | | } | + | 269. |Sept. 2| 5d 54' N., 147d 2' W.|Ocean } Paumotu | + | 270. | " 4| 2d 34' N., 149d 9' W.|Ocean } (17d N. lat. to | + | 271. | " 6| 0d 33' S., 151d 34' W.|Ocean } 11d S. lat.). | + | 272. | " 8| 3d 48' S., 152d 56' W.|Ocean } | + | 273. | " 9| 5d 11' S., 152d 56' W.|Ocean } | + | | | | } | + | 274. | " 11| 7d 25' S., 152d 15' W.|Ocean } | + | 275. | " 14|11d 20' S., 150d 30' W.|Ocean } | + | 276. | " 16|13d 28' S., 149d 30' W.|Paumotu. | + | 280. |Oct. 4|18d 40' S., 149d 52' W.|S. of Tahiti. | + | 281. | " 6|22d 21' S., 150d 17' W.|Tubuai Islands. | + | | | | | + | 282. | " 7|23d 46' S., 149d 59' W.|Tubuai Islands. | + | 283. | " 9|26d 9' S., 145d 17' W.|N. of Oparo Island. | + | 284. | " 11|28d 22' S., 141d 22' W.|S. of Oparo Island. | + | 285. | " 14|32d 36' S., 137d 43' W.|Ocean } | + | 286. | " 16|33d 29' S., 133d 22' W.|Ocean } | + | | | | | + | 287. | " 10|36d 32' S., 132d 52' W.|Ocean } | + | 288. | " 21|40d 3' S., 132d 58' W.|Ocean } | + | 289. | " 23|39d 41' S., 131d 23' W.|Ocean } | + | 290. | " 25|39d 16' S., 124d 7' W.|Ocean } Open South Pacific | + | 291. | " 27|39d 13' S., 118d 49' W.|Ocean } Ocean, between New | + | | | | } Zealand and | + | 292. | " 29|38d 43' S., 112d 31' W.|Ocean } Valparaiso. | + | 293. |Nov. 1|39d 4' S., 105d 5' W.|Ocean } | + | 294. | " 3|39d 22' S., 98d 46' W.|Ocean } | + | 295. | " 5|38d 7' S., 94d 4' W.|Ocean } | + | 296. | " 9|38d 6' S., 88d 2' W.|Ocean } | + | | | | } | + | 297. | " 11|37d 29' S., 83d 7' W.|Ocean } | + | 298. | " 17|34d 7' S., 73d 56' W.|W. of Valparaiso. | + | 299. |Dec. 14|33d 31' S., 74d 43' W.|W. of Valparaiso. | + | 300. | " 17|33d 42' S., 78d 18' W.|N. of Juan Fernandez. | + | 302. | " 28|42d 43' S., 82d 11' W.| (Ocean). | + | | | | | + | 303. | " 30|45d 31' S., 78d 9' W.|W. of Patagonia. | + | 304. | " 31|46d 53' S., 75d 12' W.|W. of Patagonia. | + | | 1876. | | | + | 318. |Feb. 11|42d 32' S., 56d 29' W.| (Ocean). | + | 319. | " 12|41d 54' S., 54d 48' W.| (Ocean). | + | 323. | " 28|35d 39' S., 50d 47' W.|W. of Buenos Ayres. | + | | | | } | + | 324. | " 29|36d 9' S., 48d 22' W.|Ocean } | + | 325. |Mar. 2|36d 44' S., 46d 16' W.|Ocean } | + | 326. | " 3|37d 3' S., 44d 17' W.|Ocean } Open South Atlantic| + | 327. | " 4|36d 48' S., 42d 45' W.|Ocean } Ocean, between | + | 328. | " 6|37d 38' S., 39d 36' W.|Ocean } Buenos Ayres and | + | | | | } | + | 329. | " 7|37d 31' S., 36d 7' W.|Ocean } Tristan da Cunha | + | 330. | " 8|37d 45' S., 33d 0' W.|Ocean } (35d-37d S. lat., | + | 331. | " 9|37d 47' S., 30d 20' W.|Ocean } 21d-48d W. long.). | + | 332. | " 10|37d 29' S., 27d 31' W.|Ocean } | + | 333. | " 13|35d 36' S., 21d 12' W.|Ocean } | + | | | | | + | 334. | " 14|35d 45' S., 18d 31' W.|W. of Tristan da Cunha. | + | 335. | " 16|32d 24' S., 13d 5' W.|N. of Tristan da Cunha. | + | 338. | " 21|21d 15' S., 14d 2' W.|(Ocean). | + | 340. | " 24|14d 33' S., 13d 42' W.|Ocean } | + | 341. | " 25|12d 16' S., 13d 44' W.|Ocean } W. of St. Helena. | + | | | | | + | 342. | " 26| 9d 43' S., 13d 51' W.|Ocean } | + | 343. | " 27| 8d 3' S., 14d 27' W.|Ascension Island. | + | 344. |April 3| 7d 54' S., 14d 28' W.|Ascension Island. | + | 345. | " 4| 5d 45' S., 14d 25' W.|Ocean } | + | 346. | " 6| 2d 42' S., 14d 41' W.|Ocean } Tropical Atlantic, | + | | | | } between Ascension | + | 347. | " 7| 0d 15' S., 14d 25' W.|Ocean } and Sierra Leone. | + | 348. | " 9| 3d 10' N., 14d 51' W.|Ocean } | + | 349. | " 10| 5d 28' N., 14d 38' W.|Ocean } | + | 350. | " 11| 7d 33' N., 15d 16' W.|W. of Sierra Leone. | + | 351. | " 12| 9d 9' N., 16d 41' W.|W. of Sierra Leone. | + | | | | | + | 352. | " 13|10d 55' N., 17d 46' W.|W. of Sierra Leone. | + | 353. |May 3|26d 21' N., 33d 37' W.|W. of Canary Islands. | + | 354. | " 6|32d 41' N., 36d 6' W.|S. of Azores. | + +----------+--------+-----------------------+---------------------------+ + + + + +{clxiv}CHAPTER X.--GEOGRAPHICAL DISTRIBUTION. + +(ss 241-250.) + +241. _Historical Distribution._--Radiolaria are found fossil in all the +more important groups of the sedimentary rocks of the earth's crust. Whilst +a few years ago their well-preserved siliceous skeletons were only known in +considerable quantity from Cainozoic marls (s 242), very many SPUMELLARIA +and NASSELLARIA have recently been found in Mesozoic and a few in +Palaeozoic strata. By the aid of improved modern methods of investigation +(especially by the preparation of thin sections of very hard rocks) it has +been shown that many hard siliceous minerals, especially cryptocrystalline +quartz, contain numerous well-preserved Radiolaria, and sometimes are +mainly composed of closely compacted masses of such siliceous shells; of +this kind are many quartzites of the Jura (s 243). These Jurassic quartzes +(Switzerland), as well as the Tertiary marls (Barbados) and clays (Nicobar +Islands), are to be regarded as "fossil Radiolarian ooze" (s 237). Dense +masses of compressed SPUMELLARIA and NASSELLARIA form the principal part of +these rocks. Isolated or in smaller quantities, fossil Polycystina, +belonging to different families of SPUMELLARIA and NASSELLARIA, also occur +in in other rocks, and even in some of Palaeozoic origin. Since specimens +have also been recently found both in Silurian and Cambrian strata, it may +be stated that as regards their historical distribution, Radiolaria occur +in all fossiliferous sedimentary deposits, from the oldest to those of the +present time. + + +242. _Cainozoic Radiolaria._--The great majority of fossil Radiolaria which +have hitherto been described, belong to the Cainozoic or Tertiary period, +and in fact, to its middle portion, the Miocene period. At this period the +richest and most important of all the Radiolarian formations were +deposited, such as the pure "Polycystine marl" of Barbados (see note A), +also that of Grotte in Sicily (see note B), and the clay of the Nicobar +Islands (see note C). Besides the above-mentioned deposits, which may be +designated "pure" fossil Radiolarian ooze, many deposits containing these +organisms have recently been discovered in widely separated parts of the +earth, partly of the nature of tripoli or marl, partly resembling clay. +Among these may be mentioned in the first place many coasts and islands of +the Mediterranean, both on the south coast of Europe (Sicily, Calabria, +Greece), and the north coast of Africa (from Oran to Tripoli). The +extensive layers of tripoli which are found in these Mediterranean Tertiary +mountains belong to the upper Miocene (Tortona stage), and consist partly +of marl rich in calcareous matter, and resembling chalk, partly passing +over into plastic clay or "Kieselguhr" (s 246). The quantity of Radiolaria +contained varies, and is more conspicuous the fewer the calcareous shells +of Foraminifera present. Similar Tertiary Polycystine formations occur in +some parts of America (see note D); probably they have a very wide +distribution. In their general morphological characters, the Tertiary +SPUMELLARIA and NASSELLARIA {clxv}are related to those forms which are +found in the recent Radiolarian ooze of the depths of the Pacific, +especially to the species which are characteristic of the Challenger +Stations 225, 226, 265 and 268. Many living genera and families (_e.g._, +most #Larcoidea# and #Stephoidea#) have not yet been found in the Tertiary +formations. + + A. The famous Polycystine marl of Barbados in the Antilles, which Robert + Schomburgk discovered forty years ago, belongs to the Miocene formation, + and is the richest and best known of all the important Radiolarian + deposits (see L. N. 16, pp. 5-8). After Ehrenberg had published in + December 1846 the first preliminary communication regarding its + composition out of masses of well-preserved Polycystina, he was able in + the following year to describe no less than 282 species from it; he + distributed these in 44 genera and 7 families (L. N. 4, 1847, p. 54). In + the year 1854 Ehrenberg published figures of 33 species in his + Mikrogeologie (L. N. 6, Taf. xxxvi.); but it was only in 1873 that he + published descriptions of 265 species (Monatsber. d. k. preuss. Akad. d. + Wiss. Berlin, Jan. 30, pp. 213-263). Finally there followed in 1875 his + Fortsetzung der Mikrogeologischen Studien, mit specieller Ruecksicht auf + den Polycystinen-Mergel von Barbados (L. N. 25). On the thirty plates + which accompany this the last work of Ehrenberg, 282 species are figured + and named, of which 54 are SPUMELLARIA (13 #Sphaeroidea#, 8 #Prunoidea#, + 33 #Discoidea#), and 228 NASSELLARIA (2 #Stephoidea#, 38 #Spyroidea#, and + 188 #Cyrtoidea#). The fourth section of this memoir contains a survey of + the Polycystine formation of Barbados (pp. 106-115), and the fifth + section the special description of a large specimen of rock from Mount + Hillaby in Barbados (see also L. N. 28, p. 117, and L. N. 41, pp. + 476-478). The account given by Ehrenberg of the Polycystina of Barbados + is in many respects very incomplete, and very far from exhausting this + rich mine of remarkable forms. This may be readily seen from the + twenty-five plates of figures of Polycystins in the Barbados Chalk + Deposit published by Bury in 1862 (L. N. 17). The number of species here + figured (140 to 142) is about half of those given by Ehrenberg; and there + are among them numerous generic types, some of great interest, which were + entirely overlooked by the latter; _e.g._ _Saturnalis_ (#Sphaeroidea#), + _Cannartidium_ (#Prunoidea#), _Tympanidium_ (#Stephoidea#), + _Cinclopyramis_ (#Cyrtoidea#), &c. Finally, Ehrenberg always (until 1875) + ignored Bury's atlas, which had been published thirteen years ago and was + quite accessible to him. How different were the contents of the two works + may easily be seen from the following abstract. + +_Comparative View of the Species of Fossil Radiolaria from Barbados made +known by the figures of Bury in 1862 and of Ehrenberg in 1875._ + + +-------------------+--------------------+--------+-----------+-------+ + | Legion. | Order. | Bury. | Ehrenberg.| Total.| + +-------------------+--------------------+--------+-----------+-------+ + | I. Legion | { 1. Sphaeroidea | 16 | 13 | 29 | + | SPUMELLARIA | { 2. Prunoidea | 10 | 8 | 18 | + | (PERIPYLEA). | { 3. Discoidea | 37 | 33 | 70 | + | | | | | | + | II. Legion | { 4. Stephoidea | 5 | 2 | 7 | + | NASSELLARIA | { 5. Spyroidea | 13 | 38 | 51 | + | (MONOPYLEA). | { 6. Cyrtoidea | 60 | 188 | 248 | + +-------------------+--------------------+--------+-----------+-------+ + | Total, | 141 | 282 | 423 | + +----------------------------------------+--------+-----------+-------+ + + {clxvi}In 1882 Buetschli still further increased the number of known + Radiolaria from Barbados both by figures and descriptions (L. N. 40), and + gave in particular a very accurate morphological analysis of 12 new + NASSELLARIA (3 #Stephoidea#, 3 #Spyroidea#, and 6 #Cyrtoidea#; L. N. 40, + Taf. xxxii., xxxiii.). The number of the fossil species collected in the + Barbados marl is, however, greater than would appear from the + above-quoted communications. My respected friend, Dr. R. Teuscher, of + Jena, has, at my request, made a large number (about a thousand) of very + accurate drawings with the camera lucida of Polycystina from Barbados + (see p. 1760). From these it appears that the variations in the structure + of the shells, with respect to number, size, and form of the + lattice-pores, of the spines, &c., is much greater than would be supposed + from the figures of Ehrenberg and Bury. I have thus come to the + conviction that the number of species from Barbados (using the word + "species" in the sense understood by those authors) is not less than 400 + and probably more than 500. Descriptions of some particularly interesting + new species from this series have been included in the systematic account + of the Challenger Radiolaria. A complete critical investigation of the + Radiolaria of Barbados, and especially an accurate comparison of these + Cainozoic species with the Mesozoic forms from the Jura, on the one hand, + and with recent types on the other, must be left to the future for its + accomplishment (see s 246). + + B. The Cainozoic Polycystine tripoli or marl of the Mediterranean coast, + which is probably always of Miocene origin, forms very extensive mountain + ranges both in the south of Europe (Sicily, Calabria, Greece) and in the + north of Africa (from Oran to Tripoli) (s 246). Hitherto, however, only + one locality has been thoroughly investigated, namely, Grotte in the + province of Girgenti in Sicily (L. N. 35). In the accurate account which + was given of it by Stoehr in 1880, 118 species were described, + distributed in 40 genera (L. N. 35; pp. 72-84); of these 118 species 78 + are quite new, 25 are identical with previously known fossils, and 29 + identical with living forms. Among them are 73 SPUMELLARIA (28 + #Sphaeroidea#, 8 #Prunoidea#, and 37 #Discoidea#), but only 40 + NASSELLARIA (1 #Stephoidea#, 6 #Spyroidea#, and 33 #Cyrtoidea#), and 5 + PHAEODARIA (Dictyochida). The other parts of Sicily from which the same + upper Miocene tripoli has been investigated (belonging to the Tortona + stage) have proved less rich than Grotte. The best known of these places + is Caltanisetta, since upon three genera discovered here (_Haliomma_, + _Cornutella_, _Lithocampe_) the group Polycystina was founded by + Ehrenberg in 1838 (see L. N. 16, p. 3). Afterwards 31 species were + described from this locality, of which 23 were again found in Grotte. The + richest deposit on the Mediterranean coast, however, appears to be at + Oran. A small specimen of the Kieselguhr found there, which was recently + sent to me by Professor Steinman, proved to be pure Radiolarian ooze, + very similar to that now found in the Central Pacific, and contained many + hitherto undescribed species; it is deserving of careful investigation + and comparison. + + C. Regarding the Tertiary Radiolarian clay of the Nicobar Islands, see s + 247 and L. N. 25, pp. 116-120. Its fauna is incompletely known; probably + it is of Miocene or Oligocene origin. + + D. Cainozoic tripoli, containing larger or smaller quantities of + Radiolaria, appears to be rather widely distributed in America. Ehrenberg + has described such from South America (polishing-slate from Morro di + Mijellones, on the coast between Chili and Bolivia), and from North + America (Richmond and Petersburg in Virginia, Piscataway in Maryland). + Similar deposits are also found in the Bermuda Islands (L. N. 4, 1855-56; + L. N. 6, Taf. 18; L. N. 16, pp. 3-9; L. N. 41, pp. 475-478, and L. N. 25, + pp. 2-6). + + +{clxvii}243. _Mesozoic Radiolaria._--From the Mesozoic or Secondary period +numerous well-preserved Radiolaria have recently been described. They +belong for the most part to the Jurassic formation (see notes A, B, C), +whilst the more recent Chalk (see note D) and the older Trias (see note E) +have hitherto yielded but few species. All the main divisions of the Jura, +both the upper (Malm) and the middle (Dogger), and especially the lower +(Lias) appear in certain localities to be very rich in well-preserved +shells of fossil Polycystina. Most of these are aggregated together in +coprolites and quartzites (jasper, chert, flint, &c., s 248). The majority +are #Cyrtoidea#, the minority #Sphaeroidea# and #Discoidea# in almost equal +proportions; a few #Beloidea# (_Sphaerozoum_) and #Phaeocystina# +(Dictyocha) are also found among them. The general morphological character +of these Jurassic Radiolaria is very different from that of the nearly +related Tertiary and living forms. In general, their siliceous shells are +firmer and more massive, usually also somewhat larger, but of simpler +structure. The manifold delicate appendages (spines, bristles, feet, wings, +&c.) which are so richly developed in the living SPUMELLARIA and +NASSELLARIA, and are also well shown in the Tertiary species, are entirely +wanting in the majority of the Jurassic Polycystina. The #Sphaeroidea# and +#Prunoidea# are all simple spherical or ellipsoidal lattice-shells +(Monosphaerida); concentric lattice-shells (Polysphaerida) are entirely +wanting. The #Cyrtoidea# are, for the most part, devoid of radial processes +or basal feet (Eradiata); triradiate and multiradiate forms, such as are +found abundantly in the recent and Tertiary formations, are very rare. The +large number of many-jointed forms (Stichocyrtida) and of #Cyrtoidea# with +latticed basal opening is very striking. + + A. The most important work on the Jurassic Radiolaria, regarding which + but little was known prior to the year 1885, is the valuable and in some + respects very interesting Beitraege zur Kenntniss der fossilen + Radiolarien aus Gesteinen des Jura, by Dr. Ruest of Freiburg i. B. (1885, + Palaeontographica, Bd. xxxi. 51 pp. with 12 plates). Unfortunately this + important work was issued only when about half of the present Report was + printed off, so that it was no longer possible to include the 234 species + there described in its systematic part. I have therefore elsewhere given + a list of the Jurassic Radiolaria, and at present only make the following + remarks:--Of the 234 species described, the larger half (130) belong to + the NASSELLARIA (#Cyrtoidea#), the smaller half (102) to the SPUMELLARIA + (38 #Sphaeroidea#, 14 #Prunoidea#, and 50 #Discoidea#). In addition, + there are 2 PHAEODARIA depicted, and several spicules which are probably + to be referred to the #Beloidea#. Among the 130 #Cyrtoidea# (of which 2 + are described as #Botryodea#), there are 24 Monocyrtida, 14 Dicyrtida, 22 + Tricyrtida, and 70 Stichocyrtida. Just as striking as the predominant + number of the last is the fact that there are only very few triradiate + (9) and multiradiate (4) species found among these 130 #Cyrtoidea#, as + also the large number of species with latticed basal opening; + #Stephoidea# appear to be entirely wanting. The rich material of jasper, + chert, flint, and coprolites in which Dr. Ruest found these Radiolaria, + is derived for the most part from the Jurassic rocks of Germany (Hanover, + South Bavaria), Tyrol, and Switzerland (compare s 248). + + {clxviii}B. Jurassic Radiolaria from Italy, also found in jasper, which + are closely related to the forms from Germany and Switzerland described + by Dr. Ruest, were made known so long ago as 1880 by Dante Pantanelli in + his treatise I Diaspri della Toscana e i loro Fossili (Rome, 1880, 33 pp. + 60 figs.). Pantanelli believes, however, that this jasper is for the most + part of Eocene origin; but from his description, and especially from the + morphological character of the forms which he figures, it appears very + probable "that these Tuscan jaspers from Galestro, like those of the + Swiss conglomerates, are found in a secondary locality and belong to the + Jurassic period" (Ruest, L. N. 51, p. 3). Unfortunately the figures of + Pantanelli are so small and incomplete that a reliable determination of + the species is hardly possible; for example, the lattice-work is only + given in ten of the sixty figures. Among the 32 recorded species 15 are + SPUMELLARIA (6 #Sphaeroidea# and 9 #Discoidea#) and 17 NASSELLARIA (4 + #Stephoidea# and 13 #Cyrtoidea#); many of which seem to be identical with + the forms more accurately described by Dr. Ruest (compare p. 1762). + + C. From the Lias of the Alps and more particularly "from the lower + Liassic beds of the Schafberg near Salzburg," Dr. Emil von Dunikowski in + 1882 described 18 species of fossil Radiolaria (L. N. 44, pp. 22-34, Taf. + iv.-vi.); most of these are #Sphaeroidea# and #Discoidea# and appear to + have been more or less altered by petrological changes; their spongy + structure is probably secondary. + + D. Cretaceous Radiolaria have been hitherto described only in very small + numbers; quite recently Dr. Ruest has found a larger number chiefly in + flints from the English chalk, but they have not yet been published. In + 1876 Zittel described 6 very well-preserved species from the upper chalk + of North Germany (L. N. 29, pp. 76-96, Taf. ii.); among them were 1 + #Sphaeroidea#, 1 #Discoidea#, 1 Dictyocha, and 3 #Cyrtoidea#. + + E. Triassic Radiolaria have recently been discovered by Dr. Ruest in + chert, but have not yet been described. + + +244. _Palaeozoic Radiolaria._--The number of Radiolaria which are known +from the Palaeozoic or Primary formations is much less than from either the +Mesozoic or Cainozoic periods. Here, however, the investigations of recent +times have yielded important information; a few species, at all events, of +Polycystina (mostly #Sphaeroidea#) are now known from various Palaeozoic +formations, and not only from the Permian ("Zechstein") and the +Coal-measures, but also from the older Devonian and Silurian systems. Even +in the still older Cambrian rocks a few fossil Radiolaria have been found. +All these Palaeozoic Radiolaria are Polycystina of very simple form and +primitive structure, mostly simple SPUMELLARIA (latticed spheres, +ellipsoids, lenses, &c.), but partly also simple NASSELLARIA. + + The important discoveries which have recently been made by Dr. Ruest + regarding the occurrence of Radiolaria in all the Palaeozoic formations + have not yet been published. From conversations with this estimable + palaeontologist I have learned, however, that he has pursued his fruitful + investigation of the Mesozoic quartzites (s 243), and has met with no + less success in the case of similar Palaeozoic structures. Although the + number of species hitherto discovered is relatively small, the important + conclusion appears to be warranted that they extend as far as the + Silurian and Cambrian systems. All these very ancient SPUMELLARIA + (#Sphaeroidea#) and NASSELLARIA (#Cyrtoidea#) {clxix}exhibit very + primitive structural relations. The occurrence of fossil Polycystina in + the Carboniferous formation of England has been incidentally mentioned by + W. J. Sollas:--"In the carboniferous beds of North Wales pseudomorphs of + Radiolaria in calcite occur, along with minute quartz crystals" (Ann. and + Mag. Nat. Hist., 1880, ser. 5, vol. vi. p. 439); and in the siliceous + slate-beds of Saxony Rothpletz has shown the existence of a few + #Sphaeroidea# (Zeitschr. d. Deutsch. Geol. Gesellsch., 1800, p. 447). + + +245. _Abundance of Radiolaria in the Various Rocks._--The relative quantity +of well-preserved or at all events recognisable Radiolaria in the different +rocks is very variable. In this respect three different degrees may be +distinguished, which may be called shortly "pure, mixed, and poor" +Radiolarian formations. The _pure_ Radiolarian rocks consist for the +greater part (usually much more than half, sometimes even more than +three-quarters) of closely compacted often calcined masses of siliceous +Polycystine shells. To this category belong the pure Miocene Polycystine +marls of Barbados (s 246), the Tertiary Polycystine clay of the Nicobar +Islands (s 247), and the Polycystine quartz of the Jura (s 248). All these +pure Radiolarian rocks may be regarded as fossil Radiolarian ooze (s 237), +and are certainly of deep-sea origin, having probably been deposited at +depths greater than 2000 fathoms. Their palaeontological character also is +in favour of this view, for the abyssal Osculosa (s 235) are more abundant +and richer in species than the pelagic Porulosa (s 233). The elevation of +this deep-sea layer above the surface of the sea appears to have taken +place but seldom; it has only been observed on a large scale at Barbados +and in the Nicobar Islands. The _mixed_ Radiolarian rocks are much more +common; they were probably deposited at much less depths, or perhaps are +not true deep-sea formations at all. The siliceous shells of Polycystina +always constitute less than half (sometimes less than one-tenth) of their +mass, and are less prominent than other siliceous remains (Diatoms), or +calcareous remains (Foraminifera), or in some cases than the mineral +constituents (pumice, &c.). To this group belong many of the +above-mentioned Tertiary marls and clays (especially the Mediterranean +Tripoli), also many flints, cherts, and other quartzites from Mesozoic +strata (especially from the Jura), and probably also some palaeozoic +quartzites. The marine ooze from which they have originated may have been +deposited at very various, even at slight, depths of the ocean. Formations +_poor_ in Radiolaria, which contain only a few species of SPUMELLARIA and +NASSELLARIA mingled with other fossil remains and mineral particles, occur +in all formations and are probably very widely distributed. Further careful +examination of thin sections (especially of coprolites) will yield here a +rich harvest of new forms. Both the mixed and the pure Radiolarian +formations may be divided according to their petrographic characters into +three groups, which, however, are connected by intermediate varieties--(1) +soft, chalky marl (s 246), (2) plastic clay (s 247), and (3) hard, flinty +quartz (s 248). + + +{clxx}246. _Radiolarian Marl._--Those soft, friable rocks, which contain a +large quantity of calcareous matter, but consist for the most part of the +shells of SPUMELLARIA and NASSELLARIA, are called Radiolarian or +Polycystine marl, often more correctly Polycystine tripoli; the best known +example of them is the chalky marl of Barbados in the Antilles (s 242). The +Tertiary mountain system of this island, which in Mount Hillaby rises to a +height of 1147 feet and includes about 15,800 acres, consists almost +exclusively of these remarkable masses of rock. Most of it appears as a +soft, earthy, often chalky marl, with a considerable but variable amount of +calcareous matter. Those specimens, the greater half of which is composed +of well-preserved siliceous shells of Polycystina, and which contain little +lime, approach the tripoli and "Kieselguhr." Those specimens, however, +which contain the largest amount of calcareous matter resemble common +writing chalk in consistency, and consist for the most part of shells of +Foraminifera and their fragments; of these there are only few species but +large numbers of individuals, generally in small fragments with a fine +calcareous powder between them. They may be regarded as fossil Globigerina +ooze (s 238). In a third group of specimens from Barbados the quantity of +fragments of pumice and other volcanic matters predominates; the amount of +clay is also very considerable; these deposits pass over partly into actual +clay partly into volcanic tuff. A fourth group exhibits relations to a +coarser often ferruginous material, and although the shells of Polycystina +are less abundant in it, still it may be shown to be composed largely of +fragments and metamorphosed remains of them. The colour of this deposit, +which in some places passes over into sandstone, in others into clay, is +usually rather dark, grey, brown, sometimes red and occasionally black +(bituminous). The Radiolarian marls of the first two groups, which +sometimes approach the white chalk, sometimes the Kieselguhr, are grey, or +even pure white (see note A). The same constitution is exhibited by the +yellowish or white, very light and friable Polycystine marls of Sicily, +which in Caltanisetta approach the chalk, and in Grotte the Kieselguhr. In +Greece (Aegina, Zante, &c.), on the other hand, they pass over into plastic +clay, and the same occurs in the Baden marl of the Vienna basin. In North +Africa, however, on the Mediterranean shores of which the Radiolarian marl +seems to be very widely distributed (from Tripoli to Oran), it sometimes +becomes changed into actual firm polishing slate, sometimes into +pulverulent Kieselguhr or tripoli (Terra tripolitana, see note B). Most of +these Radiolarian marls appear to date from the middle Tertiary (Miocene) +period, and to be deep-sea formations. + + A. The Polycystine marl of Barbados appears at different parts of the + island to present greater variations in its petrographical and + zoographical composition than would appear from Ehrenberg's description + (1875, L. N. 25, pp. 106-116). Through the kindness of one of my former + students, Dr. Dorner, to whom I take this opportunity of expressing my + thanks for the favour, I received a large number of specimens of Barbados + rock, taken from various parts of the island, and they exhibit very great + variations in their external appearance, their chemical composition, and + the {clxxi}Radiolaria which they contain. The white specimens resembling + Kieselguhr contained approximately 60 to 70 per cent. by volume of + Radiolarian shells, the yellowish marl 40 to 50 per cent., and the brown + and black (bituminous) marl 10 to 20 per cent. or less. Two analyses of + the first, which my friend Dr. W. Weber was good enough to carry out, + yielded different results from those which are given by Ehrenberg on the + basis of Rammelsberg's analyses (L. N. 25, p. 116). The results of both + are here given for comparison. + + --------------------------------+--------------------------+------------- + Ehrenberg-Rammelsberg | Weber I. | Weber II. + (Fragment from Hillaby). | (Chalk-like Fragment). |(Tripoli-like + | | Fragment). + --------------------------------+--------------------------+------------- + Silicate of alumina, 59.47 |Silica, 52.2 | 71.3 + Alumina and oxide of iron, 1.95 |Alumina (with traces | + Calcium carbonate, 34.31 | of oxide of iron), 12.3 | 11.2 + Water, 3.67 |Lime and magnesia, 31.9 | 14.8 + |Carbon dioxide, 3.2 | 2.7 + ______ | _____ | _____ + Total, 99.40 | Total, 99.6 | 100.0 + --------------------------------+--------------------------+------------- + + For further comparison I here add the three different analyses of Miocene + Tripoli-marls from Sicily, given by Stoehr on the authority of Fremy, + Schwager, and Mottura (Tagebl. d. fuenfzigsten Versamml. Deutsch. Naturf. + u. Aertzte in Muenchen, 1877, p. 163). + + --------------------------+-------------+--------------+------------- + Composition. |Tripoli from | Tripoli from | Tripoli from + | Licata | Grotte | Caltanisetta + | (Fremy). | (Schwager). | (Mottura). + --------------------------+-------------+--------------+------------- + Silica, | 30.98 | 58.58 | 68.6 + Alumina, | 17.54 | 11.51 | } + Oxide of iron, | 0.33 | 1.84 | } 3.6 + | | | + Lime, } | 38.09 | { 8.49 | } + Magnesia, } | | { 0.41 | } 12.1 + | | | + Water and organic matter,}| | { 11.26 | } + Carbonic acid, }| 13.06 | { 7.12 | } 15.2 + +-------------+--------------+------------ + | 100.00 | 99.21 | 99.5 + --------------------------+-------------+--------------+------------- + + B. The Radiolarian marl of the Mediterranean appears, judging by the + accounts already published, to stretch along a considerable part of the + coast in the earlier and middle Tertiary formations; thus it occurs of + similar composition in widely separated localities, in Sicily, Calabria, + Zante, and Greece; in North Africa from Tripoli to Oran and probably much + farther. So long ago as 1854 Ehrenberg, in his Mikrogeologie (L. N. 6) + gave a series of important, even if incomplete, communications regarding + the "chalky white calcareous marl of Caltanisetta" (Taf. xxii.), the + "Platten marl of Zante" (Taf. xx.), the "plastic clay of Aegina" (Taf + xix.), and the "polishing slate of Oran" (Taf. xxi.). In 1880 Stoehr + showed in his fundamental description of the Tripoli from {clxxii}Grotte + in Sicily (L. N. 35) that its Radiolarian fauna is much richer than + Ehrenberg supposed. The same is the case in the Tripoli of Caltanisetta, + and also in the Baden marl of the Vienna basin. The richest deposit + appears to be the pure Kieselguhr-like Tripoli from Oran; a small + specimen, which was recently sent to me by Professor Steinmann of + Freiburg, i. B., contained many hitherto undescribed species, and was at + least as rich as the purest Barbados marl. + + +247. _Radiolarian Clays._--Among the Radiolarian or Polycystine clays we +include the firm, often plastic, formations, which contain a larger +proportion of Radiolaria than of other organic remains. The first of these +to be mentioned is the Cainozoic formation of the Nicobar Islands in +Further India, which rises to a height of 2000 feet above the level of the +sea, and consists for the most part of coloured masses of clay of varying +constitution; on Car Nicobar these are mostly grey or reddish, on the +Island of Camorta they are partly strongly ferruginous and red and yellow +(_e.g._ at Frederickshaven), partly white and light, like meerschaum +(_e.g._ at Mongkata). The latter varieties appear to pass over into pure +loose Polycystine marl like that of Barbados, the former into calcareous +sandstone. Although the Polycystine clays of the Nicobar Islands are as yet +only very incompletely known, it may be concluded with great probability +that they are true deep-sea formations and nearly allied to those recent +forms of red clay, which by their abundance in Radiolaria most nearly +approach the Radiolarian ooze, such for example as the red clay of the +North Pacific between Japan and the Sandwich Islands (Stations 241 to 245, +compare ss 229 and 239). With this view agrees also the greater or less +quantity of pumice dust and other volcanic products. Probably Radiolarian +clays like those of the Nicobar Islands occur also in other Tertiary rocks; +part of the Barbados marl passes by gradually increasing content of clay +into such; and in this case also the amount of included pumice is often +considerable. Many mixed Radiolarian marls of the Mediterranean (_e.g._, of +Greece and Oran) also appear to pass over at certain points into +Radiolarian clay. + + The Radiolarian clays of the Nicobar Islands are unfortunately very + incompletely known both as regards their geological nature and their + palaeontological composition. The communications of Rink (Die + Nikobaren-Inseln, eine geographische Skizze, Kopenhagen, 1847) and of + Ehrenberg (L. N. 6, p. 160 and L. N. 25, pp. 116 to 120) leave many + important questions unanswered. The latter has only figured twenty-three + species in his Mikrogeologie (L. N. 6, Taf. xxxvi.). In his tabular list + of names (L. N. 25, p. 120) he only incompletely records thirty-nine + species, although in 1850, immediately after the first examination of the + Nicobar clay, he had distinguished "more than a hundred species, partly + new, partly identical with those of Barbados" (L. N. 16, p. 8). I have + unfortunately been unable in spite of many efforts, to obtain for + investigation a specimen of Nicobar clay. The only microscopical + preparation (from Ehrenberg's collection), which I was able to examine, + contained several hitherto undescribed species. A thorough systematic + examination of these important Radiolarian clays is a pressing necessity, + especially as they seem to be markedly different from those of the + Mediterranean (from Aegina, Zante, &c.). + + +{clxxiii}248. _Radiolarian Quartzes._--Under the name Radiolarian or +Polycystine quartzes are included those hard, siliceous rocks, which +consist for the most part of the closely compacted shells of SPUMELLARIA +and NASSELLARIA. To these "cryptocrystalline quartzes," or better, +quartzites, belong more especially the pure Radiolarian formations of the +Jura, which have been described as flint, chert, jasper, as well as other +cryptocrystalline quartzites. Most of the rocks of this nature hitherto +examined are from Germany (Hanover, South Bavaria), Hungary, Tyrol, and +Switzerland; others are known from Italy (Tuscany). They occur both in the +upper and middle, but especially in the lower Jurassic formation (also in +the lower layers of the Alpine Lias). A small part of them has been +examined in their primary situation (the red jaspers of Allgaeu and Tyrol), +the greater part, however, only as loose rolled stones in secondary +situations (thus in Switzerland in the breccia of the Rigi, in the +conglomerate of the Uetli-Berg, and in many boulders of the Rhine, the +Limmat, the Reuss, and the Aar). The greatest abundance, however, of +Jurassic Radiolaria has been yielded by the silicified coprolites from the +Lias of Hanover. These "Radiolarian coprolites" are roundish or cylindrical +bodies, which may attain the size of a goose-egg; they probably originated +from Fish or Cephalopods, which had fed upon Crustacea, Pteropoda, and +similar pelagic organisms, whose stomachs were already full of Radiolarian +skeletons. Next to the coprolites the richest is the red jasper, whose +colour varies from bright to dark red; it constitutes a true "silicified +deep-sea Radiolarian ooze." The "_Aptychus_ beds" also of South Bavaria and +Tyrol are very rich, and have furnished about one-third of all the +Radiolaria known from the Jura; most of the species too are very well +preserved (compare s 243). + + Regarding the remarkable composition and manifold varieties of the + Jurassic Radiolarian quartz, the very full treatise of Dr. Ruest may be + consulted (L. N. 51). The very interesting Radiolarian coprolites, which + that author has discovered in the lower and middle Jura of Hanover, occur + in astonishing numbers in the iron mines at the village of Gross-Ilsede, + four and a half miles south of the town of Peine. They constitute from 2 + to 5 per cent. by weight of the Liassic iron ore; of this latter, in the + year 1883 alone, not less than two hundred and eighty million kilograms + were excavated. It is very probable that the careful microscopic + examination of thin sections of coprolites, as well as of flints, chert, + jasper, and other quartzites, would yield a rich harvest of fossil + Radiolaria in other formations also. In Italy Dante Pantanelli has + discovered interesting Polycystine jaspers in Tuscany (L. N. 36, 45); + these also appear to occur in the Jura (compare s 243, and L. N. 51, pp. + 3-10). + + +249. _Fossil Groups._--The preservation of Radiolaria in the fossil state +is, of course, primarily dependent on the composition of their skeleton. +Hence the ACANTHARIA, whose acanthin skeleton although firm is readily +soluble, are never found fossil. The same is true of the skeletons of the +PHAEODARIA, which consist of a silicate of carbon; here, however, a single +exception is found in the Dictyochida, a subfamily of the Cannorrhaphida, +the isolated parts of whose skeletons appear to consist of pure silica, and +{clxxiv}are often found fossil. Of the two other legions those families +which possess no skeleton are of course excluded; the Nassellida among the +NASSELLARIA, and the Thalassicollida and Collozoida among the SPUMELLARIA. +Thus of the 85 known families there remain scarcely 55 of which the +skeletons may be expected in the fossil state; and of these scarcely half +have been actually observed in this condition. Of the 20 orders of this +class enumerated in s 155, the following 9 may be, for palaeontological and +geological purposes, completely excluded:--(A) The 4 orders of ACANTHARIA +(1, #Actinelida#; 2, #Acanthonida#; 3, #Sphaerophracta#; 4, +#Prunophracta#); (B) 3 orders of PHAEODARIA (5, #Phaeosphaeria#; 6, +#Phaeogromia#; 7, #Phaeoconchia#); (C) 1 order of NASSELLARIA (8, +#Nassoidea#); (D) 1 order of SPUMELLARIA (9, #Colloidea#). From a +geological point of view the following 6 orders, although occasionally +found fossil, are of quite subordinate importance:--(A) Among the +SPUMELLARIA (10, #Beloidea#, and 11, #Larcoidea#); (B) among the +NASSELLARIA (12, #Plectoidea#; 13, #Stephoidea#; 14, #Botryodea#); (C) +among the PHAEODARIA (15, the #Phaeocystina#). On the other hand the +following 5 orders, which are the main constituents of Radiolarian rocks, +are of pre-eminent geological importance:--(A) Among the SPUMELLARIA (16, +#Sphaeroidea#; 17, #Prunoidea#; 18, #Discoidea#); (B) among the NASSELLARIA +(19, #Spyroidea#, and 20, #Cyrtoidea#). The numerical relation in which the +different families of these orders appear in the Radiolarian formations may +be seen on consulting s 157. + + +250. _Fossil and Recent Species._--The fact that there are many Radiolaria +living at the present day, whose shells are found fossil in Tertiary rocks, +is of great phylogenetic and geological significance. This appeared to be +the case even from the older observations upon the Polycystina of the +Barbados marl (see note A), but more recent and extensive observations both +upon these and upon the Miocene Radiolaria of Sicily, have shown that the +number of these "living fossil" forms is much greater than was previously +supposed (see note B). Among the Miocene Radiolaria numerous species, both +of SPUMELLARIA (especially #Sphaeroidea# and #Discoidea#) and of +NASSELLARIA (especially #Spyroidea# and #Cyrtoidea#) are not to be +distinguished from the corresponding still living forms (see notes C, D). +On the other hand, those genera, which are rich both in species and +individuals (recent as well as fossil), present continuous series of forms +which lead gradually and uninterruptedly from old Tertiary species to +others still living, which are specifically indistinguishable from them. +These interesting morphological facts are capable of direct phylogenetic +application, and furnish valuable proofs of the truth of the theory of +descent. + + A. Ehrenberg, in his list of fossil Polycystina (L. N. 25, pp. 64-85, + 1875), records 325 species of which 26 are still living. + + {clxxv}B. Stoehr, in his list of Miocene Radiolaria from Grotte (L. N. + 35, p. 84, 1880), records 118 species, of which 29 are still living. + + C. Teuscher, who at my request has made a large number of comparative + measurements and drawings, both of fossil and living Radiolaria, comes to + the conclusion that numerous SPUMELLARIA and NASSELLARIA from Barbados + are to-day extant and unchanged in the Radiolarian ooze of the deep + Pacific Ocean (compare s 242A, and p. 1760, Note). + + D. From the comparative investigations, which I have made during the last + ten years into the recent deep-sea Radiolaria of the Challenger + collection and the Miocene Polycystina of Barbados, it appears that about + a quarter of the latter are identical with living species of the former. + + + + +{clxxvi}BIBLIOGRAPHICAL SECTION. + + +CHAPTER XI.--LITERATURE AND HISTORY. + +251. _List of Publications from 1834 to 1884_:-- + + _Note._--In the text the references to the following publications are + indicated by the letters L. N. + + 1. 1834. MEYEN, F., Palmellaria (Physematium, Sphaerozoum), in Beitraege + zur Zoologie, gesammelt auf einer Reise um die Erde. _Nova Acta Acad. + Caes. Leop.-Carol._, vol. xvi., Suppl., p. 160, Taf. xxviii. figs. 1-7. + + 2. 1838. EHRENBERG, G., Polycystina (Lithocampe, Cornutella, Haliomma) in + Ueber die Bildung der Kreidefelsen und des Kreidemergels durch + unsichtbare Organismen. _Abhandl. d. k. Akad. d. Wiss. Berlin_, p. 117. + + 3. 1839. EHRENBERG, G., Ueber noch jetzt lebende Thierarten der + Kreidebildung (Haliomma radians). _Abhandl. d. k. Akad. d. Wiss. Berlin_, + p. 154. + + 4. 1844-1873. EHRENBERG, G., Vorlaeufige Mittheilungen ueber + Beobachtungen von Polycystinen. _Monatsber. d. k. preuss. Akad. d. Wiss. + Berlin_. Republished with illustrations in the Mikrogeologie (L. N. 6) + and in the two treatises of 1872 (L. N. 24) and 1875 (L. N. 25). Compare + the _Monatsberichte_ of 1844 (pp. 57, 182, 257), of 1846 (p. 382), of + 1847 (p. 40), of 1850 (p. 476), of 1854 (pp. 54, 205, 236), of 1855 (pp. + 292, 305), of 1856 (pp. 197, 425), of 1857 (pp. 142, 538), of 1858 (pp. + 12, 30), of 1859 (p. 569), of 1860 (pp. 765, 819), of 1861 (p. 222), of + 1869 (p. 253), of 1872 (pp. 300-321), of 1873 (pp. 214-263). Only one of + these small papers is of permanent value, The First Systematic + Arrangement of the Polycystina in 7 families, 44 genera, and 282 species + (_Monatsber. d. k. preuss. Akad. d. Wiss. Berlin_, 1847, p. 54). Compare + my Monograph (1862, L. N. 16), pp. 3-12, 214-219. + + 5. 1851. HUXLEY, TH., Upon Thalassicolla, a new Zoophyte. _Ann. and Mag. + Nat. Hist._, ser. 2, vol. viii. pp. 433-442, pl. xvi. + + 6. 1854. EHRENBERG, G., Mikrogeologie. Figures of numerous Polycystina + on 8 plates; Taf. xviii. figs. 110, 111; Taf. xix. figs. 48-56, 60-62; + Taf. xx. Nr. i., figs. 20-25, 42; Taf. xxi. figs. 51-56; Taf. xxii. figs. + 20-40; Taf. xxxv. A., Nr. xix. A. fig. 5; Taf. xxxv. B. figs. 16-23; Taf. + xxxvi. figs. 1-33. + + 7. 1855. BAILEY, J. W., Notice of Microscopic Forms of the Sea of + Kamtschatka. _Amer. Journ. Sci. and Arts_, vol. xxii. p. 1, pl. i. + + 8. 1855. MUELLER, JOHANNES, Ueber Sphaerozoum und Thalassicolla. + _Monatsber. d. k. preuss. Akad. d. Wiss. Berlin_, p. 229. + + 9. 1855. MUELLER, JOHANNES, Ueber die im Hafen von Messina beobachteten + Polycystinen (Haliomma, Eucyrtidium, Dictyospyris, Podocyrtis). + _Monatsber. d. k. preuss. Akad. d. Wiss. Berlin_, p. 671. + + 10. 1856. MUELLER, JOHANNES, Ueber die Thalassicollen, Polycystinen und + Acanthometren des Mittelmeeres. _Monatsber. d. k. preuss. Akad. d. Wiss. + Berlin_, p. 474. + + 11. 1858. MUELLER, JOHANNES, Erlaeuterung einiger bei St. Tropez am + Mittelmeer beobachteter Polycystinen und Acanthometren. _Monatsber. d. k. + preuss. Akad. d. Wiss. Berlin_, p. 154. + + 12. 1858. MUELLER, JOHANNES, Ueber die Thalassicollen, Polycystinen und + Acanthometren des Mittelmeeres, _Abhandl. d. k. Akad. d. Wiss. Berlin_, + pp. 1-62, Taf. i.-xi. (The fundamental treatise on the Radiolaria.) + + {clxxvii}13. 1858. SCHNEIDER, ANTON, Ueber zwei neue Thalassicollen von + Messina. _Archiv f. Anat. u. Physiol._, p. 38, Taf. iii. B, figs. 1-4. + + 14. 1858. CLAPAREDE et LACHMANN, Echinocystida (Plagiacantha et + Acanthometra). Etudes sur les Infusoires et les Rhizopodes, p. 458, pl. + xxii. figs. 8, 9; pl. xxiii. figs. 1-6. + + 15. 1860. HAECKEL, ERNST, Ueber neue lebende Radiolarien des + Mittelmeeres. _Monatsber. d. k. preuss. Akad. d. Wiss. Berlin_, pp. 794, + 835. + + 16. 1862. HAECKEL, ERNST, Die Radiolarien (Rhizopoda radiaria). Eine + Monographie. 572 pp. fol. with an Atlas of 35 Copperplates. + + 17. 1862. BURY, Mrs., Polycystins, figures of remarkable forms in the + Barbados Chalk Deposit. Ed. ii. By M. C. Cooke, 1868. 25 quarto plates, + photographed from drawings by hand, containing many forms overlooked by + Ehrenberg from Barbados. + + 18. 1863 HARTING, PAUL, Bijdrage tot de Kennis der mikroskopische Fauna + en Flora van de Banda-Zee (Diep-Zee-Polycystinen). _Verhandl. d. Kon. + Akad. van. Wetensch. Amsterdam_, vol. ix. p. 30, pls. i.-iii. + + 19. 1865. HAECKEL, ERNST, Ueber den Sarcode-Koerper der Rhizopoden + (Actinelius, Acanthodesmia, Cyrtidosphaera, &c.). _Zeitschr. f. wiss. + Zool._, Bd. xv. p. 342, Taf. xxvi. + + 20. 1867. SCHNEIDER, ANTON, Zur Kenntniss des Baues der Radiolarien + (Thalassicolla). _Archiv f. Anat. u. Physiol._, 1867, p. 509. + + 21. 1870. HAECKEL, ERNST, Beitraege zur Plastiden Theorie (Myxobrachia; + Amylum in den gelben Zellen). _Jenaische Zeitschr. fuer Naturw._, Bd. v. + p. 519-540, Taf. xviii. + + 22. 1871. CIENKOWSKI, L., Ueber Schwaermer-Bildung bei Radiolarien. + _Archiv f. mikrosk. Anat._, Bd. vii. p. 372-381, Taf. xxix. + + 23. 1872. WAGNER, N., Myxobrachia Cienkowskii. _Bull. d. Acad. St. + Petersburg_, vol. xvii. p. 140. + + 24. 1872. EHRENBERG, GOTTFRIED, Mikrogeologische Studien ueber das + kleinste Leben der Meeres-Tiefgruende aller Zonen und dessen geologischen + Einfluss. _Abhandl. d. k. Akad. d. Wiss. Berlin_, 1872. Mit 12 Tafeln. + (The Latin diagnoses of 113 new species here mentioned are given in the + _Monatsberichte_ of April 25, 1872, pp. 300-321.) + + 25. 1875. EHRENBERG, GOTTFRIED, Polycystinen-Mergel von Barbados + (Fortsetzung der Mikrogeologischen Studien). _Abhandl. d. k. Akad. d. + Wiss. Berlin_, 1875, 168 pag. mit 30 Tafeln. (The Latin diagnoses of 265 + species here recorded are given in Namensverzeichniss der fossilen + Polycystinen von Barbados. _Monatsber. d. k. preuss. Akad. d. Wiss. + Berlin_, Jan. 30, 1873, pp. 213-263.) + + 26. 1876. HERTWIG, RICHARD, Zur Histologie der Radiolarien. + Untersuchungen ueber den Bau und die Entwickelung der Sphaerozoiden und + Thalassicolliden. 91 pp. with 5 plates. + + 27. 1876. MURRAY, JOHN, Challengerida. Preliminary Reports on Work done + on board the Challenger. _Proc. Roy. Soc. Lond._, vol. xxiv. pp. 471-536, + pl. xxiv. + + 28. 1876. ZITTEL, KARL, Palaeozoologie, Bd. i. pp. 114-126, figs. 46-56. + + 29. 1876. ZITTEL, KARL, Ueber fossile Radiolarien der oberen Kreide. + _Zeitschr. d. deutsch. geol. Gesellsch._, Bd. xxviii. pp. 75-96, Taf. ii. + (with figures of six Cretaceous species). + + 30. 1877. MIVART, ST. GEORGE, Notes touching recent researches on the + Radiolaria. _Journ. Linn. Soc. Lond._ (Zool.), vol. xiv. pp. 136-186. + (Historical sketch of previous literature.) + + 31. 1877. WYVILLE THOMSON, The Voyage of the Challenger--The Atlantic, + vol. i. pp. 231-237, figs. 51-54; vol. ii. pp. 340-343, figs. 58, 59, &c. + + 32. 1878. HAECKEL, ERNST, Das Protistenreich, eine populaere Uebersicht + ueber das Formengebiet der niedersten Lebewesen, pp. 101-104. + + 33. 1879. HERTWIG, RICHARD, Der Organismus der Radiolarien. _Jenaische + Denkschriften_, Bd. ii. Taf. vi.-xvi. pp. 129-277. + + 34. 1879. HAECKEL, ERNST, Ueber die Phaeodarien, eine neue Gruppe + kieselschaliger mariner Rhizopoden. _Sitzungsb. med.-nat. Gesellsch. + Jena_, December 12, 1879. + + 35. 1880. STOEHR, EMIL, Die Radiolarien-Fauna der Tripoli von Grotte + (Provinz Girgenti in Sicilien). _Palaeontographica,_ Bd. xxvi. pp. + 71-124, Taf. xvii.-xxiii. A preliminary communication regarding this + fauna from the tripoli is given in _Tagebl. d. Naturf. Versamml. + Muenchen_, 1877. + + {clxxviii}36. 1880. PANTANELLI, DANTE, I Diaspri della Toscana e i loro + fossili. _Real. Accad. dei Lincei_, ser. 3, vol. vii. pp. 13-34, Tab. i. + Radiolaria di Calabria. _Atti. Soc. Tosc._, p. 59. + + 37. 1881. HAECKEL, ERNST, Prodromus Systematis Radiolarium, Entwurf eines + Radiolarien-Systems auf Grund von Studien der Challenger-Radiolarien. + _Jenaische Zeitschr. fuer Naturw._, Bd. xv. pp. 418-472. + + 38. 1881. BRANDT, KARL, Untersuchungen an Radiolarien. _Monatsber. d. k. + preuss. Akad. d. Wiss. Berlin_, (April 21), pp. 388-404, Taf. i. + + 39. 1882. BRANDT, KARL, Ueber die morphologische und physiologische + Bedeutung des Chlorophylls bei Thieren. I. Artikel. _Archiv f. Anat. u. + Physiol._, pp. 125-151, Taf. i. II. Artikel. _Mittheil. a. d. Zool. + Station zu Neapel_, Bd. iv. pp. 193-302, Taf. xix., xx. + + 40. 1882. BUETSCHLI, OTTO, Beitraege zur Kenntniss der + Radiolarien-Skelette, insbesondere der der Cyrtida. _Zeitschr. f. wiss. + Zool._, Bd. xxxvi. pp. 485-540, Taf. xxxi.-xxxiii. + + 41. 1882. BUETSCHLI, OTTO, Radiolaria. In Bronn's Klassen und Ordnungen + des Thierreichs. Bd. i., Protozoa, pp. 332-478, Taf. xvii.-xxxii. + + 42. 1882. GEDDES, PATRICK, Further Researches on Animals containing + Chlorophyll. _Nature_, pp. 303-305. + + 43. 1882. GEDDES, PATRICK, On the Nature and Functions of the "Yellow + Cells" of Radiolarians and Coelenterates. _Proc. Roy. Soc. Edin._, p. + 377. + + 44. 1882. DUNIKOWSKI, EMIL, Die Spongien, Radiolarien und Foraminiferen + der Unter-Liassischen Schichten vom Schafberg bei Salzburg. _Denkschr. d. + k. Akad. d. Wiss. Wien_, Bd. xlv. pp. 22-34. Taf. iv.-vi. + + 45. 1882. PANTANELLI, DANTE, Fauna miocenica di Radiolari del Appennino + settentrional. _Boll. Soc. Geol. Ital._ + + 46. 1883. HAECKEL, ERNST, Die Ordnungen der Radiolarien (Acantharia, + Spumellaria, Nassellaria, Phaeodaria). _Sitzungsb. med.-nat. Gesellsch. + Jena_, February 16, 1883. + + 47. 1883. HERTWIG, OSCAR, Die Symbiose oder das Genossenschaftsleben im + Thierreich. 56. _Versamml. Deutscher Naturf. u. Aerzte_, Freiburg i/B. + + 48. 1883. RUEST, WILHELM, Ueber das Vorkommen von Radiolarien-Resten in + kryptokrystallinischen Quarzen aus dem Jura und in Koprolithen aus dem + Lias. 56. _Versamml. Deutscher Naturf. u. Aerzte_, Freiburg i/B. + + 49. 1884. CAR, LAZAR, Acanthometra hemicompressa (= Zygacantha + semicompressa). _Zool. Anzeiger_, p. 94. + + 50. 1884. HAECKEL, ERNST, Ueber die Geometrie der Radiolarien + (Promorphologie). _Sitzungsb. med.-nat. Gesellsch. Jena_, November 22, + 1883. + + +251 A. _Supplementary List of Works Published in_ 1885:-- + + 51. 1885. D. RUEST, Beitraege zur Kenntniss der fossilen Radiolarien aus + Gesteinen des Jura. 45 pp. 4to, and 20 plates. _Palaeontographica_, Bd. + xxxi. (oder iii. Folge, vii. Band). + + 52. 1885. KARL BRANDT, Die koloniebildenden Radiolarien (Sphaerozoeen) + des Golfes von Neapel und der angrenzenden Meeres-Abschnitte. 276 pp. + 4to, and 8 plates. + + 53. 1885. JOHN MURRAY, Narrative of the Cruise of H.M.S. Challenger, with + a general account of the scientific results of the Expedition. Vol i. + First part, pp. 219-227, pl. A. Second part, pp. 915-926, pl. N. fig. 2. + + 54. 1885. ERNST HAECKEL, System der Acantharien. _Sitzungsb. med.-nat. + Gesellsch. Jena_, November 13. + + Since the printing of this Report began in 1884 and was far advanced in + 1885, it was impossible to include the important works of Ruest and + Brandt (L. N. 51, 52) in the descriptive portion, so that they are only + referred to in the Introduction. + +251 B. _Phaulographic Appendix_:-- + + A list of absolutely worthless literature, which contains either only + long known facts or false statements, and may hence be entirely + neglected with advantage. Compare s 252, and also L. N. 26, p. 9. + + 55. 1865. WALLICH, G. C., On the structure and affinities of Polycystina. + _Trans. Micr. Soc. Lond._, vol. xiii. pp. 57-84. (Compare L. N. 26, p. + 9.) + + {clxxix}56. 1879. WALLICH, G. C., Observations on the Thalassicollidae. + _Ann. and Mag. Nat. Hist._, ser. 4, vol. iii. p. 97. + + 57. 1866. STUART, ALEXANDER, Ueber Coscinosphaera ciliosa, eine neue + Radiolarie (= Globigerina echinoides!!). _Zeitschr. f. wiss. Zool._, Bd. + xvi. p. 328, Taf. xviii. (Compare L. N. 26, p. 9.) + + 58. 1870. STUART, ALEXANDER, Neapolitanische Studien. _Goettinger + Nachr._, p. 99, and _Zeitschr. f. wiss. Zool._, Bd. xxii. p. 290 ("Blue + Siliceous Crystals" in Collozoum inerme!). + + 59. 1871. MACDONALD, JOHN DENIS, Remarks on the Structure of Polycystina + (Astromma Yelvertoni = Euchitonia Muelleri). _Ann. and Mag. Nat. Hist._, + ser. 4, vol. viii. p. 226. + + 60. 1871. DOENITZ, W., Beobachtungen ueber Radiolarien. _Archiv f. Anat. + u. Physiol._, 1871, p. 71, Taf. ii. (Compare L. N. 26, p. 7.) + + +252. _Progress of our Knowledge of the Radiolaria from_ 1862 _to_ +1885.--The history of our scientific knowledge of the Radiolaria extends +over about half a century (from 1834 to 1885). A historical and critical +discussion of the works which appeared within the first twenty-eight years +of this period (from 1834 to 1862) is contained in the historical +introduction to my Monograph (L. N. 16, pp. 1-24); I shall therefore +give here only a brief survey of the investigations published during +the last twenty-three years (from 1862 to 1885). The most important +steps in our progress during this period we owe to the following +naturalists:--Cienkowski (1871), Ehrenberg (1872 and 1875), Richard Hertwig +(1876 and 1879), Karl Brandt (1881 and 1885), Buetschli (1882), and Ruest +(1885). To the valuable works of these authors must be added a number of +smaller contributions, which are recorded in the foregoing Bibliography. +Some communications from dilettanti, written with insufficient knowledge of +the subject, and hence of no value, are mentioned for the sake of +completeness in the "Phaulographic Appendix" (compare L. N. 55-60, also L. +N. 26, p. 9). + +The first important advance in our knowledge of the organisation of the +Radiolaria, made after the publication of my Monograph (1862), was the +demonstration of the nature of the extracapsular "yellow cells." In the +year 1870 I showed that these yellow cells contain starch (L. N. 21, p. +519). I regarded them, as did all authors up to that time, as integral +parts of the Radiolarian organism, and hence considered this to be +multicellular; for no doubt was possible regarding the true cellular nature +of these remarkable, nucleated, yellow globules, which I had thoroughly +studied in 1862. It was first shown by Cienkowski in 1871 that the yellow +cells of the #Collodaria# remain unchanged even after the death of these +organisms, "that they continue to grow uninterruptedly, and eventually +multiply by division" (L. N. 22, pp. 378-380, Taf. xix. figs. 30-36). +Cienkowski concluded from these important observations that the yellow +cells are not integral parts of the Radiolarian body, but "parasitic +structures," independent, unicellular organisms, which live only as +parasites in the body of the Radiolaria (compare s 90). + +This important recognition underwent ten years later a further development +and complete establishment by the extensive investigations of Karl Brandt +(L. N. 38, 39) {clxxx}and Patrick Geddes (L. N. 42, 43). This arrangement +was compared by Brandt to the remarkable symbiosis of the Algoid gonidia +and Fungoid hyphae in the organisation of the Lichens, which had been +recently discovered, and since he recognised the independent nature of the +yellow cells, as unicellular Algae, in all divisions of the Radiolaria, he +founded for them the genus _Zooxanthella_. Geddes named them _Philozoon_, +and showed experimentally that they give out oxygen under the influence of +sunlight (compare s 90). The great physiological importance of the yellow +cells in the metastasis of the Radiolaria, and, when they are developed in +large quantities, in the economy of marine organisms in general, has +recently been insisted upon by Brandt (see s 205 and L. N. 52, pp. 65-71, +86-94). + +The proof that the yellow cells do not belong to the Radiolarian organism +itself, but only live parasitically in it, was a necessary preliminary to +the very important step which next took place in our knowledge of the +organisation of the Radiolaria. This step consisted in the demonstration +that the whole body of the Radiolaria, like that of all other Protista, is +only a single cell. It was Richard Hertwig who in two remarkable works (L. +N. 26, 33) firmly established this fundamental theorem of the unicellular +nature of the Radiolaria. In his treatise on the histology of the +Radiolaria (L. N. 26, 1876) he published complete investigations into the +structure and development of the Sphaerozoida and Thalassicollida. Since he +made use of the modern methods of histological examination, and especially +of staining fluids, which he was the first to apply to the study of the +Radiolaria, he was able to show that no true cells (apart from the +parasitic yellow cells) are to be found in their bodies, but rather that +all their morphological components are to be regarded as differentiated +parts of a single true cell, and in particular that the central capsule +includes a genuine nucleus. + +A wider foundation for this important discovery and its applicability to +all divisions of this extensive class, was given by Hertwig in a second +work on the organisation of the Radiolaria (L. N. 33, 1879). Among the +numerous discoveries by which this work enriched the natural history of the +Radiolaria must be specially mentioned the recognition of the fundamental +differences exhibited by the main divisions of the class in the structure +of their central capsule. Hertwig first observed that the capsular membrane +is double in the PHAEODARIA but single in the other Radiolaria (s 56); the +former he named "TRIPYLEA" because he discovered in their capsular membrane +a large, peculiarly constructed main opening and two small accessory +openings. The NASSELLARIA, in which he found a single porous area at the +basal pole of the main axis, with a cone of pseudopodia rising from it, he +called on this account "MONOPYLEA"; whilst the other Radiolaria, whose +capsular membrane is perforated on all sides with fine pores, were termed +"PERIPYLEA." Besides the central capsule, Hertwig laid stress upon the +significance of the gelatinous envelope as a constant and important +constituent of the body. He also devoted attentive consideration to the +morphology of the skeleton, and on the basis of certain +{clxxxi}phylogenetic conclusions which he drew from it, he arrived at an +improved systematic arrangement in which he distinguished six orders:--(1) +#Thalassicollea#, (2) #Sphaerozoea#, (3) #Peripylea#, (4) #Acanthometrea#, +(5) #Monopylea#, (6) #Tripylea#. The numerous isolated discoveries with +which Hertwig enriched the morphology of the Radiolaria, have been already +alluded to in the appropriate paragraphs in the anatomical portion of this +Introduction (see L. N. 42, pp. 340, 341). + +The new and interesting group, which was thus erected into an order under +the name TRIPYLEA, I had already a year previously separated from the other +Radiolaria as "_Pansolenia_" in my Protistenreich (L. N. 32, p. 102). +Since, however, neither the three capsular openings of the TRIPYLEA nor the +skeletal tubes of the Pansolenia are present in all the families of this +extensive order, I substituted in 1879 the more suitable name PHAEODARIA, +which is applicable to all members of the group (L. N. 34). In the +preliminary memoir then published regarding the Phaeodaria, a New Group of +Siliceous Marine Rhizopods, I distinguished four orders, ten families, and +thirty-eight genera. The great majority of these new forms (among which +were no less than 465 different species) were first discovered by the +deep-sea investigations of the Challenger. John Murray was the first who +called attention to the great abundance in the deep sea of these remarkable +Rhizopods, and to the constant presence of their peculiar, dark, +extracapsular pigment body (phaeodium); even in 1876 he described a portion +of them as Challengerida (L. N. 27, p. 536; L. N. 53, p. 226). The earliest +observations on the PHAEODARIA were made at Messina in 1859, where I +examined five genera of this remarkable group alive (compare p. 1522 and L. +N. 16). + +By the discovery that the PHAEODARIA, although differing in important +respects from the other Radiolaria, still conform to the definition of the +class, a new and extensive series of forms was added to this latter, and by +their closer investigation a fresh source of interesting morphological +problems was disclosed. In other groups, however, morphology was advanced +by comparative anatomical studies. In addition to the smaller contributions +of various authors, mentioned in the foregoing bibliography, I may +specially refer to the valuable Beitraege zur Kenntniss der +Radiolarien-Skelete, insbesondere der der Cyrtida by O. Buetschli (L. N. +40, 1882). On the basis of careful comparative anatomical studies, +investigations into the skeletal structure of a number of fossil +#Cyrtoidea# and critical application of the recently published researches +of Ehrenberg into the Polycystina of Barbados (L. N. 25), Buetschli +attempted to derive the complicated relations of the Monopylean skeletons +phylogenetically from a simple primitive form,--the primary sagittal ring. +Even if this attempt did not actually solve the very difficult +morphological problem in question, still the critical and synthetic mode in +which it was carried out deserves full recognition, and furnishes the proof +that the comparative anatomy of the skeleton in the Radiolaria not less +than in the Vertebrata, is a most interesting and fruitful field of +phylogenetic investigation. A {clxxxii}further demonstration of this was +furnished by Buetschli in the general account of the organisation of the +Radiolaria which he published in 1882 in Bronn's Klassen und Ordnungen des +Thierreichs (L. N. 41). + +In our knowledge of the developmental history of these Protista the last +two decades have witnessed less progress than in their comparative anatomy. +The most important advance in this direction has been the proof that in all +the main groups of the class the contents of the central capsule are used +in the formation of swarm-spores. The movements of these zoospores in the +central capsule had indeed been observed by several previous authors in the +case of the SPUMELLARIA and ACANTHARIA (L. N. 10, 13, 16; compare also s +142, Note A). The origin of the flagellate spores from the contents of the +central capsule and their peculiar constitution were, however, first +described fully by Cienkowski in 1871 (L. N. 22, p. 372). Soon after this, +R. Hertwig discovered that in the social Radiolaria (Polycyttaria or +Sphaerozoea) two different forms of zoospores are formed, one with, the +other without crystals, and that the latter are also divided into +macrospores and microspores (compare L. N. 26, and s 142). Recently this +sexual differentiation has been shown by Karl Brandt to exist in all the +groups of Sphaerozoea, and its regular interchange with the formation of +crystal-spores has been interpreted as a true "alternation of generations" +(compare L. N. 52 and also s 216). The other forms of development also, +especially reproduction by cell-division (s 213) and gemmation (s 214), +have been elucidated by the recent investigations of the same author. + +The palaeontology of the Radiolaria has of late made important and +interesting advances. Until ten years ago fossil remains of this class were +known exclusively from the Tertiary period; almost the only source of our +information was to be found in the researches of Ehrenberg, commenced in +1838, continued in his Mikrogeologie in 1854, and concluded in his last +work (L. N. 25) published in 1875 (compare L. N. 16, pp. 3-9, 191-193). In +the year 1876 a number of Mesozoic Radiolaria from the chalk were described +by Zittel (L. N. 28), and afterwards others from the Jura by Dunikowski (L. +N. 44). That fossil Radiolaria occur in Mesozoic formations, especially in +the Jura, as well preserved and as abundantly as in the Tertiary rocks of +Barbados, was shown in 1883 by Ruest (L. N. 48). By the examination of +numerous thin sections he discovered that in all the main divisions of the +Jurassic formation (Lias, Dogger, Malm) there are distributed jaspers, +flints, cherts, and other quartzites, which consist largely of the +siliceous shells of Polycystina; the same is true also of many Coprolites +found in the Jura. The full account of these and the descriptions and +figures of 234 Jurassic species, distributed in 76 genera, are contained in +the Beitraege zur Kenntniss der fossilen Radiolarien aus Gesteinen des Jura +(L. N. 51, 1885). But even in the older rocks, the Trias, the Permian, and +Carboniferous systems, and even as far downwards as the Silurian and +Cambrian formations, Ruest has recently shown the existence of fossil +Radiolaria, {clxxxiii}and thus increased the known period of the +developmental history of the class by many millions of years (s 244). + +The great significance of the Radiolaria in geology and palaeontology has +been brought into new light not only by these extensive discoveries, but +also by the important relations which have been shown to exist between the +Radiolarian rocks and the deep-sea deposits of the present day. In this +direction the wonderful discoveries of the Challenger, and especially the +investigation of the deep-sea deposits by Wyville Thomson (L. N. 31) and +John Murray (L. N. 27), have furnished us with new and valuable information +(compare ss 236-239, and ss 245-250). The Tertiary Polycystine formations +of Barbados and the Nicobar Islands, with which we have been acquainted for +the last forty years, as also the Mesozoic Radiolarian quartzes, which have +only recently been made known to us from the Jura, are ascertained to be +fossil representatives of the same deep-sea deposits which now occur in the +form of Radiolarian ooze (s 237), and to some extent also of Globigerina +ooze and red clay (ss 238, 239), on the bottom of the ocean, at depths of +from 2000 to 4500 fathoms. + +These investigations into fossil Radiolaria and their comparison with +recent deep-sea forms have a further general significance, inasmuch as the +identity of many living and fossil species from the Tertiary formation has +been shown beyond all doubt. In this direction the numerous measurements +and accurate comparisons which I have made during the last ten years of the +abyssal forms in the Challenger collection, and of fossil species from +Barbados and Caltanisetta, have brought to light many important facts. In +this I had the able assistance of my friend, Dr. Reinhold Teuscher (compare +s 250, and p. 1760). Further valuable contributions in this direction are +found in the careful observations and comparative measurements recently +published by Emil Stoehr (L. N. 35, 1880), regarding the Radiolarian fauna +of the Tripoli of Grotte in the province of Girgenti, Sicily. From these it +appears that the number of Miocene species which are still extant, is much +greater than would appear from the results of Ehrenberg. + +Ehrenberg himself, towards the end of his long and laborious life, +collected the results of the systematic and palaeontological researches, +which he had begun thirty-seven years previously (L. N. 16, pp. 3-12) into +the Polycystina, in two large works (L. N. 24, 25). The first treatise (L. +N. 24, 1872) contains the Mikrogeologische Studien ueber das Kleinste Leben +der Meeres-Tiefgruende aller Zonen und dessen geologischen Einfluss, with a +list of 279 Polycystina observed by him from the deep-sea, as well as +figures of 127 species. The second work (L. N. 25, 1875) contains the +Fortsetzung der Mikrogeologischen Studien, mit specieller Ruecksicht auf +den Polycystinen-Mergel von Barbados; the list of fossil Polycystina +observed by him includes 325 species, of which 26 are still extant; 282 of +them are figured on the thirty plates accompanying the memoir. By means of +these numerous figures, as well as by the appended systematic and +chorological tables, Ehrenberg furnished a welcome {clxxxiv}supplement to +the numerous communications regarding the Polycystina, which he had made to +the Berlin Academy since 1838, and which he had published in his +Mikrogeologie in 1854. It will always be the merit of this zealous and +indefatigable microscopist that he first called attention to the great +wealth of forms existing in this class; he separated systematically about +500 species, and published drawings of about 400; in addition to which he +was the first to lay stress upon the great chorological and geological +importance of the Radiolaria. + +With these systematic and descriptive, chorological and palaeontological +works, however, which relate exclusively to the Polycystina, the merits of +the famous naturalist of Berlin are exhausted as regards this class of +animals. Of the organisation of the Radiolaria, Gottfried Ehrenberg +remained entirely ignorant up till his death in 1876. All that a number of +famous naturalists had observed during a quarter of a century as to the +structure and life-history of the Radiolaria, all the important discoveries +of Huxley (1851), Johannes Mueller (1858), Claparede (1858), Cienkowski +(1871), and many others (L. N. 1-22), and all that I had published in my +Monograph (1862) on the basis of three years' study of their anatomy and +physiology--all this Ehrenberg ignored, or rather, he regarded it all as +worthless rubbish of science, as a chaos of devious errors, resting upon +incomplete observations and false conclusions. His strange "special +considerations regarding the Polycystina" (L. N. 24, pp. 339-346) and the +general "concluding remarks" (L. N. 25, pp. 146-147) leave no room for +doubt on this point. Ehrenberg indeed doubted to the last whether any +observer had seen living Radiolaria at all (L. N. 25, p. 108). + +The invincible obstinacy with which Ehrenberg maintained his preconceived +opinion of the high organisation of the Radiolaria, and entirely ignored +the contrary observations of other naturalists, is explained by the +consistency with which he held to the end the "principle peculiar to +himself of the universally equal development of the animal kingdom" (L. N. +16, p. 7). From the complicated arrangement of their siliceous shells he +concluded that the animals inhabiting them must possess a structure +correspondingly complex, and nearly related to that of the Echinodermata +(Holothuria). Like all other animals the Radiolaria must possess systems of +organs for locomotion, sensation, nutrition, circulation, and reproduction. +Whilst Ehrenberg originally interpreted the Polycystina as siliceous +Infusoria polygastrica, and regarded them as compound Arcellina, he +afterwards classed them sometimes with the Echinodermata (Holothuria), +sometimes with the Bryozoa, sometimes with the Oscillaria (see L. N. 41, p. +336). Although a decided opponent of the cell-theory he called them +"multicellular animalcules" (Polycystina), interpreting the pores of the +siliceous shell as cells. To-day the opposite term (Monocystina) might be +adopted to express their unicellular organisation. It was a remarkable +irony of fate that in the self-same year (1838) in which Schwann of Berlin +made by his foundation of the cell theory the greatest advance in the whole +{clxxxv}of Biological Science, that Ehrenberg, all his life the most +zealous opponent of that theory, published his great work on the Infusoria, +and at the same time established the "family of multicellular animalcules +or Polycystina" (L. N. 16, p. 4). + +The "short systematic survey of the genera of cellular animalcules" given +by Ehrenberg in 1875 (L. N. 25, p. 157), is only a new edition, increased +by sixteen genera, of his first systematic arrangement of the Polycystina +of 1847 (L. N. 4, p. 53). Since I have already given a full discussion of +this in my Monograph (L. N. 16, pp. 214-219), I need only here remark that +a correct understanding of his very inadequate generic diagnoses is only +possible by the aid of his figures. Relying upon these I have retained +almost all Ehrenberg's genera, although entirely new definitions of most of +them have been necessary. + +The same is true also of the two orders which Ehrenberg distinguished in +his class of "Zellenthierchen." The first order is constituted by his +"Netzkoerbchen" (Monodictya or NASSELLARIA) formerly known as "Polycystina +solitaria"; they include our #Cyrtoidea#, the greater part of Hertwig's +Monopylea. Ehrenberg's second order is the "Schaumsternchen" (Polydictya or +SPUMELLARIA), previously called "Polycystina composita"; they include the +Peripylea of Hertwig, as well as the Spyridina (our #Spyroidea#), which +belong properly to the NASSELLARIA. Although Ehrenberg's statements +regarding the organisation of both these orders were quite erroneous, and +his knowledge even of the structure of their shells very defective, I still +thought it advisable to retain his names for the groups, since they +constituted his one successful effort in the systematic treatment of the +Radiolaria (compare L. N. 41, p. 336). + +The sketch of a systematic arrangement of the Radiolaria (L. N. 37), which +I published in 1881 on the basis of the study of the Challenger Radiolaria, +resembles, in respect of seven orders being distinguished, the new system +which R. Hertwig founded in 1879, in consequence of the variations which he +discovered in the structural relations of the central capsule (L. N. 33, p. +133). It differs, however, inasmuch as his Sphaerozoea (my Polycyttaria) +are here divided into two orders, Symbelaria (#Collosphaerida#) and +Syncollaria (#Sphaerozoida#). In that sketch too I separated for the first +time the two subclasses Holotrypasta (Porulosa) and Merotrypasta +(Osculosa). The fifteen families established by Hertwig were then raised to +twenty-four. The six hundred and thirty genera, which I then distinguished, +are still for the most part retained, some, however, in a restricted sense, +or with amended definitions. + +The differential characters of the orders and families of the Radiolaria, +given in the Prodromus in 1881, were amended in a further communication +which I gave in 1883 regarding the orders of the Radiolaria (L. N. 46, p. +17). There I reduced the seven orders to four, the structural relations of +the central capsule being precisely the same in the Polycyttaria and +#Collodaria# as in the #Peripylea#. The survey of the affinities of the +class was thus rendered much simpler and clearer, and the +{clxxxvi}hypothetical genealogical tree, which I then published, has been +still further carried out in Chapter VI. of the present Introduction (see +ss 153-200). + + +253. _General Survey of the Growth of our Systematic Acquaintance with the +Radiolaria from 1834 to 1885._ + + 1834. MEYEN (L. N. 1) describes 2 genera and species of + #Collodaria#:--_Sphaerozoum fuscum_ and _Physematium atlanticum_. + + 1838. EHRENBERG (L. N. 2) founds the family Polycystina upon 3 fossil + genera (with 6 species):--_Lithocampe_, _Cornutella_, _Haliomma_. + + 1847. EHRENBERG (L. N. 4) publishes his preliminary communications + regarding the fossil Polycystina of Barbados and distinguishes 282 + species, distributed in 44 genera and 7 families. In the tabular view of + the genera he distinguishes two orders:--I. #Solitaria#--(1) + Halicalyptrina, (2) Lithochytrina, (3) Eucyrtidina; and II. + #Composita#--(4) Spyridina, (5) Calodictya, (6) Haliommatina, (7) + Lithocyclidina (compare L. N. 16, pp. 214-219). + + 1851. HUXLEY (L. N. 5) gives the first accurate account of living + Radiolaria, and describes 2 species of the genus _Thalassicolla_ + (_nucleata_ and _punctata_); under the latter are included 4 genera of + #Sphaerozoea#:--_Collozoum_, _Sphaerozoum_, _Collosphaera_, + _Siphonosphaera_ (compare L. N. 16, pp. 12-14). + + 1854. EHRENBERG (L. N. 6) publishes in his Mikrogeologie, figures of + seventy-two species of fossil Polycystina (without descriptions). + + 1855. JOHANNES MUELLER (L. N. 8, p. 248) describes the first + _Acanthometra_, and elucidates its affinity to Huxley's _Thalassicolla_ + and Ehrenberg's Polycystina. + + 1858. JOHANNES MUELLER (L. N. 12) establishes the new group Radiolaria as + a special order of the Rhizopoda, and includes in it the Thalassicolla, + Polycystina, and Acanthometra as closely related families. He opposes + these radiate Rhizopoda to the Polythalamia, and describes 50 species + observed by him living in the Mediterranean, these he arranges in 20 + genera, of which 10 are new. The figures are contained in eleven plates + (see L. N. 16, pp. 22-24). + + 1858. CLAPAREDE (L. N. 14) describes the first #Plectoidean# + (_Plagiacantha arachnoides_) and two species of _Acanthometra_, which he + had observed living in Norway (see L. N. 16, p. 18). + + 1860. EHRENBERG (L. N. 4) gives a short diagnosis of 22 new genera of + Polycystina, based on the investigation of numerous deep-sea species + brought up by Brooke from the depths of the Pacific Ocean. The number of + his genera is thus increased to 66 (compare L. N. 16, pp. 10, 11). + + 1862. ERNST HAECKEL (L. N. 16) embraces in his Monograph of the + Radiolaria all the species hitherto known either by figures or + descriptions, and arranges them in 15 families and 113 genera; of which + latter 46 are new. The number of new species observed living amounts to + 144. In a "survey of the Radiolarian fauna of Messina" (p. 565) he + records 72 genera and 169 species. Most of these are figured in the + accompanying atlas of thirty-five plates. + + {clxxxvii}1862. BURY (L. N. 17) gives in an atlas of twenty-five plates, + photographed from drawings, the figures of numerous fossil Polycystina of + Barbados (without descriptions), of which many are new species overlooked + by Ehrenberg (compare s 242, above). + + 1872. EHRENBERG (L. N. 24) gives a list of names (without description) of + all the Polycystina observed by him from the bottom of the sea, 279 + species, of which 127 are figured on twelve plates. + + 1875. EHRENBERG (L. N. 25) gives a list of names of all the fossil + Polycystina observed by him (from Barbados, the Nicobar Islands and + Sicily), 326 species, of which 282 are figured (compare s 242 above). In + a new "Systematic Survey of the Genera" the number of these is given as + 63. The 7 families are the same as given in 1847 (see above), as also the + two orders (NASSELLARIA = Solitaria, SPUMELLARIA = Composita). + + 1876. ZITTEL (L. N. 29) describes the first fossil Radiolaria from the + chalk (6 species) and establishes the new Cyrtoid genus _Dictyomitra_. + + 1876. JOHN MURRAY (L. N. 27) establishes the new family Challengerida, + and figures 6 new generic types of PHAEODARIA. + + 1879. RICHARD HERTWIG (L. N. 33) first describes the fundamental + differences in the structure of the central capsule, and in accordance + with them divides the Radiolaria into six orders:--(1) Thalassicollea, + (2) Sphaerozoea, (3) Peripylea, (4) Acanthometrea, (5) Monopylea, (6) + Tripylea (p. 133). These are subdivided into 18 families, and their + phylogenetic affinities discussed (p. 137). On the ten plates, several + new species from Messina are figured, among them the types of several new + genera (_Cystidium_, _Coelacantha_, _Echinosphaera_) (compare s 252). + + 1879. ERNST HAECKEL (L. N. 34) founds the order PHAEODARIA as a "new + group of marine siliceous Rhizopods," and distinguishes in it 4 + suborders, 10 families and 38 genera. + + 1880. EMIL STOEHR (L. N. 35) describes the Miocene "Radiolarian fauna of + the tripoli from Grotte in Sicily," 118 species, of which 78 are new; + among them is the new genus _Ommatodiscus_, the type of a new family, + Ommatodiscida. The new species are figured on seven plates. + + 1880. DANTE PANTANELLI (L. N. 36) describes 30 species of fossil + Polycystina from the jaspers of Tuscany, which he regarded as Eocene, but + which were probably of Jurassic origin (compare s 243, note B, above). + + 1881. ERNST HAECKEL (L. N. 37) publishes a "Sketch of a classification of + the Radiolaria on the basis of the study of the Challenger Collection," + and distinguishes in his "conspectus ordinum" (p. 421) 2 subclasses and 7 + orders, and in the "prodromus systematis Radiolarium" (pp. 423-472) 24 + families with 630 genera, among which are more than 2000 new species. + + 1882. BUETSCHLI (L. N. 40) on the basis of studies of the fossil + Monopylea of Barbados, investigates the "mutual relations of the + Acanthodesmida, Zygocyrtida and Cyrtida," and gives a critical revision + of the genera of these "Cricoidea;" a number of new species are described + and figured (Tafs. xxxii., xxxiii.), and some new genera of Stichocyrtida + established (_Lithostrobus_, _Lithomitra_, &c.). + + 1882. DUNIKOWSKI (L. N. 44) describes 18 new fossil Polycystina from the + lower lias of the Salzburg Alps, among them the types of 3 new genera + (_Ellipsoxiphus_, _Triactinosphaera_, and _Spongocyrtis_). + + {clxxxviii}1883. ERNST HAECKEL (L. N. 46) revises the 4 orders and 32 + families of Radiolaria, and gives more accurate definitions of them, as + well as of the 2 subclasses (I. _Holotrypasta_ = ACANTHARIA and + SPUMELLARIA; II. _Merotrypasta_ = NASSELLARIA and PHAEODARIA). + + 1885. D. RUEST (L. N. 51) describes 234 new species of fossil Radiolaria + from the Jura, and illustrates them by twenty plates. Among them are 103 + SPUMELLARIA, 130 NASSELLARIA, and 1 PHAEODARIA; these are contained in 35 + genera, of which 20 belong to the Porulosa, and 15 to the Osculosa. + + +254. _Statistical Synopsis of the Twenty Orders_:-- + + + (a) Number of Families. + (b) Number of Genera. + (c) Number of Species. + (d) Previously known Species. + (e) New Species. + (f) Fossil Species. + (g) Pelagic Abundance. + (h) Abyssal Abundance. + (i) Figured on Plates + + +-----+-----+------+-----+------+-----+-----+-----+-------------------+ + | | | | | | | | | Figured on | + | (a) | (b) | (c) | (d) | (e) | (f) | (g) | (h) | Plates. | + +-----+-----+------+-----+------+-----+-----+-----+-------------------+ + | I. Legion SPUMELLARIA (Porulosa peripylea) | + +-----+---------------------------------------------------------------+ + | | I. COLLODARIA (Spumellaria palliata) | + +-----+-----+---------------------------------------------------------+ + | | 1. Colloidea | + +-----+-----+------+-----+------+-----+-----+-----+-------------------+ + | 2 | 6 | 36 | 9 | 27 | 0 | A | E | 1, 3 | + +-----+-----+------+-----+------+-----+-----+-----+-------------------+ + | | 2. Beloidea | + +-----+-----+------+-----+------+-----+-----+-----+-------------------+ + | 2 | 8 | 56 | 9 | 47 | 0 | A | D | 2, 4 | + +-----+-----+------+-----+------+-----+-----+-----+-------------------+ + | | II. SPHAERELLARIA (Spumellaria loricata) | + +-----+-----+---------------------------------------------------------+ + | | 3. Sphaeroidea | + +-----+-----+------+-----+------+-----+-----+-----+-------------------+ + | 6 | 107 | 660 | 105 | 555 | 66 | A | B | { 5-8 | + | | | | | | | | | { 11-30 | + +-----+-----+------+-----+------+-----+-----+-----+-------------------+ + | | 4. Prunoidea | + +-----+-----+------+-----+------+-----+-----+-----+-------------------+ + | 7 | 53 | 280 | 35 | 245 | 36 | B | B | { 16, 17 | + | | | | | | | | | { 39, 40 | + +-----+-----+------+-----+------+-----+-----+-----+-------------------+ + | | 5. Discoidea | + +-----+-----+------+-----+------+-----+-----+-----+-------------------+ + | 6 | 91 | 503 | 126 | 376 | 102 | B | A | { 31-38 | + | | | | | | | | | { 41-48 | + +-----+-----+------+-----+------+-----+-----+-----+-------------------+ + | | 6. Larcoidea | + +-----+-----+------+-----+------+-----+-----+-----+-------------------+ + | 9 | 51 | 260 | 8 | 252 | 0 | E | B | { 9, 10 | + | | | | | | | | | { 49, 50 | + +-----+-----+------+-----+------+-----+-----+-----+-------------------+ + | II. Legion ACANTHARIA (Porulosa actipylea) | + +-----+---------------------------------------------------------------+ + | | III. ACANTHOMETRA (Acantharia palliata) | + +-----+-----+---------------------------------------------------------+ + | | 7. Actinelida | + +-----+-----+------+-----+------+-----+-----+-----+-------------------+ + | 3 | 6 | 22 | 6 | 16 | 0 | E | E | 129 (figs. 1-3) | + +-----+-----+------+-----+------+-----+-----+-----+-------------------+ + | | 8. Acanthonida | + +-----+-----+------+-----+------+-----+-----+-----+-------------------+ + | 3 | 21 | 138 | 50 | 88 | 0 | A | C | 130-132 | + +-----+-----+------+-----+------+-----+-----+-----+-------------------+ + | | IV. ACANTHOPHRACTA (Acantharia loricata) | + +-----+-----+---------------------------------------------------------+ + | | 9. Sphaerophracta | + +-----+-----+------+-----+------+-----+-----+-----+-------------------+ + | 3 | 27 | 149 | 9 | 140 | 0 | B | B | 133-138 | + +-----+-----+------+-----+------+-----+-----+-----+-------------------+ + | | 10. Prunophracta | + +-----+-----+------+-----+------+-----+-----+-----+-------------------+ + | 3 | 11 | 63 | 5 | 58 | 0 | D | B | 139, 140 | + +-----+-----+------+-----+------+-----+-----+-----+-------------------+ + | III. Legion NASSELLARIA (Osculosa monopylea) | + +-----+---------------------------------------------------------------+ + | | V. PLECTELLARIA (Nassellaria palliata) | + +-----+-----+---------------------------------------------------------+ + | | 11. Nassoidea | + +-----+-----+------+-----+------+-----+-----+-----+-------------------+ + | 1 | 2 | 5 | 1 | 4 | 0 | E | E | 91 (fig. 1) | + +-----+-----+------+-----+------+-----+-----+-----+-------------------+ + | | 12. Plectoidea | + +-----+-----+------+-----+------+-----+-----+-----+-------------------+ + | 2 | 17 | 61 | 5 | 56 | 0 | D | C | 91 (figs. 2-12) | + +-----+-----+------+-----+------+-----+-----+-----+-------------------+ + | | 13. Stephoidea | + +-----+-----+------+-----+------+-----+-----+-----+-------------------+ + | 4 | 40 | 205 | 14 | 191 | 17 | C | B | { 81, 82 | + | | | | | | | | | { 92-94 | + +-----+-----+------+-----+------+-----+-----+-----+-------------------+ + | | VI. CYRTELLARIA (Nassellaria loricata) | + +-----+-----+---------------------------------------------------------+ + | | 14. Spyroidea | + +-----+-----+------+-----+------+-----+-----+-----+-------------------+ + | 4 | 45 | 239 | 51 | 188 | 53 | C | A | 83-90 | + +-----+-----+------+-----+------+-----+-----+-----+-------------------+ + | | 15. Botryodea | + +-----+-----+------+-----+------+-----+-----+-----+-------------------+ + | 3 | 10 | 55 | 15 | 40 | 10 | E | C | 96 | + +-----+-----+------+-----+------+-----+-----+-----+-------------------+ + | | 16. Cyrtoidea | + +-----+-----+------+-----+------+-----+-----+-----+-------------------+ + | 12 | 160 | 1122 | 328 | 794 |250 | C | A | 51-80 | + +-----+-----+------+-----+------+-----+-----+-----+-------------------+ + | IV. Legion PHAEODARIA (Osculosa cannopylea) | + +-----+---------------------------------------------------------------+ + | | VII. PHAEOCYSTINA (Phaeodaria palliata) | + +-----+-----+---------------------------------------------------------+ + | | 17. Phaeocystina | + +-----+-----+------+-----+------+-----+-----+-----+-------------------+ + | 3 | 15 | 112 | 30 | 82 | 24 | C | B | 101-105 | + +-----+-----+------+-----+------+-----+-----+-----+-------------------+ + | | VIII. PHAEOCOSCINA (Phaeodaria loricata) | + +-----+-----+---------------------------------------------------------+ + | | 18. Phaeosphaeria | + +-----+-----+------+-----+------+-----+-----+-----+-------------------+ + | 4 | 22 | 121 | 5 | 116 | 0 | C | A | 106-112 | + +-----+-----+------+-----+------+-----+-----+-----+-------------------+ + | | 19. Phaeogromia | + +-----+-----+------+-----+------+-----+-----+-----+-------------------+ + | 5 | 27 | 159 | 5 | 154 | 0 | C | A | { 99, 100 | + | | | | | | | | | { 113-120 | + +-----+-----+------+-----+------+-----+-----+-----+-------------------+ + | | 20. Phaeoconchia | + +-----+-----+------+-----+------+-----+-----+-----+-------------------+ + | 3 | 20 | 73 | 4 | 69 | 0 | D | B | 121-128 | + +-----+-----+------+-----+------+-----+-----+-----+-------------------+ + | Total, | + +-----+-----+------+-----+------+-----+-----+-----+-------------------+ + | 85 | 739 | 4318 | 810 | 3508 | 558 | ... | ... | 140 | + +-----+-----+------+-----+------+-----+-----+-----+-------------------+ + +_Note._--In the tenth and eleventh columns the relative abundance of each +order at or near the surface and near the bottom is approximately indicated +by the letters A-E, which have the following significance:--A, abundant; B, +very numerous; C, many (medium quantity); D, few; E, very few. + + + + +{1}SYSTEMATIC PART. + +---- + +CLASS RADIOLARIA. + + RADIOLARIA, Johannes Mueller, 1858. + RHIZOPODA RADIARIA, Johannes Mueller, 1858. + POLYCYSTINA (_pro parte_), Ehrenberg, 1838. + ECHINOCYSTIDA, Claparede, 1858. + RHIZOPODA CAPSULARIA, Haeckel, 1861. + CYTOPHORA, Haeckel, 1862. + +_Definition of the Class:_--#Rhizopoda with unicellular body, divided by a +porous membrane into an internal or intracapsular part (with nucleus), and +an external or extracapsular part (with calymma); propagating by +flagellated spores.# + + +The RADIOLARIA or CAPSULATE RHIZOPODA, first constituted by Johannes +Mueller in the year 1858 as a separate group of the Rhizopoda, form a +peculiar class of the PROTISTA, or unicellular organisms. This class is +exclusively marine, and has in general the characteristic organisation of +the Rhizopoda, with the development of numerous _pseudopodia_ from the +surface of the cell; but it differs from all other Rhizopoda in the +possession of a peculiar _membrane_, dividing the cell-body into two +different parts; the _central capsule_ or the internal part with the +_nucleus_, and the external part or _extracapsulum_ with the _calymma_; +propagation by flagellated spores produced in the central capsule; the +sarcode or the _protoplasm_ of both parts communicates by fine _pores_, +piercing the separating membrane, which is called the _capsule-membrane_. + +The _Central Capsule_ or the inner part of the Radiolarian body is +constantly composed of three essential parts, viz.:-- + + 1. _The Central Nucleus_ (a true cell-nucleus). + + 2. _The Intracapsular Sarcode_ (endosarc) or surrounding internal + protoplasm. + + 3. _The Capsule Membrane_ or enveloping porous membrane. + +{2}Besides these constant and essential elements, the central capsule +contains very commonly (but not constantly) some other enclosed structures, +viz.:-- + + 4. An internal or intracapsular skeleton. + + 5. Intracapsular vacuoles or alveoli. + + 6. Fat-granules or oil-globules. + + 7. Crystals of different composition. + + 8. Pigment-granules. + +_The Extracapsulum_, or the outer part of the Radiolarian body is also +constantly composed of three essential elements,-- + + 1. _The Calymma_, or the thick extracapsular _jelly-veil_, completely + enveloping the whole central capsule. + + 2. _The Matrix_, or the maternal tissue of the external protoplasm, + enveloping immediately the capsule-membrane as a thin continuous layer of + _extracapsular sarcode_ (ectosarc). + + 3. _The Pseudopodia_, or the very numerous thread-like filaments of + protoplasm, which radiate from the matrix; whilst their inner part is + enclosed in the calymma, their outer part floats freely in the sea-water. + +Besides these three constant and essential elements, the extracapsulum +contains very commonly (but not constantly) some other enclosed structures, +viz.:-- + + 4. An external or extracapsular skeleton. + + 5. Extracapsular vacuoles or alveoli. + + 6. Fat-granules or oil-globules. + + 7. Pigment-granules or a peculiar large body of dark extracapsular + pigment, the "phaeodium." + + 8. "Xanthellae" or "zooxanthellae," peculiar yellow cells, which contain + starch and are unicellular yellow Algae, living as "Symbiontes" in true + Symbiosis with a great many Radiolaria. + +_The Nucleus_ of the Radiolaria is a large true simple cell-nucleus, +originally a solid spherical, roundish or longish body of nuclein. It is +placed either in the centre of the capsule (in most Peripylea) or +excentrically (in most other Radiolaria). Originally solid, the nucleus is +commonly differentiated later into an outer dense nuclear-membrane and an +inner softer or fluid content; either with one single nucleolus or with a +variable number of nucleoli. Originally always simple, the nucleus becomes +afterwards constantly divided into numerous small nuclei, each of which, +together with a part of the surrounding {3}protoplasm, forms a +vibratile-spore or "flagellate-spore." This division in the Acantharia and +in the social (or colonial) Peripylea begins very early, in all other +Radiolaria much later, immediately before propagation. + +_The Endoplasm_ or "endosarc," or "intracapsular protoplasm" or "inner +sarcode," in all Radiolaria originally fills that space within the capsule, +which is not taken up by the nucleus. It seems to be employed mainly for +the purpose of propagation, becoming divided earlier or later into numerous +small particles, each of which surrounds a small particle of the nucleus +and forms together with it a flagellate-spore. Besides this the endoplasm +of the Radiolaria seems to have a great significance for the nutrition, +mainly for the interchange of materials. It becomes very often vacuolate or +alveolate, filled with smaller or larger spherical drops of fluid; it +produces very commonly smaller fat-granules or larger oil-globules, and +further pigment-granules of different colours, more rarely crystals and +other peculiar enclosed parts. + +_The Membrane_ or "capsule-membrane" is the most typical and characteristic +part of the body of a Radiolarian, sufficient of itself to separate this +class from all other Rhizopoda. At the same time, by its different shape it +presents the best means for the systematic distinction of the four +subclasses or "legions" of the class. The membrane is composed of a special +organic matter (probably nearly related to chitin) and combines density +with elasticity to a high degree. Observed with a high power of the +microscope its margin (or section) appears commonly simple-edged, but often +in larger forms distinctly double-edged. + +The legion PHAEODARIA is distinguished by a double membrane (the thinner +inner and thicker outer membranes being separated by an interval); in the +three other legions it is simple. The membrane completely separates the +intracapsular from the extracapsular body, both communicating only by +certain pores or openings in the membrane. With reference to this important +communication, the whole class can be divided into two subclasses, +Holotrypasta and Merotrypasta: the HOLOTRYPASTA contain the Peripylea and +Actipylea, in which the membrane is pierced by innumerable very small +pores; the MEROTRYPASTA consist of the Monopylea and the Cannopylea, in +which the membrane exhibits only one large main opening, distinguished in +the former by a peculiar "porous area," in the latter by an "osculum" or a +prolonged tubule. + +_The Calymma_ or "jelly-veil" is the most characteristic part of the +extracapsular body in all Radiolaria; in the majority of the class it is +the most voluminous part of the whole body, being much more voluminous than +all the other parts taken together. The calymma is a structureless, clear, +and transparent jelly-envelope which always includes the whole central +capsule and often also the whole extracapsular skeleton. Owing to the high +degree of its consistence, this jelly-veil takes a very important part in +the formation of the extracapsular skeleton, furnishing the matrix for the +deposition of its tangential parts. + +{4}_The Matrix_ or the "maternal tissue of the pseudopodia" is formed in +all Radiolaria by the thin layer of exoplasm or of extracapsular sarcode, +which immediately envelops the central capsule and is itself enclosed by +the calymma. This continuous sarcode-cover of the capsule communicates by +its pores or openings with the endoplasm or the intracapsular sarcode; +whilst from its outer surface arise the pseudopodia. The morphological +signification of the matrix is very small, but the physiological importance +is very great, for it seems to be the chief organ of many vital functions. + +_The Pseudopodia_ or the very fine, long, thread-like filaments of exoplasm +arise in all Radiolaria in very great numbers from the surface of the +matrix, and exhibit in general the same characteristic shape as in the +other Rhizopoda. Their inner or proximal part is enclosed within the +jelly-veil or calymma, whilst their outer or distal part floats freely in +the sea-water. Their special motions and modifications exhibit considerable +variations in different groups, their tendency to ramify, anastomose, and +form networks being in some cases very small, in others very great. Also +the characteristic motion of granules in the pseudopodia is very different. +In general those most important exoplasmatic filaments serve as organs both +for the vegetative functions of nutrition, and for the animal functions of +motion and sensation. + +_The class_ Radiolaria can be divided according to its varying structure +into four different legions or subclasses, the characters of which are the +following:-- + + +I. PERIPYLEA OR SPUMELLARIA. + + Membrane of the central capsule simple, perforated by innumerable very + fine pores. Fundamental form originally homaxon or spherical. Skeleton + wanting or siliceous. No phaeodium in the extracapsular calymma. The + Peripylea comprise two orders:-- + + A. COLLODARIA (without lattice-shell). + B. SPHAERELLARIA (with lattice-shell). + +II. ACTIPYLEA OR ACANTHARIA. + + Membrane of the central capsule simple, perforated by innumerable fine + pores. Fundamental form originally homaxon or spherical. Skeleton + acanthinic (not siliceous). No phaeodium in the extracapsular calymma. + The Actipylea consist of two orders:-- + + A. ACANTHOMETRA (without complete lattice-shell). + B. ACANTHOPHRACTA (with complete lattice-shell). + + +{5}III. MONOPYLEA OR NASSELLARIA. + + Membrane of the central capsule simple, perforated by a porous-area, or + by one single large opening, divided into numerous very fine pores. + Fundamental form originally monaxon or egg-shaped. Skeleton siliceous. No + phaeodium in the extracapsular calymma. The Monopylea comprise two + orders:-- + + A. PLECTELLARIA (without complete lattice-shell). + B. CYRTELLARIA (with complete lattice-shell). + +IV. CANNOPYLEA OR PHAEODARIA. + + Membrane of the central capsule double, perforated by one simple + main-opening, prolonged into a tubulus, and besides this commonly by one + or two (rarely more) small accessory openings. Fundamental form + originally monaxon or egg-shaped. Skeleton siliceous. Constantly a + peculiar dark pigment-body or "phaeodium" in the extracapsular calymma. + The Cannopylea comprise two orders:-- + + A. PHAEOCYSTINA (without lattice-shell). + B. PHAEOCOSCINA (with lattice-shell). + +_Synopsis of the four Subclasses or Legions of Radiolaria._ + + -------------------------------+----------------------------------- + A. HOLOTRYPASTA. | B. MEROTRYPASTA. + | + Central capsule everywhere | Central capsule with one large + perforated by innumerable | main-opening (with or without + small pores. | small accessory openings). + | + Fundamental form originally | Fundamental form originally + homaxon (spherical or | monaxon (egg-shaped or + derived from a sphere). | perhaps dipleural). + --------------+----------------+-----------------+----------------- + I. | II. | III. | IV. + | | | + SPUMELLARIA. | ACANTHARIA. | NASSELLARIA. | PHAEODARIA. + (_Peripylea._)| (_Actipylea._) | (_Monopylea._) | (_Cannopylea._) + | | | + Wall-pores of | Wall-pores of | Main-opening of | Main-opening of + the capsule | the capsule | the capsule | the capsule + equally | symmetrically | with a porous | with a short + disposed. | disposed. | operculum. | tubule. + | | | + Skeleton | Skeleton | Skeleton | Skeleton + siliceous | acanthinic | siliceous | siliceous + or wanting. | (organic). | (rarely | (rarely + | | wanting). | wanting). + | | | + Calymma | Calymma | Calymma | Calymma + without | without | without | constantly + phaeodium. | phaeodium. | phaeodium. | with a + | | | phaeodium. + --------------+----------------+-----------------+----------------- + + + +{6}LEGION I. #SPUMELLARIA#, + +VEL PERIPYLEA, VEL PERIPYLARIA (PLS. 1-50). + + _Spumellaria_ (_exclusis_ Spyridinis), Ehrenberg, 1875. + _Peripylea_ (_inclusis_ Thalassicollis et Sphaerozois), Hertwig, 1879. + _Peripylaria_ (_inclusis_ Collodariis et Polycyttariis), Haeckel, 1881. + +_Definition._--Radiolaria with simple membrane of the central capsule, +which is everywhere perforated by innumerable very fine pores. +Extracapsulum without phaeodium. Skeleton wanting or siliceous. Fundamental +form originally spherical. + +The legion SPUMELLARIA vel PERIPYLEA, in the extent here defined, was +constituted by me in 1883 in my paper on Die Ordnungen der Radiolarien.[2] +I propose to retain for this legion either the name SPUMELLARIA of +Ehrenberg (1875) or PERIPYLEA of Hertwig (1879), although both groups have +not quite the same extension. We exclude from the SPUMELLARIA the Spyridina +(united with them by Ehrenberg) and include the Collodaria. With the +Peripylea of Hertwig we unite his Thalassicollea and Sphaerozoea. To avoid +any confusion it would perhaps be better to name this legion "Peripylaria." + +The SPUMELLARIA agree with the ACANTHARIA in the structure of the simple +capsule-membrane, which is perforated by numerous small pores (but devoid +of the large main opening, which the NASSELLARIA and PHAEODARIA possess), +whence we unite both the former as Holotrypasta, both the latter as +Merotrypasta. + +The difference between the two legions of Holotrypasta is determined by the +skeleton, which in the SPUMELLARIA is either siliceous or wanting, whilst +in the Acantharia it consists of the peculiar organic substance, acanthin. + +The legion SPUMELLARIA is by far the largest and most important of the four +legions of Radiolaria, as well with respect to the number of different +forms, as to the enormous masses of individuals, which we encounter living +and fossil. We distinguish in this legion not less than thirty-two +different families, three hundred and sixteen genera, and more than +seventeen hundred species. + +The classification of this large group requires for its better +comprehension a careful division into larger and smaller groups. We divide +it therefore first of all into two orders, #Collodaria# and +#Sphaerellaria#, as proposed in the paper mentioned above.[3] + +The #Collodaria# have no perfect latticed skeleton, and comprise two +suborders or sections: in the #Colloidea# the skeleton is entirely wanting, +in the #Beloidea# it is represented by a variable number of siliceous +needles or spicules, scattered in the calymma around the central capsule. + +{7}The #Sphaerellaria# differ from the #Collodaria# in the possession of a +perfect siliceous skeleton, which is originally a latticed spherical shell, +enveloping the central capsule. By modification of this fenestrated sphere +arises an enormous mass of different forms, which we dispose in +twenty-eight families, and these in four larger groups, suborders or +sections,--#Sphaeroidea#, #Prunoidea#, #Discoidea#, and #Larcoidea#. + +The #Sphaeroidea#, the common ancestral group of the #Sphaerellaria#, +possess a skeleton which is either a simple fenestrated sphere, or composed +of two or more concentric latticed spheres, which are united by radial +beams; more rarely it becomes more or less spongy. + +The #Prunoidea# are derived from the #Sphaeroidea# by prolongation of the +latticed sphere in one axis; the skeleton therefore becomes here +ellipsoidal or cylindrical (often with annular transversal constrictions). + +The #Discoidea# on the contrary must be derived from the #Sphaeroidea# by +shortening in one axis; here therefore the fenestrated shell becomes more +or less lenticular or iscoidal (often with radial spines or arms in the +equatorial plane, on the circular margin). + +The #Larcoidea#, the fourth section, differ from the three foregoing +sections by the different growth of the shell in three different dimensions +of space; therefore here the fenestrated shell becomes "lentelliptical," or +a "triaxial ellipsoid," its length, breadth, and height being different. + + + + +_The Skeleton_ consists in all SPUMELLARIA either of pure _silica_ or of a +peculiar silicate. The siliceous bars and beams constituting it are +invariably _solid_, as also in the NASSELLARIA, never hollow, as in the +PHAEODARIA. Never is the skeleton composed of acanthin, as in all +ACANTHARIA. Whilst in the first order of SPUMELLARIA, #Collodaria#, the +form of the spicula, or the scattered needles, composing the skeleton, is +very simple, _never latticed_, in the second order, the #Sphaerellaria#, it +is constantly latticed or fenestrated, often also spongy. + +The geometrical fundamental form of the lattice-shell in the +#Sphaerellaria# is originally spherical (homaxon), as preserved in all +#Sphaeroidea#; in the #Prunoidea# and #Discoidea# it becomes monaxon, with +one single axis (prolonged in the former, shortened in the latter); in the +#Larcoidea# it becomes triaxon, by different growth in three principal +axes, perpendicular one to another. The further development of radial parts +of the skeleton in these three axes is very important for the +"promorphology" of the Radiolaria. + +_The Malacoma_, or the whole soft body of the SPUMELLARIA as opposed to the +skeleton, exhibits some differences of structure in two different groups, +which were separated formerly (1862) as Monocyttaria and Polycyttaria, +corresponding to the "Radiolaria monozoa and polyzoa" of Johannes Mueller +(1858). + +The #Monocyttaria# (or the Spumellaria solitaria) live isolated as single +cells--like {8}all other Radiolaria--and are never aggregated in colonies; +the calymma includes one single central capsule, and this again one central +nucleus, which does not become divided until full maturity. + +The #Polycyttaria# on the contrary (or the Spumellaria socialia) live +aggregated in large colonies; the calymma includes a variable number of +associated central capsules and each of these commonly one central +oil-globule, whilst the original simple nucleus commonly becomes very early +divided into numerous small nuclei. + +_The Nucleus_ of the SPUMELLARIA is originally constantly _central_, placed +quite in the centre of the concentric capsule, and it retains this central +position in all Monocyttaria or solitary Peripylea; whereas in the +Polycyttaria--in consequence of its early division--its place is commonly +taken by a central oil-globule. Whilst the numerous nuclei of the latter +are very small, the single nucleus of the former is comparatively large, +extremely large (more than a millimeter in diameter) in some gigantic +#Collodaria#. + +_The Endoplasm_ or the intracapsular sarcode exhibits in the greater number +of SPUMELLARIA a more or less distinct radial striation. It encloses a +great variety of different parts; vacuoles, oil-globules, pigment-granules, +crystals, &c. + +_The Membrane_ of the capsule in all SPUMELLARIA is simple (never double as +in the _Phaeodaria_) and everywhere equally perforated by innumerable small +pores; in the thick, double-edged membrane of many large #Collodaria# these +pores appear (in the optical section of the capsule-wall) as distinct fine +radial canals, very densely and regularly disposed. + +_The Central Capsule_ in the SPUMELLARIA is originally a _geometrical +sphere_, and this simple globular form is preserved in all #Sphaeroidea#, +and in the greatest part of #Colloidea# and #Beloidea#. By prolongation of +one axis the form becomes _ellipsoidal_ (or even cylindrical) in the +#Prunoidea#, and in some few forms of #Colloidea#. By shortening of one +axis it becomes _lenticular_ (or even discoidal) in the _Discoidea_, and in +some few forms of #Colloidea#. By unequal growth in three different axes, +perpendicular one to another, the capsule becomes _lentelliptical_ in all +#Larcoidea#. Very rarely the capsule assumes in the SPUMELLARIA a +polyhedral or irregular (sometimes even amoeboid) form, only in a few +#Colloidea#. + +_The Calymma_, or the jelly-veil including the central capsule, is very +voluminous in many SPUMELLARIA of gigantic size, mainly in the large +#Colloidea#, and in all Polycyttaria or social Radiolaria. It includes here +a considerable number of large vacuoles or "alveoli." The calymma never +exhibits in this legion the dark voluminous phaeodium, possessed by all +PHAEODARIA. + +_Xanthellae_ or "zooxanthellae" are numerous in the calymma of most +SPUMELLARIA, but by no means constant; they are very variable in number and +size. + +_The Matrix_, placed between the calymma and central capsule, is, in the +majority of the SPUMELLARIA, a rather thick layer of granular exoplasm. + +_The Pseudopodia_ arising from it are very numerous, equally disposed over +the whole {9}surface, and are in general rather fluid, exhibiting a +considerable tendency to ramify, anastomose, and form networks. The +movement of granules is commonly lively. In the Polycyttaria all capsules +of one colony or "coenobium" are connected by the dense variable network of +anastomosing pseudopodia. + +_Synopsis of the Orders and Suborders of_ SPUMELLARIA. + + I. COLLODARIA. { Skeleton entirely wanting, 1. #Colloidea.# + Skeleton wanting or { + quite imperfect, { Skeleton represented by + not latticed. { numerous scattered spicules, 2. #Beloidea.# + + II. SPHAERELLARIA. { Lattice-shell spherical or + { composed of concentric spheres, 3. #Sphaeroidea.# + Skeleton a perfect { + shell of lattice { Lattice-shell ellipsoidal or + work, or spongy and { prolonged in one axis, 4. #Prunoidea.# + resembling { + wicker-work. { Lattice-shell discoidal or + { shortened in one axis, 5. #Discoidea.# + { + { Lattice-shell lentelliptical, + { with different extent of growth + { in three axes, 6. #Larcoidea.# + + +---- + + +Order I. COLLODARIA, Haeckel, 1881. + + _Collodaria_, Haeckel, Prodromus, 1881, p. 469. + _Collida_ et _Sphaerozoida_, Haeckel, 1862, Monogr. d. Radiol., pp. 246, + 522. + +_Definition._--SPUMELLARIA without latticed shell. + +The order #Collodaria#, the first order of Radiolaria, comprises all those +SPUMELLARIA in which the skeleton is either entirely wanting, or +represented by numerous single, solid, siliceous needles or spicules, +loosely scattered in the calymma around the central capsule. Never in this +order is there any trace of the latticed or fenestrated shell, which +characterises the second order, #Sphaerellaria#. The skeleton exhibits no +trace of phylogenetic connection in the two orders. + +In my monograph (1862) two families appertaining to this order are +described, the Collida (p. 244) and the Sphaerozoida (p. 521). Both +families contain forms with and without a skeleton. Of the solitary or +monozous Collida the Thalassicollida are devoid of a skeleton, whilst the +Thalassosphaerida are provided with a skeleton. Of the social or polyzous +Sphaerozoida the Collozoida are without a skeleton, the Rhaphidozoida +provided with one. As the special form in both skeletophorous subfamilies +is exactly the same, I prefer now to associate them in the suborder +#Beloidea#, and to oppose them to the other two skeletonless subfamilies, +which are united under the name of #Colloidea#. + +{10}_Synopsis of the four Families of Collodaria._ + + Suborder I. { Solitary cells, living + COLLOIDEA. { as isolated individuals + { (_Colloidea monozoa_), 1. THALASSICOLLIDA. + Skeleton entirely { + wanting. { Associated cells, living + { in colonies or coenobia + { (_Colloidea polyzoa_), 2. COLLOZOIDA. + + Suborder II. { Solitary cells, living as + BELOIDEA. { isolated individuals + { (_Beloidea monozoa_), 3. THALASSOSPHAERIDA. + Skeleton composed { + of numerous { Associated cells, living in + needles or { colonies or coenobia + spicula, scattered { (_Beloidea polyzoa_), 4. SPHAEROZOIDA. + in the calymma. { + + +---- + + +Suborder I. COLLOIDEA, Haeckel. + +_Definition._--SPUMELLARIA without skeleton. + +The suborder #Colloidea# comprises all those SPUMELLARIA in which no +skeleton is developed. The whole body is therefore soft--a true +malacoma--and is composed only of two essential parts, the central capsule +and the enveloping extracapsulum. The suborder contains only two different +families, the solitary #Thalassicollida# (or Colloidea monozoa) and the +associated #Collozoida# (or Colloidea polyzoa). Both families are very +nearly allied, and differ only in one single essential character: the +solitary life of the former, the social union of the latter. It seems to be +merely in consequence of this difference that the cleavage of the nucleus +commonly takes place very late in the former, very early in the latter. + +Therefore the full-grown Thalassicollida (till immediately before +propagation) commonly exhibit one single nucleus in the centre of the +capsule, whilst in the Collozoida the capsule is distended by numerous +small nuclei. In these latter the centre of the capsule usually contains +one large oil-globule, whilst in the former oil-globules are either +wanting, or scattered in large numbers in the endoplasm, or disposed in one +layer on the inside of the capsule membrane. + +In the solitary Thalassicollida each capsule is enclosed in its own +peculiar spherical calymma, whilst in the associated Collozoida all +capsules of the colony are united in one common, very voluminous calymma. + + + +Family I. #THALASSICOLLIDA#, Haeckel, 1862. + + _Thalassicollida_, Haeckel, 1862, Monogr. d. Radiol., p. 246. + _Thalassicollida_, Haeckel, 1881, Prodromus, p. 469. + +_Definition._--#Colloidea# solitaria. + +The family Thalassicollida comprises all solitary SPUMELLARIA without a +skeleton. The oldest and best known form of this family is the genus +_Thalassicolla_, as restricted by {11}Johannes Mueller.[4] The most common +representative of it, the cosmopolitan _Thalassicolla nucleata_, was first +described by Huxley in 1851. But as early as 1834 another large +Radiolarian, appertaining either to this or to a nearly allied family, had +been described by Meyen as _Physematium atlanticum_. A third genus was +detected by me in 1859 at Messina and figured under the name _Thalassolampe +margarodes_.[5] A very accurate histological description of these forms was +given in 1876 by Richard Hertwig.[6] The same author figured in his +Organismus in 1879 a very interesting simpler form under the name +_Thalassolampe primordialis_ (Taf. iii. fig. 5). Some similar forms had +already been observed by me, and are here united with it to form the first +genus _Actissa_.[7] + +_Actissa_ is of the highest general interest as the most simple and typical +form of all Radiolaria, and as the common ancestral form, from which all +other forms of this large class may be derived. Its unicellular body +exhibits neither the extracapsular alveoli of _Thalassicolla_, nor the +intracapsular alveoli of _Thalassolampe_, and shows all essential +characters of the Radiolarian type in its most simple form (Pl. 1, figs. 1 +to 1_c_). The simple cell-body is composed of a spherical central capsule +and a concentric, spherical, enveloping calymma, both separated by a thin +membrane which is perforated by innumerable pores. The capsule includes the +endoplasm and in the centre a simple spherical nucleus with nucleolus; at +the time of propagation this latter becomes cleft into numerous small +nuclei, each of which, together with a small piece of the surrounding +endoplasm, forms a flagellated zoospore (fig. 1_c_). The extracapsulum is +formed by the large, structureless, spherical calymma or concentric +jelly-veil enveloping the capsule, and by the thin granular matrix or the +layer of exoplasm which separates the calymma from the membrane. From this +matrix or maternal tissue arise innumerable very long and thin pseudopodia, +as simple radiating filaments, the proximal part of which is included in +the calymma, whilst the distal part floats freely in the sea-water (Pl. 1, +fig. 1). + +The other Thalassicollida differ from their common ancestral form, +_Actissa_, mainly by the higher histological differentiation of the +unicellular body. Whilst in _Thalassicolla_ and _Thalassolampe_ the nucleus +remains a single sphere as in _Actissa_, it becomes branched or covered +with radial blind saccules in _Thalassopila_ and _Thalassophysa_; also the +intracapsular protoplasm develops here a great variety of peculiar +different corpuscles, as oil-globules, pigment-granules, concentric +concretions, crystals, &c. But the most striking peculiarity by which the +other Thalassicollida differ from _Actissa_ is the development of large +vesicular alveoli, either within or without the capsule; the unicellular +body reaches by this inflation the extraordinary size of 5 to 10 mm. or +more. + +{12}_Synopsis of the Genera of Thalassicollida._ + + A. Alveoli neither { Nucleus spherical + within nor without { (sometimes ellipsoidal), + the central capsule. { not branched, 1. _Actissa_. + + B. Numerous large { Nucleus spherical, 2. _Thalassolampe_. + alveoli within the { + central capsule (not { Nucleus branched or + in the calymma). { covered with radial + { sacs, 3. _Thalassopila_. + + C. Numerous large { Nucleus spherical, 4. _Thalassicolla_. + alveoli without the { + central capsule, { Nucleus branched, or + within the jelly-veil { covered with radial + or calymma. { sacs, 5. _Thalassophysa_. + + + +Genus 1. _Actissa_,[8] n. gen. + +_Definition._--#Thalassicollida# with simple spherical nucleus, without any +alveoli (either within or outside the central capsule). + +The genus _Actissa_ is the most simple and typical form of all Radiolaria, +and may be regarded as the common ancestral form of the whole class. The +spherical body is composed of a simple spherical capsule and a concentric +spherical calymma or jelly-envelope. Neither the former nor the latter +contains alveoli. The central capsule possesses a strong membrane +perforated by small pores, and contains in the intracapsular sarcode +numerous small pellucid vacuoles, and in its middle a simple, concentric, +spherical nucleus (often with some nucleoli); sometimes also one or more +oil-globules. The extracapsularium forms a soft, voluminous, structureless +calymma or enveloping jelly-sphere, perforated by the numberless, fine +pseudopodia, which radiate outwards from the matrix or the thin granulated +sarcode-layer, surrounding the capsule. Often (but not constantly) +xanthellae or yellow cells are scattered in it. _Actissa_ differs from the +following skeletonless genera in the absence of all alveoli; it has neither +intracapsular alveoli (like _Thalassolampe_) nor extracapsular alveoli +(like _Thalassicolla_). The first observed species of this genus is that +which I found in 1866 at the Canary Islands, _Actissa prototypus_; the +second is that which Hertwig accurately described in 1879, from the +Mediterranean (Messina), _Actissa primordialis_; the third I observed in +1881 at Ceylon, frequent and sporiparous, _Actissa princeps_. A fourth +species (_Actissa radiata_) exhibited a distinct radial segmentation of the +capsule-contents. These four species are quite spherical. Six other +species, occurring in different preparations from the Challenger, are +distinguished by modifications of the spherical capsule-form and may +represent three different subgenera (or, perhaps better, +genera?)--_Actiprunum_ ellipsoidal, _Actidiscus_ lenticular, _Actilarcus_ +lentelliptical; perhaps these are the ancestral forms of the three +sections: #Prunoidea#, #Discoidea#, #Larcoidea#. + + + +{13}Subgenus 1. _Procyttarium_, Haeckel, 1879. + + _Procyttarium_, Haeckel, Natuerl. Schoepfungsgeschichte, ed. vii. p. 705. + +_Definition._--Central capsule spherical. + + +1. _Actissa princeps_, n. sp. (Pl. 1, fig. 1). + +Central capsule spherical, colourless or a little reddish, transparent, +with a thick double-edged membrane. Nucleus central, spherical, one-third +as broad as the central capsule, containing a single, central, glossy +nucleolus. Protoplasm finely granulated, without oil-globules, with +numerous clear spherical vacuoles of equal size and at equal distances; the +superficial layer of protoplasm (immediately below the membrane) radially +striated (fig. 1). In some older specimens the nucleus was divided into +numerous small nuclei (fig. 1_a_), which by further division gave the +nuclei of the flagellated spores (fig. 1_b_); each spore with a very thin +lateral flagellum (fig. 1_c_). Jelly-like calymma twice as broad as the +enclosed capsule, without xanthellae or yellow cells, pierced by +innumerable, very thin and long, undivided pseudopodia, which arise from +the sarcode-matrix on the outside of the membrane (six to eight times +longer than shown in fig. 1). + +_Dimensions._--Diameter of the central capsule 0.1 to 0.12, of the nucleus +0.03 to 0.04, of the jelly calymma 0.2 to 0.3. + +_Habitat._--Indian Ocean, Ceylon, Belligemma, Haeckel, 1881; also in a +preparation from Station 271, Central Pacific, surface. + + +2. _Actissa primordialis_, Haeckel. + + _Thalassolampe primordialis_, R. Hertwig, 1879, Organismus der + Radiolarien, p. 32, Taf. iii. fig. 5. + + _Procyttarium primordiale_, Haeckel, 1879, Natuerl. Schoepf., ed. vii. p. + 705, Taf. xvi. fig. 1. + +Central capsule spherical, dim-yellowish, with a thin, simple-edged but +compact membrane. Nucleus large, central (about half as broad), with one or +two dark nucleoli; on its side an excentric oil-globule, nearly of the same +size. Protoplasm between nucleus and membrane, in the younger specimens +finely granulated and radially striped; in the older specimens with +numerous hyaline globules (vacuoles). Jelly-envelope or calymma very +voluminous, ten to twelve times as broad as the central capsule, +structureless, containing numerous yellow bodies (xanthellae?), pierced by +very numerous simple pseudopodia. + +_Dimensions._--Diameter of the central capsule 0.11 to 0.18, of the nucleus +0.04 to 0.09, of the jelly-like calymma 1.2 to 1.5. + +_Habitat._--Mediterranean, Messina, Hertwig, 1878, surface. + + +3. _Actissa prototypus_, n. sp. + +Central capsule spherical, red-coloured, with a thick, double-edged +membrane. Nucleus central, spherical, half as large as the radius of the +capsule, containing a large number (forty to sixty) of small {14}dark +nucleoli. Protoplasm filled up with numerous small clear vacuoles, and +between them fine red pigment granules; on the inside of the membrane one +layer of dark oil-globules. Jelly-like calymma four times as broad as the +enclosed capsule, with very numerous small xanthellae. + +_Dimensions._--Diameter of the capsule 0.2, of the nucleus 0.05, of the +calymma 0.8. + +_Habitat._--Atlantic, Canary Islands (Lanzerote, Haeckel), 1866; also at +Station 348, surface. + + +4. _Actissa radiata_, n. sp. + +Central capsule spherical, dark, with a thick, double-edged membrane. +Nucleus central, spherical, half as large as the capsule, transparent. +Protoplasm divided into numerous cuneiform radial pieces which are +separated by clear intervals, and filled with very fine dark granules +(darker in the distal half). The equatorial optical section exhibits around +the circular clear nucleus a coronal of twenty-five such wedge-shaped +pieces (mother-cells of spores?) No oil-globules in the central capsule. +Jelly-like calymma one and a half times as broad as the enclosed capsule, +with numerous small xanthellae. + +_Dimensions._--Diameter of the capsule 0.15, of the nucleus 0.07, of the +calymma 0.24. + +_Habitat._--North Pacific, Station 241, surface. + + + +Subgenus 2. _Actiprunum_, Haeckel, 1882. + +_Definition._--Central capsule ellipsoidal, with one prolonged axis. + + +5. _Actissa prunoides_, n. sp. + + _Actiprunum prunoideum_, Haeckel, 1882, Manuscript. + +Central capsule ellipsoidal, colourless, with a thin, simple-edged +membrane. Proportion of its major axis to the minor 4 : 3. Nucleus +spherical, its diameter equal to one-third of the minor axis, in its centre +a large, dark, spherical nucleolus. Protoplasm clear, containing numerous +small vacuoles, separated by regular distances, and on the inside of the +capsule-membrane, numerous (forty to fifty) small oil-globules. Calymma (or +jelly-veil) ellipsoidal, with a thin sarcode-stratum on the outside of the +capsule; its diameter twice as large as that of the central capsule. + +_Dimensions._--Major axis of the capsule 0.16, minor 0.12; diameter of the +nucleus 0.04; major axis of the calymma 0.32, minor 0.24. + +_Habitat._--Central Pacific, Station 274, surface. + + +6. _Actissa ellipsoides_, n. sp. + + _Actiprunum ellipsoides_, Haeckel, 1882, Manuscript. + +Central capsule ellipsoidal, red-coloured, with a thick, double-edged +membrane. Proportion of its major axis to the minor 5 : 3. Nucleus +ellipsoidal, one-third as large as the capsule, containing eight small dark +nucleoli. Protoplasm dusky, filled with dark pink pigment-granules; in the +{15}major axis, on both poles of the nucleus-axis, two large oil-globules, +half as large as the nucleus. Calymma ellipsoidal, with numerous +xanthellae; its diameter four times as large as that of the capsule. + +_Dimensions._--Major axis of the capsule 0.2, minor 0.12; major axis of the +nucleus 0.07, minor 0.04; major axis of the calymma 0.8, minor 0.5. + +_Habitat._--Mediterranean, Corfu, 1877, Haeckel, surface. + + + +Subgenus 3. _Actidiscus_, Haeckel, 1882. + +_Definition._--Central capsule lenticular, with one shortened axis. + + +7. _Actissa discoides_, n. sp. + + _Actidiscus discoides_, Haeckel, 1882, Manuscript. + +Central capsule lenticular, red-coloured, about twice as broad as high, +with a thick, double-edged membrane. Nucleus spherical, one-third as broad +as the capsule, with one single, large central nucleolus. Protoplasm dusky, +filled with scarlet pigment; granules and small oil-globules between them. +Calymma lenticular, three times as broad as the capsule. + +_Dimensions._--Major axis of the capsule 0.16, minor 0.08; diameter of the +nucleus 0.05; breadth of the calymma 0.5. + +_Habitat._--North Pacific, Station 236, surface. + + +8. _Actissa lenticularis_, n. sp. + +Central capsule lenticular, flattened, about three times as broad as high, +with a thin, simple-edged membrane. Nucleus lenticular, one-third as large +as the capsule, with ten small dark nucleoli. Protoplasm transparent, +colourless, filled with small vacuoles at regular distances; on the inside +of the membrane in the circular periphery of the lens twenty dark +oil-globules. Calymma lenticular, twice as broad as the capsule. + +_Dimensions._--Major axis of the capsule 0.15, minor 0.05; breadth of the +nucleus 0.05, height 0.02; breadth of the calymma 0.03. + +_Habitat._--East Pacific, Station 272, surface. + + +9. _Actissa phacoides_, n. sp. + + _Actidiscus phacoides_, Haeckel, 1882, Manuscript. + +Central capsule lenticular, strongly flattened, about four times as broad +as high, with a thin, simple-edged membrane. Nucleus lenticular, one-fourth +as broad as the capsule, with numerous (twenty or more) small nucleoli. +Protoplasm filled with dark pigment-granules; on the inside of the membrane +in the circular periphery of the lens thirty-two dark oil-globules. Calymma +lenticular, three times as broad as the capsule. + +{16}_Dimensions._--Major axis of the capsule 0.2, minor 0.05; breadth of +the nucleus 0.05, height 0.015; breadth of the calymma 0.6. + +_Habitat._--Tropical Atlantic, Station 347, surface. + + + +Subgenus 4. _Actilarcus_, Haeckel. + +_Definition._--Central capsule lentelliptical, with three different axes. + + +10. _Actissa larcoides_, n. sp. + +Central capsule lentelliptical; with three different axes, bearing the +proportion 4 : 3 : 2. Nucleus spherical; its diameter equal to the shortest +radius of the capsule. No nucleoli visible. Protoplasm transparent, with +small vacuoles; on the inside of the thin capsule-membrane numerous (fifty +to sixty) small oil-globules, regularly disposed. Calymma lentelliptical, +twice as large as the central capsule. + +_Dimensions._--Major axis or length of the capsule 0.2, middle axis or +breadth 0.15, minor axis or height 0.1; diameter of the nucleus 0.05, of +the calymma 0.3-0.4. + +_Habitat._--Central Pacific, Station 266, surface. + + + +Genus 2. _Thalassolampe_,[9] Haeckel, 1862, Monogr. d. Radiol., p. 253. + +_Definition._--#Thalassicollida# without extracapsular alveoles, but with +large roundish or globular alveoles within the central capsule, with a +simple spherical, not branched nucleus in the centre. + +The genus _Thalassolampe_ is, next to _Actissa_, the most simple of all +Radiolaria, but differs from it by the large intracapsular alveoles. By +these the central capsule is inflated to an extraordinary size, which in +_Thalassolampe maxima_ exceeds that of most other Radiolaria. From the +nearly allied _Thalassopila_ it differs by the simple spherical nucleus, +from _Physematium_ by the absence of spicula. Of the two species of the +genus the first observed _Thalassolampe margarodes_, 1862, is +Mediterranean, the second, _Thalassolampe maxima_, 1882, is Indian. + + +1. _Thalassolampe margarodes_, Haeckel. + + _Thalassolampe margarodes_, Haeckel, 1862, Monogr. d. Radiol., p. 253, + Taf. ii. figs. 4, 5. + + _Thalassolampe margarodes_, R. Hertwig, 1876, Histologie d. Radiol., p. + 68, Taf. iii. figs. 1-5. + +Spherical body very soft and limpid, somewhat pearl-like opalescent, +yellowish or bluish. Central capsule with a very thin structureless +membrane, its diameter six to eight times as large as that of the central +spherical nucleus. Wall of the vesicular nucleus thick, perforated by fine +{17}pore-canals; on its inside often numerous oval nucleoli. In the movable +protoplasmic network between the large alveoles a considerable number of +large yellowish or orange oil-globules. Extracapsular jelly-envelope very +thin, contains small yellow bodies (zooxanthellae). (Compare the accurate +description of this Mediterranean species in my monograph and in Hertwig's +work.) In the Canary Islands I found very often a large variety of it, of +double and triple the size, distinguished by the delicate orange colour of +the intracapsular oil-globules. This may be distinguished as _Thalassolampe +aurantiaca_. + +_Dimensions._--Diameter of the whole jelly-sphere 2 to 4 mm., of the +central capsule 2 to 3 mm., of its nucleus 0.2 to 0.4 mm. + +_Habitat._--Mediterranean, Messina, Haeckel, Hertwig; Canary Islands, +Lanzerote, Haeckel; surface. + + +2. _Thalassolampe maxima_, n. sp. (Pl. 1, fig. 2). + +Spherical body quite pellucid, like a glass globule, colourless. Central +capsule with a moderately thick, but quite transparent, structureless +membrane, its diameter ten to twelve times as large as that of the central +spherical nucleus. Wall of the vesicular nucleus thick, perforated by fine +pore-canals; on its inside numerous small spherical nucleoli. No large +oil-globules in the movable protoplasmic network between the large +alveoles. Extracapsular jelly-envelope very thin, containing no yellow +bodies. This differs from the preceding nearly allied species in the want +of the intracapsular oil-globules and of the extracapsular yellow bodies. +It possesses the largest central capsule of all known Radiolaria. I found +them living and floating in water taken from the surface of the Indian +Ocean by a bucket. + +_Dimensions._--Diameter of the whole jelly-body 12 to 15 mm., of the +central capsule 10 to 12 mm., of the nucleus 0.8 to 1.2 mm. + +_Habitat._--Indian Ocean, near the Maldive Islands, Haeckel, 1882, surface. + + + +Genus 3. _Thalassopila_,[10] Haeckel, 1881, Prodromus, p. 469. + +_Definition._--Thalassicollida without extracapsular alveoles, but with +large roundish or globular alveoles within the central capsule, with a +papillate or branched nucleus in its centre. + +The genus _Thalassopila_ has, like _Thalassolampe_, a voluminous foamy +central capsule, inflated by numerous large alveoles; but it differs in the +complicated form of the nucleus, which is like that of _Thalassophysa_, and +is either branched or occupied by conical or roundish papillae. + + +1. _Thalassopila cladococcus_, n. sp. (Pl. 1, fig. 3). + +Spherical body dark-spotted, with a thin yellowish jelly-envelope. Central +capsule with a thick and firm membrane, perforated by pores; its diameter +three times that of the central nucleus, {18}three-fourths that of the +whole jelly-sphere. Nucleus profusely branched or papillated, its spherical +surface covered with numerous (more than a hundred) finger-shaped obtuse +blind sacs, about as long as its radius. Protoplasm of the central capsule +forming a loose network between the large roundish alveoles, in the +cortical zone radially striped and containing one layer of large dark +oil-globules. These are regularly distributed on the inside of the +capsule-membrane and separated by intervals, twice as broad as its +diameter, giving to the capsule-surface a spotted appearance. Extracapsular +jelly-envelope thin, yellowish, with very numerous and small xanthellae. + +_Dimensions._--Diameter of the whole jelly-sphere 5 mm., of the central +capsule 4 mm., of the nucleus 1.3 mm. + +_Habitat._--Antarctic Ocean, Station 154 (south of Kerguelen), surface. + + + +Genus 4. _Thalassicolla_,[11] Huxley, 1851, Ann. and Mag. Nat. Hist., ser. +2, vol. viii. p. 433. + +_Definition._--Thalassicollida without intracapsular alveoles, but with +large roundish or globular alveoles within the extracapsular calymma. +Nucleus in the centre of the capsule simple spherical, not branched. + +The genus _Thalassicolla_ was proposed by Huxley in 1851, for a certain +number of different voluminous jelly-like Radiolaria, which he had observed +living during his voyage in the "Rattlesnake" through the tropical seas, +and of which he gives an excellent description--the first accurate +observations on living Radiolaria. Johannes Mueller afterwards removed from +this genus the social genera _Sphaerozoum_ and _Collosphaera_ (formerly +_Thalassicolla punctata_), and retained as type of the genus _Thalassicolla +nucleata_. In 1862 in my Monograph I added two other species, +_Thalassicolla pelagica_ and _Thalassicolla zanclea_, and later (1870) +_Thalassicolla sanguinolenta_. Now I think it better to separate the last +two species as a new genus, _Thalassophysa_, characterised by the papillate +or branched nucleus, and to retain in _Thalassicolla_ only those forms with +simple spherical nucleus. For both genera the extracapsular, voluminous, +spherical calymma or jelly-envelope, with numerous large alveoles, is +characteristic. The membrane of the central capsule in _Thalassicolla_ is +now structureless (subgenus _Thalassicollarium_, with three species), now +characterised by a peculiar structure, prominent ridges on the inside of +the membrane, which form a network with polygonal plates, resembling an +epithelium (Pl. 1, fig. 5_b_; subgenus _Thalassicollidium_, with four +species). Of the seven species here described, two are cosmopolitan, widely +distributed, and common; one is Mediterranean, one Atlantic, and three +Pacific. + + + +Subgenus 1. _Thalassicollarium_, Haeckel. + +_Definition._--Membrane of the central capsule structureless, only +perforated by innumerable very small radial pores. + + +{19}1. _Thalassicolla pellucida_, n. sp. + +Spherical body very soft, transparent, clear and colourless, without any +pigment. Central capsule soft, hyaline, with a thin, structureless, not +areolated membrane. Diameter of the central capsule about three times that +of the nucleus, one-fourth to one-sixth that of the jelly-envelope. Nucleus +delicate, transparent, with one single central nucleolus, about one-third +its diameter. Protoplasm of the central capsule contains only small, +pellucid, densely packed globules (vacuoles?), no oil-globules. +Extracapsular body quite transparent, without pigment or oil-globules, only +composed of the large alveoles imbedded in the jelly-cover, and of the fine +protoplasmic network between them. No xanthellae. + +_Dimensions._--Diameter of the central capsule 0.8 to 1.2, of the nucleus +0.3 to 0.4, of the calymma 3 to 6 mm. + +_Habitat._--Cosmopolitan, Canary Islands, Haeckel; Cape, Australia, +Pacific, Challenger; surface. + + +2. _Thalassicolla spumida_, n. sp. + +Spherical body nearly transparent, yellowish, without dark pigment. Central +capsule pellucid, with a thick, structureless, not areolated membrane. +Diameter of the central capsule about twice that of the nucleus, one-sixth +to one-eighth that of the jelly-cover. Nucleus delicate, somewhat opaque, +with numerous small nucleoli. Protoplasm of the central capsule contains +small pellucid globules (vacuoles?), and immediately under its membrane (on +its inside) one single layer of large, dark, refractive oil-globules. +Extracapsular body very voluminous, foamy, with innumerable alveoles in the +jelly, and many xanthellae between them. + +_Dimensions._--Diameter of the central capsule 0.6 to 0.8, of the nucleus +0.3 to 0.4, of the calymma 3 to 5 mm. + +_Habitat._--Atlantic, Canary Islands, Haeckel; Cape Verde Islands, +Challenger Station 350; Brazil, Rabbe; surface. + + +3. _Thalassicolla zanclea_, Haeckel. + + _Thalassicolla zanclea_, Haeckel, 1862, Monogr. d. Radiol., p. 252, Taf. + ii. fig. 3. + +Spherical body opaque, transparent only in the periphery, with colourless +central capsule, but with brown or black pigment-powder scattered +everywhere through the extracapsular alveolated jelly-cover. Central +capsule soft, transparent, colourless, with a thin structureless, not +areolated membrane. Diameter of the central capsule about one and a half +times that of the nucleus, one-half or one-third that of the jelly-cover. +Nucleus delicate, transparent, with a thin, finely punctated membrane, with +one or more nucleoli. Protoplasm of the central capsule contains only +small, pellucid, densely packed globules (vacuoles?), no oil-globules. +Extracapsular body very dark and opaque, with a great mass of brown or +blackish-brown pigment between the alveoles of the jelly-cover. Numerous +xanthellae. + +_Dimensions._--Diameter of the central capsule 0.1 to 0.12, of the nucleus +0.07 to 0.08, of the calymma 0.2 to 0.4. + +_Habitat._--Mediterranean, Messina, Haeckel. + + + +{20}Subgenus 2. _Thalassicollidium_, Haeckel. + +_Definition._--Membrane of the central capsule areolated, with small +polygonal plates, resembling an epithelial cell-tissue, spotted by +innumerable fine radial pores. + + +4. _Thalassicolla australis_, n. sp. + +Spherical body nearly transparent, without dark pigment. Central capsule +colourless, somewhat opaque, with a thick and firm, very elastic membrane, +areolated by polygonal, punctated figures resembling cells. Diameter of the +central capsule about three times that of the nucleus, one-third that of +the jelly-cover. Nucleus thin-walled, with many small nucleoli. Protoplasm +of the central capsule finely granulated, containing numerous hyaline +globules (vacuoles?) of different size, and in each of these one single +roundish, dark refringing corpuscle, concentrically lamellated like an +amylum grain. Extracapsular body without pigment or oil-globules, only +composed of the large alveoles imbedded in the jelly-cover, and of the fine +protoplasmic network between them. No xanthellae. + +_Dimensions._--Diameter of the central capsule 1 to 2, of its nucleus 0.3 +to 0.4, of the nucleoli 0.12 to 0.16, of the hyaline globules in the +protoplasm of the capsule 0.02 to 0.05; calymma, 4 to 6 mm. + +_Habitat._--South-west Pacific, east coast of Australia, New Zealand, &c.; +Challenger Stations 163, 171; surface. + + +5. _Thalassicolla nucleata_, Huxley. + + _Thalassicolla nucleata_, Huxley, 1851, Ann. and Mag. Nat. Hist., ser. 2, + vol. viii. p. 435, pl. xvi. fig. 4. + + _Thalassicolla nucleata_, J. Mueller, 1858, Abhandl. d. k. Akad. d. Wiss. + Berlin, p. 28. + + _Thalassicolla coerulea_, Schneider, 1858, Archiv f. Anat. u. Physiol., + p. 40, Taf. iii. Bd. i. figs. 5-7. + + _Thalassicolla nucleata_, Haeckel, 1862, Monogr. d. Radiol., p. 249, Taf. + iii. figs. 1-5. + + _Thalassicolla nucleata_, R. Hertwig, 1876, Histologie d. Radiol., p. 43, + Taf. iii. figs. 61-5, Taf. iv., v. + + _Thalassicolla nucleata_, R. Hertwig, 1879, Organismus d. Radiol., p. 34. + +Spherical body in the central part opaque, black or dark coloured, in the +periphery transparent, whitish, or yellowish. Central capsule rather +compact, yellowish, opaque, with a thick and firm, very elastic membrane, +areolated by polygonal, punctated figures resembling cells. Diameter of the +central capsule about twice as large as that of the nucleus, one-half to +one-fourth that of the jelly-cover. Nucleus with a very thick, finely +punctated membrane, containing a viscous fluid (when coagulated finely +granular), and sometimes one large, central, spherical, or ramified +nucleolus, sometimes a variable number of smaller roundish nucleoli. +Protoplasm of the central capsule containing many very variable corpuscles, +mostly pellucid (albuminous?) spherules, containing oil-globules, or +concentric amyloid concretions, or crystals, &c. Extracapsular body with +dark pigment-powder of variable colour (black, brown, violet, blue, &c.), +densely aggregated around the central capsule, more loosely dissipated +between the alveoles of the outer jelly-cover. Xanthellae very numerous. + +{21}_Dimensions._--Diameter of the central capsule 0.4 to 0.8, of the +nucleus 0.02 to 0.05, of the calymma 1 to 5 mm. + +_Habitat._--Cosmopolitan; common in all warmer seas; Mediterranean, +Atlantic, Indian Ocean, Pacific, mainly between lat. 40d N. and lat. 40d +S.; surface. + + +6. _Thalassicolla maculata_, n. sp. (Pl. 1, fig. 4). + +Spherical body in the central part opaque, black or dark coloured, in the +periphery semi-transparent, spotted. Central capsule compact, yellowish, +opaque, with a thick and firm, very elastic membrane, areolated by +polygonal, punctated figures resembling cells. Diameter of the central +capsule about twice that of the nucleus, one-third to one-fifth that of the +jelly-cover. Nucleus thin-walled, with one large spherical nucleolus. +Protoplasm of the central capsule contains innumerable very small, hyaline, +spherical vesicles of equal size (or vacuoles?), two to four times as broad +as the separating bridges of protoplasm. Extracapsular body with dark +pigment-powder of black or brown colour, densely accumulated around the +central capsule (in the matrix), loosely scattered between the alveoles of +the outer jelly-cover. The latter appears spotted by numerous large, +roundish lumps of protoplasm, scattered between the alveoles. No +xanthellae. + +_Dimensions._--Diameter of the central capsule 0.3 to 0.6, of the nucleus +0.2 to 0.3, of the hyaline globules in the protoplasm of the capsule 0.02 +to 0.03; calymma, 2 to 3 mm. + +_Habitat._--South Pacific, Challenger Station 289. + + +7. _Thalassicolla melacapsa_, n. sp. (Pl. 1, fig. 5). + +Spherical body in the central part opaque, black or dark coloured, in the +periphery semi-transparent, spotted. Central capsule compact, black, with a +thick and firm, very elastic membrane, areolated by polygonal, punctated +figures resembling cells. Diameter of the central capsule about twice that +of the nucleus, one-third or half that of the jelly-cover. Nucleus +thin-walled, transparent, containing very numerous and small nucleoli. +Protoplasm of the central capsule filled with small black pigment-granules, +quite intransparent, contains densely packed hyaline (albuminous?) globules +of equal size; every pellucid globule includes a smaller globule (one-third +or one-fourth its diameter), which appears to be composed of aggregated +oil-bubbles. Extracapsular body without pigment, contains between its +alveoles in the inner half numerous, dark refractive oil-globules, in the +outer half numerous amoeboid lumps of protoplasm, irregularly scattered. No +xanthellae. + +_Dimensions._--Diameter of the central capsule 2 to 2.5, of the nucleus 1 +to 1.5, of the hyaline globules in the protoplasm of the capsule 0.03 to +0.04; calymma, 3 to 5 mm. + +_Habitat._--South-east Pacific (near Valparaiso), Challenger Station 300, +surface. + + + +Genus 5. _Thalassophysa_,[12] Haeckel, 1881, Prodromus, p. 470. + +_Definition._--Thalassicollida without intracapsular alveoles, but with +large roundish or globular alveoles within the extracapsular calymma. +Nucleus in the centre of the capsule papillate or branched. + +{22}The genus _Thalassophysa_ contains those species of Thalassicollida +formerly associated with _Thalassicolla_, which are distinguished by the +complicated, ramose, or papillate form of the large nucleus. All three +species here described are found in the Mediterranean and the Atlantic. To +this genus appertains also that strange form of Radiolaria which I +described in 1870 as _Myxobrachia_ (compare _Thalassophysa sanguinolenta_). + + +1. _Thalassophysa papillosa_, n. sp. + + _Thalassicolla papillosa_, Haeckel, 1867, Manuscript. + +Spherical body transparent, colourless, or somewhat yellowish. Central +capsule soft, colourless, with a very thin but firm, elastic, structureless +membrane. Diameter of the central capsule about twice that of the nucleus, +one-fourth to one-sixth that of the jelly-envelope. Nucleus papillated, its +spherical surface covered with a great number (50 to 80) of conical or +finger-like protuberances or blind sacs, not longer than half its radius. +Protoplasm of the central capsule filled with very small and numerous +spherical vacuoles, without oil-globules. Extracapsular jelly-body, without +dark pigment, oil-globules, and large protoplasmic lumps, contains between +its alveoles very numerous xanthellae. + +_Dimensions._--Diameter of the whole jelly sphere 4 to 5 mm., of the +central capsule 0.8 to 1 mm., of its nucleus 0.4 to 0.5. + +_Habitat._--Canary Islands, Lanzerote, common, Haeckel; Cape Verde Islands, +Challenger; surface. + + +2. _Thalassophysa sanguinolenta_, Haeckel. + + _Thalassicolla sanguinolenta_, Haeckel, 1870, Jenaische Zeitschr., Bd. v. + p. 526, Taf. 18. + + _Thalassicolla sanguinolenta_, Haeckel, 1870, Biolog. Studien, i. p. 113, + Taf. iv. + + _Thalassicolla sanguinolenta_, R. Hertwig, 1879, Organismus d. Radiol., + p. 37, Taf. iii. fig. 1. + + _Myxobrachia rhopalum_, Haeckel, 1870, Jenaische Zeitschr., Bd. v. p. + 519, Taf. 18 (et in Biol. Stud., _loc. cit._). + + _Myxobrachia pluteus_, Haeckel, 1870, Jenaische Zeitschr., Bd. v. p. 520, + Taf. 18 (et in Biol. Stud., _loc. cit._). + +Spherical body in the central part opaque, reddish, in the periphery +transparent, yellowish. Central capsule compact, white, red spotted, with a +thick elastic membrane, perforated by pores, but not areolated. Diameter of +the central capsule three times that of the nucleus, one-fifth to +one-eighth that of the jelly-envelope. Nucleus papillated, its spherical +surface covered with numerous (80 to 120) conical or finger-like +protuberances not longer than one-fourth or one-third of its radius. On the +inside of these blind sacs lie numerous small roundish nucleoli. Protoplasm +of the central capsule in the outer (cortical) zone (on the inside of the +membrane) radially striped, with one layer of very numerous red +oil-globules of equal size, producing its blood-spotted appearance; in the +inner (medullary) zone foamy, with numerous small spherical vacuoles. +Extracapsular jelly-body without dark pigment, contains between its +alveoles no large protoplasmic lumps (as in _Thalassophysa pelagica_), but +numerous small oil-globules and xanthellae. This species sometimes amasses +in its jelly-envelope large accumulations of Coccoliths and Coccospheres, +{23}which are much heavier than the jelly-body, and produce arm-like +protuberances of it; this modified form, often of very regular and peculiar +appearance, I formerly described as _Myxobrachia_ (compare my Biolog. +Studien, _loc. cit._, and Hertwig, _loc. cit._, p. 37). Compare also +_Myxobrachia cienkowski_, Wagner, 1872, L. N. 23. + +_Dimensions._--Diameter of the whole jelly-sphere 5 to 8 mm., of the +central capsule 1 to 1.2 mm., of its nucleus 0.3 to 0.4. + +_Habitat._--Canary Islands, Lanzerote; common, Haeckel; Mediterranean, +Messina, Hertwig; surface. + + +3. _Thalassophysa pelagica_, Haeckel. + + _Thalassicolla pelagica_, Haeckel, 1862, Monogr. d. Radiol., p. 247, Taf. + i. + + _Thalassicolla pelagica_, R. Hertwig, 1879, Organismus d. Radiol., p. 35, + Taf. iii. fig. 4. + +Spherical body in the central part opaque, yellowish, in the periphery +semi-transparent, spotted. Central capsule compact, yellowish-white, with a +thick and compact membrane, perforated by pores, but not areolated. +Diameter of the central capsule about twice that of the nucleus, one-half +to one-sixth that of the jelly-envelope. Nucleus papillated, its spherical +surface covered with numerous (20 to 60) conical, roundish, or finger-like +protuberances, not longer than its radius (commonly only one-half or +one-third as long). Enclosed in the semi-fluid substance of the nucleus are +very long and thin cylindrical nucleoli snake-like, contorted, and +penetrating into the protuberances of the nucleus. Protoplasm of the +central capsule in the outer (cortical) zone (on the inside of the +membrane) radially striped, with one layer of large oil-globules of +different sizes; in the inner (medullary) zone foamy, with numerous small +spherical vacuoles, mostly of equal size. Extracapsular jelly-body without +dark pigment, contains between its alveoles a large number of large +roundish or amoeboid lumps of protoplasm, and very numerous yellow cells or +xanthellae (compare the detailed description in my Monograph, and in R. +Hertwig's work). + +_Dimensions._--Diameter of the whole jelly-sphere 1 to 4 mm., of the +central capsule 0.5 to 0.6, of the nucleus 0.2 to 0.3. + +_Habitat._--Mediterranean--Messina, Corfu, Nizza, Genoa, Haeckel; Messina, +R. Hertwig; surface. + + + +Family II. #COLLOZOIDA#, Haeckel, 1862 (Pl. 3). + +_Collozoida_, Haeckel, 1862, Monogr. d. Radiol., p. 522. + +_Definition._--#Colloidea# socialia. + +The family Collozoida comprises all associated or colony-building +Radiolaria without skeleton. We unite here all these skeletonless +Radiolarian colonies into one single genus _Collozoum_, constituted (1862) +in my Monograph (p. 522). The oldest known form of it was the _Collozoum +inerme_, described firstly by Johannes Mueller (1856) as _Sphaerozoum +inerme_. Two other species of the genus were figured (1862) in my Monograph +(p. 522, Tafn. xxxii., xxxv.). A most accurate description of its +histological structure and {24}development was given in 1876 by Richard +Hertwig in his Histologie der Radiolarien (pp. 12-42, Tafn. i., ii.). A +number of other very remarkable forms of _Collozoum_ have been observed by +me during the last few years, and partly figured in Pl. 3. + +_Collozoum_, as the only representative of this family, is sufficiently +distinguished from all other Radiolaria by the definition "_Skeletonless +Radiolarian Colonies._" These occur floating on the surface of all warmer +seas, often in astonishing masses, and may be easily confounded, owing to +their external resemblance, with the jelly-like egg-masses of certain +Mollusca. _Collozoum_ is derived either from _Actissa_ or from +_Thalassicolla_, simply by multiplication of the unicellular body and by +reunion of the associated capsules in one common calymma or jelly-veil; +this is constantly alveolated, as in _Thalassicolla_. As in _Actissa_, the +form of the central capsule remains either spherical, or it becomes +ellipsoidal or discoidal, rarely polyhedral or amoeboid. In _Collozoum_ as +in all colonial Radiolaria, the original central nucleus commonly undergoes +cleavage very early into numerous small nuclei, whilst its place is usually +taken by a central oil-globule. This peculiarity may serve often (but not +constantly) for the distinction of isolated capsules of _Collozoum_ from +_Actissa_. + + + +Genus 6. _Collozoum_,[13] Haeckel, 1862, Monogr. d. Radiol., p. 522. + +_Definition._--Skeletonless colonies of Radiolaria. + +The genus _Collozoum_, as already mentioned, is the only representative of +its family, and comprises all Radiolaria living associated in colonies, and +having no skeleton. Therefore _Collozoum_ possesses all the peculiarities +described above. Although the floating colonies of this genus occur in +enormous masses on the surface of all warmer seas, nevertheless the number +of different species in this genus is not great, and amounts only to +thirteen. If this number increase by further investigations, the subgenera +distinguished in the following description can be advanced to the range of +genera; in which case _Collodinium_ (or _Collozoum_ sensu restricto) will +be characterised by the spherical form of its central capsules, +_Colloprunum_ by the ellipsoidal form (Pl. 3, fig. 9), _Collophidium_ by +the cylindrical, very prolonged form (figs. 2, 3), _Collodiscus_ by the +lenticular or discoidal form, and _Collodastrum_ by the indefinite, +polyhedral, or amoeboid form (figs. 4, 5). + + +Subgenus 1. _Collodinium_, Haeckel. + +_Definition._--Form of the central capsules spherical or subspherical, +never polyhedral, ellipsoidal, or cylindrical. + + +{25}1. _Collozoum inerme_, Haeckel (Pl. 3, figs. 10-12). + + _Collozoum inerme_, Haeckel, 1862, Monogr. d. Radiol., p. 522, Taf. xxxv. + + _Collozoum inerme_, Cienkowski, 1871, Archiv. f. mikrosk. Anat., vol. + vii. p. 376, Taf. xxix. figs. 18-36. + + _Collozoum inerme_, R. Hertwig, 1876, Histologie der Radiol., p. 12, Taf. + i., ii. + + _Collozoum inerme_, R. Hertwig, 1879, Organismus d. Radiol., p. 31, Taf. + iii. fig. 12. + + _Sphaerozoum inerme_, J. Mueller, 1856, Monatsber. d. k. Akad. d. Wiss. + Berlin, p. 478; Abhandl., p. 54. + + _Sphaerozoum bicellulare_, J. Mueller, 1858, Abhandl. d. k. Akad. d. + Wiss. Berlin, p. 54, Taf. viii. fig. 5. + + _Thalassicolla punctata_, Huxley (_pro parte_), 1851, Ann. and Mag. Nat. + Hist., ser. 2, vol. viii. p. 433. + +Central capsules spherical, with thin, simple-edged membrane, with one +single oil-globule in the centre. (If the capsules multiply by division, +the spherical form becomes violin-shaped, constricted in the middle; and in +this condition the number of oil-globules increases; but in the ordinary +mature state the capsule of this species remains spherical, and its +oil-globule solitary. In quite young capsules the oil-globules are wanting; +Pl. 3, fig. 12.) + +_Dimensions._--Diameter of the central capsules 0.04 to 0.16. + +_Habitat._--Cosmopolitan, common in all warmer seas (Mediterranean, +Atlantic, Indian, and Pacific), surface. + + +2. _Collozoum nostochinum_, n. sp. + +Central capsules spherical, very large, opaque, distended with red +pigment-granules and with very numerous (two hundred to three hundred) +small oil-globules. Membrane thick, double-edged. + +_Dimensions._--Diameter of the central capsules 0.3 to 0.5. + +_Habitat._--Indian Ocean, off Socotra, surface, Haeckel. + + +3. _Collozoum volvocinum_, n. sp. + +Central capsules spherical, very large, opaque, containing a great number +(ten to thirty) of large oil-globules, and between them densely packed +masses of dark pigment. Membrane thick, double-edged. This species differs +from _Collozoum inerme_, mainly by the great size of the central capsules +(three to five times as big as in the former) and the great number of +oil-globules in them. + +_Dimensions._--Diameter of the central capsules 0.2 to 0.3. + +_Habitat._--Central Pacific, Station 272, surface. + + +Subgenus 2. _Colloprunum_, Haeckel. + +_Definition._--Form of the central capsules ellipsoidal, with one prolonged +axis. + + +4. _Collozoum ovatum_, n. sp. + + _Colloprunum ovatum_, Haeckel, 1882, Manuscript. + +Central capsules ovate or ellipsoidal, its longer diameter twice to three +times as large as the shorter. In the centre of every capsule one single +oil-globule. + +{26}_Dimensions._--Length of the central capsules 0.2 to 0.3, breadth of +them 0.1 to 15. + +_Habitat._--North Pacific, Station 244, surface. + + +5. _Collozoum ellipsoides_, n. sp. (Pl. 3, figs. 8, 9). + + _Colloprunum ellipsoides_, Haeckel, 1882, Manuscript. + +Central capsules regularly ellipsoidal, very large; their longer diameter +once and a half to twice as large as the shorter. In every capsule fifty to +eighty oil-globules. + +_Dimensions._--Length of the central capsules 0.3 to 4, breadth of them +0.2. + +_Habitat._--North Atlantic, Faeroee Channel (Gulf Stream), surface, John +Murray. + + +Subgenus 3. _Collophidium_, Haeckel. + +_Definition._--Form of the central capsules cylindrical, often snake-like, +contorted, with one axis much prolonged, several times longer than the +transverse axis. + + +6. _Collozoum contortum_, n. sp. + + _Collophidium contortum_, Haeckel, 1882, Manuscript. + +Central capsules cylindrical, three to four times as long as broad, C- or +S-like curved, transparent, without oil-globules. + +_Dimensions._--Length of the central capsules 0.2 to 0.3, breadth 0.06 to +0.08. + +_Habitat._--Tropical Atlantic, Station 347, surface. + + +7. _Collozoum serpentinum_, n. sp. (Pl. 3, figs. 1-3). + + _Collophidium serpentinum_, Haeckel, 1882, Manuscript. + +Central capsules cylindrical, filiform, much elongated, ten to one hundred +times, sometimes two hundred to four hundred times as long as broad, +snake-shaped or worm-shaped, curved and contorted in the most irregular +manner, often spiral or twisted into a large nodule. Numerous oil-vesicles +constantly present, forming one series of globules in the axis of every +capsule; distance of the globules, one from another, and also from the +capsule-membrane, about equal to their diameter. (This interesting and very +curious form was very frequently observed living by me in the Canary +Islands, in January 1867; the jelly-colonies were commonly spherical, and +contained fifty to two hundred or more capsules of very different size and +form.) + +_Dimensions._--Length of the central capsules 1 to 10, sometimes 20 to 40 +mm.; average breadth 0.1 mm. + +_Habitat._--Canary Islands, Lanzerote, Haeckel, surface. + + +{27}8. _Collozoum vermiforme_, n. sp. (Pl. 3, figs. 6, 7). + + _Collophidium vermiforme_, Haeckel, 1882, Manuscript. + +Central capsules cylindrical, much elongated, five to ten times (sometimes +twenty to fifty times) as long as broad, snake-shaped or worm-shaped, very +irregularly curved and contorted. Numerous oil-globules constantly present, +forming in the axis of every capsule a double series of alternating +rose-coloured globules. (This species is nearly allied to the preceding; +but its capsules are thicker and shorter, and the oil-vesicles in them are +arranged not in a single, but in a double row.) + +_Dimensions._--Length of the central capsules 0.6 to 1.2 mm., sometimes 3 +to 6 mm.; breadth 0.12. + +_Habitat._--Tropical Atlantic, near the west coast of Africa, Station 349, +Canary Islands, surface. + + +Subgenus 4. _Collodiscus_, Haeckel. + +_Definition._--Form of the central capsules discoidal or lenticular, with +one shortened axis. + + +9. _Collozoum coeruleum_, Haeckel. + + _Collozoum coeruleum_, Haeckel, 1862, Monogr. d. Radiol., p. 523, Taf. + xxxii. figs. 6-8. + + _Collodiscus coeruleus_, Haeckel, 1882, Manuscript. + +Central capsule lenticular or discoidal, flattened, blue coloured, with one +single oil-globule in the centre. Protoplasm containing numerous crystals +and dark blue pigment-granules. Membrane very thick, double-edged. (Whilst +at Messina in 1859 I found this form not constantly discoidal, in 1867 in +the Canary Islands I observed it constantly lenticular.) + +_Dimensions._--Breadth of the central capsules 0.1 to 0.15, height 0.04 to +0.08. + +_Habitat._--Mediterranean (Messina), Atlantic (Canary Islands), surface. + + +10. _Collozoum discoideum_, n. sp. + + _Collodiscus discoideus_, Haeckel, 1882, Manuscript. + +Central capsule discoidal, flattened, transparent, with a ring of twenty to +twenty-five oil-globules in its circular periphery (on the inside of the +thin membrane). + +_Dimensions._--Breadth of the central capsules 0.2, height 0.05. + +_Habitat._--South Pacific (Juan Fernandez), Station 300, surface. + + +Subgenus 5. _Collodastrum_, Haeckel. + +_Definition._--Form of the central capsules irregular and indefinite, +variable, commonly polyhedral or polygonal, or amoeboid, often with +irregular, finger-like processes. + + +{28}11. _Collozoum pelagicum_, Haeckel. + + _Collozoum pelagicum_, Haeckel, 1862, Monogr. d. Radiol., p. 525, Taf. + xxxii. figs. 4, 5. + + _Sphaerozoum pelagicum_, Haeckel, 1860, Monatsber. d. k. Akad. d. Wiss. + Berlin, 1860, p. 845. + +Central capsules small, quite irregularly formed, roundish-polyhedral or +depressed-polygonal, transparent, without oil-globules. Often many +extracapsular oil-vesicles in the common jelly-body between the central +capsules. Membrane very thin and delicate. + +_Dimensions._--Diameter of the central capsules 0.02 to 0.08. + +_Habitat._--Mediterranean, Messina, Haeckel; Naples, Brandt; surface. + + +12. _Collozoum stellatum_, n. sp. + + _Collodastrum stellatum_, Haeckel, 1882, Manuscript. + +Central capsules star-shaped, irregularly radiating, with a great number +(eight to twenty or more) of radial, short, conical, acute processes, very +variable in size and number. Membrane thin. In every capsule several (four +to eight) oil-globules. + +_Dimensions._--Diameter of the central capsules 0.12 to 0.2. + +_Habitat._--Central Pacific, Station 274, surface. + + +13. _Collozoum amoeboides_, n. sp. (Pl. 3, figs. 4, 5). + + _Collodastrum amoeboides_, Haeckel, 1882, Manuscript. + +Central capsules amoebiform, of moderate size, quite irregularly formed, +with a variable number of finger-like, obtuse, irregular prolongations +(commonly three to six), very variable in size and form. Membrane thin. In +the centre of every capsule one single oil-globule. + +_Dimensions._--Diameter of the central capsules 0.04 to 0.08. + +_Habitat._--Indian Ocean, Ceylon, Haeckel; Madagascar, Rabbe; surface. + + +---- + + +Suborder II. BELOIDEA, Haeckel. + +_Definition._--SPUMELLARIA with an imperfect skeleton, composed of numerous +solid needles or spicula, scattered irregularly in the calymma. + + +The suborder #Beloidea# comprises all those SPUMELLARIA which possess an +imperfect or rudimentary skeleton, composed of a variable number of +isolated spicula scattered in the extracapsulum. The suborder contains only +two different families, the solitary Thalassosphaerida (or Beloidea +monozoa) and the associated Sphaerozoida (or Beloidea polyzoa). Both +families are very nearly allied, and differ only in one single character: +the solitary life of the former, the social union of the {29}latter. It +seems to be merely a consequence of this difference that the cleavage of +the nucleus commonly takes place very late in the former, very early in the +latter. + +Commonly, therefore, the full-grown Thalassosphaerida (until immediately +before their propagation) exhibit one single nucleus in the centre of the +capsule, whilst in the Sphaerozoida the capsule is distended with numerous +small nuclei. In these latter the centre of the capsule usually contains +one large oil-globule, whilst in the former oil-globules are either wanting +or scattered in large numbers in the endoplasm, or disposed in one layer on +the inside of the capsule membrane. + +In the solitary Thalassosphaerida each capsule is enclosed in its own +peculiar spherical calymma, whilst in the associated Sphaerozoida all the +capsules of the colony are united into one common, very voluminous, +alveolated calymma. + + + +Family III. #THALASSOSPHAERIDA#, Haeckel, 1862, (Pl. 2). + +_Thalassosphaerida_, Monogr. d. Radiol., p. 255. + +_Definition._--#Beloidea# solitaria. + +The family Thalassosphaerida comprises all solitary SPUMELLARIA with an +imperfect skeleton, composed of numerous solid needles or spicula, +scattered around the central capsule in the calymma. The structure of the +unicellular soft body is quite the same as in the Thalassicollida; it +differs from these only in the possession of the extracapsular skeleton. +All needles of this skeleton are solid siliceous spicula, never hollow, as +in the similar Cannorrhaphida among the PHAEODARIA. In the special +structure and form of the skeleton the Thalassosphaerida agree perfectly +with the well-known, colony-building Sphaerozoida; they differ from these +only by their hermit-like life and by some peculiarities derived from this +solitary development. + +The oldest known form of this family is probably the first Radiolarian, +observed in the living state, described in 1834 by Meyen as _Physematium +atlanticum_ (see p. 35). A second form was figured in my Monograph (1862) +as _Thalassosphaera bifurca_ (p. 260, Taf. xii. fig. 1). A third form was +there described under the name _Thalassosphaera morum_; this remarkable +form was first observed by Johannes Mueller, and figured under the name +_Thalassicolla morum_ (1858, Abhandl., p. 28, Taf. vii. figs. 1, 2). The +same form was afterwards observed living by myself in the Mediterranean, as +well as in the Atlantic, and in great numbers by the late Sir Wyville +Thomson in the Pacific. The latter gave a good figure of it with some +valuable remarks in his excellent work, The Atlantic (1877, vol. i. p. 233, +fig. 51). He called this peculiar Rhizopod _Calcaromma calcarea_, on +account of the very peculiar _calcareous_ bodies "looking in outline like +the rowels of spurs," which are accumulated in great quantity around the +central capsule, in the calymma. Further investigations have convinced me +that these peculiar stellate {30}bodies of carbonate of lime, for which we +propose the name "Calcastrella," are not parts of the skeleton produced by +the Radiolarian, but foreign bodies picked up by its extracapsular sarcode +(in the same way as the Coccoliths are picked up by _Thalassicolla +sanguinolenta = Myxobrachia!_). These Calcastrella occur also in the +calymma of some Discoidea and other Radiolaria; they are either unicellular +calcareous Algae, or foreign bodies of other origin. The _Collodarium_, +however, described as _Thalassicolla morum_ and _Calcaromma calcarea_, +seems to be a simple _Actissa_, which has picked up a number of +Calcastrella. + +The Challenger collection has yielded a number of other true +Thalassosphaerida, which partly agree with _Thalassosphaera_ in the simple +structure of the unicellular body (resembling _Actissa_), and partly differ +from it in the development of alveoles, either within or without the +central capsule (similar to _Thalassolampe_ and _Thalassicolla_). The solid +siliceous spicula, which occur in great numbers scattered in the calymma, +agree perfectly in form with the spicula of the colony-building +Sphaerozoida. A characteristic difference between the social and the +solitary #Beloidea# seems to be determined by the cleavage of the nucleus, +which takes place in the latter very late, in the former very early. +Therefore in the large central capsule of the mature solitary +Thalassosphaerida, we commonly find one large nucleus in the centre, and a +number of oil-globules around it in the endosarc, or disposed in one layer +on the inside of the capsule-membrane (Pl. 2, figs. 2, 5); whereas in the +much smaller associated capsules of the Sphaerozoida one large oil-globule +is placed commonly in the centre, and a great number of small nuclei +scattered in the endoplasm (compare above, p. 24). + +_Synopsis of the Genera of Thalassosphaerida._ + + A. Alveoles neither within { Spicula simple, 7. _Thalassosphaera_. + nor without the { + central capsule. { Spicula branched, 8. _Thalassoxanthium_. + + B. Numerous large alveoles } + within the central } Spicula simple, 9. _Physematium_. + capsule (not in the } + calymma). } + + C. Numerous large alveoles { Spicula simple, 10. _Thalassoplancta_. + within the calymma (not { + in the central capsule). { Spicula branched, 11. _Lampoxanthium_. + + +Genus 7. _Thalassosphaera_,[14] Haeckel, 1862, Monogr. d. Radiol., p. 259. + +_Definition._--Thalassosphaerida without alveoles, with simple, unbranched, +needle-shaped spicula in the calymma. + +The genus _Thalassosphaera_ was founded by me in 1862 for those solitary +#Collodaria# in which the simple central capsule is surrounded by scattered +solid spicula. {31}I described these two different species, the new +_Thalassosphaera bifurca_ and the _Thalassosphaera morum_, which J. Mueller +had formerly called _Thalassicolla morum_. This latter form is +characterised by peculiar _calcareous_ bodies "looking in outline like the +rowels of spurs, scattered irregularly in the gelatinous envelope," and was +therefore afterwards called "_Calcaromma calcarea_" by Sir Wyville +Thomson.[15] As already mentioned above, these calcareous rowels are +foreign bodies, picked up by an _Actissa_ (see p. 29). I here confine the +genus _Thalassosphaera_ to those solitary #Beloidea# in which the body +exhibits no alveoles, and the siliceous solid spicula in the calymma are +quite simple needles. + + +_Thalassosphaera belonium_, n. sp. + +Spicula thin cylindrical rods, more or less curved, pointed at both ends, +with smooth surface (similar to the needles of _Rhaphidozoum italicum_). +Central capsule spherical, three times as large as the central nucleus, +without larger oil-globules. + +_Dimensions._--Diameter of the central capsule 0.1 to 0.12, length of the +spicula 0.04 to 0.08. + +_Habitat._--Central Pacific, Station 272, surface. + + +_Thalassosphaera rhaphidium_, n. sp. + +Spicula thick cylindrical rods, more or less curved, pointed at both ends, +covered with numerous strong conical thorns, perpendicular to the axis. +Central capsule spherical, four times as broad as the central nucleus, with +twenty to thirty large oil-globules on the inside of the membrane. + +_Dimensions._--Diameter of the central capsule 0.2, length of the spicula +0.12 to 0.16. + +_Habitat._--Tropical Atlantic, Station 347, surface. + + +Genus 8. _Thalassoxanthium_,[16] Haeckel, 1881, Prodromus, p. 470. + +_Definition._--Thalassosphaerida without alveoles, with numerous branched +or compound spicula in the calymma. + +The genus _Thalassoxanthium_ differs from the foregoing _Thalassosphaera_, +by the ramification of the spicula, and has therefore the same relation to +it as _Sphaerozoum_ to _Belonozoum_. The soft unicellular body is as simple +as in _Actissa_, and exhibits alveoles neither in the capsule nor in the +calymma. + + +Subgenus 1. _Thalassoxanthella_, Haeckel. + +_Definition._--Spicula not geminate, but simply radiate, consisting of +three, four, or more needles or shanks, radiating in different directions +from one and the same point; shanks now simple or needle-like, now furcate +or branched. + + +{32}1. _Thalassoxanthium triactinium_, n. sp. + +Spicula all (or nearly all) triradiate, composed of three (or sometimes in +a few spicula four) needle-like shanks of equal length, diverging from one +common point. Shanks straight or somewhat curved, smooth, pointed. Central +capsule pellucid, twice as broad as its dark nucleus, without larger +oil-globules. Jelly-envelope very thin, with numerous xanthellae. + +_Dimensions._--Diameter of the central capsule 0.1, of its nucleus 0.05, +length of the spicule-shanks 0.6 to 0.8. + +_Habitat._--Central Pacific, Station 266, surface. + + +2. _Thalassoxanthium triradiatum_, n. sp. + +Spicula all (or nearly all) triradiate, composed of three (or sometimes in +a few spicula four) needle-like shanks of different length, diverging from +one common point. Shanks curved or bent, covered with small conical thorns. +Central capsule dark, three times as large as the nucleus, with numerous +large oil-globules. Jelly-envelope thick, without xanthellae. + +_Dimensions._--Diameter of the capsule 0.2, of the nucleus 0.07, length of +the spicule-shanks 0.1 to 0.15. + +_Habitat._--South Pacific, Station 302, surface. + + +3. _Thalassoxanthium medusinum_, n. sp. (Pl. 2, fig. 5). + +Spicula all (or nearly all) quadriradiate, irregular, composed of four (or +sometimes in a few spicula three) needle-like shanks (mostly of unequal +length), diverging from one common point. Shanks curved, pointed, thorny, +covered with small spinules. Central capsule dusky, twice to three times as +large as its dark central nucleus. On the inside of the membrane numerous +large oil-globules. Jelly-envelope thin, with numerous xanthellae. + +_Dimensions._--Diameter of the central capsule 0.45 to 0.5, of its nucleus +0.18 to 0.2. + +_Habitat._--North Pacific, Station 244, surface. + + +4. _Thalassoxanthium hexactinium_, n. sp. + +Spicula all (or nearly all) hexaradiate, composed of six (or sometimes in a +few spicula three) needle-like shanks, diverging in two opposite +hemispheres (three needles upwards, three needles downwards). Shanks +somewhat curved, pointed, smooth. Central capsule yellowish-brown, dark, +four times as broad as its dark central nucleus. Jelly-envelope thick +(about twice as broad as the capsule), with very numerous xanthellae. + +_Dimensions._--Diameter of the central capsule 0.3 to 0.4, of its nucleus +0.1 to 0.12. + +_Habitat._--South Atlantic, Station 325, surface. + + +{33}5. _Thalassoxanthium cervicorne_, n. sp. (Pl. 2, figs. 3, 4). + +Spicula all triradiate, trichotomously branched, with three equal shanks, +which diverge from one common point, and are again provided each with three +branches on the distal end. These nine branches are commonly once or twice +forked (each fork rarely provided with three ramules). The ramules are +thin, unequal, curved, or bent, and the ramification nearly resembles a +stag's horn. Central capsule transparent, without oil-globules, two to +three times as broad as the dark nucleus, which contains one single long +central nucleolus. Calymma thin, scarcely as thick as the radius of the +nucleus. + +_Dimensions._--Diameter of the central capsule 0.2 to 0.25, of the nucleus +0.08 to 0.1, length of the spicula 0.05 to 0.15. + +_Habitat._--Central Pacific, Stations 271, 274, surface. + + + +Subgenus 2. _Thalassoxanthomma_, Haeckel. + +_Definition._--Spicula all or partly geminate, consisting of one middle or +axial rod, from the two poles of which diverge two, three, or more shanks +in different directions. Shanks or needle-rays sometimes simple, +needle-like, sometimes bifurcated or branched. + + +6. _Thalassoxanthium furcatum_, n. sp. + +Spicula all (or nearly all) geminate and simply forked, composed of a +simple axial rod and two simple, needle-like shanks on each end of it. +Shanks straight, pointed, smooth, somewhat shorter than the middle rod. +Central capsule yellowish, dark, three times as broad as its central dark +nucleus; besides this a single oil-globule, nearly of the same size. + +_Dimensions._--Diameter of the central capsule 0.1, of its nucleus 0.03; +length of the axial rod of the spicula 0.04, of its shanks 0.03. + +_Habitat._--Cape Verde Islands. + + +7. _Thalassoxanthium bifurcum_, Haeckel. + + _Thalassosphaera bifurca_, Haeckel, 1862, Monogr. d. Radiol., p. 260, + Taf. xii. fig. 1. + + _Sphaerozoum bifurcum_, Haeckel, 1860, Monatsber. d. k. preuss. Akad. d. + Wiss. Berlin, p. 845. + +Spicula all geminate and double forked, composed of a simple axial rod and +two forked branches on each end; these branches are again forked, so that +each spiculum exhibits eight thin distal ends. All branches are thin, +slender and straight. Central capsule red, four times as broad as the +central nucleus, containing between the red pigment-granules numerous, +peculiar, violin-shaped bodies (fat-corpuscles?). Compare fig. 1, _loc. +cit._ + +_Dimensions._--Diameter of the central capsule 0.08, of the nucleus 0.02, +length of the spicula 0.05 to 0.08. + +_Habitat._--Mediterranean (Messina), surface, Haeckel. + + +{34}8. _Thalassoxanthium ovodimare_, n. sp. + +Spicula all geminate, composed of a simple, very short axial rod and three +diverging shanks or branches on each end of it; the shanks are very thin, +straight, or little curved, and eight to ten times as long as the axial +rod. The spicula are quite smooth, as in the similar _Sphaerozoum +ovodimare_ (in which, however, the axial rod is much longer). Central +capsule transparent, without oil-globules, twice as broad as the nucleus. + +_Dimensions._--Diameter of the capsule 0.4, of the nucleus 0.2, length of +the spicula 0.1 to 0.2. + +_Habitat._--Central Pacific, Station 273, surface. + + +9. _Thalassoxanthium punctatum_, n. sp. + +Spicula all geminate-triradiate, composed of a simple middle rod and of +three diverging shanks on each end of it; the shanks are thorny with small +spinules and shorter than the axial rod, very similar to the common +_Sphaerozoum punctatum_. Central capsule dark, with numerous (twenty to +thirty) oil-globules on the inside of the membrane, three times as broad as +the nucleus. + +_Dimensions._--Diameter of the capsule 0.3, of the nucleus 0.1, length of +the spicula 0.05 to 0.2. + +_Habitat._--Central Pacific, Station 274, surface. + + +10. _Thalassoxanthium octoceras_, n. sp. (Pl. 2, fig. 6). + +Spicula all geminate-quadriradiate, composed of a simple short middle rod +and of four diverging shanks on each end of it; the shanks are quite +smooth, irregularly curved or bent, and four to eight times as long as the +middle rod. Central capsule dark, filled with pigment-granules, without +oil-globules, four times as large as the nucleus. + +_Dimensions._--Diameter of the capsule 0.5, of the nucleus 0.12, length of +the spicula 0.2 to 0.4. + +_Habitat._--Indian Ocean, Madagascar, Rabbe. + + +Genus 9. _Physematium_,[17] Meyen, 1834, Nova Acta Acad. Nat. Curios., vol. +xvi., Suppl., p. 286 (p. 162). + +_Definition._--#Thalassosphaerida# with large numerous alveoles within the +central capsule (not in the calymma), and with numerous simple, +needle-shaped spicula in the calymma. + +The genus _Physematium_ is, together with the colony-forming _Sphaerozoum_, +the first Radiolarian which was observed in the living state, described in +1834 by Meyen. It is most nearly allied to _Thalassolampe_, and has the +same large roundish alveoles within the central capsule, which reaches +therefore an extraordinary size, 5 to 10 mm. It {35}differs from the latter +by the possession of spicula in the calymma. The peculiar "centripetale +Zell-gruppen" on the inside of the capsule-membrane are probably due to +radial cleavages of the endoplasm; as also occurs in other #Collodaria#. + + +1. _Physematium muelleri_, Schneider. + + _Physematium muelleri_, Schneider, 1858, Archiv. f. Anat. u. Physiol., p. + 38, Taf. iii. B, figs. 1-5. + + _Physematium muelleri_, Haeckel, 1862, Monogr. d. Radiol., p. 256, Taf. + iii. figs. 6-9. + +Spherical body limpid, somewhat opalescent, sometimes a little yellowish or +brownish, rather soft. Central capsule with a thin, but firm, transparent +membrane, its diameter eight to ten times as large as that of the central +spherical nucleus. Membrane of the nucleus thick, porous, on its inside +with some nucleoli. In the protoplasmic network between the large +intracapsular alveoles, numerous large, pale, yellowish, or orange +oil-globules. On the inside of the membrane numerous conical bodies, +centripetally directed with the apex towards the centre; every conical body +("kegelfoermige centripetale Zellgruppe") composed of three to nine +(commonly four or five) nucleated cells (mother-cells of the spores?); in +the axis of the cone there is often a yellowish, orange, or brown +oil-globule. Extracapsular jelly-envelope thin, with short pseudopodia. +Xanthellae scarce or wanting. Spicula scattered in the jelly numerous, +small, simple needles, commonly C- or S-like curved, smooth. + +_Dimensions._--Diameter of the whole jelly-sphere 3 to 6 mm., of the +central capsule 1 to 5 mm., of the nucleus 0.1 to 0.5, length of the +spicula 0.05 to 0.1. + +_Habitat._--Mediterranean, Messina; Schneider, Haeckel; surface. + + +2. _Physematium atlanticum_, Meyen. + + _Physematium atlanticum_, Meyen, 1834, Nova Acta Acad. Nat. Curios., vol. + xvi., Suppl., p. 286 (162), Taf. xxxviii. (xxviii.) figs. 1-3. + +Spherical body opalescent, pearl-like, with a violet or purple lustre, very +soft. Central capsule with a strong, semi-transparent membrane, its +diameter six to eight times as large as that of the central spherical +nucleus. Membrane of the nucleus very thick, porous, on its inside with +many small nucleoli. In the protoplasmic network between the alveoles very +numerous, small, purple oil-globules. On the inside of the membrane a +continuous simple layer of small nuclei, enclosed in radially striped +protoplasm (mother-cells of the spores?). No centripetal conical bodies. +Extracapsular jelly-envelope very thin, with short pseudopodia. No +xanthellae. Spicule scattered in the jelly numerous, small needles, +straight or slightly curved, thorny owing to numerous small vertical +spinules. This species and _Thalassolampe maxima_ (p. 17) possess the +largest central capsule. + +_Dimensions._--Diameter of the whole jelly-sphere 8 to 12 mm., of the +central capsule 5 to 10 mm., of the nucleus 1 to 2 mm., length of the +spicula 0.1 to 0.3. + +_Habitat._--Eastern Atlantic, between Canary Islands and Cape Verde +Islands, Meyen; Lanzerote, Haeckel. + + + +{36}Genus 10. _Thalassoplancta_,[18] Haeckel, 1862, Monogr. d. Radiol., p. +261. + +_Definition._--#Thalassosphaerida# with numerous large alveoles in the +calymma (but not in the central capsule), and with numerous simple, +needle-shaped spicula around the central capsule. + +The genus _Thalassoplancta_ was founded by me in 1862 for a Radiolarian +with simple hollow needles in the calymma, which was afterwards recognised +as a Phaeodarium, belonging to _Cannorrhaphis_. We here retain this name +for a true Thalassosphaerid, very similar to the latter, but distinguished +by the absence of the phaeodium and the solid--not hollow--needle-shaped +spicula, which are scattered in the alveolated calymma. _Thalassoplancta_ +can be regarded as the solitary form of the social _Belonozoum_.[19] + + +1. _Thalassoplancta longispicula_, n. sp. + +Spicula long and thin, cylindrical, smooth, more or less bent, pointed at +both ends, similar to those of _Thalassoplancta cavispicula_. Central +capsule thin-walled, without oil-globules, four times as broad as the +nucleus, which encloses one single nucleolus. + +_Dimensions._--Diameter of the capsule 0.6, of the nucleus 0.15, of the +calymma 4 mm. + +_Habitat._--North Atlantic, Faeroee Channel (Gulf Stream), John Murray. + + +2. _Thalassoplancta brevispicula_, n. sp. (Pl. 2, fig. 2). + + _Lampoxanthium brevispiculum_, Haeckel, 1882, Atlas. + +Spicula short and thick, thorny, irregularly curved, pointed at both ends, +very numerous. In the observed specimen all spicula were aggregated in the +outer part of the voluminous calymma, whilst the inner alveolated part was +devoid of them. Central capsule thick walled, with a layer of large +oil-globules on its inner surface, twice as broad as the large nucleus +which contains numerous nucleoli. + +_Dimensions._--Diameter of the central capsule 0.5, of the nucleus 0.2, of +the calymma 2.5. + +_Habitat._--South Atlantic, Station 334, surface. + + +Genus 11. _Lampoxanthium_,[20] n. gen. + +_Definition._--#Thalassosphaerida# with numerous large alveoles in the +calymma (but not in the central capsule), and with numerous branched or +compound spicula in the calymma. + +{37}The genus _Lampoxanthium_ differs from the foregoing, +_Thalassoplancta_, by the composite form of the spicula, which are not +simple needles, but radiate or geminate, or branched in different forms; +the former stands therefore in the same relation to the latter as the +social _Belonozoum_ to _Sphaerozoum_. The spicula of some species of +_Lampoxanthium_ are identical with those of some species of _Sphaerozoum_, +so that the latter may be derived from the former by forming colonies. The +large central capsule is enveloped by a very voluminous alveolated calymma, +and includes a large central nucleus with numerous nucleoli. + + +Subgenus 1. _Lampoxanthella_, Haeckel. + +_Definition._--Spicula all (or nearly all) of one kind, radiate. + + +1. _Lampoxanthium tetractinium_, n. sp. + +Spicula all (or nearly all) tetraradiate, with four thorny, straight, +pointed shanks, radiating from one common point. (Intermingled with these +are often some few, thorny, triradiate spicula.) On the inside of the +capsule a layer of large oil-globules as in _Thalassoplancta_, Pl. 2, fig. +2. + +_Dimensions._--Diameter of the central capsule 0.2, of the nucleus 0.08, of +the calymma 0.8. + +_Habitat._--South Pacific, Station 288, surface. + + +Subgenus 2. _Lampoxanthomma_, Haeckel. + +_Definition._--Spicula all (or nearly all) of one kind, geminate-radiate, +with a simple middle rod and two to four diverging shanks on each end of +it. + + +2. _Lampoxanthium punctatum_, n. sp. + +Spicula all geminate-triradiate, thorny, of the same form as in the common +_Sphaerozoum punctatum_, of which this species is the large solitary +representative. The spicula are aggregated in a very condensed layer on the +surface of the large calymma. + +_Dimensions._--Diameter of the capsule 0.8, of the nucleus 0.6, of the +calymma 2.0. + +_Habitat._--North Pacific, Station 248, surface. + + +3. _Lampoxanthium octoceras_, n. sp. + +Spicula all geminate-quadriradiate, with a very short simple middle rod and +four very long divergent shanks on both ends of it; the shanks are smooth, +five to ten times as long as the middle {38}rod, irregularly bent and +curved. (Differs from the similar _Thalassoxanthium octoceras_, Pl. 2, fig. +6, by slender, more curved shanks, and by the voluminous calymma, there +entirely wanting.) + +_Dimensions._--Diameter of the capsule 0.5, of the nucleus 0.2, of the +calymma 3.0. + +_Habitat._--South Atlantic, Station 331, surface. + + +Subgenus 3. _Lampoxanthura_, Haeckel. + +_Definition._--Spicula of two or three different kinds, simple, radiate, +and geminate-radiate mixed. + + +4. _Lampoxanthium pandora_, n. sp. (Pl. 2, fig. 1). + +Spicula mixed, of three different kinds--simple, radiate and +geminate-radiate; all three kinds partly smooth, partly thorny. The simple +needles short, thin spindle-shaped, often curved. The radiate spicula +commonly with three or four, rarely five or six, unequal rays, straight or +curved. The radiate-geminate spicula commonly with three, rarely four, +shanks on each end, often different on both ends of the middle rod. The +size, number, and form of the irregular spicula are here quite as variable +as in the social _Rhaphidozoum pandora_, of which it is the solitary +representative. The wall of the large central capsule is very thick, with +evident pore-canals, separated by a clear interval from the coagulated and +vacuolated endoplasm, which contains no oil-globules. Nucleus with numerous +nucleoli. + +_Dimensions._--Diameter of the central capsule 0.5 to 0.6, of the nucleus +0.1 to 0.2, of the calymma 2 to 4 mm. + +_Habitat._--North Pacific, Station 244, surface. + + + +Family IV. #SPHAEROZOIDA#, Haeckel (Pl. 4). + +_Sphaerozoida_, Haeckel, 1862, Monogr. d. Radiol., p. 521. + +_Definition._--#Beloidea# socialia. + +The family #Sphaerozoida# comprises all associated or colony-forming +Radiolaria, which are provided with an imperfect skeleton, composed of +numerous solid needles or spicula, scattered around the central capsule in +the calymma. The structure and form of this skeleton is quite the same as +in the preceding solitary Thalassosphaerida, but on the other hand, the +structure and form of the colonies and of the included numerous central +capsules is the same as in the skeletonless Collozoida. + +The oldest well-known form of Sphaerozoida is the common cosmopolitan +_Sphaerozoum punctatum_, probably first observed in 1834 by Meyen, and +called _Sphaerozoum fuscum_, afterwards more accurately described by Huxley +in 1851. + +{39}Other forms were afterwards described by Mueller and by myself in +1862.[21] Further investigations have shown me that some species of this +family are among the most common Radiolaria, and occur in astonishing +numbers on the surface of all warmer seas. But the number of species is +comparatively small, and their distinction is very difficult, as all the +different forms are very variable and connected by intermediate forms--a +truly "_transformistic_" group. + +The only character sufficient for the constitution of genera in this +transformistic group is found in the form and composition of the spicula; +the very variable form of the jelly-calymma and the enclosed central +capsule being without value for this purpose. But also the form of the +spicula is very variable, and not always constant. In some species the +particular form of the spicula is transmitted by constant heredity, whilst +in others it is very inconstant, even in one and the same individual. +(Compare the remarks on variability in the general introduction.) + +As the number of various forms is rather great, it seems to be advisable to +distinguish the three following genera. + +_Synopsis of the Genera of Sphaerozoida._ + + A. Spicula all of one kind, simple or needle-shaped, 12. _Belonozoum_. + B. Spicula all of one kind, branched or radiate, + or geminate, 13. _Sphaerozoum_. + C. Spicula of two more different kinds, partly + simple, partly branched, 14. _Rhaphidozoum_. + + +Genus 12. _Belonozoum_,[22] n. gen. + +_Definition._--#Sphaerozoida# with simple needle-shaped spicula, which are +neither radiate nor branched. + +The genus _Belonozoum_ comprises the Sphaerozoida with simple needle-shaped +spicula, and may be regarded as the colonial form of _Thalassosphaera_ or +_Thalassoplancta_, derived from these solitary #Beloidea# by multiplication +of the capsules and union in a common calymma. + + +1. _Belonozoum bacillosum_, n. sp. + + _Sphaerozoum bacillosum_, Haeckel, 1881, Manuscript. + +Spicula all simple rods, straight cylindrical, obtuse at both ends, quite +smooth. Central capsule pellucid, with one single central oil-globule. + +_Dimensions._--Diameter of the central capsule 0.08 to 0.12, length of the +spicula 0.05 to 0.08. + +_Habitat._--Central Pacific, Station 271, surface. + + +{40}2. _Belonozoum spinulosum_, Haeckel. + + _Sphaerozoum spinulosum_, J. Mueller, 1858, Abhandl. d. k. Akad. d. Wiss. + Berlin, p. 54, Taf. viii. fig. 4. + + _Sphaerozoum spinulosum_, Haeckel, 1862, Monogr. d. Radiol., p. 527, Taf. + xxxiii. figs. 3, 4. + +Spicula all simple rods, straight cylindrical, obtuse on both ends, thorny +with numerous small spines, placed vertically on the rods. + +_Dimensions._--Diameter of the central capsule 0.08 to 0.1, length of the +spicula 0.05 to 0.2. + +_Habitat._--Mediterranean, Nice, J. Mueller; Messina, Haeckel; Naples, +Brandt; surface. + + +3. _Belonozoum italicum_, Haeckel. + + _Sphaerozoum italicum_, Haeckel, 1862, Monogr. d. Radiol., p. 526, Taf. + xxxiii. figs. 1, 2. + +Spicula all simple rods, more or less curved or bent, pointed at both ends, +quite smooth. Central capsule with a variable number (commonly five to +twenty) of oil-globules. + +_Dimensions._--Diameter of the central capsule 0.1 to 0.3, length of the +spicula 0.05 to 0.2. + +_Habitat._--Mediterranean, Nice, Naples, Messina, Haeckel, surface. + + +4. _Belonozoum atlanticum_, n. sp. + + _Sphaerozoum atlanticum_, Haeckel, 1881, Manuscript. + +Spicula all together simple rods, more or less curved or bent, pointed at +both ends, thorny from numerous small spines, placed vertically on the +rods. + +_Dimensions._--Diameter of the central capsule 0.1 to 0.2, length of the +spicula 0.07 to 0.15. + +_Habitat._--Tropical Atlantic, Station 348, surface. + + +Genus 13. _Sphaerozoum_,[23] Meyen, 1834, Nova Acta Acad. Nat. Curios., Bd. +xvi., Suppl., p. 287 (p. 163). + +_Definition._--#Sphaerozoida# with branched or radiate spicula of one kind. + +The genus _Sphaerozoum_, with _Physematium_ one of the two oldest +Radiolaria, observed in the living state, was founded 1834 by Meyen for one +of the social #Beloidea#, which was probably the common cosmopolitan +_Sphaerozoum punctatum_, the true type of this genus. Johannes Mueller +described a number of species, which were partly skeletonless +(_Collozoum_), partly armed with simple or with compound spicula. The +species with simple spicula we refer here to _Belonozoum_, the species with +two or more different kinds of spicula to _Rhaphidozoum_, while we unite in +_Sphaerozoum_ all species with one kind of branched or compound spicula. +The two following species are incompletely known:--_Sphaerozoum orientale_, +Dana, 1863, _Ann. and Mag. Nat. Hist._, vol. xii. p. 54. _Sphaerozoum +sanderi_, Doenitz, 1871, L. N. 60, p. 71. + + +{41}Subgenus 1. _Sphaerozonactis_, Haeckel. + +_Definition._--Spicula radiate, not geminate, consisting of three, four, or +more needles or shanks, radiating in different directions from one common +central point. + + +1. _Sphaerozoum triactinium_, n. sp. + +Spicula all (or nearly all) triradiate, composed of three (or sometimes in +few spicula four) needle-like shanks, diverging from one common point. +Shanks straight or somewhat curved, smooth, pointed. Central capsules +spherical, with one central oil-vesicle. This species may be regarded as +the social form of _Thalassoxanthium triactinium_. + +_Dimensions._--Diameter of the central capsules 0.1 to 0.12, length of the +spicula-shanks 0.05 to 0.1. + +_Habitat._--South Pacific, Station 295, surface. + + +2. _Sphaerozoum medusinum_, n. sp. + +Spicula all (or nearly all) quadriradiate, composed of four (or sometimes +in few spicula three) needle-like shanks (mostly of unequal length), +diverging from one common point. Shanks slightly curved, pointed, thorny, +covered with small spinules. Central capsules ellipsoidal, containing +several (four to eight) oil-vesicles. This species may be regarded as the +social form of the solitary _Thalassoxanthium medusinum_ (Pl. 2, fig. 5). + +_Dimensions._--Diameter of the central capsules 0.15 to 0.18, length of the +spicula-shanks 0.08 to 0.12. + +_Habitat._--North Pacific, Station 236, surface. + + +3. _Sphaerozoum hamatum_, n. sp. + +Spicula all (or nearly all) quadriradiate, composed of four (or sometimes +in few spicula three) needle-like shanks, mostly of very different size, +diverging from one common point. Shanks strong, straight, curved, or +hook-like; thorny, covered with small spinules on the distal extremity. +Central capsules ellipsoidal, large, containing many (ten to twenty) +oil-globules. This large species is distinguished by the very irregular +form and size of the spicula. + +_Dimensions._--Diameter of the central capsules 0.2 to 0.25, length of the +spicula-shanks 0.12 to 0.18. + +_Habitat._--Central Pacific, Station 265, surface. + + +4. _Sphaerozoum hexactinium_, n. sp. + +Spicula all (or nearly all) hexaradiate, composed of six (or sometimes in +few spicula five or seven) needle-like shanks, mostly of equal size, +diverging from one common point in two opposite hemispheres (three needles +upwards, three needles downwards). Shanks somewhat curved, pointed, +{42}smooth. Central capsules spherical, small, with one central +oil-globule. This species may be regarded as the social form of +_Thalassoxanthium hexactinium_. + +_Dimensions._--Diameter of the central capsule 0.06 to 0.08, length of the +spicula-shanks 0.05 to 0.06. + +_Habitat._--North Atlantic, Faeroee Channel (Gulf Stream), John Murray. + + + +Subgenus 2. _Sphaerozonoceras_, Haeckel. + +_Definition._--Spicula all geminate-radiate, consisting of one middle rod, +which bears an equal and constant number of rays (two, three, or four) at +each end. + + +5. _Sphaerozoum furcatum_, n. sp. + +Spicula all (or nearly all) geminate and simply forked, composed of a +simple axial rod and two simple needle-like shanks on each end of it. +Shanks straight, pointed, smooth, commonly somewhat longer than the middle +rod. + +_Dimensions._--Diameter of the central capsules 0.1 to 0.15, length of the +axial rod of the spicula 0.03, of its shanks 0.04 to 0.06. + +_Habitat._--Tropical zone of the Atlantic, near Ascension Island, Station +344, surface. + + +6. _Sphaerozoum furculosum_, n. sp. + +Spicula all (or nearly all) geminate and simply forked, composed of a +simple axial rod and two simple needle-like shanks on each end of it. +Shanks curved or bent, pointed, thorny, with many small spinules, commonly +somewhat shorter than the middle rod. + +_Dimensions._--Diameter of the central capsules 0.2 to 0.25, length of the +axial rod of the spicula 0.1, of its shanks 0.05 to 0.08. + +_Habitat._--South Atlantic, near Tristan da Cunha, Station 334, surface. + + +7. _Sphaerozoum ovodimare_, Haeckel. + + _Sphaerozoum ovodimare_, Haeckel, 1862, Monogr. d. Radiol., p. 527, Taf. + xxxiii. figs. 5, 6. + + _Sphaerozoum punctatum_, var., Brandt, 1881, Monatsber. d. k. preuss. + Akad. d. Wiss. Berlin, Taf. i. fig. 54. + + +Spicula all (or nearly all) geminate and triradiate, composed of a long +simple axial rod and three simple needle-like shanks on each end of it. +Shanks straight, pointed, smooth, commonly shorter than the middle rod. +(Often few furcate or four-rayed spicula are intermixed, or few spicula are +not smooth, but thorny.) + +_Dimensions._--Diameter of the central capsules 0.05 to 0.2, length of the +middle rod of the spicula 0.02 to 0.06, of its shanks 0.01 to 0.04. + +_Habitat._--Mediterranean, Naples, Messina, Haeckel; Atlantic, Canary +Islands, Cape Verde Islands, West Coast of Africa, Stations 351 to 354; +surface. + + +{43}8. _Sphaerozoum trigeminum_, n. sp. + +Spicula all (or nearly all) geminate-triradiate, composed of a short simple +axial middle rod and three simple needle-like shanks on each end of it. +Shanks curved or bent, very thin, smooth, commonly much longer than the +middle rod. (Often few quadriradiate or few thorny triradiate spicules are +interspersed among the others.) + +_Dimensions._--Length of the middle rod of the spicula 0.02 to 0.04, of its +shanks 0.03 to 0.09. + +_Habitat._--North Pacific, Stations 244 to 248, surface. + + +9. _Sphaerozoum punctatum_, J. Mueller. + + _Sphaerozoum punctatum_, J. Mueller, 1858, Abhandl. d. k. Akad. d. Wiss. + Berlin, p. 54, Taf. viii. figs. 1, 2. + + _Sphaerozoum punctatum_, Haeckel, 1862, Monogr. d. Radiol., p. 528, Taf. + xxxiii. figs. 7-9. + + _Sphaerozoum fuscum_, Meyen, 1834, Nova Acta Acad. Nat. Cur., vol. xvi. + Taf. xxxviii. fig. 7. + + _Thalassicolla punctata_, Huxley, 1851, Ann. and Mag. Nat. Hist., ser. 2, + vol. viii. p. 434, pl. xvi. figs. 1, 2, 3. + +Spicula all (or nearly all) geminate-triradiate, composed of a long simple +axial middle rod and three simple needle-like shanks on each end of it. +Shanks straight, pointed, thorny, with many small spines, commonly somewhat +shorter than the middle rod. (Often few furcate or four-rayed spicula are +intermingled, or some of the spicula are smooth.) This cosmopolitan species +is extremely variable, and produces interesting transitional forms to many +other species of the genus. Compare also the general remarks on the genus, +and the chapter on "Transformation" in the general introduction. + +_Dimensions._--Length of the middle rod of the spicula 0.02 to 0.06, of its +shanks 0.01 to 0.05. + +_Habitat._--Cosmopolitan, common in nearly all warmer seas, Mediterranean, +Atlantic, Indian Ocean, Pacific; surface. + + +10. _Sphaerozoum armatum_, n. sp. (Pl. 4, fig. 9). + +Spicula all geminate-triradiate, with a stout and short middle rod and +three arborescent shanks on each end of it. Shanks longer than the middle +rod, very stout, straight, pine-shaped, with six to twelve irregular, +spinulated, lateral branches. + +_Dimensions._--Diameter of the central capsules 0.04 to 0.08, length of the +middle rod of the spicula 0.02 to 0.03, of its shanks 0.05 to 0.08. + +_Habitat._--North Pacific, Japan, Station 239, surface. + + +11. _Sphaerozoum alveolatum_, n. sp. (Pl. 4, figs. 2, 3). + +Spicula all together geminate-triradiate, with a simple stout middle rod +and three arborescent shanks on each end of it. Shanks more or less curved, +slender, pine-shaped, with four to eight short, thorny lateral branches. In +all coenobia of this remarkable species the central capsules are enclosed +in large thick-walled alveoles (of three times their breadth), and in each +alveole is placed besides {44}the capsule one single very large spiculum, +whilst the others are much smaller (fig. 3). All the alveolated capsules +are placed in one single stratum on the surface of the jelly-like spherical +coenobium, comparable to the blastoderm-cells of a blastula. + +_Dimensions._--Diameter of the central capsules 0.08 to 0.1, of the +alveoles 0.2 to 0.4, length of the spicula 0.1 to 0.3. + +_Habitat._--South Pacific (Juan Fernandez), Station 300, surface. + + +12. _Sphaerozoum verticillatum_, n. sp. (Pl. 4, fig. 7). + +Spicula all geminate-triradiate, with a short simple middle rod and three +much longer arborescent shanks on each end of it. Shanks straight, slender, +pine-shaped, each in the distal half with three to four elegant verticils +of thorny lateral branches. + +_Dimensions._--Diameter of the capsules 0.1 to 0.12, middle rod of the +spicula 0.03 to 0.05, shanks 0.1 to 0.15. + +_Habitat._--Indian Ocean, Ceylon, Haeckel; Madagascar, Rabbe; surface. + + +13. _Sphaerozoum octoceras_, n. sp. + +Spicula all geminate-quadriradiate, with a short simple middle rod and four +diverging shanks on each end of it. Shanks smooth, irregularly curved or +bent, three to six times as long as the middle rod. It may be regarded as +the social form of _Thalassoxanthium octoceras_ (Pl. 2, fig. 6). + +_Dimensions._--Diameter of the capsules 0.12 to 0.16, middle rod of the +spicula 0.02, shanks 0.01. + +_Habitat._--Australia, south coast, Faber; Station 163, surface. + + +14. _Sphaerozoum quadrigeminum_, n. sp. + +Spicula all geminate-quadriradiate, with a long thick middle rod and four +shorter diverging shanks on each end of it. Shanks straight, thorny. + +_Dimensions._--Diameter of the capsules 0.06 to 0.08, length of the spicula +0.05 to 0.15. + +_Habitat._--North Atlantic, Azores, Station 354, surface. + + +15. _Sphaerozoum araucaria_, n. sp. + +Spicula all geminate-quadriradiate, with stout straight middle rod and four +longer diverging shanks on each end of it. Shanks arborescent, with six to +twelve thorny lateral branches. + +_Dimensions._--Diameter of the capsules 0.1 to 0.15, length of the spicula +0.05 to 0.1. + +_Habitat._--South Atlantic, coast of Brazil, Rabbe; surface. + + +16. _Sphaerozoum arborescens_, n. sp. (Pl. 4, fig. 8). + +Spicula all geminate-quadriradiate, with a stout straight middle rod and +four longer diverging shanks on each end of it. Shanks arborescent, +pine-shaped, with four to six verticils of lateral branches, which again +are ramified and thorny. + +{45}_Dimensions._--Diameter of the capsules 0.16 to 0.18, length of the +spicula 0.1 to 0.2. + +_Habitat._--South Atlantic (Tristan da Cunha), Station 332, surface. + + + +Subgenus 3. _Sphaerozonura_, Haeckel. + +_Definition._--Spicula all geminate-radiate, but with a different and +variable number of shanks on each end of the middle rod. + + +17. _Sphaerozoum stellatum_, n. sp. + +Spicula all geminate-radiate, with a strong middle rod and a variable +number of shorter radiating shanks on the two ends of it. Shanks straight, +nearly conical, smooth; for the most part three or four shanks on each end, +but sometimes also five or six; very often this number is unequal on the +two ends. + +_Dimensions._--Diameter of the central capsules 0.1 to 0.2, length of the +spicula 0.05 to 0.15. + +_Habitat._--Central Pacific, Station 270, surface. + + +18. _Sphaerozoum geminatum_, n. sp. (Pl. 4, fig. 4). + +Spicula all geminate-radiate, with a strong middle rod and a variable +number of longer radiant shanks on each end of it. Shanks straight, +conical, in the distal half thorny; commonly either three or four shanks on +each end of the middle rod, often also three on one end, four on the other +end; rarely five or six rays on one end. + +_Dimensions._--Diameter of the capsules 0.15 to 0.2, length of the spicula +0.05 to 0.1. + +_Habitat._--Indian Ocean, Ceylon, Haeckel; surface. + + +19. _Sphaerozoum circumtextum_, n. sp. + +Spicula all geminate-radiate, with a very variable number of rays (two to +six) on each end of the thin middle rod. All spicula very thin and +delicate, smooth, with curved or bent shanks, densely covering the central +capsule like a cobweb. The number of rays on each end is usually different, +generally four or five, often also two or three, rarely six. + +_Dimensions._--Diameter of the capsule 0.1 to 0.2, length of the spicula +0.04 to 0.12. + +_Habitat._--Southeast part of the Indian Ocean, Station 160, surface. + + +20. _Sphaerozoum variabile_, n. sp. (Pl. 4, fig. 5). + +Spicula all geminate-radiate, with a short middle rod and a variable number +of shanks on each end of it. Shanks four to eight times as long as the +middle rod, curved or bent, in the distal half thorny; their number is +commonly different on the two ends of it, three or five, often also four or +six, rarely two; their size and form very variable. + +{46}_Dimensions._--Diameter of the capsules 0.1 to 0.3, length of the +spicula 0.1 to 0.2. + +_Habitat._--North Pacific, Station 248, surface. + + + +Genus 14. _Rhaphidozoum_,[24] Haeckel, 1862, Monogr. d. Radiol., p. 529. + +_Definition._--Sphaerozoida with two or more different kinds of spicula; +one kind simple, needle-shaped; the other kinds compound, radiate, or +branched. + +The genus _Rhaphidozoum_ differs from _Sphaerozoum_ by the composition of +the skeleton of two or more different kinds of spicula, and has therefore +the same relation to it as the solitary _Lampoxanthura_ to +_Lampoxanthella_. + +In some species nearly all the different forms, which characterise the +numerous species of #Beloidea#, may be united in one and the same +individual. + + + +Subgenus 1. _Rhaphidonactis_, Haeckel. + +_Definition._--Spicula of two different kinds; one kind simple, +needle-shaped, the other radiate (composed of three, four, or more shanks, +diverging from one common point). + + +1. _Rhaphidozoum pelagicum_, n. sp. + +Spicula of two different kinds; one kind simple thin needles, a little +curved or bent, the other kind triradiate, with three thin, curved shanks. +Both kinds smooth, without thorns. Resembles a combination of _Belonozoum +italicum_ and _Sphaerozoum triactinium_. + +_Dimensions._--Diameter of the central capsules 0.1 to 0.12, length of the +spicula 0.05 to 0.15. + +_Habitat._--Central Pacific, Station 267, surface. + + +2. _Rhaphidozoum pacificum_, n. sp. + +Spicula of two different kinds; one kind simple needles, stout and +straight, pointed at both ends, the other kind triradiate, with three +straight and stout shanks. Both kinds thorny. + +_Dimensions._--Diameter of the central capsule 0.06 to 0.08, length of the +spicula 0.05 to 0.1. + +_Habitat._--Central Pacific, Station 271, surface. + + +3. _Rhaphidozoum acuferum_, Haeckel. + + _Rhaphidozoum acuferum_, Haeckel, 1862, Monogr. d. Radiol., p. 529, Taf. + xxxii. figs. 9-11. + + _Sphaerozoum acuferum_, J. Mueller, 1858, Abhandl. d. k. Akad. d. Wiss. + Berlin, p. 54, Taf. viii. fig. 3. + + _Thalassicolla acufera_, J. Mueller, 1855, Monatsber. d. k. preuss. Akad. + d. Wiss. Berlin, p. 237. + +Spicula of two different kinds, simple needles and quadriradiate; both +strong, thorny, covered with small spinules. Simple needles mostly curved, +C-shaped. Four shanks of the quadriradiate {47}spicula now straight, now +curved, commonly of very different size. (Often one single quadriradiate +spiculum is distinguished by its extraordinary size.) For the detailed +description of this species compare my Monograph (_loc. cit._). + +_Dimensions._--Diameter of the central capsules 0.05 to 0.35, length of the +simple needles 0.05 to 0.25, shanks of the quadriradiate spicula 0.05 to +0.15. + +_Habitat._--Mediterranean, Messina, Naples, Nice. + + +4. _Rhaphidozoum arachnoides_, n. sp. + +Spicula of two different kinds; one kind simple, needle-like, the other +quadriradiate; both very thin and slender, smooth, without spicules. Simple +needles curved, C-shaped. Four shanks of the quadriradiate spicula also +curved, commonly of nearly equal size. The numerous thread-like spicula of +this species are so densely packed around the central capsule, that they +extend all around its surface like the network round a balloon. + +_Dimensions._--Diameter of the central capsules 0.12 to 0.15, length of the +simple needles 0.1 to 0.12, shanks of the quadriradiate spicula 0.06 to +0.08. + +_Habitat._--Tropical Atlantic, Station 345, surface. + + +5. _Rhaphidozoum asperum_, n. sp. + +Spicula of two different kinds; one kind simple, needle-shaped, stout, and +straight, the other kind hexaradiate; its six shanks about half as long as +the former, conical. Both kinds very thorny, covered with short conical +spinules. + +_Dimensions._--Diameter of the capsules 0.06 to 0.08, length of the simple +needles 0.05 to 0.07, shanks of the hexaradiate spicula 0.03 to 0.04. + +_Habitat._--South Pacific, Station 288, surface. + + + +Subgenus 2. _Rhaphidoceras_, Haeckel. + +_Definition._--Spicula of two different kinds; one kind simple, +needle-shaped, the other kind geminate-radiate, with rays on both poles of +a middle rod. + + +6. _Rhaphidozoum neapolitanum_, Haeckel. + + _Sphaerozoum neapolitanum_, C. Brandt, 1881, Monatsber. d. k. preuss. + Akad. d. Wiss. Berlin, p. 390, Taf. i. figs. 14, 16-18. + +Spicula mixed, of two different kinds; simple needles and geminate-forked. +Simple rods, like those of _Belonozoum italicum_, more or less curved, +pointed at both ends, smooth (sometimes a little thorny at both ends). +Geminate spicula simply forked, like those of _Sphaerozoum furcatum_, +composed of a short, simple, axial rod, and two simple, smooth, straight +shanks on each end of it, commonly somewhat longer than the middle rod. +This species, which I have observed myself in Spezzia in great quantity, is +quite as variable as all the other species of the genus, and has not more +claim to specific rights than the others. Commonly the simple needles are +much more numerous {48}than the geminate-forked, but sometimes the contrary +is the case. On their variability compare the general remarks on the genus, +and the chapter on "Transformation" in the general introduction. + +_Dimensions._--Length of the simple spicula 0.05 to 0.1, of the middle rod +of the forked spicule 0.05 to 0.08, of their shanks 0.01 to 0.03. + +_Habitat._--Mediterranean, Naples, Spezzia, surface. + + +7. _Rhaphidozoum patagonicum_, n. sp. + +Spicula mixed, of two different kinds, simple needles and +geminate-triradiate. Simple rods, like those of _Belonozoum spinulosum_, +straight, thorny, pointed at both ends. Geminate spicula double-triradiate, +like those of _Sphaerozoum punctatum_, composed of a simple, short, axial +rod and three simple pointed shanks on each end of it. Shanks straight, +thorny, with many small spinules, commonly somewhat longer than the middle +rod. (Often some of the spicula of both kinds are smooth, not thorny, or +not straight, but a little curved, or a few forked or four-radiated +geminate spicula are mingled with the others.) + +_Dimensions._--Diameter of the central capsules 0.08 to 0.2, length of the +simple spicula 0.1 to 0.15, of the geminate 0.08 to 0.16. + +_Habitat._--South Pacific, west coast of Patagonia, Station 302, surface. + + +8. _Rhaphidozoum ascensionis_, n. sp. + +Spicula mixed, of two different kinds, simple needles and +geminate-triradiate; both kinds thin, smooth, without spinules. Simple +needles somewhat curved, C- or S-shaped. Geminate spicula +double-triradiate, composed of a simple, short, straight axial rod and +three slender curved shanks on each end of it. Shanks two to four times +longer than the middle rod. (Sometimes few simple hexaradiate and geminate +tetraradiate spicula are mingled.) + +_Dimensions._--Diameter of the central capsules 0.12 to 0.15, length of the +simple spicula 0.1, of the double-triradiate 0.05 to 0.2. + +_Habitat._--South Atlantic, off Ascension Island, Station 342, surface. + + +9. _Rhaphidozoum capense_, n. sp. + +Spicula of two different kinds; one kind simple, needle-shaped, straight, +pointed at both ends, the other kind geminate-quadriradiate, with a stout +short middle rod and four longer bent shanks on each end of it. Both kinds +smooth. + +_Dimensions._--Diameter of the capsules 0.2 to 0.25, length of the simple +needles 0.01 to 0.3, of the geminate spicula 0.05 to 0.15. + +_Habitat._--Cape of Good Hope (Agulhas), Station 142, surface. + + +10. _Rhaphidozoum australe_, n. sp. + +Spicula of two different kinds; one kind simple, needle-shaped, curved, +thin; the other kind geminate, with a variable number of shanks on both +ends of the shorter middle rod, often {49}different on the two poles of it. +The prevalent number of rays on each end is three or four, often also two +or five, rarely six. All spicula smooth, more or less bent. + +_Dimensions._--Diameter of the capsules 0.1 to 0.2, length of the spicula +0.05 to 0.15. + +_Habitat._--South West Pacific, Station 165, surface. + + + +Subgenus 3. _Rhaphidonura_, Haeckel. + +_Definition._--Spicula of three different kinds: one kind simple, +needle-shaped; the second kind radiate, with three to six shanks radiating +from a common central point; the third kind geminate-radiate, with rays on +both poles of a middle rod. + + +11. _Rhaphidozoum polymorphum_, n. sp. + +Spicula of three different kinds; simple needles, radiate, and geminate +mixed. The simple needles straight and stout. The radiate spicula commonly +with three or six, rarely four or five, rays. The geminate-radiate spicula +prevalent, with three or four, rarely two or five, shanks on each end of +the middle rod. Number very variable. All shanks straight and smooth. + +_Dimensions._--Diameter of the capsule 0.1 to 0.2, length of the spicula +0.05 to 0.15. + +_Habitat._--South Pacific, Station 295, surface. + + +12. _Rhaphidozoum pandora_, n. sp. (Pl. 4, fig. 6). + +Spicula of three different kinds; simple needles, radiate and geminate +mixed. The simple needles thin spindle-shaped, often curved. The radiate +spicula commonly with three or four, rarely five or six, curved rays. The +geminate-radiate spicula commonly with three or four, rarely two or five, +shanks on each end, often different on the two ends of the middle rod. +Number and form very variable. All or most of the shanks more or less bent +and thorny. + +_Dimensions._--Diameter of the capsule 0.1 to 0.3, length of the spicula +0.05 to 0.2. + +_Habitat._--South Atlantic (near Ascension Island), Station 343, surface. + + +---- + + +Order II. SPHAERELLARIA, Haeckel, 1881. + + _Sphaerellaria_, Haeckel, 1881, Prodromus, p. 421. + _Sphaeridea_ vel _Peripylea_, Hertwig, 1879, Organismus der Radiol., p. + 133. + +_Definition._--SPUMELLARIA with latticed or spongy shell. + +The order #Sphaerellaria#, the second order of Radiolaria, comprises all +those SPUMELLARIA in which the skeleton is a latticed or fenestrated, often +more or less spongy, siliceous shell. Originally this shell is a simple +extracapsular lattice-sphere, in which the central capsule is included; +from this simple ancestral form an enormous {50}mass of different and often +very complicated forms is derived; this order is by far the largest, and in +morphological respects the most important and most interesting, of all +Radiolaria. It contains not less than twenty-eight different families, +three hundred and five genera, and more than sixteen hundred species. + +In my Monograph (1862) seven families appertaining to this group are +described--the Ethmosphaerida, Cladococcida, Ommatida, Spongurida, Discida, +Lithelida, and Collosphaerida. The astonishing increase of this group by +the detection of a large series of new and interesting forms, and +particularly of important connecting forms between very different branches +of it, now enables me to give a much better arrangement. I discern now four +suborders or sections of #Sphaerellaria#, according to the different +geometrical form of the central capsule and of the latticed shell +enveloping it. The first of these, and the common ancestral group of the +whole order, is the #Sphaeroidea#, with spherical capsule; in the +#Prunoidea# it becomes ellipsoidal or cylindrical by prolongation of one +axis; in the #Discoidea# lenticular or discoidal by shortening of one axis; +in the #Larcoidea# lentelliptical, or triaxon-ellipsoid, by different +growth of the capsule in three different "dimensive axes." + +_Synopsis of the Four Suborders of_ #Sphaerellaria#. + + Central capsule { Shell a simple sphere or a + spherical. { system of concentric spheres, 1. #Sphaeroidea#. + + Central capsule { Shell a simple ellipsoid or a + ellipsoidal or { cylinder with annular + cylindrical. { transverse constrictions, 2. #Prunoidea#. + + Central capsule + lenticular or { Shell a biconvex lens or a + discoidal. { flat disk, 3. #Discoidea#. + + Central capsule + lentelliptical or { Shell a triaxon-ellipsoid, with + triaxon. { three different axes, 4. #Larcoidea#. + + +---- + + +Suborder I. SPHAEROIDEA, Haeckel. + + _Sphaeroida_, _Sphaeridea_, _Sphaerida_, Haeckel, 1878, Protistenreich, + p. 103. + _Sphaeridea_, R. Hertwig, 1879, Organismus der Radiol., p. 39. + +_Definition._--SPUMELLARIA with spherical central capsule (very rarely +somewhat modified, or allomorphous); with spherical fenestrated siliceous +shell (often an endospherical polyhedron, very rarely of more modified, +subspherical form or allomorphous). Growth of the shell in the three +dimensive axes equal. + +The suborder #Sphaeroidea#, the first and most important of the four of the +#Sphaerellaria#, comprises those SPUMELLARIA in which the original +geometrical {51}spherical form is quite constantly preserved in the central +capsule, and commonly also in the fenestrated shell enveloping the latter, +although in many forms the sphere is more or less modified; very frequently +it is an "endospherical polyhedron," _i.e._, a polyhedron all the angles +(or the nodes of the network) of which lie upon the surface of a +geometrical sphere; more rarely the spherical form is more or less modified +and irregular. In the great majority of #Sphaeroidea# there is no external +indication of the three dimensive axes; but in many forms they are +indicated by the regular position of certain external radial spines or +internal radial beams. However, in no case are those three axes expressed +in the form of the shell itself and of the enclosed spherical central +capsule; this is the main character by which the #Sphaeroidea# differ from +the following sections:--#Prunoidea#, #Discoidea#, #Larcoidea#, all three +of which arise from them. + +The section #Sphaeroidea#, in the sense here restricted, was founded by me +in my Protistenreich (1878, p. 103) and adopted by Hertwig (1879) in his +Organismus der Radiolarien (p. 39). The different groups appertaining to +this large section were characterised more accurately in my Prodromus +(1881, pp. 448-456); there I gave the characters of six subfamilies with +thirty tribes, containing ninety-three genera. Formerly, in my Monograph +(1862), the #Sphaeroidea# were disposed in five different +families:--Ethmosphaerida, Cladococcida, Ommatida, Spongosphaerida, +Collosphaerida. At that time I could not separate them sufficiently from +some ACANTHARIA and PHAEODARIA, which have a similar spherical +lattice-shell. + +As the number of different genera and species in the #Sphaeroidea# is much +greater than in all other sections of SPUMELLARIA, many forms were already +described by former authors. In the oldest system of Ehrenberg (1847, _loc. +cit._, p. 53) they represent one part of his Haliommatina (with four +genera, _Haliomma_, _Chilomma_, _Stylosphaera_, _Spongosphaera_). Most +species, however, of these genera are #Discoidea#. Also in the latest +system of Ehrenberg (1875, _loc. cit._, p. 157) his Haliommatina are a +confused conglomeration of different SPUMELLARIA (#Sphaeroidea#, +#Discoidea#, and #Prunoidea#). + +The section #Sphaeroidea# is the largest division of #Sphaerellaria#, +comprising not less than one hundred and seven genera and six hundred and +fifty species. This enormous number (easily to be augmented by further +investigations) requires a careful disposition in different families and +subfamilies. For this disposition two different principles only can be +employed: firstly, the number and disposition of the _radial spines_; +secondly, the number of the _concentric latticed spheres_, which are +connected by radial beams. I give here the preference to the first +principle, whilst in my Prodromus (1881) I had preferred the second. The +question, which of the two principles is more important for the +classification of #Sphaeroidea#, is very difficult to answer; probably in +many cases the former, in many the latter is more important for their +phylogeny. + +{52}Regarding the number of the concentric shells which compose the +latticed carapace of the #Sphaeroidea#, we can distinguish six families, +viz.:-- + + I. Monosphaerida (with one single shell). + II. Dyosphaerida (with two concentric shells). + III. Triosphaerida (with three concentric shells). + IV. Tetrasphaerida (with four concentric shells). + V. Polysphaerida (with five or more concentric shells). + VI. Spongosphaerida (with spongy shells). + +On the other hand, regarding the number of the radial spines and their +regular disposition on the shell-surface, we can distinguish five families, +viz.:-- + + I. Liosphaerida (without radial spines). + II. Stylosphaerida (with two radial spines, opposite in one axis). + III. Staurosphaerida (with four radial spines, opposite in pairs in two + axes, perpendicular one to another). + IV. Cubosphaerida (with six radial spines, opposite in pairs in the + three dimensive axes). + V. Astrosphaerida (with numerous--eight, twelve, twenty, or + more--radial spines, often more than a hundred). + +All five latter groups contain representatives of all six former groups; +therefore we get together not less than thirty different subfamilies of +#Sphaeroidea#, already enumerated in my Prodromus, 1881, p. 449. I repeat +them here to give a better survey of the system there employed. + + +------------------+----------------+---------------+---------------+ + | Families and | LIOSPHAERIDA |STYLOSPHAERIDA |STAUROSPHAERIDA| + | Subfamilies of | (anacantha). | (diacantha). |(tetracantha). | + | SPHAEROIDEA. | | | | + +------------------+----------------+---------------+---------------+ + | _Monosphaerida._ |Ethmosphaerida. |Xiphostylida. |Staurostylida. | + | (One single | | | | + | shell.) | | | | + | | | | | + | _Dyosphaerida._ |Carposphaerida. |Sphaerostylida.|Staurolonchida.| + | (Two concentric | | | | + | shells.) | | | | + | | | | | + | _Triosphaerida._ |Thecosphaerida. |Amphistylida. |Stauracontida. | + |(Three concentric | | | | + | shells.) | | | | + | | | | | + |_Tetrasphaerida._ |Cromyosphaerida.|Cromyostylida. |Staurocromyida.| + |(Four concentric | | | | + | shells.) | | | | + | | | | | + | _Polysphaerida._ |Caryosphaerida. |Caryostylida. |Staurocaryida. | + | (Five or more | | | | + | concentric | | | | + | shells.) | | | | + | | | | | + |_Spongosphaerida._|Plegmosphaerida.|Spongostylida. |Staurodorida. | + |(Spongy shells.) | | | | + +------------------+----------------+---------------+---------------+ + + +------------------+-------------+---------------+ + | Families and |CUBOSPHAERIDA|ASTROSPHAERIDA | + | Subfamilies of |(hexacantha).|(polyacantha). | + | SPHAEROIDEA. | | | + +------------------+-------------+---------------+ + | _Monosphaerida._ |Hexastylida. |Coscinommida. | + | (One single | | | + | shell.) | | | + | | | | + | _Dyosphaerida._ |Hexalonchida.|Haliommida. | + | (Two concentric | | | + | shells.) | | | + | | | | + | _Triosphaerida._ |Hexacontida. |Actinommida. | + |(Three concentric | | | + | shells.) | | | + | | | | + |_Tetrasphaerida._ |Hexacromyida.|Cromyommida. | + |(Four concentric | | | + | shells.) | | | + | | | | + | _Polysphaerida._ |Hexacaryida. |Arachnommida. | + | (Five or more | | | + | concentric | | | + | shells.) | | | + | | | | + |_Spongosphaerida._|Hexadorida. |Spongiommida. | + |(Spongy shells.) | | | + +------------------+-------------+---------------+ + +{53}The #Monosphaerida# comprise all those #Sphaeroidea# in which the +carapace is represented only by one single lattice-shell. Originally this +shell is probably everywhere an extracapsular or "cortical shell," which is +developed on the outside of the jelly-veil enveloping the central capsule, +and serves as a protective carapace for these soft enclosed parts. But with +the progress of growth the central capsule becomes larger than the +including shell, and sends out through its pores club-shaped prolongations +or caecal-sacs (Pl. 11, figs. 1, 5; Pl. 19, figs. 2, 3, 5; Pl. 20, fig. +1_a_; Pl. 27, fig. 3). These protruded sacs may fuse together again outside +the shell and form a spherical bladder, now enveloping the smaller shell; +the latter now becomes an intracapsular or "medullary shell." + +As #Pliosphaerida# (or _Sphaeroidea concentrica_) we can oppose to the +simple Monosphaerida all other #Sphaeroidea#, the lattice-shell of which is +composed of two or more concentric shells, connected by radial beams. +Probably all Pliosphaerida (or at least the greater part of them) arise +from the Monosphaerida by centrifugal growth; two or more radial spines are +developed from the surface of the simple lattice-sphere, and are united +together by communicating lateral branches, developed at equal distances +from the centre; and this same process may be repeated, two, three, four, +or more times. In this way originate the characteristic systems of +concentric spheres, all united by piercing radial beams which arise from +the surface of the innermost sphere (not from its centre). Regarding this +mode of growth, we can distinguish the innermost as "original" or "primary" +shell, and all subsequent ones as "apposed" or "secondary" shells; if the +number of concentric shells amount to three or more, commonly both +innermost shells lie within the central capsule and are medullary shells, +whilst all others lie outside it and are therefore cortical shells. This +difference can be commonly recognised also in the isolated shell, without +its central capsule; the distance between the cortical and the medullary +shells being commonly much larger than the distance between the two +medullary shells. + +The #Dyosphaerida#, or the #Sphaeroidea# with two concentric shells, are +the most numerous among the Pliosphaerida. Commonly in this group the inner +or primary shell lies within the central capsule as a true "medullary +shell," whilst the outer lies outside it as a "cortical shell"; therefore +the radial beams, connecting both, pierce the wall of the capsule. But in +several forms, mainly in the peculiar group of Diplosphaerida, both +concentric shells remain outside the central capsule, and both are +therefore "cortical shells." + +The #Triosphaerida#, or the #Sphaeroidea# with three concentric shells, are +also very rich in different forms, though not so numerous by far as the +Dyosphaerida. Commonly in the Triosphaerida both inner shells lie within +the central capsule as "medullary shells," whilst the third lies outside it +as a "cortical shell"; therefore the central capsule remains intermediate +in size between the outer and the middle shell. But in some genera (_e.g._, +_Rhodosphaera_) both outer shells are cortical and only the {54}innermost +is a medullary shell. In this case the size of the capsule remains +intermediate between the inner and the middle shell. + +The #Tetrasphaerida#, or the #Sphaeroidea# with four concentric shells, are +in general not frequent, and not rich in different forms. In most of the +observed species two inner shells are medullary, two outer cortical shells, +the former within, the latter without, the central capsule; and the wall of +the capsule, pierced by the connecting radial beams, lies between the two +middle shells. But there are some Tetrasphaerida in which all four shells +seem to be external or cortical shells. + +The #Polysphaerida#, or the #Sphaeroidea# with five or more concentric +shells, seem of course to offer the greatest possibility for the +development of very different forms; but in reality this group is the +poorest and smallest of all; and only one part of it, the Arachnosphaerida, +is rather common. In this peculiar division the shell is composed of five +to ten or more, very delicate, cobweb-like concentric shells, which are +connected by radial beams; all are cortical shells, and lie outside the +central capsule. Much more rare are those Polysphaerida, in which both +innermost shells, as true medullary shells, lie within the central capsule, +all others being outside it. The total number of concentric shells in this +group is commonly between five and ten, rarely more. + +The #Spongosphaerida# are distinguished from all other #Sphaeroidea# by the +spongy structure of the spherical shell, which is composed wholly or +partially of an irregular spongy framework. The relation of this group to +the other groups of #Sphaeroidea# is probably rather complicated, for in +some Spongosphaerida the whole shell is composed of massive spongy +reticulation, whilst in others it contains a spherical central cavity, and +in a third group this cavity is filled up by one or two concentric +lattice-shells, connected by radial beams. Many of these Spongosphaerida +are very common, and of considerable size. + +The #Collosphaerida# form a peculiar separate group of #Sphaeroidea#, +distinguished from all others by their social life or aggregation in +colonies (coenobia). They represent the only group of #Sphaerellaria# in +which this association of numerous individual capsules or cells is +realised. The shell is almost constantly simple, without regularly disposed +radial spines; therefore they may be called "social Monosphaerida," or +better "polyzoic Ethmosphaerida." Only in one small group +(Clathrosphaerida) the shell, enveloping every central capsule, is double +or surrounded by an external mantle; these may be compared to the +Diplosphaerida (or better to a part of the Carposphaerida, _Liosphaera_, p. +76). In most of the Collosphaerida the lattice-shell is more or less +irregular in form and structure. + + +_The Lattice Work_ of the fenestrated shells is in the #Sphaeroidea# of the +greatest variability, and its innumerable modifications serve mainly for +the distinction of species. In general we can distinguish as the most +important modifications a _regular_ network (with equal size, form, and +distance of the pores or meshes) and an _irregular_ network (with +{55}differences in the size, form, or distance of the meshes or pores). In +both groups the pores may be either angular or round; so that there may +exist together four different main forms of network--(A) regular lattice +with equal hexagonal pores; (B) regular lattice with equal circular pores; +(C) irregular lattice with unequal polygonal pores; (D) irregular lattice +with unequal roundish pores. Besides these modifications, the pores may be +prolonged into tubules which are directed radially towards the outside +(rarely towards the inside) of the sphere. In other cases they are +surrounded by elevated or honeycomb-like frames. + +_The Radial Spines_ exhibit in the #Sphaeroidea# the greatest variety in +form, size, disposition, &c., and their numerous modifications serve mainly +for the distinction of genera, their peculiar formation and size also for +the distinction of species. In general we may distinguish as the most +important modifications primary and secondary spines. The primary spines or +"main spines" are commonly direct outward prolongations of the internal +radial beams, connecting the concentric shells. The secondary or +"by-spines" arise only from the surface of the lattice-shell, without +reference to the internal beams. The by-spines are commonly smaller, and +much more numerous than the main spines. Regarding the form, the radial +spines are either roundish (cylindrical or conical, often also club-shaped, +rarely spindle-shaped) or angular (commonly three-sided, prismatic or +pyramidal). The spines are constantly solid, never hollow; the "internal +canals," described by some authors, are only microscopic views of the +transparent edges. In many cases the spines are branched or forked. The +most important difference in the variable shape of the spines is their +regular or irregular number and disposition, which afford characters for +the distinction of our five families. + +_The Three Dimensive Axes_--or the three diameters of the sphere, +perpendicular one to another--are in the great majority of the +#Sphaeroidea# significant in the promorphological consideration of the +body, and are indicated either by the position of the external radial +spines, or at least of the internal radial beams, connecting the concentric +spheres. Commonly two radial spines are placed opposite in each axis. The +most perfect group in this respect seems to be that of the Cubosphaerida, +in which the three axes are represented by three pairs of spines. Next come +the Staurosphaerida, in which two axes in cross-form are exhibited by two +pairs of spines. The most simple group are the Stylosphaerida, in which +only one pair of spines is developed, indicating one single axis. These +three families form together a continuous natural series,--the +#Sphaeroidea# with real dimensive axes,--and exhibit at the same time +relations to the three other suborders of #Sphaerellaria#, the #Larcoidea#, +#Discoidea#, and #Prunoidea# respectively. At both ends of this series +stand two other families, on one side the Liosphaerida, without any radial +spines on the surface of the sphere, on the other side the Astrosphaerida, +in which the radial spines are developed in great and variable numbers, at +least eight to twelve, commonly twenty to forty, often more than a hundred +or even a thousand. + +{56}The #Liosphaerida# comprise all those #Sphaeroidea# in which the +surface of the shell is smooth, without radial spines (Pls. 12, 20). The +simplest of these are the Ethmosphaerida, with one single lattice-shell, +enveloping the spherical central capsule. _Cenosphaera_, the most simple +form of the Ethmosphaerida, may be regarded as the common ancestral form of +all #Sphaeroidea#, in an ontogenetical as well as in a phylogenetical and +morphological sense. From this simple lattice sphere all other +#Sphaeroidea# can be derived either by radial or by tangential growth. If +the radial beams, arising from the surface of the simple fenestrated +sphere, become connected (at equal distances from the centre) by tangential +beams, we get the compound shells of the "Liosphaerida concentrica" (with +two, three, four, or more concentric spheres). The radial beams connecting +these exhibit in many Liosphaerida the same regular disposition and number +as the external radial spines in the Astrosphaerida. Perhaps these forms in +a "natural system" would be better united (_e.g._, Liosphaerida with twelve +or twenty internal radial beams, and Astrosphaerida with twelve or twenty +external radial spines); but in many cases (mainly for higher numbers) the +certain determination of their number and disposition is very difficult or +quite impossible. + +The #Cubosphaerida# (Pls. 21-25) represent the large and very important +family of #Sphaeroidea#, in which all three dimensive axes are equally +distinguished by pairs of spines, corresponding to three axes of a cube or +of a regular octahedron, agreeing therefore also with the three axes of the +cubic or regular crystalline system. In the majority of the Cubosphaerida +the six radial spines are accurately opposite each other in pairs in three +axes, perpendicular one to another, and commonly they are of equal size and +form; but in some genera the three pairs of spines become differentiated, +whilst both spines of each pair remain equal. Either one pair is larger +than the two others (which are equal), corresponding to the axes of the +quadratic crystalline system; or all three pairs are different +(corresponding to the three unequal axes of the rhombic crystalline +system); the former nearer to the #Discoidea#, the latter to the +#Larcoidea#. We may suppose with some probability, that the Cubosphaerida +are for the most part the common ancestral group of those #Sphaeroidea#, in +which a certain number of radial spines or beams is disposed in a regular +order; the Staurosphaerida may be derived from them by loss of one pair of +spines, the Stylosphaerida by loss of two pairs of spines, and most +Astrosphaerida by multiplying the radial spines, six to fourteen or more +secondary spines being added to the six primary "dimensive spines." +However, in many Astrosphaerida (_e.g._, in those with eight spines, +_Centrocubus_, _Octodendron_, &c.) the regular geometrical disposition of +the radial spines seems to follow another mathematical order, quite +independent of the Cubosphaerida. + +The #Staurosphaerida# (Pl. 15) are distinguished by the possession of four +radial spines, opposite in pairs in two axes, perpendicular one to another. +This rectangular cross determines a certain plane, the "equatorial plane," +and this brings the Staurosphaerida near {57}to the #Discoidea#, mainly to +those which also bear on the periphery of the circular equatorial plane +four crossed spines (such as _Staurodisculus_, _Stethostaurus_, +_Staurodictya_, &c.). But in these cruciform #Discoidea# the shell and the +enclosed central capsule are discoidal or lenticular, whilst in the +Staurosphaerida they remain spherical. Commonly the cross is quite regular, +with four right angles and four equal beams; but often also it becomes more +or less irregular. In some genera one pair of equal opposite spines is +larger than the other pair. These forms represent the three different axes +of the rhombic crystal system, whilst the common regular Staurosphaerida +represent those of the quadratic crystal system. The latter can be derived +from the Cubosphaerida (representing the regular crystal system) by +reduction of one axis and loss of its pair of spines. In general the number +of species (and particularly of the individuals) is much smaller in the +Staurosphaerida than in all other families of #Sphaeroidea#. + +The #Stylosphaerida# (Pls. 13-17) can be derived from the Cubosphaerida by +reduction of two dimensive axes and loss of two pairs of spines. Therefore, +here one pair of spines only is developed, opposite in one single axis. +This "monaxonial" form brings the Stylosphaerida very near to the +ellipsoidal #Prunoidea# (mainly to many two-spined forms of Ellipsida and +Druppulida); but they differ from these by the spherical (not ellipsoidal) +form of the central capsule and of the enclosing lattice-shell. In the +greater part of the Stylosphaerida both spines are of equal size and form, +accurately opposite in the "main axis." But in many forms both spines +become unequal in size or form, often very different. More rarely they are +not accurately opposed, but placed in two different axes, intersecting at a +small variable angle. The small group of Saturnalida presents a very +remarkable and peculiar structure, in which both spines (at equal distances +from the centre) are united by a circular or elliptical ring (Pl. 13, figs. +15, 16; Pl. 16, figs. 16, 17). + +The #Astrosphaerida# are distinguished from the other #Sphaeroidea# by the +great and variable number of their external radial spines (Pls. 11, 18-20, +26-30). Commonly this number amounts to from twelve to twenty, rarely to +only eight to ten, very often to thirty-two to forty or more; in many +species more than one hundred are present. As already mentioned above, it +would be important to distinguish between primary spines (as outer +prolongations of the inner radial beams) and secondary spines (developed +from the surface of the shell), but in many cases this distinction is +difficult or impossible. More practical is the distinction between larger +"main spines" and smaller "by-spines." The size and form of the radial +spines is extremely variable. Much more important is their number and +disposition. In general we can here distinguish the following different +cases:--(A) radial spines are developed from all the nodal points of the +network on the shell surface; (B) the number of the spines is smaller than +that of the nodal points, but they are irregularly scattered; (C) the +radial spines exhibit a limited number and a certain regular disposition. +In this latter case the following modes of distribution seem to be the most +important:--(_a_) eight spines placed in the four diagonal axes of the +{58}regular cube (Pl. 18, figs. 1-3); (_b_) twelve spines (placed in the +corner axes of the regular icosahedron); (_c_) fourteen spines (six placed +in the three dimensive axes of the regular octahedron, eight in the centres +of its eight faces); (_d_) twenty spines (placed either in the same order +as in many #Larcoidea# and ACANTHARIA [?], or in the twenty corners of the +regular dodecahedron); (_e_) thirty-two spines (twelve placed in the twelve +corners of the regular icosahedron, twenty in the centre of its triangular +faces). Besides these most important and quite geometrical modes of +disposition there also seem to occur in the Astrosphaerida the following +subregular (or symmetrical?) modes: 9, 10, 16, 18, 24, 40, 60, 80. But it +is very difficult to give a correct account of these modes. In every case +this manifold and regular disposition of the radial spines is of the +highest interest for the study of general "Promorphology." + + +_The Central Capsule_ is in all #Sphaeroidea# (without any exception) a +perfect sphere in the geometrical sense, even in those forms in which the +enclosing lattice-shell is more or less irregular (_i.e._, many +Collosphaerida). This is the most important character, which separates the +#Sphaeroidea# from all other #Sphaerellaria#. For in the #Prunoidea# the +capsule is ellipsoidal, with one prolonged axis; in the #Discoidea# +lenticular, with one shortened axis; in the #Larcoidea# lentelliptical, +with three different dimensive axes. The central capsule is originally +always enclosed by the lattice-shell; but in many cases with increasing +growth this relation becomes inverted; the capsule sending out many +club-shaped blind sacs through the meshes of the lattice-shell, and these +melting together outside the latter, a new membrane is formed, enclosing a +"medullary shell." + +_The Nucleus_ of the cell exhibits a very different shape in the solitary +and the social #Sphaeroidea#. In the solitary or monozoic #Sphaeroidea# the +centre of the central capsule is occupied by a large spherical concentric +nucleus, with or without nucleoli; also this nucleus is originally always +within the innermost lattice-shell, but with increasing size may overgrow +and enclose it. A short time before the formation of the vibratile spores +the central nucleus becomes resolved into many small nuclei. In the social +or polyzoic #Sphaeroidea#--the Collosphaerida--commonly the simple central +nucleus very early (a long time before the formation of the spores) is +divided into a great number of small nuclei, whilst the centre of the +capsule becomes filled with a large oil-globule. Therefore we find the same +difference between the solitary and social forms in the #Sphaeroidea# as in +the #Colloidea#. Here also the calymma, or the jelly-mantle, enveloping the +central capsule, is in the social forms very large and voluminous, +differentiated into alveoles, whilst in the solitary forms it is much +smaller, without alveoles. + +{59}_Synopsis of the Families of_ #Sphaeroidea#. + + { A. Liosphaerida { Spherical shell + { monozoa. { commonly + { Single cells { quite regular, + { (each with shell) { simple, or + Surface of { living solitary. { composed of + the spherical { { two or more + shell smooth, { { concentric + rough, or { { spheres, 5. LIOSPHAERIDA. + thorny, but { + not armed { B. Liosphaerida { Spherical shell + with radial { polyzoa. { commonly + spines. { Aggregated cells { more or less + { (each with { irregular, + { shell) living { simple (rarely + { in colonies. { composed of + { { two concentric + { { spheres), 6. COLLOSPHAERIDA. + + Surface of { Two radial main-spines, opposite in + the spherical { one axis of the shell 7. STYLOSPHAERIDA. + shell armed { + with two, { Four radial main-spines, opposite in + four, or six { pairs in two dimensive axes, + radial main { perpendicular one to another, 8. STAUROSPHAERIDA. + spines, { + opposite in { Six radial main-spines, opposite in + pairs in one, { pairs in three dimensive + two, or three { axes (perpendicular one to + dimensive { another), 9. CUBOSPHAERIDA. + axes (always { + solitary). { + + Surface of the spherical shell covered with numerous + (commonly irregularly disposed) radial spines, + often also twelve to twenty, more or less regularly + disposed, 10. ASTROSPHAERIDA. + + + +Family V. #LIOSPHAERIDA#, Haeckel, 1881. + +_Liosphaerida_, Haeckel, 1881, Prodromus, p. 449. + +_Definition._--#Sphaeroidea# without radial spines on the surface of the +spherical shell; living solitary (not associated in colonies). + +The family #Liosphaerida# comprises all those solitary #Sphaeroidea# in +which the surface of the spherical shell is not armed with radial spines. +Nearly the half of this large group is formed by the Ethmosphaerida, in +which the carapace is a quite simple, spherical lattice-shell; this +subfamily is probably the common ancestral group from which all other +#Sphaeroidea#, or even all #Sphaerellaria#, can be derived in a +phylogenetical as well as in a morphological sense. The central capsule in +this first subfamily is constantly enclosed by the fenestrated shell, and +separated from it by the jelly-veil. The shell is therefore an +extracapsular or medullary shell. + +To these simple Ethmosphaerida all other subfamilies can be opposed as +"Liosphaerida concentrica," as their carapace is composed of two or more +concentric lattice-shells; two in the Carposphaerida, three in the +Thecosphaerida, four in the Cromyosphaerida, five or more in the +Caryosphaerida. In all these four subfamilies the concentric shells are +simple (not spongy) fenestrated shells. In a sixth subfamily, in the +Plegmosphaerida, the shell is wholly or partially composed of spongy +wicker-work, with or without a latticed medullary shell in the centre. + +The internal radial beams, in the "Liosphaerida composita" connecting the +concentric spheres, exhibit in their number and disposition similar +important differences, such as the external radial spines in the +Astrosphaerida. The following eight {60}different cases of regular +disposition were observed:--(A) two opposite beams in one axis; (B) four +beams, opposite in pairs in two axes perpendicular one to another; (C) six +beams, opposite in pairs in the three dimensive axes; (D) eight beams, +opposite in pairs in the four diagonals of the regular cube; (E) twelve +beams corresponding to the twelve axes of the regular icosahedron; (F) +fourteen beams quite regularly disposed (six corresponding to the three +axes of the regular octahedron, eight to the central points of its faces); +(G) twenty beams (probably corresponding to the twenty corners of a regular +dodecahedron); (H) thirty-two beams, regularly disposed. Rarely the number +of the radial beams is intermediate between these eight cases, and rarely +it is higher; then commonly the disposition is irregular. The regularity of +their disposition in the great majority of cases is very remarkable and +evident. + +_Synopsis of the Genera of Liosphaerida._ + + ------------------------------------------------------------------------- + I. Subfamily Ethmosphaerida. + (Shell one single latticed sphere.) + ------------------------------------------------------------------------- + {Shell cavity + { simple, 15. _Cenosphaera_. + Pores of the { + shell simple, {Shell cavity + not prolonged { with radial + into free tubuli. { beams united + { in the + { centre, 16. _Stigmosphaera_. + + Pores prolonged {Tubuli external, + into free { centrifugal, 17. _Ethmosphaera_. + conical or { + cylindrical {Tubuli internal, + tubuli. { centripetal, 18. _Sethosphaera_. + ------------------------------------------------------------------------- + II. Subfamily Carposphaerida. + (Two concentric spheres.) + ------------------------------------------------------------------------- + One shell medullary (intracapsular), + the other cortical (extracapsular), 19. _Carposphaera_. + + Both shells cortical + (near together), 20. _Liosphaera_. + ------------------------------------------------------------------------- + III. Subfamily Thecosphaerida. + (Three concentric spheres.) + ------------------------------------------------------------------------- + Two shells medullary + (intracapsular), one shell + cortical (extracapsular), 21. _Thecosphaera_. + + One shell medullary (intracapsular), + two shells cortical + (extracapsular), 22. _Rhodosphaera_. + ------------------------------------------------------------------------- + IV. Subfamily Cromyosphaerida. + (Four concentric spheres.) + ------------------------------------------------------------------------- + Two inner medullary shells + (intracapsular), and two outer + cortical shells (extracapsular), 23. _Cromyosphaera_. + ------------------------------------------------------------------------- + V. Subfamily Caryosphaerida. + (Five or more concentric spheres.) + ------------------------------------------------------------------------- + Two inner medullary shells, and + three or more outer cortical + shells, 24. _Caryosphaera_. + ------------------------------------------------------------------------- + VI. Subfamily Plegmosphaerida. + (Spherical shell wholly or partially of spongy structure.) + ------------------------------------------------------------------------- + Spongy sphere {Sphere solid, 25. _Styptosphaera_. + without latticed { + medullary shell {Sphere with a + in the centre. { central cavity, 26. _Plegmosphaera_. + + Spongy sphere with {One single + one or two { medullary shell, 27. _Spongoplegma_. + latticed { + medullary shells {Two concentric + in the centre. { medullary + { shells, 28. _Spongodictyon_. + + + +{61}Subfamily ETHMOSPHAERIDA,[25] Haeckel, 1862, Monogr. d. Radiol., p. 348 +(_sensu restricto_). + +_Definition._--#Liosphaerida# with one single spherical lattice-shell; +living solitary, not aggregated in colonies. + + +Genus 15. _Cenosphaera_,[26] Ehrenberg, 1854, Monatsber. d. k. preuss. +Akad. d. Wiss. Berlin, p. 237. + +_Definition._--#Liosphaerida# with one single latticed sphere, with simple +shell-pores (not prolonged into free tubuli) and with simple shell-cavity +(without internal radial beams). + +The genus _Cenosphaera_ is the most simple form of all SPHAEROIDEA, and may +be regarded as the common ancestral form of this order. The siliceous +latticed shell, in which the central capsule is enclosed, represents a +simple regular sphere, with simple cavity. The pores of the shell-wall are +simple, not prolonged into radial tubuli (as in _Ethmosphaera_ and +_Sethosphaera_). According to the different form of the pores, the numerous +species of this genus can be disposed in four different subgenera. Some +species may be easily confounded with isolated shells of the corresponding +social _Collosphaera_; but in this latter the spherical shell-form is +commonly more or less irregular, in _Cenosphaera_ quite regular. + + + +Subgenus 1. _Phormosphaera_, Haeckel, 1881, Prodromus, p. 448. + +_Definition._--Pores of the shell regular or subregular, hexagonal or +circular, with hexagonal frames or lobes; all nearly of equal size and +form. + + +1. _Cenosphaera primordialis_, n. sp. + +Shell very thin walled, smooth. Pores hexagonal, regular, or subregular; +twelve to fifteen on the half meridian of the shell; bars between them +extremely delicate (only visible when three hundred or four hundred times +enlarged). Diameter of the shell nine to ten times that of the meshes. This +species is remarkable for the extreme delicacy of the arachnoidal network +of the simple spherical shell; it may be regarded as the common ancestral +form of all #Sphaeroidea#. The shell equals that of _Heliosphaera +tenuissima_ (figured in my Monograph, 1862, pl. ix. fig. 2), but differs +from it by the smooth surface and the absence of all spines or thorns. I +observed this species living in the Indian Ocean, near Ceylon, in 1882; the +spherical diameter of the central capsule is about one-third of that of the +shell; the contents of the central capsule are colourless {62}and +transparent, except the central dark globular nucleus. The same shells also +occur in some mounted preparations of surface organisms from the +Challenger. + +_Dimensions._--Diameter of the shell 0.12, of the pores 0.012. + +_Habitat._--Indian Ocean, Ceylon, Haeckel; Central Pacific, Stations 266, +271, surface. + + +2. _Cenosphaera inermis_, Haeckel. + + _Heliosphaera inermis_, Haeckel, 1862, Monogr. d. Radiol., p. 351, Taf. + ix. fig. 1. + +Surface of the thin-walled shell smooth. Pores regular, hexagonal, twelve +to fifteen times as broad as the bars, seven to nine on the quadrant. + +_Dimensions._--Diameter of the shell 0.08 to 0.12, pores 0.012 to 0.015, +bars 0.001. + +_Habitat._--Cosmopolitan; Mediterranean, Atlantic, Indian, Pacific, +surface. + + +3. _Cenosphaera hexagonalis_, n. sp. + +Surface of the thick-walled shell smooth. Pores regular, hexagonal, five to +six times as broad as the bars, six to eight on the quadrant. + +_Dimensions._--Diameter of the shell 0.1 to 0.15, pores 0.01 to 0.012, bars +0.002. + +_Habitat._--Central Pacific, Stations 265 to 274, at various depths. + + +4. _Cenosphaera mellifica_, n. sp. (Pl. 12, fig. 9). + +Surface of the thick-walled shell smooth. Pores regular, circular, with +thin hexagonal frames, four times as broad as the bars, six to eight on the +quadrant. + +_Dimensions._--Diameter of the shell 0.2, pores 0.12, bars 0.003. + +_Habitat._--South Pacific, Station 288, surface. + + +5. _Cenosphaera favosa_, n. sp. (Pl. 12, fig. 10). + +Surface of the thick-walled shell rough. Pores regular, circular, with thin +hexagonal frames, three times as broad as the bars, ten to twelve on the +quadrant. + +_Dimensions._--Diameter of the shell 0.2, pores 0.09, bars 0.003. + +_Habitat._--North Atlantic, Faeroee Channel (Gulf Stream), John Murray, +surface. + + +6. _Cenosphaera vesparia_, n. sp. (Pl. 12, fig. 11). + +Surface of the thick-walled shell smooth. Pores regular, circular, with +thick hexagonal frames, twice as broad as the bars, ten to twelve on the +quadrant. + +_Dimensions._--Diameter of the shell 0.25, pores 0.016, bars 0.008. + +_Habitat._--Central Pacific, Station 265, depth 2900 fathoms, and surface. + + +{63}7. _Cenosphaera bombus_, n. sp. + +Shell thick walled, rough. Pores regular, circular, with thin hexagonal +frames, of the same breadth as the bars, twenty to twenty-two on the +quadrant. + +_Dimensions._--Diameter of the shell 0.3, pores and bars 0.005. + +_Habitat._--Tropical Atlantic, Station 347, depth 2250 fathoms. + + +8. _Cenosphaera melecta_, n. sp. + +Shell thick walled, papillate. Pores regular, circular, double-edged, with +thick hexagonal frames, of the same breadth as the bars; a short conical +papilla in the corner of each hexagon; fourteen to sixteen pores on the +quadrant. + +_Dimensions._--Diameter of the shell 0.2, pores and bars 0.008. + +_Habitat._--Fossil in Barbados. + + +9. _Cenosphaera anthophora_, n. sp. + +Shell thick walled, papillate. Pores regular, circular, with an elegant +six-lobed frame and a coronal of six short papillae; the latter alternating +with the six lobes (quite as in Pl. 28, fig. 1_b_). Pores twice as broad as +the bars, ten to twelve on the quadrant. + +_Dimensions._--Diameter of the shell 0.13, pores 0.01, bars 0.005. + +_Habitat._--Central Pacific, Station 271, surface. + + +10. _Cenosphaera rosetta_, n. sp. + +Shell thin walled, smooth. Pores regular, circular, with an elegant +six-lobed outer opening, without papillae. Pores of the same breadth as the +bars, six to eight on the quadrant. + +_Dimensions._--Diameter of the shell 0.1, pores and bars 0.006. + +_Habitat._--South Atlantic, Station 323, depth 1900 fathoms. + + + +Subgenus 2. _Circosphaera_, Haeckel. + +_Definition._--Pores of the spherical shell regular or subregular, +circular, without hexagonal frames or lobes, all nearly of equal size and +form. + + +11. _Cenosphaera porophaena_, Ehrenberg. + + _Cenosphaera porophaena_, Ehrenberg, 1858, Monatsber. d. k. preuss. Akad. + d. Wiss. Berlin, p. 31. + +Shell thin walled, smooth. Pores regular, circular, six to eight times as +broad as the bars, five to six on the quadrant. + +_Dimensions._--Diameter of the shell 0.1, pores 0.012, bars 0.002. + +_Habitat._--Mediterranean (Crete, depth 1100 fathoms; Corfu, surface). + + +{64}12. _Cenosphaera setosa_, Ehrenberg. + + _Cenosphaera setosa_, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. + Berlin, p. 287, Taf. vii. fig. 1. + +Shell thin walled, covered with very short and numerous bristles. Pores +regular, circular, five to six times as broad as the bars, six to eight on +the quadrant. + +_Dimensions._--Diameter of the shell 0.17, pores 0.2, bars 0.03. + +_Habitat._--West Tropical Pacific, 3300 fathoms; Philippine Sea, Station +200, depth 250 fathoms. + + +13. _Cenosphaera plutonis_, Ehrenberg. + + _Cenosphaera plutonis_, Ehrenberg, 1854, Mikrogeol., Taf. xxxv. B, B. iv. + fig. 20. + +Shell thin walled, covered with short conical papillae. Pores regular, +circular, twice as broad as the bars, eight to nine on the quadrant. + +_Dimensions._--Diameter of the shell 0.09, pores 0.006, bars 0.003. + +_Habitat._--North Atlantic, Station 353, depth 2965 fathoms. + + +14. _Cenosphaera proserpinae_, n. sp. + +Shell thin walled, smooth. Pores regular, circular, four times as broad as +the bars, five to six on the quadrant. + +_Dimensions._--Diameter of the shell 0.08, pores 0.008, bars 0.002. + +_Habitat._--Central Pacific, Station 265, depth 2900 fathoms. + + +15. _Cenosphaera eridani_, n. sp. + +Shell thin walled, smooth. Pores regular, circular, three times as broad as +the bars, eleven to twelve on the quadrant. + +_Dimensions._--Diameter of the shell 0.16, pores 0.01, bars 0.003. + +_Habitat._--South Pacific, Station 295, depth 1500 fathoms. + + +16. _Cenosphaera lethe_, n. sp. + +Shell thick walled, smooth. Pores regular, circular, double-edged, five +times as broad as the bars, sixteen to eighteen on the quadrant. + +_Dimensions._--Diameter of the shell 0.25, pores 0.01, bars 0.002. + +_Habitat._--North Atlantic, Station 64, depth 2700 fathoms. + + +17. _Cenosphaera elysia_, n. sp. (Pl. 12, fig. 8). + +Shell thick walled, rough. Pores regular, circular, double-edged, twice as +broad as the bars, twelve to fourteen on the quadrant. + +_Dimensions._--Diameter of the shell 0.2, pores 0.01, bars 0.005. + +_Habitat._--Central Pacific, Station 266, depth 2750 fathoms. + + +{65}18. _Cenosphaera nirwana_, n. sp. + +Shell thick walled, smooth. Pores regular, circular, twice as broad as the +bars, twenty-four to twenty-five on the quadrant. + +_Dimensions._--Diameter of the shell 0.25, pores 0.004, bars 0.002. + +_Habitat._--Indian Ocean, Belligemma, Ceylon, surface; Haeckel. + + +19. _Cenosphaera maxima_, n. sp. + +Shell thick walled, smooth. Pores regular, circular, twice as broad as the +bars, thirty to thirty-three on the quadrant. + +_Dimensions._--Diameter of the shell 0.3 to 0.4, pores 0.012, bars 0.006. + +_Habitat._--West Tropical Pacific, Station 225, depth 4475; also fossil in +Barbados. + + +20. _Cenosphaera compacta_, n. sp. (Pl. 12, fig. 7). + +Shell very thick walled, rough (its wall one-fourth to one-third as thick +as the radius). Pores subregular, circular, of the same breadth as the +bars, seven to eight on the quadrant. + +_Dimensions._--Diameter of the shell 0.15, pores and bars 0.012. + +_Habitat._--Central Pacific, Station 265, depth 2900 fathoms. + +_Cenosphaera radiata_, Zittel, 1876 (L. N. 29, p. 84, Taf. ii. figs. 7, 8), +a fossil Cretaceous species, is closely allied to _Cenosphaera compacta_. + + +21. _Cenosphaera crassa_, n. sp. + +Shell very thick walled, rough (its wall nearly half as thick as the +radius). Pores tubular, double-edged, regular, circular, ten times as broad +as the thin united bars, twelve to fourteen on the quadrant. + +_Dimensions._--Diameter of the shell 0.14, pores 0.01, bars 0.001. + +_Habitat._--Central Pacific, Station 268, depth 2900 fathoms. + + +22. _Cenosphaera solida_, n. sp. + +Shell very thick walled, covered with innumerable short bristles (its wall +one-third as thick as the radius). Pores regular, circular, four times as +broad as the bars, tubular, eight to ten on the quadrant. + +_Dimensions._--Diameter of the shell 0.2, pores 0.02, bars 0.005. + +_Habitat._--Antarctic Ocean, Station 157, depth 1950 fathoms. + + + +Subgenus 3. _Cyrtidosphaera_, Haeckel, 1862, Monogr. d. Radiol., p. 348. + +_Definition._--Pores of the spherical shell irregularly polygonal, of +unequal size or form, sometimes roundish with polygonal frames. + + +{66}23. _Cenosphaera reticulata_, Haeckel. + + _Cyrtidosphaera reticulata_, Haeckel, 1862, Monogr. d. Radiol., p. 349, + Taf. xi. fig. 2. + +Shell very thin walled, smooth. Pores irregular, polygonal, two to eight +times as broad as the bars, fifteen to twenty on the quadrant (groups of +four to eight smaller meshes are scattered on the surface, and separated by +reticular rows of larger meshes). + +_Dimensions._--Diameter of the shell 0.16, pores 0.004 to 0.016, bars +0.002. + +_Habitat._--Mediterranean (Messina), surface. + + +24. _Cenosphaera tenerrima_, n. sp. + +Shell extremely thin walled, smooth, like a cobweb. Pores very irregular +and small, polygonal with thread-like bars, thirty to forty on the +quadrant. + +_Dimensions._--Diameter of the shell 0.25, pores 0.002 to 0.008, bars under +0.001. + +_Habitat._--Central Pacific, Station 271, surface. + + +25. _Cenosphaera polygonalis_, n. sp. + +Shell thin walled, smooth, with irregular, polygonal pores, three to four +times as broad as the bars, eight to ten on the quadrant. + +_Dimensions._--Diameter of the shell 0.2, pores 0.012 to 0.02, bars 0.005. + +_Habitat._--North Pacific, Station 236, surface. + + +26. _Cenosphaera papillata_, n. sp. + +Shell thick walled, covered with short conical papillae. Pores irregular, +polygonal, three to five times as broad as the bars, fourteen to sixteen on +the quadrant. + +_Dimensions._--Diameter of the shell 0.12, pores 0.004 to 0.007, bars +0.0015. + +_Habitat._--South Atlantic, Station 325, surface. + + +27. _Cenosphaera cristata_, n. sp. + +Shell thick walled, rough. Pores irregular, roundish, surrounded by +polygonal crested frames two to three times as broad as the bars, eight to +twelve on the quadrant. + +_Dimensions._--Diameter of the shell 0.16, pores 0.006 to 0.01, bars 0.003. + +_Habitat._--North Pacific, Station 254, surface. + + +28. _Cenosphaera perforata_, n. sp. (Pl. 26, fig. 10). + + _Ceriosphaera perforata_, Haeckel, 1881, Prodromus et Atlas, _loc. cit._ + +Shell thick walled, rough. Pores irregular, roundish, surrounded by high +polygonal funnel-shaped frames, which are solid in the inner half, +perforated by numerous very small pores in the {67}outer half, +sieve-shaped. Pores one to three times as broad as the bars, of very +different size, four to six on the quadrant. + +_Dimensions._--Diameter of the shell 0.15, pores 0.01 to 0.02, bars 0.005 +to 0.01. + +_Habitat._--Tropical Atlantic, Station 347, depth 2250 fathoms. + + +29. _Cenosphaera coronata_, n. sp. (Pl. 26, fig. 11). + +Shell thick walled, rough. Pores irregular, roundish, surrounded by high +polygonal frames bearing on their sharp crest a series of small papillae, +so that each pore is surrounded by a coronal of such spinules. Pores four +to eight times as broad as the bars, four to five on the quadrant. + +_Dimensions._--Diameter of the shell 0.15, pores 0.01 to 0.03, bars 0.002 +to 0.008. + +_Habitat._--Central Pacific, Station 272, depth 2600 fathoms. + + + +Subgenus 4. _Porosphaera_, Haeckel. + +_Definition._--Pores of the spherical shell irregular, roundish, without +polygonal frames, of unequal size or form. + + +30. _Cenosphaera antiqua_, Haeckel. + + _Cenosphaera plutonis_, var., Dunikowski, 1882, Denkschr. d. k. Akad. d. + Wiss. Wien, Bd. xlv. p. 25, Taf. iv. figs. 47, 48. + + _Cenosphaera plutonis_, var., Stoehr, 1880, Palaeontogr. xxvi. p. 85, + Taf. i. fig. 1. + +Shell thin walled, smooth. Pores irregular, roundish, two to eight times as +broad as the bars, ten to fifteen on the quadrant. + +_Dimensions._--Diameter of the shell 0.15 to 0.2, pores 0.007 to 0.015, +bars 0.002 to 0.008. + +_Habitat._--Fossil in the Jurassic, Cretaceous, and Tertiary formations; +living in the depths of the Atlantic and Pacific; Station 332, depth 2200 +fathoms; Station 225, depth 4475 fathoms, &c. + + +31. _Cenosphaera gigantea_, n. sp. + +Shell thick walled, smooth. Pores irregular, roundish, two to five times as +broad as the bars, thirty to forty on the quadrant. + +_Dimensions._--Diameter of the shell 0.4 to 0.5, pores 0.004 to 0.01, bars +0.002. + +_Habitat._--Central Pacific, Station 268, depth 2900 fathoms; also fossil +in Barbados. + + +32. _Cenosphaera marginata_, n. sp. + +Shell very thick walled, smooth. Pores irregular, roundish, double-edged, +three to eight times as broad as the bars, six to eight on the quadrant. + +{68}_Dimensions._--Diameter of the shell 0.12, pores 0.01 to 0.03, bars +0.004. + +_Habitat._--Central Pacific, Station 274, depth 2750 fathoms. + + +33. _Cenosphaera aspera_, Stoehr. + + _Cenosphaera aspera_, Stoehr, 1880, Palaeontogr. Bd. xxvi. p. 85, Taf. i. + fig. 2. + +Shell thick walled, rough, covered with short conical papillae. Pores +irregular, roundish, of about the same breadth as the bars, eight to twelve +on the quadrant. + +_Dimensions._--Diameter of the shell 0.17, pores and bars 0.01 to 0.04. + +_Habitat._--Fossil in Tertiary rocks of Sicily; Grotte, Stoehr. + + +34. _Cenosphaera hirsuta_, Ehrenberg. + + _Cenosphaera hirsuta_, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss., + Berlin, p. 287, Taf. x. fig. 18. + +Shell thin walled, rough, covered with innumerable very short bristles. +Pores very irregular, roundish, of about the same breadth as the bars. + +_Dimensions._--Diameter of the shell 0.11, pores and bars 0.002 to 0.012. + +_Habitat._--Indian Ocean, Zanzibar, Pullen; depth 2200 fathoms. + + + +Genus 16. _Stigmosphaera_,[27] Haeckel, n. gen. + +_Definition._--#Liosphaerida# with one single latticed sphere, with simple +shell-pores (not prolonged into free tubuli); in the central point of the +spherical shell-cavity are united a number of radial beams, which become +forked and inserted into the inner surface of the shell by their distal +ends. + +The genus _Stigmosphaera_ differs from _Cenosphaera_ (and from all other +Monosphaerida) by internal radial beams, which are united in the centre of +the simple spherical shell; these beams are branched, and the distal ends +of the branches inserted on the internal surface of the shell. I have +observed only two, nearly identical specimens of this genus, both with +regular, hexagonal pores and thin bars; the beams were implanted in the +corners of the hexagons. In one specimen the surface was covered with short +radial bristles, whilst these in the other specimen were prolonged into +radial spines (like _Acanthosphaera_). Possibly this peculiar genus is +derived from _Carposphaera_, by reduction and loss of a central medullary +shell. + + +_Stigmosphaera actinocentra_, n. sp. + +Shell very thin walled, rough, with regular circular, hexagonally framed +pores, six times as broad as the bars, eight to ten on the quadrant; in the +corner of each hexagon a small bristle. In {69}the central point of the +shell are united about twelve (?) thin and straight radial beams, which are +forked, with dichotomous branches; the distal ends of the branches are +inserted in the corners of the hexagons on the inside of the shell. + +_Dimensions._--Diameter of the shell 0.15, pores 0.02, bars 0.003. + +_Habitat._--Central Pacific, Station 271, surface. + + + +Genus 17. _Ethmosphaera_,[28] Haeckel, 1862, Monogr. d. Radiol., p. 349. + +_Definition._--#Liosphaerida# with one single latticed sphere, with simple +shell-cavity; with shell-pores which are prolonged on the outside in +centrifugal, conical, or cylindrical tubuli. + +The genus _Ethmosphaera_ differs from the simple _Cenosphaera_, its +ancestral form, by the peculiar formation of the shell-pores; in all +observed species of the genus these are quite regular, of nearly equal size +and form; their base in the spherical shell-face is hexagonal, but on the +outside prolonged into centrifugal, external, radial tubuli, which are +either conical or cylindrical (in the latter case both openings of the +tubes being equal, in the former the outer opening being smaller than the +inner). The solitary _Ethmosphaera_ corresponds to the social +_Siphonosphaera_; but in the former the formation of the shell and of its +tubuli is quite regular, in the latter more or less irregular. + + + +Subgenus 1. _Ethmosphaerella_, Haeckel. + +_Definition._--Tubuli conical, their outer opening smaller than the inner. + + +1. _Ethmosphaera siphonophora_, Haeckel. + + _Ethmosphaera siphonophora_, Haeckel, 1862, Monogr. d. Radiol., p. 350, + Taf. xi. fig. 1. + +Tubuli conical, their outer opening half as broad as the inner and three +times as broad as their height. Five to six pores on the quadrant. Diameter +of the outer pores one and a half times as large as their distance from +each other. + +_Dimensions._--Diameter of the shell 0.1, outer pores 0.01, their distance +0.007. + +_Habitat._--Mediterranean (Messina), surface, Haeckel. + + +2. _Ethmosphaera conosiphonia_, n. sp. (Pl. 12, figs. 5, 5_a_). + +Tubuli conical, their outer opening two thirds as broad as the inner, and +scarcely broader than their height. Ten to twelve pores on the quadrant. +Diameter of the outer pores twice as large as their distance from each +other. + +_Dimensions._--Diameter of the shell 0.17, outer pores 0.01, their distance +0.005. + +_Habitat._--Central Pacific, Station 268, depth 2900 fathoms. + + +{70}3. _Ethmosphaera polysiphonia_, n. sp. (Pl. 12, fig. 6). + +Tubuli conical, their outer opening three-fourths as broad as the inner and +three times as broad as their height. Sixteen to eighteen pores on the +quadrant. Diameter of the outer pores three times as large as their +distance apart. + +_Dimensions._--Diameter of the shell 0.2, outer pores 0.008, their distance +0.003. + +_Habitat._--West Tropical Pacific, Station 225, depth 4475 fathoms; also +fossil in Barbados and in Sicily. + + + +Subgenus 2. _Ethmosphaeromma_, Haeckel. + +_Definition._--Tubuli cylindrical, their outer opening about as large as +the inner. + + +4. _Ethmosphaera stenosiphonia_, n. sp. + +Tubuli cylindrical, short, quite contiguous, so that their diameter is six +times as large as their distance apart, but about equal to their height. +Nine to ten pores on the quadrant. + +_Dimensions._--Diameter of the shell 0.14, outer pores 0.012, their +distance 0.002. + +_Habitat._--Central Pacific, Station 271, surface. + + +5. _Ethmosphaera pachysiphonia_, n. sp. + +Tubuli cylindrical, twice as long as broad, very thick-walled, and nearly +contiguous, so that their diameter is five times as large as their distance +apart. The thickness of their wall is equal to their lumen. Twelve to +fourteen pores on the quadrant. + +_Dimensions._--Diameter of the shell 0.16, outer pores 0.01, their distance +0.002. + +_Habitat._--Central Pacific, Station 265, depth 2900 fathoms. + + +6. _Ethmosphaera leptosiphonia_, n. sp. + +Tubuli cylindrical, short, about as long as broad, very thin-walled and +fragile, separated by wide distances, which are three times as large as +their diameter. Six to seven pores on the quadrant. (Very similar to +_Siphonosphaera cyathina_, Pl. 6, fig. 10, but quite regular, all tubuli +retaining the same size and distance.) + +_Dimensions._--Diameter of the shell 0.12, outer pores 0.01, their distance +0.03. + +_Habitat._--North Atlantic, Faeroee Channel, John Murray; surface. + + +7. _Ethmosphaera macrosiphonia_, n. sp. + +Tubuli cylindrical, very elongated, four times as long as broad; their +bases separated by distances which are equal to their breadth. Eight to ten +tubuli on the quadrant. (The tubes are similar to those of _Siphonosphaera +serpula_, Pl. 6, fig. 6, but quite regular, straight, not curved, all of +the same size and at equal distances apart.) + +{71}_Dimensions._--Diameter of the shell 0.1, length of the tubes 0.04, +breadth 0.01, basal distance 0.01. + +_Habitat._--Indian Ocean, Cocos Islands, surface, Rabbe. + + + +Genus 18. _Sethosphaera_,[29] Haeckel, 1881, Prodromus, p. 452 (_sensu +emendato_). + +_Definition._--#Liosphaerida# with one single latticed sphere, with simple +shell-cavity; with shell-pores, which are prolonged on the inside into +centripetal, conical, or cylindrical tubuli. + +The genus _Sethosphaera_ differs from its ancestral form, _Cenosphaera_, by +the production of internal, centripetal, radial tubuli on the inside of the +shell (the contrary of the preceding genus _Ethmosphaera_). It corresponds +therefore to the social _Pharyngosphaera_; but in the latter the formation +of the shell and its tubes is more or less irregular, whilst in the former +each regular pore is prolonged into a regular tubule. + + +1. _Sethosphaera entosiphonia_, n. sp. + +Shell with smooth surface and regular circular pores, separated by +hexagonal frames, twice as broad as the bars. Six to eight on the quadrant. +Each pore is prolonged on the inside of the shell in a short conical +centripetal tube, twice as long as its diameter. + +_Dimensions._--Diameter of the shell 0.15, outer pores 0.008, bars 0.004, +length of the tubuli 0.015. + +_Habitat._--Central Pacific, Station 272, depth 2600 fathoms. + + +2. _Sethosphaera entosolenia_, n. sp. + +Shell with smooth surface and regular circular pores, without hexagonal +frames, of about the same breadth as the bars. Ten to twelve on the +quadrant. Each pore is prolonged on the inside of the shell into a thin +cylindrical centripetal tube, three times as long as its diameter. + +_Dimensions._--Diameter of the shell 0.2, outer pores and bars 0.006, +length of the tubuli 0.02. + +_Habitat._--Central Pacific, Station 268, depth 2900 fathoms. + + + +Subfamily CARPOSPHAERIDA,[30] Haeckel, 1881, Prodromus, p. 449. + +_Definition._--#Liosphaerida# with two concentric spherical lattice-shells, +which are united by radial beams. + + +_Carposphaera_,[31] Haeckel, 1881, Prodromus, p. 451. + +_Definition._--Liosphaerida with one medullary (intracapsular) and one +cortical (extracapsular) shell, both connected by radial beams piercing the +central capsule. + +{72}The genus _Carposphaera_ comprises a large number of double-shelled +#Sphaeroidea#, formerly united with _Haliomma_, but different from this +genus by the absence of radial spines. The shell is composed of two +concentric latticed spheres, the inner of which (or the medullary shell) is +situated within the central capsule, the other (or the cortical shell) +outside it. Both shells are connected by radial beams which pierce the wall +of the central capsule. The distance between the shells is at least as +large as (commonly much larger than) the radius of the inner shell, whilst +in the following genus, _Liosphaera_, that distance is much smaller than +this radius. + + + +Subgenus 1. _Melittosphaera_, Haeckel, 1881, Prodromus, p. 451. + +_Definition._--Pores of the cortical shell regular, hexagonal (or circular, +with hexagonal frames or lobes), all of nearly equal size and form. + + +1. _Carposphaera capillacea_, n. sp. + +Cortical shell very delicate, four times as broad as the similarly +constructed medullary shell, with regular hexagonal meshes (twenty to +twenty-five on the quadrant) and very thin thread-like bars. Both shells +connected by twenty (?) very thin radial beams. (Similar to _Heliosoma +radians_, Pl. 28, fig. 3, 3_a_, but with smooth surface, without any radial +spines.) + +_Dimensions._--Diameter of the outer shell 0.2, inner 0.05, pores 0.01, +bars below 0.001. + +_Habitat._--Central Pacific, Station 274, surface. + + +2. _Carposphaera cubaxonia_, n. sp. + +Cortical shell smooth, three times as broad as the medullary shell, with +regular hexagonal pores, four times as broad as the bars. Eight to ten +pores on the quadrant. Medullary shell with regular circular pores, twice +as broad as the bars. Both shells connected by six radial beams, which are +three-sided prismatical, opposite in pairs in the three dimensive axes. + +_Dimensions._--Diameter of the outer shell 0.15, inner 0.05; outer pores +0.01, inner 0.005. + +_Habitat._--South Pacific, Station 291, surface. + + +3. _Carposphaera infundibulum_, Haeckel. + + _Haliomma infundibuliforme_, Stoehr, 1880, Palaeontogr. Bd. xxvi. p. 87, + Taf. i. fig. 6. + +Cortical shell very thick-walled, two and a half times as broad as the +medullary shell, with rough surface and regular hexagonal, funnel-shaped +pores, of about the same breadth as the bars. Five to six on the quadrant. + +_Dimensions._--Diameter of the outer shell 0.1, inner 0.04, outer pores and +bars 0.01. + +_Habitat._--North Atlantic, Station 354; fossil in Tertiary rocks (Barbados +and Sicily). + + +{73}4. _Carposphaera melissa_, n. sp. + +Cortical shell thick walled, four times as broad as the medullary shell, +with regular circular, hexagonally framed pores, three times as broad as +the bars. Eight to ten pores on the quadrant. Medullary shell with simple +circular pores. + +_Dimensions._--Diameter of the outer shell 0.16, inner 0.04, outer pores +0.012, bars 0.004. + +_Habitat._--Central Pacific, Station 268, depth 2900 fathoms. + + +5. _Carposphaera melitomma_, n. sp. (Pl. 20, fig. 4). + + _Melitomma melittosphaera_, Haeckel, 1881; Prodromus et Atlas, _loc. + cit._ + +Cortical shell thick walled, with thorny surface, two and a half times as +broad as the medullary shell. Its pores regular, circular, twice as broad +as the bars, elegantly six-lobed, separated by crested hexagonal frames; in +each hexagon-corner a short conical papilla (alternating with a lobe). +Eight to ten pores on the quadrant. Medullary shell with small simple +circular pores. + +_Dimensions._--Diameter of the outer shell 0.17, inner 0.07, outer pores +0.01, bars 0.005, inner pores 0.005. + +_Habitat._--Central Pacific, Stations 266 to 274, in various depths. + + + +Subgenus 2. _Cerasosphaera_, Haeckel, 1881, Prodromus, p. 451. + +_Definition._--Pores of the cortical shell regular, circular, without +hexagonal frames, all of nearly equal size and form. + + +6. _Carposphaera cerasus_, n. sp. + +Cortical shell thin walled, smooth, twice as broad as the medullary shell; +both with regular circular pores, six times as broad as the bars. Twelve to +fifteen pores on the quadrant. Outer pores twice as large as the inner. + +_Dimensions._--Diameter of the outer shell 0.24, inner 0.12; outer pores +0.016, inner 0.008. + +_Habitat._--Central Pacific, Station 271, surface. + + +7. _Carposphaera apiculata_, Haeckel. + + ? _Haliomma apiculatum_, Ehrenberg, 1872; Monatsber. d. k. preuss. Akad. + d. Wiss. Berlin, p. 313. + +Cortical shell thin-walled, covered with numerous short conical thorns, +three times as broad as the medullary shell. Pores regular, circular, four +times as broad as the bars. Six to eight pores on the quadrant. + +_Dimensions._--Diameter of the outer shell 0.15, inner 0.05, outer pores +0.012, bars 0.03. + +_Habitat._--North Pacific, California, depth 2000 fathoms; Station 254, +depth 3025 fathoms. + + +{74}8. _Carposphaera entactinia_, Haeckel. + + _Haliomma entactinia_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. + Berlin, p. 74, Taf. xxvi. fig. 4. + +Cortical shell thick walled, rough, twice as broad as the medullary shell; +both shells with regular circular pores, twice as broad as the bars. Six to +eight pores on the quadrant. Outer pores half as broad as the inner. Both +shells connected by very numerous (twenty-four to forty-eight or more) +radial beams. + +_Dimensions._--Diameter of the outer shell 0.12, inner 0.06, outer pores +0.008, bars 0.004, inner pores 0.004. + +_Habitat._--Cosmopolitan; Atlantic and Pacific, in various depths; fossil +in Barbados and Sicily. + + +9. _Carposphaera modesta_, Haeckel. + + _Haliomma modestum_, Stoehr, 1880, Palaeontogr. Bd. xxvi. p. 86, Taf. i. + fig. 5. + +Cortical shell thick walled, rough, three times as broad as the medullary +shell, with regular circular pores of the same breadth as the bars. Eight +to twelve pores on the quadrant. (Very common, like the preceding species, +and connected with it by numerous intermediate forms.) + +_Dimensions._--Diameter of the outer shell 0.12 to 0.2, inner 0.04 to 0.07, +pores and bars 0.006 to 0.008. + +_Habitat._--Atlantic and Pacific, from many Stations and at various depths; +fossil in Barbados and Sicily. + + +10. _Carposphaera belladonna_, n. sp. + +Cortical shell thick walled, smooth, five times as broad as the medullary +shell, with regular circular pores of the same breadth as the bars. Twenty +to twenty-two pores on the quadrant. + +_Dimensions._--Diameter of the outer shell 0.3, inner 0.06, outer pores and +bars 0.004. + +_Habitat._--North Atlantic, Faeroee Channel, John Murray. + + +11. _Carposphaera areca_, n. sp. + +Cortical shell very thick walled, rough, twice as broad as the medullary +shell, with regular circular pores half as broad as the bars. Eight to ten +pores on the quadrant. + +_Dimensions._--Diameter of the outer shell 0.12, inner 0.06, outer pores +0.03, bars 0.006. + +_Habitat._--Indian Ocean, Ceylon, Haeckel, surface. + + + +Subgenus 3. _Prunosphaera_, Haeckel, 1881, Prodromus, p. 451. + +_Definition._--Pores of the cortical shell irregular polygonal, of unequal +size or dissimilar form. + + +12. _Carposphaera prunulum_, n. sp. + +Cortical shell thin walled, smooth, four times as broad as the medullary +shell, with large irregular polygonal pores, four to eight times as broad +as the bars. Connecting beams between them numerous. + +{75}_Dimensions._--Diameter of the outer shell 0.24, inner 0.06, outer +pores 0.008 to 0.016, bars 0.002. + +_Habitat._--South Atlantic, Station 325, surface. + + +13. _Carposphaera corypha_, n. sp. + +Cortical shell thin walled, rough, three times as broad as the medullary +shell, with irregular polygonal pores, three to six times as broad as the +bars. Connecting beams between the two shells twenty, regularly disposed. + +_Dimensions._--Diameter of the outer shell 0.15, inner 0.05, outer pores +0.01 to 0.02, bars 0.003. + +_Habitat._--South Pacific, Station 300, surface. + + +14. _Carposphaera borassus_, n. sp. + +Cortical shell thick walled, smooth, three times as broad as the medullary +shell, with irregular polygonal pores, two to four times as broad as the +bars. Connecting beams between the two shells six, opposite by pairs in the +three dimensive axes. (Similar to _Hexalonche aristarchi_, Pl. 22, fig. 3, +but without external radial spines.) + +_Dimensions._--Diameter of the outer shell 0.12, inner 0.04, outer pores +0.01 to 0.02, bars 0.005. + +_Habitat._--Central Pacific, Station 268, surface. + + + +Subgenus 4. _Phoenicosphaera_, Haeckel. + +_Definition._--Pores of the cortical shell irregular roundish, of unequal +size or form. + + +15. _Carposphaera nobilis_, Haeckel. + + _Haliomma nobile_, Ehrenberg, 1844, Monatsber. d. k. preuss. Akad. d. + Wiss. Berlin, p. 268; Abhandl., 1875, Taf. xxvii. fig. 6. + +Cortical shell thin walled, rough, twice as broad as the medullary shell, +with irregular roundish pores, two to four times as broad as the bars. + +_Dimensions._--Diameter of the outer shell 0.1, inner 0.05, outer pores +0.01 to 0.02, bars 0.006. + +_Habitat._--Cosmopolitan; Atlantic, Indian, Pacific, at various depths; +fossil in Jurassic, Cretaceous, and Tertiary rocks. + + +16. _Carposphaera micrococcus_, n. sp. + +Cortical shell thin walled, rough, seven times as broad as the medullary +shell, with irregular roundish pores, three to six times as broad as the +bars. + +_Dimensions._--Diameter of the outer shell 0.2, inner 0.03, outer pores +0.012 to 0.025, bars 0.004. + +_Habitat._--South Atlantic, Station 330, surface. + + +{76}17. _Carposphaera maxima_, n. sp. + +Cortical shell thin walled, smooth, five times as broad as the medullary +shell, with irregular roundish pores, of about the same breadth as the +bars. + +_Dimensions._--Diameter of the outer shell 0.4, inner 0.08, pores and bars +0.004 to 0.008. + +_Habitat._--Central Pacific, Station 272, depth 2600 fathoms. + + +18. _Carposphaera nodosa_, n. sp. (Pl. 28, figs. 2, 2_a_). + + _Anthomma nodosum_, Haeckel, 1879, Atlas, _loc. cit._ + +Cortical shell thick walled, covered with forty to fifty scattered +pyramidal nodules, two and a half times as broad as the medullary shell, +connected with it by very numerous thin radial beams. Outer and inner pores +irregular roundish or polygonal, two to three times as broad as the bars. +(This species in consequence of the cortical nodules may represent a +peculiar genus, analogous to _Conosphaera_, called _Anthomma_.) + +_Dimensions._--Diameter of the outer shell 0.13, inner 0.05, inner and +outer pores 0.008 to 0.012, bars 0.004. + +_Habitat._--Central Pacific, Station 271, depth 2425 fathoms. + + + +Genus 20. _Liosphaera_,[32] Haeckel, 1881, Prodromus, p. 449. + +_Definition._--#Liosphaerida# with two cortical (extracapsular) shells +(without a medullary or intracapsular shell). + +The genus _Liosphaera_ agrees with the preceding _Carposphaera_ in the +possession of two concentric latticed spheres; but whilst in the latter +genus the inner sphere is a medullary one (intracapsular), the outer a +cortical shell (extracapsular), both connected by radial beams piercing the +capsule-wall, here in _Liosphaera_ the central capsule lies freely within +the inner lattice shell and is not pierced by radial beams. Therefore both +shells are here cortical shells, both separated by a distance, which is +constantly much smaller than the radius of the inner shell; whereas in +_Carposphaera_ this distance is at least as large as that radius (commonly +much larger). In _Carposphaera_ the number of pores in both shells is never +the same; in several species of _Liosphaera_ this number is the same, each +outer regular hexagonal pore exactly corresponding to an inner; the six +corners of each connected by six short radial beams. + + + +Subgenus 1. _Melitomma_, Haeckel. + +_Definition._--Pores of both shells regular, in each shell all of nearly +equal size and form. + + +1. _Liosphaera hexagonia_, n. sp. (Pl. 20, fig. 3). + +Both shells with the same number of pores, exactly corresponding, about ten +on the quadrant. {77}All pores regular, or subregular, hexagonal; the outer +twice as broad as the inner. Outer bars very thin, thread-like; inner bars +thick, one-third as broad as the pores. Surface smooth. Both shells +connected by numerous radial beams, their distance one-third as large as +the radius of the inner shell. + +_Dimensions._--Diameter of the outer shell 0.16, inner 0.12, distance of +both 0.02; outer pores 0.014, inner pores 0.007. + +_Habitat._--Central Pacific, Station 272, depth 2600 fathoms. + + +2. _Liosphaera rhodococcus_, n. sp. + +Both shells with the same number of pores, exactly corresponding, about +twelve on the quadrant. All pores regular or subregular; the inner +circular, with elegant six-lobed frames, twice as broad as the bars; the +outer hexagonal, with very thin thread-like bars. All corners of the outer +and inner hexagons connected by thin, bristle-shaped radial beams. (Similar +to _Haliomma rhodococcus_, Pl. 19, fig. 6; but with smooth surface and +regular hexagonal pores of the outer shell.) + +_Dimensions._--Diameter of the outer shell 0.2, inner 0.16, distance of +both 0.02; outer pores 0.03, inner 0.01. + +_Habitat._--Central Pacific, Station 266, depth 2750 fathoms. + + +3. _Liosphaera porulosa_, n. sp. + +Both shells with regular hexagonal pores; their number in the outer shell +seven times as great as in the inner. Pores of the stout inner shell large, +three times as broad as the bars, about eight on the quadrant. From each +hexagon-corner arises one bristle-shaped radial beam; their distal ends are +united by threads (three from each), forming the large meshes of the +delicate outer shell. Each of these is divided by very thin threads into +seven small circular porules, one central and six around it. + +_Dimensions._--Diameter of the outer shell 0.25, inner 0.2, distance of +both 0.025; outer pores 0.04, their porules 0.012, inner pores 0.15. + +_Habitat._--Indian Ocean, Sunda Strait, Rabbe; surface. + + + +Subgenus 2. _Craspedomma_, Haeckel. + +_Definition._--Pores of both shells irregular, in each shell differing +either in form or size. + + +4. _Liosphaera peridromium_, n. sp. + +Both shells with the same number of large, polygonal, very irregular pores, +exactly corresponding (about eight to ten on the quadrant); both with a +very delicate thin framework. From the thread-like bars of the inner, very +large and thin-walled, sphere arise perpendicularly innumerable short +bristles of equal length, which are united at equal distances by tangential +thread-like bars, parallel to the former, composing the outer shell. Each +mesh is, therefore, surrounded by a delicate ballister or rail. + +{78}_Dimensions._--Diameter of the outer shell 0.42, inner 0.4, distance of +both 0.01; diameter of the meshes 0.02 to 0.06. + +_Habitat._--North Pacific, Station 250, surface. + + +5. _Liosphaera polypora_, n. sp. (Pl. 20, fig. 2). + +Both shells with small irregular roundish pores, of about the same size as +the bars between them; twenty to thirty on the quadrant. The pores of the +outer shell somewhat smaller, therefore much more numerous than the pores +of the inner shell. Distance between the two shells about one-third as +great as the radius of the inner. Both shells connected by numerous thin +radial beams. Surface smooth or a little rough. + +_Dimensions._--Diameter of the outer shell 0.18, inner 0.14, distance of +both 0.02; pores and bars 0.003 to 0.005. + +_Habitat._--West Tropical Pacific, Station 225, depth 4475. + + + +Subfamily THECOSPHAERIDA,[33] Haeckel, 1881, Prodromus, pp. 449, 452. + +_Definition._--#Liosphaerida# with three concentric spherical +lattice-shells, which are united by radial beams. + + + +Genus 21. _Thecosphaera_,[34] Haeckel, 1881, Prodromus, p. 452. + +_Definition._--#Liosphaerida# with two medullary (intracapsular) shells and +one cortical (extracapsular) shell. + +The genus _Thecosphaera_ comprises a large number of triple-shelled +#Sphaeroidea#, formerly united with _Actinomma_, but different from this +genus in the absence of radial spines. The latticed shell is composed of +three concentric spheres, two of which lie within the central capsule +(medullary shells), and one outside (cortical shell). This latter is +connected with the former by radial beams piercing the wall of the central +capsule. From the following _Rhodosphaera_ (with one medullary and two +cortical shells) _Carposphaera_ differs also by the distance of the three +shells. In the former the distance between the two outer shells is much +smaller, in the latter much larger, than the distance between the inner +shells. + + + +Subgenus 1. _Thecosphaerantha_, Haeckel. + +_Definition._--Pores of the cortical shell regular, hexagonal, or circular, +with hexagonal frames or lobes, all of nearly equal size and form. + + +{79}1. _Thecosphaera triplodictyon_, n. sp. + +Cortical shell thin walled, smooth, with regular, hexagonal pores, four +times as broad as the bars. Radial proportion of the three spheres = +1 : 2 : 8. Both medullary shells with regular circular pores, twice as +broad as the bars, the inner half as broad as the outer. All three shells +connected by six thin radial beams, opposite in pairs in the three +dimensive axes. + +_Dimensions._--Diameter of the outer shell 0.2, middle 0.05, inner 0.025; +cortical pores 0.012, bars 0.003. + +_Habitat._--Central Pacific, Station 271, surface. + + +2. _Thecosphaera phaenaxonia_, n. sp. + +Cortical shell thick walled, rough, with regular, circular, hexagonally +framed pores, twice as broad as the bars. Radial proportion of the three +spheres = 1 : 2 : 6. Both medullary shells with regular hexagonal pores and +thin bars. All three shells connected by six prismatic radial beams, +opposite in pairs in the three dimensive axes. (Shell similar to +_Hexacontium sceptrum_, Pl. 24, fig. 1, 1_a_, but without external spines.) + +_Dimensions._--Diameter of the outer shell 0.12, middle 0.04, inner 0.02; +cortical pores 0.01, bars 0.005. + +_Habitat._--North Pacific, Station 253, surface. + + +3. _Thecosphaera favosa_, n. sp. + +Cortical shell thick walled, thorny, with regular, circular, hexagonally +framed pores, of the same breadth as the bars. Radial proportion of the +three spheres = 1 : 3 : 10. Both medullary shells with regular circular +pores, connected with the former by twelve short prismatic, regularly +disposed radial beams. + +_Dimensions._--Diameter of the outer shell 0.2, middle 0.06, inner 0.02; +cortical pores and bars 0.008. + +_Habitat._--Central Pacific, Station 268, surface; also fossil in Barbados. + + +4. _Thecosphaera floribunda_, n. sp. + +Cortical shell thick walled, smooth, with regular, elegantly six-lobed +pores, three times as broad as the bars. Radial proportion of the three +spheres = 1 : 2 : 4. Both medullary shells with simple regular circular +pores, connected with the former by six dimensive radial beams. (Similar to +_Hexacontium floridum_, Pl. 24, fig. 4, but without external spines.) + +_Dimensions._--Diameter of the outer shell 0.12, middle 0.06, inner 0.03; +cortical pores 0.01, bars 0.0033. + +_Habitat._--Central Pacific, Station 266, depth 2750 fathoms. + + + +{80}Subgenus 2. _Thecosphaerella_, Haeckel. + +_Definition._--Pores of the cortical shell regular, circular, without +hexagonal frames or lobes, all of nearly equal size and form. + + +5. _Thecosphaera inermis_, Haeckel. + + _Actinomma inerme_, Haeckel, 1862, Monogr. d. Radiol., p. 440, Taf. xxiv. + fig. 5. + + _Haliomma inerme_, Haeckel, 1860, Monatsber. d. k. preuss. Akad. d. Wiss. + Berlin, p. 815. + +Cortical shell thin walled, rough, with regular circular pores, twice as +broad as the bars. Radial proportion of the three spheres and of their +circular regular pores = 1 : 2 : 4. All three spheres connected by twelve +regularly disposed radial beams. + +_Dimensions._--Diameter of the outer shell 0.1, middle 0.05, inner 0.025; +cortical pores 0.006, bars 0.003. + +_Habitat._--Cosmopolitan; Mediterranean, Atlantic, Indian, Pacific, at many +Stations and at various depths. + + +6. _Thecosphaera aequorea_, Haeckel. + + _Haliomma aequorea_, Ehrenberg, 1844, Monatsber. d. k. preuss. Akad. d. + Wiss. Berlin, p. 83; Mikrogeol., 1854, Taf. xxii. fig. 35. + + _Actinomma aequorea_, Haeckel, 1862, Monogr. d. Radiol., p. 443. + +Cortical shell thick walled, smooth, with regular circular pores of the +same breadth as the bars. Radial proportion of the three spheres and of +their regular pores = 1 : 2 : 6 or = 1 : 3 : 9; they are connected by six +radial beams, opposite by pairs in the three dimensive axes. + +_Dimensions._--Diameter of the outer shell 0.08 to 0.12, middle 0.03 to +0.04, inner 0.09 to 0.12; cortical pores and bars about 0.006. + +_Habitat._--Mediterranean, Corfu, surface; fossil in Greece and Sicily. + + +7. _Thecosphaera medusa_, Haeckel. + + _Haliomma medusa_, Ehrenberg, 1838, Abhandl. d. k. Akad. d. Wiss. Berlin, + p. 130; Mikrogeol., 1854, Taf. xxii. figs. 33, 34. + + _Actinomma medusa_, Haeckel, 1862, Monogr. d. Radiol., p. 444. + + _Actinomma medusa_, Stoehr, 1880, Palaeontogr., Bd. xxvi. p. 90, Taf. ii. + fig. 3. + +Cortical shell thick walled, rough or thorny, with regular circular pores +of the same breadth as the bars. Radial proportion of the three spheres = +1 : 2 : 4 (or 1 : 2.5 : 6); they are connected by four radial beams, +crossed by pairs in two diameters, perpendicular one to another. + +_Dimensions._--Diameter of the outer shell 0.08 to 0.12, middle 0.04 to +0.06, inner 0.02 to 0.025; cortical pores and bars in average 0.005. + +_Habitat._--Fossil in Tertiary rocks of Barbados and the Mediterranean. + + +{81}8. _Thecosphaera entactinia_, n. sp. + +Cortical shell thick walled, smooth, with regular circular pores of the +same breadth as the bars. Radial proportion of the three spheres = +1 : 3 : 12; they are connected by very numerous (forty to fifty, or more) +thin radial beams. + +_Dimensions._--Diameter of the outer shell 0.24, middle 0.06, inner 0.02; +cortical pores and bars 0.008. + +_Habitat._--Central Pacific, Station 268, depth 2900 fathoms. + + +9. _Thecosphaera micropora_, n. sp. + +Cortical shell thin walled, smooth, with very small and numerous, regular, +circular pores, half as broad as the bars. Radial proportion of the three +shells = 1 : 2 : 5; they are connected by twenty regularly disposed radial +beams. + +_Dimensions._--Diameter of the outer shell 0.2, middle 0.08, inner 0.04; +cortical pores 0.002, bars 0.004. + +_Habitat._--South Pacific, Station 288, surface. + + + +Subgenus 3. _Thecosphaerina_, Haeckel. + +_Definition._--Pores of the cortical shell irregular polygonal, of unequal +size or dissimilar form. + + +10. _Thecosphaera capillacea_, n. sp. + +Cortical shell thin walled, smooth, with irregular polygonal pores, three +to six times as broad as the bars. Both medullary shells with similar, but +smaller, pores. Radial proportion of the three spheres = 1 : 3 : 8; they +are connected by very numerous (sixty to eighty or more) thin radial beams. + (Similar to _Actinomma capillaceum_, Pl. 29, fig. 6, but without external +spines.) + +_Dimensions._--Diameter of the outer shell 0.2, middle 0.075, inner 0.025; +cortical pores 0.006 to 0.012, bars 0.002. + +_Habitat._--North Pacific, Station 250, surface. + + +11. _Thecosphaera diplococcus_, n. sp. + +Cortical shell thick walled, rough, with large irregular polygonal pores, +two to three times as broad as the bars. Both medullary shells with small +regular circular pores. Radial proportion of the three spheres = 1 : 2 : 6; +they are connected by twenty (?) stout radial beams. + +_Dimensions._--Diameter of the outer shell 0.12, middle 0.04, inner 0.02; +cortical pores 0.008 to 0.012, bars 0.004. + +_Habitat._--South Atlantic, Station 330, surface. + + + +Subgenus 4. _Thecosphaeromma_, Haeckel. + +_Definition._--Pores of the cortical shell irregular, roundish, of unequal +size or dissimilar form. + + +{82}12. _Thecosphaera dodecactis_, n. sp. + +Cortical shell thin walled, smooth, with large irregular roundish pores, +two to eight times as broad as the bars. Both medullary shells with regular +circular pores, twice as broad as the bars. Radial proportion of the three +spheres = 1 : 2 : 5; they are connected by twelve regularly disposed stout +radial beams. + +_Dimensions._--Diameter of the outer shell 0.2, middle 0.08, inner 0.04; +cortical pores 0.004 to 0.016, bars 0.002. + +_Habitat._--Central Pacific, Station 263, depth 2650 fathoms. + + +13. _Thecosphaera icosactis_, n. sp. + +Cortical shell thin walled, with small irregular roundish pores, two to +four times as broad as the bars. Both medullary shells with similar but +smaller pores. Radial proportion of the three spheres = 1 : 3 : 8; they are +connected by twenty thin radial beams. + +_Dimensions._--Diameter of the outer shell 0.32, middle 0.12, inner 0.04; +cortical pores 0.005 to 0.012, bars 0.003. + +_Habitat._--North Pacific, Station 244, depth 2900 fathoms. + + +14. _Thecosphaera maxima_, n. sp. + +Cortical shell thin walled, with small irregular roundish pores, two to six +times as broad as the bars. Both medullary shells with similar, but +smaller, pores. Radial proportion of the three spheres = 1 : 3 : 9; they +are connected by numerous (forty to sixty or more) thin radial beams. + +_Dimensions._--Diameter of the outer shell 0.45, middle 0.15, inner 0.05; +cortical pores 0.008 to 0.024, bars 0.004. + +_Habitat._--Central Pacific, Station 272, depth 2600 fathoms. + + + +Genus 22. _Rhodosphaera_,[35] Haeckel, 1881, Prodromus, p. 452. + +_Definition._--#Liosphaerida# with one medullary (intracapsular) shell and +two cortical (extracapsular) shells. + +The genus _Rhodosphaera_ differs from the preceding _Thecosphaera_ in the +same manner in which, among the Dyosphaerida, _Liosphaera_ differs from +_Carposphaera_. The cortical shell is double, composed of two not far +distant shells, lying outside the central capsule. The distance between the +shells is much smaller than the radius of the inner shell. This is +connected by radial beams (piercing the central capsule) with the small +central medullary shell. + + + +Subgenus 1. _Rhodosphaerella_, Haeckel. + +_Definition._--Pores of both cortical shells regular, in each shell all of +nearly equal size and form. + + +{83}1. _Rhodosphaera hexagonia_, n. sp. + +Both cortical shells with the same number of regular hexagonal pores; the +inner four times as broad as the bars, and half as broad as the outer +pores, which are separated by thread-like bars. Medullary shell only +one-fourth as broad as the inner cortical shell, with regular hexagonal +pores of half the size. (Differs from the similar _Liosphaera hexagonia_, +Pl. 20, fig. 3, by the possession of a medullary shell.) + +_Dimensions._--Diameter of the outer shell 0.2, middle 0.16, inner 0.04; +outer pores 0.013, middle 0.008, inner 0.004. + +_Habitat._--Central Pacific, Station 266, depth 2750 fathoms. + + +2. _Rhodosphaera melitomma_, n. sp. + +Both cortical shells with the same number of regular pores; the inner +regular, circular, twice as broad as the bars, with elegant hexagonal +frames and six roundish lobes alternating with the six radial spines which +arise from the hexagon-corners; these short conical spines are connected at +the distal end (at equal distances from the centre) by delicate threads +(three from each spine), which form the delicate external shell. Medullary +shell one-third as broad as the inner cortical shell, with small, simple, +regular circular pores. (If in _Carposphaera melitomma_, Pl. 20, fig. 4, +the distal ends of the spines became united by a cobweb-like outer shell, +this species would be formed.) + +_Dimensions._--Diameter of the outer shell 0.22, middle 0.18, inner 0.06; +outer pores 0.025, middle 0.0125, inner 0.005. + +_Habitat._--Central Pacific, Station 270, depth 2925 fathoms. + + + +Subgenus 2. _Rhodosphaeromma_, Haeckel. + +_Definition._--Pores of both cortical shells irregular, in each shell of +unequal size or dissimilar form. + + +3. _Rhodosphaera palliata_, n. sp. + +Both cortical shells with an unequal number of irregular roundish pores; +the outer pores somewhat smaller and much more numerous than the inner +pores; the bars between the latter are thicker. Medullary shell about one +quarter as broad as the inner cortical shell, with regular circular pores. + +_Dimensions._--Diameter of the outer shell 0.4, middle 0.36, inner 0.08; +outer pores on an average 0.008, middle 0.012, inner 0.004. + +_Habitat._--Fossil in Barbados. + + +4. _Rhodosphaera pentaphylla_, n. sp. + +Both cortical shells with unequal number of irregular roundish pores; the +inner pores large, three to four times as broad as the bars; to each inner +pore corresponds a group of five smaller {84}outer pores, like the five +petals of a flower. Medullary shell half as broad as the inner cortical +shell, with regular circular pores. + +_Dimensions._--Diameter of the outer shell 0.25, middle 0.2, inner 0.1; +outer pores on an average 0.006, middle 0.012, inner 0.004. + +_Habitat._--Central Pacific, Station 268, depth 2900 fathoms. + + + +Subfamily CROMYOSPHAERIDA,[36] Haeckel, 1881, Prodromus, pp. 449, 453. + +_Definition._--#Liosphaerida# with four concentric spherical latticed +shells, united by radial beams. + + + +Genus 23. _Cromyosphaera_,[37] Haeckel, 1881, Prodromus, p. 453. + +_Definition._--#Liosphaerida# with two intracapsular (medullary) shells and +two extracapsular (cortical) shells; the former united with the latter by +radial beams piercing the wall of the central capsule. + +The genus _Cromyosphaera_ is the only known genus of Cromyosphaerida, or of +such #Sphaeroidea#, the smooth shell of which is composed of two medullary +and two cortical shells. There may possibly be other Cromyosphaerida, in +which the shell is composed of one simple medullary and three cortical +shells, or only of four extra-capsular cortical shells; but such have not +as yet been observed. _Caryosphaera polysphaerica_, Buetschli, 1882 (L. N. +41, Taf. xxiii. fig. 12) is probably a _Cromyosphaera_ (fossil in +Barbados). + + +1. _Cromyosphaera quadruplex_, n. sp. (Pl. 30, fig. 9). + +Radial proportion of the four spheres = 1 : 2 : 4 : 5. Outer cortical shell +smooth, with large regular hexagonal pores, ten times as broad as the bars; +inner cortical shell with irregular polygonal pores, five times as broad as +the bars. Both medullary shells with regular circular pores of the same +breadth as the bars. + +_Dimensions._--Diameter of the four spheres--(A) 0.16, (B) 0.12, (C) 0.06, +(D) 0.03. + +_Habitat._--Central Pacific, Station 265, depth 2900 fathoms. + + +2. _Cromyosphaera rosetta_, n. sp. + +Radial proportion of the four spheres = 1 : 2 : 8 : 10. Outer cortical +shell smooth, with regular hexagonal pores and very thin bars; inner +cortical shell with the same number of exactly corresponding, regular +circular, hexagonally framed pores, twice as broad as the bars; the corners +of the outer and inner hexagons united by radial bristles. Both medullary +shells with regular circular pores, twice as broad as the bars. + +_Dimensions._--Diameter of the four spheres--(A) 0.2, (B) 0.16, (C) 0.04, +(D) 0.02. + +_Habitat._--Central Pacific, Station 271, depth 2425 fathoms. + + +{85}3. _Cromyosphaera bigemina_, n. sp. + +Radial proportion of the four spheres = 1 : 2 : 7 : 8. Outer cortical shell +smooth, with regular hexagonal pores and very thin bars; inner cortical +shell with the same number of exactly corresponding, regular circular +pores. Both medullary shells with regular circular pores of the same +breadth as the bars. (Somewhat similar to _Hexacromyon elegans_, Pl. 24, +fig. 9, also with six inner radial beams, but without external radial +spines.) + +_Dimensions._--Diameter of the four spheres--(A) 0.2, (B) 0.17, (C) 0.05, +(D) 0.025. + +_Habitat._--North Pacific, Station 241, depth 2300 fathoms. + + +4. _Cromyosphaera cepa_, n. sp. + +Radial proportion of the four spheres = 1 : 2 : 4 : 5. All four shells of +the same structure, thick-walled, with regular circular pores, two to four +times as broad as the bars; the size of the pores increases gradually from +the inner to the outer shell. Surface thorny. Distance between the second +and third shells twice as great as that between the others. + +_Dimensions._--Diameter of the four spheres--(A) 0.125, (B) 0.1, (C) 0.05, +(D) 0.025. + +_Habitat._--Fossil in Barbados. + + +5. _Cromyosphaera scorodonium_, n. sp. + +Radial proportion of the four spheres = 1 : 2 : 3 : 4. All four shells of +the same structure, thin-walled, with irregular roundish pores, two to four +times as broad as the bars; the size of the pores increasing gradually from +the inner to the outer shell. Surface smooth. Distance between each two +shells equal to the diameter of the innermost. + +_Dimensions._--Diameter of the four spheres--(A) 0.12, (B) 0.09, (C) 0.06, +(D) 0.03. + +_Habitat._--Central Pacific, Station 268, depth 2900 fathoms; also fossil +in Barbados. + + +6. _Cromyosphaera antarctica_, n. sp.. + +Radial proportion of the four spheres = 1 : 2 : 5 : 7. Both cortical shells +with irregular polygonal roundish pores; the outermost with thinner bars +and rough surface, the inner with thicker bars. Both medullary shells with +irregular roundish pores. + +_Dimensions._--Diameter of the four spheres--(A) 0.18, (B) 0.12, (C) 0.05, +(D) 0.025. + +_Habitat._--Antarctic Ocean; in very large number, together with +_Rhizosphaera antarctica_, in the diatomaceous ooze of Station 157 (3rd +March 1874); depth 1950 fathoms. + + + +Subfamily CARYOSPHAERIDA,[38] Haeckel, 1881, Prodromus, pp. 449, 454. + +_Definition._--#Liosphaerida# with numerous (five or more) concentric +spherical latticed shells, united by radial beams. + + + +{86}Genus 24. _Caryosphaera_,[39] Haeckel, 1881, Prodromus, p. 454. + +_Definition._--#Liosphaerida# with two intracapsular (medullary) shells and +three or more extracapsular (cortical) shells; the former united with the +latter by radial beams piercing the wall of the central capsule. + +The genus _Caryosphaera_, the only observed form of this subfamily, +comprises those #Liosphaerida# in which the shell is composed of two +medullary and three or more cortical shells. Such forms (without radial +spines) are very rare; I observed only two species, one with five, the +other with six shells. They are derived from _Cromyosphaera_ by further +apposition of outer cortical shells. + + +1. _Caryosphaera pentalepas_, n. sp. + +Shell composed of five concentric spheres, with radial proportion = +1 : 2 : 8 : 10 : 12. Both medullary shells with regular circular pores, +twice as broad as the bars. First cortical shell with regular, circular, +hexagonally framed pores, three times as broad as the bars; second cortical +shell with regular hexagonal pores, four times as broad as the bars; third +(outermost) cortical shell with regular hexagonal pores and very thin +thread-like bars. Surface smooth. + +_Dimensions._--Diameter of the five shells--(A) 0.02, (B) 0.04, (C) 0.16, +(D) 0.2, (E) 0.24. + +_Habitat._--Central Pacific, Station 274, depth 2750 fathoms. + + +2. _Caryosphaera hexalepas_, n. sp. + +Shell composed of six concentric spheres, with the radial proportion = +1 : 2 : 4 : 5 : 6 : 8. All six shells with regular circular pores, two to +four times as broad as the bars, with increasing size from the centrum +against the smooth surface. + +_Dimensions._--Diameter of the six shells--(A) 0.025, (B) 0.05, (C) 0.1, +(D) 0.13, (E) 0.16, (F) 0.2. + +_Habitat._--Central Pacific, Station 268, depth 2900 fathoms; also fossil +in Barbados. + + + +Subfamily PLEGMOSPHAERIDA,[40] Haeckel, 1881, Prodromus, p. 455. + +_Definition._--#Liosphaerida# with spongy spherical shell, with or without +latticed medullary shell in the centre. + + + +Genus 25. _Styptosphaera_,[41] Haeckel, 1881, Prodromus, p. 455. + +_Definition._--#Liosphaerida# forming a solid sphere of spongy framework, +without enclosed medullary shell, and without central cavity. + +{87}The genus _Styptosphaera_ presents a spherical shell with smooth or +rough surface (without radial spines), the whole mass of which is composed +of looser or denser spongy wicker-work. + + +1. _Styptosphaera spumacea_, n. sp. + +Spongy framework of the solid sphere loose, with large polygonal meshes of +slightly different size, ten to twenty times as broad as the bars. +Structure of the whole spongy sphere the same. Central capsule filled with +crystals. Surface smooth. + +_Dimensions._--Diameter of the sphere 0.32, of the central capsule 0.26, +meshes 0.01 to 0.02, bars 0.001. + +_Habitat._--North Pacific, Station 236, surface. + + +2. _Styptosphaera spongiacea_, n. sp. + +Spongy framework in the central part of the solid sphere much more compact +than in the peripheral part, becoming gradually looser towards the rough +surface. Meshes in the centre three to five times, in the periphery fifteen +to twenty times as broad as the bent bars. + +_Dimensions._--Diameter of the sphere 0.45, inner meshes 0.006 to 0.01, +outer meshes 0.03 to 0.04, bars 0.002. + +_Habitat._--Central Pacific, Station 271, surface. + + +3. _Styptosphaera stupacea_, n. sp. + +Spongy framework of the solid sphere rather compact, everywhere of the same +structure, with roundish, nearly equal meshes, six to eight times as broad +as the bars. Surface rough with prominent thorns. + +_Dimensions._--Diameter of the sphere 0.22, meshes 0.01 to 0.012, bars +0.0015. + +_Habitat._--South Pacific, Station 291, surface. + + + +Genus 26. _Plegmosphaera_, Haeckel,[42] 1881, Prodromus, p. 455. + +_Definition._--#Liosphaerida# forming a hollow sphere of spongy framework, +without a medullary shell in the central cavity. + +The genus _Plegmosphaera_ develops a large hollow sphere, the wall of which +is composed of looser or denser spongy wicker-work. On the inner as well as +on the outer face of the spongy shell-wall may be present a simple +lattice-sphere from which the threads of the framework arise; but in some +species these lattice-plates are quite absent. + + + +{88}Subgenus 1. _Plegmosphaerantha_, Haeckel. + +_Definition._--Inside and outside of the spongy shell-wall smooth, closed +by a lattice-plate with polygonal meshes. + + +1. _Plegmosphaera maxima_, n. sp. + +Radius of the spherical shell-cavity eight to ten times as great as the +thickness of the thin spongy wall. Inside and outside of the wall smooth, +closed by a lattice-plate with irregular polygonal meshes. Only three or +four meshes in the thickness of the wall. + +_Dimensions._--Diameter of the spongy sphere 0.8 to 1.0 mm., of its inner +cavity 0.7 to 0.8, meshes 0.01 to 0.02, bars 0.002 to 0.003, central +capsule 0.5 to 0.6, nucleus 0.1 to 0.15. + +_Habitat._--Central Pacific, Station 271, surface. + + +2. _Plegmosphaera coelopila_, n. sp. + +Radius of the spherical shell-cavity eight to ten times as great as the +thickness of the spongy wall. Inside and outside of the wall closed by a +smooth lattice-plate with irregular polygonal meshes, five to ten times as +broad as the bars. + +_Dimensions._--Diameter of the shell 0.32, of its cavity 0.26, meshes 0.01 +to 0.02, bars 0.002. + +_Habitat._--North Atlantic, Faeroee Channel, Gulf Stream, John Murray. + + +3. _Plegmosphaera pachypila_, n. sp. + +Radius of the spherical shell-cavity about equal to the thickness of the +spongy wall. Inside and outside of the wall closed by a smooth +lattice-plate with irregular polygonal meshes, three to six times as broad +as the bars. + +_Dimensions._--Diameter of the shell 0.24, of its cavity 0.12. + +_Habitat._--North Pacific, Station 250, surface. + + + +Subgenus 2. _Plegmosphaerella_, Haeckel. + +_Definition._--Inside of the spongy shell-wall closed by a smooth +lattice-plate, outside rough, spongy, with prominent thorns. + + +4. _Plegmosphaera entodictyon_, n. sp. + +Radius of the spherical shell-cavity half as great as the thickness of the +spongy wall. Inside of the wall closed by a smooth lattice-plate, outside +rough, spongy. + +_Dimensions._--Diameter of the shell 0.24, of its cavity 0.08. + +_Habitat._--South Pacific, Station 300, surface. + + +{89}5. _Plegmosphaera leptodictyon_, n. sp. + +Radius of the spongy shell-cavity six times as great as the thickness of +the spongy wall. Inside of the wall closed by a smooth lattice-plate, +outside rough spongy. + +_Dimensions._--Diameter of the shell 0.44, of its cavity 0.36. + +_Habitat._--Central Pacific, Station 266, surface. + + + +Subgenus 3. _Plegmosphaeromma_, Haeckel. + +_Definition._--Inside of the spongy shell-wall rough spongy, without +lattice-plate, outside closed by a smooth lattice-plate. + + +6. _Plegmosphaera exodictyon_, n. sp. (Pl. 18, fig. 8). + +Radius of the spongy shell-cavity only one-fourth as great as the thickness +of the spongy shell-wall. Outside of the wall closed by a smooth +lattice-plate, inside rough, spongy. + +_Dimensions._--Diameter of the shell 0.4, of its cavity 0.08. + +_Habitat._--South Atlantic, Station 325, surface. + + + +Subgenus 4. _Plegmosphaerusa_, Haeckel. + +_Definition._--Inside and outside of the spongy shell-wall rough, with +spongy or spiny surface, without lattice-plate. + + +7. _Plegmosphaera leptoplegma_, n. sp. + +Radius of the spherical shell-cavity half as great as the thickness of the +loose spongy shell-wall. Inside and outside of the wall rough spongy, not +closed by a lattice-plate. Meshes ten to twenty times as broad as the bars. + +_Dimensions._--Diameter of the shell 0.3, of its cavity 0.088. + +_Habitat._--North Atlantic, Station 253, surface. + + +8. _Plegmosphaera pachyplegma_, n. sp. + +Radius of the spherical shell-cavity about equal to the thickness of the +dark and dense spongy shell-wall. Inside and outside of the wall rough +spongy, not closed by a lattice-plate. Meshes three to five times as broad +as the bars. + +_Dimensions._--Diameter of the shell 0.2, of its cavity 0.1. + +_Habitat._--Central Pacific, Station 270, surface. + + + +Genus 27. _Spongoplegma_,[43] Haeckel, 1881, Prodromus, p. 455. + +_Definition._--#Liosphaerida# forming a sphere of spongy framework, which +encloses in the centre one single latticed medullary shell. + +{90}The genus _Spongoplegma_ may be regarded as a _Carposphaera_, in which +the simple latticed cortical shell is represented by an irregular spongy +framework, immediately enclosing the simple latticed medullary shell. + + +1. _Spongoplegma antarcticum_, n. sp. + +Cortical shell with loose spongy framework and rough surface, four to six +times as broad as the enclosed simple medullary shell. Pores of the latter +regular circular, twice as broad as the bars. From its surface arise +numerous (forty to fifty or more) short radial beams, which become forked +and compose, by communication of lateral branches, the spongy cortical +shell. + +_Dimensions._--Diameter of the spongy cortical shell 0.2 to 0.3 of the +latticed medullary shell 0.05 to 0.06. + +_Habitat._--Antarctic Ocean, in large number, together with _Cromyosphaera +antarctica_; in the Diatom ooze of Station 157 (depth 1950 fathoms). + + + +Genus 28. _Spongodictyon_,[44] Haeckel, 1862, Monogr. d. Radiol., p. 459. + +_Definition._--#Liosphaerida# forming a sphere of spongy framework, which +encloses in the centre a double latticed concentric medullary shell. + +The genus _Spongodictyon_ can be regarded as a _Thecosphaera_, in which the +simple latticed cortical shell is represented by an irregular spongy +framework, which immediately encloses the double latticed medullary shell. +Sometimes this latter appears triple, the inner surface of the spongy +cortical shell forming a smooth spherical lattice-plate, separated by an +interval from the double medullary shell. + + + +Subgenus 1. _Dictyoplegma_, Haeckel, 1862, Monogr. d. Radiol, p. 458. + +_Definition._--Spongy cortical shell enveloping immediately the double +medullary shell. + + +1. _Spongodictyon spongiosum_, Haeckel. + + _Dictyosoma spongiosum_, J. Mueller, 1858, Abhandl. d. k. Akad. d. Wiss. + Berlin, p. 31, Taf. ii. figs. 9-11. + + _Dictyoplegma spongiosum_, Haeckel, 1862, Monogr. d. Radiol., p. 458. + +Spongy framework of the cortical shell loose, with large, polygonal +roundish meshes, on an average as large as the double medullary shell, +which is immediately enveloped by it. Both concentric medullary shells with +subregular roundish pores, twice as broad as the bars. + +_Dimensions._--Diameter of the cortical shell 0.2 to 0.3 or more; of the +outer medullary shell 0.03, inner 0.01. + +_Habitat._--Mediterranean (French south coast, surface), J. Mueller. + + +{91}2. _Spongodictyon cavernosum_, n. sp. + +Spongy framework of the cortical shell rather compact in the inner part, +which immediately envelops the double medullary shell; very loose, with +large caverns in the outer part, caverns of the surface larger than the +medullary shell. Both medullary shells with regular circular pores, three +times as broad as the bars. + +_Dimensions._--Diameter of the cortical shell 0.3 to 0.4, outer medullary +shell 0.1, inner 0.03. + +_Habitat._--Tropical Atlantic, Station 338, surface. + + + +Subgenus 2. _Spongodictyoma_, Haeckel. + +_Definition._--Spongy cortical shell on the inner surface with a smooth +lattice-plate (or third medullary shell), which is connected by radial +beams with the inner double medullary shell. + + +3. _Spongodictyon trigonizon_, Haeckel. + + _Spongodictyon trigonizon_, Haeckel, 1862, Monogr. d. Radiol., p. 459, + Taf. xxvi. figs. 4-6. + + _Dictyosoma trigonizon_, Haeckel, 1860, Monatsber. d. k. preuss. Akad. d. + Wiss. Berlin, p. 841. + +Spongy framework of the cortical shell very loose, with very large, for the +most part triangular meshes, which are two to six times as large as the +enclosed double medullary shell. From the surface of the latter arise +numerous radial beams, which are connected by a spherical lattice-plate, +forming the smooth inner surface of the spongy sphere (or a third medullary +shell). The structure of the framework reminds one of the PHAEODARIUM +_Sagena_ (Pl. 108). Pores of both medullary shells regular circular, twice +as broad as the bars. + +_Dimensions._--Diameter of the cortical shell 0.5 to 1.15, outer medullary +0.05, inner 0.035. + +_Habitat._--Mediterranean, Messina, surface. + + +4. _Spongodictyon arcadophoron_, n. sp. + +Spongy framework of the cortical shell in the inner part very loose, in the +outer part more compact; outer meshes scarcely as large as the inner +medullary shell (or only half as large), inner meshes two to four times as +large. From the surface of the double medullary shell arise numerous radial +beams, which are forked at equal distances from the centre; the fork +branches are curved and united together by dichotomous branches, like +elegant arcades; and these arcades form together the large polygonal meshes +on the inside of the cortical shell (or a third medullary shell). Both +medullary shells with regular circular pores, of the same breadth as the +bars. + +_Dimensions._--Diameter of the cortical shell 0.2, outer medullary shell +0.04, inner 0.02. + +_Habitat._--Tropical Atlantic, Station 349, surface. + + + +{92}Family VI. #COLLOSPHAERIDA#, J. Mueller[45] (Pls. 5-8). + +_Definition._--#Sphaeroidea# living associated in colonies, united by an +alveolar jelly-body, and connected by the network of anastomosing +pseudopodia. + +The family #Collosphaerida# comprises all polyzous or social #Sphaeroidea#, +and constitutes the only polyzoic group among the SPHAERELLARIA. This group +was first constituted by J. Mueller as "_Radiolaria polyzoa_ with +shells."[46] Formerly following his authority, in my Monograph I had +separated them from the other #Sphaeroidea# and united them with the social +Collodaria (Sphaerozoida).[47] Also R. Hertwig in his Organismus der +Radiolarien[48] united them with his Sphaerozoea. In my Prodromus[49] I had +retained this isolated position. But a further careful study has convinced +me that this isolation is not truly natural, and that the Collosphaerida +are only "social Ethmosphaerida" which have arisen from this solitary +subfamily by adaptation to colonial life. There are some forms of +Collosphaerida which are nearly identical with some forms of +Ethmosphaerida, only differing from the latter by their association in +colonies; and in some forms of both groups it is quite impossible to decide +whether the isolated shells appertain to one or to the other family. + +The isolated shell of the Collosphaerida is almost constantly (with few +exceptions) a simple extracapsular lattice-shell, as in the Monosphaerida; +only the small group of Clathrosphaerida (with the genera _Clathrosphaera_ +and _Xanthiosphaera_) exhibit an exception, the simple lattice-shell being +overgrown by an external mantle or veil of very thin, cobweb-like, +irregular lattice-work (Pl. 8, figs. 6-11). Therefore these +Clathrosphaerida bear to the Acrosphaerida (or the common simple +Collosphaerida) a relation similar to that which _Liosphaera_ (p. 76) bears +to _Cenosphaera_; both shells are extracapsular "cortical shells" at a very +short distance apart. In the Collosphaerida true concentric medullary +shells never occur; the central capsule always lies quite freely in the +simple or double cortical shell, separated from it by a jelly-veil. + +Although a well marked difference in the simple lattice-shell of the social +Collosphaerida and the solitary Ethmosphaerida does not exist, nevertheless +in most cases the two shells can be distinguished by a practiced observer. +The simple fenestrated shells of the monozoic Ethmosphaerida are commonly +quite regular spheres in a mathematical sense, or regular "endospherical +polyhedra"; whereas in the Collosphaerida they are commonly more or less +irregular, often to an extraordinary degree (Pls. 5-8). Some species of +Collosphaerida, however, also possess quite regular spherical shells. +Another difference is often shown in the lattice-work of the shells, which +in the Collosphaerida is nearly always very irregular, and exhibits a +peculiar tendency to the {93}production of radial, conical, or cylindrical +tubules. These occur as well on the inside as on the outside of the shell, +and the tubules are now more conical, now more cylindrical; their wall +either solid or pierced by pores (Pls. 5-8). The tubules are commonly very +irregular in form, size, and disposition; distinguished, however, by a +number of hereditary peculiarities, which are sufficient for the +distinction of genera. Similar tubules occur also in some genera of +solitary Ethmosphaerida (_Coscinomma_, _Ethmosphaera_, _Conosphaera_, &c., +Pl. 12); but the tubules are here much more regular and not so highly +developed. + +Besides the tubules of the fenestrated shells, in some genera of +Collosphaerida the surface is armed with irregular thorns, rarely with more +regular radial spines. But these spines obtain constantly the character of +accessory by-spines, and remain short and thin. In this family typical +radial spines never occur in a regular and characteristic disposition, +corresponding to dimensive axes, as is the case in nearly all solitary +#Sphaeroidea#, only excepting the Liosphaerida. Commonly these spines or +thorns serve as protective arms for the shell-meshes, surrounding them +often in the form of coronels. Often the lattice-plate of the irregular +roundish shell is tubercular, elevated into irregular protuberances, +bearing on the top a short spine or thorn (Pl. 8). + +The _Central Capsule_ of the Collosphaerida is always a regular sphere, as +in all other #Sphaeroidea#; it is constantly placed within the +lattice-shell, and commonly much smaller than it, separated from it by a +thick jelly-veil. A remarkable difference from the solitary #Sphaeroidea# +is shown in the early division of the nucleus. Commonly the central capsule +of the Collosphaerida contains in its centre a large oil-globule, +surrounded by very numerous small nuclei. R. Hertwig estimated this +difference as so important, that he separated the social "Sphaerozoea" and +the solitary "Peripylea" as two different orders. As already shown above +(p. 7, 24), we cannot support this separation, and are now convinced that +this difference in the development of the spores--just as in the +#Collodaria#--is the consequence of an adaptation to social life. + +The common jelly-body, in which the numerous central capsules and their +enveloping shells are united, exhibits in the Collosphaerida quite the same +characters as in the other social Radiolaria, the Collozoida and +Sphaerozoida. The jelly-body is very voluminous, commonly spherical, often +cylindrical, of considerable size; constantly containing numerous large +alveoles. Often each shell is enclosed in a separate alveole with rather +solid wall (Pl. 6, fig. 2). Sometimes in the dead colonies all shells are +united in the central part of the jelly-body, whilst its peripheral part is +composed of a stratum of large alveoles (Pl. 8, fig. 11); at other times no +alveoles are visible (Pl. 7, fig. 11). In many living colonies I found a +very large spherical alveole with thick wall in the centre of the spherical +colony, surrounded by many strata of delicate thin-walled alveoles (Pl. 5, +fig. 1). In this case often the inner younger capsules were naked, +{94}without shells, the outer only surrounded by shells. Already in my +Monograph I had described the same peculiar formation.[50] + +_Synopsis of the Genera of Collosphaerida._ + + ------------------------------------------------------------------------- + I. Subfamily Acrosphaerida. (Lattice-shell simple, without an external + mantle of network.) + ------------------------------------------------------------------------- + {Inside {Inside smooth, 29. _Collosphaera_. + Outside of { without { + the shell { tubuli. {Inside spiny, 30. _Tribonosphaera_. + smooth, { + without { {Tubuli + spines or {Inside with { imperforated, 31. _Pharyngosphaera_. + tubuli. { centripetal { + { tubuli. {Tubuli + { { fenestrated, 32. _Buccinosphaera_. + + {Spines + { irregularly + { scattered on + { the surface, 33. _Acrosphaera_. + { + Outside of the shell armed {Each larger + with solid spines, but { pore with one + with hollow tubuli. { single spine, 34. _Odontosphaera_. + { + {Each larger + { pore with + { a coronal of + { spines, 35. _Choenicosphaera_. + + {Mouth of the + { tubuli + { truncated, + { smooth, 36. _Siphonosphaera_. + { + Outside of {Tubuli {Mouth with + the shell { simple, not { one single + with { branched. { large tooth, 37. _Mazosphaera_. + irregular { { + radial { {Mouth with a + tubuli, { { coronal of + the wall of { { teeth, 38. _Trypanosphaera_. + which is { + solid, not {Tubuli irregularly branched, + fenestrated.{ each with two to four or + { more openings, 39. _Caminosphaera_. + + {Mouth of the + { tubuli + { truncated, + { smooth, 40. _Solenosphaera_. + Outside of the shell with { + irregular radial tubuli, {Mouth with one + open on both ends, { single large + with fenestrated wall. { tooth, 41. _Otosphaera_. + { + {Mouth with a + { coronal of + { teeth, 42. _Coronosphaera_. + ------------------------------------------------------------------------- + II. Subfamily Clathrosphaerida. (Lattice-shell double, with an external + mantle of network.) + ------------------------------------------------------------------------- + Surface of the outer shell smooth, 43. _Clathrosphaera_. + + Surface of the outer shell thorny, 44. _Xanthiosphaera_. + + + +Subfamily ACROSPHAERIDA, Haeckel, 1881, Prodromus, p. 471. + +_Definition._--#Collosphaerida# with one simple lattice-shell around every +central capsule of the coenobium. + + + +{95}Genus 29. _Collosphaera_,[51] J. Mueller, 1855. + +_Definition._--#Collosphaerida# with simple shells, smooth on the inside +and on the outside, without any spines or tubuli. + +The genus _Collosphaera_ is the most simple form of all Collosphaerida, and +must be regarded as the common ancestral form of this family. As the +lattice-shell is quite a simple sphere, without any spines, tubules, or +other peculiar productions, it agrees perfectly with _Cenosphaera_, and +represents the social or polyzoid aggregate of this solitary or monozoid +genus. Therefore a certain distinction between the isolated shells of the +two genera is often very difficult or even impossible; but commonly this +distinction is possible owing to the circumstance, that in the majority of +the _Collosphaerae_ the shell is more or less irregular roundish or +polyhedral, not quite spherical, as in _Cenosphaera_. _Dermatosphaera_, +Ehrenberg, is a _Collosphaera_ with small pores (compare L. N. 16, p. 533). + + + +Subgenus 1. _Eucollosphaera_, Haeckel. + +_Definition._--Shell a regular or subregular sphere. + + +1. _Collosphaera primordialis_, n. sp. + +Shell a regular sphere, with very delicate and regular network of hexagonal +meshes. Six to eight meshes in the half meridian of the shell. Diameter of +the meshes ten to fifteen times as broad as the thin bars between them. Can +be regarded as social form of _Cenosphaera primordialis_. + +_Dimensions._--Diameter of the shell 0.1 to 0.12, of the pores 0.008. + +_Habitat._--Central Pacific, Stations 271 to 274, surface. + + +2. _Collosphaera regularis_, n. sp. + +Shell a regular sphere, with a perfectly regular network of circular +meshes, all of the same size. Ten to twelve meshes in the half meridian of +the shell. Diameter of the meshes the same as that of the bars between +them. + +_Dimensions._--Diameter of the shell 0.1 to 0.12, of the pores 0.005 to +0.006. + +_Habitat._--Indian Ocean, Madagascar, surface, Rabbe. + + +3. _Collosphaera globularis_, n. sp. + +Shell a regular sphere, with subregular network of circular meshes of +different sizes; few large pores between many smaller pores. Ten to twenty +meshes in the half meridian of the shell. Diameter of the meshes from half +to twice as broad as that of the bars. + +{96}_Dimensions._--Diameter of the shell 0.1 to 0.12, of the pores 0.002 to +0.008, breadth of the bars 0.004 to 0.008. + +_Habitat._--Tropical and subtropical zone of both hemispheres, widely +distributed; Canaries, Azores, Cape Verde Islands, Guinea Coast, Brazil +Coast, Indian Ocean, Madagascar, Ceylon, surface. + + + +Subgenus 2. _Dyscollosphaera_, Haeckel. + +_Definition._--Shell not a regular sphere, but irregular roundish, in all +degrees of variation between subspherical and polyhedral or quite irregular +forms. + + +4. _Collosphaera huxleyi_, J. Mueller. + + _Collosphaera huxleyi_, J. Mueller, 1855, Abhandl. d. k. Akad. d. Wiss. + Berlin, pp. 55-59, Taf. viii. figs. 6-9. + + _Collosphaera huxleyi_, Haeckel, 1862, Monogr. d. Radiol., p. 534, Taf. + xxxiv. + + _Collosphaera huxleyi_, Cienkowski, 1871, Archiv f. mikrosk. Anat., Bd. + vii. p. 374, Taf. xxix. figs. 1-6. + + _Collosphaera ligurina_, J. Mueller, 1856, Monatsber. d. k. Akad. d. + Wiss. Berlin, p. 481. + + _Thalassicolla punctata_, var., Huxley, 1851, Ann. and Mag. Nat. Hist., + ser. 2, vol. viii. p. 434, pl. xvi. fig. 6. + +Shell subspherical, somewhat irregular, sometimes with more or less +superficial impressions, with irregular network of roundish meshes. Eight +to sixteen meshes in the half meridian of the shell, one to three times as +broad as their bars. Very variable, with direct transition-forms to other +species of this genus, especially to _Collosphaera globularis_, +_Collosphaera tuberosa_, _Collosphaera pyriformis_, and _Collosphaera +polyedra_. + +_Dimensions._--Diameter of the shell 0.1 to 0.16, of the pores 0.004 to +0.012, of the bridges 0.003 to 0.006. + +_Habitat._--Cosmopolitan; common in the greater part of the warmer seas, +surface. + + +5. _Collosphaera polygona_, n. sp. (Pl. 5, fig. 13). + + _Collosphaera huxleyi_ var., Haeckel, 1862, Monogr. d. Radiol., Taf. + xxxiv. fig. 5. + +Shell irregular polygonal, with very delicate, irregular network of +polygonal meshes, four to twelve times as broad as the bars. Ten to twenty +pores on the half meridian of the shell. + +_Dimensions._--Diameter of the shell 0.1 to 0.2, of the pores 0.012 to +0.004, of the bars 0.001 to 0.002. + +_Habitat._--Mediterranean, Atlantic, surface; Stations 348 to 354. + + +6. _Collosphaera pyriformis_, Haeckel, n. sp. + +Shell irregular, rounded, ovate or pear-shaped, with irregular network of +rounded or nearly polygonal meshes. Ten to twenty meshes in the half +meridian of the shell, one to three times as broad as the bars. Commonly +one large opening (two to three times as broad as the largest {97}meshes) +on the thinner end of the ovate shell (corresponding to the insertion of a +pear-stalk); sometimes two or three such large openings. + +_Dimensions._--Diameter of the shell 0.1 to 0.15, of the pores 0.008 to +0.016, of the bridges 0.004 to 0.008. + +_Habitat._--Tropical zone--Cape Verde Islands, Ceylon; Central Pacific, +Stations 266 to 272, 348 to 352, &c. + + +7. _Collosphaera polyedra_, n. sp. + + _Trisolenia zanguebarica_, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. + Berlin, p. 301, Taf. x. fig. 11. + +Shell irregular, polyhedral, with even or somewhat vaulted sides, and +obtuse ridges between them. Network more or less irregular, with small +rounded meshes, quite as broad or twice as broad as their bars. Besides +these small pores constantly some large round openings (commonly three to +six), situated on the corners of the polyhedral shell, four to six times as +large as the pores. Often an acute tooth on the edge of each large opening. +Transition-form between _Collosphaera_ and _Solenosphaera_ or +_Odontosphaera_. + +_Dimensions._--Diameter of the shell 0.1 to 0.15, of the pores 0.004 to +0.008, of their bridges 0.004, of the large openings 0.24 to 0.032. + +_Habitat._--Tropical zone of the Pacific and the Indian Ocean; Stations 266 +to 272, surface. + + +8. _Collosphaera tuberosa_, n. sp. + + _Collosphaera huxleyi_, var., Haeckel, 1862, Monogr. d. Radiol., Taf. + xxxiv. figs. 3, 9. + +Shell very irregular, between subspherical and polyhedral in form, but +always with irregular impressions, boils or bosses, and between these +different rounded prominent tubercles and ridges. Network irregular, +strong, with rounded, subcircular or nearly polygonal meshes. Ten to thirty +pores in the half meridian of the shell. Diameter of the meshes half to +four times as broad as that of the thick bars. + +_Dimensions._--Diameter of the shell very variable in the same coenobium, +0.05 to 0.2, of the pores 0.002 to 0.008, breadth of the bridges 0.004 to +0.006. + +_Habitat._--Cosmopolitan, common in all warmer seas, surface. + + +9. _Collosphaera irregularis_, n. sp. + + _Collosphaera huxleyi_, var., Haeckel, 1862, Monogr. d. Radiol., Taf. + xxxiv. fig. 8. + +Shell quite irregular, knotty or bulbous, with irregular impressions, and +prominent knobs or bulbs between them. Network thin, fragile, quite +irregular, with polygonal meshes of most unequal size and form. Five to +twenty pores in the half meridian of the shell. Diameter of the meshes two +to ten times as broad as that of the thin bars. + +_Dimensions._--Diameter of the shell very variable in the same coenobium, +0.04 to 0.24, of the pores 0.005 to 0.05, of the bridges 0.002 to 0.004. + +_Habitat._--Mediterranean, Atlantic, not common; Stations 348, 352, &c., +surface. + + + +{98}Genus 30. _Tribonosphaera_,[52] Haeckel, 1881, Prodromus, p. 471. + +_Definition._--#Collosphaerida# with simple shells, on the inside with +radial centripetal beams. + +The genus _Tribonosphaera_ differs from _Collosphaera_ by a very peculiar +and rare character, the development of centripetal radial sticks on the +internal face of the shell; these beams are not united in the centrum, but +finish freely in a certain distance from it. + + +1. _Tribonosphaera centripetalis_, n. sp. (Pl. 5, fig. 12). + +Shell roundish or subspherical, with numerous small circular or roundish +pores, about twice as broad as the bars. Twenty to thirty pores on the half +meridian of the shell. Outside of the shell smooth, inside a variable +number (ten to twenty) of thin, radial, centripetal sticks or spines, +one-third or one-half as long as the radius of the shell. (In the central +capsule many very large crystals, resting after the destruction of the +capsule.) + +_Dimensions._--Diameter of the shell 0.1 to 0.12, of the pores 0.003 to +0.005, of the bridges 0.001 to 0.002; length of the inner centripetal +sticks 0.02 to 0.03. + +_Habitat._--Central Pacific, Station 271, surface. + + + +Genus 31. _Pharyngosphaera_,[53] n. gen. + +_Definition._--#Collosphaerida# with simple shells, having on the inside +radial centripetal tubes, the walls of which are solid. + +The genus _Pharyngosphaera_ differs from _Collosphaera_ by the development +of radial tubules on the inside of the shell, which are directed +centripetally towards its centre. The wall of the tubule is solid, not +latticed as in the following genus. + + +1. _Pharyngosphaera stomodaea_, n. sp. (Pl. 5, fig. 10). + +Shell irregular polyhedral, with ten to fifteen polygonal faces and rounded +edges. Pores very small, circular, irregularly scattered, smaller than the +bars. Twelve to fifteen pores on the half meridian of the shell. On the +inside of every shell-face one short, nearly cylindrical, centripetal +tubule, twice as long as broad, and about one-third as long as the shell +radius. Outer umbilical mouth of the tubules somewhat wider than the inner +truncated mouth. + +_Dimensions._--Diameter of the shell 0.11 to 0.12, of the pores 0.003 to +0.005, of the bars 0.01 to 0.02; length of the inner tubuli 0.02, breadth +of them 0.01. + +_Habitat._--South Pacific, Station 288, depth 2600 fathoms. + + + +{99}Genus 32. _Buccinosphaera_,[54] n. gen. + +_Definition._--#Collosphaerida# with simple shells, having on the inside +radial centripetal tubes, the walls of which are fenestrated. + +The genus _Buccinosphaera_ exhibits, on the inner surface of the shell, +radial centripetal tubules similar to those of the foregoing +_Pharyngosphaera_; but the walls of these tubes are here latticed, not +solid; they represent therefore true invaginations of the whole shell-wall. + + +1. _Buccinosphaera invaginata_, n. sp. (Pl. 5, fig. 11). + +Shell irregular roundish or nearly polyhedral, with a variable number of +umbilical depressions, which are prolonged on the inside into cylindrical +or somewhat conical, centripetal, fenestrated tubes, about one-third as +long as the shell radius. Inner mouth of the tubes narrower, scarcely half +as broad as the outer mouth, about equal to one-fourth the shell radius, +truncated. Pores of the tubes and of the shell small, roundish, irregular +in size and distribution, about as broad as the bars. Twenty-five to thirty +pores in the half meridian of the shell. In all observed specimens the +spherical central capsule (half as broad as the shell) contained a large +number of crystals. + +_Dimensions._--Diameter of the shell 0.1 to 0.12, of the pores 0.001 to +0.003, of the bars 0.002 to 0.003; length of the tubuli 0.02; outer mouth +0.026, inner mouth 0.013; crystals in the central capsule 0.002 to 0.004, +sometimes 0.008. + +_Habitat._--Philippine Islands (Samboangan), Station 213, surface. + + +2. _Buccinosphaera tubaria_, n. sp. + +Shell irregular polyhedral with rounded edges, with a variable number of +umbilical depressions, which are prolonged on the inside into large, nearly +cylindrical, centripetal, fenestrated tubes, half as long as the shell +radius. In the middle the tubes are somewhat constricted and narrower. +Inner mouth of the tubes dilated, nearly as broad as the outer mouth, about +equal to one-half the shell-radius, truncated. Pores of the tubes and of +the shell large, roundish polygonal, irregular in size and distribution, +three to four times as broad as the bars. Fifteen to twenty pores in the +half meridian of the shell. + +_Dimensions._--Diameter of the shell 0.12 to 0.14, of the pores 0.008 to +0.012, of the bars 0.002 to 0.004; length of the tubuli 0.03; outer mouth +0.04, inner mouth 0.03. + +_Habitat._--North coast of New Guinea, Station 217, surface. + + + +Genus 33. _Acrosphaera_,[55] Haeckel, 1881, Prodromus, p. 471. + +_Definition._--#Collosphaerida# with simple shells, the outer surface of +which is covered with radial, irregularly scattered spines. + +{100}The genus _Acrosphaera_ differs from its ancestral genus +_Collosphaera_ by the development of spines on the outer surface of the +shell. These are either short, straight, radial spines, or oblique and +often curved; their base is often inflated; they are irregularly scattered +on the whole surface between the pores. + + +1. _Acrosphaera erinacea_, n. sp. + +Shell a regular sphere, everywhere covered with small, very numerous, +straight radial spines, regularly scattered between the pores. In the half +meridian of the shell ten to twelve circular pores, all of the same form +and size, double as broad as the bars. Spines bristle-shaped, very thin, +solid, about as long as the diameter of the pores. + +_Dimensions._--Diameter of the shell 0.1 to 0.12, of the pores 0.008 to +0.012; length of the spines 0.01. + +_Habitat._--Tropical zone of the Atlantic, coast of Brazil, Rabbe, surface. + + +2. _Acrosphaera echinoides_, n. sp. (Pl 8, fig. 1). + +Shell a regular sphere, covered with numerous, straight, radial spines, +irregularly scattered over the whole surface. In the half meridian of the +shell twenty to thirty irregular roundish pores of variable size, one to +four times as broad as the bars. Spines conical, strong, quite radial, at +the top of small conical elevations, which are perforated by from three to +six pores. + +_Dimensions._--Diameter of the shell 0.12 to 0.15, of the pores 0.002 to +0.008; length of the spines 0.015, of their basal zones 0.01. + +_Habitat._--South-east corner of the Pacific, Valparaiso, Station 298, +surface. + + +3. _Acrosphaera setosa_, Haeckel. + + _Polysolenia setosa_, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. + Berlin, p. 299, Taf. viii. fig. 10. + +Shell a regular sphere, covered with numerous bristle-shaped radial spines, +irregularly scattered between the pores. In the half meridian of the shell +two to four very large circular pores (equal to one-third the radius), and +between them numerous very small, point-like pores. + +_Dimensions._--Diameter of the shell 0.05 to 0.08, of the large pores 0.01, +of the small 0.001; length of the spines 0.01 to 0.02. + +_Habitat._--West Tropical Pacific, Philippine Sea, Station 206, depth 2100 +fathoms. + + +4. _Acrosphaera spinosa_, Haeckel. + + _Collosphaera spinosa_, Haeckel, 1862, Monogr. d. Radiol., p. 536, Taf. + xxxiv. figs. 12, 13. + + _Collosphaera spinosa_, Cienkowsky, 1871, Archiv f. mikrosk. Anat., vii. + p. 374, Taf. xxix. figs. 7-17. + +Shell a regular or subregular sphere, covered with numerous, obliquely +standing spines, irregularly scattered over the surface. In the half +meridian of the shell fifteen to twenty irregular {101}roundish pores of +very different form and size, one to four times as broad as their bars. +Spines conical, irregularly diverging and curved, their hollow base +perforated by several pores, not longer than the diameter of the largest +pores. + +_Dimensions._--Diameter of the shell 0.1 to 0.2, of the pores 0.001 to +0.04; length of the spines 0.01 to 0.02. + +_Habitat._--Mediterranean, Messina; Canary Islands, Haeckel. + + +5. _Acrosphaera collina_, n. sp. (Pl. 8, fig. 2). + +Shell quite irregular, polyhedrical, hilly, with a variable number (eight +to sixteen) of large conical hill-like prominences; every cone or hill +about as high as broad, perforated by the same pores as the shell, on its +top bearing a larger irregular roundish pore, and on its edge one single +bristle-like spine, not larger than the diameter of this pore, obliquely +inserted. In the half meridian of the shell twenty to thirty irregular +roundish pores of very different size, one to six times as broad as the +bars. A very characteristic species, closely resembling the following +_Odontosphaera_. + +_Dimensions._--Diameter of the shell 0.15 to 0.25, of the pores 0.005 to +0.02; length of the spines 0.01 to 0.02, height of the hills from which +they rise 0.03 to 0.04. + +_Habitat._--North coast of New Guinea, Station 218, surface. + + +6. _Acrosphaera inflata_, n. sp. (Pl. 5, fig. 7). + + _Mazosphaera inflata_, Haeckel, 1879, Atlas, _loc. cit._ + +Shell more or less irregular, polyhedral, hilly, with a variable number +(six to twelve) of large pyramidal, hill-like prominences; every hill about +as high as broad, on the top a strong conical, radial, or obliquely +inserted spine, inflated, with three to six very large polygonal meshes, +much larger than the other pores between the hills, which are also +polygonal, two to six times as broad as the bars. Ten to fifteen pores on +the half meridian. + +_Dimensions._--Diameter of the shell 0.1 to 0.14, of the largest pores +0.05, of the smallest 0.005; length of the spines 0.02 to 0.03. + +_Habitat._--North Atlantic, Station 64, surface. + + + +Genus 34. _Odontosphaera_,[56] n. gen. + +_Definition._--#Collosphaerida# with simple shells, the outside of which +bears single scattered spines, one single spine on the margin of each +larger pore. + +The genus _Odontosphaera_ is distinguished from the foregoing _Acrosphaera_ +by the peculiar disposition of the spines, which are not scattered on the +outside of the shell between the pores, but so disposed that each larger +pore is protected by one single spine, obliquely placed over it. + + +{102}1. _Odontosphaera monodon_, n. sp. (Pl. 5, fig. 5). + +Shell spherical or subspherical, with very small and numerous circular +pores, much smaller than the bars. Twelve to fifteen pores on the half +meridian of the shell. Between them a variable number of larger roundish +apertures (mostly twelve to sixteen) irregularly scattered, one-fourth to +one-fifth as broad as the shell radius. On the margin of every larger +aperture a single (rarely two or three) sharp conical tooth, about as long +as the diameter of the aperture, and obliquely laid over them. + +_Dimensions._--Diameter of the shell 0.1 to 0.13, of the pores 0.001 to +0.003, of the bars 0.01 to 0.02, of the larger apertures 0.01 to 0.02. + +_Habitat._--Sunda Archipelago, Station 192, surface. + + +2. _Odontosphaera cyrtodon_, n. sp. (Pl. 5, fig. 6). + +Shell spherical or subspherical, with numerous roundish pores of very +irregular size and distribution, mostly larger than the bars. Ten to twelve +pores on the half meridian of the shell. Between them a variable number +(mostly six to nine) of large roundish pores, about half as broad as the +shell radius, armed on one side of the margin with one single large tooth, +about as long as the diameter of the aperture, hook-like, curved, and +obliquely laid over them. + +_Dimensions._--Diameter of the shell 0.12 to 0.14, of the pores 0.01 to +0.02, of the bars 0.003 to 0.006, of the larger apertures 0.03 to 0.04. + +_Habitat._--Indian Ocean, near the Cocos Islands, Rabbe, surface. + + + +Genus 35. _Choenicosphaera_,[57] n. gen. + +_Definition._--#Collosphaerida# with simple shells, armed on the outside +with radial spines, forming elegant coronals around the larger pores. + +The genus _Choenicosphaera_ is characterised by the peculiar disposition of +its radial spines, which form protective coronals around the larger pores, +or even around all pores of the shell. + + + +Subgenus 1. _Choenicosphaerula_. + +_Definition._--A coronal of spines around every pore of the shell. + + +1. _Choenicosphaera murrayana_, n. sp. (Pl. 8, fig. 4). + +Shell spherical, with large circular or roundish pores of unequal size, two +to four times as broad as the bars. Ten to twelve pores in the half +meridian of the shell. Margin of every pore {103}with a coronal of six to +nine short and acute spines, not longer than the half diameter of the pore. +No spines between the pores. + +_Dimensions._--Diameter of the shell 0.16 to 0.2, of the pores 0.02 to +0.03; length of the spines 0.008 to 0.012. + +_Habitat._--Faeroee Channel (Gulf Stream), common. Expedition of H.M.S. +"Triton," John Murray. + + +2. _Choenicosphaera flosculenta_, n. sp. + +Shell spherical, with large circular or roundish pores of different size, +three to six times as broad as the bars. Six to eight pores in the half +meridian of the shell. Margin of every pore somewhat prominent, with a +coronal of ten to twenty parallel acute spines of different length, the +largest somewhat longer than the diameter of the pore. No spines between +the pores. + +_Dimensions._--Diameter of the shell 0.12 to 0.15, of the pores 0.02 to +0.04; length of the spines 0.02 to 0.05. + +_Habitat._--Central Pacific, Station 272, depth 2600 fathoms. + + + +Subgenus 2. _Choenicosphaerium_. + +_Definition._--A coronal of spines only around the larger pores, not around +the smaller. + + +3. _Choenicosphaera nassiterna_, n. sp. (Pl. 8, fig. 3). + +Shell spherical, with circular or roundish pores of very different size. +The smaller pores very numerous, without coronal of spines, roundish, about +as broad as the bridges. Twenty to thirty pores in the half meridian of the +shell. Between them, irregularly scattered, a small number (eight to +twelve) of very large circular pores, one-third to one-half as broad as the +radius of the shell, armed with a coronal of six to nine parallel, +straight, acute spines, about half as long as the radius of the shell. + +_Dimensions._--Diameter of the shell 0.1 to 0.13, of the smaller pores +0.002 to 0.004, of the larger armed pores 0.02 to 0.03; length of the +spines 0.03 to 0.04. + +_Habitat._--Philippine Islands, Mindanao, Station 213, depth 2050 fathoms. + + +4. _Choenicosphaera flammabunda_, n. sp. (Pl. 8, fig. 5). + +Shell spherical, with circular or roundish pores of very different size. +The smaller pores very numerous and unequal, very irregularly scattered, +hardly one-fourth to one-half as broad as the bridges between them. Twelve +to twenty-four pores in the half meridian of the shell. Between them, +irregularly scattered, a variable number (ten to twenty) of very large +circular pores, about one-fourth as broad as the radius of the shell. The +margin of these large pores is armed with a very irregular coronal of four +to twelve unequal, curved acute spines, partly simple, partly branched like +{104}a deer-horn, one-fourth to one-half as long as the radius of the +shell. Some other small spines irregularly scattered over the shell. + +_Dimensions._--Diameter of the shell 0.12 to 0.16, of the smaller pores +0.001 to 0.004, of the larger armed pores 0.016 to 0.024; length of the +spines 0.02 to 0.04. + +_Habitat._--Central area of the Tropical Pacific, Stations 266 to 272, +depth 2425 to 2925 fathoms. + + + +Genus 36. _Siphonosphaera_,[58] J. Mueller, 1858, Abhandl. d. k. Akad. d. +Wiss. Berlin, p. 59. + +_Definition._--#Collosphaerida# with simple shells, the pores of which are +prolonged into external simple radial tubuli with solid wall; outer mouth +of the tubuli truncated, smooth. + +The genus _Siphonosphaera_ is, next to _Collosphaera_, the most common of +all Collosphaerida, and rich in different species; all agreeing in the +tubular prolongation of the pores, and corresponding therefore to +_Ethmosphaera_ among the simple Liosphaerida. + + + +Subgenus 1. _Holosiphonia_, Haeckel. + +_Definition._--All the pores or apertures of the shell prolonged into +tubules. + + +1. _Siphonosphaera pansiphonia_, n. sp. + +Shell a regular sphere, everywhere occupied by short, regular cylindrical +tubes, all of the same size and form. Length of the tubules equal to their +breadth and to the intervals between them. Ten to twelve tubules in the +half meridian of the shell. This most regular species is nearly allied to +_Collosphaera regularis_, and may be derived from it by tubular +prolongation of all the regular pores. + +_Dimensions._--Diameter of the shell 0.1 to 0.12, length and breadth of the +tubules 0.005 to 0.006. + +_Habitat._--Indian Ocean, Sunda Strait, Rabbe, surface. + + +2. _Siphonosphaera marginata_, n. sp. + +Shell a regular or subregular sphere, occupied by numerous short +cylindrical tubules of different sizes. Six to eight tubules in the half +meridian of the shell. Diameter of the tubules about equal to their +distance apart, but two to four times as large as their length. + +_Dimensions._--Diameter of the shell 0.1 to 14; length of the tubules 0.004 +to 0.006, breadth of the tubules and the intervals 0.01 to 0.02. + +_Habitat._--Central Pacific, Station 268, depth 2900 fathoms. + + +{105}3. _Siphonosphaera tubulosa_, J. Mueller (Pl. 6, fig. 4). + + _Siphonosphaera tubulosa_, J. Mueller, 1858, Abhandl. d. k. Akad. d. + Wiss. Berlin, p. 59. + + _Siphonosphaera tubulosa_, Haeckel, 1862, Monogr. d. Radiol., p. 532. + + _Collosphaera tubulosa_, J. Mueller, 1858, Abhandl. d. k. Akad. d. Wiss. + Berlin, p. 59. + + _Thalassicolla punctata_, var., Huxley, 1851, Ann. and Mag. Nat. Hist., + ser. 2, vol. viii. p. 435, pl. xvi. fig. 5. + +Shell subspherical or roundish, somewhat irregular, occupied by a small +number (five to ten) of short cylindrical tubules, irregularly scattered at +great distances; intervals between the tubules very large, two to four +times as broad as the length of the tubules, which is equal to their +breadth and about one-fifth or one-sixth of the shell diameter. Only two or +three tubules in the half meridian of the shell. + +_Dimensions._--Diameter of the shell 0.12 to 0.15, length and breadth of +the tubules 0.02 to 0.03. + +_Habitat._--Equatorial zone of the Pacific, Stations 225, 265, 268, +surface. + + +4. _Siphonosphaera cyathina_, n. sp. (Pl. 6, fig. 10). + +Shell a regular sphere, everywhere occupied by short cup-like tubules of +somewhat different size. In the half meridian of the shell about ten to +twelve tubules, nearly cylindrical, but constricted in the middle. Inner +and outer aperture of the tubule of the same size; their diameter equal to +their length and distance. + +_Dimensions._--Diameter of the shell 0.1 to 0.12, length and breadth of the +tubules 0.005 to 0.01. + +_Habitat._--West coast of Tropical Africa, Stations 348 to 352, surface. + + +5. _Siphonosphaera patinaria_, n. sp. (Pl. 6, figs. 7, 8). + +Shell a regular or subregular sphere, occupied by numerous broad cup-like +tubules of very different sizes. In the half meridian of the shell about +six to eight tubules, very flat, circular or subcircular, much constricted +in the middle. Diameter of the inner aperture larger than that of the +middle stricture, smaller than that of the outer aperture of the tubule; +outer diameter two to four times as great as their length. + +_Dimensions._--Diameter of the shell 0.1 to 0.15, of the pores 0.01 to +0.04; length of the tubules 0.01, breadth 0.02 to 0.04. + +_Habitat._--Tropical Atlantic, Station 348, depth 2450 fathoms. + + +6. _Siphonosphaera infundibulum_, n. sp. + +Shell subspherical or irregular rounded, occupied by a small number (six to +twelve) of large funnel-like tubules of very different size, scattered +irregularly at great distances. Intervals between the tubules larger than +their length, which surpasses the radius of the shell. Outer opening of the +funnels three to four times as broad as the inner. + +_Dimensions._--Diameter of the shell 0.15; length of the tubules 0.05 to +0.09. + +_Habitat._--South Atlantic, Station 332, depth 2200 fathoms. + + +{106}7. _Siphonosphaera conifera_, n. sp. (Pl. 6, fig. 9). + +Shell subspherical, everywhere occupied by irregular conical tubules, the +length of which nearly reaches the shell radius. Inner aperture of the +cones two to three times as large as the outer. Four to five tubules in the +half meridian of the shell. Distances between the bases of the cones small +and irregular. + +_Dimensions._--Diameter of the shell 0.06 to 0.08, length of the tubules +0.03 to 0.04; inner aperture of the cones 0.01 to 0.02, outer aperture +0.008 to 0.01. + +_Habitat._--Indian Ocean, Cocos Islands, Rabbe, surface. + + +8. _Siphonosphaera fragilis_, n. sp. + +Shell quite irregular roundish or nearly ovate, very thin and fragile, +everywhere occupied by irregular, short, and broad cylindrical or conical +tubes. Six to ten tubes in the half meridian of the shell. Diameter of the +tubules about one-eighth that of the shell, three to four times as large as +the length of the tubules, and the distance apart of their bases. + +_Dimensions._--Diameter of the shell 0.16 to 0.24, of the tubules 0.02 to +0.03; length of the tubules 0.006 to 0.008, distance of them 0.005 to +0.009. + +_Habitat._--East coast of Australia, Sydney, Faber; Station 165, surface. + + + +Subgenus 2. _Merosiphonia_, Haeckel. + +_Definition._--Only part of the shell apertures prolonged in tubules, the +others simple. + + +9. _Siphonosphaera socialis_, n. sp. (Pl. 6, figs. 1, 2). + +Shell a regular or subregular sphere, bearing only a small number (one to +four, commonly two to three) of short and broad cylindrical tubules, +irregularly scattered. Between them many small circular or subcircular +pores of different sizes, double as broad as their bars. Eight to ten pores +in the half meridian of the shell. Tubules three to six times as broad as +the pores, about as long as broad, now quite cylindrical, now somewhat +dilated at the outer opening. (Although the shells and cells of this common +species are among the smallest, their colonies are among the largest, often +containing more than one hundred social individuals, often enclosed in +alveoles.) + +_Dimensions._--Diameter of the shell 0.04 to 0.05, of the pores 0.002 to +0.004, of the tubules 0.015 to 0.02; length of them about the same. + +_Habitat._--Tropical and subtropical part of the Eastern Atlantic, Cape +Verde Islands, Canaries, very common, Haeckel; Stations 338 to 353, +surface. + + +10. _Siphonosphaera polysiphonia_, n. sp. + +Shell a regular or subregular sphere, bearing twelve to sixteen circular +pores in its half meridian. Nearly one half the pores simple, very small; +the other half prolonged into short cylindrical tubules, {107}half as long +as broad, two to four times as broad as the pores and their intervals. This +species is nearly related to the foregoing, which it represents in the +western tropical part of the Atlantic, but differs constantly in the double +size of the shell and the much larger number of the tubules. + +_Dimensions._--Diameter of the shell 0.06 to 0.09, of the pores 0.002 to +0.004, of the tubules 0.01 to 0.012; their length 0.006 to 0.008, surface. + +_Habitat._--Tropical and subtropical part of the Western Atlantic, coast of +Brazil, &c., Rabbe. + + +11. _Siphonosphaera macrosiphonia_, n. sp. + +Shell a regular sphere, with numerous very small pores of equal size and +distribution. Twelve to sixteen pores in its half meridian. Bars (between +the pores) three to four times as broad as their diameter. Only a small +number (two to four) of very long cylindrical tubes, irregularly scattered, +nearly as long or somewhat longer than the shell diameter; now quite +straight, now somewhat curved. Diameter of the cylinders four to six times +as large as that of the pores. + +_Dimensions._--Diameter of the shell 0.1 to 0.12, of the pores 0.002 to +0.004, of the tubules 0.015 to 0.018; length of the tubules 0.08 to 0.16. + +_Habitat._--Central Tropical Pacific, Station 266 to 272, surface. + + +12. _Siphonosphaera serpula_, n. sp. (Pl. 6, fig. 6). + +Shell a regular sphere, with numerous very small pores of equal size and +distribution. Eight to ten pores in its half meridian; bars between them +three to four times as broad as their diameter. Only a small number (six to +eight) of very long and snake-like, contorted, cylindrical tubes, +irregularly scattered. The shape of the latter is very much like that of +the calcareous tubes of some species of _Serpula_; they are nearly as long +as, or longer than, the shell diameter, and four to six times as broad as +the pores. + +_Dimensions._--Diameter of the shell 0.12 to 0.14, of the pores 0.003 to +0.005, of the tubules 0.02 to 0.022; length of the tubules 0.1 to 0.2. + +_Habitat._--North Eastern Pacific, Station 252 to 262, Sandwich Islands, +Haltermann. + + +13. _Siphonosphaera chonophora_, n. sp. (Pl. 6, fig. 5). + +Shell a regular or subregular sphere, with numerous very small pores of +equal size and distribution, ten to twelve in its half meridian. Bars +between the pores four to six times their diameter. Only a small number +(two to six) of very large funnel-like tubules, irregularly scattered. The +inner half of these tubules is a short cylindrical tube, of the same +thickness as the shell, three to four times as broad as the pores; the +outer half is an irregular funnel, suddenly expanded, with siliceous walls +of the utmost tenuity and fragility, often irregularly folded and +contorted, like a decayed flower-calyx, often half as large as the shell. + +_Dimensions._--Diameter of the shell 0.1 to 0.12, of the pores 0.003 to +0.005, inner half of the tubules 0.015 to 0.02, outer funnel-like half 0.05 +to 0.08. + +_Habitat._--South Pacific, Stations 285 to 295, surface. + + +{108}14. _Siphonosphaera pipetta_, n. sp. (Pl. 6, fig. 3). + +Shell more or less irregularly roundish or subspherical, occupied in part +by very small pores, in part by very large cylindrical tubules, inflated in +the middle. Number, form, and size of the tubes very irregular; commonly +there are five to ten, half as long or as long as the shell radius; their +inner and outer aperture about half as broad as their inflated middle part; +three to nine times as broad as the pores. A very irregular and variable +species. + +_Dimensions._--Diameter of the shell 0.1 to 0.15, of the pores 0.001 to +0.005, of the tubules 0.015 to 0.03; length of the tubules 0.03 to 0.08. + +_Habitat._--North Pacific, Stations 242 to 253, surface. + + + +Genus 37. _Mazosphaera_,[59] Ehrenberg, 1860. + + _Mazosphaera_, Ehrenberg, 1860, Monatsber. d. k. preuss. Akad. d. Wiss. + Berlin, p. 833. + +_Definition._--#Collosphaerida# with simple shells, the pores of which are +prolonged into external simple radial tubuli with solid wall; outer mouth +of each tubulus armed with a single tooth. + +The genus _Mazosphaera_ is intermediate between _Siphonosphaera_ and +_Odontosphaera_, agreeing with the former in the tubular prolongation of +the pores, with the latter in the possession of a single large protective +tooth on the outer opening. + + +1. _Mazosphaera hippotis_, n. sp. (Pl. 5, fig. 8). + +Shell spherical, with circular pores of irregular size and distribution, +scarcely half as broad as the bars; fifteen to twenty on the half meridian +of the shell. Between them, irregularly distributed, a variable number (ten +to fifteen) of short cylindrical radial tubules, about twice as long as +broad, and half as long as the shell radius. Mouth of the tubuli obliquely +truncated, having on one side a strong acute tooth. + +_Dimensions._--Diameter of the shell 0.11 to 0.12, of the pores 0.002 to +0.004, of the bridges 0.006 to 0.009; length of the tubuli 0.03, breadth of +them 0.01 to 0.015. + +_Habitat._--North Pacific, Station 253, depth 3125 fathoms. + + +2. _Mazosphaera lagotis_, n. sp. (Pl. 5, fig. 9). + +Shell spherical, with circular pores of irregular size and distribution, +about as broad as the bars; twelve to sixteen on the half meridian. Between +them, irregularly distributed, a variable number (eight to twelve) of long, +cylindrical, curved tubules, three to six times as long as broad, and about +as long as the shell radius; their external mouth lateral, obliquely +truncated, ovate, having on one side a strong conical tooth. + +{109}_Dimensions._--Diameter of the shell 0.1 to 0.12, of the pores 0.002 +to 0.01; length of the tubuli 0.05 to 0.07. + +_Habitat._--Central Pacific, Station 266, depth 2750 fathoms. + + +3. _Mazosphaera laevis_, Ehrenberg. + + _Mazosphaera laevis_, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. + Berlin, p. 297, Taf. vii. fig. 7. + +Shell spherical, with very small pores, scarcely one-fourth as broad as the +bars. Fifteen to twenty pores on the half meridian of the shell. Between +them, irregularly distributed, a variable number (fifteen to twenty) of +short conical tubules, about as long as broad, only one-fifth to one-sixth +as long as the shell radius. Mouth of the tubuli truncated, with an obtuse +short tooth on one side. + +_Dimensions._--Diameter of the shell 0.08 to 0.09, of the pores 0.001 to +0.002, of the bridges 0.005 to 0.008; length of the tubuli 0.01 to 0.02, +breadth of them the same. + +_Habitat._--Philippine Islands (depth 3300 fathoms), Ehrenberg; Station +206, depth 2100 fathoms; Station 225, depth 4575 fathoms. + + +4. _Mazosphaera apicata_, Ehrenberg. + + _Mazosphaera apicata_, Ehrenberg, 1872, Monatsber. d. k. preuss. Akad. d. + Wiss. Berlin, p. 316. + +Shell spherical, without small pores, only with a variable number (ten to +twenty) of short conical tubules, twice as long as broad, and half as long +as the shell radius. Mouths of the tubuli obliquely truncated, with a +strong acute tooth on one side. (This species differs from the two +preceding by the want of the small pores between the tubules.) + +_Dimensions._--Diameter of the shell 0.08 to 0.1, of the tubules 0.01. + +_Habitat._--Philippine Islands (depth 3300 fathoms), Ehrenberg; north coast +of New Guinea, depth 2000 fathoms; Station 217. + + + +Genus 38. _Trypanosphaera_,[60] n. gen. + +_Definition._--#Collosphaerida# with simple shells, the pores of which are +prolonged into external simple radial tubuli with solid walls; outer mouth +of each tubulus armed with a coronal of spines. + +The genus _Trypanosphaera_ is intermediate between _Siphonosphaera_ and +_Choenicosphaera_ agreeing with the former in the tubular prolongation of +the pores, with the latter in the possession of a coronal of teeth on their +outer opening. + + + +Subgenus 1. _Trypanosphaerula_, Haeckel. + +_Definition._--All pores of the shell prolonged into short coronated +tubules. + + +{110}1. _Trypanosphaera trepanata_, n. sp. (Pl. 5, fig. 4). + +Shell regular spherical, with regular circular pores of nearly equal size, +at unequal distances, one to four times as broad as the bars. Eight to ten +pores on the half meridian. All the pores prolonged into short cylindrical +tubuli about as long as broad, armed on the external mouth with an elegant +coronal of twenty to thirty straight bristle-shaped, parallel teeth. + +_Dimensions._--Diameter of the shell 0.12 to 0.14, of the pores 0.015 to +0.02; length of the tubuli 0.02. + +_Habitat._--Central Pacific, Station 268, depth 2900 fathoms. + + +2. _Trypanosphaera dentata_, n. sp. + +Shell regular spherical, with regular circular pores of equal size, but at +very different distances. Only three to four pores on the half meridian. +All the pores prolonged into irregular curved, cylindrical tubuli, about as +long as the shell radius, with a coronal of ten to twelve short conical +teeth on the distal end. + +_Dimensions._--Diameter of the shell 0.08 to 0.09; length of the tubuli +0.04, breadth 0.02. + +_Habitat._--Central Pacific, Station 274, depth 2750 fathoms. + + + +Subgenus 2. _Trypanosphaerium_, Haeckel. + +_Definition._--Only part of the shell-pores prolonged into coronated +tubules. + + +3. _Trypanosphaera coronata_, n. sp. (Pl. 5, fig. 3). + +Shell regular spherical, with irregular roundish pores of very different +sizes. On the half meridian four to six large and twelve to sixteen very +small pores. About half of the large pores prolonged into short cylindrical +tubuli, the outer mouth of each being armed with an elegant coronal of ten +to twenty thin irregular teeth. + +_Dimensions._--Diameter of the shell 0.1 to 0.12, of the large pores 0.01 +to 0.02, of the small pores 0.001; length of the tubuli 0.012. + +_Habitat._--North Pacific, Station 241, depth 2300 fathoms. + + +4. _Trypanosphaera terebrata_, n. sp. + +Shell irregular roundish, with unequal, small, roundish pores. Sixteen to +twenty pores on the half meridian. Six to eight larger pores are prolonged +into curved cylindrical tubuli, about as long as the shell radius, with a +coronal of ten to twelve strong conical straight teeth on the distal end. + +_Dimensions._--Diameter of the shell 0.15, of the pores 0.001 to 0.003; +length of the tubuli 0.08, breadth 0.02. + +_Habitat._--West Tropical Pacific, Station 225, depth 4575 fathoms. + + +{111}5. _Trypanosphaera transformata_, n. sp. (Pl. 5, figs. 1, 2). + +Shell quite irregular, of very variable, roundish, or polyhedral form, with +small irregular roundish pores, two to four times as broad as the bars. Ten +to thirty on the half meridian. The different form of the shell depends +upon the variable number of tubuli, which arise at irregular distances from +the shell; commonly three to four, often also five to six, more rarely one +or two. The tubuli are now more conical, now more cylindrical, about as +long as the shell radius, at other times scarcely one-half or one-third as +long, with a coronal of ten to twenty more or less curved teeth on the +narrower distal mouth. All the different forms are to be found in one and +the same colony, as shown in fig. 1. This coenobium, which I observed +living in Ceylon, exhibited the same peculiar formation as I figured in +_Collosphaera huxleyi_ in my Monograph 1862 (Taf. xxxiv. fig. 1). In the +centre of the jelly-sphere lies a large globular alveole, surrounded by +numerous small, young central capsules without shell; whilst in the surface +lies one layer of older capsules, enclosed in shells. Some of the younger +capsules exhibit self-division. + +_Dimensions._--Diameter of the shells 0.08 to 0.12, pores 0.002 to 0.006; +length and breadth of the tubuli 0.03 to 0.05. + +_Habitat._--Indian Ocean, Belligemma, Ceylon, surface. + + + +Genus 39. _Caminosphaera_,[61] n. gen. + +_Definition._--#Collosphaerida# with simple shells, the pores of which are +prolonged into external branched radial tubuli with solid wall. + +The genus _Caminosphaera_ differs from _Siphonosphaera_ (and from all other +Collosphaerida) in the ramification of the tubuli, which arise from the +pores; the walls of the tubuli are solid, not fenestrated. + + +1. _Caminosphaera furcata_, n. sp. + +Shell spherical or subspherical, with a variable number (four to eight) of +short cylindrical tubes, irregularly scattered, about as long as the radius +of the shell. Every tube forked, with two cylindrical branches of the same +size as the simple basal part of the tube. Mouth of the branches truncated, +not dilated. Pores of the shell between the tubes very small, all of the +same size, half as broad as their bars. Fifteen to twenty pores in the +half meridian of the shell. + +_Dimensions._--Diameter of the shell 0.1 to 0.12, of the pores 0.001 to +0.002; length of the tubules 0.05 to 0.06, breadth of them 0.012 to 0.015. + +_Habitat._--North Pacific, Station 244, depth 2900 fathoms. + + +2. _Caminosphaera elongata_, n. sp. + +Shell spherical, with a large number (twelve to twenty) of long cylindrical +tubes, irregularly formed and scattered, somewhat longer than the diameter +of the shell. Every tube forked at {112}the distal end, with two or three +short irregular branches of unequal size and form; branches much shorter +than the undivided basal part of the tube. Mouth of the branches narrowed, +truncated. Pores of the shell between the tubes about half as broad, +irregularly roundish or polygonal, two to three times as broad as their +bars. Ten to twelve pores in the half meridian of the shell. + +_Dimensions._--Diameter of the shell 0.05 to 0.07, of the pores 0.006 to +0.009; length of the tubules 0.06 to 0.09, breadth of them 0.015 to 0.02. + +_Habitat._--Tropical Central Pacific, Station 271, depth 2425 fathoms. + + +3. _Caminosphaera dichotoma_, n. sp. (Pl. 7, fig. 2). + +Shell spherical, with a variable number (ten to fifteen) of cylindrical +tubes, irregularly scattered, about as long as the radius of the shell. +Every tube furcated, with two cylindrical branches of the same size as the +simple basal part of the tube. Mouth of the branches dilated, funnel-like, +twice as broad as the tube; the edges irregularly dentated or lacerated. +Pores between the tubes small, one-third to one-sixth as broad as these, +half as broad as their bars. Ten to twelve pores in the half meridian of +the shell. + +_Dimensions._--Diameter of the shell 0.12 to 0.14, of the pores 0.003 to +0.005; length of the tubules 0.06 to 0.08, breadth of them 0.02 to 0.03. + +_Habitat._--Southern Pacific, Station 295, depth 1500 fathoms. + + +4. _Caminosphaera dendrophora_, n. sp. (Pl. 7, fig. 1). + +Shell spherical, with a variable number (eight to twelve) of long +cylindrical tubes, irregularly branched and scattered, nearly as long as +the diameter of the shell. Every tube with two to six (commonly three to +four) branches of different sizes. Mouth of the branches dilated, +funnel-like; the edges irregularly dentated or lacerated. Pores between the +tubes half as broad as these, irregularly roundish, twice as broad as their +bars. Ten to twelve pores in the half meridian of the shell. + +_Dimensions._--Diameter of the shell 0.12 to 0.15, of the pores 0.006 to +0.01; length of the tubules 0.1 to 0.13, breadth of them 0.02 to 0.025. + +_Habitat._--Central Pacific, Station 266, depth 2750 fathoms. + + + +Genus 40. _Solenosphaera_,[62] n. gen. + +_Definition._--#Collosphaerida# with simple shells, the pores of which are +prolonged into external simple radial tubuli with fenestrated wall; outer +mouth of the tubuli truncated, smooth. + +The genus _Solenosphaera_ differs from _Siphonosphaera_ in the fenestration +of the external radial tubes. A large number of shells, appertaining to +this genus, were already described by Ehrenberg, and disposed in five +different genera corresponding to the {113}different numbers of the +tubuli:--_Disolenia_ with two tubes, _Trisolenia_ with three tubes, +_Tetrasolenia_ with four tubes, _Pentasolenia_ with five tubes, +_Polysolenia_ with six or more tubes. All these five genera are without +value, as those different numbers of tubes occur frequently intermingled in +the individual cells of one and the same colony, wherever the form and +structure of the tubes is inherited with sufficient constancy to determine +the species. + + + +Subgenus 1. _Solenosphactra_, Haeckel. + +_Definition._--Tubuli of the shell cylindrical or nearly cylindrical, the +outer and inner apertures nearly of the same size. + + +1. _Solenosphaera variabilis_, Haeckel. + + _Tetrasolenia quadrata_, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. + Berlin, Taf. x. fig. 20. + +Shell quite irregular roundish or polyhedral, with roundish pores of +different size. Ten to fifteen pores in the half meridian of the shell, two +to three times as broad as the bars. Porous tubuli of the shell in variable +number (in one and the same colony), three to nine, mostly four to six; +cylindrical or subcylindrical or somewhat conical, two to three times as +broad as long, not longer than the half radius of the shell. Inner aperture +of the tubuli commonly as broad as the half radius of the shell (or +somewhat smaller), about as large as the truncated outer aperture. This +species is closely related to _Collosphaera polyedra_ (p. 97), and may be +derived from it by a short tube-like prolongation of the larger apertures. + +_Dimensions._--Diameter of the shell 0.1 to 0.16, of the pores 0.005 to +0.015; length of the tubules 0.02 to 0.03, breadth of them 0.04 to 0.06. + +_Habitat._--Central area of the Tropical Pacific, Stations 270, 271, 272, +depths 2425 to 2925 fathoms. + + +2. _Solenosphaera pandora_, n. sp. (Pl. 7, figs. 10, 11). + +Shell irregular roundish or subglobular, with roundish pores of different +sizes, mostly somewhat broader than the bars. About twelve to sixteen pores +on the half meridian of the shell. Porous tubuli of the shell of variable +number (in one and the same colony), one to six, mostly three to four; +cylindrical or nearly cylindrical, somewhat longer than broad, not longer +than the radius of the shell. Inner aperture of the tubuli commonly as +broad as the half radius of the shell, and a little smaller than the +truncated outer aperture. + +_Dimensions._--Diameter of the shell 0.07 to 0.1, of the pores 0.003 to +0.006; length of the tubuli 0.03 to 0.05, breadth of them 0.02 to 0.03. + +_Habitat._--Central area of the Tropical Pacific, Stations 266 to 274, +depths 2350 to 2925 fathoms. + + +{114}3. _Solenosphaera megalactis_, Haeckel. + + _Trisolenia megalactis_, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. + Berlin, p. 301, Taf. viii. fig. 19. + +Shell irregularly polyhedrical, with very small roundish pores, scarcely +half as broad as the bars. Only eight to ten pores on the half meridian of +the shell. Porous tubuli of the shell of variable number (in one and the +same colony), two to five, mostly three or four; cylindrical, about as long +as the radius of the shell. Inner aperture of the tubuli commonly as broad +as the half radius of the shell, and quite as broad as the truncated outer +aperture. + +_Dimensions._--Diameter of the shell 0.07 to 0.09, of the pores 0.002 to +0.004, of the bars 0.005 to 0.009; length of the tubuli 0.03 to 0.04, +breadth of them 0.02. + +_Habitat._--Pacific; California, Philippine Sea, Ehrenberg; Stations 256 to +285, depths 310 to 3000 fathoms. + + +4. _Solenosphaera serpentina_, n. sp. (Pl. 7, fig. 7). + +Shell nearly spherical, with very small circular pores, scarcely one-third +or one-fourth as broad as the bars. Only five to seven pores in the half +meridian of the shell. Porous tubuli of the shell of variable number (in +one and the same colony), two to nine, mostly seven or eight; cylindrical, +somewhat curved or contorted, once and a half or twice as long as the +diameter of the shell, with few very small and widely scattered pores. +Inner and outer aperture of the tubuli have the same diameter, about +one-fifth or one-fourth that of the shell. (This species is closely allied +to _Siphonosphaera serpula_, but is distinguished from it by the long +tortuous tubuli and the small scarce pores.) + +_Dimensions._--Diameter of the shell 0.08 to 0.1, of the pores 0.001 to +0.002, of the bars 0.004 to 0.008; length of the tubuli 0.12 to 0.18, +breadth of them 0.02 to 0.025. + +_Habitat._--North-eastern Pacific, between Sandwich Islands and California, +Haltermann, surface. + + + +Subgenus 2. _Solenosphenia_, Haeckel. + +_Definition._--Tubuli of the shell more or less conical, the inner aperture +much larger than the outer aperture. + + +5. _Solenosphaera venosa_, Haeckel. + + _Tetrasolenia venosa_, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. + Berlin, p. 301, Taf. vii. fig. 22. + +Shell irregular polyhedral or roundish, with a delicate network of large +irregular polyhedral meshes, five to ten times as broad as the thin bars. +Eight to twelve meshes on the half meridian of the shell. Fenestrated +tubuli of the shell of variable number (in one and the same colony), one to +five, commonly three or four, shaped like a short truncated cone, about +half as long as broad on its base, shorter than the radius of the shell. +Inner aperture of the cone nearly as broad as the half radius of the shell, +about twice as broad as the truncated outer aperture. + +{115}_Dimensions._--Diameter of the shell 0.07 to 0.12, of the pores 0.008 +to 0.016, of the bars 0.001; length of the tubuli 0.02 to 0.03, inner +aperture 0.03 to 0.04, outer aperture 0.02 to 0.03. + +_Habitat._--Indian Ocean, Sunda Strait, Rabbe. + + +6. _Solenosphaera ascensionis_, n. sp. (Pl. 7, fig. 9). + +Shell somewhat irregular, subspherical, with polygonal pores of different +size. Twelve to fifteen pores in the half meridian of the shell, two to +eight times as broad as their bars. Porous tubuli of the shell of variable +number (in one and the same colony), three to nine, mostly five to seven; +conical or nearly cylindrical, irregular, about as long as broad at their +base. Inner aperture of the tubuli two to four times as broad as the +broadest pores, and double as broad as the truncated circular outer +aperture. + +_Dimensions._--Diameter of the shell 0.1 to 0.12, of the pores 0.004 to +0.018, of the bars 0.002, length of the tubuli 0.04, inner aperture 0.04, +outer 0.02. + +_Habitat._--South Atlantic, near Ascension Island, Station 343, surface. + + + +Subgenus 3. _Solenosphyra_, Haeckel. + +_Definition._--Tubuli of the shell funnel-like, the outer aperture much +larger than the inner. + + +7. _Solenosphaera cornucopia_, n. sp. (Pl. 7, fig. 8). + +Shell spherical or subspherical, with roundish pores of different size. Ten +to twelve pores in the half meridian of the shell, two to three times as +broad as the bars. Porous tubuli of the shell of variable number (in one +and the same colony), four to eight, mostly five to seven, funnel-like, +about as long as the diameter of the shell. Inner aperture of the tubuli +commonly two-thirds or three-fourths as broad as the radius of the shell +(or somewhat smaller), only one-half or two-thirds as broad as the dilated +and truncated outer aperture. + +_Dimensions._--Diameter of the shell 0.07 to 0.09, of the pores 0.006 to +0.018; length of the tubuli 0.06 to 0.08, diameter of the inner aperture +0.04 to 0.05, of the outer 0.06 to 0.08. + +_Habitat._--Central Pacific, Station 271, depth 2425 fathoms. + + +8. _Solenosphaera amalthea_, n. sp. + +Shell irregular roundish or spherical, with small circular pores of +different size. Fifteen to twenty pores in the half meridian of the shell, +but still not as broad as the bars. Porous tubuli of the shell of variable +number (in one and the same colony), three to six, commonly four or five, +funnel-like, about as long as the radius of the shell. Inner aperture of +the tubuli about half as broad as the radius of the shell, only one-half or +one-third as broad as the truncated outer aperture. (This species is +intermediate between the preceding and _Siphonosphaera chonophora_, Pl. 6, +fig. 5.) + +{116}_Dimensions._--Diameter of the shell 0.09 to 0.11, of the pores 0.002 +to 0.004, of the bars 0.003 to 0.006; length of the tubuli 0.05 to 0.06; +diameter of the inner aperture 0.02 to 0.03, of the outer aperture 0.05 to +0.07. + +_Habitat._--Western part of the South Atlantic, Station 325, surface. + + + +Genus 41. _Otosphaera_,[63] n. gen. + +_Definition._--#Collosphaerida# with simple shells, the pores of which are +prolonged into external simple radial tubuli with fenestrated walls; outer +mouth of the tubuli armed with a single tooth. + +The genus _Otosphaera_ differs from _Solenosphaera_ by the single tooth on +the external mouth of the tubuli, from _Mazosphaera_ by the fenestration of +the walls of the tubuli. + + +1. _Otosphaera polymorpha_, n. sp. (Pl. 7, fig. 6). + +Shell quite irregular, polyhedral or roundish, very variable in size and +form, with numerous very small pores, much smaller than the bars. Twenty to +thirty pores in the half meridian of the shell. Porous tubuli of the shell +commonly in variable number (one to four), but sometimes constant in number +(one, two, three, or four) in the one and same colony. Tubuli irregular +conical, commonly about as long as the radius of the shell; their outer +aperture obliquely truncated, on one side prolonged into one large, +prominent, bill-like, curved, acute tooth. + +_Dimensions._--Diameter of the shell 0.12 to 0.15, of the pores 0.001 to +0.002; length of the tubuli 0.06 to 0.08, inner aperture 0.03, outer +aperture 0.02. + +_Habitat._--Indian Ocean, Madagascar, Rabbe, surface. + + +2. _Otosphaera auriculata_, n. sp. (Pl. 7, fig. 5). + +Shell quite irregular, of extremely variable form, now inclining to +roundish, now to polyhedral, with very numerous small pores, irregularly +formed and distributed. Twelve to twenty-four pores in the half meridian of +the shell, of very different size, for the most part larger than the bars. +Porous tubuli of the shell of variable number (in one and the same colony), +one to five, mostly three or four, of conical form, irregularly formed and +scattered, commonly about half as long as the radius of the shell. Outer +aperture of the tubuli obliquely truncated, with one large prominent, often +curved, acute tooth. + +_Dimensions._--Diameter of the shell 0.1 to 0.2, of the pores 0.003 to +0.005; length of the tubuli 0.01 to 0.05, inner aperture 0.04, outer +aperture 0.03. + +_Habitat._--Central Tropical Pacific, Stations 268 to 272, depths 2425 to +2925 fathoms. + + + +{117}Genus 42. _Coronosphaera_,[64] n. gen. + +_Definition._--#Collosphaerida# with simple shells, the pores of which are +prolonged into external simple radial tubuli with fenestrated walls; outer +mouth of the tubuli armed with a coronal of spines. + +The genus _Coronosphaera_ differs from _Solenosphaera_ by the coronated +mouth of the tubuli, from _Trypanosphaera_ by the fenestration of the walls +of the tubuli. + + +1. _Coronosphaera diadema_, n. sp. (Pl. 7, fig. 3). + +Shell spherical or subspherical, with a variable number (fifteen to twenty) +of short, coronal-like tubules, irregularly scattered, about half as long +as the radius of the shell. Outer aperture of the tubuli irregularly +dentated, a little dilated, and not much broader than the inner aperture, +one-half or one-third as broad as the shell radius. Pores of the shell and +of the tubuli circular or roundish, very irregularly scattered, mostly +one-half or one-third as broad as the bars. + +_Dimensions._--Diameter of the shell 0.11 to 14, of the pores 0.002 to +0.004, of the bars 0.006 to 0.012; length of the tubuli 0.03, inner +aperture 0.02 to 0.03, outer aperture 0.03 to 0.04. + +_Habitat._--Central Pacific, Stations 268 to 270, depths 2550 to 2925 +fathoms. + + +2. _Coronosphaera calycina_, n. sp. (Pl. 7, fig. 4). + +Shell spherical or subspherical, with a variable number (eight to twelve) +of large, funnel-like tubules, irregularly scattered, about as long as the +radius of the shell. Outer aperture of the tubuli irregularly dentated, +much dilated, somewhat broader than the shell radius, three to four times +as broad as the inner circular aperture. Pores of the shell and of the +tubuli circular or roundish, of very different size, one to three times as +broad as the bars. + +_Dimensions._--Diameter of the shell 0.1 to 0.3, of the pores 0.003 to +0.01, of the bars 0.002 to 0.004; length of the tubuli 0.1, inner aperture +0.02 to 0.03, outer aperture 0.06 to 0.18. + +_Habitat._--Central Pacific, Stations 271, 272, depths 2425 and 2600 +fathoms respectively. + + +3. _Coronosphaera convolvulus_, n. sp. + +Shell irregular roundish, with a variable number (five to ten) of long, +curved tubules, about as long as the shell diameter. The inner half of the +tubuli is narrow, cylindrical; the outer half funnel-like dilated, similar +to the flower of _Convolvulus_. The outer aperture is elegantly dentated, +five to six times as broad as the inner aperture. Pores of the shell and of +the tubuli very irregular roundish, about as broad as the bars. + +_Dimensions._--Diameter of the shell 0.08 to 0.09, of the pores and bars +0.004 to 0.008; length of the tubuli 0.07 to 0.1, inner aperture 0.01, +outer aperture 0.05. + +_Habitat._--Tropical Atlantic, Station 347, surface. + + + +{118}Subfamily CLATHROSPHAERIDA, Haeckel, 1881, Prodromus, p. 472. + +_Definition._--#Collosphaerida# with a double lattice-shell around every +central capsule of the coenobium; both concentric shells connected by +irregular or subradial beams, commonly solid or lamellar staffs, rarely +hollow tubes. + + + +Genus 43. _Clathrosphaera_,[65] Haeckel, 1881, Prodromus, p. 472. + +_Definition._--#Collosphaerida# with a double lattice-shell around every +central capsule of the coenobium; surface of the outer shell smooth. + +The genus _Clathrosphaera_ (with smooth surface) and the following +_Xanthiosphaera_ (with spiny surface) form together the small subfamily, +Clathrosphaerida, different from the other Collosphaerida by the double +lattice-shell. From the surface of the inner primary shell arise either +solid spines or hollow tubes, which unite by the anastomosis of irregular +branches and so form the outer secondary shell, often very incomplete and +irregular. All Clathrosphaerida seem to inhabit great depths. + + + +Subgenus 1. _Clathrosphaerula_, Haeckel. + +_Definition._--The connecting staffs between both shells are hollow tubes +(derived from _Siphonosphaera_). + + +1. _Clathrosphaera circumtexta_, n. sp. (Pl. 8, fig. 6). + +Inner shell spherical, with irregular roundish large meshes, now broader +now smaller than their bars. Eight to ten meshes in the half meridian of +the shell. All these meshes are prolonged into short cylindrical hollow +tubes, about as long as broad, somewhat constricted in the middle. From the +margins of the outer openings of these tubes proceed very numerous and +delicate siliceous filaments, which all lie on the same spherical face, +branch, anastomose, and twine over the openings and the intervals between +them, forming a very thin, arachnoid spherical outer shell. The meshes of +this are quite irregular polygonal, of very different size and form. The +radius of the inner shell bears to that of the outer a ratio = 5 : 6. + +_Dimensions._--Diameter of the inner shell 0.11 to 0.13, of the outer 0.13 +to 0.16; meshes of the inner shell 0.005 to 0.02, of the outer 0.005 to +0.04. + +_Habitat._--North Pacific, Stations 238 to 253, depths 2050 to 3950 +fathoms. + + + +Subgenus 2. _Clathrosphaerium_, Haeckel. + +_Definition._--The connecting staffs between the two shells are solid rods +or lamellar spines (derived from _Acrosphaera_). + + +{119}2. _Clathrosphaera arachnoides_, n. sp. (Pl. 8, fig. 7). + +Inner shell spherical, with irregular roundish meshes, two or three times +as broad as the bars. Ten to twelve meshes in the half meridian of the +shell. From its surface arise numerous conical radial spines (with base +often fenestrated), which at equal distances from the surface send out +lateral branches. All these branches lie on a spherical face, and form by +communications the irregular, very delicate, arachnoid network of the outer +shell, quite unlike that of the inner, with large polygonal meshes of very +different size. Eight to sixteen meshes in the half meridian of the shell. +Surface of the outer shell nearly spherical, somewhat uneven, like a +spider's web. The radius of the inner shell bears to that of the outer a +ratio = 3 : 4. + +_Dimensions._--Diameter of the inner shell 0.12 to 0.14, of the outer 0.15 +to 0.18; pores of the inner shell 0.003 to 0.02, of the outer 0.01 to 0.04. + +_Habitat._--Central area of the Tropical Pacific, Station 268, depth 2900 +fathoms. + + +3. _Clathrosphaera lamellosa_, n. sp. (Pl. 8, fig. 8). + +Inner shell spherical or subspherical, with irregular roundish meshes, +about half as broad as the bars. Twelve to sixteen meshes in the half +meridian of the shell. From its surface arise numerous oblique irregular +staffs or broad and thin lamellae, which branch quite irregularly, and by +communications of the branches form the thin outer shell. This is quite +irregular roundish or subspherical, very unlike the inner, with large +polygonal meshes of different size, six to twelve in the half meridian of +the shell. Bridges between the meshes very variable, now very thin +filamentous, now very broad lamellar. Outer surface very uneven or +tuberculated, but not spinous. The radius of the inner shell bears to that +of the outer a ratio = 5 : 6. + +_Dimensions._--Diameter of the inner shell 0.1 to 0.13, of the outer 0.12 +to 0.18; pores of the inner shell 0.003 to 0.009, of the outer 0.01 to +0.04. + +_Habitat._--Central area of the Tropical Pacific, Stations 270 to 274, +depths 2350 to 2925 fathoms. + + + +Genus 44. _Xanthiosphaera_,[66] Haeckel, 1881, Prodromus, p. 472. + +_Definition._--#Collosphaerida# with a double lattice-shell around every +central capsule of the coenobium; surface of the outer shell thorny or +spiny. + +The genus _Xanthiosphaera_ differs from the foregoing _Clathrosphaera_ by +spines or thorns arising from the surface of the outer shell, commonly very +irregular. + + +1. _Xanthiosphaera capillacea_, n. sp. + +Inner shell spherical, with irregular polygonal meshes, three to five times +as broad as their narrow bars. Six to eight meshes in the half meridian of +the shell. From its surface arise at the nodes of the network numerous thin +radial spines, which, at equal distances from the surface, {120}send out +lateral branches. All these branches lie on a spherical face, and form by +communications the irregular delicate network of the outer shell, very like +that of the inner, with large polygonal meshes, six to eight meshes in the +half meridian of the shell. Surface of the outer shell covered with +numerous straight spines, prolongations of the inner spines, but only half +as long as these. The radius of the inner shell bears to that of the outer +a ratio = 3 : 5. + +_Dimensions._--Diameter of the inner shell 0.1 to 0.12, of the outer 0.15 +to 0.19; pores of the inner shell 0.02 to 0.04 to 0.06, of the outer 0.04 +to 0.06 to 0.08; length of the outer spines 0.01 to 0.02. + +_Habitat._--Central area of the Tropical Pacific, Station 263, depth 2650 +fathoms. + + +2. _Xanthiosphaera erinacea_, n. sp. (Pl. 8, fig. 9). + +Inner shell spherical, with irregular roundish meshes, one-half to two +times as broad as the bars. Fifteen to twenty meshes in the half meridian +of the shell. From its surface arise numerous thin radial spines, which at +equal distances from the surface send out lateral branches. All these +branches lie on the face of a sphere, and form by communications the +irregular delicate network of the outer shell, very unlike that of the +inner, with large polygonal meshes, twelve to twenty-four in the half +meridian of the shell. Surface of the outer shell covered with numerous +straight spines, prolongations of the inner spines, and of the same length. +The radius of the inner shell bears to that of the outer a ratio = 3 : 4. + +_Dimensions._--Diameter of the inner shell 0.1 to 0.12, of the outer 0.13 +to 0.16; pores of the inner shell 0.002 to 0.008, of the outer 0.01 to +0.03; length of the outer spines 0.02 to 0.03. + +_Habitat._--Central area of the Tropical Pacific, Stations 270, 272, depth +2925 and 2600 fathoms respectively. + + +3. _Xanthiosphaera lappacea_, n. sp. (Pl. 8, figs. 10, 11). + +Inner shell spherical or subspherical, with very small roundish pores, +quite irregularly scattered, one-fourth to three-fourth as broad as their +bars. Ten to twenty pores in the half meridian of the shell. From its +surface arise in an extremely irregular and variable manner numerous +oblique spines, often curved, often lamellar, and perforated by pores, +sometimes hollow, fenestrated cones. At different distances from the +surface these spines send out lateral curved branches, which by +communications form the delicate and very irregular network of the outer +shell. This network is often incomplete and very unlike that of the inner +shell, with large polygonal meshes, six to eighteen in the half meridian of +the shell. Surface of the outer shell covered with numerous small, curved, +and oblique spines, prolongations of the inner spines, but scarcely +one-third to one-half as long as these. The radius of the inner shell bears +to that of the outer a ratio = 3 : 4. + +_Dimensions._--Diameter of the inner shell 0.08 to 0.12, of the outer 0.11 +to 0.15; pores of the inner shell 0.001 to 0.009, of the outer 0.01 to +0.04; length of the outer spines 0.005 to 0.009. + +_Habitat._--Central area of the Tropical Pacific, Stations 263 to 274, +depths 2350 to 3000 fathoms. + + + +{121}Family VII. #STYLOSPHAERIDA#, Haeckel (Pls. 13-17). + +_Stylosphaerida_, Haeckel, 1881, Prodromus, p. 449. + +_Definition._--#Sphaeroidea# with two radial spines on the surface of the +spherical shell, opposite in one axis; living solitary (not associated in +colonies). + +The family #Stylosphaerida# comprises a large number of very common +#Sphaeroidea#, and is distinguished from all others by the possession of +two radial spines which are placed in one axis of the spherical shell.[67] +By the expression of this "main axis" as a solid rod they form the +transition to the #Prunoidea#, in which the whole shell is more or less +transformed according to this "monaxial growth." But in these latter the +shell, as well as the central capsule, becomes ellipsoidal, prolonged in +one axis, whilst in the former they remain spherical. However, the +distinction of both nearly allied groups is sometimes difficult. + +The most simple Stylosphaerida are the _Xiphostylida_, with one single +spherical lattice-shell. To this ancestral group all other subfamilies can +be opposed as "Stylosphaerida concentrica," as their carapace is composed +of two or more concentric lattice-shells: two in the Sphaerostylida, three +in the Amphistylida, four in the Cromyostylida, five or more in the +Caryostylida. In all these four subfamilies the concentric shells are +simple (not spongy) fenestrated spheres. In a sixth subfamily, in the +Spongostylida, the shell is wholly or partially composed of a spongy +irregular wicker-work, with or without a medullary shell in the centre. + +Both the radial spines in all Stylosphaerida are opposed normally in one +axis; but in many species besides the normal form occur individual +abnormalities, in which the two spines are not accurately opposed in this +main axis, but placed in two different axes, intersecting at a smaller or +larger angle. In the majority of the Stylosphaerida both opposite spines +have the same size and form; but in some genera they are more or less +different, often in a very striking degree. The same differences occur in +the nearly allied groups of #Prunoidea#, in the Ellipsida and Druppulida. + +The distal ends of both spines are commonly free; but in the small group of +Saturnalida (_Saturnalis_ with one single shell, _Saturnulus_ with two +concentric shells, _Saturninus_ with three concentric shells) the distal +ends of both spines are united, at equal distances from the centre, by a +circular or elliptical ring. This remarkable peculiarity occurs in no other +group of #Sphaeroidea#, and consequently brings the Saturnalida into close +relation with the #Discoidea#. + +{122}_Synopsis of the Genera of Stylosphaerida._ + + { {Both spines + {Polar spines { equal, 45. _Xiphosphaera_. + { free, without{ + I. Subfamily { connecting {Spines + Xiphostylida. { ring on the { different + (Spherical shell{ distal ends. { in size + simple.) { { or form, 46. _Xiphostylus_. + { + {Both polar spines united by + { a circular or elliptical + { ring, 47. _Saturnalis_. + + { {Both spines + { { equal, 48. _Stylosphaera_. + {Polar spines { + II. Subfamily { free. {Spines + Sphaerostylida.{ { different in + (Two concentric { { size or + spheres.) { { form, 49. _Sphaerostylus_. + { + {Both polar spines united by + { a circular or elliptical + { ring, 50. _Saturnulus_. + + { {Both spines + { { equal, 51. _Amphisphaera_. + {Polar spines { + III. Subfamily { free. {Spines + Amphistylida. { { different in + (Three { { size or + concentric { { form, 52. _Amphistylus_. + spheres.) { + {Both polar spines united by + { a circular or elliptical + { ring, 53. _Saturninus_. + + IV. Subfamily } {Both spines + Cromyostylida.}Polar spines { equal, 54. _Stylocromyum_. + (Four concentric} free. { + spheres.) } {Spines + } { different, 55. _Cromyostylus_. + + V. Subfamily } + Caryostylida. }Polar spines {Both spines + (Five or more } free. { equal, 56. _Caryostylus_. + concentric } + spheres.) } + + {Shell a solid spongy sphere + { without central medullary + { shell, 57. _Spongolonchis_. + VI. Subfamily { + Spongostylida.{ {One central + (Spherical shell{ { medullary + partially or {In the centre { shell, 58. _Spongostylus_. + wholly of a { of the spongy{ + spongy { sphere one or{Two + structure.) { two medullary{ concentric + { shells. { medullary + { { shells, 59. _Spongostylidium_. + + + +Subfamily XIPHOSTYLIDA, Haeckel, 1881, Prodromus, pp. 449, 450. + +_Definition._--#Stylosphaerida# with one simple spherical lattice-shell. + + + +Genus 45. _Xiphosphaera_,[68] Haeckel, 1881, Prodromus, p. 450. + +_Definition._--#Stylosphaerida# with one single lattice-sphere and two free +spines of equal size and form. + +The genus _Xiphosphaera_ is the most simple form of all Stylosphaerida, and +may be regarded as the common ancestral form of this family. On the surface +of a simple {123}spherical lattice-shell, enclosing the central capsule, +arise two equal, free, radial spines, opposite to each other on the poles +of one axis. + + + +Subgenus 1. _Xiphosphaerantha_, Haeckel. + +_Definition._--Pores of the spherical shell regular, of nearly equal size +and form; surface smooth or a little rough, without spines or thorns (other +than the two polar spines). + + +1. _Xiphosphaera planeta_, n. sp. + +Pores regular, hexagonal, eight to nine times as broad as the thin bars. +Ten to twelve pores on the half equator. Shell very thin walled; surface +smooth. Polar spines three-sided pyramidal, about as long as the axis of +the sphere, as broad at the base as one pore. + +_Dimensions._--Diameter of the sphere 0.12 to 0.13, pores 0.016 to 0.018, +bars 0.002; length of the polar spines 0.1 to 0.15, basal thickness 0.02. + +_Habitat._--Pacific, central area, surface; Stations 271 to 274, depths +2425 to 2750 fathoms. + + +2. _Xiphosphaera gaea_, n. sp. (Pl. 14, fig. 5). + +Pores regular, circular, with prominent hexagonal crests between them. On +the half equator ten to twelve pores, of the same breadth as the crested +bars. Shell thin walled; surface smooth. Polar spines three-sided +prismatic, about twice as long as the axis of the sphere, twice as broad at +the base as one pore. + +_Dimensions._--Diameter of the sphere 0.07 to 0.09, pores and bars 0.005; +length of the polar spines 0.15 to 0.2, basal thickness 0.01. + +_Habitat._--Pacific, central area, Station 274, depth 2750 fathoms. + + +3. _Xiphosphaera venus_, n. sp. (Pl. 14, fig. 2). + +Pores regular, circular, with prominent hexagonal frames. On the half +equator fifteen to eighteen pores, of the same breadth as the bars. Shell +very thick walled; surface smooth, honeycomb-like. Polar spines conical, +smooth, about as long as the axis of the shell, twice as broad at the base +as one pore. + +_Dimensions._--Diameter of the sphere 0.12 to 0.13, pores and bars 0.005; +thickness of the shell wall 0.013; length of the polar spines 0.12 to 0.15, +basal breadth 0.01. + +_Habitat._--Pacific, central area, Station 272, depth 2600 fathoms. + + +4. _Xiphosphaera luna_, n. sp. + +Pores regular, circular, hexagonally lobed or rosette-shaped, three times +as broad as the bars. Ten to twelve pores on the half equator. Shell thick +walled; surface smooth. Polar spines three-sided pyramidal, one to two +times as long as the axis of the shell, as broad at the base as one pore +{124}(very similar to _Xiphostylus phasianus_, Pl. 13, fig. 9, but +different in the equal size and similar form of the two large polar +spines). + +_Dimensions._--Diameter of the sphere 0.12, pores 0.015, bars 0.005; length +of the polar spines 0.1 to 0.2, basal breadth 0.02. + +_Habitat._--Indian Ocean, Cocos Islands, surface, Rabbe. + + +5. _Xiphosphaera hebe_, n. sp. + +Pores regular, circular, three times as broad as the bars. On the half +equator sixteen to twenty pores. Shell thick walled; surface smooth. Polar +spines conical or nearly cylindrical, about as long as the axis of the +sphere, as broad at the base as two pores. + +_Dimensions._--Diameter of the sphere 0.1 to 0.13, pores 0.006, bars 0.002; +polar spines 0.1 to 0.15 long, 0.01 thick. + +_Habitat._--Pacific, central area, Stations 265 to 268, depths 2700 to 2900 +fathoms. + + +6. _Xiphosphaera maxima_, n. sp. + +Pores regular, circular, twice as broad as the bars, funnel-shaped. Twenty +to thirty pores on the half equator. Shell very thick walled; surface +smooth. Polar spines three-sided pyramidal, about as long as the radius of +the sphere, as broad at the base as two pores. + +_Dimensions._--Diameter of the sphere 0.22 to 0.35, pores 0.008 to 0.01, +bars 0.005; polar spines 0.1 to 0.15 long, 0.02 thick. + +_Habitat._--Equatorial Atlantic, Station 347, depth 2250 fathoms. + + +7. _Xiphosphaera euphrosyne_, n. sp. + +Pores regular, circular, about as broad as the bars, double contoured. +Eight to ten on the half equator. Shell thin walled; surface smooth. Polar +spines conical, about as long as the radius of the sphere, as broad at the +base as one pore. + +_Dimensions._--Diameter of the sphere 0.12 to 0.15, pores and bars 0.02; +polar spines 0.06 to 0.09 long, 0.02 thick. + +_Habitat._--South Atlantic, Station 323, depth 1900 fathoms. + + + +Subgenus 2. _Xiphosphaerella_, Haeckel. + +_Definition._--Pores of the spherical shell regular, of nearly equal size +and form; surface thorny or spiny, covered with regularly distributed +papillae or thorns (in addition to the two large polar spines). + + +8. _Xiphosphaera pallas_, n. sp. (Pl. 14, fig. 4). + +Pores regular, circular, separated by hexagonal elevated frames, the sharp +crest of which is elegantly denticulated; in each corner of the hexagons +(between three pores) is a short radial spine, {125}about as long as one +pore. On the half equator sixteen to twenty pores, of the same breadth as +the bars. Shell thick walled; whole surface spiny. Polar spines +cylindrical, at the apex conical, about as long as the axis of the sphere, +three to four times as broad as one pore. + +_Dimensions._--Diameter of the sphere 0.1, pores and bars 0.005; length of +the polar spines 0.07 to 0.11, thickness 0.015 to 0.02. + +_Habitat._--Western Tropical Pacific, Station 225, depth 4475 fathoms. + + +9. _Xiphosphaera flora_, n. sp. + +Pores regular, circular, with hexagonal frames, twice as broad as the bars. +Ten to twelve pores on the half equator. Shell thin walled, with spiny +surface; in each corner of the hexagons is one bristle-like radial spine +twice as long as one pore. Polar spines three-sided prismatic, at the apex +pyramidal, nearly twice as long as the axis of the sphere, as broad at the +base as two pores (similar to _Ellipsoxiphus palliatus_, Pl. 14, fig. 7). + +_Dimensions._--Diameter of the sphere 0.15, pores 0.01, bars 0.005; length +of the polar spines 0.2 to 0.25, breadth 0.02. + +_Habitat._--Tropical Atlantic, Station 342, depth 1445 fathoms. + + +10. _Xiphosphaera juno_, n. sp. + +Pores regular, circular, as broad as the bars, funnel-shaped. Fifteen to +twenty pores on the half equator. Shell thick walled, covered with +bristle-like spines, about twice as long as one pore. Polar spines conical, +thick, about as long as the axis of the sphere, twice as broad at the base +as one pore. + +_Dimensions._--Diameter of the sphere 0.12, pores and bars 0.01; length of +the polar spines 0.14, basal breadth 0.02. + +_Habitat._--Fossil in the Barbados rocks; living in the greatest depth of +the Tropical Pacific, Station 225, depth 4475. + + +11. _Xiphosphaera gigantea_, n. sp. + +Pores regular, circular, two to three times as broad as the bars; +twenty-eight to thirty-two on the half equator. Shell thick walled, covered +with short conical thorns. Polar spines three-sided pyramidal, about as +long as the radius of the sphere, as broad at the base as three pores. + +_Dimensions._--Diameter of the sphere 0.25 to 0.3, pores 0.01, bars 0.004; +polar spines 0.1 to 0.15 long, 0.03 broad. + +_Habitat._--Fossil in the Tertiary rocks of Barbados and Sicily +(Cattanisetta). + + + +Subgenus 3. _Xiphosphaerissa_, Haeckel. + +_Definition._--Pores of the spherical shell irregular, of different size or +form; surface smooth or a little rough, without spines or thorns (other +than the polar spines). + + +{126}12. _Xiphosphaera ceres_, n. sp. + +Pores irregular, roundish, of different sizes, two to four times as broad +as the bars. Sixteen to twenty pores on the half equator. Shell thin +walled, with smooth surface. Polar spines conical, about as long as the +axis of the sphere, very thick at the base. + +_Dimensions._--Diameter of the sphere 0.15 to 0.2, pores 0.004 to 0.008, +bars 0.002; polar spines 0.18 to 0.24 long, at the base 0.02 thick. + +_Habitat._--North Atlantic, Station 353, surface. + + +13. _Xiphosphaera clavigera_, n. sp. + +Pores irregular, roundish, double contoured, of very unequal size, two to +seven times as broad as the bars; ten to twelve on the half equator. Shell +thick walled; surface a little rough. Polar spines club-shaped, with +prominent edges, about half as long as the axis of the sphere; thinner at +both ends than in the middle. (Differs from _Ellipsoxiphus claviger_, Pl. +14, fig. 3, in the spherical shell and shorter spines.) + +_Dimensions._--Diameter of the sphere 0.2, pores 0.005 to 0.02, bars 0.003; +polar spines 0.06 long, 0.02 broad. + +_Habitat._--Pacific, central area, Station 274, depth 2750 fathoms. + + + +Subgenus 4. _Xiphosphaeromma_, Haeckel. + +_Definition._--Pores of the spherical shell irregular, of different size or +form; surface thorny or spiny (besides the two large polar spines). + + +14. _Xiphosphaera vesta_ n. sp. (Pl. 14, fig. 6). + +Pores irregular, roundish, three to five times as broad as the bars; +fourteen to sixteen on the half equator. Scattered on the surface of the +thick-walled shell are from twenty to thirty strong three-sided pyramidal +spines of unequal size, the largest twice as long as the largest pores. +Polar spines very strong, nearly three-sided prismatic, with curved edges, +nearly as long as the axis of the sphere and twice as broad as the largest +pores. + +_Dimensions._--Diameter of the sphere 0.17, pores 0.01 to 0.02, bars 0.004; +length of the polar spines 0.13, thickness 0.02 to 0.03. + +_Habitat._--Pacific, central area. Station 266, depth 2750 fathoms, + + +15. _Xiphosphaera astraea_, n. sp. + +Pores irregular, roundish, one to two times as broad as the bars; ten to +twelve on the half equator. Surface of the thick-walled shell covered with +numerous short conical thorns. Polar spines cylindro-conical, one and a +half to two times as long as the axis of the sphere. + +{127}_Dimensions._--Diameter of the sphere 0.18, pores 0.01 to 0.015, bars +0.008; length of the polar spines 0.25 to 0.3, thickness 0.02. + +_Habitat._--Indian Ocean, surface; Ceylon, Haeckel. + + + +Genus 46. _Xiphostylus_,[69] Haeckel, 1881, Prodromus, p. 450. + +_Definition._--#Stylosphaerida# with one single lattice-sphere and two free +spines of different size or form. + +The genus _Xiphostylus_ differs from the foregoing _Xiphosphaera_ in the +unequal size or form of both polar spines, which become more or less +differentiated. + + + +Subgenus 1. _Xiphostylantha_, Haeckel. + +_Definition._--Pores of the spherical shell regular, of nearly equal size +and form; surface smooth or a little rough, without spines or thorns. + + +1. _Xiphostylus alcedo_, n. sp. (Pl. 13, fig. 4). + +Pores regular, circular, with elevated hexagonal frames, twice as broad as +the bars. Eight to ten pores on the half equator. Surface smooth. Polar +spines three-sided pyramidal, as broad at the base as one hexagon; the +major spine four to five times as long as the minor, which is about equal +to the radius of the sphere. + +_Dimensions._--Diameter of the sphere 0.12, pores 0.012, bars 0.006; length +of the major polar spine 0.16 to 0.2, of the minor 0.04 to 0.06, basal +breadth 0.02. + +_Habitat._--Western Tropical Pacific, Station 225, depth 4475. + + +2. _Xiphostylus phasianus_, n. sp. (Pl. 13, fig. 9). + +Pores regular, circular, twice as broad as the bars. Eight to ten pores on +the half equator. Outer opening of each pore elegantly lobed, with eight +indentations. Surface a little rough. Polar spines very unequal; major +spine sword-like, sharply edged, about as long as the diameter of the +sphere; minor spine scarcely half so long, pommel-shaped, with nine (?) +wing-like edges. + +_Dimensions._--Diameter of the sphere 0.13, inner circular opening of the +pores 0.01, outer eight-lobed opening 0.015, bars 0.005; length of the +major polar spine 0.14, of the minor 0.06, breadth 0.03. + +_Habitat._--Australian Sea, Station 162, surface. + + +3. _Xiphostylus motacilla_, n. sp. + +Pores regular, circular, three times as broad as the bars; sixteen to +twenty on the half equator. Surface smooth. Polar spines compressed, +two-edged, at the base three to four times as broad as {128}one pore; the +major spine somewhat longer than the diameter of the shell, the minor +scarcely one-third or one-half as long. + +_Dimensions._--Diameter of the sphere 0.14, pores 0.006, bars 0.002; length +of the major spine 0.16 to 0.18, of the minor 0.05 to 0.07, basal breadth +0.02. + +_Habitat._--Indian Ocean, Zanzibar, 2200 fathoms, Pullen. + + +4. _Xiphostylus gallus_, n. sp. + +Pores regular, circular, five times as broad as the bars. Twelve to sixteen +pores on the half equator. Surface smooth. Polar spines very unequal; the +major conical spine one and a half to three times as long as the diameter +of the sphere; the minor pommel-shaped, scarcely one-third as long (length +of both spines very variable). + +_Dimensions._--Diameter of the sphere 0.13, pores 0.01, bars 0.002; length +of the major spine 0.2 to 0.4, of the minor 0.05 to 0.08. + +_Habitat._--Pacific, central area, Station 268, depth 2900 fathoms. + + +5. _Xiphostylus alauda_, n. sp. (Pl. 14, fig. 15). + + _Lithomespilus alauda_, Haeckel, 1881, Prodrom. et Atlas, _loc. cit._ + +Pores subregular, circular, three to four times as broad as the bars; +fifteen to eighteen on the half equator. Surface a little rough. Polar +spines irregularly conical or pyramidal, scarcely as long as the radius of +the sphere; one spine simple, the other composed of a bunch of four or five +spines united at the base. + +_Dimensions._--Diameter of the sphere 0.11, pores 0.01, bars 0.003; length +of the polar spines 0.03 to 0.05, basal breadth 0.02. + +_Habitat._--Pacific, central area, Station 272, depth 2600 fathoms. + + +6. _Xiphostylus anhinga_, Haeckel. + + _Rhabdolithis pipa_, Bury, 1862, Polycystins of Barbados, pl. iii. fig. + 4. + +Pores subregular, circular, about the same breadth as the bars; eight to +ten on the half equator. Surface smooth or a little rough. Polar spines +cylindrical, very irregularly curved like S or contorted, the major three +to six times as long as the diameter of the sphere, the minor scarcely +one-fourth as long as the former, at the end truncated. + +_Dimensions._--Diameter of the sphere 0.07, pores and bars 0.005; length of +the major polar spine 0.2 to 0.4, of the minor 0.06 to 0.09, basal breadth +0.01. + +_Habitat._--Fossil in the Barbados rocks. + + + +Subgenus 2. _Xiphostyletta_, Haeckel. + +_Definition._--Pores of the spherical shell regular, of nearly equal size +and form; surface thorny or spiny (other than the two large polar spines). + + +{129}7. _Xiphostylus cuculus_, n. sp. + +Pores regular, circular, hexagonally framed, three times as broad as the +bars; ten to twelve on the half equator. Surface thorny, between every +three pores a short conical thorn. Polar spines three-sided prismatic, the +major somewhat longer than the diameter of the sphere, the minor scarcely +one-third as long, pommel-shaped. + +_Dimensions._--Diameter of the sphere 0.17, pores 0.012, bars 0.004; length +of the major polar spine 0.2, of the minor 0.05, basal breadth 0.015. + +_Habitat._--South Atlantic, surface; Station 335, depth 1425 fathoms. + + +8. _Xiphostylus trochilus_, n. sp. (Pl. 13, fig. 10). + +Pores regular, circular, four times as broad as the bars; eight to nine on +the half equator. Polar spines cylindrical, the major somewhat longer than +the axis of the sphere, the minor shorter, surrounded by a group of from +four to eight shorter conical spines. Surface of the opposite hemisphere +smooth, without by-spines. + +_Dimensions._--Diameter of the sphere 0.07 to 0.08, pores 0.01, bars +0.0025. + +_Habitat._--North Pacific, Station 244, depth 2900 fathoms. + + +9. _Xiphostylus picus_, n. sp. (Pl. 14, fig. 13). + + _Lithomespilus picus_, Haeckel, 1881, Prodrom. et Atlas. + +Pores regular, circular, twice as broad as the bars; sixteen to eighteen on +the half equator. Polar spines cylindrical, conical at the apex, the major +once and a half to twice as long as the diameter of the shell, the minor +scarcely half so long; around the latter a group of twelve to twenty +shorter conical spines, irregularly scattered. Surface of the other +hemisphere smooth. + +_Dimensions._--Diameter of the sphere 0.13, pores 0.006, bars 0.003; length +of the major polar spine 0.2 to 0.24, of the minor 0.08 to 0.09, basal +breadth 0.02. + +_Habitat._--Central Pacific, Station 265, depth 2900 fathoms. + + + +Subgenus 3. _Xiphostylissa_, Haeckel. + +_Definition._--Pores of the spherical shell irregular, of unequal size or +form; surface smooth or a little rough, without thorns. + + +10. _Xiphostylus trogon_, n. sp. (Pl. 14, fig. 12). + + _Lithomespilus trogon_, Haeckel, 1881, Prodrom. et Atlas. + +Pores irregular, roundish or subcircular, two to three times as broad as +the bars; ten to twelve on the half equator. Surface smooth. Major polar +spine three-sided prismatic, once and a half to twice as long as the axis +of the sphere; minor spine quite rudimentary, scarcely longer than broad, +but surrounded by a group of from three to six similar short spines. + +{130}_Dimensions._--Diameter of the sphere 0.1, pores 0.005 to 0.015, bars +0.005 to 0.008; length of the major spine 0.15 to 0.18, of the minor 0.01 +to 0.02, basal breadth 0.02. + +_Habitat._--Western Tropical Pacific, Station 225, depth 4475 fathoms. + + +11. _Xiphostylus falco_, n. sp. (Pl. 13, fig. 14). + +Pores irregular, roundish, two to five times as broad as the bars; sixteen +to eighteen on the half equator. Surface smooth. Polar spines cylindrical, +very stout, nearly half as thick as the radius of the shell; major spine +two to four times as long as the diameter of the shell; minor spine +obliquely inserted, scarcely longer than the diameter, divided at the end +into two short, hook-shaped, curved branches. + +_Dimensions._--Diameter of the sphere 0.08, pores 0.002 to 0.005, bars +0.001; breadth of the spines 0.02, length of the major spine 0.15 to 0.2, +of the minor 0.09. + +_Habitat._--South Pacific, Station 302, depth 1450 fathoms. + + +12. _Xiphostylus alca_, n. sp. (Pl. 13, fig. 13). + +Pores irregular, roundish, two to six times as broad as the bars; six to +eight on the half equator. Each pore with three to six lobes, composed of +three to six confluent smaller pores. Surface smooth. Major spine conical, +curved, somewhat longer than the axis of the sphere; minor spine somewhat +shorter, pommel-like, edged. + +_Dimensions._--Diameter of the sphere 0.07, pores 0.01 to 0.02, bars 0.003; +length of the major spine 0.08, of the minor 0.06, basal thickness 0.02. + +_Habitat._--Indian Ocean, Sunda Strait, Rabbe, surface. + + +13. _Xiphostylus edolius_, n. sp. (Pl. 13, fig. 5). + +Pores irregular, roundish, composed of two to six smaller confluent pores. +On the half equator six to eight large pores, and twenty to thirty small +pores; bars between the smaller very thin. Surface a little rough. Major +polar spine conical, S-shaped, about twice as long as the axis of the +shell; minor spine pommel-shaped, edged, scarcely as long as its radius. + +_Dimensions._--Diameter of the sphere 0.12, large pores 0.01 to 0.03, small +pores 0.004 to 0.008, bars 0.001 to 0.004; length of the major spine 0.2, +of the minor 0.05, basal breadth 0.02. + +_Habitat._--Central Pacific, Station 273, surface. + + + +Subgenus 4. _Xiphostylomma_, Haeckel. + +_Definition._--Pores of the spherical shell irregular, of different size or +form; surface thorny or spiny. + + +{131}14. _Xiphostylus emberiza_, n. sp. (Pl. 13, fig. 11). + +Pores irregular, roundish, one to four times as broad as the bars; six to +eight on the half equator. Polar spines very unequal; major cylindrical, +twice as long as the axis of the sphere; minor scarcely half as long, +obliquely inserted, like a bird's head, surrounded by a group of ten to +twenty smaller conical spines. Opposite hemisphere smooth. + +_Dimensions._--Diameter of the sphere 0.005, pores 0.002 to 0.008, bars +0.002; length of the major spine 0.09, of the minor 0.05, basal breadth +0.01. + +_Habitat._--South Atlantic, Station 332, surface. + + +15. _Xiphostylus ardea_, n. sp. + +Pores irregular, roundish, one to three times as broad as the bars; twelve +to sixteen on the half equator. Whole surface spiny. Major polar spine +three-sided pyramidal, somewhat longer than the diameter of the sphere; +minor scarcely so long as its half radius, pommel-like, edged. + +_Dimensions._--Diameter of the sphere 0.12, pores 0.003 to 0.01, bars +0.003; length of the major polar spine 0.15, of the minor 0.03, basal +breadth 0.02. + +_Habitat._--North Atlantic, Station 64, surface. + + + +Genus 47. _Saturnalis_,[70] Haeckel, 1881, Prodromus, p. 450. + +_Definition._--#Stylosphaerida# with one single lattice-sphere and two +equal opposite spines, connected at the distal end by a circular or +elliptical ring. + +The genus _Saturnalis_ (with simple lattice-sphere) and the two similar +genera _Saturnulus_ (with two concentric spheres) and _Saturninus_ (with +three spheres) form together the small peculiar group of Saturnalida, +distinguished by a remarkable circular or elliptical ring, connecting the +distal ends of the two equal opposite polar spines. This ring indicates a +certain equatorial plane, and therefore brings these #Sphaeroidea# into +relation with the #Discoidea#. + + + +Subgenus 1. _Saturnalina_, Haeckel. + +_Definition._--Ring smooth, without spines or thorns. + + +1. _Saturnalis circularis_, n. sp. + +Pores of the spherical shell regular, circular, hexagonally framed, twice +as broad as the bars. Ten to twelve pores on the half equator. Ring +circular, smooth, its diameter three times as great as that of the sphere. + +{132}_Dimensions._--Diameter of the sphere 0.07, pores 0.005, bars 0.0025; +diameter of the circular ring 0.2, thickness of the axial beams and the +ring 0.01. + +_Habitat._--South Atlantic, Station 332, depth 2200 fathoms. + + +2. _Saturnalis annularis_, n. sp. (Pl. 13, fig. 16). + +Pores of the spherical shell regular, circular, with elevated hexagonal +frames, of the same breadth as the bars. Sixteen to twenty pores on the +half equator. Ring elliptical, smooth, somewhat constricted at the poles of +the axis, its diameter three times as great as that of the sphere. + +_Dimensions._--Diameter of the sphere 0.09, pores and bars 0.005, major +axis of the elliptical ring 0.27 to 0.3, minor axis 0.19 to 0.2; thickness +of the ring and of the axial beams 0.01. + +_Habitat._--Pacific, central area, Stations 270 to 274, surface. + + +3. _Saturnalis cyclus_, n. sp. + + _Lithocircus mesocena_, Bury, 1862, Polycystins of Barbados, pl. iii. + fig. 1. + +Pores of the spherical shell regular, circular, without hexagonal frames, +twice as broad as the bars. Eight to ten pores on the half equator. Ring +circular, smooth, its diameter four times as great as that of the sphere. + +_Dimensions._--Diameter of the sphere 0.07, pores 0.006, bars 0.003; +diameter of the circular ring 0.28, thickness of the ring and both axial +beams 0.01. + +_Habitat._--Fossil in the Barbados rocks. + + +4. _Saturnalis circoides_, n. sp. (Pl. 13, fig. 12). + +Pores of the spherical shell irregular, roundish, often somewhat lobed, one +to three times as broad as the bars; fifteen to twenty on the half equator. +Ring circular, smooth, with four prominent edges, its diameter twice as +great as that of the sphere. (The figured specimen is a young or not fully +developed one; afterwards I found in the same locality other specimens with +quite perfect rings, similar to the edged ring of _Saturnulus annulus_, Pl. +16, fig. 17.) + +_Dimensions._--Diameter of the sphere 0.09 to 0.1, pores 0.003 to 0.01, +bars 0.004; diameter of the circular ring 0.2 to 0.24, thickness of the +ring and the polar beams 0.01. + +_Habitat._--Indian Ocean; fossil in the Nicobar rocks; living at great +depths near Zanzibar, 2200 fathoms, Pullen. + + + +Subgenus 2. _Saturnalium_, Haeckel. + +_Definition._--Ring armed on the periphery with numerous spines or thorns. + + +5. _Saturnalis trochoides_, n. sp. + + _Haliomma_ species, Bury, 1862, Polycystins of Barbados, pl. xx. fig. 2. + +Pores of the spherical shell subregular, circular, twice as broad as the +bars. Twelve to sixteen pores on the half equator. Ring circular, armed +with ten to twelve strong conical, irregular spines, its diameter twice as +great as that of the sphere. + +{133}_Dimensions._--Diameter of the sphere 0.08, pores 0.006, bars 0.003; +diameter of the circular ring 0.16; length of the radial spines 0.02 to +0.04; thickness of the ring and the axial beams 0.01. + +_Habitat._--Fossil in the Barbados rocks. + + +6. _Saturnalis rotula_, n. sp. (Pl. 13, fig. 15). + +Pores of the spherical shell regular, circular, twice as broad as the bars; +sixteen to twenty on the half equator. Ring circular, armed with fifteen to +twenty strong, conical, irregular spines, partly simple, partly divided +into two or three irregular branches; diameter of the ring two and a half +times as great as that of the sphere. + +_Dimensions._--Diameter of the sphere 0.08, pores 0.004, bars 0.002; +diameter of the circular ring 0.2, length of its spines 0.02 to 0.03; +thickness of the ring and the radial beams 0.01. + +_Habitat._--North Pacific, Station 244, surface. + + + +Subfamily SPHAEROSTYLIDA, Haeckel, 1881, Prodromus, pp. 449, 451. + +_Definition._--#Stylosphaerida# with two concentric, spherical +lattice-shells. + + + +Genus 48. _Stylosphaera_,[71] Ehrenberg, 1847, Monatsber. d. Berlin Akad., +p. 54. + +_Definition._--#Stylosphaerida# with two concentric lattice-spheres and two +free spines of equal size and similar form. + +The genus _Stylosphaera_, the most simple form of the Sphaerostylida, can +be derived either from _Xiphosphaera_ by duplication of the spherical +shell, or from _Carposphaera_ by development of two opposite polar spines. +The inner or medullary shell is enclosed in the central capsule, whilst the +outer or cortical shell lies outside it; the two are connected by two or +more radial beams, piercing the wall of the capsule. + + + +Subgenus 1. _Stylosphaerantha_, Haeckel. + +_Definition._--Pores of the cortical shell regular, of nearly equal size +and similar form; surface smooth or a little rough, without spines or +thorns. + + +1. _Stylosphaera musa_, n. sp. + +Radial proportion of the two concentric spheres = 3 : 1. Cortical shell +thin walled, smooth, with regular, hexagonal pores, three times as broad as +the thin bars; twelve on the half equator. Polar spines three-sided +pyramidal, as long as the axis of the cortical shell, one-tenth as broad at +the base. + +_Dimensions._--Diameter of the outer shell 0.2, pores 0.01, bars 0.003; +diameter of the inner shell 0.06; length of the polar spines 0.2, basal +breadth 0.02. + +_Habitat._--Tropical Atlantic, Station 347, depth 2250 fathoms. + + +{134}2. _Stylosphaera urania_, n. sp. + +Radial proportion of the two shells = 4 : 1. Cortical shell thin walled, +smooth; pores regular, circular, hexagonally framed, twice as broad as the +bars; ten on the half equator. Polar spines conical, as long as the radius +of the outer shell. + +_Dimensions._--Diameter of the cortical shell 0.24, pores 0.012, bars +0.006; medullary shell 0.06; length of the polar spines 0.12, basal breadth +0.024. + +_Habitat._--South Pacific, Station 285, depth 2375 fathoms. + + +3. _Stylosphaera calliope_, n. sp. (Pl. 16, fig. 6). + +Radial proportion of the two shells = 3 : 1. Cortical shell thick walled, +smooth; pores regular, circular, three times as broad as the bars. Each +pore on its outer opening with eight regular lobules, flower-like. Nine to +ten pores on the half equator. Polar spines three-sided pyramidal, with +three strong prominent edges, about as long as the axis, as broad as one +pore. (Sometimes, as in the figured specimen, one spine is smaller than the +other; this variety, otherwise identical, may be called _Sphaerostylus +calliope_.) + +_Dimensions._--Diameter of the outer shell 0.12, pores 0.015, bars 0.005; +inner shell 0.04; length of the polar spine 0.08 to 0.12, breadth 0.02. + +_Habitat._--Pacific, central area, Station 268, depth 2900 fathoms. + + +4. _Stylosphaera clio_, n. sp. (Pl. 16, fig. 7). + +Radial proportion of the two shells = 2 : 1. Cortical shell thick walled, +smooth; pores regular, circular, three times as broad as the bars; fourteen +to sixteen on the half equator. Polar spines three-sided pyramidal, very +robust, with thick prismatic edges, about as long as the axis of the +cortical shell, one-third as broad at the base. (Sometimes, as in the +figured specimen, one spine is greater than the other; this form may be +called _Sphaerostylus clio_.) + +_Dimensions._--Diameter of the outer shell 0.12, pores 0.01, bars 0.003; +inner shell 0.06; length of the polar spines 0.08 to 0.12, basal breadth +0.03 to 0.04. + +_Habitat._--Pacific, central area; Station 272, depth 2600 fathoms. + + +5. _Stylosphaera polyhymnia_, n. sp. + +Radial proportion of the two spheres = 3 : 1. Cortical shell very thin +walled, smooth, with regular, circular pores, three times as broad as the +bars; sixteen to twenty on the half equator. Polar spines cylindrical, +pointed, once and a half to twice as long as the axis of the outer sphere, +scarcely broader than one pore. The two spheres are connected only by the +two opposite beams. + +_Dimensions._--Diameter of the outer shell 0.12 to 0.16, pores 0.006 to +0.009, bars 0.002 to 0.003; inner shell 0.04 to 0.05; length of the polar +spines 0.18 to 0.22, breadth 0.01. + +_Habitat._--Cosmopolitan; Mediterranean, Atlantic, Indian, Pacific, +surface. + + +{135}6. _Stylosphaera dixyphos_, Haeckel. + + _Haliomma dixyphos_, Ehrenberg, 1854, Monatsber. d. k. preuss. Akad. d. + Wiss. Berlin, p. 83; Mikrogeol., Taf. xxii. fig. 31. + + _Haliomma dixyphos_, Haeckel, 1862, Monogr. d. Radiol. p. 433. + +Radial proportion of the two spheres = 2 : 1. Cortical shell thin walled, +smooth, with regular, circular pores, twice as broad as the bars; ten to +twelve on the half equator. Polar spines about as long as the axis of the +outer shell, three-sided pyramidal, at the base twice as broad as one pore. +(The two spheres connected by four beams, two opposite in the main axis, +two opposite in the equatorial axis.) + +_Dimensions._--Diameter of the outer shell 0.1, pores 0.01, bars 0.05; +inner shell 0.05; length of the polar spines 0.08 to 0.1, basal breadth +0.02. + +_Habitat._--South Atlantic, Station 332, surface; fossil in Tertiary rocks +of Sicily. + + + +Subgenus 2. _Stylosphaerella_, Haeckel. + +_Definition._--Pores of the cortical shell regular, of nearly equal size +and similar form; surface thorny or spiny. + + +7. _Stylosphaera setosa_, Ehrenberg, 1872. + + _Stylosphaera setosa_, Ehrenberg, 1872, Monatsber. d. k. preuss. Akad. d. + Wiss. Berlin, p. 320; Abhandl. d. k. Akad. d. Wiss. Berlin, Taf. viii. + fig. 15. + +Radial proportion of the two shells = 2 : 1. Cortical shell thin walled, +spiny; pores regular, hexagonal, four times as broad as the bars. Six to +eight pores on the half equator. Polar spines conical, thin, scarcely as +long as the radius of the cortical shell. + +_Dimensions._--Diameter of the cortical shell 0.1, pores 0.002, bars 0.005; +medullary shell 0.05; length of the polar spines 0.04, basal breadth 0.01. + +_Habitat._--Philippine Sea, depth 3300 fathoms, Ehrenberg; Station 206, +depth 2100 fathoms. + + +8. _Stylosphaera euterpe_, n. sp. + +Radial proportion of the two shells = 3 : 1. Cortical shell thin walled, +spiny; pores regular, circular, with hexagonal frames, twice as broad as +the bars; eight to ten on the half equator. Polar spines conical, as thick +as one pore at the base, about as long as the axis of the cortical shell. + +_Dimensions._--Diameter of the cortical shell 0.12, pores 0.012, bars +0.006; medullary shell 0.04; length of the polar spines 0.1, basal breadth +0.012. + +_Habitat._--South Pacific, Station 302, depth 1450 fathoms. + + +9. _Stylosphaera melpomene_, n. sp. (Pl. 16, fig. 1). + +Radial proportion of the two shells = 3 : 1. Cortical shell thin walled, +spiny, with regular, circular pores, four times as broad as the bars; eight +to ten on the half equator. Polar spines three-sided prismatic, pointed, as +broad as one pore, only one-third as long as the axis of the sphere (the +two shells connected by four thin beams, two opposite in the main axis, two +in the equatorial axis). + +{136}_Dimensions._--Diameter of the outer shell 0.12, pores 0.012, bars +0.003; inner shell 0.04; length of the polar spines 0.04, thickness 0.013. + +_Habitat._--Indian Ocean, Cocos Islands, Rabbe. + + +10. _Stylosphaera hispida_, Ehrenberg, 1854. + + _Stylosphaera hispida_, Ehrenberg, 1854, Monatsber. d. k. preuss. Akad. + d. Wiss. Berlin, p. 246; Mikrogeol, Taf. xxxvi. fig. 26. + + _Haliomma hispidum_, Haeckel, 1862, Monogr. d. Radiol., p. 433. + +Radial proportion of the two spheres = 3 : 1. Cortical shell thick walled, +spiny, with regular, circular pores of the same breadth as the bars; ten to +fifteen on the half equator. Polar spines three-sided prismatic, pointed, +about as long as the axis of the outer sphere, nearly as broad at the base +as the inner sphere. (Compare _Sphaerostylus hispidus_; also Ehrenberg, +Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, 1874, p. 259.) + +_Dimensions._--Diameter of the outer shell 0.1 to 0.12, pores and bars +0.004; inner shell 0.04; length of the polar spines 0.1 to 0.15, basal +breadth 0.03. + +_Habitat._--Fossil in the Tertiary rocks of Sicily, Barbados, Nicobars, &c. + + +11. _Stylosphaera liostylus_, Ehrenberg, 1875. + + _Stylosphaera liostylus_, Ehrenberg, Abhandl. d. k. Akad. d. Wiss. + Berlin, p. 84, Taf. xxv. fig. 3. + +Radial proportion of the two spheres = 3 : 1. Cortical shell thick walled, +thorny, with regular, circular pores, three times as broad as the bars; +eight to ten on the half equator. Polar spines conical, once and a half to +twice as long as the axis of the outer sphere, half as broad at the base as +its radius. (This species, common in the Barbados rocks, is different from +_Sphaerostylus liostylus_, _loc. cit._, fig. 2, which Ehrenberg believed +identical.) + +_Dimensions._--Diameter of the outer shell 0.1, pores 0.01, bars 0.0035; +inner shell 0.03; length of the polar spines 0.14 to 0.18, basal breadth +0.02. + +_Habitat._--Fossil in the Barbados rocks; living in the depths of the North +Atlantic, Gulf Stream, Florida. + + + +Subgenus 3. _Stylosphaerissa_, Haeckel. + +_Definition._--Pores of the cortical shell irregular, of different size or +form; surface smooth or a little rough, without thorns or spines. + + +12. _Stylosphaera nana_, n. sp. (Pl. 16, figs. 12, 13). + +Radial proportion of the two spheres = 2 : 1. Cortical shell thick walled, +somewhat irregular, smooth, with irregular, roundish pores, one to three +times as broad as the bars; eight to ten on the half equator. Polar spines +three-sided pyramidal, scarcely as long as the axis of the outer sphere, +and nearly as broad at the base as its radius. (A very variable and +irregular form.) + +_Dimensions._--Diameter of the outer shell 0.07 to 0.09, pores 0.003 to +0.009, bars 0.003; inner shell 0.03 to 0.04; length of the polar spines +0.04 to 0.07, basal breadth 0.03. + +_Habitat._--North Pacific, Stations 241 to 253, surface. + + +{137}13. _Stylosphaera jugata_, n. sp. + +Radial proportion of the two shells = 2 : 1. Cortical shell thick walled, +smooth, with irregular, roundish, double-contoured pores, confluent in +groups of two to six. On the half equator six to nine groups and fifteen to +twenty pores; bars between them of very variable breadth. Polar spines very +strong, three-sided pyramidal, twice as long as the axis of the outer +sphere, half as broad at the base as its radius. (Nearly allied to +_Lithatractus jugatus_, Pl. 16, fig. 2, but differs in the truly spherical +form of both shells and the double length of the polar spines.) + +_Dimensions._--Diameter of the outer shell 0.15, pores 0.005 to 0.02; inner +shell 0.07; length of the polar spines 0.25 to 0.3, basal breadth 0.03. + +_Habitat._--Western Tropical Pacific, Station 224, depth 1850 fathoms. + + +14. _Stylosphaera terpsichore_, n. sp. + +Radial proportion of the two shells = 3 : 1 or 4 : 1. Cortical shell thick +walled, smooth, with irregular, roundish pores, one to three times as broad +as the bars; fifteen to twenty-five on the half equator. Polar spines +conical, about as long as the axis of the outer sphere, as broad at the +base as the inner shell. + +_Dimensions._--Diameter of the outer shell 0.15 to 0.2, pores 0.005 to +0.02, bars 0.004 to 0.008; inner shell 0.05; length of the polar spines +0.15 to 0.25, basal breadth 0.05. + +_Habitat._--Western Indian Ocean, Zanzibar, depth 2200 fathoms, Pullen. + + + +Subgenus 4. _Stylosphaeromma_, Haeckel. + +_Definition._--Pores of the cortical shell irregular, of different size or +form; surface spiny or thorny. + + +15. _Stylosphaera thalia_, n. sp. + +Radial proportion of the two shells = 2 : 1. Cortical shell thin walled, +thorny, with irregular, roundish pores, two to four times as broad as the +bars; eight to twelve on the half equator. Polar spines conical, one to one +and a half times as long as the axis of the outer sphere, one-fourth to +one-sixth as thick at the base. (Resembles _Sphaerostylus ophidium_, Pl. +16, fig. 14, but differs in the straight regular conical polar spines, both +of equal length and similar form.) + +_Dimensions._--Diameter of the outer shell 0.12, pores 0.01 to 0.02, bars +0.005; inner shell 0.06; polar spines 0.1 to 0.16 long, 0.03 broad. + +_Habitat._--South Pacific, Station 302, depth 1450 fathoms. + + +16. _Stylosphaera erato_, n. sp. + +Radial proportion of the two shells = 3 : 1. Cortical shell thick walled, +thorny, with irregular, roundish pores, two to five times as broad as the +bars; fourteen to eighteen on the half equator. {138}Polar spines +three-sided pyramidal, about as long as the axis of the outer sphere, +one-fourth as broad as its radius. (Similar to _Xiphosphaera vesta_, Pl. +14, fig. 6.) + +_Dimensions._--Diameter of the outer shell 0.15, pores 0.008 to 0.015, bars +0.003; inner shell 0.05; polar spines 0.12 long, 0.02 broad. + +_Habitat._--South Atlantic, Station 335, depth 1425 fathoms. + + + +Genus 49. _Sphaerostylus_,[72] Haeckel, 1881, Prodromus, p. 451. + +_Definition._--#Stylosphaerida# with two concentric lattice-spheres and two +free spines, of different size or form. + +The genus _Sphaerostylus_ differs from _Stylosphaera_ in the different size +or form of the two polar spines, and therefore has the same relation to it +that _Xiphostylus_ bears to _Xiphosphaera_. + + + +Subgenus 1. _Sphaerostylantha_, Haeckel. + +_Definition._--Pores of the cortical shell regular, of nearly equal size +and similar form; surface smooth or a little rough, without thorns. + + +1. _Sphaerostylus liostylus_, Haeckel. + + _Stylosphaera liostylus_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. + Berlin, Taf. xxv. fig. 2. + +Cortical shell thin walled, with rough surface, three times as broad as the +medullary shell. Pores of the cortical shell regular, circular, twice as +broad as the bars; ten to twelve on the half equator. Polar spines +cylindrical, as broad as one pore, with conical apex; the minor spine about +as long as the axis of the outer shell, the major three to four times as +long. + +_Dimensions._--Diameter of the outer sphere 0.12, pores 0.12, bars 0.006; +diameter of the inner sphere 0.04; length of the major polar spine 0.3 to +0.4, of the minor 0.1 to 0.15, breadth 0.012. + +_Habitat._--Fossil in the Barbados rocks. + + +2. _Sphaerostylus flexuosus_, Haeckel. + + _Stylosphaera flexuosa_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. + Berlin, Taf. xxv. fig. 5. + +Cortical shell thick walled, with rough surface, three times as broad as +the medullary shell. Pores of the cortical shell regular circular, of the +same breadth as the bars; eight to ten on the half equator. Polar spines +cylindrical, S-like curved, irregular; the minor scarcely as long as the +axis of the outer sphere, the major two to three times as long. (In the +figure of Ehrenberg the spines are broken off; I have found them myself +constantly irregular and of unequal length, sometimes with conical apex.) + +{139}_Dimensions._--Diameter of the outer sphere 0.08, pores and bars +0.006; inner sphere 0.03; length of the major polar spine 0.15 to 0.25, of +the minor 0.07 to 0.09, breadth 0.02. + +_Habitat._--Fossil in the Barbados rocks. + + +3. _Sphaerostylus clio_, n. sp. + +Cortical shell thick walled, with smooth surface, twice as broad as the +medullary shell; its network has regular, circular pores, three times as +broad as the bars; sixteen to twenty on the half equator. Polar spines very +strong, three-sided pyramidal; the major nearly twice as long as the axis +of the outer sphere, the minor scarcely as long as its radius. (Nearly +related to _Stylosphaera clio_, Pl. 16, fig. 7, but differs in the slender +form and unequal length of the polar spines.) + +_Dimensions._--Diameter of the outer sphere 0.14, pores 0.01, bars 0.03; +inner sphere 0.07; length of the major spine 0.25, of the minor 0.06, basal +breadth 0.02. + +_Habitat._--Pacific, central area, Station 274, depth 2750 fathoms. + + +4. _Sphaerostylus hippocampus_, n. sp. (Pl. 16, figs. 10, 11). + +Cortical shell thick walled, with smooth surface and regular network; the +pores circular, hexagonally-lobed, three times as broad as the bars; ten to +twelve on the half equator. Medullary shell half as large, with very small +circular pores, eight to ten on the half equator. Major polar spine +scarcely as long as the axis of the outer shell, curved like a horn; minor +spine scarcely half as long, pommel-like, edged. (Sometimes, by +prolongation of the main axis, the spherical shells become ellipsoidal and +thus the species is transformed into _Druppatractus hippocampus_.) + +_Dimensions._--Diameter of the outer sphere 0.08, pores 0.009, bars 0.003; +inner sphere 0.04; length of the major spine 0.07, of the minor 0.03, +breadth 0.02. + +_Habitat._--Pacific, central area, Station 270, depth 2925 fathoms. + + + +Subgenus 2. _Sphaerostyletta_, Haeckel. + +_Definition._--Pores of the cortical shell regular, of nearly equal size +and form; surface spiny or thorny. + + +5. _Sphaerostylus diadema_, n. sp. + +Cortical shell thick walled, spiny, twice as broad as the medullary shell, +with regular, circular pores, twice as broad as the bars; eight to ten on +the half equator. Major polar spine about as long as the axis of the outer +sphere, three-sided pyramidal; minor spine scarcely half as long, +pommel-shaped, edged. (Similar in general form to _Xiphatractus glyptodon_, +Pl. 17, figs. 9, 10; but differs in the simple medullary shell, the +spherical form of both shells, and the simple circular regular pores.) + +{140}_Dimensions._--Diameter of the outer sphere 0.12, pores 0.014, bars +0.007; inner sphere 0.06; length of the major spine 0.13, of the minor +0.05, greatest breadth 0.04. + +_Habitat._--Southern Pacific, surface, Station 289. + + + +Subgenus 3. _Sphaerostylissa_, Haeckel. + +_Definition._--Pores of the cortical shell irregular, of different size or +form; surface smooth or a little rough. + + +6. _Sphaerostylus cottus_, n. sp. + +Cortical shell thick walled, smooth, about twice as broad as the medullary +shell, with irregular, roundish pores, scarcely larger than the bars; +fifteen to twenty on the half equator. Polar spines conical, the major once +and a half to twice as long as the axis of the outer sphere, the minor +scarcely as long as its radius. + +_Dimensions._--Diameter of the outer sphere 0.14, pores and bars 0.008 to +0.012; inner sphere 0.065; length of the major spine 0.2 to 0.3, of the +minor 0.05 to 0.07, basal breadth 0.03. + +_Habitat._--Northern Atlantic, Faeroee Channel, surface, John Murray. + + +7. _Sphaerostylus trigla_, n. sp. + +Cortical shell thin walled, smooth, three times as broad as the medullary +shell, with irregular, roundish pores, two to three times as broad as the +bars; ten to twelve on the half equator. Polar spines very unequal; the +major three-sided pyramidal, one and a half times as long as the axis of +the outer sphere; the minor scarcely as long as its radius, edged, +pommel-like. + +_Dimensions._--Diameter of the outer sphere 0.12, pores 0.01 to 0.015, bars +0.005; inner sphere 0.04; length of the major spine 0.2, of the minor 0.05, +breadth 0.03. + +_Habitat._--Northern Pacific, Station 241, depth 2300 fathoms. + + + +Subgenus 4. _Sphaerostylomma_, Haeckel. + +_Definition._--Pores of the cortical shell irregular, of different size or +form; surface spiny or thorny. + + +8. _Sphaerostylus ophidium_, n. sp. (Pl. 16, figs. 14, 15). + + _Stylosphaera ophidium_, Haeckel, 1878, Atlas, _loc. cit._ + +Cortical shell thin walled, thorny, twice as broad as the medullary shell, +with irregular, roundish pores; eight to ten on the half equator. Polar +spines conical, more or less curved or S-shaped; the minor scarcely as long +as the axis of the outer sphere, the major two to three times as long. + +{141}_Dimensions._--Diameter of the outer sphere 0.11, pores 0.01 to 0.017, +bars 0.003 to 0.007; diameter of the inner sphere 0.06, pores 0.005 to +0.008, bars 0.002 to 0.004; length of the major polar spine 0.25, of the +minor 0.1, basal breadth 0.03. + +_Habitat._--Indian Ocean, Madagascar, Rabbe, surface. + + + +Genus 50. _Saturnulus_,[73] Haeckel, 1881, Prodromus, p. 451. + +_Definition._--#Stylosphaerida# with two concentric lattice-spheres and two +equal opposite spines, the distal ends of which are connected by a circular +or elliptical ring. + +The genus _Saturnulus_ differs from the similar _Saturnalis_ by the +duplication of the spherical lattice-shell; the inner lies within, the +outer without the central capsule. + + +1. _Saturnulus circulus_, n. sp. + +Cortical shell smooth, twice as broad as the medullary shell, with regular, +circular, hexagonally framed pores, of the same breadth as the bars; +fourteen to sixteen on the half equator. Ring circular, smooth, without +edges, its diameter three times as great as that of the sphere. + +_Dimensions._--Diameter of the outer sphere 0.08, pores and bars 0.004; of +the inner sphere 0.04, of the ring 0.24. + +_Habitat._--Central Pacific, Station 272, surface. + + +2. _Saturnulus annulus_, n. sp. + +Cortical shell smooth, three times as broad as the medullary shell, with +regular, circular, hexagonally framed pores, of the same breadth as the +bars; eighteen to twenty on the half equator. Ring elliptical, smooth, +without edges, somewhat constricted at the poles of the minor axis, its +major diameter four times as great as that of the sphere. Differs from +_Saturnalis annularis_, Pl. 13, fig. 16, mainly in the possession of a +medullary shell. + +_Dimensions._--Diameter of the outer sphere 0.1, pores and bars 0.005; +inner sphere 0.033; major axis of the ring 0.4, minor 0.3. + +_Habitat._--North Pacific, Station 244, surface. + + +3. _Saturnulus ellipticus_, n. sp. (Pl. 16, fig. 16). + +Cortical shell smooth, three times as broad as the medullary shell, with +regular, circular pores, three times as broad as the bars; sixteen to +eighteen on the half equator. Ring elliptical, smooth, without edges, its +major diameter three times as great as that of the sphere. + +_Dimensions._--Diameter of the outer sphere 0.09, pores 0.006, bars 0.002; +inner sphere 0.03; major axis of the elliptical ring 0.28, minor 0.24; +thickness of the ring and the axial beams 0.008. + +_Habitat._--South Pacific, Station 300, surface. + + +{142}4. _Saturnulus planetes_, n. sp. (Pl. 16, fig. 17). + +Cortical shell smooth, twice as broad as the medullary shell, with regular, +circular pores, of the same breadth as the bars; sixteen to eighteen on the +half equator. Ring elliptical, smooth, with strong prominent edges, +constricted at the poles of the minor axis, its major diameter three times +as great as that of the outer sphere. + +_Dimensions._--Diameter of the outer sphere 0.08, pores and bars 0.005; +inner sphere 0.035; major axis of the ring 0.25, minor axis 0.2; thickness +of the ring and the axial beams 0.012. + +_Habitat._--Indian Ocean, Sunda Strait, Rabbe; Station 200, surface. + + + +Subfamily AMPHISTYLIDA, Haeckel, 1881, Prodromus, pp. 449, 452. + +_Definition._--#Stylosphaerida# with three concentric spherical +lattice-shells. + + + +Genus 51. _Amphisphaera_, Haeckel,[74] 1881, Prodromus, p. 452. + +_Definition._--#Stylosphaerida# with three concentric lattice-spheres and +two free spines of equal size and similar form. + +The genus _Amphisphaera_ differs from its probable ancestral form, +_Stylosphaera_, in the triple spherical lattice-shell. Commonly two of +these lie within the central capsule (medullary shell), whilst the third +lies outside it (cortical shell). But sometimes this order is inverted, the +cortical shell being double, the medullary shell simple; and perhaps these +forms may better represent a peculiar genus, _Amphisphaeridium_. + + + +Subgenus 1. _Amphisphaerantha_, Haeckel. + +_Definition._--Pores of the cortical shell regular, of nearly equal size +and similar form; surface smooth or a little rough, without spines or +thorns. + + +1. _Amphisphaera neptunus_, n. sp. + +Radial proportion of the three concentric spheres = 4 : 2 : 1. Cortical +shell thick walled, smooth, with regular, circular, hexagonally framed +pores, of the same breadth as the bars; twelve to fifteen on the half +equator. Polar spines three-sided pyramidal, with strong prominent edges, +about as long as the radius of the outer shell, half as broad at the base. +(Similar to _Stylatractus neptunus_, Pl. 17, fig. 6, but differs in the +purely spherical form of the three concentric shells and the regular form +of the network and of the polar spines.) + +_Dimensions._--Diameter of the outer shell 0.16, middle shell 0.08, inner +shell 0.04; pores and bars of the cortical shell 0.008; length of the polar +spines 0.08, basal breadth 0.04. + +_Habitat._--Pacific, central area, Station 271, depth 2425 fathoms. + + +{143}2. _Amphisphaera uranus_, n. sp. + +Radial proportion of the three spheres = 4 : 2 : 1. Cortical shell thick +walled, smooth, with regular, circular pores, three times as broad as the +bars; ten to twelve on the half equator. Polar spines three-sided +pyramidal, about as long as the diameter of the outer shell, twice as broad +at the base as one pore. + +_Dimensions._--Diameter of the outer shell 0.12, middle 0.06, inner 0.03; +pores of the cortical shell 0.012, bars 0.004; length of the polar spines +0.1, basal breadth 0.024. + +_Habitat._--Western Indian Ocean, Zanzibar, 2200 fathoms, Pullen. + + +3. _Amphisphaera jupiter_, n. sp. + +Radial proportion of the three spheres = 10 : 3 : 2. Cortical shell thick +walled, smooth, with regular, circular pores, twice as broad as the bars; +twenty to twenty-five on the half equator. Polar spines cylindro-conical, +nearly as long as the axis of the outer shell, twice as broad at the base +as one pore. + +_Dimensions._--Diameter of the outer shell 0.2, middle 0.06, inner 0.04; +pores of the cortical shell 0.01, bars 0.005; length of the polar spines +0.15 to 0.18, breadth 0.02. + +_Habitat._--South Atlantic, Station 332, depth 2200 fathoms. + + + +Subgenus 2. _Amphisphaerella_, Haeckel. + +_Definition._--Pores of the cortical shell regular, of nearly equal size +and similar form; surface thorny or spiny. + + +4. _Amphisphaera apollo_, n. sp. + +Radial proportion of the three spheres = 3 : 1.5 : 1. Cortical shell thick +walled, spiny, with regular, circular, hexagonally framed pores, of the +same breadth as the bars; twenty to twenty-two on the half equator. In each +hexagon-corner (between three pores) a bristle-like radial spine. Polar +spines cylindrical, with conical apex; one to one and a half times as long +as the axis of the outer shell, as broad as three pores at the base. +(Resembles closely _Xiphosphaera pallas_, Pl. 14, fig. 4, but differs in +the presence of two medullary shells and the absence of the fine +denticulations on the hexagonal crests.) + +_Dimensions._--Diameter of the outer shell 0.12, middle 0.06, inner 0.04; +pores and bars of the cortical shell 0.006; length of the polar spines +0.15, breadth 0.02. + +_Habitat._--Western Tropical Pacific, Station 224, depth 1850 fathoms. + + +5. _Amphisphaera mercurius_, n. sp. + +Radial proportion of the three spheres = 3 : 2 : 1. Cortical shell thin +walled, spiny, with regular, circular pores, twice as broad as the bars; +fifteen to eighteen on the half equator; between {144}them short +bristle-like radial spines. Polar spines three-sided pyramidal, about as +long as the radius of the outer shell, one-third as broad at the base. + +_Dimensions._--Diameter of the outer shell 0.15, middle 0.09, inner 0.05; +pores of the cortical shell 0.01, bars 0.005; length of the polar spines +0.09, basal breadth 0.03. + +_Habitat._--North Pacific, Station 244, depth 2900 fathoms. + + + +Subgenus 3. _Amphisphaerissa_, Haeckel. + +_Definition._--Pores of the cortical shell irregular, of different size or +form; surface smooth or a little rough, without spines or thorns. + + +6. _Amphisphaera cronos_, n. sp. (Pl. 17, fig. 5). + +Radial proportion of the three spheres = 3 : 2 : 1. Cortical shell thin +walled, smooth, with irregular, roundish pores, two to four times as broad +as the bars; eight to ten on the half equator. Outer medullary shell +similar, but with pores of half the size, connected with the cortical shell +by numerous radial beams; inner medullary shell with very small pores. +Polar spines three-sided pyramidal, as long as the axis of the inner +medullary shell, half as broad at the base. + +_Dimensions._--Diameter of the outer shell 0.12, middle 0.08, inner 0.04; +pores of the cortical shell 0.01 to 0.02, bars 0.05; length of the polar +spines 0.04, basal breadth 0.02. + +_Habitat._--South Atlantic, Station 330, surface. + + +7. _Amphisphaera pluto_, n. sp. (Pl. 17, figs. 7, 8). + +Radial proportion of the three spheres about = 4 : 2 : 1 (or 11 : 7 : 3). +Cortical shell thick walled, smooth, with very irregular, roundish pores, +two to four times as broad as the bars; eight to ten on the half equator; +often two to four pores confluent. Margin of their outer aperture double. +Polar spines conical, double contoured, as long as the radius of the outer +shell, one-third as broad at the base. + +_Dimensions._--Diameter of the outer shell 0.11, middle shell 0.07, inner +shell 0.03; pores of the cortical shell 0.01 to 0.02, bars 0.06, length of +the polar spines 0.06, basal breadth 0.02. + +_Habitat._--Central Pacific, Station 268, surface. + + + +Subgenus 4. _Amphisphaeromma_, Haeckel. + +_Definition._--Pores of the cortical shell irregular, of different size or +form; surface spiny or thorny. + + +8. _Amphisphaera mars_, n. sp. + +Radial proportion of the three spheres = 10 : 3 : 2. Cortical shell thin +walled, thorny, with irregular, roundish pores, one to three times as broad +as the bars; sixteen to twenty on the {145}half equator. Irregularly +scattered between them short conical thorns. Polar spines conical, about as +long as the axis of the outer shell, as broad at the base as the inner +shell. + +_Dimensions._--Diameter of the outer shell 0.2, middle shell 0.06, inner +shell 0.04; pores of the cortical shell 0.005 to 0.02, bars 0.006; length +of the polar spines 0.17, basal breadth 0.04. + +_Habitat._--North Atlantic, Gulf Stream, near Florida, depth 1500 fathoms, +Schaffner. + + + +Genus 52. _Amphistylus_,[75] Haeckel, 1881, Prodromus, p. 452. + +_Definition._--#Stylosphaerida# with three concentric lattice-spheres and +two free spines of different size or form. + +The genus _Amphistylus_ differs from its ancestral form, _Amphisphaera_, by +the differentiation of both polar spines, and exhibits therefore the same +relation to it that _Sphaerostylus_ bears to _Stylosphaera_. + + +1. _Amphistylus clio_, n. sp. + +Radial proportion of the three spheres = 4 : 2 : 1. Cortical shell thick +walled, smooth; its pores regular, circular, three times as broad as the +bars; eighteen to twenty on the half equator. Polar spines three-sided +pyramidal, very stout, as broad at the base as the inner medullary shell; +major spine somewhat longer than the diameter of the cortical shell; minor +spine scarcely half as long. (Similar to _Stylosphaera clio_, Pl. 16, fig. +7, but different in the double medullary shell and the different length of +the polar spines.) + +_Dimensions._--Diameter of the outer sphere 0.15, middle 0.08, inner 0.04; +pores of the outer shell 0.01, bars 0.003; length of the major spine 0.17, +minor 0.07, basal breadth 0.04. + +_Habitat._--Pacific, central area, Station 265, depth 2900 fathoms. + + +2. _Amphistylus hippocampus_, n. sp. + +Radial proportion of the three spheres = 3 : 2 : 1. Cortical shell thick +walled, smooth; its pores regular, circular, hexagonally lobed, three times +as broad as the bars; twelve to fifteen on the half equator. Major polar +spine three-sided pyramidal, about as long as the axis of cortical shell; +minor spine pommel-like, edged, scarcely one-third as long. (Similar to +_Sphaerostylus hippocampus_, Pl. 16, figs. 10, 11, but differs in the +larger size, the double medullary shell, and the straight, not curved, +major spine.) + +_Dimensions._--Diameter of the outer sphere 0.11, middle 0.07, inner 0.035; +pores of the outer shell 0.011, bars 0.004; length of the major spine 0.12, +of the minor 0.04, breadth 0.03. + +_Habitat._--North Pacific, Station 244, depth 2900 fathoms. + + +3. _Amphistylus glyptodon_, n. sp. + +Radial proportion of the three spheres = 6 : 3 : 1. Cortical shell thick +walled, spiny, with irregular, roundish pores, two to four times as broad +as the bars; ten to twelve on the half equator. {146}Inner aperture of each +pore closed by a thin fenestrated lamella with five to seven small pores. +Major polar spine three-sided pyramidal, longer than the diameter of the +outer sphere; minor polar spine scarcely as long as its radius, +pommel-shaped. (Similar to _Xiphatractus glyptodon_, Pl. 17, figs. 9, 10, +but differs in the spherical, not ellipsoidal, form of the three shells and +the size of the polar spines.) + +_Dimensions._--Diameter of the outer sphere 0.12, middle 0.06, inner 0.02; +pores and spines of the outer shell 0.01 to 0.02, bars and porules 0.006; +length of the major polar spine 0.15, of the minor 0.05, breadth 0.04. + +_Habitat._--South Pacific, Station 285, depth 2375 fathoms. + + + +Genus 53. _Saturninus_,[76] n. gen. + +_Definition._--#Stylosphaerida# with three concentric lattice-spheres and +two equal opposite spines, connected at the distal end by a circular or +elliptical ring. + +The genus _Saturninus_ differs from the similar _Saturnulus_ by the +triplication of the spherical lattice-shell; the inner shell is enclosed in +the central capsule, whilst both the others lie outside it. + + +1. _Saturninus triplex_, n. sp. + +Radial proportion of the three spheres = 4 : 3 : 1. Inner cortical shell +with regular, circular pores, of the same breadth as the bars, sixteen to +eighteen on the half equator; outer cortical shell connected with the inner +by numerous bristle-like radial spines, network very delicate, +cobweb-shaped, with irregular polygonal meshes. Ring elliptical, two and a +half times as broad as the outer shell. + +_Dimensions._--Diameter of the inner sphere 0.03, middle 0.09, outer 0.12; +pores and bars of the middle shell 0.004; major axis of the elliptical ring +0.3, minor 0.25; thickness of the ring and the axial beams 0.008. + +_Habitat._--Central Pacific, Station 272, surface. + + + +Subfamily CROMYOSTYLIDA, Haeckel, 1881, Prodromus, pp. 449, 453. + +_Definition._--#Stylosphaerida# with four concentric spherical +lattice-shells (two medullary and two cortical). + + + +Genus 54. _Stylocromyum_,[77] Haeckel, 1881, Prodromus, p. 453. + +_Definition._--#Stylosphaerida# with four concentric lattice-spheres and +two free spines of equal size and similar form. + +{147}The genus _Stylocromyum_ differs from its probable ancestral form, +_Amphisphaera_, by the duplication of the cortical shell; two opposite +radial beams, piercing the wall of the central capsule, connect it with the +double medullary shell, and are prolonged outside into two equal spines. + + +1. _Stylocromyum amphiconus_, n. sp. + +Surface of the shell smooth. Radial proportion of the four spheres = +1 : 2 : 8 : 9. Two medullary shells inside the central capsule, two +cortical shells outside it. Interval between the second and third shells +the greatest. Pores of all the shells regular, circular, two to four times +as broad as the bars. Both polar spines equal, conical, about as long as +the axis of the outermost sphere, as broad at the base as the innermost. + +_Dimensions._--Diameter of the four spheres--(A) inner medullary shell +0.03, (B) outer medullary shell 0.06, (C) inner cortical shell 0.25, (D) +outer cortical shell 0.28; length of the polar spines 0.3, basal breadth +0.03. + +_Habitat._--Central Pacific, Station 273, depth 2350 fathoms. + + +2. _Stylocromyum amphipyramis_, n. sp. + +Surface of the shell smooth. Radial proportion of the four spheres = +2 : 3 : 6 : 8. Both medullary shells with regular, circular pores, twice as +broad as the bars. Both cortical shells with irregular, roundish, much +larger pores, three to six times as broad as the bars. Both polar spines +equal or nearly equal, three-sided pyramidal, about as long as the axis of +the third shell. + +_Dimensions._--Diameter of the four spheres--(A) 0.04, (B) 0.06, (C) 0.12, +(D) 0.16; length of the polar spines 0.11, basal breadth 0.02. + +_Habitat._--Central Pacific, Station 265, depth 2900 fathoms. + + + +Genus 55. _Cromyostylus_,[78] Haeckel, 1881, Prodromus, p. 453. + +_Definition._--#Stylosphaerida# with four concentric lattice-spheres and +two free spines of different size or form. + +The genus _Cromyostylus_ differs from its ancestral form, _Stylocromyum_, +in the differentiation of the two unequal polar spines. + + +1. _Cromyostylus gladius_, n. sp. + +Surface of the shell smooth. Radial proportion of the four spheres = +1 : 3 : 10 : 12. Both medullary shells with regular, circular, simple +pores. Inner cortical shell with regular, circular, hexagonally framed +pores, twice as broad as the bars. From each hexagon-corner arises a +{148}bristle-shaped radial spine, which at the distal end gives off three +thread-like branches; by communication of these threads (at equal distances +from the centre) the delicate outer medullary shell is formed. The polar +spines very different; major spine six-sided pyramidal, longer than the +diameter of the shell; minor pommel-shaped, shorter than the radius +(similar to _Xiphatractus glyptodon_, Pl. 17, figs. 9, 10, but different in +the double spherical cortical shell). + +_Dimensions._--Diameter of the four spheres--(A) 0.02, (B) 0.06, (C) 0.2, +(D) 0.24; length of the major spine 0.3, of the minor 0.1. + +_Habitat._--Central Pacific, Station 271, depth 2425 fathoms. + + + +Subfamily CARYOSTYLIDA, Haeckel, 1881, Prodromus, pp. 449, 454. + +_Definition._--#Stylosphaerida# with five or more concentric, spherical +lattice-shells. + + + +Genus 56. _Caryostylus_, Haeckel, 1881, Prodromus, p. 454. + +_Definition._--#Stylosphaerida# with five to six or more concentric +lattice-shells and two free opposite spines of equal size and similar form. + +The genus _Caryostylus_ differs from its ancestral form, _Stylocromyum_, by +the multiplication of the concentric spheres, the number of which amounts +to five or six or more. I have only observed one single species of this +genus. Some similar forms which in my Prodromus (1881, p. 454) were annexed +to it, and disposed in three nearly allied genera (_Caryoxiphus_, +_Caryodoras_, _Caryolonche_), have now been proved to belong to other +groups, mainly ellipsoidal Druppulida. + + +1. _Caryostylus hexalepas_, n. sp. + +Surface of the spherical shell smooth. Radial proportion of the component +six concentric shells = 1 : 2 : 7 : 9 : 12 : 15. Both medullary shells +connected only by six radial beams, opposite in pairs in the three +dimensive axes. Between second and third shell numerous (twenty regularly +disposed?) radial beams. Four cortical shells connected by very numerous +(sixty to eighty or more?) short radial beams. Pores of all six shells +regular, circular, the size increasing towards the surface, two to three +times as broad as the bars. Two opposite polar spines very large, of equal +size, three times as long as the shell radius, cylindrical, club-shaped at +the thicker distal end. (The whole shell structure is similar to Pl. 15, +fig. 2, but the shells are spherical, not ellipsoidal.) + +_Dimensions._--Diameter of the six spheres--(A) 0.02, (B) 0.04, (C) 0.15, +(D) 0.18, (E) 0.24, (F) 0.3; length of the spines 0.5. + +_Habitat._--West Tropical Pacific, Station 225, depth 4475 fathoms. + + + +Subfamily SPONGOSTYLIDA, Haeckel, 1881, Prodromus, pp. 449, 455. + +_Definition._--#Stylosphaerida# with spherical spongy shell (with or +without enclosed latticed medullary shells). + + + +{149}Genus 57. _Spongolonchis_,[79] Haeckel, 1881, Prodromus, p. 455. + +_Definition._--#Stylosphaerida# with a solid sphere of spongy framework, +and with two opposite free radial spines. + +The genus _Spongolonchis_ differs from its probable ancestral form, +_Styptosphaera_, by the development of two opposite radial spines situated +in one axis. + + +1. _Spongolonchis compacta_, n. sp. + +Spongy framework of the spherical shell very compact, with small meshes, +three to four times as broad as the bars. Surface rough, but not spiny. Two +polar spines pyramidal, only as long as the radius of the shell, one-third +as broad at the base. + +_Dimensions._--Diameter of the shell 0.2; length of the spines 0.1, basal +breadth 0.03. + +_Habitat._--Central Pacific, Station 274, depth 2750 fathoms. + + +2. _Spongolonchis laxa_, n. sp. + +Spongy framework loose, with large meshes, ten to twelve times as broad as +the bars. Surface spiny. Two polar spines three-sided prismatic, longer +than the diameter of the shell (broken off in the observed specimen). + +_Dimensions._--Diameter of the shell 0.5; length of the spine 0.6 and more, +breadth 0.02. + +_Habitat._--Central Pacific, Station 265, depth 2900 fathoms. + + + +Genus 58. _Spongostylus_,[80] Haeckel, 1881, Prodromus, p. 455. + +_Definition._--#Stylosphaerida# with spongy spherical cortical shell, +enclosing in the centre a simple latticed medullary shell, and with two +opposite free radial spines. + +The genus _Spongostylus_ may probably be derived from _Spongoplegma_ by +development of two opposite radial spines in one axis. + + +1. _Spongostylus hastatus_, n. sp. + +Spongy cortical shell with compact framework, twice as broad as the +enclosed medullary shell, the pores of which are regular, circular, twice +as broad as the bars. Two polar spines, three times as long as the radius +of the shell, in the basal two-thirds cylindrical, in the distal third +compressed, two-edged, spear-shaped. + +_Dimensions._--Diameter of the cortical shell 0.1, medullary shell 0.05; +length of the spines 0.15. + +_Habitat._--South Atlantic, Station 335, depth 1425 fathoms. + + +{150}2. _Spongostylus gladiatus_, Haeckel. + + _Stylosphaera holosphaera_, Ehrenberg, 1872, Abhandl. d. k. Akad. d. + Wiss. Berlin, p. 299, Taf. viii. fig. 14. + +Spongy cortical shell with rather compact framework, four times as broad as +the enclosed medullary shell, the pores of which are irregular, roundish, +three to four times as broad as the bars. Two polar spines sword-shaped, +two-edged, as long as the shell diameter. + +_Dimensions._--Diameter of the cortical shell 0.24, medullary shell 0.06; +length of the spines 0.25. + +_Habitat._--Central Pacific, Station 268, depth 2900 fathoms; Philippine +Sea, depth 3300 fathoms. + + +3. _Spongostylus serratus_, n. sp. + +Spongy cortical shell with lax framework, ten to twelve times as broad as +the enclosed medullary shell, the pores of which are irregular, roundish, +once and a half to twice as broad as the bars. Two polar spines longer than +the shell diameter (broken off in the observed specimen), three-sided +prismatical, with three straight serrated edges. + +_Dimensions._--Diameter of the cortical shell 0.5, medullary shell 0.04; +length of the spines 0.6 or more. + +_Habitat._--South Pacific, Station 285, depth 2375 fathoms. + + + +Genus 59. _Spongostylidium_,[81] Haeckel, 1881, Prodromus, p. 455. + +_Definition._--#Stylosphaerida# with spongy spherical cortical shell, +enclosing two concentric spherical latticed medullary shells, and with two +opposite, free radial spines. + +The genus _Spongostylidium_ differs from _Spongostylus_ by duplication of +the latticed medullary shell, and therefore bears the same relation to it +as _Spongodictyon_ to _Spongoplegma_. + + +1. _Spongostylidium streptacanthum_, n. sp. + +Both medullary shells spherical, with small, regular, circular pores, twice +as broad as the bars (outer twice as broad as the inner). Spongy cortical +shell enclosing it with dense framework, four times as broad as the outer +medullary shell. Two polar spines very large, four times as long as the +diameter of the outer shell; as broad as the inner medullary shell, with +three dentated, spirally contorted edges. (Very similar to the common +_Spongosphaera streptacantha_ and to _Hexadoridium streptacanthum_, but +with only two opposite spines in one axis.) + +_Dimensions._--Diameter of the cortical shell 0.16, of the outer medullary +shell 0.04, inner 0.02; length of the spines 0.7 and more, breadth 0.02. + +_Habitat._--Indian Ocean, Cocos Islands, Rabbe. + + + +{151}Family VIII. #STAUROSPHAERIDA#, Haeckel (Pl. 15). + +_Staurosphaerida_, Haeckel, 1881, Prodromus, p. 449. + +_Definition._--#Sphaeroidea# with four radial spines on the surface of the +spherical shell, forming a regular cross, being opposite in pairs in two +axes perpendicular to one another; living solitary (not associated in +colonies). + +The family #Staurosphaerida# is distinguished from the other #Sphaeroidea# +by the possession of four radial spines, which are opposite in pairs in two +perpendicularly crossed axes. By these "two main axes" an equatorial plane +is determined, which approximates them to the #Discoidea#. But in the +latter the shells as well as the central capsule become more or less +flattened, lenticular, or discoidal, whilst in the former they remain +spherical. However, some forms of both groups are very similar, and +inspection from different sides (and mainly from the margin of the +equatorial plane) is required to determine the spherical (not compressed) +shell-form of the Staurosphaerida. As a rule the species of this family are +much rarer, and much less numerous, than those of all the other +#Sphaeroidea#. + +The most simple Staurosphaerida are the Staurostylida, with one single +spherical lattice-shell. To this ancestral group all other subfamilies can +be opposed as "Staurosphaerida concentrica," since their carapace is +composed of two or more concentric lattice-shells; two in the +Staurolonchida, three in the Stauracontida, four in the Staurocromyida, +five or more in the Staurocaryida. In all these four subfamilies the +concentric shells are simple (not spongy) fenestrated spheres. In a sixth +subfamily, in the Staurodorida, the shell is wholly or partially composed +of irregular spongy wickerwork, with or without a medullary shell in the +centre. + +_The Four Radial Spines_ in all Staurosphaerida are normally opposed in +pairs in two axes perpendicular one to another, and therefore together form +a rectangular cross. But in many species besides this normal form +individual abnormalities occur, in which the four spines in the equatorial +plane are not quite accurately opposed, so that the four angles between +them are not right angles, but more or less unequal. More rarely also their +position in the equatorial plane is not accurately retained, so that they +are placed in two, three, or four different meridian planes, intersecting +at very small variable angles. + +In the greater part of Staurosphaerida all four radial spines are quite +equal, and of the same size and form. But in some genera there takes place +a more or less considerable differentiation of the four spines, commonly in +pairs, so that the two opposite spines of each pair are equal, but the +pairs different (_Staurostylus_, _Staurolonchidium_). More rarely also both +spines of one pair become unequal, whilst those of the other pair remain +equal (_Stauroxiphos_). Very rarely all four spines assume a different size +or form. + + +{152}_Synopsis of the Genera of Staurosphaerida._ + + I. Subfamily {All four spines equal, 60. _Staurosphaera_. + Staurostylida. { + (Shell one single {Four spines different + lattice-sphere.) { in pairs, 61. _Staurostylus_. + { + {One spine larger than the + { three others, 62. _Stylostaurus_. + + II. Subfamily {All four spines {Simple, 63. _Staurolonche_. + Staurolonchida. { equal, { + (Shell with { {Branched, 64. _Staurancistra_. + two concentric { + lattice-spheres.) {Four spines different 65. + { in pairs, _Staurolonchidium_. + { + {One spine larger than + { the three others, 66. _Stauroxiphos_. + + III. Subfamily }All four spines equal, + Stauracontida. } simple, 67. _Stauracontium_. + (Shell with three } + concentric spheres.) } + + IV. Subfamily }All four spines {Simple, 68. _Staurocromyum_. + Staurocromyida. } equal, { + (Shell with four } {Branched, 69. _Cromyostaurus_. + concentric spheres.) } + + V. Subfamily }All four spines equal, 70. _Staurocaryum_. + Staurocaryida. } + (Shell with five } + or more concentric } + spheres.) } + + VI. Subfamily }Solid spongy sphere + Staurodorida. } without medullary shell, 71. _Staurodoras_. + (Shell a spongy } + sphere.) } + + + +Subfamily STAUROSTYLIDA,[82] Haeckel, Prodromus, 1881, pp. 449, 450. + +_Definition._--#Staurosphaerida# with one single spherical lattice-shell. + + + +Genus 60. _Staurosphaera_,[83] Haeckel, 1881, Prodromus, p. 450. + +_Definition._--#Staurosphaerida# with a single lattice-sphere and four +crossed equal spines. + +The genus _Staurosphaera_ may be regarded as the common ancestral form of +this subfamily, since it represents their most simple and primitive form. +From the surface of the simple lattice-sphere, enclosing the central +capsule, arise four equal, simple, radial spines, opposite in pairs in two +diameters, perpendicular one to another. _Staurosphaera_ may be derived +phylogenetically either from _Cenosphaera_ by production of the four +spines, or from _Hexastylus_ by reduction of two opposite spines. + + + +{153}Subgenus 1. _Staurosphaerantha_, Haeckel. + +_Definition._--Pores regular, all of nearly equal size and similar form; +surface smooth. + + +1. _Staurosphaera cruciata_, n. sp. + +Shell thin walled, smooth, with regular, hexagonal pores, four times as +broad as the bars; ten to twelve on the quadrant. Four crossed radial +spines three-sided pyramidal, as long as the diameter of the shell, as +broad at the base as one pore (very similar to _Hexastylus phaenaxonius_, +Pl. 21, fig. 3, but with only four spines). + +_Dimensions._--Diameter of the shell 0.12, of the pores 0.008, bars 0.002. + +_Habitat._--Central Pacific, Station 271, depth 2425 fathoms. + + +2. _Staurosphaera christiana_, n. sp. + +Shell thick walled, smooth, with regular, circular, hexagonally framed +pores, three times as broad as the bars; six to eight on the quadrant. Four +crossed spines six-sided pyramidal, as long as the radius, as broad as one +mesh. + +_Dimensions._--Diameter of the shell 0.13, pores 0.012, bars 0.004. + +_Habitat._--Central Pacific, Station 268, depth 2900 fathoms. + + +3. _Staurosphaera johannis_, n. sp. + +Shell thick walled, smooth, with regular, circular pores, four times as +broad as the bars; five to six on the quadrant. Four spines six-sided +pyramidal, half as long as the radius, as broad as one mesh. + +_Dimensions._--Diameter of the shell 0.15, pores 0.02, bars 0.005. + +_Habitat._--North Pacific, Station 241, depth 2300 fathoms. + + +4. _Staurosphaera pauli_, n. sp. + +Shell very thick walled, smooth, with regular, circular, double-edged +pores, four times as broad as the bars; eight to ten on the quadrant. Four +spines conical, as long as the radius, as broad as one mesh. + +_Dimensions._--Diameter of the shell 0.15, pores 0.016, bars 0.004. + +_Habitat._--Central Pacific, Station 265, depth 2900 fathoms. + + +5. _Staurosphaera petri_, n. sp. + +Shell thin walled, smooth, with regular, circular pores, three times as +broad as the bars; twenty to twenty-two on the quadrant. Four spines +conical, half as long as the radius, as broad as one mesh. + +_Dimensions._--Diameter of the shell 0.22, pores 0.006, bars 0.002. + +_Habitat._--South Atlantic, Station 325, depth 2650 fathoms; also fossil in +Barbados. + + +{154}6. _Staurosphaera jacobi_, n. sp. + +Shell thick walled, smooth, with regular, circular pores, twice as broad as +the bars; eleven to twelve on the quadrant. Four spines cylindrical, three +times as long as the radius, three times as broad as one mesh. + +_Dimensions._--Diameter of the shell 0.1, pores 0.006, bars 0.003. + +_Habitat._--North Atlantic, Station 353, depth 2965 fathoms. + + +7. _Staurosphaera simonis_, n. sp. + + _Haliomma_ with four spines, Bury, 1862, Polycystins of Barbados, pl. iv. + fig. 4. + +Shell thick walled, smooth, with regular, circular pores, of the same +breadth as the bars; eight to ten on the quadrant. Four spines cylindrical, +twice as long as the radius, five times as broad as one mesh. + +_Dimensions._--Diameter of the sphere 0.1, pores and bars 0.003. + +_Habitat._--Fossil in Barbados. + + + +Subgenus 2. _Staurosphaerella_, Haeckel. + +_Definition._--Pores regular, all of nearly equal size and similar form; +surface covered with by-spines or accessory thorns. + + +8. _Staurosphaera philippi_, n. sp. (Pl. 15, fig. 6). + +Shell thin walled, covered with bristle-shaped by-spines, as long as the +radius. Pores regular, circular, twice as broad as the bars; six to eight +on the quadrant. Four main spines cylindrical, five to ten times as long as +the radius, as broad as one mesh. + +_Dimensions._--Diameter of the shell 0.08, pores 0.006, bars 0.003. + +_Habitat._--Central Pacific, Station 272, surface. + + +9. _Staurosphaera andreae_, n. sp. + +Shell thick walled, with regular, circular, hexagonally framed pores, three +times as broad as the bars; nine to ten on the quadrant. From each +hexagon-corner arises a bristle-shaped by-spine, half as long as the +radius. Four main spines three-sided pyramidal, with spirally contorted +edges, as long as the radius (very similar to _Hexastylus solonis_, Pl. 21, +fig. 11, but with only four spines). + +_Dimensions._--Diameter of the shell 0.16, pores 0.01, bars 0.003. + +_Habitat._--Central Pacific, Station 265, depth 2900 fathoms. + + +{155}10. _Staurosphaera thomae_. + +Shell thick walled, with regular, circular pores, twice as broad as the +bars; twelve to fourteen on the quadrant; surface covered with short +conical by-spines. Four main spines conical, twice as long as the radius, +twice as broad as one mesh. + +_Dimensions._--Diameter of the sphere 0.2, pores 0.012, bars 0.006. + +_Habitat._--South Atlantic, Station 332, depth, 2200 fathoms. + + + +Subgenus 3. _Staurosphaerissa_, Haeckel. + +_Definition._--Pores irregular, of different size or form; surface smooth. + + +11. _Staurosphaera judae_, n. sp. + +Shell thin walled, smooth, with irregular, polygonal pores, twice to four +times as broad as the bars; six to ten on the quadrant. Four main spines +three-sided pyramidal, as long as the radius. + +_Dimensions._--Diameter of the sphere 0.15, pores 0.006 to 0.012, bars +0.003. + +_Habitat._--Central Pacific, Station 273, depth, 2350 fathoms. + + +12. _Staurosphaera crassa_, Dunikowski. + + _Staurosphaera crassa_, 1882, Denkschr. d. k. Akad. d. Wiss. Wien, Bd. + xlv. p. 27, Taf. v. figs. 52-55. + +Shell thick walled, smooth, with irregular, roundish pores, scarcely +broader than the bars; eight to ten on the quadrant. Four spines +three-sided pyramidal, nearly as long as the shell diameter. + +_Dimensions._--Diameter of the sphere 0.19, pores and bars 0.015. + +_Habitat._--Fossil in the Alpine Lias (Schafberg near Salzburg, +Dunikowski). + + +13. _Staurosphaera apostolorum_, Haeckel. + + ? _Cenosphaera megapora_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. + Berlin, p. 66, Taf. iii. fig. 1. + + ? _Cenosphaera micropora_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. + Berlin, p. 66, Taf. iii. fig. 2. + +Shell thin walled, smooth, with large, irregular, roundish pores, twice to +six times as broad as the bars; four to six on the quadrant. Four spines +conical, very stout, about as long as the shell diameter, often more or +less irregularly disposed. + +_Dimensions._--Diameter of the sphere 0.12 to 0.2, pores 0.01 to 0.03, bars +0.005. + +_Habitat._--Fossil in Barbados. + + + +{156}Subgenus 4. _Staurosphaeromma_, Haeckel. + +_Definition._--Pores irregular, of different size or form; surface covered +with by-spines or accessory thorns. + + +14. _Staurosphaera bartholomaei_, n. sp. + +Shell thin walled, with irregular, polygonal pores, three times as broad as +the bars; six to eight on the quadrant; surface covered with short +bristle-shaped by-spines. Four main spines three-sided pyramidal, twice as +long as the radius. + +_Dimensions._--Diameter of the shell 0.14, pores 0.008 to 0.016, bars 0.003 +to 0.005. + +_Habitat._--South Pacific, Station 285, depth 2375 fathoms. + + +15. _Staurosphaera thaddaei_, n. sp. + +Shell thick walled, with irregular, roundish, polygonally framed pores, +twice to three times as broad as the bars; five to seven on the quadrant; +surface covered with bristle-shaped spines, half as long as the radius. +Four main spines pyramidal, as long as the radius. + +_Dimensions._--Diameter of the shell 0.12, pores 006 to 0.012, bars 0.004. + +_Habitat._--Central Pacific, Station 266, depth 2750 fathoms; also fossil +in Barbados. + + +16. _Staurosphaera matthaei_, n. sp. + +Shell thick walled, with irregular, roundish pores, twice to five times as +broad as the bars; ten to twelve on the quadrant; surface covered with +short conical thorns or by-spines. Four main spines conical, as long as the +radius. + +_Dimensions._--Diameter of the shell 0.15, pores 0.004 to 0.01, bars 0.002. + +_Habitat._--North Pacific, Station 253, depth 3125 fathoms. + + + +Genus 61. _Staurostylus_,[84] Haeckel, 1881, Prodromus, p. 450. + +_Definition._--#Staurosphaerida# with one single lattice-sphere and four +crossed spines which are arranged in opposite pairs, one pair opposite +being larger than the other. + +The genus _Staurostylus_ has been developed from _Staurosphaera_ by +differentiation of the four crossed spines in pairs; two opposite spines +growing much more strongly than the other two. + + +1. _Staurostylus graecus_, n. sp. + +Shell thick walled, smooth, with regular, circular, hexagonally framed +pores, twice as broad as the bars; six to eight on the quadrant. Spines +three-sided prismatic, pointed, as broad as {157}one mesh; two opposite +larger spines as long as the diameter of the shell, two smaller only as +long as the radius. + +_Dimensions._--Diameter of the shell 0.15, pores 0.01, bars 0.005; length +of the major spines 0.16, minor 0.08. + +_Habitat._--Central Pacific, Station 274, depth 2750 fathoms. + + +2. _Staurostylus latinus_, n. sp. + +Shell thin walled, smooth, with regular, circular, double-edged pores, +three times as broad as the bars; twelve to fourteen on the quadrant. +Spines conical, twice as broad at the base as one mesh; two opposite larger +spines as long as the radius of the shell, two smaller only one-third as +long. + +_Dimensions._--Diameter of the shell 0.24, pores 0.012, bars 0.004; length +of the major spines 0.12, minor 0.04. + +_Habitat._--South Pacific, Station 295, depth 1500 fathoms. + + +3. _Staurostylus germanicus_, n. sp. + +Shell thick walled, covered with bristle-shaped by-spines, half as long as +the radius. Pores regular, circular, hexagonally framed, twice as broad as +the bars; eight to ten on the quadrant. From each hexagon-corner arises one +short by-spine. Four main spines three-sided pyramidal, as broad at the +base as one mesh; two opposite larger spines one and a half times as long +as the radius, two smaller two-thirds as long. + +_Dimensions._--Diameter of the shell 0.16, pores 0.008, bars 0.004; length +of the major spines 0.12, minor 0.08. + +_Habitat._--North Pacific, Station 244, depth 2900 fathoms. + + + +Genus 62. _Stylostaurus_,[85] 1881, Prodromus, p. 450. + +_Definition._--#Staurosphaerida# with one single lattice-sphere and four +crossed spines, one of which is much larger than the other three. + +The genus _Stylostaurus_ differs from the preceding in the extraordinary +development of one of the four spines, which is much longer than the other +three; these may be equal or different. + + +1. _Stylostaurus caudatus_, n. sp. (Pl. 13, fig. 7). + +Shell thick walled, smooth, with regular, circular, hexagonally framed +pores, twice as broad as the bars; five to six on the quadrant. Spines +three-sided pyramidal, as broad at the base as {158}one mesh; one of the +spines longer than the shell diameter, the opposite spine nearly as long as +the shell radius; both lateral spines scarcely one-third as long. + +_Dimensions._--Diameter of the shell 0.1, pores 0.01, bars 0.005; length of +the major spine 0.14, of the opposite 0.04, of both lateral spines 0.012. + +_Habitat._--Central Pacific, Station 266, depth 2750 fathoms. + + +2. _Stylostaurus gladiatus_, n. sp. + +Shell thick walled, smooth, with regular, circular pores, three times as +broad as the bars; nine to ten on the quadrant. Spines three-sided +prismatic, as broad at the base as one mesh; one of the spines longer than +the shell diameter, and much larger than the other three, which are nearly +equal (half as long as the radius). + +_Dimensions._--Diameter of the shell 0.2, pores 0.015, bars 0.005; length +of the major spine 0.25, of the three others 0.005. + +_Habitat._--Central Pacific, Station 271, depth 2425 fathoms. + + + +Subfamily STAUROLONCHIDA,[86] Haeckel, 1881, Prodromus, pp. 449, 451. + +_Definition._--#Staurosphaerida# with two concentric spherical +lattice-shells. + + + +Genus 63. _Staurolonche_,[87] Haeckel, 1881, Prodromus, p. 451. + +_Definition._--#Staurosphaerida# with two concentric lattice-spheres and +four crossed, equal, simple spines. + +The genus _Staurolonche_ may be derived either from _Staurosphaera_ by the +duplication of the lattice-sphere, or from _Carposphaera_ by the production +of four crossed radial spines, lying in one meridional plane, or from +_Hexalonche_ by the reduction of two opposite spines. + + + +Subgenus 1. _Staurolonchantha_, Haeckel. + +_Definition._--Pores of the cortical shell regular, and of nearly equal +size and similar form; surface smooth. + + +1. _Staurolonche hexagona_, n. sp. + + _Haliomma hexagonum_, Ehrenberg, 1854, Mikrogeol., Taf. xxxvb., Bd. iv. + fig. 17. + + _Haliomma hexagonum_, Haeckel, 1862, Monogr. d. Radiol., p. 434. + +Cortical shell thin walled, smooth, three times as broad as the medullary +shell, with regular, hexagonal pores, four times as broad as the bars; +seven to eight on the quadrant. Four spines three-sided pyramidal, somewhat +longer than the radius, as broad at the base as one mesh. + +{159}_Dimensions._--Diameter of the outer shell 0.12, inner 0.04; cortical +pores 0.012, bars 0.003; length of the spines 0.08. + +_Habitat._--North Atlantic, Station 64, depth 2700 fathoms. + + +2. _Staurolonche spinozae_, n. sp. + +Cortical shell thick walled, smooth, twice as broad as the medullary shell, +with regular, circular, hexagonally framed pores, three times as broad as +the bars; five to six on the quadrant. Four spines three-sided pyramidal, +half as long as the radius, as broad at the base as one mesh. + +_Dimensions._--Diameter of the outer shell 0.16, inner 0.08; cortical pores +0.012, bars 0.004; length of the spines 0.04. + +_Habitat._--Central Pacific, Station 271, surface. + + +3. _Staurolonche aperta_, Haeckel. + + _Haliomma apertum_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. + Berlin, p. 74, Taf. xxviii. fig. 5. + +Cortical shell thin walled, smooth, three times as broad as the medullary +shell; pores regular, circular, five times as broad as the bars; four to +five on the quadrant. Four spines conical, as long as the radius, as broad +as one mesh. + +_Dimensions._--Diameter of the outer shell 0.1, inner 0.03; cortical pores +0.015, bars 0.003; length of the spines 0.05. + +_Habitat._--Fossil in Barbados. + + +4. _Staurolonche brunonis_, n. sp. + +Cortical shell thick walled, smooth, twice as broad as the medullary shell, +with regular, circular pores, three times as broad as the bars; eight to +ten on the quadrant. Four spines cylindro-conical, longer than the +diameter, twice as broad as one mesh. + +_Dimensions._--Diameter of the outer shell 0.08, inner 0.04; cortical pores +0.006, bars 0.002; length of the spines 0.12. + +_Habitat._--Central Pacific, Station 268, depth 2900 fathoms. + + +5. _Staurolonche pertusa_, n. sp. (Pl. 15, figs. 5, 5_a_). + +Cortical shell thin walled, smooth, three times as broad as the medullary +shell, with regular, circular pores, three times as broad as the bars; +eight to ten on the quadrant. Pores of the medullary shell only one-third +as large, also circular. Four spines three-sided prismatic, three times as +long as the radius; each of their three thin wings perforated by a single +row of small pores. + +_Dimensions._--Diameter of the outer shell 0.1, inner 0.033; cortical pores +0.01, bars 0.003; length of the spines 0.15. + +_Habitat._--North Atlantic, Station 353, surface. + + + +{160}Subgenus 2. _Staurolonchella_, Haeckel. + +_Definition._--Pores of the cortical shell regular, and of nearly equal +size and similar form; surface covered with by-spines or thorns. + + +6. _Staurolonche straussii_, n. sp. + +Cortical shell thin walled, four times as broad as the medullary shell, and +covered with numerous bristle-shaped by-spines, half as long as the radius. +Pores regular, circular, hexagonally framed, twice as broad as the bars; +six to eight on the radius. On each hexagonal frame twelve by-spines (six +at the corners, six in the middle between them). Four main spines six-sided +pyramidal, about as long as the radius, twice as broad as one mesh. + +_Dimensions._--Diameter of the outer shell 0.16, inner 0.04; cortical pores +0.016, bars 0.008; length of the spines 0.1. + +_Habitat._--West Tropical Pacific, Station 225, depth 4475 fathoms. + + +7. _Staurolonche feuerbachii_, n. sp. + +Cortical shell thick walled, five times as broad as the medullary shell, +and covered with short conical by-spines. Pores regular, circular, twice as +broad as the bars; twenty to twenty-two on the quadrant. Four main spines +three-sided prismatic, with pyramidal apex, two to three times as long as +the radius, twice as broad as one mesh. + +_Dimensions._--Diameter of the outer shell 0.27, of the inner 0.055; +cortical pores 0.008, bars 0.004; length of the spines 0.3 to 0.4. + +_Habitat._--Fossil in Barbados. + + +8. _Staurolonche moleschottii_, n. sp. + +Cortical shell thick walled, three times as broad as the medullary shell, +and covered with short conical by-spines. Pores regular, circular, of the +same breadth as the bars; fourteen to sixteen on the quadrant. Four main +spines conical, as long as the radius, three times as broad at the base as +one mesh. + +_Dimensions._--Diameter of the outer shell 0.15, inner 0.05; cortical pores +and bars 0.004; length of the spines 0.08. + +_Habitat._--Central Pacific, Station 268, depth 2900 fathoms. + + + +Subgenus 3. _Staurolonchissa_, Haeckel. + +_Definition._--Pores of the cortical shell irregular, of different size or +form; surface smooth. + + +9. _Staurolonche holbachii_, n. sp. + +Cortical shell thin walled, with smooth surface, three times as broad as +the medullary shell. Pores irregular, polygonal, twice to four times as +broad as the bars. Four main spines three-sided prismatic, longer than the +shell diameter. + +{161}_Dimensions._--Diameter of the outer shell 0.12, inner 0.04; cortical +pores 0.006 to 0.012, bars 0.003; length of the spines 0.15. + +_Habitat._--South Pacific, Station 295, depth 1500 fathoms. + + +10. _Staurolonche gassendii_, n. sp. + +Cortical shell thick walled, with smooth surface, four times as broad as +the medullary shell. Pores irregular, roundish, three to five times as +broad as the bars. Four main spines conical, as long as the radius. + +_Dimensions._--Diameter of the outer shell 0.2, inner 0.05; cortical pores +0.01 to 0.02, bars 0.004; length of the spines 0.1. + +_Habitat._--North Atlantic, Station 353, depth 2965 fathoms. + + + +Subgenus 4. _Staurolonchura_, Haeckel. + +_Definition._--Pores of the cortical shell irregular, of different size or +form; surface covered with by-spines or thorns. + + +11. _Staurolonche epicurii_, n. sp. + +Cortical shell thick walled, five times as broad as the medullary shell, +and covered with numerous bristle-shaped by-spines (half as long as the +radius). Pores irregular, roundish, polygonally framed, twice to three +times as broad as the bars. Four main spines pyramidal, as long as the +radius. + +_Dimensions._--Diameter of the outer shell 0.22, inner 0.044; cortical +pores 0.02 to 0.04, bars 0.012; length of the spines 0.1. + +_Habitat._--Central Pacific, Station 271, depth 2425 fathoms. + + +12. _Staurolonche lucretii_, n. sp. + +Cortical shell thick-walled, three times as broad as the medullary shell, +and covered with numerous short, conical thorns. Pores irregular, roundish, +twice to four times as broad as the bars. Four main spines conical, half as +long as the radius. + +_Dimensions._--Diameter of the outer shell 0.15, inner 0.05; cortical pores +0.015 to 0.03, bars 0.008; length of the spines 0.04. + +_Habitat._--Central Pacific, Station 265, depth 2900 fathoms. + + + +Genus 64. _Staurancistra_,[88] Haeckel, 1881, Prodromus, p. 451. + +_Definition._--#Staurosphaerida# with two concentric lattice-spheres and +four crossed, equal, branched spines. + +{162}The genus _Staurancistra_ differs from its ancestral form, +_Staurolonche_, in the ramification of the four crossed spines. + + +1. _Staurancistra quadricuspis_, n. sp. + +Cortical shell thin walled, with rough, thorny surface, and irregular, +roundish pores, twice to four times as broad as the bars; six to eight on +the quadrant. Medullary shell one-third as large, with regular, circular +pores; connected with the cortical shell by four crossed radial beams. +These are prolonged outside into four strong three-sided prismatic spines, +nearly as long as the shell diameter, each having three curved branches +below the distal end. (Similar to _Hexancistra quadricuspis_, Pl. 22, fig. +11, but with only four spines.) + +_Dimensions._--Diameter of the cortical shell 0.16, of the medullary shell +0.05; pores of the former 0.06 to 0.012, bars 0.003; length of the spines +0.14, breadth 0.012. + +_Habitat._--Central Pacific, Station 271, depth 2425 fathoms. + + + +Genus 65. _Staurolonchidium_,[89] n. gen. + +_Definition._--#Staurosphaerida# with two concentric lattice-spheres and +four crossed simple spines which are disposed in two different pairs, two +opposite being larger than the other two. + +The genus _Staurolonchidium_ has arisen from _Staurolonche_ by the stronger +growth of the two opposite spines, the other two remaining stationary; both +spines of each pair equal. + + +1. _Staurolonchidium artioscelides_, n. sp. + +Cortical shell thin walled, with smooth surface, three times as broad as +the medullary shell. Pores regular, circular, hexagonally framed, twice as +broad as the bars; eight to ten on the quadrant. Four radial spines +three-sided pyramidal, as broad as one mesh; two opposite larger spines +three times as long as the two smaller, which are about equal to the +radius. + +_Dimensions._--Diameter of the cortical shell 0.16, medullary shell 0.05; +pores of the former 0.012, bars 0.006; length of the major spines 0.24, +minor 0.08. + +_Habitat._--Central Pacific, Station 265, surface. + + +2. _Staurolonchidium perspicuum_, Haeckel. + + _Haliomma perspicuum_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. + Berlin, p. 74, Taf. xxix. fig. 1. + +Cortical shell thin walled, covered with small conical by-spines, five +times as broad as the medullary shell. Pores regular, circular, eight times +as broad as the bars; three to four on the quadrant. Four radial spines +three-sided pyramidal, scarcely one-third as broad as one mesh; two +opposite larger spines four times as long as the two smaller, which are +about equal to half the radius. + +{163}_Dimensions._--Diameter of the cortical shell 0.12, medullary shell +0.025; pores of the former 0.03, bars 0.004; length of the major spines +0.12, minor 0.03. + +_Habitat._--Fossil in Barbados. + + + +Genus 66. _Stauroxiphos_,[90] n. gen. + +_Definition._--#Staurosphaerida# with two concentric lattice-spheres and +four crossed simple spines, one of which is much larger than the other +three. + +The genus _Stauroxiphos_ differs from its ancestral form, _Staurolonche_, +in the greater development of one single spine, and exhibits therefore the +same relation to it that _Stylostaurus_ bears to _Staurosphaera_. + + +1. _Stauroxiphos gladius_, n. sp. (Pl. 15, fig. 7). + +Cortical shell thick walled, smooth, three times as broad as the medullary +shell. Pores of the outer shell regular, circular, regularly six-lobed on +the outer opening, four times as broad as the bars; about six on the +quadrant. Pores of the inner shell only one-third as large, simple, +circular. Three of the four radial spines of nearly equal size, +pommel-shaped, with three prominent, dentated wings, somewhat shorter than +the shell radius and about half as broad as long; the fourth spine much +larger, sword-like, about three times as long as the shell radius. + +_Dimensions._--Diameter of the outer shell 0.12, of the inner 0.04; pores +of the former 0.01, bars 0.0025; pores of the latter 0.003, bars 0.001; +length of the major spine 0.18, of the three minor 0.04. + +_Habitat._--Central Pacific, Station 266, depth 2750 fathoms. + + + +Subfamily STAURACONTIDA,[91] Haeckel, 1881, Prodromus, p. 52. + +_Definition._--#Staurosphaerida# with three concentric spherical +lattice-shells. + + + +Genus 67. _Stauracontium_,[92] Haeckel, 1881, Prodromus, p. 452. + +_Definition._--#Staurosphaerida# with three concentric lattice-spheres and +four crossed, equal, simple spines. + +The genus _Stauracontium_ differs from its probable ancestral form, +_Staurolonche_, in the duplication of the cortical shell. + + + +Subgenus 1. _Stauracontarium_, Haeckel. + +_Definition._--Pores of the cortical shell regular, all of nearly equal +size and similar form; surface smooth. + + +{164}1. _Stauracontium cruciferum_, n. sp. + +Cortical shell thin walled, smooth, with regular, hexagonal pores, four +times as broad as the bars; eight to ten on the quadrant. Radial proportion +of the three spheres = 1 : 3 : 9. Connecting radial beams between them six +(opposite in pairs in the three dimensive axes), but only four of them are +prolonged outside into four stout three-sided prismatic spines, lying in +one equatorial plane, as long as the shell diameter. + +_Dimensions._--Diameter of the outer shell 0.22, middle 0.07, inner 0.025; +cortical pores 0.012, bars 0.003; length of the spines 0.2. + +_Habitat._--Central Pacific, Station 268, depth 2900 fathoms. + + +2. _Stauracontium tetracanthum_, Haeckel. + + _Haliomma tetracanthum_, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. + Berlin, p. 295, Taf. x. figs. 7, 8. + +Cortical shell thin walled, smooth, with regular, circular pores, three +times as broad as the bars; five to six on the quadrant. Radial proportion +of the three spheres = 1 : 3 : 12. Radial spines three-sided pyramidal, +about as long as the shell diameter. + +_Dimensions._--Diameter of the outer shell 0.12, middle 0.03, inner 0.01; +cortical pores 0.01, bars 0.003; length of the spines 0.1. + +_Habitat._--Indian Ocean, Zanzibar, depth 2200 fathoms, Pullen. + + +3. _Stauracontium tetracontium_, Haeckel. + + _Actinomma tetracanthum_, Stoehr, 1880, Palaeontogr. 26, p. 91, Taf. ii. + fig. 6. + +Cortical shell thin walled, rough, with regular, circular pores, of the +same breadth as the bars; six to seven on the quadrant. Radial proportion +of the three spheres = 1 : 2.5 : 8. Radial spines three-sided pyramidal, +nearly as long as the shell diameter. + +_Dimensions._--Diameter of the outer shell 0.1, middle 0.03, inner 0.013; +cortical pores and bars 0.006; length of the spines 0.08. + +_Habitat._--Fossil in Tertiary rocks of Sicily; Grotte, Caltanisetta. + + + +Subgenus 2. _Stauracontellium_, Haeckel. + +_Definition._--Pores of the cortical shell regular, and of nearly equal +size and similar form; surface covered with numerous small thorns or +by-spines. + + +4. _Stauracontium daturaeforme_, Haeckel. + + _Actinomma daturaeforme_, Stoehr, 1880, Palaeontogr. 26, p. 93, Taf. ii. + fig. 13. + +Cortical shell thick walled, covered with short thorns, and with regular, +hexagonal pores, five times as broad as the bars; six to seven on the +quadrant. Radial proportion of the three spheres = 1 : 3 : 3.5. Radial +spines six-sided pyramidal, about half as long as the radius and one-fourth +as broad. + +{165}_Dimensions._--Diameter of the outer shell 0.15, middle 0.13, inner +0.04; cortical pores 0.017, bars 0.003; length of the spines 0.03. + +_Habitat._--Fossil in Tertiary rocks of Sicily; Grotte, Stoehr. + + +5. _Stauracontium sparganium_, n. sp. + +Cortical shell thick walled, covered with very numerous, short, conical +spines, and with regular, circular pores, five times as broad as the bars; +sixteen to eighteen on the quadrant. Radial proportion of the three spheres += 2 : 3 : 9. Radial main spines three-sided prismatic, as long as the +radius or longer. + +_Dimensions._--Diameter of the outer shell 0.275, middle 0.09, inner 0.06; +cortical pores 0.01, bars 0.002; length of the spines 0.15. + +_Habitat._--Fossil in Barbados. + + + +Subgenus 3. _Stauracontidium_, Haeckel. + +_Definition._--Pores irregular, of different size or form; surface smooth. + + +6. _Stauracontium antarcticum_, n. sp. + +Cortical shell thin walled, smooth. Pores irregular, roundish, two to four +times as broad as the bars. Radial proportion of the three spheres = +1 : 2 : 8. Radial spines conical, as long as the radius. + +_Dimensions._--Diameter of the outer shell 0.2, middle 0.05, inner 0.025; +cortical pores 0.006 to 0.012, bars 0.003; length of the spines 0.1. + +_Habitat._--Antarctic Ocean, Station 157, depth 1950 fathoms. + + + +Subgenus 4. _Stauracontonium_, Haeckel. + +_Definition._--Pores irregular, of different size or form; surface covered +with thorns or by-spines. + + +7. _Stauracontium setosum_, n. sp. + +Cortical shell thin walled, covered with thin bristle-shaped by-spines, +half as long as the radius. Pores irregular, polygonal, three to five times +as broad as the bars. Proportion of the three spheres = 1 : 2 : 6. Radial +main spines pyramidal, nearly as long as the shell diameter. + +_Dimensions._--Diameter of the outer shell 0.15, middle 0.05, inner 0.025; +cortical pores 0.01 to 0.015, bars 0.003; length of the spines 0.12. + +_Habitat._--Central Pacific, Station 266, depth 2750 fathoms. + + +8. _Stauracontium papillosum_, n. sp. + +Cortical shell thick walled, covered with short conical papillae or +by-spines. Pores irregular, roundish, two to four times as broad as the +bars. Proportion of the three spheres = 1 : 3 : 12. Radial main spines +conical, as long as the radius. + +{166}_Dimensions._--Diameter of the outer shell 0.24, middle 0.06, inner +0.02; cortical pores 0.007 to 0.015, bars 0.004; length of the spines 0.12. + +_Habitat._--Central Pacific, Station 274, depth 2750 fathoms. + + + +Subfamily STAUROCROMYIDA,[93] Haeckel, 1881, Prodromus, pp. 449, 453. + +_Definition._--#Staurosphaerida# with four concentric spherical +lattice-shells. + + + +Genus 68. _Staurocromyum_,[94] Haeckel, 1881, Prodromus, p. 453. + +_Definition._--#Staurosphaerida# with four concentric lattice-spheres and +four crossed, equal, simple spines. + +The genus _Staurocromyum_ has arisen probably from _Stauracontium_ by +duplication of the cortical shell, two concentric shells lying within, two +others outside the central capsule. + + +1. _Staurocromyum quadruplex_, n. sp. + +Radial proportion of the four spheres = 1 : 2 : 8 : 10. Both medullary +shells with very small, regular, circular pores. Inner cortical shell with +regular, circular, hexagonally-framed pores, twice as broad as the bars; +from each hexagon-corner arises a small by-spine, and these, connected by +tangential branches at equal distances from the centre, form the delicate +outer cortical shell, with spiny surface. Four main spines three-sided +pyramidal, as long as the shell radius. + +_Dimensions._--Diameter of the four shells--(A) 0.25, (B) 0.2, (C) 0.05, +(D) 0.025; length of the spines 0.12. + +_Habitat._--Central Pacific, Station 271, depth 2425 fathoms. + + +2. _Staurocromyum quadrispinum_, n. sp. + +Radial proportion of the four spheres = 1 : 3 : 9 : 12. Both medullary +shells with small, regular, circular pores. Both cortical shells with +irregular, roundish pores. Surface covered with short, conical by-spines. +Four main spines cylindro-conical, somewhat longer than the shell diameter. + +_Dimensions._--Diameter of the four shells--(A) 0.24, (B) 0.18, (C) 0.06, +(D) 0.02. + +_Habitat._--Central Pacific, Station 265, depth 2900 fathoms. + + + +Genus 69. _Cromyostaurus_,[95] Haeckel, 1881, Prodromus, p. 453. + +_Definition._--#Staurosphaerida# with four concentric lattice-spheres and +four crossed, equal, branched spines. + +{167}The genus _Cromyostaurus_ differs from the preceding _Staurocromyum_, +its ancestral form, in the ramification of the four crossed spines. + + +1. _Cromyostaurus verticillatus_, n. sp. + +Radial proportion of the four spheres = 1 : 3 : 11 : 13. Both medullary +shells with small, regular, circular pores; inner cortical shell with +regular, hexagonal pores; from the hexagon-corners arise small, radial +by-spines, which at equal distances from the centre send out forked +tangential branches, three from each spine, and by communication of these +form the outer, delicate, cortical shell. Four main spines nearly as long +as the shell diameter, three-sided prismatic, with four to six verticils of +ramified lateral branches, each verticil composed of three forked branches, +which ramify again. + +_Dimensions._--Diameter of the four shells--(A) 0.26, (B) 0.22, (C) 0.06, +(D) 0.02; length of the spines 0.24. + +_Habitat._--Central Pacific, Station 268, depth 2900 fathoms. + + + +Subfamily STAUROCARYIDA,[96] Haeckel, 1881, Prodromus, pp. 449, 454. + +_Definition._--#Staurosphaerida# with five or more concentric spherical +lattice-shells. + + + +Genus 70. _Staurocaryum_,[97] Haeckel, 1881, Prodromus, p. 454. + +_Definition._--#Staurosphaerida# with five or more concentric +lattice-spheres and four crossed, equal spines. + +The genus _Staurocaryum_ has arisen from the preceding _Staurocromyum_ by +the further multiplication of the concentric spheres; in the only observed +form there are six, at nearly equal distances apart. + + +1. _Staurocaryum arborescens_, n. sp. (Pl. 15, fig. 8). + +Shell composed of six concentric latticed spheres, at nearly equal +distances apart, and with somewhat regular, circular pores, the size of +which gradually increases from the first to the sixth shell. The surface of +the outermost shell is densely covered with numerous arborescent by-spines, +which bifurcate from three to four times, and are three-sided pyramidal at +the base, and twice as long as the distance between each two shells. The +six shells are connected only by four crossed, conical, radial beams, which +increase in diameter from the centre, and are prolonged outside into very +stout cylindrical, radial spines, irregularly covered with small thorns and +forked ramules, and nearly as long as the shell diameter. Only a single +specimen was observed. + +{168}_Dimensions._--Diameter of the whole shell 0.22; distance between each +two shells 0.02; length of the by-spines 0.05, of the main spines 0.2. + +_Habitat._--Indian Ocean, Cocos Islands, surface, Rabbe. + + + +Subfamily STAURODORIDA,[98] Haeckel, 1881, Prodromus, pp. 449, 455. + +_Definition._--#Staurosphaerida# with spongy, spherical shell (with or +without enclosed concentric lattice-shells). + + + +Genus 71. _Staurodoras_,[99] Haeckel, 1881, Prodromus, p. 455. + +_Definition._--#Staurosphaerida# with solid, spongy, spherical shell and +four crossed simple spines. + +The genus _Staurodoras_ may be developed from _Styptosphaera_ by the +production of four crossed spines on the simple, spongy, spherical shell, +which is composed of looser or denser irregular wicker-work, without +enclosed medullary shell. + + +1. _Staurodoras spongosphaera_, n. sp. + +Four crossed spines, two to three times as long as the diameter of the +spongy sphere, three-sided prismatic, with three dentated and spirally +contorted edges. (Form of _Spongosphaera streptacantha_, but without +medullary shell and with four equal spines, crossed regularly at right +angles.) + +_Dimensions._--Diameter of the sphere 0.25; length of the spines 0.4 to +0.7. + +_Habitat._--Central Pacific, Station 271, surface. + + +2. _Staurodoras mojsisovicsi_, Dunikowski. + + _Staurodoras mojsisovicsi_, Dunikowski, 1882, Denkschr. d. k. Akad. d. + Wiss. Wien, Bd. xlv. p. 28, Taf. v. fig. 56. + +Four crossed spines, one and a half times as long as the diameter of the +spongy sphere, three-sided pyramidal, with three smooth edges. (What +Dunikowski describes as "inner canals" of the spines are their edges.) + +_Dimensions._--Diameter of the sphere 0.14; length of the spines 0.18 to +0.2. basal breadth 0.04. + +_Habitat._--Fossil in the Alpine Lias (Schafberg near Salzburg). + + +3. _Staurodoras liassica_, Dunikowski. + + _Staurodoras liassica_, Dunikowski, 1882, Denkschr. d. k. Akad. d. Wiss. + Wien, Bd. xlv. p. 28, Taf. v. fig. 57. + +Four crossed spines, shorter than the diameter of the spongy sphere, +conical or pyramidal (?). + +_Dimensions._--Diameter of the sphere 0.19; length of the spine 0.13, basal +breadth 0.045. + +_Habitat._--Fossil in the Alpine Lias (Schafberg near Salzburg). + + +{169}4. _Staurodoras wandae_, Dunikowski. + + _Staurodoras wandae_, Dunikowski, 1882, Denkschr. d. k. Akad. d. Wiss. + Wien, Bd. xlv. p. 28, Taf. v. fig. 58. + +Four crossed spines shorter than the radius of the spongy sphere, conical. +(May be the young form of the preceding species.) + +_Dimensions._--Diameter of the sphere 0.14; length of the spines 0.06, +basal breadth 0.05. + +_Habitat._--Fossil in the Alpine Lias (Schafberg near Salzburg). + + + +Family IX. #CUBOSPHAERIDA#, Haeckel (Pls. 21-25). + +_Cubosphaerida_, Haeckel, 1881, Prodromus, p. 449. + +_Definition._--#Sphaeroidea# with six radial spines on the surface of the +spherical shell, opposite in pairs in the three dimensive axes, +perpendicular one to another; living solitary (not associated in colonies). + +The family #Cubosphaerida# is distinguished from the other #Sphaeroidea# by +the possession of six radial spines, which are opposite in pairs in three +different axes, one perpendicular to the other two. These three axes are +the typical "dimensive axes," which are more or less differentiated in the +#Larcoidea#. But in these latter the shell itself and the enclosed central +capsule become affected by the unequal growth in the three axes, whilst in +the former the capsule constantly, and commonly also the shell, remains +spherical. Sometimes the shell assumes the form of a regular octahedron, +from the six corners of which arise the six radial spines, indicating its +three axes. + +The most simple Cubosphaerida are the Hexastylida, with one single, +spherical lattice-shell. To this ancestral group all other subfamilies can +be opposed as "Cubosphaerida concentrica," as their carapace is composed of +two or more concentric lattice-shells--two in the Hexalonchida, three in +the Hexacontida, four in the Hexacromyida, five or more in the Hexacaryida. +In all these four subfamilies the concentric shells are simple (not +spongy), fenestrated spheres. In a sixth subfamily, in the Hexadorida, the +shell is wholly or partially composed of irregular, spongy wicker-work or +loose reticulations, with or without a medullary shell in the centre. + +The _Six Radial Spines_ of the Cubosphaerida are normally opposite in pairs +in the three dimensive axes, each of which is perpendicular to the other +two. But in many species besides this normal form occur individual +abnormalities, in which the six spines are not quite accurately opposed, +but more or less divergent; and often also the three dimensive planes +(determined each by two axes) are not quite regular, but more or less +uneven. More rarely the six spines appear disposed in quite an irregular +manner. + +In the greater part of the Cubosphaerida all six spines are quite equal, of +the same size and form. But in some genera a more or less considerable +differentiation takes place, so {170}that two pairs or all three pairs of +spines become different; very rarely, also both spines of one pair become +unequal (probably only an individual abnormality). Those variations +correspond to the differences between the crystalline systems. The common +Cubosphaerida, with three equal spine-pairs, correspond to the regular or +cubic system, with three equal axes. The rarer forms (_Hexastylarium_, +_Hexaloncharium_, _Hexacontarium_) exhibit two equal pairs and one +different pair; they correspond to the quadratic system, with three +perpendicular axes, two of which are equal, the third unequal. Still more +rare are those forms (_Hexastylidium_, _Hexalonchidium_), in which all +three pairs of spines are different, corresponding to the three unequal +axes of the rhombic crystalline system. + +_Synopsis of the Genera of Cubosphaerida._ + + {All six radial spines simple, + I. Subfamily { of equal size, 72. _Hexastylus_. + Hexastylida. { + (Shell one {Six spines of {Two pairs equal, + simple { different sizes,{ one pair + latticed { all six simple. { different, 73. _Hexastylarium_. + sphere.) { { + { {All three pairs + { { different, 74. _Hexastylidium_. + + {All six radial {Spines simple, 75. _Hexalonche_. + { spines of { + II. Subfamily { equal size. {Spines branched, 76. _Hexancistra_. + Hexalonchida. { + (Shell composed {Six spines {Two pairs equal, + of two { simple, in { one pair + concentric { pairs of { different, 77. _Hexaloncharium_. + latticed { different sizes. + spheres.) { {All three pairs + { { different, 78. _Hexalonchidium_. + + {All six radial {Spines simple, 79. _Hexacontium_. + III. Subfamily { spines of { + Hexacontida. { equal size. {Spines branched, 80. _Hexadendron_. + (Shell composed { + of three {Six spines Two pairs equal, + spheres.) { simple, of one pair + { different sizes. different, 81. _Hexacontarium_. + + IV. Subfamily }All six radial Spines simple, + Hexacromyida. } spines of not branched, 82. _Hexacromyum_. + (Four concentric} equal size. + spheres.) } + + V. Subfamily }All six radial {Spines simple, 83. _Cubosphaera_. + Hexacaryida. } spines of { + (Five or more } equal size. {Spines branched, 84. _Hexacaryum_. + spheres.) } + + {Without latticed + { medullary + VI. Subfamily }All six radial { shell, 85. _Cubaxonium_. + Hexadorida. } spines of { + (Shell a spongy } equal size, {With one single + sphere, with } simple (not { medullary + or without an } branched). { shell, 86. _Hexadoras_. + enclosed } { + central } {With two + medullary } { medullary + shell.) } { shells, 87. _Hexadoridium_. + + + +{171}Subfamily HEXASTYLIDA,[100] Haeckel, 1881, Prodromus, pp. 449, 450. + +_Definition._--#Cubosphaerida# with one single spherical lattice-shell. + + + +Genus 72. _Hexastylus_,[101] Haeckel, 1881, Prodromus, p. 450. + +_Definition._--#Cubosphaerida# with one simple lattice-sphere and six +simple spines of equal size. + +The genus _Hexalonche_ is the most simple form of all Cubosphaerida, and +may be regarded as the common ancestral form of this family. It can be +derived phylogenetically from _Cenosphaera_, by development of six radial +spines on the surface of the simple spherical lattice-shell. These six +simple spines are of equal size and opposite in pairs in the three +dimensive axes, corresponding to the three equal axes of a cubic crystal. + + + +Subgenus 1. _Hexastylanthus_, Haeckel. + +_Definition._--Pores regular or subregular, of nearly equal size and form; +surface of the cortical shell smooth, without radial by-spines (other than +the six main spines). + + +1. _Hexastylus phaenaxonius_, n. sp. (Pl. 21, fig. 3). + +Shell thin walled, with smooth surface. Pores subregular, hexagonal, five +to six times as broad as the bars; nine to ten on the radius. Six spines +triangular pyramidal, as long as the radius of the shell, as broad at the +base as one pore. + +_Dimensions._--Diameter of the shell 0.13, pores 0.008 to 0.01, bars +0.0015; length of the spines 0.07, basal breadth 0.008 to 0.012. + +_Habitat._--Central Pacific, Station 272, depth 2600 fathoms. + + +2. _Hexastylus sapientum_, n. sp. + +Shell thin walled, with smooth surface. Pores regular, hexagonal, eight to +ten times as broad as the bars; six to seven on the radius. Six spines +bristle-shaped, longer than the diameter of the shell. (Lattice-work and +spines similar to those of _Heliosphaera actinota_, Monogr. d. Radiol., +Taf. ix. fig. 3.) + +_Dimensions._--Diameter of the shell 0.15, pores 0.016, bars 0.002; length +of the spines 0.2, breadth 0.002. + +_Habitat._--North Atlantic, Station 354, surface. + + +{172}3. _Hexastylus thaletis_, n. sp. (Pl. 21, fig. 4). + +Shell thin walled, with smooth surface. Pores subregular, circular, +hexagonally framed, somewhat funnel-shaped, of the same breadth as the +bars; eight to nine on the radius. Six spines triangular pyramidal, with +prominent edges, as long as the radius, three to four times as broad at the +base as one pore. + +_Dimensions._--Diameter of the shell 0.1, pores and bars 0.005; length of +the spines 0.05, basal breadth 0.02. + +_Habitat._--Tropical Pacific, Station 225, depth 4575 fathoms. + + +4. _Hexastylus favosus_, n. sp. + +Shell thick walled, with smooth surface. Pores regular, circular, +hexagonally framed, deep funnel-shaped, of the same breadth as the bars; +six to seven on the radius. Six spines triangular pyramidal, as long as the +diameter, twice as broad at the base as one pore. + +_Dimensions._--Diameter of the shell 0.12, pores and bars 0.01; length of +the spines 0.12, basal breadth 0.02. + +_Habitat._--South Atlantic, Station 320, surface. + + +5. _Hexastylus longissimus_, n. sp. + +Shell thick walled, with smooth surface. Pores regular, circular, +hexagonally framed, of the same breadth as the bars; five to six on the +radius. Six spines triangular prismatic, extremely elongated, ten to twenty +times as long as the diameter of the shell, twice as broad as one pore. + +_Dimensions._--Diameter of the shell 0.08, pores and bars 0.008; length of +the spines 1.0 to 1.5, breadth 0.015. + +_Habitat._--Tropical Atlantic, Station 347, surface. + + +6. _Hexastylus minimus_, n. sp. (Pl. 21, fig. 5). + +Shell thin walled, with smooth surface. Pores subregular, circular, twice +as broad as the bars; five to six on the radius. Six spines triangular +pyramidal, scarcely as long as the radius, at the base half as broad as +long. + +_Dimensions._--Diameter of the shell 0.05, pores 0.004, bars 0.002; length +of the spines 0.02, basal breadth 0.01. + +_Habitat._--Tropical Pacific, Station 225, depth 4575 fathoms. + + +7. _Hexastylus biantis_, n. sp. + + ? _Haliphormis hexacantha_, Ehrenberg, 1872, L. N. 24, Taf. x. fig. 6. + +Shell thin walled, smooth. Pores regular, circular, four times as broad as +the bars; eight to nine on the radius. Six spines conical, as long as the +radius, at the base as broad as one pore. + +{173}_Dimensions._--Diameter of the shell 0.12, pores 0.012, bars 0.003; +length of the spines 0.06, basal breadth 0.012. + +_Habitat._--Indian Ocean, Madagascar, surface, Rabbe. + + +8. _Hexastylus pittaci_, n. sp. + +Shell thin walled, smooth. Pores regular, circular, ten to twelve times as +broad as the bars; six to seven on the radius. Six spines triangular +pyramidal, as long as the radius, as broad as one pore. + +_Dimensions._--Diameter of the shell 0.12, pores 0.02, bars 0.002; length +of the spines 0.06, basal breadth 0.02. + +_Habitat._--Central Pacific, Station 271, depth 2425 fathoms. + + +9. _Hexastylus maximus_, n. sp. + +Shell thick walled, smooth. Pores regular, circular, twice as broad as the +bars; twelve to sixteen on the radius. Six spines six-sided pyramidal, half +as long as the radius, three times as broad as one pore. + +_Dimensions._--Diameter of the shell 0.3, pores 0.01, bars 0.005; length of +the spines 0.08, basal breadth 0.03. + +_Habitat._--Central Pacific, Station 268, depth 2900 fathoms. + + +10. _Hexastylus periandri_, n. sp. + +Shell thick walled, smooth. Pores regular, circular, double-edged, four +times as broad as the bars; six to seven on the radius. Six spines conical, +as long as the radius, twice as broad as one pore. + +_Dimensions._--Diameter of the shell 0.2, pores 0.012, bars 0.003; length +of the spines 0.1, basal breadth 0.025. + +_Habitat._--Tropical Atlantic, Station 335, depth 1425 fathoms. + + + +Subgenus 2. _Hexastylettus_, Haeckel. + +_Definition._--Pores regular or subregular, of nearly equal size and form; +surface of the spherical shell spiny, covered with numerous conical or +bristle-shaped radial by-spines. + + +11. _Hexastylus solonis_, n. sp. (Pl. 21, fig. 11). + +Shell thick walled, covered with numerous bristle-shaped radial spines +(one-third to one-half as long as the six main spines, arising from the +lattice-knots). Pores regular, circular, enclosed by prominent, hexagonal +frames, four to six times as broad as the bars; seven to eight on the +radius. {174}Six main spines triangular pyramidal, with spirally contorted +prominent edges, as long as the radius, as broad at the base as one pore. + +_Dimensions._--Diameter of the shell 0.13, pores 0.01, bars 0.002; length +of the spines 0.06 to 0.8, basal breadth 0.01. + +_Habitat._--Central Pacific, Station 266, depth 2750 fathoms. + + +12. _Hexastylus cochleatus_, n. sp. (Pl. 21, fig. 1). + +Shell thick walled, covered with numerous short, conical spines (about as +large as one pore). Pores regular, circular, three times as broad as the +bars; eight to nine on the radius. Six main spines triangular pyramidal, +with prominent, spirally-twisted edges, as long as the diameter of the +shell, and twice as broad at the base as one pore. + +_Dimensions._--Diameter of the shell 0.17, pores 0.015, bars 0.005; length +of the spines 0.16, breadth 0.03. + +_Habitat._--Mediterranean, Corfu, Haeckel, surface. + + +13. _Hexastylus setosus_, Haeckel. + + _Acanthosphaera setosa_, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. + Berlin, p. 285, Taf. ix. fig. 11. + +Shell thin walled, covered with numerous short, bristle-shaped spines (not +larger than one pore). Pores regular, circular, four times as broad as the +bars; thirteen to sixteen on the radius. Six main spines three-sided +pyramidal, scarcely one-third as long as the radius. (In the figure of +Ehrenberg, _loc. cit._, only four spines are in regular, crossed +disposition, two others opposite in oblique direction; this is either an +individual abnormality, or an error of drawing; the same species occurs +with six spines exactly regularly disposed in the three dimensive axes.) + +_Dimensions._--Diameter of the shell 0.15; pores 0.008, bars 0.002; length +of the spines 0.02 to 0.03, basal breadth 0.005. + +_Habitat._--Indian Ocean, Zanzibar, Pullen; Madagascar, Rabbe. + + +14. _Hexastylus chilonis_, n. sp. + +Shell thin walled, covered with numerous bristle-shaped spines (as long as +the radius). Pores regular, circular, twice as broad as the bars; eight to +nine on the radius. Six main spines triangular pyramidal, with straight +edges, as long as the diameter of the shell, as broad as two pores. + +_Dimensions._--Diameter of the shell 0.2, pores 0.02, bars 0.01; length of +the spines 0.2, basal breadth 0.05. + +_Habitat._--South Atlantic, Station 325, surface. + + +15. _Hexastylus cleobuli_, n. sp. + +Shell thick walled, covered with numerous short, conical spines (twice as +large as one pore). Pores regular, circular, of the same breadth as the +bars; twelve to thirteen on the radius. Six main spines conical, as long as +the radius, three times as broad as one pore. + +{175}_Dimensions._--Diameter of the shell 0.24, pores and bars 0.005; +length of the spines 0.12, basal breadth 0.016. + +_Habitat._--South Pacific, Station 300, depth 1375 fathoms. + + + +Subgenus 3. _Hexastylissus_, Haeckel. + +_Definition._--Pores irregular, of unequal size or form; surface of the +spherical shell smooth, without radial by-spines (other than the six main +spines). + + +16. _Hexastylus triaxonius_, n. sp. (Pl. 21, fig. 2). + +Shell thin walled, with smooth surface. Pores irregular, polygonal, three +to six times as broad as the bars; four to six on the radius. Six spines +triangular pyramidal, as long as the diameter of the shell, as broad at the +base as one pore. + +_Dimensions._--Diameter of the shell 0.05, pores 0.004 to 0.008, bars +0.0015; length of the spines 0.04, basal breadth 0.006. + +_Habitat._--North Pacific, Station 253, depth 3125 fathoms. + + +17. _Hexastylus dimensivus_, n. sp. (Pl. 21, fig. 6). + +Shell thin walled, with smooth surface. Pores irregular, polygonal, four to +eight times as broad as the bars; eleven to thirteen on the radius. Six +spines hexagonal pyramidal, as long as the radius, about three times as +broad at the base as one pore. + +_Dimensions._--Diameter of the shell 0.13, pores 0.006 to 0.009, bars +0.0012; length of the spines 0.06, basal breadth 0.025. + +_Habitat._--North Pacific, Station 256, depth 2950 fathoms. + + +18. _Hexastylus brevispinus_, n. sp. + +Shell thin walled, with smooth surface. Pores irregular, roundish, two to +four times as broad as the bars; six to eight on the radius. Six spines +triangular pyramidal, half as long as the radius, twice as broad as one +pore. + +_Dimensions._--Diameter of the shell 0.2, pores 0.008 to 0.016, bars 0.004; +length of the spines 0.05, basal breadth 0.025. + +_Habitat._--Central Pacific, Station 268, depth 2900 fathoms. + + +19. _Hexastylus longispinus_, n. sp. + +Shell thick walled, smooth. Pores irregular, roundish, two to three times +as broad as the bars; three to four on the radius. Six spines triangular +prismatical, two to three times as long as the diameter of the shell. + +{176}_Dimensions._--Diameter of the shell 0.08, pores 0.008 to 0.012, bars +0.004; length of the spines 0.2, breadth 0.01. + +_Habitat._--North Atlantic, Station 353, surface. + + +20. _Hexastylus marginatus_, n. sp. (Pl. 21, fig. 10). + +Shell thick walled, rough. Pores irregular, roundish, somewhat +funnel-shaped double-edged, two to three times as broad as the bars; twelve +to fourteen on the radius. Six spines three-sided pyramidal, somewhat +longer than the radius, three times as broad as one pore. + +_Dimensions._--Diameter of the shell 0.15, pores 0.007 to 0.01, bars 0.004; +length of the spines 0.1, basal breadth 0.025. + +_Habitat._--South Pacific, Station 295, depth 1500 fathoms. + + +21. _Hexastylus conifer_, n. sp. + +Shell thick walled, rough. Pores irregular, roundish, scarcely broader than +the bars; fifteen to sixteen on the radius. Six spines conical, as long as +the radius, five to seven times as broad as one pore. + +_Dimensions._--Diameter of the shell 0.18, pores and bars 0.004 to 0.006; +length of the spines 0.1, basal breadth 0.03. + +_Habitat._--Indian Ocean, Sunda Strait, Rabbe, surface. + + + +Subgenus 4. _Hexastylurus_, Haeckel. + +_Definition._--Pores irregular, of unequal size or form; surface of the +spherical shell spiny, covered with numerous conical or bristle-shaped +by-spines. + + +22. _Hexastylus dictyotus_, n. sp. (Pl. 21, figs. 8, 9). + +Shell thin walled, spiny; short spines conical, smaller than the +pore-breadth. Pores irregular, polygonal, five to seven times as broad as +the bars; four to six on the radius. Six spines triangular pyramidal, +longer than the radius, about as broad as one smaller pore. + +_Dimensions._--Diameter of the shell 0.09, pores 0.01 to 0.015, bars 0.002; +length of the spines 0.06, basal breadth 0.01. + +_Habitat._--Central Pacific, Station 272, depth 2600 fathoms. + + +23. _Hexastylus hirsutus_, n. sp. + +Shell thin walled, densely covered with bristle-shaped, radial spines, half +as long as the six main spines. Pores irregular, polygonal, three to four +times as broad as the bars; eight to ten on the radius. Six spines +triangular pyramidal, as long as the radius, twice as broad as one pore. + +{177}_Dimensions._--Diameter of the shell 0.14, pores 0.005 to 0.008, bars +0.002; length of the spines 0.06, basal breadth 0.01. + +_Habitat._--Central Pacific, Station 271, depth 2425 fathoms. + + +24. _Hexastylus contortus_, n. sp. (Pl. 21, fig. 12). + +Shell thick walled, covered with bristle-shaped, radial spines, half as +long as the radius. Pores irregular, roundish, two to three times as broad +as the bars; seven to eight on the radius. Six spines triangular prismatic, +in the distal half spirally twisted like a cork-screw (fig. 12); longer +than the diameter of the shell, about as broad as one pore. + +_Dimensions._--Diameter of the shell 0.12, pores 0.006 to 0.008, bars +0.003; length of the spines 0.15, breadth 0.015. + +_Habitat._--Central Pacific, Station 265, depth 2900 fathoms. + + +25. _Hexastylus spiralis_, n. sp. (Pl. 21, fig. 7). + +Shell thick walled, covered with short conical spines. Pores irregular, +roundish, two to three times as broad as the bars; five to six on the +radius. Six spines triangular prismatic, with three thin, spirally +contorted edges, two to three times as long as the diameter of the shell, +about as broad as one large pore. + +_Dimensions._--Diameter of the shell 0.16, pores 0.01 to 0.02, bars 0.006; +length of the spines 0.3 to 0.5, basal breadth 0.02. + +_Habitat._--Tropical Western Pacific, Station 225, depth 4475 fathoms. + + + +Genus 73. _Hexastylarium_,[102] n. gen. + +_Definition._--#Cubosphaerida# with one simple lattice-sphere and six +simple spines of different sizes; one opposite pair larger than the other +two. + +The genus _Hexastylarium_ differs from its probable ancestral form, +_Hexastylus_, by the unequal growth of the six simple spines; two opposite +spines of one pair being more strongly developed than the four others, +which are equal. They correspond therefore to the three axes of a quadratic +crystal. + + +1. _Hexastylarium heteraxonium_, n. sp. + +Cortical shell thin walled, smooth, with regular, hexagonal pores, three +times as broad as the bars; eight to ten on the radius. Six spines +three-sided pyramidal, at the base as broad as one pore. Two opposite major +spines longer than the shell diameter; four others scarcely as long as +{178}the radius. (Similar to _Hexastylus phaenaxonius_, Pl. 21, fig. 3, but +differing in the unequal length of the spines.) + +_Dimensions._--Diameter of the shell 0.15, pores 0.12, bars 0.004; length +of the two major spines 0.2, of the four minor 0.07. + +_Habitat._--Central Pacific, Station 265, depth 2900 fathoms. + + +2. _Hexastylarium quadratum_, n. sp. + +Shell very delicate, with smooth surface, and irregular, polygonal pores, +separated by very thin bars. The form of the shell is not, as commonly, a +sphere, but a geometrical square octahedron, one axis (with two opposite +major spines) being nearly twice as long as the other two dimensive axes; +four spines, opposite by pairs in the latter, are only half as long. The +eight sides of the octahedral shell are even, equilateral-triangular. +Spines angular, thin. + +_Dimensions._--Diameter of the shell in the major axis 0.18, in the minor +0.1; length of the major spines 0.24, minor 0.12. + +_Habitat._--South Pacific, Station 295, depth 1500 fathoms. + + +3. _Hexastylarium elongatum_, n. sp. + +Shell thick walled, with spiny surface, and with irregular, roundish pores, +two to four times as broad as the bars; eight to ten on the radius. Two +opposite major spines, three to four times as long as the shell diameter, +whilst the four other spines are very short, scarcely as long as the +radius. All six spines at the base three-sided pyramidal, the two longer +being cylindrical. + +_Dimensions._--Diameter of the shell 0.1; length of the major spines 0.3 to +0.4, of the minor 0.04, basal breadth 0.02. + +_Habitat._--North Pacific, Station 244, surface. + + + +Genus 74. _Hexastylidium_,[103] Haeckel, 1881, Prodromus, p. 450. + +_Definition._--#Cubosphaerida# with one simple lattice-sphere and six +simple spines in pairs different; the two opposite spines of each pair +equal, the three pairs unequal. + +The genus _Hexastylidium_ differs from its probable ancestral form, +_Hexastylus_, by the unequal growth of the six simple spines; the two +spines of each pair reaching the same dimensions, whilst the three pairs +are different. They correspond therefore to the three axes of a rhombic +crystal. + + +1. _Hexastylidium rhomboides_, n. sp. + +Shell thin walled, smooth, with irregular, polygonal pores and very thin +bars. Its form is not, as commonly, a sphere, but a rhombic octahedron. The +radial proportion of the three unequal {179}dimensive axes = 1 : 2 : 4. The +radial proportion of the three pairs of spines = 1 : 3 : 8. Spines thin +cylindrical, at the base angular. + +_Dimensions._--Diameter of the major shell axis 0.2, middle 0.1, minor +0.05; length of the major spines 0.3, middle 0.12, minor 0.04. + +_Habitat._--Indian Ocean, Madagascar, Rabbe, surface. + + +2. _Hexastylidium spirale_, n. sp. + +Shell thick walled, spherical, thorny, with irregular, roundish pores, +three to five times as broad as the bars; six spines very stout, prismatic +(as broad as one large pore), with three ring-like, spirally convoluted +edges. Two opposite major spines of extraordinary length, ten to twelve +times as long as the shell diameter, the two middle opposite spines being +about as long as the latter, the two minor scarcely one-third as long. +(Similar to _Hexastylus spiralis_, Pl. 21, fig. 7, but distinguished by the +very unequal length of the spines.) + +_Dimensions._--Diameter of the shell 0.12; length of the major spines 1 to +1.5 mm., middle 0.15, minor 0.04. + +_Habitat._--Central Pacific, Station 266, surface. + + + +Subfamily HEXALONCHIDA,[104] Haeckel, 1881, Prodromus, pp. 449, 451. + +_Definition._--#Cubosphaerida# with two concentric spherical +lattice-shells. + + + +Genus 75. _Hexalonche_,[105] Haeckel, 1881, Prodromus, p. 451. + +_Definition._--#Cubosphaerida# with two concentric lattice-spheres and six +simple spines of equal size. + +The genus _Hexalonche_ is the most simple form, and probably the common +ancestral form, of all Hexalonchida, or those Cubosphaerida which possess +two concentric latticed spheres, connected by six radial beams. Commonly +one shell is intracapsular (medullary shell) and the other extracapsular +(cortical shell); but sometimes also both shells are extracapsular, and +these forms may perhaps be better separated as a peculiar genus +_Hexadilemma_. In _Hexalonche_ all six simple spines are of equal size, and +opposite by pairs in three equal dimensive axes, corresponding to the three +equal axes of a tesseral crystal. It can be derived from _Hexastylus_ by +duplication of the lattice-shell. + + + +Subgenus 1. _Hexalonchara_, Haeckel. + +_Definition._--Pores of the cortical shell regular or subregular, of nearly +equal size and similar form; surface smooth, without radial by-spines +(other than the six main spines). + + +{180}1. _Hexalonche phaenaxonia_, n. sp. + +Cortical shell thin walled, smooth; its pores regular, hexagonal, six to +eight times as broad as the bars; eight to ten to twelve on the radius. +Medullary shell one-third as broad, with regular, hexagonal pores of half +size. Six spines triangular pyramidal, as long as the radius of the shell, +at the base as broad as one pore. (Differs from _Hexastylus phaenaxonius_, +Pl. 21, fig. 3, only in the medullary shell and the six inner radial beams, +connecting it with the cortical shell.) + +_Dimensions._--Diameter of the outer shell 0.15, pores 0.01 to 0.015, bars +0.015 to 0.02; inner shell 0.05; length of the spines 0.08, basal breadth +0.01. + +_Habitat._--Central Pacific, Stations 266 to 271, depth 2425 to 2925 +fathoms. + + +2. _Hexalonche rosetta_, n. sp. (Pl. 25, figs. 3, 3_a_, 3_b_). + +Cortical shell thick walled, smooth, two and a half time as broad as the +medullary shell. Pores of the latter (fig. 3_a_) regular circular; eight to +ten on the half meridian, about as broad as the bars between them. Pores of +the outer shell regular, hexagonal, remarkable for a very peculiar form and +arrangement. In the transverse section of the shell (fig. 3_b_) they appear +as narrow, hexagonal prismatic canals, twice as high as broad, and four to +five times as broad as the thin elevated bars between them. Every seven +meshes form together a larger, regular hexagon (six pores surrounding one +central pore). The periphery of these larger, rosette-like hexagons +projects more strongly from the surface than the walls between the smaller +hexagons. On the half meridian of the shell may be counted six to seven +larger and eighteen to twenty smaller hexagons. The six radial beams +between the two shells are thin, three-sided prismatic, not broader than +the bars of the network, the prominent prolongations of which form six very +strong spines of peculiar club-like shape (fig. 3), as long as the radius +of the outer shell. The three wings of the club are lower in the inner, +higher in the outer half; the broadest part of the spine (at the base and +in the outer third) is as broad as a hexagonal rosette (equal to three +meshes of the outer shell); its outer apex is pyramidal. + +_Dimensions._--Diameter of the outer shell 0.13, pores 0.008 to 0.01, bars +0.02; inner shell 0.05; length of the spines 0.07, distal breadth 0.03. + +_Habitat._--Tropical West Pacific, Station 225, depth 4475 fathoms. + + +3. _Hexalonche favosa_, n. sp. + +Cortical shell thick walled, smooth, four times as broad as the medullary +shell. Pores of the former regular circular, hexagonally framed, deep +funnel-shaped, of the same breadth as the bars; six to eight on the radius. +Six spines triangular-pyramidal, as long as the radius, at the base twice +as broad as one pore. (Differs from the similar _Hexastylus favosus_ mainly +in the possession of a medullary shell.) + +_Dimensions._--Diameter of the outer shell 0.16, pores and bars 0.012; +inner shell 0.04; length of the spines 0.08, basal breadth 0.025. + +_Habitat._--Equatorial Atlantic, Station 348, depth 2450 fathoms; also +fossil in Barbados. + + +{181}4. _Hexalonche octahedra_, n. sp. (Pl. 22, figs. 8, 8_a_). + +Cortical shell a regular octahedron, thin walled, with twelve more or less +rounded edges (between the bases of the spines), and with smooth surface, +three times as broad as the spherical medullary shell. Pores of the former +regular circular (three times as large as those of the latter), four times +as broad as the bars; five to seven on the radius. Six spines three-sided +prismatic, with thickened base and cuspidated end, somewhat longer than the +radius, and once to twice as broad as one pore. + +_Dimensions._--Diameter of the outer shell 0.11, pores 0.01, bars 0.0025; +inner shell 0.04; length of the spines 0.08, bars 0.01. + +_Habitat._--Central Pacific, Station 272, depth 2600 fathoms. + + +5. _Hexalonche conicornis_, n. sp. (Pl. 22, fig. 2). + +Cortical shell thick walled, smooth, three times as broad as the medullary +shell. Pores of both spheres regular circular, three to four times as broad +as the bars; those of the thick walled outer shell six to seven on the +radius, twice as large as those of the thin walled inner shell; six radial +beams between the two spheres, very thin, cylindrical; six spines short, +conical, scarcely as long as the radius of the outer shell, at the base +twice as broad as one pore. + +_Dimensions._--Diameter of the outer shell 0.12 to 0.14, pores 0.01, bars +0.003; inner shell 0.04 to 0.05; length of the spines 0.04 to 0.06, basal +breadth 0.02. + +_Habitat._--Central Pacific, Station 268, depth 2900 fathoms. + + +6. _Hexalonche curvicornis_, n. sp. (Pl. 25, fig. 4). + +Cortical shell thick walled, smooth, not much larger than the medullary +shell (= 4 : 3). Pores of both spheres regular circular, nearly of the same +size, three times as broad as the bars between them; seven to nine on the +radius. Six spines three-sided prismatic, inside and outside of the +exterior shell of equal thickness, twice as broad as one pore, longer than +the diameter of the outer shell, and in a singular manner curved like an ox +horn; the three edges of each horn somewhat spirally twisted. + +_Dimensions._--Diameter of the outer shell 0.16, pores 0.01, bars 0.003; +inner shell 0.12; length of the spines 0.2, breadth 0.02. + +_Habitat._--Central Pacific, Station 266, depth 2750 fathoms. + + +7. _Hexalonche brevicornis_, n. sp. + +Cortical shell thin walled, smooth, three times as broad as the medullary +shell. Pores of the former regular circular, double-edged, six to eight +times as broad as the thin bars, five to six on the radius. Six spines +triangular pyramidal, as broad as one pore and only twice as long. + +_Dimensions._--Diameter of the outer shell 0.14, pores 0.02, bars 0.003; +inner shell 0.045; length of the spines 0.05, basal breadth 0.02. + +_Habitat._--North Pacific, Station 253, depth 3125 fathoms. + + +{182}8. _Hexalonche grandis_, n. sp. + +Cortical shell thick walled, smooth, four times as broad as the medullary +shell. Pores of the outer shell regular circular, four times as broad as +the bars; thirteen to fifteen on the radius. Six spines conical, scarcely +half as long as the radius, at the base as broad as one pore. + +_Dimensions._--Diameter of the outer shell 0.2 to 0.32, pores 0.01 to 0.02, +bars 0.003 to 0.005; inner shell 0.06 to 0.08; length of the spines 0.06, +breadth 0.02. + +_Habitat._--Central Pacific, Station 268, depth 2900 fathoms. + + + +Subgenus 2. _Hexalonchetta_, Haeckel. + +_Definition._--Pores of the cortical shell regular or subregular, of nearly +equal size and similar form; surface covered with numerous conical or +bristle-shaped radial by-spines. + + +9. _Hexalonche amphisiphon_, n. sp. (Pl. 25, figs. 2, 2_a_, 2_b_). + +Cortical shell thin walled, armed with very numerous bristle-shaped, radial +by-spines, a quarter to a half as long as the six main spines. Pores +regular hexagonal, twelve to fourteen on the radius, with very thin bars, +prolonged on the outer as well as the inner surface into a short truncated +conical tube (Pl. 25, fig. 2_b_). Medullary shell octahedral, with +irregular polygonal meshes and very thin bars between them (fig. 2_a_), +connected with the outer (six to eight times larger) shell by six very thin +radial beams. These are prolonged outside into six strong pyramidal spines, +nearly as long as the diameter of the outer shell, with sharp straight +edges, at the base twice as broad as one pore. + +_Dimensions._--Diameter of the outer shell 0.15, pores 0.01, bars 0.001; +inner shell 0.02; length of the spines 0.12, basal breadth 0.02. + +_Habitat._--Central Pacific, Station 271, surface. + + +10. _Hexalonche anaximandri_, n. sp. (Pl. 22, fig. 5). + +Cortical shell thin walled, covered with short conical spines (smaller than +the pores), three times as broad as the medullary shell. Pores of the outer +shell subregular hexagonal, four times as broad as the bars; five to seven +on the radius. Inner shell with regular hexagonal pores of half the size, +connected with the outer by six strong, three-sided prismatic beams, which +are prolonged outside into six very stout pyramidal spines, with three +prominent edges, longer than the radius and twice as broad as one pore. + +_Dimensions._--Diameter of the outer shell 0.12, pores 0.01, bars 0.0025; +inner shell 0.04; length of the spines 0.07, basal breadth 0.02. + +_Habitat._--Central Pacific, Station 272, depth 2600 fathoms. + + +{183}11. _Hexalonche octocolpa_, n. sp. (Pl. 22, figs. 6, 6_a_). + +Cortical shell thin walled, nearly octahedral, with eight hemispherical or +bosom-shaped vaultings, corresponding to the eight faces of a regular +octahedron, the three axes of which are indicated by the six spines. +Surface covered with short bristle-shaped spines. Pores regular hexagonal, +ten to fifteen times as broad as the thin bars; seven to nine on the +radius. Medullary shell (fig. 6_a_) spherical, with regular circular pores, +one-third as broad as the cortical shell, and connected with it by six +strong triangular radial beams, which are prolonged outside into pyramidal +spines, one-third as long as the shell diameter. + +_Dimensions._--Diameter of the outer shell 0.2, pores 0.03, bars 0.002; +inner shell 0.06; length of the spines 0.06, breadth 0.02. + +_Habitat._--Central Pacific, Station 274, depth 2750 fathoms. + + +12. _Hexalonche cristata_, n. sp. + +Cortical shell thick walled, four times as broad as the medullary shell, +and covered with short conical spines arising from the nodal points of +elevated crests which form regular hexagonal frames around the +funnel-shaped circular pores. These are two to three times as broad as the +crested bars; eight to ten on the radius. Six spines three-sided pyramidal, +with strong prominent edges, about as long as the radius of the shell. + +_Dimensions._--Diameter of the outer shell 0.16 to 0.2, pores 0.01 to +0.015, bars 0.003 to 0.005; inner shell 0.04 to 0.05; length of the spines +0.08 to 0.12, basal breadth 0.01 to 0.03. + +_Habitat._--Central Pacific, Station 266 to 274, depth 2350 to 2925 +fathoms. + + +13. _Hexalonche serrata_, n. sp. + +Cortical shell thick walled, four times as broad as the medullary shell, +with spiny surface. Pores regular circular, twice as broad as the bars, +five to seven on the radius, funnel-shaped, separated by hexagonal frames, +the sharp crests of which are serrated; at the nodal-points longer +bristle-shaped by-spines. Six main spines triangular prismatic, longer than +the diameter of the shell, twice as broad as one pore. + +_Dimensions._--Diameter of the outer shell 0.15, pores 0.01, bars 0.005; +inner shell 0.04; length of the spines 0.2, breadth 0.02. + +_Habitat._--South Atlantic, Station 332, depth 2200 fathoms. + + +14. _Hexalonche anaximenis_, n. sp. (Pl. 25, fig. 5). + +Cortical shell thin walled, twice as broad as the medullary shell, and +covered with short conical by-spines. Pores regular circular, twice as +broad as the bars; five to six on the radius. Circular pores of the +medullary shell one-third as broad. Radial main spines conical, nearly as +long as the radius of the shell. + +_Dimensions._--Diameter of the outer shell 0.1, pores 0.01, bars 0.005; +inner shell 0.05; length of the spines 0.04, basal breadth 0.015. + +_Habitat._--Central Pacific, Station 272, depth 2600 fathoms. + + +{184}15. _Hexalonche aspera_, n. sp. + +Cortical shell thin walled, three times as broad as the medullary shell, +and covered with short conical spines. Pores regular circular, four to six +times as broad as the bars; eight to ten on the radius. Radial spines +conical, about as long as the diameter of the shell. + +_Dimensions._--Diameter of the outer shell 0.12, pores 0.08, bars 0.0015; +inner shell 0.04; length of the spines 0.1, basal breadth 0.02. + +_Habitat._--South Pacific, Station 300, depth 1375 fathoms. + + +16. _Hexalonche castanella_, n. sp. + +Cortical shell thick walled, five times as broad as the medullary shell, +and covered with numerous short conical spines. Pores regular circular, +twice as broad as the bars; ten to twelve on the radius. Radial spines +triangular pyramidal, about as long as the radius of the shell. + +_Dimensions._--Diameter of the outer shell 0.22, pores 0.01, bars 0.005; +inner shell 0.045; length of the spines 0.12, basal breadth 0.02. + +_Habitat._--North Atlantic, Station 353, depth 3125 fathoms. + + + +Subgenus 3. _Hexalonchilla_, Haeckel. + +_Definition._--Pores of the cortical shell irregular, of unequal size or +form; surface smooth, without radial by-spines (other than the six main +spines). + + +17. _Hexalonche hexacantha_, Haeckel. + + _Haliomma hexacanthum_, J. Mueller, 1858, Abhandl. d. k. Akad. d. Wiss. + Berlin, p. 35, Taf. iv. fig. 5. + + _Haliomma hexacanthum_, Haeckel, 1862, Monogr. d. Radiol., p. 430. + +Cortical shell thin walled, smooth, with irregular polygonal pores +(commonly hexagonal or pentagonal), two to three times as broad as the +bars; eight to ten on the radius. Medullary shell one quarter as broad, +connected with the former by six thin radial beams which are prolonged +outside into six triangular pyramidal spines (not quadrangular, as Mueller +describes), longer than the radius of the shell. + +_Dimensions._--Diameter of the outer shell 0.2, pores 0.01 to 0.015, bars +0.005; inner shell 0.05; length of the spines 0.15, basal breadth 0.015. + +_Habitat._--Mediterranean (Messina, Nice, Genoa). + + +18. _Hexalonche geometrica_, n. sp. + +Cortical shell thick walled, smooth, with very peculiar geometrical +formation of its network, the pores of which are of very different size and +form, but highly regular disposition. Each of the six {185}triangular +spines is surrounded at the base by three small roundish pores (between the +three wings of its base), and further by a coronal of six very large pores, +three of which are pentagonal, and the other three (alternating) +heptagonal. The six basal coronals are separated by irregular smaller +pores. Medullary shell thin walled, with regular hexagonal pores (three on +the radius) and thin bars, connected with the outer shell by six thin +triangular prismatic radial beams, which are prolonged outside into short +pyramidal spines (half as long as the radius). + +_Dimensions._--Diameter of the outer shell 0.2, thirty-six larger pores of +the coronals 0.03 to 0.04, smaller pores between them 0.01 to 0.02, bars +0.005; inner shell 0.05 (with pores of 0.008); length of the spines 0.05, +basal breadth 0.03. + +_Habitat._--South Atlantic, off Buenos Ayres, Station 323, depth 1900 +fathoms. + + +19. _Hexalonche pythagoraea_, n. sp. (Pl. 22, fig. 1). + +Cortical shell thick walled, smooth, three times as broad as the medullary +shell. Pores irregular roundish, twice to eight times as broad as the bars, +of very different size; usually in the space between every three spines are +three or six larger pores, separated by numerous smaller pores (often the +disposition of the larger pores is much more regular than in the figured +specimen). Medullary shell with regular circular pores, connected with the +outer by six very thin radial beams, which are prolonged outside into six +short triangular pyramidal spines about as long and broad as the half +radius. + +_Dimensions._--Diameter of the outer shell 0.12, pores 0.008 to 0.03, bars +0.004; inner shell 0.04; length of the spines 0.04, basal breadth 0.03. + +_Habitat._--Central Pacific, Station 271, depth 2425 fathoms. + + +20. _Hexalonche aristarchi_, n. sp. (Pl. 22, fig. 3). + +Cortical shell thin walled, smooth, four times as broad as the medullary +shell. Pores irregular polygonal, of very variable size and form, twice to +six times as broad as the bars; six to ten on the radius. Medullary shell +with regular hexagonal pores, connected with the outer by six very thin +radial beams, which are prolonged outside into six triangular pyramidal +spines, nearly as long as the radius. + +_Dimensions._--Diameter of the outer shell 0.1, pores 0.005 to 0.02, bars +0.003; inner shell 0.025; length of the spines 0.05, basal breadth 0.01. + +_Habitat._--North Pacific, Station 241, depth 2300 fathoms. + + +21. _Hexalonche ekphantaea_, n. sp. + +Cortical shell thin walled, smooth, four times as broad as the medullary +shell. Pores irregular roundish, of very variable size and form, twice to +six times as broad as the bars, ten to fifteen on the radius. Six spines +cylindro-conical, longer than the diameter of the shell. + +_Dimensions._--Diameter of the outer shell 0.2, pores 0.004 to 0.012, bars +0.002; inner shell 0.05; length of the spine 0.3, basal breadth 0.01. + +_Habitat._--Indian Ocean, Sunda Strait, surface, Rabbe. + + + +{186}Subgenus 4. _Hexalonchusa_, Haeckel. + +_Definition._--Pores of the cortical shell irregular, of different size or +form; surface covered with numerous conical or bristle-shaped, radial +by-spines. + + +22. _Hexalonche philosophica_, n. sp. (Pl. 22, fig. 4). + +Cortical shell thin walled, covered with short conical spines, three times +as broad as the medullary shell. Pores irregular polygonal, or more +roundish, twice to six times as broad as the bars; six to eight on the +radius. Inner shell of the same structure, pores three times smaller, +connected with the outer by six very thin radial beams, which are prolonged +outside into six strong, triangular pyramidal spines, as long as the +radius. (Similar to _Hexalonche anaximandri_, Pl. 22, fig. 5, but different +in the irregular network and the shorter by-spines.) + +_Dimensions._--Diameter of the outer shell 0.11, pores 0.005 to 0.015, bars +0.0025; inner shell 0.04; length of the spines 0.06, breadth 0.02. + +_Habitat._--North Atlantic, Faeroee Channel, John Murray; Iceland, Krabbe, +surface. + + +23. _Hexalonche seleuci_, n. sp. + +Cortical shell thick walled, covered with numerous short, bristle-shaped +spines. Pores of very different size and form, and of a peculiar, +subregular disposition, similar to those of _Hexalonche geometrica_ (though +in this case more regular). Each of the six triangular main spines (which +reach nearly the length of the radius) is surrounded at the base by three +small roundish pores, and these are further supplemented by a coronal of +six very large polygonal pores; the six coronals are separated by irregular +rows of smaller pores. Inner shell equal to one-third of the outer. Six +main spines pyramidal, as long as the radius. + +_Dimensions._--Diameter of the outer shell 0.16, larger pores 0.03 to 0.04, +smaller pores 0.01 to 0.02, bars 0.05 to 0.01; inner shell 0.05; length of +the spines 0.08, basal breadth 0.03. + +_Habitat._--North Atlantic, Station 354, surface. + + +24. _Hexalonche sexaculeata_, Haeckel. + + _Haliomma sexaculeatum_, Stoehr, 1880, Palaeontogr., vol. xxvi. p. 87, + Taf. i. fig. 8. + +Cortical shell thick walled, twice as broad as the medullary shell, and +covered with short conical spines. Pores irregular polygonal (mostly +hexagonal), twice to three times as broad as the bars; six to eight on the +radius. Six spines triangular-pyramidal (not quadrangular), somewhat longer +than the radius of the shell. + +_Dimensions._--Diameter of the outer shell 0.11, pores 0.06 to 0.08, bars +0.03; inner shell 0.06; length of the spines 0.07, basal breadth 0.015. + +_Habitat._--Fossil in Tertiary rocks of Sicily, Grotte, Caltanisetta. + + +{187}25. _Hexalonche heracliti_, n. sp. (Pl. 22, fig. 7). + +Cortical shell thick walled, covered with bunches of small spines, each +bunch at the nodule point between every three pores composed of four to +eight conical spinules. Pores irregular roundish, twice to four times as +broad as the bars; four to six on the radius. Inner shell equal to +one-third of the outer, connected with it by six thin radial beams, which +are prolonged outside into six strong triangular spines about as long as +the radius. + +_Dimensions._--Diameter of the outer shell 0.15, pores 0.015 to 0.03, bars +0.08; inner shell 0.05; length of the spines 0.06, basal breadth 0.02. + +_Habitat._--Indian Ocean, Madagascar, Rabbe, surface. + + +26. _Hexalonche xenophanis_, n. sp. + +Cortical shell thin walled, covered with numerous short conical spines, +four times as broad as the medullary shell. Pores irregular circular, twice +to eight times as broad as the bars; five to seven on the radius. Six +spines conical or more cylindrical, as long as the diameter of the shell or +longer. + +_Dimensions._--Diameter of the outer shell 0.16 to 0.24, pores 0.01 to +0.04, bars 0.005; inner shell 0.04 to 0.06; length of the spines 0.2 to +0.3, breadth 0.02. + +_Habitat._--Central Pacific, Stations 266 to 272, surface. + + +27. _Hexalonche setosa_, n. sp. + +Cortical shell thin walled, covered with numerous bristle-shaped spines, +half as long as the six main spines. Pores irregular roundish, twice to +five times as broad as the bars; ten to twelve on the radius. Inner shell +equal to one-fifth of the outer. Six spines conical, as long as the radius. + +_Dimensions._--Diameter of the outer shell 0.25, pores 0.008 to 0.02, bars +0.004; inner shell 0.05; length of the spines 0.12, basal breadth 0.03. + +_Habitat._--South Pacific, Station 291, surface. + + +28. _Hexalonche hystricina_, n. sp. (Pl. 25, fig. 6). + +Cortical shell thick walled, covered with numerous bristle-shaped spines, +half as long as the six main spines. Pores irregular roundish, twice to +four times as broad as the bars; five to seven on the radius. Medullary +shell with very small circular pores, one-fourth of the cortical shell, +connected with it by six thin prismatic radial beams, which are prolonged +outside into six strong, short, three-sided pyramidal, cuspidated spines, +only half as long as the radius of the outer shell. + +_Dimensions._--Diameter of the outer shell 0.2, pores 0.015 to 0.03, bars +0.008; inner shell 0.05; length of the spines 0.05, basal breadth 0.02. + +_Habitat._--Indian Ocean, Sunda Strait, surface, Rabbe. + + + +{188}Genus 76. _Hexancistra_,[106] Haeckel, 1881, Prodromus, p. 451. + +_Definition._--#Cubosphaerida# with two concentric lattice-spheres and six +branched spines of equal size. + +The genus _Hexancistra_ differs from its ancestral form, _Hexalonche_, in +the ramification of the six radial spines. These are very different in the +two subgenera; in _Hexancora_ each spine bears only three simple lateral +branches, while in _Hexapitys_ there are three rows of verticillate lateral +branches on each spine. + + + +Subgenus 1. _Hexancora_, Haeckel. + +_Definition._--Each radial spine with three simple lateral branches only +(one branch from each edge of the triangular spine). + + +1. _Hexancistra tricuspis_, n. sp. (Pl. 22, fig. 9). + +Cortical shell thin walled, covered with short conical by-spines, three +times as broad as the medullary shell; its pores regular circular, three +times as broad as the bars; ten to twelve on the radius. Pores of the +medullary shell half as large, also regular circular. The two shells +connected by six thin prismatic radial beams, which are prolonged outside +into six very stout main spines, three-sided prismatic, as long as the +shell diameter, with three thin wing-like edges. Each edge at the distal +end prolonged into a strong curved lateral branch. + +_Dimensions._--Diameter of the outer shell 0.13, inner 0.4; cortical pores +0.01, bars 0.003; medullary pores 0.005, bars 0.003; length of the six +spines 0.13, breadth 0.02. + +_Habitat._--Central Pacific, Station 266, depth 2750 fathoms. + + +2. _Hexancistra ancorata_, n. sp. + +Cortical shell thick walled, smooth, twice as broad as the medullary shell; +its pores regular circular, twice as broad as the bars; six to eight on the +radius. Six radial spines, three-sided prismatic, as long as the shell +radius, with three recurved lateral branches at the distal end like the +three teeth of an anchor. + +_Dimensions._--Diameter of the outer shell 0.1, inner 0.05; cortical pores +0.006, bars 0.003; length of the six spines 0.05, breadth 0.02. + +_Habitat._--South Pacific, Station 296, depth 1825 fathoms. + + +3. _Hexancistra triserrata_, n. sp. (Pl. 22, fig. 10). + +Cortical shell thin walled, thorny, twice to three times as broad as the +medullary shell; the two shells connected by six strong triangular beams. +Inner shell spherical, with very small, regular, circular {189}pores; ten +to twelve on the half meridian. Bars as broad as the pores. Outer shell +regularly octahedral, with eight triangular perfectly regular even faces, +separated by eight prominent edges; the meshes circular, regular, about +twelve to fourteen on the half meridian, two to three times as broad as the +bars between them. Six strong radial spines, about as long as the diameter +of the outer shell, three-sided prismatic, cuspidate; their three edges +prominent, serrate, spirally twisted. Each spine bears about its middle +three strong flattened lateral branches, nearly perpendicular to it, not +serrated, and slightly curved. + +_Dimensions._--Diameter of the outer shell 0.13, inner 0.045; pores of the +former 0.01, of the latter 0.004; length of the spine 0.12, breadth 0.014. + +_Habitat._--Central Pacific, Station 274, depth 2750 fathoms. + + +4. _Hexancistra quadricuspis_, n. sp. (Pl. 22, fig. 11). + +Cortical shell thin walled, covered with short bristle-shaped by-spines, +three and a half times as broad as the medullary shell. Pores of the latter +regular circular, small; pores of the former three to six times as large, +very irregular, roundish, double-edged. Six radial spines, three-sided +prismatic, about as long as the shell diameter, with three wing-like, +slightly twisted edges, which are prolonged towards the distal end into +three curved horn-shaped branches. + +_Dimensions._--Diameter of the outer shell 0.17, inner 0.05; cortical pores +0.01 to 0.03, bars 0.005; medullary pores 0.003, bars 0.001; length of the +spines 0.15, breadth 0.013. + +_Habitat._--Central Pacific, Station 271, depth 2425 fathoms. + + + +Subgenus 2. _Hexapitys_, Haeckel, 1881, Prodromus, p. 451. + +_Definition._--Each radial spine with three rows of verticillate lateral +branches (a row arising from each edge of the spine). + + +5. _Hexancistra mirabilis_, n. sp. (Pl. 23, fig. 3). + + _Hexapitys mirabilis_, Haeckel, 1881, Prodromus, p. 451. + +Cortical shell very thin walled, three times as broad as the medullary +shell. Inner shell spherical, with very delicate, subregular hexagonal +meshes; seven to eight on the half diameter. Outer shell octahedral, with +irregular polygonal meshes of very different size; on the surface numerous +thin accessory radial spines, equal in length to its radius. Six main +spines, extremely long and stout, many times longer than the diameter of +the outer shell, nearly as broad as the radius of the inner shell, +three-sided prismatic, with sharp, prominent, spirally twisted edges; on +every edge a great number of thin lateral branches, arranged +perpendicularly to it, as long as the diameter of the outer shell, and +pinnated by ten to twenty pairs of delicate secondary spinules, biserial +and perpendicular to the primary branches. (In the figured specimen the +spherical central capsule, between both shells, was well preserved; its +nucleus nearly filled the medullary shell. The thick jelly-veil around it +was radially striped and octahedral.) + +{190}_Dimensions._--Diameter of the outer shell 0.13, of the inner 0.05; +length of the spines 0.5 to 0.8 or more, breadth 0.02. + +_Habitat._--Central Pacific, Station 271, surface. + + + +Genus 77. _Hexaloncharium_,[107] n. gen. + +_Definition._--#Cubosphaerida# with two concentric lattice-spheres and six +simple spines of different sizes; one opposite pair larger than the two +others. + +The genus _Hexaloncharium_ exhibits the same relation to its ancestral +form, _Hexalonche_, that _Hexastylarium_ bears to _Hexastylus_. Two +opposite spines of one pair are larger than the four others, and correspond +to the three axes of a quadratic crystal. + + +1. _Hexaloncharium octahedrum_, n. sp. + +Cortical shell smooth, three to four times as broad as the spherical +medullary shell, each having regular circular pores, twice to three times +as broad as the bars. Form of the outer shell not a sphere, but a regular +octahedron, with eight congruent, equilateral triangular even faces. Two +opposite spines twice as long as the shell diameter, whilst the four others +are scarcely equal to it. Basal breadth of all six the same (three times as +large as one pore); form, three-sided prismatic, with cuspidate distal end. +(Similar to _Hexalonche octahedra_, Pl. 22, fig. 8, but distinct in the +unequal length of the spines.) + +_Dimensions._--Diameter of the outer shell 0.16, inner 0.045; length of the +major spine 0.3, minor 0.12, basal breadth 0.03. + +_Habitat._--South Atlantic, Station 332, depth 2200 fathoms. + + +2. _Hexaloncharium philosophicum_, n. sp. + +Cortical shell spherical, covered with short conical by-spines, twice as +broad as the medullary shell; both with regular circular pores three to +four times as broad as the bars. Two major spines cylindrical, with conical +apex, three times as long as the four others, which are conical and about +as long as the shell radius; basal breadth of all six the same (equal to +one pore). Similar to _Hexalonche anaximenis_ (Pl. 25, fig. 5), but +distinct in the enormous prolongation of two opposite spines. + +_Dimensions._--Diameter of the outer shell 0.12, inner 0.06; length of the +two major spines 0.2, of the four minor 0.06, basal breadth 0.02. + +_Habitat._--Central Pacific, Station 267, depth 2700 fathoms. + + +{191}3. _Hexaloncharium hystricinum_, n. sp. + +Cortical shell spherical, three times as broad as the medullary shell, and +densely covered with oblique bristle-shaped by-spines. Pores irregular +roundish. Two opposite major spines three-sided prismatic, longer than the +shell diameter; four minor spines pyramidal, scarcely half as long as the +shell radius. (Somewhat similar to _Hexalonche hystricina_, but distinct in +the prolongation of two major spines.) + +_Dimensions._--Diameter of the outer shell 0.15, inner 0.05; length of the +two major spines 0.2, four minor 0.03, basal breadth 0.02. + +_Habitat._--South Pacific, Station 288, surface. + + + +Genus 78. _Hexalonchidium_,[108] Haeckel, 1881, Prodromus, p. 451. + +_Definition._--#Cubosphaerida# with two concentric lattice-spheres and six +simple spines of different sizes in pairs; the two opposite spines of each +pair equal, the three pairs unequal. + +The genus _Hexalonchidium_ exhibits the same relation to _Hexalonche_ that +_Hexastylidium_ bears to _Hexastylus_; the growth of the three spine-pairs +is different, whilst both spines of each pair are equal; they correspond +therefore to the three axes of a rhombic crystal. + + +1. _Hexalonchidium axonometrum_, n. sp. + +Cortical shell thin walled, covered with short bristle-shaped by-spines, +twice as broad as the medullary shell; both with regular hexagonal meshes, +twice to three times as broad as the bars (inner meshes half as broad as +the outer). All three spine-pairs three-sided prismatic, of very different +length but of equal breadth (equal to three pores). Major spine-pair twice +as long as the shell diameter; middle pair about equal to the latter, minor +scarcely half as long. (Similar to _Hexalonche anaximandri_, Pl. 22, fig. +5, but distinct in the different length of the spines.) + +_Dimensions._--Diameter of the outer shell 0.12, inner 0.06; length of the +major spines 0.25, middle 0.1, minor 0.04. + +_Habitat._--Indian Ocean, Madagascar, surface, Rabbe. + + + +Subfamily HEXACONTIDA,[109] Haeckel, 1881, Prodromus, pp. 449, 452. + +_Definition._--#Cubosphaerida# with three concentric, spherical, or +octahedral lattice-shells. + + + +{192}Genus 79. _Hexacontium_, Haeckel,[110] 1881, Prodromus, p. 452. + +_Definition._--Shell with three concentric lattice-spheres and six simple +spines of equal size. + +The genus _Hexacontium_, the ancestral form of the Hexacontida, is probably +derived from _Hexalonche_ by duplication of the medullary shell. As in the +latter, all six spines are of equal size, opposite in pairs in the three +dimensive axes, and correspond therefore to the three equal axes of a +tesseral crystal. + + + +Subgenus 1. _Hexacontanna_, Haeckel. + +_Definition._--Pores of the cortical shell regular or subregular, of nearly +equal size and similar form; surface smooth, without radial spines or +papillae (other than the six main spines). + + +1. _Hexacontium phaenaxonium_, n. sp. + +Cortical shell thin walled, smooth; its pores regular hexagonal, six to +nine times as broad as the bars; twelve to sixteen on the radius. Radial +proportion of the three spheres = 1 : 2 : 4. Both medullary shells of the +same structure as the cortical shell, only with smaller pores. The three +spheres connected by six thin radial beams, which are prolonged on the +outside into six strong triangular pyramidal spines, as long as the radius +of the cortical shell, and, at the base, as broad as one of its pores. +(Differs from _Hexastylus phaenaxonius_ and from _Hexalonche phaenaxonia_, +Pl. 21, fig. 3, in the larger size and the triple shell.) + +_Dimensions._--Diameter of the outer sphere 0.2, middle 0.1, inner 0.05; +cortical pores 0.008, bars 0.0012; length of the spines 0.1. + +_Habitat._--Central Pacific, Station 270, surface. + + +2. _Hexacontium axotrias_, n. sp. (Pl. 24, fig. 3). + +Cortical shell thin walled, smooth; its pores regular circular, five to six +times as broad as the bars; eleven to thirteen on the radius. Radial +proportion of the three spheres = 1 : 3 : 8. Outer medullary shell with +hexagonal frames around the regular circular pores (five to six on the +radius). Inner medullary shell with simple small circular pores (three on +the radius). The two outer shells connected by six triangular prismatic +beams, which are prolonged outside to the length of the cortical radius or +more. + +_Dimensions._--Diameter of the outer sphere 0.2, middle 0.07, inner 0.025; +cortical pores 0.016, bars 0.003; length of the spines 0.1 to 0.015, basal +breadth 0.02. + +_Habitat._--North Pacific, Station 253, surface. + + +3. _Hexacontium hexactis_, Haeckel. + + _Actinomma hexactis_, Stoehr, 1880, Palaeontogr., vol. xxvi. p. 91, Taf. + ii. fig. 7. + +Cortical shell thick walled, smooth, or a little rough. Pores regular +circular, of the same breadth as the bars; five to seven on the radius. +Radial proportion of the three spheres {193}= 1 : 3 : 6. Both medullary +shells of the same structure, but with smaller pores. Six spines triangular +pyramidal, nearly as long as the diameter of the outer shell, three times +as broad at the base as one pore. + +_Dimensions._--Diameter of the outer sphere 0.1, middle 0.05, inner 0.016; +cortical pores and bars 0.008; length of the spines 0.08, basal breadth +0.025. + +_Habitat._--Fossil in Tertiary rocks of Sicily, Grotte, Stoehr. + + +4. _Hexacontium laevigatum_, n. sp. (Pl. 24, fig. 6). + +Cortical shell thick walled, quite smooth. Pores regular circular, with +double margins, eight to ten on the radius, of the same breadth as the +smooth bars. Radial proportion of the three spheres = 1 : 2 : 6. All three +spheres connected by six very thin radial beams, which are prolonged +outside into six short, stout, triangular, pyramidal spines, half as long +as the radius of the outer shell. + +_Dimensions._--Diameter of the outer shell 0.13, middle 0.04, inner 0.02; +cortical pores and bars 0.008; length of the spines 0.04, basal breadth +0.02. + +_Habitat._--South Atlantic, Station 332, depth 2200 fathoms. + + +5. _Hexacontium triplosphaerium_, n. sp. + +Cortical shell thick walled, smooth. Pores regular circular, three times as +broad as the bars; ten to twelve on the radius. Radial proportion of the +three spheres = 1 : 3 : 10. Six spines conical, about as long as the radius +of the cortical shell. + +_Dimensions._--Diameter of the outer shell 0.16, middle 0.05, inner 0.016; +cortical pores 0.012, bars 0.004; length of the spines 0.07, basal breadth +0.02. + +_Habitat._--Central Pacific, Station 268, depth 2900 fathoms. + + +6. _Hexacontium octahedrum_, n. sp. + +Cortical shell a regular octahedron, thin walled, with twelve more or less +rounded edges (between the spine-bases) and with smooth surface; its pores +regular circular, five to seven on the radius, four times as broad as the +bars. Radial proportion of the three shells = 1 : 3 : 9. Both medullary +shells spherical, with very small circular pores. Six inner bars very thin; +six outer spines (their prolongations) triangular pyramidal, as long as the +radius of the outer shell. (Differs from _Hexalonche octahedra_, Pl. 22, +fig. 8, almost solely in the duplication of the medullary shell.) + +_Dimensions._--Diameter of the outer shell 0.12, middle 0.04, inner 0.013. + +_Habitat._--Central Pacific, Station 271, depth 2425 fathoms. + + +7. _Hexacontium circumtextum_, n. sp. (Pl. 25, figs. 7, 7_a_). + +Cortical shell double, enclosing a simple medullary shell. Radial +proportion of the three spheres = 3 : 10 : 12. Inner cortical shell very +thick walled, with regular circular, double-edged pores, four times as +broad as the bars; seven to nine on the radius. From each nodal-point +between {194}every six pores arises a small, bristle-shaped, radial spine, +as long as the diameter of one pore. The distal ends of all these spines +are connected by very delicate tangential threads, and consequently form by +their attachment an outer cortical shell, with regular hexagonal meshes and +smooth surface. Six main spines short, three-sided prismatic, scarcely as +long as half the radius of the outer shell. + +_Dimensions._--Diameter of the outer shell 0.12, middle 0.1, inner 0.03; +pores of the middle shell 0.004, bars 0.001; length of the spines 0.025, +basal breadth 0.01. + +_Habitat._--Central Pacific, Station 274, depth 2750 fathoms. + + + +Subgenus 2. _Hexacontella_, Haeckel. + +_Definition._--Pores of the cortical shell regular or subregular, of nearly +equal size and similar form; surface covered with numerous conical or +bristle-shaped, radial spines (other than the six main spines). + + +8. _Hexacontium hexagonale_, n. sp. + +Cortical shell thin walled, bristly, with very delicate network; its pores +regular hexagonal, twelve to sixteen on the radius, ten to twelve times as +broad as the thin thread-like bars. At each nodal-point of the network +(between every three meshes) arises a bristle-shaped, radial spine, as long +as the diameter of one mesh. Six main spines hexagonal, as long as the +radius of the outer shell, as broad at its base as one mesh. Radial +proportion of the three spheres = 1 : 2 : 4. Pores of both medullary shells +also regular hexagonal, but much smaller, in the middle shell eleven to +twelve, in the inner, six to seven on the half meridian. + +_Dimensions._--Diameter of the outer shell 0.12, of the middle 0.06, of the +inner 0.03; meshes of the outer shell 0.008; length of the six spines 0.05, +basal thickness 0.008. + +_Habitat._--Indian Ocean, Ceylon, surface, Haeckel. + + +9. _Hexacontium favosum_, n. sp. (Pl. 24, figs. 2, 2_a_). + +Cortical shell very thick walled, spiny, with regular, honeycomb-like +network; its meshes funnel-shaped, with circular inner, hexagonal outer +aperture, twice as broad as the bars; five to seven on the radius. Between +every three meshes (at each corner of the hexagon) arises a short radial +thorn, not so long as the thickness of the shell-wall. Six radial spines +very short and stout, three-sided pyramidal, scarcely half so long as the +radius of the outer shell. Radial proportion of the three spheres = +1 : 2 : 5. Pores of both medullary shells regular, circular, about as broad +as the bars, six to eight on the half meridian. + +_Dimensions._--Diameter of the outer shell 0.1 to 0.12, of the middle 0.04 +to 0.05, of the inner 0.02; meshes of the outer shell 0.008; length of the +six spines 0.2 to 0.3, basal breadth 0.015. + +_Habitat._--Central Pacific, Station 265, depth 2900 fathoms. + + +10. _Hexacontium sceptrum_, n. sp. (Pl. 24, figs. 1, 1_a_). + +Cortical shell thick walled, spiny, with regular, honeycomb-like network; +its meshes funnel-shaped, with circular inner, hexagonal outer aperture, +three to four times as broad as the bars; {195}five to six on the radius. +Between every three meshes arises a short radial thorn, as long as the +thickness of the shell-wall. Six radial spines sceptre-shaped, six-sided, +somewhat constricted towards their middle part, strong, as long as the +radius of the outer shell, as broad as one of its meshes. Radial proportion +of the three spheres = 1 : 2 : 6. Pores of the two inner shells regular +hexagonal, with thin bars, six to eight on the half meridian (fig. 1_a_). + +_Dimensions._--Diameter of the outer shell 0.13, of the middle 0.04, of the +inner 0.02; pores of the outer shell 0.01, of the middle 0.008, of the +inner 0.004; length of the six spines 0.06, basal breadth 0.015. + +_Habitat._--Equatorial Atlantic, Station 347, surface. + + +11. _Hexacontium prionacanthum_, n. sp. (Pl. 24, figs. 7, 7_a_). + +Cortical shell thick walled, thorny; its pores regular circular, with +elevated hexagonal frames six to nine on the radius, twice as broad as the +crest-shaped bars. At each nodal-point of the hexagon arises one short +conical papilla or thorn. Radial proportion of the three spheres = +1 : 3 : 10. Pores of both medullary shells much smaller, regular circular. +Six main spines three-sided prismatic, longer than the radius of the outer +shell, as broad as one of its meshes; their three edges serrated, with ten +to twelve teeth. + +_Dimensions._--Diameter of the outer shell 0.15, middle 0.045, inner 0.015; +cortical pores 0.01, bars 0.005; length of the spines 0.1, breadth 0.012. + +_Habitat._--West Tropical Pacific, Station 225, depth 4475 fathoms. + + +12. _Hexacontium clavigerum_, n. sp. (Pl. 23, fig. 5). + +Cortical shell very thick walled, thorny; its pores regular circular, +hexagonally framed, three times as broad as the bars, nine to twelve on the +radius; between them short conical papillae or thorns arising at the +nodal-points. Radial proportion of the three spheres = 1 : 2 : 5. Outer +medullary shell with regular circular, much smaller pores; connected with +the cortical shell by numerous (twenty to thirty) thin radial beams. Six +main spines very stout, club-shaped, scarcely as long as the radius of the +outer shell, three times as broad as one of its pores, three-sided, with +three to four teeth on each edge. + +_Dimensions._--Diameter of the outer shell 0.2, of the middle 0.08, of the +inner 0.04; cortical pores 0.012, bars 0.004; length of the six spines +0.08, breadth 0.03. + +_Habitat._--South Atlantic, Station 332, depth 2200 fathoms. + + +13. _Hexacontium floridum_, n. sp. (Pl. 24, fig. 4). + +Cortical shell papillose, thick walled. Pores regular, six-lobed, four +times as broad as the bars, five to seven on the radius; each pore with six +(sometimes also five or seven) concave indentations or lobules; between the +pores at the nodal-points arise short conical papillae or thorns. Radial +proportion of the three spheres = 1 : 2 : 3. Radial main spines +pommel-shaped, three-sided prismatic, longer than the radius of the outer +shell, two to three times as broad as one pore. + +{196}_Dimensions._--Diameter of the outer shell 0.12, middle 0.06, inner +0.03; cortical pores 0.012, bars 0.003; length of the six spines 0.08, +breadth 0.03. + +_Habitat._--Central Pacific, Station 266, depth 2750 fathoms. + + +14. _Hexacontium hexaconicum_, n. sp. + +Cortical shell spiny, thick walled. Pores regular circular, of the same +breadth as the bars, ten to twelve on the radius; between them long +bristle-shaped by-spines, half as long as the six main spines. Radial +proportion of the three spheres = 1 : 3 : 9. Six main spines conical, as +long as the radius of the outer shell, four times as broad at the base as +one pore. + +_Dimensions._--Diameter of the outer shell 0.18, middle 0.06, inner 0.02; +cortical pores and bars 0.005; length of the spines 0.1, basal breadth +0.02. + +_Habitat._--Antarctic Sea, Station 157, depth 1950 fathoms. + + +15. _Hexacontium asteracanthion_, Haeckel. + + _Haliomma asteracanthion_, Haeckel, 1860, Monatsber. d. k. preuss. Akad. + d. Wiss. Berlin, p. 816. + + _Actinomma asteracanthion, Haeckel_, 1862, Monogr. d. Radiol., p. 441, + Taf. xxiii. figs. 5, 6. + +Cortical shell thin walled, spiny; its pores circular, without hexagonal +frame (as a rule very regular, but in other specimens more or less +irregular), often very variable in size, three to six times as broad as the +bars, commonly seven to eight on the radius. Radial proportion of the three +spheres = 1 : 2 : 4, or sometimes 1 : 3 : 8. Pores of the two inner shells +also circular, but much smaller; those of the middle shell about half as +broad, those of the inner shell one-fourth to one-sixth as broad as the +pores of the outer shell. Six radial spines strong, three-sided prismatic, +about as long as (or somewhat longer than) the radius of the outer shell, +as broad as one of its large meshes. Accessory spines very numerous and +very thin, bristle-like, usually half as long as the six main spines. (For +the variability of this common species compare my Monograph, p. 442.) + +_Dimensions._--Diameter of the outer shell 0.1 to 0.12, of the middle 0.04 +to 0.06, of the inner 0.02 to 0.03; cortical pores 0.005 to 0.01; length of +the six spines 0.06 to 0.08. + +_Habitat._--Cosmopolitan; Mediterranean, Atlantic, Pacific, surface. + + + +Subgenus 3. _Hexacontosa_, Haeckel. + +_Definition._--Pores of the cortical shell irregular, of different size or +form; surface smooth, without radial by-spines or papillae (other than the +six main spines). + + +16. _Hexacontium axophaenum_, n. sp. + +Cortical shell thin walled, smooth. Pores irregular polygonal, three to +nine times as broad as the bars; seven to ten on the radius. Radial +proportion of the three spheres = 1 : 3 : 8. Both {197}medullary shells +with smaller, irregular roundish pores. Six spines three-sided pyramidal, +longer than the radius of the outer shell, one to two times as broad as one +larger pore. + +_Dimensions._--Diameter of the outer shell 0.12, middle 0.045, inner 0.015; +cortical pores 0.006 to 0.018, bars 0.002; length of the spines 0.06 to +0.12, basal breadth 0.02 to 0.03. + +_Habitat._--Central Pacific, Stations 266 to 272, at various depths. + + +17. _Hexacontium polygonale_, n. sp. + +Cortical shell thick walled, smooth. Pores irregular roundish, with +polygonal frames, two to four times as broad as the bars; eight to twelve +on the radius. Radial proportion of the three spheres = 1 : 3 : 10. Six +spines pyramidal, nearly as long as the diameter of the outer shell, with +six to nine prominent edges (along the corner number of the polygonal +meshes). + +_Dimensions._--Diameter of the outer shell 0.2, middle 0.06, inner 0.02; +cortical pores 0.008 to 0.016, bars 0.004; length of the spines 0.16 to +0.18, basal breadth 0.02. + +_Habitat._--South Pacific, Station 295, depth 1500 fathoms. + + +18. _Hexacontium antarcticum_, n. sp. + +Cortical shell thin walled, smooth, with irregular roundish pores, eight to +ten on the radius, two to four times as broad as the bars. Radial +proportion of the three spheres = 1 : 3 : 9. Both medullary shells with +smaller roundish irregular pores. Six spines conical, pyramidal at their +origin, about as long as the radius, as broad as one larger mesh. + +_Dimensions._--Diameter of the outer shell 0.18, middle 0.06, inner 0.02; +cortical pores 0.006 to 0.012, bars 0.003; length of the spines 0.1, basal +breadth 0.12. + +_Habitat._--Antarctic Ocean, Station 157, depth 1950 fathoms. + + + +Subgenus 4. _Hexacontura_, Haeckel. + +_Definition._--Pores of the cortical shell irregular, of different size or +form; surface covered with numerous conical papillae or bristle-shaped, +radial by-spines (other than the six main spines). + + +19. _Hexacontium papillosum_, n. sp. (Pl. 24, fig. 5). + +Cortical shell thick walled, papillose. Pores irregular roundish, often +somewhat lobed, five to six on the radius, two to four times as broad as +the bars. Radial proportion of the three spheres = 1 : 2.5 : 5. Both +medullary shells with subregular circular pores (inner much smaller). Six +radial spines short and stout, pommel or club shaped, with three prominent +wings, about as long as the shell radius, and as broad as the medullary +shell. + +_Dimensions._--Diameter of the outer shell 0.1, middle 0.05, inner 0.02, +cortical pores 0.006 to 0.012, bars 0.003; length of the spines 0.05, bars +0.02. + +_Habitat._--Central Pacific, Stations 266 to 272, at various depths. + + +{198}20. _Hexacontium gladiatum_, n. sp. (Pl. 25, fig. 8). + +Cortical shell very thick walled, spiny, with irregular network; its meshes +roundish, two to five times as broad as the bars, of very different size, +ten to fifteen on the half meridian. Bars between them very strong, +three-sided prismatic, armed with a great number of small thorns, and with +large spines at the nodal-points between every three meshes. Radial +proportion of the three spheres = 1 : 3 : 12. Six strong radial main spines +three-sided prismatic, with three prominent, somewhat contorted wings, +acute, broader than the diameter of the inner shell and as long as the +diameter of the outer shell. These six main spines are situated in the same +three dimensive axes as the six thin radial beams connecting the two +medullary shells. But the six radial beams which connect the middle with +the outer shell alternate with the former and lie in three other dimensive +axes,--a very rare and remarkable disposition. + +_Dimensions._--Diameter of the outer shell 0.2, middle 0.05, inner 0.016; +cortical pores 0.01 to 0.03, bars 0.006; length of the six spines 0.2, +breadth 0.02 to 0.03. + +_Habitat._--Tropical Atlantic, Station 342, depth 1445 fathoms. + + +21. _Hexacontium setosum_, n. sp. + +Cortical shell thin walled, with numerous bristle-shaped, simple, radial +by-spines of variable length. Pores irregular roundish, five to seven on +the radius, two to eight times as broad as the bars. Radial proportion of +the three spheres = 1 : 3 : 9. Main spines three-sided pyramidal, as long +as the radius. + +_Dimensions._--Diameter of the outer shell 0.1 to 0.015, middle 0.035 to +0.05, inner 0.013 to 0.016; cortical pores 0.01 to 0.03, bars 0.003 to +0.004; length of the six spines 0.05 to 0.08, basal breadth 0.012 to 0.015. + +_Habitat._--Cosmopolitan; Mediterranean, Atlantic, Pacific, surface; also +fossil in Barbados. + + +22. _Hexacontium furcatum_, n. sp. + +Cortical shell thin walled, covered with numerous thin, bristle-shaped +by-spines, which are forked and nearly as long as the main spines. Pores +irregular roundish, eight to ten on the radius, two to eight times as broad +as the bars. Radial proportion of the three spheres = 1 : 2.5 : 10. Main +spines triangular pyramidal, shorter then the radius. + +_Dimensions._--Diameter of the outer shell 0.18, middle 0.045, inner 0.018; +cortical pores 0.005 to 0.015, bars 0.002; length of the six spines 0.07, +basal breadth 0.015. + +_Habitat._--North Atlantic, Station 354, surface. + + +23. _Hexacontium drymodes_, Haeckel. + + _Actinomma drymodes_, Haeckel, 1862, Monogr. d. Radiol., p. 442, Taf. + xxiv. fig. 9. + +Cortical shell thin walled, covered with numerous thin, bristle-shaped +spines, which are double forked and half as long as the main spines. Pores +irregular roundish, eight to ten on the radius, {199}two to eight times as +broad as the bars. Radial proportion of the three spheres = 1 : 2 : 4. Main +spines three-sided prismatic, with prominent, often somewhat contorted +edges, at the distal end cuspidated; longer than the radius of the outer +shell. + +_Dimensions._--Diameter of the outer shell 0.15, middle 0.07, inner 0.035; +cortical pores 0.01 to 0.03, bars 0.04; length of the six spines 0.11, +basal breadth 0.03. + +_Habitat._--Mediterranean (Messina), surface; Canary Islands (Lanzerote); +Haeckel. + + +24. _Hexacontium periplectum_, n. sp. + +Cortical shell double, enclosing a simple medullary shell. Radial +proportion of the three shells = 1 : 4 : 5. Inner cortical shell thick +walled, with irregular roundish pores, two to eight times as broad as the +bars; five to seven on the radius. Numerous radial spines, arising from it, +are connected below their distal ends (at equal distances from the centre) +by delicate branched threads, and so form an outer, irregular, thin, +cortical shell, with spiny surface. Six main spines three-sided pyramidal, +about as long as the radius. + +_Dimensions._--Diameter of the outer shell 0.22, middle 0.2, inner 0.045; +cortical pores (of both outer shells) 0.01 to 0.03, bars 0.001 to 0.005; +length of the spines 0.1, basal breadth 0.02. + +_Habitat._--North Pacific, Station 241, surface. + + + +Genus 80. _Hexadendron_,[111] Haeckel, 1881, Prodromus, p. 452. + +_Definition._--#Cubosphaerida# with three concentric lattice-spheres and +six branched spines of equal size. + +The genus _Hexadendron_ differs from _Hexacontium_ in the ramification of +the six dimensive spines, and from the similar _Hexancistra_ in the +duplication of the medullary shell. As in the latter instance, each spine +can bear either three simple lateral branches or three rows of pinnate +lateral branches. + + +1. _Hexadendron quadricuspis_, n. sp. + +All three shells spherical, with radial proportion = 1 : 2 : 6. Pores of +both medullary shells regular circular, twice as broad as the bars. Pores +of the cortical shell irregular roundish, four to six times as broad as the +bars; surface a little thorny. Six radial spines prismatic, with three +prominent wing-like edges, which are prolonged below the distal end in +three curved lateral branches. (Differs from _Hexalonche quadricuspis_, Pl. +22, fig. 11, mainly in the double medullary shell.) + +_Dimensions._--Diameter of the outer shell 0.15, middle 0.05, inner 0.025; +length of the spines 0.12, breadth 0.01. + +_Habitat._--Central Pacific, Station 272, depth 2600 fathoms. + + +{200}2. _Hexadendron bipinnatum_, n. sp. (Pl. 23, fig. 1). + +All three shells regular octahedral, with very delicate network of +irregular polygonal meshes, and very thin, thread-like bars between them; +their radial proportion = 1 : 2.5 : 7.5. Surface of the cortical shell +covered with numerous bristle-shaped by-spines, as long as the radius. Six +main spines very large, three-sided prismatic, with three rows of pinnate, +lateral branches, on the three wing-like, spirally twisted edges (similar +to those of _Hexancistra mirabilis_, p. 189, Pl. 23, fig. 3). + +_Dimensions._--Diameter of the outer shell 0.12, middle 0.04, inner 0.016. + +_Habitat._--Central Pacific, Station 272, surface. + + + +Genus 81. _Hexacontarium_,[112] n. gen. + +_Definition._--#Cubosphaerida# with three concentric lattice-spheres and +six simple spines of different size; one opposite pair larger than the two +others. + +The genus _Hexacontarium_ exhibits to its ancestral form _Hexacontium_ the +same relation that _Hexaloncharium_ bears to _Hexalonche_; the former is +developed from the latter by duplication of the medullary shell. As two +opposite spines of one pair are larger than the four others, they +correspond to the three axes of a quadratic crystal. + + +1. _Hexacontarium dentatum_, n. sp. + +Cortical shell with regular circular, hexagonally framed pores, twice as +broad as the bars, with smooth surface. Radial proportion of the three +spheres = 1 : 2 : 5. Six radial spines three-sided prismatic, half as broad +as the inner medullary shell, with three dentated edges. Two opposite major +spines longer than the shell diameter; four other minor spines only half as +long as the radius. (Similar to _Hexacontium clavigerum_, Pl. 23, fig. 5, +but distinct by the prolongation of the spines of one axis.) + +_Dimensions._--Diameter of the outer shell 0.15, middle 0.06, inner 0.03; +length of the major spines 0.2, minor 0.04. + +_Habitat._--Central Pacific, Station 266, depth 2750 fathoms. + + +2. _Hexacontarium clavatum_, n. sp. + +Cortical shell covered with short conical by-spines and irregular roundish +pores, three to four times as broad as the bars. Radial proportion of the +three spheres = 1 : 3 : 8. Six radial spines three-sided prismatic, at the +distal end club-shaped; two major spines three times as long as the four +others, which are equal to the shell radius. + +_Dimensions._--Diameter of the outer shell 0.16, middle 0.06, inner 0.02. + +_Habitat._--Central Pacific, Station 272, depth 2600 fathoms. + + + +{201}Subfamily HEXACROMYIDA,[113] Haeckel, 1881, Prodromus, pp. 449, 453. + +_Definition._--#Cubosphaerida# with four concentric spherical +lattice-shells. + + + +Genus 82. _Hexacromyum_,[114] Haeckel, 1881, Prodromus, p. 453. + +_Definition._--#Cubosphaerida# with four concentric lattice-spheres and six +simple spines of equal size. + +The genus _Hexacromyum_ possesses four concentric, spherical, or octahedral +lattice-shells; two inner medullary shells within the central capsule, two +outer cortical outside it. The four spheres are connected by six radial +beams, which are prolonged outside into simple spines of equal size, +opposite in pairs in the three dimensive axes. This genus can be derived +from _Hexacontium_ by duplication of the cortical shell. + + +1. _Hexacromyum elegans_, n. sp. (Pl. 24, fig. 9). + +Shell composed of four concentric shells, with radial proportion = +1 : 2.5 : 7.5 : 10. First (innermost) shell with very small circular pores, +second shell with larger circular pores. Third shell (inner cortical shell) +with large, subregular, circular, hexagonally framed pores (eight to nine +on the radius), twice as broad as the bars; from the elevated nodal-points +of the hexagonal frames (between every three pores) arise thin +bristle-shaped radial beams, which are united at the distal end by vaulted +branches forming the delicate fourth shell. Surface smooth. Radial spines +three-sided pyramidal, as long as the radius, as broad at the base as the +innermost shell. + +_Dimensions._--Diameter of the four shells--(A) 0.02, (B) 0.05, (C) 0.15, +(D) 0.2; length of the six radial spines 0.1, basal breadth 0.02. + +_Habitat._--Central Pacific, Station 271, surface. + + +2. _Hexacromyum quadrigatum_, n. sp. + +Shell composed of four concentric shells, with radial proportion = +1 : 3 : 8 : 10. Structure of all four shells the same, with regular, +circular pores, twice to three times as broad as the bars; size of the +pores gradually increasing from the innermost to the outermost shell; +surface smooth. Radial spines three-sided pyramidal, as long as the radius, +half as broad at the base as the innermost shell. + +_Dimensions._--Diameter of the four shells--(A) 0.025, (B) 0.08, (C) 0.20, +(D) 0.25; length of the spines 0.12, basal breadth 0.012. + +_Habitat._--North Pacific, Station 253, depth 3125 fathoms. + + +{202}3. _Hexacromyum arachnoides_, n. sp. + + _Hexacromidium arachnoides_, Haeckel, 1881, Prodromus, p. 453. + +Shell composed of four concentric shells, with radial proportion = +1 : 2 : 3 : 4. Innermost shell with regular, hexagonal meshes; the three +other shells with irregular, polygonal meshes; bars between the large +meshes in all four shells very thin, cobweb-like. Surface covered with thin +bristle-shaped by-spines, as long as the radius. Six radial main spines +three-sided prismatic, longer than the diameter of the whole shell. + +_Dimensions._--Diameter of the four shells--(A) 0.08, (B) 0.16, (C) 0.24, +(D) 0.32; length of the spines 0.4, breadth 0.01. + +_Habitat._--South Pacific, Station 300, depth 1375 fathoms. + + +4. _Hexacromyum octahedrum_, n. sp. (Pl. 23, fig. 2). + +Shell composed of four concentric shells which are not spherical (as in the +three preceding species), but regular octahedral. Radial proportion = +1 : 2.5 : 6 : 9. Network in all four shells delicate, with irregular +polygonal meshes and thin bars; the thickness of the bars and size of the +meshes increasing from the innermost to the outermost shell. Six radial +spines three-sided prismatic, increasing slowly in breadth towards the +distal end, much longer than the shell diameter. + +_Dimensions._--Diameter of the four shells--(A) 0.02, (B) 0.05, (C) 0.12, +(D) 0.18; length of the radial spines 0.2 to 0.3 and more, breadth 0.01. + +_Habitat._--Central Pacific, Station 263, depth 2650 fathoms. + + + +Subfamily HEXACARYIDA,[115] Haeckel, 1881, Prodromus, p. 454. + +_Definition._--#Cubosphaerida# with five or more concentric lattice-shells. + + + +Genus 83. _Cubosphaera_,[116] n. gen. + +_Definition._--#Cubosphaerida# with five to six or more concentric +lattice-shells and six simple spines of equal size. + +The genus _Cubosphaera_ is developed from the preceding _Hexacromyum_ by +further addition of the concentric lattice-shells, their number amounting +to five, six, or more. The innermost two of these are medullary shells, the +others being cortical shells. All are connected by six radial beams, +prolonged outside into six simple spines of equal size; these lie opposite +in pairs in three dimensive axes, corresponding to the three axes of a +cube. + + +{203}1. _Cubosphaera cubaxonia_, n. sp. (Pl. 24, fig. 8). + + _Hexacromyon cubaxonium_, Haeckel, 1881, Prodrom. et Atlas. + +Shell composed of five concentric spheres, with the radial proportion = +1 : 3 : 8 : 10 : 13. The two medullary shells with small regular, circular +pores of the same breadth as the bars. Inner cortical shell (third shell) +with large regular, circular pores, four times as broad as the bars, +hexagonally framed. From each hexagon-corner arises a thin bristle-shaped +radial by-spine, which at a fixed distance from the centre is united with +the middle cortical shell (fourth shell), which has very small circular +pores. The beginning of the fifth shell (outermost) is indicated by six +small reticula, produced by the six main spines at equal distances from the +centre. All five shells are united by six prismatic radial beams, ending +outside in pyramidal furrowed spines. + +_Dimensions._--Diameter of the five shells--(A) 0.2, (B) 0.15, (C) 0.12, +(D) 0.045, (E) 0.015. + +_Habitat._--Central Pacific, Station 272, depth 2600 fathoms. + + +2. _Cubosphaera concentrica_, n. sp. + +Shell composed of six concentric spheres, with the radial proportion = +1 : 2 : 6 : 7.5 : 9 : 11. The two medullary shells with regular, circular +pores, twice as broad as the bars. The four cortical shells of the same +structure, with irregular, roundish pores, three to four times as broad as +the bars. The size of these pores and the breadth of their bars gradually +increase towards the smooth surface. All six shells are connected by six +thin three-sided prismatic radial beams, which are prolonged outside in six +stronger spines, angular pyramidal, with smooth edges, as long as the shell +radius. + +_Dimensions._--Diameter of the six shells--(A) 0.02 (B) 0.04, (C) 0.12, (D) +0.15, (E) 0.18, (F) 0.22. + +_Habitat._--Central Pacific, Station 268, depth 2900 fathoms. + + + +Genus 84. _Hexacaryum_,[117] Haeckel, 1881, Prodromus, p. 454. + +_Definition._--#Cubosphaerida# with five to six or more concentric +lattice-shells and six branched spines of equal size. + +The genus _Hexacaryum_ is distinguished from the foregoing _Cubosphaera_ by +ramification of the six radial spines, and therefore exhibits the same +relation to it that _Hexancistra_ bears to _Hexastylus_, &c. + + +1. _Hexacaryum arborescens_, n. sp. (Pl. 23, figs. 4, 4_a_). + +Shell composed of five, six, or more concentric shells, which are united by +six very large radial spines. The two medullary shells spherical, inner +with regular, circular, outer with irregular polygonal pores. All cortical +shells (third and following) not spherical, but regular octahedral, with +irregular polygonal meshes and thin bars. Radial spines prismatic, with +three wing-like, spirally twisted edges, which at equal distances send out +thin forked lateral branches (six on each {204}verticil); by further +ramification and communication of these branches the triangular net-plates +arise, filling out the sides of the octahedral cortical shells. Diameter of +all shells little different. The outer free parts of the six spines are +arborescent, twice to three times as long as the enclosed inner parts, and +bear six to eight verticils of free lateral branches, decreasing in size +towards the distal end (similar to _Arachnosphaera_). + +_Dimensions._--Diameter of the six shells--(A) 0.015, (B) 0.04, (C) 0.1, +(D) 0.16, (E) 0.22, (F) &c.; average distance of the concentric octahedra = +0.06; length of the radial spines 0.3 to 0.4 and more, breadth 0.02. + +_Habitat._--Central Pacific, Station 274, surface. + + + +Subfamily HEXADORIDA,[118] Haeckel, 1881, Prodromus, pp. 449, 455. + +_Definition._--#Cubosphaerida# with spongy spherical or octahedral shell +(with or without enclosed concentrical lattice-shells). + + + +Genus 85. _Cubaxonium_,[119] n. gen. + +_Definition._--#Cubosphaerida# with solid spongy spherical or octahedral +shell, without latticed medullary shell in the centre, and with six simple +radial spines of equal size. + +The genus _Cubosphaera_ may be regarded as a form of _Styptosphaera_, which +develops six radial spines, opposite in pairs in the three dimensive axes. +The solid spongy framework of the shell assumes the outer form either of a +sphere, or of a regular octahedron. + + +1. _Cubaxonium spongiosum_, n. sp. + +Spongy shell spherical, composed of a very dense spongy framework of nearly +uniform structure; the meshes three to four times as broad as the bars; +surface almost smooth. Six spines cylindrical, twice to three times as long +as the diameter of the spongy sphere, about as broad as one half mesh. + +_Dimensions._--Diameter of the sphere 0.2, meshes 0.006 to 0.008, bars +0.002; length of the spines 0.4 to 0.5, breadth 0.004. + +_Habitat._--South Pacific, Station 288, surface. + + +2. _Cubaxonium octahedrum_, n. sp. + +Spongy shell octahedral, composed of a loose spongy framework of nearly +uniform structure; the meshes ten to twelve times as broad as the bars; +surface thorny. Six spines three-sided {205}pyramidal, longer than the +diameter of the octahedron, arising from its six corners, as broad at the +base as one mesh. + +_Dimensions._--Diameter of the shell 0.15, meshes 0.01 to 0.012, bars +0.001; length of the spines 0.2, basal breadth 0.01. + +_Habitat._--South Pacific, Station 300, surface. + + + +Genus 86. _Hexadoras_,[120] Haeckel, 1881, Prodromus, p. 455. + +_Definition._--#Cubosphaerida# with spongy spherical shell and one simple +latticed medullary shell in its centre, having six simple spines of equal +size. + +The genus _Hexadoras_ exhibits the same structure of the spongy shell as +_Spongoplegma_, but differs from it in the production of six dimensive +spines. In the centre lies one simple, latticed, medullary shell, which is +either spherical or octahedral. In the latter case the six spines arise +from the six corners of the octahedron. + + +1. _Hexadoras axophaena_, n. sp. + +Medullary shell spherical, with regular hexagonal meshes, twice as broad as +the bars. Cortical shell entirely enclosing it, with loose irregular +framework and thorny surface. Diameter of the outer shell three times as +large as that of the inner. Six radial spines arising from the medullary +shell, four to five times as long as the radius of the cortical shell, +three-sided prismatic, with straight dentated edges. + +_Dimensions._--Diameter of the outer shell 0.15, inner 0.05; length of the +spines 0.3 to 0.4. + +_Habitat._--Central Pacific, Station 265, depth 2900 fathoms. + + +2. _Hexadoras lychnosphaera_, n. sp. + +Medullary shell spherical, with regular, circular, hexagonally framed +pores, three times as broad as the bars. Cortical shell enveloping it, with +loose irregular framework and spiny surface. Diameter of the outer shell +eight times as large as that of the inner. Six radial spines arising from +the inner shell, three-sided prismatic, with dentated, spirally contorted +edges, seven times as long as the diameter of the medullary shell, with +three lateral branches at the distal end (similar to _Lychnosphaera_, Pl. +11, fig. 1). + +_Dimensions._--Diameter of the outer shell 0.5, inner 0.06; total length of +the spines 0.4, breadth 0.01. + +_Habitat._--Central Pacific, Station 270, depth 2925 fathoms. + + +3. _Hexadoras octahedrum_, n. sp. + +Medullary shell regular octahedral, with irregular polygonal meshes, five +times as broad as the bars. Cortical shell enveloping it, with dense spongy +framework, also octahedral with rough surface. {206}Diameter of the outer +shell five times as large as that of the inner. Six radial spines very +long, arising from the six corners of the inner and piercing the spongy +mass of the outer shell, considerably exceeding it at the free distal end, +three-sided prismatic, with elegantly denticulate edges. + +_Dimensions._--Diameter of the outer shell 0.2, inner 0.04; total length of +the spines 0.3 or more, breadth 0.02. + +_Habitat._--Central Pacific, Station 266, depth 2750 fathoms. + + + +Genus 87. _Hexadoridium_,[121] Haeckel, 1881, Prodromus, p. 455. + +_Definition_.--#Cubosphaerida# with spongy spherical shell and two +concentric latticed medullary shells in its centre, having six simple +spines of equal size. + + +The genus _Hexadoridium_ differs from _Hexadoras_ in the duplication of the +medullary shell, and exhibits therefore the same relation to it that +_Spongodictyon_ bears to _Spongoplegma_. In the only known species the six +spines are opposite, arranged quite regularly in pairs in the three +dimensive axes, and consequently represent the three axes of a regular +crystal or cube. + + +1. _Hexadoridium streptacanthum_, n. sp. (Pl. 25, figs. 1, 1_a_). + +Both medullary shells spherical, with small regular, circular pores, twice +as broad as the bars; outer twice as broad as the inner. Spongy cortical +shell enclosing it with dense framework, five times as broad as the outer +medullary shell, regular octahedral. Six radial spines, arising from the +latter, are thinned at the inner end, three to five times as long as the +diameter of the cortical shell, and nearly as broad as the inner medullary +shell, with three dentated and spirally contorted edges. (Very similar to +the common _Spongosphaera streptacantha_, with irregular and variable +number and dispositions of spines; possibly its ancestral form?). + +_Dimensions._--Diameter of the cortical shell 0.2, of the outer medullary +shell 0.04, inner 0.02; length of the spines 1 mm. and more, breadth 0.02. + +_Habitat._--Central Pacific, Station 271, depth 2425 fathoms. + + + +Family X. #ASTROSPHAERIDA# (Pls. 11, 18-20, 26-30). + +_Astrosphaerida_, Haeckel, 1881, Prodromus, p. 449. + +_Definition._--#Sphaeroidea# with numerous (eight to twelve or more, +commonly between twenty and sixty) radial spines on the surface of the +spherical shell; living solitary (not associated in colonies). + +The family #Astrosphaerida#, the largest and most varied of all +#Sphaeroidea#, is distinguished from the other members of this group by the +possession of numerous {207}radial spines, which are either regularly or +irregularly disposed on the surface of the spherical shell. The extreme +variability and richness of form in this family is mainly due to the +different size, shape, and disposition of these radial spines. + +The simplest Astrosphaerida are the Coscinommida, with a single spherical +or polyhedral lattice-shell. To this ancestral group all other subfamilies +can be opposed as "Astrosphaerida composita," since their skeleton is +composed of two or more concentric lattice-shells: two in the Haliommida, +three in the Actinommida, four in the Cromyommida, five or more in the +Caryommida. In these four subfamilies the concentric shells are all simple +(not spongy) fenestrated spheres or endospherical polyhedra. In the sixth +subfamily, the Spongiommida, the shell is wholly or partially composed of +spongy irregular wicker-work, with or without a medullary shell in the +centre. + +_The Number of the Radial Spines_ in the Astrosphaerida is extremely +variable, and ranges from eight to forty or more; in many cases more than +one hundred. Often each nodal-point of the network develops on the shell +surface one spine. Still more frequently the number of the spines is less +than that of the nodal-points. In all concentric Astrosphaerida, having two +or more concentrical shells, we can distinguish "primary spines," as outer +prolongations of the inner radial beams connecting the shells, and +"secondary spines," developed only on the outer surface of the shell. +Naturally the former are of much greater importance than the latter. But we +can also often distinguish among the latter larger "main spines" and +smaller "by-spines," the latter commonly much more numerous than the +former. + +_The Disposition of the Radial Spines_, either regular or irregular, is a +subject of great morphological interest, and remains to be exhausted by +further observations. The following cases of regular disposition have been +observed by me--(A) eight spines, opposite in pairs in four axes +corresponding to the four diagonal axes of a cube; (B) nine spines, +regularly disposed at equal distances (?) (not opposed in pairs); (C) ten +spines, disposed at equal distances (?); (D) twelve spines, regularly +disposed, corresponding to the twelve corners of the regular icosahedron; +(E) fourteen spines, quite regularly disposed (six corresponding to the +three axes of a regular octahedron, eight to the central points of its +eight faces); (F) sixteen spines, regularly disposed (?); (G) twenty spines +(very common!), either disposed in the same manner (after the law of +Johannes Mueller) as in the ACANTHARIA (?), or corresponding to the twenty +corners of the regular or pentagonal dodecahedron, or disposed in the same +manner as in many #Larcoidea# (Tholonida, &c., to be described afterwards); +(H) twenty-four spines, regularly disposed (?); (I) thirty-two spines, +quite regularly disposed (twenty corresponding to the twenty corners of the +regular dodecahedron, twelve to the central points of its twelve faces); +(K) forty spines, nearly regularly (or quite symmetrically?) disposed. If +the number of the spines amounts to more than forty, it is as a rule +impossible to determine their regular disposition in a satisfactory manner. + +{208}_Synopsis of the Genera of Astrosphaerida._ + + ------------------------------------------------------------------------- + I. Subfamily Coscinommida. + (One single latticed shell.) + ------------------------------------------------------------------------- + { All spines of the same + Spines all simple, not { kind, 88. _Acanthosphaera_. + branched and not { + tubulous. { Larger main spines and + { smaller by-spines, 89. _Heliosphaera_. + + Spines hollow conical tubes with porous walls, 90. _Conosphaera_. + + Between simple spines the pores prolonged in hollow + tubes, 91. _Coscinomma_. + + { Spines with lateral + { branches, 92. _Cladococcus_. + Spines branched or forked.{ + { Spines forked or + { dichotomous, 93. _Elaphococcus_. + ------------------------------------------------------------------------- + II. Subfamily Haliommida. + (Two concentric latticed shells.) + ------------------------------------------------------------------------- + { All spines equal, + { simple, 94. _Haliomma_. + { + A. Elatommida, one { All spines simple, of + medullary and one cortical{ two different kinds, 95. _Heliosoma_. + shell. { + { Spines branched, 96. _Elatomma_. + + { No by-spines, 97. _Leptosphaera_. + { + B. Diplosphaerida, both { Inner by-spines, 98. _Diplosphaera_. + shells cortical. { + { Outer by-spines, 99. _Drymosphaera_. + { + { Outer and inner + { by-spines, 100. _Astrosphaera_. + ------------------------------------------------------------------------- + III. Subfamily Actinommida. + (Three concentric latticed shells.) + ------------------------------------------------------------------------- + { All spines equal, 101. _Actinomma_. + Radial spines not { + branched. { Larger main spines and + { smaller by-spines, 102. _Echinomma_. + + Radial spines branched or forked, 103. _Pityomma_. + ------------------------------------------------------------------------- + IV. Subfamily Cromyommida. + (Three concentric latticed shells.) + ------------------------------------------------------------------------- + { All spines equal, 104. _Cromyomma_. + Radial spines not { + branched. { Larger main spines and + { smaller by-spines, 105. _Cromyechinus_. + + Radial spines branched or forked, 106. _Cromyodrymus_. + ------------------------------------------------------------------------- + V. Subfamily Caryommida. + (Numerous, five to ten or more, concentric latticed shells.) + ------------------------------------------------------------------------- + Two medullary shells and three or more cortical + shells (lattice work ordinary), 107. _Caryomma_. + + { Triangular meshes, + No medullary shells { simple bars, without + (lattice work { diagonal bars, 108. _Arachnopila_. + arachnoidal); three-sided { + prismatic spines, { Triangular meshes, + with verticils of three { simple bars; diagonal + forked branches. { bars between the 109. _Arachnopegma_. + (Arachnosphaerida.) { shells, + { + { Polygonal meshes, bars + { branched, 110. _Arachnosphaera_. + + ------------------------------------------------------------------------- + VI. Subfamily Spongiommida. + (Spherical shell whole or partly spongy, with or without enclosed + latticed medullary shells in the centre.) + ------------------------------------------------------------------------- + I. Tribe {Spongy {Spines simple, 111. _Spongiomma_. + Spongodrymida, { sphere { + without { solid. {Spines branched, 112. _Spongodrymus_. + latticed { + medullary {Spongy {Spines simple, 113. _Spongechinus_. + shell. { sphere { + { hollow. {Spines branched, 114. _Spongothammus_. + + {Framework arising + { from the medullary + { shell, 115. _Spongopila_. + { + {Medullary {Framework {No medullary by-spines, + II. Tribe { shell { separate { 116. _Rhizoplegma_. + Rhizoplegmida, { spherical. { from the { + with { { medullary {Medullary by-spines, + one single { { shell. { 117. _Lychnosphaera_. + latticed { + medullary {Medullary {Framework arising + shell. { shell a { immediately from + { simple { the medullary + { cube. { shell, 118. _Centrocubus_. + { { + { {Framework separate + { { from the medullary + { { shell, 119. _Octodendron_. + + {Framework arising + III. Tribe Rhizosphaerida, { from the medullary + with two concentric { shell, 120. _Spongosphaera_. + latticed medullary shells. { + {Framework separate + { from the medullary + { shell, 121. _Rhizosphaera_. + + + +Subfamily COSCINOMMIDA, Haeckel. + +_Heliosphaerida_, Haeckel, 1881, Prodromus, pp. 449, 450. + +_Definition._--#Astrosphaerida# with one single spherical lattice-shell. + + + +Genus 88. _Acanthosphaera_,[122] Ehrenberg, 1858, Monatsber. d. k. preuss. +Akad. d. Wiss. Berlin, p. 12. + +_Definition._--#Astrosphaerida# with one simple lattice-sphere, covered +with simple radial spines of the same kind. + +The genus _Acanthosphaera_ exhibits the most simple form of all +_Astrosphaerida_; a simple spherical lattice-shell, the surface of which is +covered by radial spines of one and the same kind. The number of the latter +is very variable, often twelve to twenty, regularly disposed; in other +cases forty to sixty or more; and sometimes at each nodal-point of the +network a spine is developed. + + + +{210}Subgenus 1. _Rhaphidococcus_, Haeckel, 1862, Monogr. d. Radiol., p. +365 (_sensu emendato_). + +_Definition._--Pores of the spherical shell regular or subregular, all of +nearly equal size and similar form. Radial spines arising from all the +nodal-points of the network. + + +1. _Acanthosphaera tenuissima_, Haeckel. + + _Heliosphaera tenuissima_, Haeckel, 1862, Monogr. d. Radiol., p. 351, + Taf. ix. fig. 2. + +Shell extremely thin walled, eight to ten times as broad as one pore. +Meshes or pores regular, hexagonal, with thread-like bars; five to seven on +the radius. At each nodal-point (between every three meshes) arises a +bristle-shaped radial spine, as long as the diameter of one pore. + +_Dimensions._--Diameter of the shell 0.2 to 0.25, of the meshes or pores +0.025 to 0.03, bars below 0.0001; length of the spines 0.03. + +_Habitat._--Mediterranean (Messina), North Atlantic (Canary Islands). + + +2. _Acanthosphaera tenuis_, n. sp. + +Shell very thin walled, about twenty times as broad as one pore. Meshes +subregular, hexagonal, with thread-like bars; twelve to fourteen on the +radius. At each nodal-point arises a bristle-shaped radial spine, about as +long as the radius. + +_Dimensions._--Diameter of the shell 0.3 to 0.35, pores 0.015 to 0.018, +bars below 0.001; length of the spines 0.12 to 0.16. + +_Habitat._--Central Pacific, Stations 266 to 274, depth 2350 to 2925 +fathoms. + + +3. _Acanthosphaera macropora_, n. sp. + +Shell thin walled, five to six times as broad as one mesh. Pores regular, +circular, hexagonally framed, ten to twelve times as broad as the bars. +Radial spines bristle-shaped, as long as the diameter of one pore, arising +from all the nodal-points. + +_Dimensions._--Diameter of the shell 0.07 to 0.08, pores 0.012, bars 0.001; +length of the spines 0.012. + +_Habitat._--Central Pacific, Station 271, surface. + + +4. _Acanthosphaera micropora_, n. sp. + +Shell thick walled, forty to fifty times as broad as one pore. Pores +regular, circular, hexagonally framed, half as broad as the bars. Radial +spines bristle-shaped, as long as the radius of the shell, arising from all +the nodal-points. + +_Dimensions._--Diameter of the shell 0.22, pores 0.003, bars 0.006; length +of the spines 0.1. + +_Habitat._--South Pacific, Station 288, surface. + + +{211}5. _Acanthosphaera dentata_, Haeckel. + + _Cladococcus dentatus_, Haeckel, 1862, Monogr. d. Radiol., p. 367, Taf. + xiii. fig. 10. + +Shell thin walled, eight to ten times as broad as one pore. Pores regular, +circular, hexagonally framed, three times as broad as the bars. Radial +spines arising from all the nodal-points of the network, three-sided +prismatic, with dentated or serrated edges, longer than the shell diameter. + +_Dimensions._--Diameter of the shell 0.08, pores 0.01, bars 0.003; length +of the spines 0.1, breadth 0.003. + +_Habitat._--Mediterranean (Messina), surface. + + +6. _Acanthosphaera acufera_, Haeckel. + + _Rhaphidococcus acufer_, Haeckel, 1862, Monogr. d. Radiol., p. 366, Taf. + xiv. fig. 1. + + _Cladococcus acufer_, Haeckel, 1860, Monatsber. d. k. preuss. Akad. d. + Wiss. Berlin, p. 800. + +Shell thin walled, eight to ten times as broad as one mesh. Pores regular, +circular, three times as broad as the bars. Radial spines bristle-shaped, +arising with thicker conical bases from all the nodal-points, about as long +as the diameter of the shell. + +_Dimensions._--Diameter of the shell 0.08, pores 0.01, bars 0.003; length +of the spines 0.08. + +_Habitat._--Mediterranean (Messina); North Atlantic, Station 354, surface. + + +7. _Acanthosphaera castanea_, n. sp. (Pl. 26, fig. 3). + +Shell thick walled, thirty times as broad as one mesh. Pores regular, +circular, nearly of the same breadth as the bars. Radial spines +bristle-shaped, arising with thicker conical bases from all the +nodal-points, scarcely half as long as the radius of the shell. + +_Dimensions._--Diameter of the shell 0.15, pores and bars 0.005; length of +the spines 0.03. + +_Habitat._--North Pacific, Station 244, surface. + + +8. _Acanthosphaera flosculenta_, n. sp. + +Shell thick walled, thirteen times as broad as one mesh. Pores regular, +circular, three times as broad as the bars, with an elegant six-lobed frame +(Pl. 28, fig. 1_b_). In the intervals between the six lobes of each mesh +arise six conical radial spines (half as long as the radius), six around +each pore. (Differs from the similar _Haliomma flosculentum_, Pl. 28, fig. +1, in the absence of an enclosed medullary shell and the stronger +development of the spines.) + +_Dimensions._--Diameter of the shell 0.13, pores 0.01, bars 0.003; length +of the spines 0.03. + +_Habitat._--Indian Ocean, Cocos Islands, surface, Rabbe. + + + +Subgenus 2. _Rhaphidocapsa_, Haeckel. + +_Definition._--Pores of the spherical shell regular or subregular, all of +nearly equal size and similar form. Radial spines scattered at some +distance apart, not at all the nodal-points. + + +{212}9. _Acanthosphaera insignis_, Haeckel. + + _Heliosphaera insignis_, R. Hertwig, 1879, Organismus der Radiol., p. 40, + Taf. v. fig. 7. + +Shell thin walled, about ten times as broad as one mesh. Pores regular, +hexagonal, ten to twelve times as broad as the bars. Radial spines about +one hundred and twenty, arising from certain nodal-points of the network, +being as long as the diameter of the sphere, three-sided prismatic, with +three thin denticulated edges. + +_Dimensions._--Diameter of the shell 0.2, pores 0.02, bars 0.002; length of +the spines 0.18, breadth 0.003. + +_Habitat._--Cosmopolitan; Mediterranean (Messina), Atlantic (Stations 325, +347), Indian (Ceylon), Pacific (Stations 270 to 274), surface. + + +10. _Acanthosphaera fortispina_, n. sp. + +Shell thin walled, about six times as broad as one mesh. Pores subregular, +hexagonal, with thread-like bars; three to four on the radius. Radial +spines about twenty, three-sided pyramidal, as long as the diameter, and +one-third as broad at the base as one pore. + +_Dimensions._--Diameter of the shell 0.06 to 0.09, pores 0.01 to 0.014, +bars below 0.001; length of the spines 0.07 to 0.08, basal breadth 0.03 to +0.04. + +_Habitat._--North Pacific, Station 244, depth 2900 fathoms. + + +11. _Acanthosphaera mucronata_, n. sp. (Pl. 26, fig. 7). + +Shell thick walled, fifteen times as broad as one pore. Pores regular, +circular, hexagonally framed, funnel-shaped, three times as broad as the +bars. Radial spines twenty to thirty, dagger-shaped or spindle-shaped, +angular, twice as broad in the middle as one pore, about as long as the +radius. + +_Dimensions._--Diameter of the shell 0.11, pores 0.0075, bars 0.0025; +length of the spines 0.06, breadth 0.015. + +_Habitat._--Central Pacific, Station 271, depth 2425 fathoms. + + +12. _Acanthosphaera clavata_, n. sp. (Pl. 26, fig. 8). + +Shell thick walled, ten to twelve times as broad as one mesh. Pores +subregular, circular, three times as broad as the bars. Radial spines +twenty, club-shaped, angular, with prominent edges, twice as broad at the +distal end as one pore, about as long as the radius. + +_Dimensions._--Diameter of the shell 0.11, pores 0.01, bars 0.003; length +of the spines 0.06, breadth 0.02. + +_Habitat._--Western Tropical Pacific, Station 225, depth 4475 fathoms. + + +13. _Acanthosphaera marginata_, n. sp. + +Shell thick walled, twelve times as broad as one mesh. Pores regular, +circular double-edged, four times as broad as the bars. Radial spines +conical, fourteen in number, about as long as the {213}radius, and as broad +at the base as one mesh. Six spines correspond to the six corners of a +regular octahedron, eight to the centre of the eight faces. + +_Dimensions._--Diameter of the shell 0.1, pores 0.008, bars 0.002; radial +spines 0.06, basal breadth 0.01. + +_Habitat._--Central Pacific, Station 274, surface. + + +14. _Acanthosphaera florida_, n. sp. + +Shell thick walled, fifteen times as broad as one mesh. Pores regular, +circular, hexagonally lobed, separated by prominent funnel-shaped crests of +half the breadth. Twenty conical radial spines, half as long as the radius, +as broad at the base as one funnel. + +_Dimensions._--Diameter of the shell 0.15, pores 0.01, bars 0.005; length +of the spines 0.04, basal breadth 0.02. + +_Habitat._--South Atlantic, Station 325, depth 2650 fathoms. + + +15. _Acanthosphaera enneacantha_, n. sp. + +Shell thin walled, fourteen times as broad as one mesh. Pores regular, +circular, twice as broad as the bars. Nine radial spines, regularly +disposed, as long as the shell diameter, three-sided prismatic, with +pyramidal apex, as broad as one mesh. + +_Dimensions._--Diameter of the shell 0.14, pores 0.01, bars 0.005; length +of the spines 0.15, breadth 0.01. + +_Habitat._--Central Pacific, Station 265, depth 2900 fathoms. + + +16. _Acanthosphaera octahedralis_, n. sp. + +Shell thick walled, octahedral, fourteen times as broad as one mesh. Pores +regular, circular, three times as broad as the bars. Fourteen radial +spines, regularly disposed, conical, as long as the radius of the shell, +twice as broad at the base as one mesh. Six spines correspond to the six +corners of a regular octahedron, eight to the central points of its eight +faces. + +_Dimensions._--Diameter of the shell 0.14, pores 0.01, bars 0.003; length +of the spines 0.08, basal breadth 0.02. + +_Habitat._--North Pacific, Station 253, depth 3125 fathoms. + + +17. _Acanthosphaera compacta_, n. sp. + +Shell thick walled, about sixty times as broad as one mesh. Pores regular, +circular, twice as broad as the bars. Thirty to forty radial spines, +three-sided pyramidal, scarcely half as long as the radius, five to six +times as broad at the base as one pore. + +_Dimensions._--Diameter of the shell 0.24, pores 0.004, bars 0.002; length +of the radial spines 0.05, basal breadth 0.02. + +_Habitat._--Fossil in Barbados. + + + +{214}Subgenus 3. _Raphidodrymus_, Haeckel. + +_Definition._--Pores of the spherical shell irregular, of different size or +form. Radial spines arising from all the nodal-points of the network. + + +18. _Acanthosphaera capillaris_, n. sp. + +Shell thin walled, with irregular polygonal meshes, twelve to twenty times +as broad as the bars; eight to ten on the radius. Radial spines +bristle-shaped, arising from all the nodal-points of the network, about as +long as the diameter of the largest meshes. + +_Dimensions._--Diameter of the shell 0.15 to 0.2, pores 0.012 to 0.02, bars +0.001; length of the spines 0.02. + +_Habitat._--Central Pacific, Stations 260 to 274, surface. + + +19. _Acanthosphaera arctica_, n. sp. + +Shell thin walled, with irregular roundish, polygonally framed meshes, +three to four times as broad as the bars. Radial spines arising from all +the nodal-points of the network, pyramidal at the base; in the distal half +bristle-shaped, as long as the radius. + +_Dimensions._--Diameter of the shell 0.12, pores 0.006 to 0.008, bars +0.002; length of the spines 0.07. + +_Habitat._--Arctic Ocean, Greenland (in the stomach of _Periphylla +hyacinthina_). + + +20. _Acanthosphaera antarctica_, n. sp. + +Shell thick walled, with irregular, roundish pores, about as broad as the +bars. Radial spines arising from all nodal-points of the network, conical +at the base, half as long as the radius. + +_Dimensions._--Diameter of the shell 0.15, pores and bars 0.005 to 0.008; +length of the spines 0.04. + +_Habitat._--Antarctic Ocean, Station 157, depth 1950 fathoms. + + + +Subgenus 4. _Rhaphidosphaera_, Haeckel, 1881, Prodromus, p. 450. + +_Definition._--Pores of the spherical shell irregular, of different size or +form. Radial spines scattered at intervals, not at all the nodal-points. + + +21. _Acanthosphaera echinoides_, Haeckel. + + _Cyrtidosphaera echinoides_, Haeckel, 1865, Zeitschr. f. wiss. Zool., xv. + p. 367, Taf. xxvi. fig. 5. + +Shell thin walled, with irregular polygonal or more roundish pores of very +different size. Forty to fifty very large meshes, separated by rows of much +smaller meshes. Radial spines forty to sixty, half as long as the shell +radius, bristle-shaped, with conical bases. + +{215}_Dimensions._--Diameter of the shell 0.13, larger pores 0.03, smaller +0.003; length of the spines 0.03. + +_Habitat._--Mediterranean (Nice), surface. + + +22. _Acanthosphaera longispina_, n. sp. + +Shell thin walled, with irregular polygonal meshes, four to six times as +broad as the bars; six to eight on the radius. Thirty to forty radial +spines, three-sided prismatic, twice as broad as the bars, twice to three +times as long as the diameter of the shell. + +_Dimensions._--Diameter of the shell 0.12 to 0.15, pores 0.012 to 0.02, +bars 0.003; length of the radial spines 0.2 to 0.4, breadth 0.006. + +_Habitat._--North Pacific, Station 253, surface. + + +23. _Acanthosphaera brevispina_, n. sp. + +Shell thick walled, with irregular polygonal meshes, twice to four times as +broad as the bars; twelve to sixteen on the radius. Sixty to eighty radial +spines, pyramidal, half as long as the radius of the shell, one-fourth as +broad at the base. + +_Dimensions._--Diameter of the shell 0.2 to 0.22, pores 0.006 to 0.012, +bars 0.003; length of the spines 0.05, basal breadth 0.02. + +_Habitat._--Central Pacific, Station 268, depth 2900 fathoms. + + +24. _Acanthosphaera acanthica_, Haeckel. + + _Cenosphaera acanthica_, Stoehr, 1880, Palaeontogr., vol. xxvi. p. 86, + Taf. i. fig. 3. + +Shell thick walled, with irregular, roundish pores, twice to three times as +broad as the bars; seven to nine on the radius. Ten to twenty radial spines +pyramidal, shorter than the radius, twice as broad at the base as one mesh. + +_Dimensions._--Diameter of the shell 0.12 to 0.16, pores 0.006 to 0.009, +bars 0.003; length of the spines 0.04 to 0.06, basal breadth 0.01 to 0.015. + +_Habitat._--Fossil in Tertiary rocks of Sicily and Barbados. + + +25. _Acanthosphaera haliphormis_, Ehrenberg. + + _Acanthosphaera haliphormis_, Ehrenberg, 1861, Abhandl. d. k. Akad. d. + Wiss. Berlin, 1872, Taf. ii. fig. 1. + +Shell thick walled, with irregular, roundish pores, twice to four times as +broad as the bars; four to five on the radius. Twelve to twenty radial +spines pyramidal, longer than the radius, scarcely as broad as one mesh at +the base. + +_Dimensions._--Diameter of the shell 0.11, pores 0.01 to 0.02, bars 0.005; +length of the spines 0.06 to 0.08, basal breadth 0.01. + +_Habitat._--Arctic Ocean, near Greenland, depth 1000 fathoms. + + +{216}26. _Acanthosphaera angulata_, n. sp. (Pl. 26, fig. 4). + +Shell thin walled; its pores irregular, roundish, with angular, +double-edged margin, two to four times as broad as the bars; six to eight +on the radius. Twenty to thirty radial spines pyramidal, angular, with +prominent edges, shorter than the radius, as broad at the base as one small +mesh. + +_Dimensions._--Diameter of the shell 0.2, pores 0.02 to 0.04, bars 0.01; +length of the spines 0.06, basal breadth 0.02. + +_Habitat._--South Atlantic, Station 332, depth 2200 fathoms. + + +27. _Acanthosphaera conifera_, n. sp. + +Shell thick walled, with irregular, roundish pores, twice to five times as +broad as the bars; ten to twelve on the radius. Twenty radial spines +conical, regularly disposed, half as long as the radius, as broad at the +base as one of the largest meshes. + +_Dimensions._--Diameter of the shell 0.2, pores 0.008 to 0.02, bars 0.004; +length of the spines 0.05, basal breadth 0.02. + +_Habitat._--Central Pacific, Station 268, depth 2900 fathoms. + + +28. _Acanthosphaera maxima_, n. sp. + +Shell thick walled, with irregular, roundish pores, twice to eight times as +broad as the bars; twelve to twenty on the radius. Radial spines very +numerous (two to three hundred), short, conical, scarcely as long as the +diameter of the largest meshes, and one-third as broad. + +_Dimensions._--Diameter of the shell 0.3 to 0.4, pores 0.008 to 0.03, bars +0.004; length of the radial spines 0.03, basal breadth 0.01. + +_Habitat._--Tropical Atlantic, Station 348, depth 2450 fathoms. + + +29. _Acanthosphaera simplex_, Haeckel. + + _Rhaphidococcus simplex_, Haeckel, Monogr. d. Radiol., 1862, p. 366, + figs. 5, 6.Taf. xiii. + + _Cladococcus simplex_, Haeckel, 1860, Monatsber. d. k. preuss. Akad. d. + Wiss. Berlin, p. 800. + +Shell thick walled, with irregular, roundish pores, three to six times as +broad as the bars; eight to nine on the radius. Forty to sixty radial +spines, about as long as the diameter of the shell, three-sided prismatic, +not straight, but more or less bent. + +_Dimensions._--Diameter of the shell 0.12, pores 0.005 to 0.012, bars +0.0015 to 0.02; length of the spines 0.12, breadth 0.003. + +_Habitat._--Mediterranean (Messina), surface, Haeckel. + + +30. _Acanthosphaera gibbosa_, n. sp. + +Shell thin walled, rugged or tuberculate, covered by about twenty +hill-shaped tubercles or protuberances with flat valleys between them. +Network very delicate, with thread-like bars and {217}irregular, polygonal +pores; twenty to thirty on the radius. Radial spines very numerous, +bristle-shaped, twice to three times as long as the diameter of the pores. + +_Dimensions._--Diameter of the shell 0.3, pores 0.01 to 0.02; length of the +spines 0.02 to 0.05. + +_Habitat._--Central Pacific, Station 274, surface. + + +31. _Acanthosphaera reticulata_, n. sp. (Pl. 26, fig. 5). + + _Rhaphidosphaera reticulata_, Haeckel, 1881, Prodromus. + +Shell thick walled, with irregular, roundish pores, twice to four times as +broad as the bars; six to eight on the radius. Surface of the bars covered +with a peculiar delicate network of very fine crests. Twenty to forty +radial spines, angular, pyramidal, scarcely one-third as long as the radius +of the shell, as broad at the base as the bars. + +_Dimensions._--Diameter of the shell 0.22, pores 0.02 to 0.04, bars 0.01; +length of the spines 0.04, basal breadth 0.01. + +_Habitat._--Central Pacific, Station 271, depth 2425 fathoms. + + + +Genus 89. _Heliosphaera_,[123] Haeckel, 1862, Monogr. d. Radiol., p. 350 +(_sensu emendato_). + +_Definition._--#Astrosphaerida# with one simple lattice-sphere, covered +with simple radial spines of two different kinds: larger main spines and +smaller by-spines. + +The genus _Heliosphaera_ (in the mended definition here employed) differs +from the foregoing _Acanthosphaera_ in the possession of two different +kinds of radial spines: larger main spines scattered on the surface or +disposed regularly in limited numbers (twelve to twenty, sometimes forty to +fifty or more), and smaller by-spines in much larger numbers, arising from +all the nodal-points of the network (or sometimes also from its bars). + + + +Subgenus 1. _Heliosphaerella_, Haeckel. + +_Definition._--Pores of the shell regular or subregular, all of nearly +equal size and similar form. + + +1. _Heliosphaera hexagonaria_, n. sp. (Pl. 26, fig. 2). + +Shell very thin walled, about twenty times as broad as one pore. Meshes or +pores subregular, hexagonal, with thread-like bars; fifteen to seventeen on +the radius. Radial spines at the nodal-points of the network; about forty +main spines three-sided pyramidal, half as broad at the base as one pore, +and twice as long as the bristle-shaped by-spines, which are very numerous, +and as long as the diameter of one pore. + +{218}_Dimensions._--Diameter of the shell 0.25 to 0.3, of the meshes or +pores 0.012 to 0.015, bars below 0.001; length of the main spines 0.03, +basal breadth 0.007. + +_Habitat._--Central Pacific, Stations 272 to 274, depth 2350 to 2750 +fathoms. + + +2. _Heliosphaera actinota_, Haeckel. + + _Heliosphaera actinota_, Haeckel, 1862, Monogr. d. Radiol., p. 352, Taf. + ix. fig. 3. + +Shell very thin walled, about ten times as broad as one mesh. Pores +regular, hexagonal, with thread-like bars; six to eight on the radius. +Radial spines at the nodal-points of the network, bristle-shaped, scarcely +broader than the bars; about twenty main spines as long as the diameter of +the shell, and numerous by-spines, only one-third to one-half as long as +the former. + +_Dimensions._--Diameter of the shell 0.2 to 0.25, of the meshes 0.02 to +0.03, bars below 0.001; length of the main spines 0.2 to 0.3. + +_Habitat._--Mediterranean (Messina), Atlantic (Canaries, Azores), surface. + + +3. _Heliosphaera echinoides_, Haeckel. + + _Heliosphaera echinoides_, Haeckel, 1862, Monogr. d. Radiol., p. 352, + Taf. ix. fig. 4. + +Shell thin walled, about six times as broad as one mesh. Pores regular, +hexagonal, eight times as broad as the bars. Radial spines arising, not +from the nodal-points of the network, but from the midst of the bars (very +rare disposition!); twenty main spines regularly disposed, as long as the +radius, four times as long as the numerous by-spines; all spines +bristle-shaped, of the same breadth as the bars. + +_Dimensions._--Diameter of the shell 0.09, pores 0.015, bars 0.002; length +of the main spines 0.04. + +_Habitat._--Mediterranean (Messina), surface, Haeckel. + + +4. _Heliosphaera elegans_, Haeckel. + + _Heliosphaera elegans_, Haeckel, 1862, Monogr. d. Radiol., p. 353, Taf. + ix. fig. 5. + +Shell very thin walled, about ten times as broad as one mesh. Pores +regular, hexagonal, with thread-like bars, which are crossed by tangential +bars, so that each side of a hexagon exhibits a regular rectangular cross +(exactly the same as in Pl. 19, fig. 5). All radial spines bristle-shaped, +as thin as the bars, and arising from the nodal-points; twenty main spines +as long as the radius, numerous by-spines scarcely one-sixth as long. + +_Dimensions._--Diameter of the shell 0.26, pores 0.026, bars below 0.001; +length of the main spines 0.13. + +_Habitat._--Mediterranean (Messina), surface, Haeckel. + + +5. _Heliosphaera pectinata_, n. sp. (Pl. 26, fig. 9). + + _Acanthosphaera pectinata_, Haeckel, 1881, Atlas. + +Shell thick walled, combed, about fourteen times as broad as one mesh. +Pores subregular, circular, with elevated hexagonal frames, three times as +broad as the bars. Radial spines very {219}numerous and stout; thirty to +forty main spines, three-sided pyramidal, nearly as long as the radius, as +broad as one mesh; by-spines small, conical, everywhere scattered at the +nodal-points of the network and on the high combs of the bars. + +_Dimensions._--Diameter of the shell 0.16, pores 0.012, bars 0.004; length +of the main spines 0.07, basal breadth 0.016. + +_Habitat._--West Tropical Pacific, Station 225, depth 4475 fathoms. + + +6. _Heliosphaera coronata_, n. sp. (Pl. 26, figs. 6, 6_a_). + + _Acanthosphaera coronata_, Haeckel, 1881, Atlas. + +Shell thick walled, about ten times as broad as one mesh. Pores regular, +circular, five times as broad as the bars; each pore surrounded by a +regular coronal of six short, conical by-spines (fig. 6_a_); twenty to +thirty main spines, also conical, half as long as the radius, as broad as +one pore. + +_Dimensions._--Diameter of the shell 0.15, pores 0.015, bars 0.003; length +of the main spines 0.04, basal breadth 0.015. + +_Habitat._--Central Pacific, Station 272, depth 2600 fathoms. + + +7. _Heliosphaera floribunda_, n. sp. + +Shell thick walled about ten times as broad as one mesh. Pores regular, +six-lobed, twice as broad as the bars; each pore surrounded by six small +conical by-spines (as in Pl. 28, figs. 1, 1_b_); twenty main spines +regularly disposed cylindro-conical, as long as the diameter of the shell +or longer. + +_Dimensions._--Diameter of the shell 0.15, pores 0.015, bars 0.008; length +of the main spines 0.16, breadth 0.008. + +_Habitat._--Central Pacific, Station 268, depth 2900 fathoms. + + +8. _Heliosphaera cristata_, n. sp. + +Shell thick walled, about twelve times as broad as one mesh. Pores +subregular, circular, twice as broad as the bars; each pore surrounded by +an elegant coronal of ten to twenty small, conical by-spines; twenty main +spines regularly disposed, conical, only one-third as long as the radius, +as broad at the base as one mesh. + +_Dimensions._--Diameter of the shell 0.25, pores 0.02, bars 0.01; length of +the main spines 0.04, basal breadth 0.02. + +_Habitat._--South Pacific, Station 285, depth 2375 fathoms. + + +9. _Heliosphaera castanella_, n. sp. + +Shell thick walled, about twenty times as broad as one mesh. Pores regular, +circular, of the same breadth as the bars. Whole surface densely covered +with innumerable bristle-shaped by-spines, half as long as the radius; +fifty to eighty main spines, conical, nearly as long as the diameter, +{220}twice as broad at the base as one pore. (Very similar to some species +of Castanella, Pl. 113, but without the osculum characteristic of this +Phaeodarian; may be easily confounded with it.) + +_Dimensions._--Diameter of the shell 0.3, pores 0.015, bars 0.015; length +of the main spines 0.25, basal breadth 0.03. + +_Habitat._--North Pacific (Japan), Station 234, surface. + + + +Subgenus 2. _Heliosphaeromma_, Haeckel. + +_Definition._--Pores of the shell irregular, of different size or form. + + +10. _Heliosphaera polygonaria_, n. sp. + +Shell very thin walled, with thread-like bars and irregular, polygonal +pores (having four to eight angles, commonly five to seven); eight to ten +on the radius. Radial spines at all the nodal-points of the network, +bristle-shaped; forty to sixty main spines, as long as the radius, twice as +thick as the numerous by-spines, which are not larger than one mesh. + +_Dimensions._--Diameter of the shell 0.15 to 0.2, pores 0.012 to 0.02, bars +0.001; length of the main spines 0.08 to 0.1. + +_Habitat._--Central Pacific, Stations 266 to 272, surface. + + +11. _Heliosphaera heteracantha_, n. sp. + +Shell thin walled, with irregular, polygonal pores, twice to four times as +broad as the bars; six to eight on the radius. Twenty radial main spines, +three-sided pyramidal, nearly as long as the diameter of the shell, as +broad as a larger mesh; innumerable bristle-shaped by-spines variously +distributed on the bars and at the nodal-points of the net; half as long as +the radius. + +_Dimensions._--Diameter of the shell 0.12, pores 0.006 to 0.012, bars +0.003; length of the main spines 0.1, basal breadth 0.012. + +_Habitat._--Equatorial Atlantic, Station 347, surface. + + +12. _Heliosphaera hyperionis_, n. sp. + +Shell thick walled. Pores irregular, roundish, with polygonal frames, three +to six times as broad as the bars; twelve to fourteen on the radius. Thirty +to forty main spines, angular, pyramidal, scarcely as long as the radius +and twice as long as the numerous bristle-shaped by-spines. + +_Dimensions._--Diameter of the shell 0.24, pores 0.006 to 0.012, bars +0.002; length of the main spines 0.1, basal breadth 0.012. + +_Habitat._--North Pacific, Station 256, surface. + + +13. _Heliosphaera elector_, n. sp. + +Shell thick walled, with irregular, roundish pores, twice to three times as +broad as the bars; eight to ten on the radius. Twenty main spines, +three-sided pyramidal, somewhat longer than the radius and four times as +long as the short bristle-shaped by-spines. + +{221}_Dimensions._--Diameter of the shell 0.12, pores 0.005 to 0.01, bars +0.003; length of the main spines 0.08, basal breadth 0.01. + +_Habitat._--South Atlantic, Station 325, surface. + + +14. _Heliosphaera solaris_, n. sp. + +Shell thick walled, with irregular, roundish pores, about the same breadth +as the bars; six to eight on the radius. Fifty to eighty main spines, +conical, as long as the radius; by-spines very numerous, also conical, but +only as large as one pore. + +_Dimensions._--Diameter of the shell 0.15, pores and bars 0.006 to 0.008; +length of the main spines 0.08, basal breadth 0.012. + +_Habitat._--Central Pacific, Station 268, depth 2900 fathoms. + + + +Genus 90. _Conosphaera_,[124] Haeckel, 1881, Prodromus, p. 451. + +_Definition._--#Astrosphaerida# with one simple latticed sphere, covered +with radial spines having the form of hollow cones with porous walls. + +The genus _Conosphaera_ differs from _Acanthosphaera_ in the peculiar +formation of the radial spines, which are not simple solid sticks, but +hollow cones with porous walls, as immediate elevations of the hollow +sphere. + + +1. _Conosphaera platyconus_, n. sp. + +Pores of the shell regular, circular, twice as broad as the bars; ten to +twelve on the radius. Conical spines about sixty, regular, broader than +they are high, with six to nine pores in the wall. + +_Dimensions._--Diameter of the shell 0.16, pores 0.008, bars 0.004; length +of the spines 0.012, basal breadth 0.024. + +_Habitat._--Central Pacific, Station 272, depth 2600 fathoms. + + +2. _Conosphaera orthoconus_, n. sp. (Pl. 12, fig. 2). + +Pores of the shell irregular, roundish, twice to three times as broad as +the bars; fourteen to sixteen on the radius. Conical spines about forty, +regular, higher than they are broad, as long as the radius, with sixteen to +twenty pores in the wall. + +_Dimensions._--Diameter of the shell 0.2, pores 0.008 to 0.012, bars 0.004; +length of the spines 0.05, basal breadth 0.03. + +_Habitat._--Central Pacific, Station 271, depth 2425 fathoms. + + +{222}3. _Conosphaera plagioconus_, n. sp. (Pl. 12, fig. 4). + +Pores of the shell irregular, polygonal, twice to five times as broad as +the bars; twenty to twenty-four on the radius. Conical spines about eighty, +irregularly formed and scattered, with oblique (not radial) axes; about as +high as broad, with eight to twelve pores in the wall. + +_Dimensions._--Diameter of the shell 0.25, pores 0.005 to 0.015, bars +0.003; length of the spines 0.02, basal breadth 0.02. + +_Habitat._--Central Pacific, Station 265, depth 2900 fathoms. + + + +Genus 91. _Coscinomma_,[125] n. gen. + +_Definition._--#Astrosphaerida# with one simple lattice-sphere, covered +with simple radial spines; the pores between them prolonged into hollow, +conical, or cylindrical tubuli. + +The genus _Coscinomma_ exhibits among the Astrosphaerida the same peculiar +formation that distinguishes _Ethmosphaera_ and _Sethosphaera_ among the +Liosphaerida; each pore of the simple shell is prolonged into a short +conical or cylindrical tubulus, as a rule either on the outside or on the +inside of the shell, but sometimes on both sides. + + + +Subgenus 1. _Coscinommarium_, Haeckel. + +_Definition._--Pores prolonged into short tubes both on the inside as well +as the outside of the shell. + + +1. _Coscinomma amphisiphon_, Haeckel (Pl. 26, figs. 1, 1_a_, 1_b_). + +Pores regular, circular, hexagonally framed, twice as broad as the bars, +prolonged on the inside as well as on the outside of the shell into a short +truncated conical tube; fifteen to eighteen pores on the radius. In each +hexagon-corner arises a bristle-shaped radial spine, half as long as the +radius. + +_Dimensions._--Diameter of the shell 0.22, pores 0.01, bars 0.005; length +of the spines 0.1. + +_Habitat._--Central Pacific, Station 271, surface. + + + +Subgenus 2. _Coscinommidium_, Haeckel. + +_Definition._--Pores prolonged into external tubes on the outside of the +shell. + + +2. _Coscinomma ectosiphon_, n. sp. + +Pores regular, circular, hexagonally framed, twice as broad as the bars, +prolonged on the outside of the shell into a short truncated conical tube; +ten to twelve pores on the radius. In each {223}hexagon-corner arises a +short bristle-shaped spine, twice as long as the tube, one-third as long as +the radius. (Very similar to _Ethmosphaera conulosa_, Pl. 12, fig. 5, but +differs in the possession of radial spines.) + +_Dimensions._--Diameter of the shell 0.2, pores 0.012, bars 0.006; length +of the spines 0.04, of the tubes 0.02. + +_Habitat._--North Pacific, Station 253, surface. + + +3. _Coscinomma macrosiphon_, n. sp. + +Pores regular, circular, without hexagonal frames, of the same breadth as +the bars, prolonged on the outside of the shell into a long cylindrical +tube, half as long as the radius (eight to nine pores on the radius); +between them bristle-shaped, at the base conical, radial spines of double +length. + +_Dimensions._--Diameter of the shell 0.16, pores and bars 0.008; length of +the spines 0.08, of the tubes 0.04. + +_Habitat._--Central Pacific, Station 274, surface. + + + +Subgenus 3. _Coscinommonium_, Haeckel. + +_Definition._--Pores prolonged into internal tubes on the inside of the +shell. + + +4. _Coscinomma endosiphon_, n. sp. + +Pores regular, circular, hexagonally framed, twice as broad as the bars +(fourteen to sixteen on the radius), prolonged on the inside of the shell +into a short truncated cylindrical tube. In each hexagon-corner arises a +thin, bristle-shaped, radial spine with pyramidal base, half as long as the +radius, twice as long as the tube. + +_Dimensions._--Diameter of the shell 0.25, pores 0.012, bars 0.006; length +of the spines 0.066, of the tubes 0.03. + +_Habitat._--South Pacific, Station 288, surface. + + + +Genus 92. _Cladococcus_,[126] J. Mueller, 1856, Monatsber. d. k. preuss. +Akad. d. Wiss. Berlin, p. 485. + +_Definition._--#Astrosphaerida# with one simple lattice-sphere, covered +with branched radial spines (the stem of the spine never forked). + +The genus _Cladococcus_, together with the following _Elaphococcus_, is +distinguished from the other _Coscinommida_ by the ramification of the +radial spines covering the surface of the simple hollow lattice-sphere. In +_Cladococcus_ each spine sends out three or more lateral branches, which +are either simple or again ramified; but the stem of the spine itself is +not forked, as in _Elaphococcus_. + + + +{224}Subgenus 1. _Cladococcalis_, Haeckel. + +_Definition._--Branches of the spines simple, not ramified. Pores regular, +all of nearly equal size and similar form. + + +1. _Cladococcus arborescens_, J. Mueller. + + _Cladococcus arborescens_, J. Mueller, 1858, Abhandl. d. k. Akad. d. + Wiss. Berlin, p. 31, Taf. i. fig. 2. + +Pores of the spherical shell regular, hexagonal, three times as broad as +the bars; three to four on the radius. Ten to twenty spines, three-sided +prismatic, two to three times as long as the shell diameter; towards the +distal end each spine with three branches (one lateral simple straight +branch on each edge of the spine). + +_Dimensions._--Diameter of the shell 0.1, pores 0.012, bars 0.004; length +of the spines 0.2 to 0.3, breadth 0.02. + +_Habitat._--Mediterranean (Nice); North Atlantic, Canary Islands, surface. + + +2. _Cladococcus spinifer_, Haeckel. + + _Cladococcus spinifer_, Haeckel, 1862, Monogr. d. Radiol., p. 368, Taf. + xiii. fig. 9. + +Pores regular, circular, hexagonally framed, three times as broad as the +bars; five to six on the radius. Radial spines, arising from all the +nodal-points of the network, three-sided, longer than the shell diameter, +with six to twelve simple verticillate branches (two to four branches on +each edge). + +_Dimensions._--Diameter of the shell 0.08, pores 0.01, bars 0.003; length +of the spines 0.1, breadth 0.03. + +_Habitat._--Mediterranean (Messina), surface. + + +3. _Cladococcus penicillus_, n. sp. + +Pores subregular, hexagonal, twice as broad as the bars; eight to ten on +the radius. Sixty to eighty radial spines, three-sided prismatic, +pencil-shaped, longer than the shell diameter; each at the distal end with +a brush or pencil composed of nine to twenty-one short, simple, curved +branches (three to seven on each edge). + +_Dimensions._--Diameter of the shell 0.1, pores 0.006, bars 0.003; length +of the spines 0.12 to 0.16, breadth 0.006. + +_Habitat._--Central Pacific, Station 271, surface. + + + +Subgenus 2. _Cladococcinus_, Haeckel. + +_Definition._--Branches of the spines simple, not ramified. Pores +irregular, of different size or form. + + +{225}4. _Cladococcus antarcticus_, n. sp. + +Pores irregular, polygonal, twice to four times as broad as the bars; five +to six on the radius. Forty to fifty radial spines, angular, curved, of +variable size and form, with three to nine irregular, simple, blunt curved +branches. + +_Dimensions._--Diameter of the shell 0.14, pores 0.01 to 0.02, bars 0.05; +length of the spines 0.1 to 0.18, breadth 0.007. + +_Habitat._--Antarctic Ocean, Station 157, depth 1950 fathoms. + + +5. _Cladococcus japonicus_, n. sp. + +Pores irregular, roundish, of the same breadth as the bars; six to eight on +the radius. Twenty to thirty radial spines, angular, longer than the shell +diameter, with thirty to forty simple branches, decreasing in size from the +middle part of the spine to the distal end (ten to thirteen branches on +each edge). + +_Dimensions._--Diameter of the shell 0.12, pores and bars 0.007; length of +the spines 0.15 to 0.2, breadth 0.004. + +_Habitat._--North Pacific (Japan), Station 240, surface. + + +6. _Cladococcus quadricuspis_, n. sp. + +Pores irregular, roundish, twice to eight times as broad as the bars; eight +to ten on the radius. About twenty radial spines, three-sided prismatic, as +long as the shell diameter; in the proximal half simple, with smooth edges; +in the distal half with three diverging simple branches, half the length of +the spine, with dentated edges. + +_Dimensions._--Diameter of the shell 0.15, pores 0.004 to 0.016, bars +0.002; length of the spines 0.17, breadth 0.01. + +_Habitat._--Central Pacific, Station 265, depth 2900 fathoms. + + + +Subgenus 3. _Cladococcodes_, Haeckel. + +_Definition._--Branches of the spines again ramified. Pores regular, of +nearly equal size and similar form. + + +7. _Cladococcus scoparius_, n. sp. (Pl. 27, fig. 2). + +Pores regular, circular, three times as broad as the bars; five to six on +the radius. Twenty radial spines, broom-shaped, three times as long as the +shell diameter; in the proximal half simple, in the distal half branched, +with three to nine branches, which are again ramified; spines and their +branches with three smooth edges, not dentated. + +_Dimensions._--Diameter of the shell 0.055, pores 0.0075, bars 0.0025; +length of the spines 0.15, basal thickness 0.007. + +_Habitat._--Central Pacific, Station 271, surface. + + +{226}8. _Cladococcus viminalis_, Haeckel. + + _Cladococcus viminalis_, Haeckel, 1862, Monogr. d. Radiol., p. 369, Taf. + xiv. figs. 2, 3. + +Pores regular, circular, hexagonally framed, four times as broad as the +bars; five to six on the radius. Radial spines, arising from all the +nodal-points of the network, twice as long as the shell diameter; in the +basal half simple, in the distal half with three to six long, thin, curved +branches, which are partly forked; three edges of the spines dentated. + +_Dimensions._--Diameter of the shell 0.08, pores 0.01, bars 0.003; length +of the radial spines 0.16, basal breadth 0.003. + +_Habitat._--Mediterranean (Messina). + + +9. _Cladococcus bifurcus_, Haeckel. + + _Cladococcus bifurcus_, Haeckel, 1862, Monogr. d. Radiol., p. 368, Taf. + xiii. figs. 7, 8. + +Pores regular, circular, hexagonally framed, four times as broad as the +bars; five to seven on the radius. Radial spines arising from all the +nodal-points, three-sided prismatic, with dentated edges, longer than the +shell diameter. On each spine six to nine branches, which are for the most +part forked, the distal branches only being simple. (May be regarded as a +further developmental stage of _Cladococcus spinifer_ and _Cladococcus +viminalis_.) + +_Dimensions._--Diameter of the shell 0.08, pores 0.01, bars 0.0025; length +of the spines 0.1, basal breadth 0.003. + +_Habitat._--Mediterranean (Messina), Canary Islands, Azores, surface. + + +10. _Cladococcus pinetum_, n. sp. (Pl. 27, fig. 1). + +Pores regular, circular, polygonally framed, about the same breadth as the +bars: two to three on the radius. About twenty radial spines, very large, +three to four times as long as the shell diameter, branched like a pine +tree, with straight, stout, three-sided prismatic stem; three prominent +edges dentated. On each edge five to seven lateral branches, the distal +ends of which are simple, the proximal again ramified, with numerous +ramules. The figured specimen is a young one, with branches but little +developed. + +_Dimensions._--Diameter of the shell 0.06, pores and bars 0.008; length of +the spines 0.2 to 0.25 breadth 0.01. + +_Habitat._--Central Pacific, Station 266 to 274, surface. + + + +Subgenus 4. _Cladococcurus_, Haeckel. + +_Definition._--Branches of the spines again ramified. Pores irregular, of +different size and form. + + +11. _Cladococcus abietinus_, n. sp. (Pl. 27, fig. 3). + +Pores irregular, roundish, twice to four times as broad as the bars; six to +ten on the radius. About twenty radial spines, two to three times as long +as the shell diameter, branched like a pine {227}tree, with straight, +stout, three-sided pyramidal stem. From the dentated edges arise numerous +verticillate branches, the proximal ends of which are thickly ramified. +(Differs from the preceding and similar species mainly in the large size +and irregular lattice-work of the shell.) + +_Dimensions._--Diameter of the shell 0.12 to 0.14, pores 0.006 to 0.012, +bars 0.003; length of the spines 0.25 to 0.4, breadth 0.012. + +_Habitat._--North Pacific, Station 256, surface. + + +12. _Cladococcus tricladus_, n. sp. + +Pores irregular, polygonal, twice to eight times as broad as the bars; +eight to ten on the radius. About twenty radial spines, three-sided +prismatic, twice as long as the shell diameter; in the proximal half +simple, with smooth edges; in the distal half with three diverging curved +branches, which bifurcate two to three times or ramify irregularly. +(Closely related to the simpler _Cladococcus quadricuspis_.) + +_Dimensions._--Diameter of the shell 0.16, pores 0.04 to 0.016, bars 0.002; +length of the spines 0.3, breadth 0.012. + +_Habitat._--Central Pacific, Station 268, depth 2900 fathoms. + + +13. _Cladococcus stalactites_, n. sp. (Pl. 27, fig. 4). + +Pores irregular, roundish, once to five times as broad as the bars; eight +to ten on the radius. About twenty radial spines, very stout, longer than +the shell diameter, with three wing-like, prominent smooth edges. At the +middle, or in the distal half, each spine bears a verticil of three strong, +irregularly formed ramified branches. + +_Dimensions._--Diameter of the shell 0.14, pores 0.003 to 0.015, bars +0.003; length of the spines 0.16 to 0.2, breadth 0.02. + +_Habitat._--West Tropical Pacific, Station 220, depth 1100 fathoms. + + +14. _Cladococcus dendrites_, n. sp. (Pl. 27, fig. 5). + +Pores irregular, roundish, with denticulate margin, twice to four times as +broad as the bars; eight to twelve on the radius. Fifty to eighty radial +spines, three-sided prismatic, with elegantly denticulated edges; in the +proximal two-thirds simple, in the distal third with a bunch of ten to +twenty short simple spines (three to seven on each edge). + +_Dimensions._--Diameter of the shell 0.16 to 0.2, pores 0.006 to 0.012, +bars 0.003; length of the spines 0.2 to 0.3, breadth 0.01. + +_Habitat._--Antarctic Ocean, Station 157, depth 1950 fathoms. + + + +Genus 93. _Elaphococcus_,[127] Haeckel, 1881, Prodromus, p. 450. + +_Definition._--#Astrosphaerida# with one simple lattice-sphere, covered +with forked or dichotomously branched radial spines (the stem of the spine +always forked). + +{228}The genus _Elaphococcus_ differs from the preceding _Cladococcus_ in +the mode of ramification of the radial spines. These are forked; and the +forked branches are either simple, again forked, or dichotomously ramified. + + + +Subgenus 1. _Elaphococcinus_, Haeckel. + +_Definition._--Pores of the shell regular, of nearly equal size and similar +form. + + +1. _Elaphococcus furcatus_, n. sp. + +Pores of the spherical shell regular, hexagonal, four times as broad as the +bars; four to five on the radius. Radial spines, arising from all the +nodal-points of the network, cylindrical, as long as the radius, simply +forked at the distal end; both branches half as long as the undivided part. + +_Dimensions._--Diameter of the shell 0.08, pores 0.01, bars 0.0025; length +of the spines 0.04, breadth 0.004. + +_Habitat._--Tropical Atlantic, Station 348, surface. + + +2. _Elaphococcus cervicornis_, Haeckel. + + _Cladococcus cervicornis_, Haeckel, 1862, Monogr. d. Radiol., p. 370, + Taf. xiv. figs. 4-6. + +Pores regular, hexagonal, ten to twenty times as broad as the bars; five to +seven on the radius. Fifty to ninety radial spines (or more), arising not +only from the nodal-points of the network but also from the bars between +them. Each spine is cylindrical, longer than the shell diameter, and +repeatedly forked (three to six times), having, therefore, numerous (thirty +to sixty or more) curved branches. The distal ends of all branches fall in +one spherical face. + +_Dimensions._--Diameter of the shell 0.07 to 0.09, pores 0.01 to 0.015, +bars 0.001 to 0.015; length of the spines 0.1 to 0.15, breadth 0.005. + +_Habitat._--Cosmopolitan; Mediterranean, Atlantic, Indian, Pacific, +surface. + + +3. _Elaphococcus elaphoceras_, n. sp. + +Pores regular, circular, hexagonally framed, three to four times as broad +as the bars; six to eight on the radius. At each nodal-point of the hexagon +arises a short bristle-shaped, simple by-spine. In addition, there arise +from the bars thirty to sixty large main spines, longer than the shell +diameter, repeatedly forked in the same way as in the preceding species. + +_Dimensions._--Diameter of the shell 0.1, pores 0.008, bars 0.002; length +of the spines 0.12, breadth 0.002. + +_Habitat._--Central Pacific, Station 272. depth 2600 fathoms. + + +4. _Elaphococcus umbellifer_, n. sp. + +Pores regular, circular, three times as broad as the bars; ten to twelve on +the radius. Twenty to forty straight cylindrical spines, as long as the +shell diameter, having at the distal end a regular {229}umbel composed of +nine to twelve curved branches of equal length, which are again ramified +and resemble the inflorescence of an umbelliferous plant, the distal ends +of all ramules falling in a spherical face. + +_Dimensions._--Diameter of the shell 0.12, pores 0.006, bars 0.002; length +of the spines 0.14, breadth 0.002. + +_Habitat._--South Atlantic, Station 325, surface. + + + +Subgenus 2. _Elaphococculus_, Haeckel. + +_Definition._--Pores of the shell irregular, of different size or form. + + +5. _Elaphococcus dichotomus_, n. sp. + +Pores irregular, polygonal, twice to four times as broad as the bars; six +to eight on the radius. Thirty to sixty radial spines cylindrical, curved, +as long as the shell diameter, simply forked at the distal end; both +branches one-third as long as the undivided part. + +_Dimensions._--Diameter of the shell 0.15, pores 0.007 to 0.015, bars +0.004; length of the spines 0.2, breadth 0.004. + +_Habitat._--Arctic Ocean, Greenland, surface (Koch). + + +6. _Elaphococcus umbellatus_, n. sp. + +Pores irregular, roundish, or polygonal, twice to five times as broad as +the bars; six to eight on the radius. Forty to sixty radial spines +cylindrical, curved, as long as the shell radius, having at the distal end +an irregular umbel, composed of six to twelve short branches, which are +irregularly ramified or forked. (Differs from the regular _Elaphococcus +umbellifer_ mainly in the irregularity.) + +_Dimensions._--Diameter of the shell 0.14, pores 0.007 to 0.015, bars +0.003; length of the spines 0.12, breadth 0.01. + +_Habitat._--South-east Pacific (Juan Fernandez), Station 299, surface. + + +7. _Elaphococcus drymodes_, n. sp. + +Pores irregular, roundish, little broader than the bars; ten to twelve on +the radius. Eighty to one hundred and twenty (or more) radial spines, +cylindrical, three to four times as long as the shell diameter, irregularly +forked or repeatedly dichotomous (each spine with forty to sixty forked +branches); the distal ends of all branches fall in a spherical plane. +(Differs from the regular _Elaphococcus cervicornis_ mainly in the +irregularity.) + +_Dimensions._--Diameter of the shell 0.1, pores and bars 0.003 to 0.008; +length of the spines 0.3 to 0.4, breadth 0.01. + +_Habitat._--Arctic Ocean, Iceland (Steenstrup). + + + +{230}Subfamily HALIOMMIDA,[128] Haeckel. + +_Diplosphaerida_, Haeckel, 1881, Prodromus, pp. 449, 451. + +_Definition._--#Astrosphaerida# with two concentric spherical +lattice-shells, united by radial beams. + + + +Genus 94. _Haliomma_,[129] Ehrenberg, 1838, Abhandl. d. k. Akad. d. Wiss. +Berlin, p. 128. + +_Definition._--#Astrosphaerida# with one medullary (intracapsular) and one +cortical (extracapsular) shell, which are connected by radial beams, +piercing the central capsule. Shell surface covered with simple radial +spines of the same kind. + +The genus _Haliomma_, one of the oldest known Radiolarian genera, contained +in the catalogue of its discoverer, Ehrenberg, a large number of very +different #Sphaerellaria#, belonging to at least sixteen different genera. +We limit here the conception of the genus to those Haliommida which bear +simple radial spines of one kind on the surface of the cortical shell (the +latter being separated from the medullary shell by the central capsule). + + + +Subgenus 1. _Haliommantha_, Haeckel. + +_Definition._--Pores of the cortical shell regular, of nearly equal size +and similar form; spines on the whole surface (commonly one spine at each +nodal-point). + + +1. _Haliomma hexagonium_, n. sp. + +Cortical shell four times as broad as the medullary shell, both having very +thin thread-like bars, and regular, hexagonal pores (eighteen to twenty on +the radius of the outer, five to six on the radius of the inner shell). The +two shells connected by twenty thin thread-like radial beams. At each +nodal-point of the outer shell arises a bristle-shaped radial spine, half +as long as the radius. (Similar to _Heliosoma radians_, Pl. 28, fig. 3, but +with all the spines equal.) + +_Dimensions._--Diameter of the outer shell 0.2, inner 0.05; pores of the +outer 0.015, of the inner 0.01; length of the spines 0.05. + +_Habitat._--Equatorial Atlantic, Station 347, surface. + + +2. _Haliomma arachnium_, n. sp. + +Cortical shell three times as broad as the medullary shell; pores of the +former regular, hexagonal, with very thin thread-like bars (fourteen to +sixteen on the radius); pores of the latter regular, {231}circular, three +times as broad as the bars (four to five on the radius). The two shells +connected by about forty radial beams. At each nodal-point of the outer +shell arises one bristle-shaped radial spine, twice as long as the diameter +of one hexagonal mesh. + +_Dimensions._--Diameter of the outer shell 0.15, inner 0.05; pores of the +outer 0.012, of the inner 0.006; length of the spines 0.025. + +_Habitat._--Central Pacific, Station 266, surface. + + +3. _Haliomma favosum_, n. sp. + +Cortical shell thick walled, three times as broad as the medullary shell, +with regular, circular, hexagonally framed pores, twice as broad as the +bars; eight to ten on the radius. Medullary shell with simple, circular +pores, of the same breadth as the bars. At each nodal-point of the outer +shell arises a short triangular spine three times as long as one pore. + +_Dimensions._--Diameter of the outer shell 0.12, inner 0.04; pores of the +former 0.01, of the latter 0.005; bars 0.005; length of the spines 0.015. + +_Habitat._--Central Pacific, Station 271 to 274, surface. + + +4. _Haliomma regulare_, n. sp. + +Cortical shell thin walled, nearly twice as broad as the medullary shell, +and connected with it by forty to sixty thin radial beams. Both shells of +the same perfectly regular structure, with an identical number of regular, +circular pores, which are hexagonally framed, four times as broad as the +bars, nine to eleven on the radius. The outer pores are twice as broad as +the inner, exactly corresponding pores. Between every three pores of the +outer surface (in each corner of the cortical hexagon) arises one short +three-sided pyramidal spine, twice as long as the diameter of one pore. + +_Dimensions._--Diameter of the outer shell 0.2, of the inner 0.11; pores of +the former 0.018, of the latter 0.009; length of the spines 0.04. + +_Habitat._--South Atlantic (Tristan da Cunha), Station 332, depth 2200 +fathoms. + + +5. _Haliomma melitomma_, n. sp. (Pl. 20, fig. 4). + + _Melitomma formosum_, Haeckel, 1879, Atlas, _loc. cit._ + +Cortical shell thick walled, two and a half times as broad as the medullary +shell, with regular pores of very elegant structure, twice as broad as the +bars; eight to ten on the radius. The inner opening of each pore is simple, +circular, the outer regular, six-lobed; corresponding to the six lobes are +six short conical spines, which arise from the six corners of the regular +hexagonal frames separating the pores. Pores of the medullary shell simple, +circular, of the same breadth as the bars. The two shells connected only by +six radial beams (in three dimensive axes). + +_Dimensions._--Diameter of the outer shell 0.17, of the inner 0.07; pores +of the former 0.012, of the latter 0.004; length of the spines 0.005 to +0.01. + +_Habitat._--Indian Ocean, Zanzibar, Pullen, depth 2200 fathoms. + + +{232}6. _Haliomma lirianthus_, n. sp. (Pl. 28, figs. 1, 1_a_, 1_b_). + +Cortical shell thick walled, three times as broad as the medullary shell, +with regular, rosette-shaped pores, twice as broad as the bars; eight to +ten on the radius. The regular structure of the elegant pores is the same +as in the preceding species, but without prominent crested frames (fig. +1_b_). Also the medullary shell (fig. 1_a_) is different, much thinner and +smaller, with simple, circular pores, which are three times as broad as the +bars. The two shells are connected by numerous (twenty?) radial beams. + +_Dimensions._--Diameter of the outer shell 0.15, of the inner 0.05; pores +of the former 0.01, of the latter 0.005; length of the spines 0.005 to +0.02. + +_Habitat._--Central Pacific, Station 271, depth 2425 fathoms. + + +7. _Haliomma castanea_, Haeckel. + + _Haliomma castanea_, Haeckel, 1862, Monogr. d. Radiol., p. 428, Taf. + xxiv. fig. 4. + +Cortical shell thick walled, three times as broad as the medullary shell; +pores of both regular, circular, twice as broad as the bars (seven to eight +on the radius of the outer, four to five on the radius of the inner shell), +the two connected by six to twelve (?) strong radial beams. Radial spines +bristle-shaped, with conical bases, twice as long as the diameter of the +cortical pores (one spine at the nodal-point between every three pores). + +_Dimensions._--Diameter of the outer shell 0.1 to 0.15, inner 0.03 to 0.05; +pores of the former 0.005, of the latter 0.003; length of the spines 0.005 +to 0.01. + +_Habitat._--Cosmopolitan; Mediterranean, Atlantic, Indian, Pacific, +surface. + + +8. _Haliomma horridum_, Stoehr. + + _Haliomma horridum_, Stoehr, 1880, Palaeontogr., vol. xxvi. p. 87, Taf. + i. fig. 10. + +Cortical shell thick walled, two and a half times as broad as the medullary +shell. Pores regular, circular, of the same breadth as the bars; eight to +ten on the radius. Radial spines conical, stout, nearly half as long as the +radius. (Differs from the closely allied _Haliomma castanea_ in the smaller +pores and larger spines.) + +_Dimensions._--Diameter of the outer shell 0.14, of the inner 0.06; pores +of the former 0.004, of the latter 0.02. + +_Habitat._--Fossil in Tertiary rocks of Barbados and Sicily; living in the +Atlantic, Station 9, depth 3150 fathoms, and Station 353, depth 2965 +fathoms. + + +9. _Haliomma datura_, n. sp. + +Cortical shell thin walled, only one and a half times as broad as the +medullary shell, both having regular, circular pores, four to six times as +broad as the bars (five to six on the radius of the outer, three to four on +the radius of the inner shell), the two connected by numerous (forty to +sixty?) thin, short, radial beams. Radial spines conical, twice as long as +the diameter of one cortical pore, arising from all the nodal-points +between them. + +{233}_Dimensions._--Diameter of the outer shell 0.08 to 0.12, inner 0.06 to +0.08; pores of the former 0.015 to 0.02, of the latter 0.007 to 0.012; +length of the spines 0.02. + +_Habitat._--Central Pacific, Stations 268 to 274, surface. + + + +Subgenus 2. _Haliommetta_, Haeckel. + +_Definition._--Pores of the cortical shell regular, of nearly equal size +and similar form; the spines not covering the entire surface, but scattered +at intervals (their number smaller than that of the nodal-points of the +network). + + +10. _Haliomma circumtextum_, n. sp. (Pl. 28, figs. 7, 7_a_). + +Cortical shell very delicate, with thin thread-like bars, and regular, +hexagonal pores, little larger than the thick-walled medullary shell (= +7 : 6). Pores of the latter regular, circular, double-edged, with hexagonal +frames, of the same breadth as the bars; from all the hexagon-corners arise +thin bristle-shaped, radial spines, twice as long as the diameter of the +pores, becoming connected at equal distances from the centre by tangential +threads, regularly disposed, forming the cortical shell. Twelve strong, +three-sided pyramidal, radial spines, as broad at the base as one mesh, and +about half as long as the radius of the shell. + +_Dimensions._--Diameter of the outer shell 0.14, of the inner 0.12; pores +of the former 0.012, of the latter 0.005; length of the radial spines 0.04, +basal breadth 0.012. + +_Habitat._--Central Pacific, Station 271, depth 2425 fathoms. + + +11. _Haliomma duodecinum_, n. sp. + +Cortical shell thick walled, three times as broad as the medullary shell. +Both shells with regular, circular pores, twice as broad as the bars; eight +to ten on the radius of the outer, five to six on the radius of the inner +shell. Twelve conical, regularly disposed radial spines, as long as the +radius, and as broad at the base as one mesh. + +_Dimensions._--Diameter of the outer shell 0.12, of the inner 0.04; pores +of the former 0.005, of the latter 0.002; length of the spines 0.05, basal +breadth 0.005. + +_Habitat._--Central Pacific, Station 265, depth 2900 fathoms. + + +12. _Haliomma megaporum_, Ehrenberg. + + _Haliomma megaporum_, Ehrenberg, 1872, Monatsber. d. k. preuss. Akad. d. + Wiss. Berlin, p. 313. + +Cortical shell thin walled, three times as broad as the medullary shell; +the pores regular, circular, three to four on the radius, eight times as +broad as the bars, quite as broad as the medullary shell, the pores of +which are much smaller, twice as broad as the bars. Eight radial spines +regularly disposed, conical, as long as the radius. (As the diagnosis of +Ehrenberg is very {234}incomplete, and no figure is given with it, it +remains doubtful whether his Mediterranean species be identical with my +Atlantic variety.) + +_Dimensions._--Diameter of the outer shell 0.12, of the inner 0.04; pores +of the former 0.04, of the latter 0.008; length of the spines 0.06. + +_Habitat._--Mediterranean (Grecian shore); North Atlantic, Station 354, +surface. + + +13. _Haliomma oculatum_, Ehrenberg. + + _Haliomma oculatum_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. + Berlin, p. 74, Taf. xxviii. figs. 2, 3. + +Cortical shell thick walled, four times as broad as the medullary shell; +its pores regular, circular, four times as broad as the bars, six to eight +on the radius. Pores of the medullary shell regular, hexagonal, with very +thin bars, three to four on the radius. Nine radial spines, regularly +disposed, conical, as long as the radius, as broad at the base as one +cortical pore. (In the specimen figured by Ehrenberg, only two spines were +preserved, seven being accidentally broken off.) + +_Dimensions._--Diameter of the outer shell 0.16, of the inner 0.04; pores +of the former 0.01, of the latter 0.005. + +_Habitat._--Fossil in Barbados. + + +14. _Haliomma enneaxiphos_, n. sp. + +Cortical shell thick walled, four times as broad as the dark medullary +shell, with regular, circular, hexagonally framed pores, twice as broad as +the bars; eight to ten on the radius. Nine radial spines regularly +disposed, three sided pyramidal, as long as the radius, as broad at the +base as one mesh. + +_Dimensions._--Diameter of the outer shell 0.11, of the inner 0.03; +cortical pores 0.008, bars 0.004; length of the radial spines 0.05, basal +breadth 0.012. + +_Habitat._--Central Pacific, Station 272, surface. + + +15. _Haliomma tenuispinum_, J. Mueller. + + _Haliomma tenuispinum_, J. Mueller, 1858, Abhandl. d. k. Akad. d. Wiss. + Berlin, p. 39, Taf. iv. fig. 9. + + _Haliomma tenuispinum_, Haeckel, 1862, Monogr. d. Radiol., p. 431. + +Cortical shell thin walled, three times as broad as the medullary shell. +Both shells with very fine, thread-like bars, and regular, hexagonal pores; +five to seven on the radius. Twenty radial spines, very thin, +bristle-shaped, as long as the radius. + +_Dimensions._--Diameter of the outer shell 0.12, of the inner 0.04; pores +of the former 0.016, of the latter 0.006. + +_Habitat._--Mediterranean (Nice); North Atlantic, Station 353, surface. + + +{235}16. _Haliomma longispinum_, J. Mueller. + + _Haliomma longispinum_, J. Mueller, 1858, Abhandl. d. k. Akad. d. Wiss. + Berlin, p. 39, Taf iv. fig. 8. + + _Haliomma longispinum_, Haeckel, 1862, Monogr. d. Radiol., p. 431. + +Cortical shell thick walled, three times as broad as the dark medullary +shell. Pores regular, circular, hexagonally framed, twice as broad as the +bars; four to six on the radius. Twenty radial spines, very long, regularly +disposed, four to five times as long as the diameter of the shell, +three-sided prismatic, with elegantly dentated edges, as broad as one +cortical mesh. + +_Dimensions._--Diameter of the outer shell 0.08, of the inner 0.03; pores +of the former 0.01, bars 0.005; length of the spines 0.3 to 0.4. + +_Habitat._--Mediterranean (Nice); Central Pacific, Station 272, surface. + + +17. _Haliomma capense_, n. sp. + +Cortical shell thick walled, twice as broad as the medullary shell, both +with regular, circular pores, twice as broad as the bars; eight to ten on +the radius of the outer, four to six on the radius of the inner shell. +Forty to sixty radial spines, conical, as long as the radius, as broad as +one cortical pore. + +_Dimensions._--Diameter of the outer shell 0.11, of the inner 0.05; pores +of the former 0.01, bars 0.005; length of the spines 0.006, basal breadth +0.012. + +_Habitat._--Cape of Good Hope, Station 142, surface. + + +18. _Haliomma denticulatum_, n. sp. + +Cortical shell thick walled, three times as broad as the dark medullary +shell, with regular, circular, double-edged pores, of the same breadth as +the bars; eight to ten on the radius. Thirty to fifty radial spines, +three-sided pyramidal, half as long as the radius, with three denticulated +edges. (Very similar to _Actinomma denticulatum_, Pl. 29, fig. 3, but with +simple medullary shell.) + +_Dimensions._--Diameter of the outer shell 0.12, inner 0.04; pores and bars +of the former 0.008; length of the spines 0.04, basal breadth 0.01. + +_Habitat._--North Pacific, Station 244, depth 2900 fathoms. + + +19. _Haliomma grande_, n. sp. + +Cortical shell thick walled, five times as broad as the dark medullary +shell, with small, regular, circular pores, half as broad as the bars; +twenty to twenty-four on the radius. One hundred to one hundred and twenty +conical radial spines, five times as long as broad, only half as long as +the radius. + +_Dimensions._--Diameter of the outer shell 0.4, inner 0.08; pores of the +outer 0.006, bars 0.012; length of the spines 0.1, basal breadth 0.02. + +_Habitat._--Equatorial Atlantic, Station 348, depth 2450 fathoms. + + + +{236}Subgenus 3. _Haliommilla_, Haeckel. + +_Definition._--Pores of the cortical shell irregular, of different size and +form; spines covering the entire surface (commonly one spine at each +nodal-point). + + +20. _Haliomma capillaceum_, Haeckel. + + _Haliomma capillaceum_, Haeckel, 1862, Monogr. d. Radiol., p. 426, Taf. + xxiii. fig. 2. + +Cortical shell very thin walled, seven to eight times as broad as the +medullary shell, both with irregular, polygonal pores, and very thin +thread-like bars; outer pores twice to three times as broad as the inner. +Radial spines very numerous, straight, bristle-shaped, about as long as the +diameter of the medullary shell. + +_Dimensions._--Diameter of the outer shell 0.2, inner 0.025 to 0.03; outer +pores 0.02 to 0.04, inner 0.008 to 0.016, bars 0.001; length of the spines +0.02 to 0.03. + +_Habitat._--Mediterranean (Messina), Atlantic (Canary Islands), surface. + + +21. _Haliomma erinaceum_, Haeckel. + + _Haliomma erinaceum_, Haeckel, 1862, Monogr. d. Radiol., p. 427, Taf. + xxiii. figs. 3, 4. + +Cortical shell thin walled, seven to eight times as broad as the medullary +shell, both with irregular, polygonal pores, two to ten times as broad as +the bars, outer pores much larger than the inner. Radial spines very +numerous, bristle-shaped, as long as the diameter of the medullary shell, +the majority or all being either curved or obliquely depressed, the greater +part neither straight nor radial. + +_Dimensions._--Diameter of the outer shell 0.2, inner 0.025 to 0.03; outer +pores 0.005 to 0.03, inner 0.008 to 0.016, bars 0.002 to 0.004; length of +the spines 0.03. + +_Habitat._--Cosmopolitan; Mediterranean, Atlantic, Pacific, surface. + + +22. _Haliomma tenellum_, Haeckel. + + _Haliomma tenellum_, Haeckel, 1862, Monogr. d. Radiol., p. 428. + + _Haliomma spinuloso affine_, J. Mueller, 1858, Abhandl. d. k. Akad. d. + Wiss. Berlin, p. 40, Taf. iv. fig. 7. + +Cortical shell thin walled, three times as broad as the medullary shell, +with irregular, roundish pores, and very thin bars. Pores of the inner +shell regular, circular. Radial spines very numerous, bristle-shaped, +straight, as long as the radius of the outer shell. + +_Dimensions._--Diameter of the outer shell 0.15, inner 0.05; outer pores +0.008 to 0.016, inner 0.005; length of the spines 0.07. + +_Habitat._--Mediterranean (Nice); Atlantic, Stations 349 to 354, surface. + + +{237}23. _Haliomma spinulosum_, J. Mueller. + + _Haliomma spinulosum_, J. Mueller, 1858, Abhandl. d. k. Akad. d. Wiss. + Berlin, p. 39, Taf. iv. fig. 6. + +Cortical shell thin walled, twice as broad as the medullary shell, with +irregular, polygonal pores, and very thin bars. Pores of the inner shell +subregular, hexagonal, ten to twelve times as broad as the bars. Radial +spines very numerous, bristle-shaped, one-sixth to one-fourth as long as +the radius of the outer shell. + +_Dimensions._--Diameter of the outer shell 0.16, inner 0.08; outer pores +0.01 to 0.03, inner 0.02; length of the spines 0.02 to 0.03. + +_Habitat._--Mediterranean (Nice); Central Pacific, Station 266, surface. + + +24. _Haliomma rhodococcus_, n. sp. (Pl. 19, fig. 6). + + _Sethosphaera rhodococcus_, Haeckel, 1879, Atlas, pl. xix. fig. 6. + +Cortical shell very thin walled, little larger than the thick walled +medullary shell (= 10 : 9). Pores of the outer shell very irregular, +roundish, twice to six times as broad as the bars, about twenty on the +radius. Pores of the inner shell twice as broad as the bars, six to eight +on the radius, very regular, circular on the inner, six-lobed on the outer +opening, separated by prominent hexagonal crests; in the hexagon-corners +arise short conical radial spines, which at equal distances from the centre +are united by the outer shell, but are prominent over its surface. (A very +peculiar form; the two shells may better be regarded as inner and outer +cortical shell.) + +_Dimensions._--Diameter of the outer shell 0.2, inner 0.18; outer pores +0.04 to 0.012, inner 0.01; length of the spines 0.01. + +_Habitat._--Tropical Atlantic, Station 338, depth 1990 fathoms; also fossil +in Barbados. + + +25. _Haliomma boreale_, n. sp. + +Cortical shell thick walled, four times as broad as the medullary shell, +with irregular, roundish pores, twice to four times as broad as the bars; +eight to ten on the radius. Pores of the inner shell regular, circular, +twice as broad as the bars, four to six on the radius. Radial spines very +numerous, conical, nearly as long as the diameter of the shell. + +_Dimensions._--Diameter of the outer shell 0.24, inner 0.06; outer pores +0.008 to 0.02, bars 0.005, inner pores 0.006, bars 0.003; length of the +spines 0.2. + +_Habitat._--Arctic Ocean, Greenland ("Alert" Expedition). + + + +Subgenus 4. _Haliommura_, Haeckel. + +_Definition._--Pores of the cortical shell irregular, of different size and +form; spines not covering the entire surface, but scattered at intervals +(their number smaller than that of the nodal-points in the network). + + +{238}26. _Haliomma macrodoras_, n. sp. (Pl. 28, figs. 6, 6_a_). + +Cortical shell thin walled, twice as broad as the medullary shell, with +irregular, polygonal meshes, three to six times as broad as the bars. Inner +shell with regular, hexagonal meshes, ten times as broad as the bars. +Twenty radial spines, very long, stout, three-sided prismatic, two to four +times as long as the diameter of the shell, as broad as one medullary mesh, +with three wing-like, denticulated edges. At the base of each spine three +supporting curved beams. + +_Dimensions._--Diameter of the outer shell 0.14 to 0.16, of the inner 0.07 +to 0.08; outer pores 0.01 to 0.02, bars 0.003; inner pores 0.01, bars +0.001; length of the spines 0.3 to 0.6, breadth 0.01. + +_Habitat._--Central Pacific, Station 271, surface. + + +27. _Haliomma antarcticum_, n. sp. + +Cortical shell very thin walled, three times as broad as the medullary +shell, with irregular, polygonal pores, and very thin thread-like bars. +Inner shell with regular, hexagonal meshes, six times as broad as the bars. +About forty radial spines, angular, pyramidal, half as long as the radius +of the shell, as broad at the base as the largest mesh. + +_Dimensions._--Diameter of the outer shell 0.2, of the inner 0.07; outer +pores 0.006 to 0.015, inner 0.008; length of the spines 0.05, basal breadth +0.012. + +_Habitat._--Antarctic Ocean, Station 154, surface. + + +28. _Haliomma wyvillei_, Haeckel. + + _Haliomma wyvillei_, Haeckel, 1878, Protistenreich, p. 44, fig. 31. + + _Haliomma species_, Wyville Thomson, 1877, Atlantic, vol. i. p. 236, fig. + 54. + +Cortical shell thin walled, three times as broad as the medullary shell. +Both shells with irregular, large, polygonal pores, and very thin bars. +From the inner shell arise very numerous (eighty to one hundred and twenty +or more) radial spines, which pierce the outer shell, and are outside it, +as long as the radius of the inner shell, straight, bristle-shaped, and as +thick as the bars. + +_Dimensions._--Diameter of the outer shell 0.18, of the inner 0.06; pores +0.01 to 0.02, bars 0.001 to 0.002; length of the free spines 0.06. + +_Habitat._--Central Pacific, Stations 266 to 274, surface. + + +29. _Haliomma beroes_, Ehrenberg. + + _Haliomma beroes_, Ehrenberg, 1854, Mikrogeol., Taf. xxxvB. B. iv. fig. + 19. + + _Haliomma beroes_, Haeckel, 1862, Monogr. d. Radiol., p. 434. + +Cortical shell thin walled, three times as broad as the medullary shell, +with irregular, roundish pores, twice to four times as broad as the bars. +Inner shell with regular, circular pores, twice as broad as the bars. Both +shells connected by four (or six ?) radial beams, perpendicularly crossed. +Thirty to forty radial spines, conical, thin, shorter than the radius. + +_Dimensions._--Diameter of the outer shell 0.11, inner 0.04; outer pores +0.007 to 0.012, inner 0.005; length of the spines 0.03, basal breadth +0.005. + +_Habitat._--Atlantic, depth 2000 fathoms. + + +{239}30. _Haliomma compactum_, n. sp. (Pl. 28, figs. 5, 5_a_). + +Cortical shell very thick walled, four times as broad as the thin walled +medullary shell; pores of the former irregular, roundish, with high +polygonal frames of very different size, twice to four times as broad as +the bars. Inner shell with simple, small, polygonal pores, connected with +the outer shell by eight (?) regularly disposed thin radial beams, opposite +in pairs, prolonged outside into strong conical spines, longer than the +radius. + +_Dimensions._--Diameter of the outer shell 0.08, inner 0.02; outer pores +0.005 to 0.01, inner 0.005; length of the spines 0.06, basal breadth 0.012. + +_Habitat._--Central Pacific, Stations 265 to 272, depth 2425 to 2925 +fathoms. + + +31. _Haliomma permagnum_, n. sp. + +Cortical shell thick walled, six times as broad as the medullary shell, +with irregular, roundish, double-edged pores, three to six times as broad +as the bars. Inner shell with regular, circular pores, twice as broad as +the bars. One hundred and twenty to one hundred and fifty radial spines, +conical, only one-fourth as long as the radius. + +_Dimensions._--Diameter of the outer shell 0.42, inner 0.07; outer pores +0.012 to 0.025, bars 0.004; inner pores 0.008, bars 0.004; length of the +spines 0.05, basal breadth 0.03. + +_Habitat._--Central Pacific, Station 268, surface. + + +32. _Haliomma patagonicum_, n. sp. + +Cortical shell thick walled, four times as broad as the medullary shell, +with irregular, roundish pores, twice to three times as broad as the bars. +Inner shell also with irregular, roundish pores, of half the size. Forty to +fifty radial spines, cylindro-conical, about as long as the shell diameter. + +_Dimensions._--Diameter of the outer shell 0.24, inner 0.06; outer pores +0.012 to 0.02, bars 0.006; inner pores 0.005 to 0.01, bars 0.004; length of +the spines 0.3, breadth 0.02. + +_Habitat._--South-east Pacific, west coast of Patagonia, Station 302, +surface. + + +33. _Haliomma clavatum_, n. sp. + +Cortical shell thick walled, three times as broad as the medullary shell, +with irregular, roundish pores little larger than the bars; eight to twelve +on the radius. Inner shell with similar but smaller pores. About twenty +radial spines, club-shaped, as long as the radius, three-sided, with +prominent edges, twice as broad at the distal end as at the base. (Similar +to _Acanthosphaera clavata_, Pl. 26, fig. 8, but differs from it in the +possession of a medullary shell.) + +_Dimensions._--Diameter of the outer shell 0.2, inner 0.06; outer pores and +bars 0.008 to 0.02, inner 0.006 to 0.01; length of the spines 0.1, distal +breadth 0.03. + +_Habitat._--Central Pacific, Station 265, depth 2900 fathoms. + + + +{240}Genus 95. _Heliosoma_,[130] Haeckel, 1881, Prodromus, p. 452. + +_Definition._--#Astrosphaerida# with one medullary (intracapsular) and one +cortical (extracapsular) shell, the two being connected by radial beams +piercing the central capsule. Shell surface covered with simple radial +spines of two different kinds; larger main spines and smaller by-spines. + +The genus _Heliosoma_ differs from the preceding _Haliomma_ in the +possession of two different kinds of radial spines, and exhibits therefore +the same relation to it that _Heliosphaera_ bears to _Acanthosphaera_ among +the Coscinommida. The smaller by-spines are much more numerous than the +larger main spines. + + + +Subgenus 1. _Heliosomantha_, Haeckel. + +_Definition._--Pores of the cortical shell regular, of nearly equal size +and similar form. + + +1. _Heliosoma radians_, n. sp. (Pl. 28, figs. 3, 3_a_). + +Cortical shell very thin walled, with thread-like bars and regular, +hexagonal meshes; twenty to twenty-two on the radius. Medullary shell only +one-fifth as large, of the same structure. The two shells connected by +twenty very thin radial beams, which are prolonged outside into twenty +stout, three-sided pyramidal main spines, as long as the diameter of the +inner shell. Between these, arising from the surface, numerous +bristle-shaped by-spines. + +_Dimensions._--Diameter of the outer shell 0.25, inner 0.05, pores 0.012; +length of the main spines 0.05, basal breadth 0.012. + +_Habitat._--Central Pacific, Stations 266 to 274, surface. + + +2. _Heliosoma elegans_, n. sp. + +Cortical shell thick walled, with regular, circular, hexagonally framed +pores, twice as broad as the bars; ten to twelve on the radius. Medullary +shell half as large, with simple, regular, circular pores, twice as broad +as the bars. The two shells connected by twenty very thin radial beams, +which are prolonged outside into twenty slender, three-sided pyramidal main +spines as long as the radius. In each corner of the surface hexagons a +bristle-shaped by-spine one-fourth as long. + +_Dimensions._--Diameter of the outer shell 0.12, inner 0.06; outer pores +0.006, bars 0.003; length of the main spines 0.05, basal breadth 0.01. + +_Habitat._--Central Pacific, Station 271, surface. + + +3. _Heliosoma echinaster_, Haeckel. + + _Haliomma echinaster_, Haeckel, 1862, Monogr. d. Radiol., p. 429, Taf. + xxiv. figs. 1-3. + +Cortical shell thin walled, with regular, circular, hexagonally framed +pores, twice as broad as the bars; ten to twelve on the radius. Medullary +shell one-fourth as large, with few irregular, large, {241}polygonal pores +and very thin thread-like bars, connected with the former by nine similar +thin radial beams, which are prolonged outside into nine pyramidal main +spines, as long as the radius. From each corner of the surface hexagon +arises a bristle-shaped by-spine, half as long as the main spine. + +_Dimensions._--Diameter of the outer shell 0.16, inner 0.04; outer pores +0.008, bars 0.004; length of the main spines 0.08, basal breadth 0.01. + +_Habitat._--Mediterranean (Messina), surface. + + +4. _Heliosoma duodecilla_, n. sp. + +Cortical shell thick walled, with regular, circular pores, of the same +breadth as the bars; sixteen to eighteen on the radius. Medullary shell +one-third as large, of the same structure. Twelve radial main spines, +regularly disposed, cylindro-conical, longer than the shell diameter, as +broad as two pores. Whole surface covered with short conical by-spines. + +_Dimensions._--Diameter of the outer shell 0.15, inner 0.05; outer pores +and bars 0.007; length of the main spines 0.2, breadth 0.02. + +_Habitat._--South Atlantic, Station 333, surface. + + + +Subgenus 2. _Heliosomura_, Haeckel. + +_Definition._--Pores of the cortical shell irregular, of different size and +form. + + +5. _Heliosoma hastatum_, n. sp. (Pl. 28, fig. 4). + +Cortical shell very thin walled, with large, irregular, polygonal meshes, +three to six times as broad as the bars; four to six on the radius. +Medullary shell one-third as large, with small, regular, circular pores. +The two shells connected by twelve regularly disposed radial beams, which +are prolonged outside into twelve very stout three-sided pyramidal main +spines, somewhat longer than the radius, spear-shaped; each of the three +wings in the middle part with one tooth. Scattered on the surface numerous +by-spines of the same form, half as long and only one-fourth as broad. + +_Dimensions._--Diameter of the outer shell 0.1, inner 0.033; outer pores +0.006 to 0.013, inner pores 0.002, bars 0.002; length of the main spines +0.06, breadth 0.015. + +_Habitat._--Central Pacific, Station 271, depth 2425 fathoms. + + +6. _Heliosoma indicum_, n. sp. + +Cortical shell thick walled, with irregular, roundish pores, twice to five +times as broad as the bars. Medullary shell of the same structure, only +one-fourth as large. Thirty to forty conical main spines, as long as the +radius; between them numerous bristle-shaped by-spines, only half as long. + +_Dimensions._--Diameter of the outer shell 0.2, inner 0.05; outer pores +0.004 to 0.01, bars 0.002; length of the main spines 0.1, breadth 0.01. + +_Habitat._--Indian Ocean, between Aden and Socotora, surface, Haeckel. + + + +{242}Genus 96. _Elatomma_,[131] n. gen. + +_Definition._--#Astrosphaerida# with one medullary (intracapsular) and one +cortical (extracapsular) shell, the two being connected by radial beams +piercing the central capsule. Shell surface covered with branched radial +spines. + +The genus _Elatomma_ differs from _Haliomma_ in the ramification of the +radial spines, and exhibits therefore the same relation to it that +_Cladococcus_, among the Coscinommida, bears to _Acanthosphaera_. + + + +Subgenus 1. _Elatommella_, Haeckel. + +_Definition._--Pores of the cortical shell regular, of nearly equal size +and similar form. + + +1. _Elatomma pinetum_, n. sp. + +Cortical shell thick walled, with regular, circular, hexagonally framed +pores, three times as broad as the bars. From its surface arise twenty to +thirty large, three-sided prismatic, radial spines as long as the shell +diameter, branched like a pine tree; on each edge of the spine five to six +ramified branches, decreasing in size towards the distal end. Similar to +_Cladococcus pinetum_ (Pl. 27, figs. 1, 3), but differing in the possession +of a medullary shell (one-third as large as the outer), with regular, +circular pores, as broad as the bars. + +_Dimensions._--Diameter of the outer shell 0.2, inner 0.07; cortical pores +0.012, bars 0.004; length of the spines 0.2 to 0.24. + +_Habitat._--Central Pacific, Stations 266 to 272, surface. + + +2. _Elatomma scoparium_, n. sp. + +Cortical shell thick walled, with regular, circular pores, twice as broad +as the bars, connected with the medullary shell by twenty thin radial +beams, which are prolonged outside into twenty large cylindrical radial +spines somewhat longer than the radius; in the proximal half simple, in the +distal half with six to nine dichotomous, irregular branches. Similar to +_Cladococcus scoparius_ (Pl. 27, fig. 2), but much larger, and with a large +medullary shell (one-third as broad as the outer), and regular, circular +pores. + +_Dimensions._--Diameter of the outer shell 0.12, inner 0.04; cortical pores +0.01, bars 0.005; length of the spines 0.08. + +_Habitat._--North Pacific, Station 240, surface. + + + +Subgenus 2. _Elatommura_, Haeckel. + +_Definition._--Pores of the cortical shell irregular, of different size or +form. + + +{243}3. _Elatomma juniperinum_, n. sp. (Pl. 28, fig. 8). + +Cortical shell thin walled, with regular, polygonal, or roundish pores, +twice to four times as broad as the bars, connected with the small +medullary shell by about twenty thin radial beams. Inner shell only +one-eighth as broad as the outer, with few irregular, polygonal meshes. +Surface covered with very numerous (one hundred to one hundred and fifty or +more) branched conical radial spines, one-third as long as the shell +radius, with six to twelve short lateral branches. + +_Dimensions._--Diameter of the outer shell 0.2, inner 0.025; cortical pores +0.08 to 0.016, bars 0.004; length of the spines 0.04. + +_Habitat._--Central Pacific, Station 271, surface. + + +4. _Elatomma penicillus_, n. sp. + +Cortical shell thin walled, with irregular, polygonal pores, twice to four +times as broad as the bars, connected with the medullary shell by twenty +(or more?) very thin beams. These are prolonged outside into twenty +straight, three-sided prismatic, radial spines as long as the radius, with +a brush-like bunch of six to nine short, irregularly ramified branches at +the end. Medullary shell very delicate (half as broad as the outer), with +regular, hexagonal meshes and thread-like bars. + +_Dimensions._--Diameter of the outer shell 0.15, inner 0.08; length of the +spines 0.08. + +_Habitat._--West coast of Norway, Bergen, Haeckel. + + +5. _Elatomma irregulare_, n. sp. + +Cortical shell thin walled, with irregular, polygonal, or roundish meshes, +twice to six times as broad as the bars; the medullary shell of the same +structure, half as broad, with smaller irregular pores. Forty to sixty +curved, three-sided, radial spines, as long as the shell, with a bunch of +very irregular, curved, and partly ramified branches at the distal end. + +_Dimensions._--Diameter of the outer shell 0.2, inner 0.1; length of the +spines 0.2, breadth 0.01. + +_Habitat._--North Atlantic, Gulf Stream, Faeroee Channel, surface, John +Murray. + + + +Genus 97. _Leptosphaera_,[132] n. gen. + +_Definition._--#Astrosphaerida# with two extracapsular cortical shells +without by-spines, connected by long prismatic radial spines. + +The genus _Leptosphaera_, together with the three following genera, forms +the very peculiar and typical small group of #Sphaeroidea# which we call +the Diplosphaerida (with four genera and twenty-four species); their shell +is composed of two concentric spheres as in the three foregoing genera; but +whilst in these the inner shell is an intracapsular medullary shell and the +outer an extracapsular cortical shell, in the Diplosphaerida {244}both +shells are extracapsular or cortical shells, therefore the inner shell of +the latter corresponds to the outer of the former. The inner spherical +shell of all Diplosphaerida is composed of very delicate beams and large +pores, which are either regular hexagonal or irregular polygonal (never +roundish). From its surface arise a variable number (twenty to thirty) of +stout long radial spines, which are invariably longer than the shell +diameter (often two to three times as long or more), and of three-sided +prismatic form, the three edges either smooth or serrate, often with three +rows of lateral branches (commonly three to five branches in each row); the +latter are invariably of the same form, concavely curved towards the spine, +and decrease in size towards the distal end. From the three edges of each +main spine in all Diplosphaerida, at equal distances from the centre, arise +six very thin, thread-like lateral branches (a pair from each edge) and +connect the spine in a tangential direction with all neighbouring spines. +In this manner the polyhedral outer shell is formed, the meshes of which +therefore are always very large and triangular. Sometimes each of these +primary triangular meshes becomes filled up with a secondary network, +either of regular quadrangular or of irregular polygonal secondary meshes. +Besides the constant twenty to thirty large main spines, in the majority of +Diplosphaerida bristle-shaped radial by-spines arise, either from the inner +shell (_Diplosphaera_) or from the outer (_Drymosphaera_), or from both +(_Astrosphaera_). They are absent only in _Leptosphaera_. Commonly the +by-spines are simple, rarely forked or branched. The central capsule in the +Diplosphaerida is usually enclosed in the inner shell; often it completely +fills up the latter, or drives out a caecal protuberance through each mesh; +but these processes rarely unite outside. The average size of the +Diplosphaerida, which are all pelagic organisms, is much larger than that +of the other Haliommida. + + + +Subgenus 1. _Leptosphaerella_, Haeckel. + +_Definition._--Radial spines simple, without lateral branches. + + +1. _Leptosphaera hexagonalis_, n. sp. (Pl. 19, fig. 2). + +Inner shell with regular, hexagonal meshes, and very thin, thread-like +bars; outer shell twice as broad, with simple triangular meshes. Radial +spines with three smooth edges. (Fig. 2 represents the central capsule with +numerous club-shaped saccules, prominent externally through the meshes; in +the centre a large simple spherical nucleus, one-third as broad as the +capsule. The skeleton of this species is identical with that of +_Diplosphaera hexagonalis_, Pl. 19, fig. 3, but has no by-spines.) + +_Dimensions._--Diameter of the outer shell 0.3, of the inner 0.15. + +_Habitat._--Cosmopolitan; Mediterranean (Corfu), North Atlantic (Canary +Islands), Tropical Pacific, surface. + + +{245}2. _Leptosphaera serrata_, n. sp. + +Inner shell with regular, hexagonal meshes, five to six times as broad as +the bars; outer shell three times as broad, with simple triangular meshes. +Radial spines with three serrated edges (of the same form as the main +spines of _Drymosphaera dendrophora_, Pl. 20, fig. 1). + +_Dimensions._--Diameter of the outer shell 0.45, of the inner 0.15. + +_Habitat._--Central Pacific, Station 271, surface. + + +3. _Leptosphaera polygonalis_, n. sp. + +Inner shell with irregular, polygonal meshes and very thin thread-like +bars; outer shell twice as broad, with simple triangular meshes. Radial +spines with three smooth edges. (Resembles _Drymosphaera polygonalis_, Pl. +19, fig. 1, but has no by-spines.) + +_Dimensions._--Diameter of the outer shell 0.35, inner 0.175. + +_Habitat._--North Pacific, Station 256, surface. + + + +Subgenus 2. _Leptosphaeromma_, Haeckel. + +_Definition._--Radial spines with three rows of lateral branches (one row +on each edge). + + +4. _Leptosphaera ciliata_, n. sp. + +Inner shell with regular, hexagonal meshes and very thin thread-like bars; +outer shell three times as broad, with simple triangular meshes. Radial +spines with smooth edges and three rows of simple, smooth, curved, lateral +branches (six branches on each edge), similar to those of _Diplosphaera +gracilis_. + +_Dimensions._--Diameter of the outer shell 0.6, inner 0.2. + +_Habitat._--South Atlantic, Station 325, surface. + + +5. _Leptosphaera spinosa_, Haeckel. + + _Diplosphaera spinosa_, R. Hertwig, 1879, Organismus d. Radiol., p. 40, + Taf. v. fig. 2. + +Inner shell with regular, hexagonal meshes, five times as broad as the +bars; outer shell three times as broad, with simple triangular meshes. +Radial spines with three densely serrated edges, and with three rows of +serrated, simple, curved, lateral branches (three branches on each edge). +Differs from the preceding in the thicker bars and the elegantly +denticulated spines and branches. + +_Dimensions._--Diameter of the outer shell 0.66, inner 0.22. + +_Habitat._--Mediterranean (Messina), R. Hertwig. + + +6. _Leptosphaera stellata_, n. sp. + +Inner shell with regular, hexagonal meshes, six times as broad as the bars, +each bar crossed by a transverse tangential rod, so that each mesh +represents an elegant six-rayed star (as {246}in _Astrosphaera stellata_, +Pl. 19, fig. 5, but without radial by-spines); outer shell twice as broad, +with simple triangular meshes. Radial spines with serrated edges and three +rows of simple lateral branches (four branches on each edge). + +_Dimensions._--Diameter of the outer shell 0.44, inner 0.22. + +_Habitat._--Tropical Atlantic (Ascension Island), Station 343, surface. + + +7. _Leptosphaera reticulum_, n. sp. + +Inner shell with irregular, polygonal meshes and very thin thread-like +bars; outer shell four times as broad, also with irregular, polygonal +meshes, the sides of the triangular main meshes being connected by +irregular lateral ramules, forming an extremely delicate reticulum. + +_Dimensions._--Diameter of the outer shell 0.64, inner 0.16. + +_Habitat._--South Pacific, Station 291, surface. + + + +Genus 98. _Diplosphaera_,[133] Haeckel, 1860, Monatsber. d. k. preuss. +Akad. d. Wiss. Berlin, p. 804. + +_Definition._--#Astrosphaerida# with two extracapsular cortical shells, +connected by long, prismatic, radial spines; inner shell with thin radial +by-spines. + +The genus _Diplosphaera_ differs from its ancestral form _Leptosphaera_ in +the development of radial by-spines on the surface of the inner shell, the +outer shell being smooth. + + + +Subgenus 1. _Diplosphaerella_, Haeckel. + +_Definition._--Radial main spines simple, without lateral branches. + + +1. _Diplosphaera hexagonalis_, n. sp. (Pl. 19, fig. 3). + +Inner shell with regular, hexagonal meshes and very thin thread-like bars; +at each nodal-point one bristle-shaped by-spine; outer shell twice as +broad, with simple triangular meshes. Radial spines with three smooth +edges. (The radially striped central capsule, enclosed in the inner shell, +envelops a large central nucleus one-third its size, fig. 3.) + +_Dimensions._--Diameter of the outer shell 0.36, inner 0.18. + +_Habitat._--Central Pacific, Stations 265 to 274, surface. + + +2. _Diplosphaera ornata_, n. sp. + +Inner shell with regular, hexagonal meshes, four times as broad as the +bars; outer shell three times as broad, with simple triangular meshes. +Radial main spines as well as the bars of both {247}shells very elegantly +denticulated; radial by-spines (very numerous in the surface of the inner +shell) smooth. + +_Dimensions._--Diameter of the outer shell 0.7, inner 0.24. + +_Habitat._--Indian Ocean, Madagascar, surface, Rabbe. + + +3. _Diplosphaera dictyota_, n. sp. + +Inner shell with regular, hexagonal meshes, six times as broad as the bars; +at each nodal-point one radial by-spine; outer shell two and a half times +as broad, with very delicate square meshes, separated by thread-like bars +which arise from the sides of the triangular main meshes. Radial main +spines with three serrated edges. (Differs from the similar _Diplosphaera +gracilis_ in the simple main spines, with delicate dentition of the edges.) + +_Dimensions._--Diameter of the outer shell 0.5, inner 0.2. + +_Habitat._--North Atlantic, Canary Islands, surface. + + +4. _Diplosphaera polygonalis_, n. sp. + +Inner shell with irregular, polygonal meshes and very thin thread-like +bars, covered with very numerous bristle-shaped by-spines; outer shell +twice as broad, with simple triangular meshes. Radial main spines with +three smooth edges. + +_Dimensions._--Diameter of the outer shell 0.44, inner 0.22. + +_Habitat._--South Pacific, Station 288, surface. + + + +Subgenus 2. _Diplosphaeromma_, Haeckel. + +_Definition._--Radial main spines with three rows of lateral branches (one +row on each edge). + + +5. _Diplosphaera gracilis_, Haeckel. + + _Diplosphaera gracilis_, Haeckel, 1862, Monogr. d. Radiol., p. 354, Taf. + x. fig. 1. + +Inner shell with regular, hexagonal meshes and very thin bars; at each +nodal-point one simple bristle-shaped radial by-spine; outer shell twice as +broad, with very delicate square meshes, separated by thread-like bars +which arise from the sides of the triangular main meshes. Radial spines +with smooth edges and with three rows of simple curved lateral branches +(four to six branches on each edge). + +_Dimensions._--Diameter of the outer shell 0.54, inner 0.27. + +_Habitat._--Mediterranean (Messina). + + +6. _Diplosphaera denticulata_, n. sp. + +Inner shell with regular, hexagonal meshes, four times as broad as the +bars; at each nodal-point is a simple bristle-shaped by-spine; outer shell +three times as broad, with simple triangular meshes. {248}Radial spines +very strong, with dentated edges and with three rows of lateral branches +(six dentated curved branches on each edge). + +_Dimensions._--Diameter of the outer shell 0.4, inner 0.13. + +_Habitat._--North Atlantic, Azores, surface. + + +7. _Diplosphaera reticulata_, n. sp. + +Inner shell with regular, hexagonal meshes, five times as broad as the +bars, which are densely covered with very numerous, simple bristle-shaped +by-spines; outer shell four times as broad, with very numerous small +irregular polygonal meshes, forming a very delicate network, and filling +out the large triangular main meshes. Radial spines with three serrated +edges and three rows of short curved branches (four to five branches on +each edge). + +_Dimensions._--Diameter of the outer shell 0.6, inner 0.15. + +_Habitat._--North Atlantic, Gulf Stream, Faeroee Channel, surface, John +Murray. + + +8. _Diplosphaera triglochin_, n. sp. + +Inner shell with irregular, polygonal meshes and very thin thread-like +bars; outer shell three times as broad, with similar irregular polygonal +meshes, filling out the large triangular main meshes. Radial spines with +three serrated edges, each of which bears one single large lateral branch, +concavely curved towards the distal end. By-spines of the inner shell very +numerous. + +_Dimensions._--Diameter of the outer shell 0.5, inner 0.17. + +_Habitat._--Central Pacific, Station 264, surface. + + + +Genus 99. _Drymosphaera_,[134] Haeckel, 1881, Prodromus, p. 452. + +_Definition._--#Astrosphaerida# with two extracapsular cortical shells, +connected by long prismatic, radial spines; outer shell with thin radial +by-spines. + +The genus _Drymosphaera_ differs from its ancestral form _Leptosphaera_ in +the development of radial by-spines on the surface of the outer shell, the +inner shell being smooth. + + + +Subgenus 1. _Drymosphaerella_, Haeckel. + +_Definition._--Radial by-spines simple, not branched (main spines simple). + + +1. _Drymosphaera hexagonalis_, n. sp. + +Inner shell with regular, hexagonal meshes and very thin thread-like bars; +outer shell twice as broad, with simple triangular meshes and thin +thread-like bars, which bear very numerous, {249}bristle-shaped radial +by-spines. Radial main spines with three smooth edges. (Differs from the +first species of the other three genera of Diplosphaerida in the presence +of by-spines on the outer, and their absence on the inner shell.) + +_Dimensions._--Diameter of the outer shell 0.32, inner 0.16. + +_Habitat._--Central Pacific, Station 274, surface. + + +2. _Drymosphaera polygonalis_, n. sp. (Pl. 19, fig. 1). + + _Diplosphaera polygonalis_, Haeckel, 1879, Atlas. + +Inner shell with irregular, polygonal meshes and very thin thread-like +bars; outer shell one and a half times as broad, with simple triangular +meshes and thicker bars, which bear numerous bristle-shaped radial +by-spines (in the figure the majority of these are broken off). Radial main +spines with three smooth edges. (Similar to _Leptosphaera polygonalis_ and +_Diplosphaera polygonalis_, but differs from both in the presence of +by-spines on the outer, and their absence on the inner shell.) + +_Dimensions._--Diameter of the outer shell 0.33, inner 0.22. + +_Habitat._--North Pacific, Station 236 south of Japan, surface. + + + +Subgenus 2. _Drymosphaeromma_, Haeckel. + +_Definition._--Radial by-spines forked or branched (main spines simple). + + +3. _Drymosphaera furcata_, n. sp. + +Inner shell with irregular, polygonal meshes and thin bars, the former five +times as broad as the latter; outer shell two and a half times as broad, +with simple triangular meshes and smooth bars, bearing numerous long smooth +bristle-shaped by-spines, which in the distal half are forked. Radial main +spines with three smooth edges. + +_Dimensions._--Diameter of the outer shell 0.4, inner 0.16. + +_Habitat._--Indian Ocean, Ceylon, surface, Haeckel. + + +4. _Drymosphaera cladophora_, n. sp. + +Inner shell with irregular, polygonal meshes, three to six times as broad +as the smooth bars; outer shell twice as broad, with simple triangular +meshes and very thin smooth bars, bearing numerous curved, irregularly +branched, smooth by-spines. Radial main spines with three serrated edges. + +_Dimensions._--Diameter of the outer shell 0.4, inner 0.2. + +_Habitat._--Central Pacific, Station 276, surface. + + +5. _Drymosphaera dendrophora_, n. sp. (Pl. 20, figs. 1, 1_a_, 1_b_). + +Inner shell with irregular, polygonal meshes and very thin thread-like +bars; outer shell one and a half times as broad, with simple triangular +meshes and thicker bars, which bear a forest of {250}very numerous, +repeatedly dichotomous or irregularly branched, curved by-spines, longer +than the diameter of the outer shell. Radial main spines with three +dentated edges. All parts of the skeleton, the net bars as well as the +radial beams and spines, are very elegantly denticulated (fig. 1_b_). The +central capsule (fig. 1_a_) completely distends the inner shell and forces +out protuberances through all its pores; in its centre lies a nucleus +one-third its size. + +_Dimensions._--Diameter of the outer shell 0.25, inner 0.16. + +_Habitat._--Central Pacific, Station 271, surface. + + + +Genus 100. _Astrosphaera_,[135] n. gen. + +_Definition._--#Astrosphaerida# with two extracapsular cortical shells, +connected by long, prismatic, radial spines; inner and outer shell with +thin radial by-spines. + +The genus _Astrosphaera_ differs from its ancestral form, _Leptosphaera_, +in the development of radial by-spines on the surface of both shells. + + + +Subgenus 1. _Astrosphaerella_, Haeckel. + +_Definition._--Radial main spines simple without lateral branches. + + +1. _Astrosphaera hexagonalis_, n. sp. (Pl. 19, fig. 4). + +Inner shell with regular, hexagonal meshes and very thin bars, having a +bristle-shaped, short radial by-spine in each hexagon-corner; outer shell +twice as broad, with simple triangular meshes and thicker bars, bearing one +row of simple bristle-shaped, curved, radial by-spines. Radial main spines +with three smooth edges. + +_Dimensions._--Diameter of the outer shell 0.32, inner 0.16. + +_Habitat._--South Pacific (West Patagonia), Station 302, surface. + + +2. _Astrosphaera splendens_, n. sp. + +Inner shell with regular, hexagonal meshes, four times as broad as the +bars, and covered with numerous curved, long, bristle-shaped by-spines; +outer shell three times as broad, with simple triangular meshes and thin +bars, bearing a row of very long, curved, bristle-shaped by-spines. Radial +main spines with three dentated edges. All parts of the skeleton elegantly +denticulated, as in _Drymosphaera dendrophora_ (Pl. 20, fig. 1). + +_Dimensions._--Diameter of outer shell 0.7, inner 0.24. + +_Habitat._--Tropical Atlantic, Station 347, surface. + + + +{251}Subgenus 2. _Astrosphaeromma_. + +_Definition._--Radial main spines with three rows of lateral branches (one +row on each edge). + + +3. _Astrosphaera sideraea_, n. sp. + +Inner shell with regular, hexagonal meshes, six times as broad as the bars, +and covered with numerous short bristle-shaped by-spines; outer shell four +times as broad, with simple triangular meshes, and rows of long +bristle-shaped by-spines arising from the bars. Radial main spines with +three serrated edges and three rows of lateral branches (four branches on +each edge). + +_Dimensions._--Diameter of the outer shell 0.6, inner 0.15. + +_Habitat._--Central Pacific, Station 266, surface. + + +4. _Astrosphaera stellata_, n. sp. (Pl. 19, fig. 5). + + _Diplosphaera stellata_, Haeckel, 1881, Prodrom. et Atlas. + +Inner shell with regular, hexagonal, six-rayed meshes, each bar being +crossed by a transverse tangential rod, at each nodal-point a long +bristle-shaped by-spine; outer shell three times as broad, with simple +triangular meshes and denticulated thin bars, bearing a row of +bristle-shaped radial by-spines. Radial main spines in the proximal half +with three serrated edges, in the distal half with three rows of curved +lateral branches (five branches on each edge). + +_Dimensions._--Diameter of the outer shell 0.6, inner 0.2. + +_Habitat._--Central Pacific, Station 274, surface. + + + +Subfamily ACTINOMMIDA,[136] Haeckel, 1862, Monogr. d. Radiol., p. 440 +(_sensu emendato_). + +_Definition._--#Astrosphaerida# with three concentric, spherical, +lattice-shells, united by radial beams. + + + +Genus 101. _Actinomma_,[137] Haeckel, 1862, Monogr. d. Radiol., p. 440. + +_Definition._--#Astrosphaerida# with three concentric lattice-spheres and +numerous simple radial spines of one kind. + +The genus _Actinomma_ is here restricted to those #Sphaeroidea# which +combine the possession of three concentric lattice-shells with numerous +radial spines on the surface; the spines are all simple, being of one and +the same kind. Commonly two of the three shells are intracapsular medullary +shells, connected by radial beams (piercing {252}the central capsule) with +the outer, extracapsular, cortical shell. But in some species only one +medullary shell is enclosed in the central capsule, whilst both other +shells lie outside it. In such case the distance between these two cortical +shells is much smaller than their distance from the simple internal +medullary shell. These forms correspond more to aculeate _Rhodosphaerae_, +whilst the others resemble aculeate _Thecosphaerae_. + + + +Subgenus 1. _Actinommantha_, Haeckel. + +_Definition._--Pores of the cortical shell regular, of nearly equal size +and similar form; spines on the entire surface (commonly one spine at each +nodal-point). + + +1. _Actinomma hexagonium_, n. sp. + +Cortical shell, as well as both medullary shells, very thin walled, with +regular, hexagonal pores and thread-like bars between them. Pores of the +outer shell twice as broad as those of the middle, and three times as broad +as those of the inner shells. Radial proportion of the three spheres = +1 : 3 : 9; about twenty thin radial beams between them. At each nodal-point +of the surface arises one bristle-shaped radial spine, half as long as the +radius. + +_Dimensions._--Diameter of the outer shell 0.22, middle 0.07, inner 0.025; +meshes of the cortical shell 0.01; length of the spines 0.05. + +_Habitat._--Central Pacific, Stations 270 to 274, surface. + + +2. _Actinomma facetum_, n. sp. + +Cortical shell thick walled, with regular, circular, hexagonally framed +pores, three times as broad as the bars. Pores of both medullary shells +regular, circular. Radial proportion of the three spheres = 1 : 2 : 4; +about forty thin radial beams between them. At each nodal-point of the +surface arises one short, three-sided pyramidal, radial spine, about +one-third as long as the radius. + +_Dimensions._--Diameter of the outer shell 0.16, middle 0.08, inner 0.04; +cortical pores 0.012, bars 0.004; length of the spines 0.03, basal breadth +0.015. + +_Habitat._--North Pacific, Station 253, depth 3125 fathoms. + + +3. _Actinomma anthomma_, n. sp. + +Cortical shell thick walled, with regular, six-lobed pores, twice as broad +as the bars. At each nodal-point of the surface is one short conical radial +spine, as long as the diameter of the pores; one corresponding to each +lobe, and there is therefore around each pore a regular corona of six +spines, as in _Haliomma lirianthus_ (Pl. 28, fig. 1_b_). Both medullary +shells with simple, circular, regular pores. Radial proportion of the three +spheres = 1 : 2.5 : 7; radial beams between them only six, opposite in +pairs in the three dimensive axes. + +{253}_Dimensions._--Diameter of the outer shell 0.2, middle 0.075, inner +0.003; cortical pores 0.01, bars 0.005; length of the spines 0.01. + +_Habitat._--Central Pacific, Station 271, surface. + + +4. _Actinomma castanomma_, n. sp. + +Cortical shell as well as both medullary shells thick walled, with regular, +circular pores, twice as broad as the bars; between them at each +nodal-point one bristle-shaped radial spine, one-third as long as the +radius, with conical base. Radial proportion of the three spheres = +2 : 3 : 8; only six radial beams between them (opposed in pairs in the +three dimensive axes). + +_Dimensions._--Diameter of the outer shell 0.15, middle 0.06, inner 0.04; +cortical pores 0.008, bars 0.004; length of the spines 0.025. + +_Habitat._--South Atlantic, Station 333, surface. + + +5. _Actinomma entactinia_, Stoehr. + + _Actinomma entactinia_, Stoehr, 1880, Palaeontogr., vol. xxvi. p. 93, + Taf. ii. fig. 12. + +Cortical shell as well as both medullary shells thick walled, with regular, +circular pores, of the same breadth as the bars. Radial proportion of the +three spheres = 1 : 3 : 8; radial beams between them very numerous (thirty +to fifty or more?). Entire surface covered with short thick conical +spines, only one-fifth as long as the radius. + +_Dimensions._--Diameter of the outer shell 0.16, middle 0.06, inner 0.02; +cortical pores and bars 0.007; length of the spines 0.015. + +_Habitat._--Fossil in the Tertiary rocks of Sicily, Grotte, Caltanisetta. + + + +Subgenus 2. _Actinommetta_, Haeckel. + +_Definition._--Pores of the outer shell regular, of nearly equal size and +similar form; spines not over the entire surface, but scattered at +intervals (their number smaller than that of the nodal-points). + + +6. _Actinomma japonicum_, n. sp. + +Cortical shell thick walled, with regular, circular, hexagonally framed +pores, three times as broad as the bars. Both medullary shells with simple, +circular, regular pores, of the same breadth as the bars. Radial proportion +of the three spheres = 2 : 5 : 9; radial beams between them twenty, +prolonged outside into twenty symmetrically disposed, three-sided pyramidal +spines, as long as the radius. + +_Dimensions._--Diameter of the outer shell 0.18, middle 0.1, inner 0.04; +cortical pores 0.01, bars 0.003; length of the spines 0.1, basal breadth +0.012. + +_Habitat._--North Pacific, Station 240, east of Japan, surface. + + +{254}7. _Actinomma denticulatum_, n. sp. (Pl. 29, fig. 3). + +Cortical shell thick walled, with regular, circular, double-edged pores, +twice as broad as the bars. Forty to fifty radial spines, three-sided +pyramidal, half as long as the radius, with three elegantly denticulated +edges. Radial proportion of the three spheres = 1 : 2 : 5. (Differs from +_Haliomma denticulatum_ only in the double medullary shell and larger +size.) + +_Dimensions._--Diameter of the outer shell 0.14, middle 0.06, inner 0.03; +cortical pores 0.01, bars 0.005; length of the spines 0.04, basal breadth +0.01. + +_Habitat._--Central Pacific, Station 271, depth 2425 fathoms. + + +8. _Actinomma trinacrium_, Haeckel. + + _Actinomma trinacrium_, Haeckel, 1862, Monogr. d. Radiol., p. 441, Taf. + xxiv. figs. 6-8. + + _Haliomma trinacrium_, Haeckel, 1860, Monatsber. d. k. preuss. Akad. d. + Wiss. Berlin, p. 815. + +Cortical shell as well as both medullary shells thin walled, with +subregular, circular pores, twice as broad as the bars. Radial proportion +of the three spheres = 1 : 3 : 9; radial beams between them twenty, +prolonged outside into strong, three-sided pyramidal spines, as long as the +radius; between them, on the surface, numerous similar spines. Sometimes +the latter remain smaller, the pores more irregular, and then this species +corresponds to _Echinomma trinacrium_. + +_Dimensions._--Diameter of the outer shell 0.09, middle 0.03, inner 0.01; +cortical pores 0.008, bars 0.004; length of the spines 0.04, basal breadth +0.01. + +_Habitat._--Mediterranean (Messina, Corfu, Haeckel), surface. + + +9. _Actinomma pachyderma_, n. sp. (Pl. 29, figs. 4, 5). + +Cortical shell very thick walled, with regular, circular, double-edged +pores, twice as broad as the bars. Both medullary shells with simple, +small, circular pores, of the same breadth as the bars. Radial proportion +of the three spheres = 1 : 2 : 4; radial spines about twenty, conical, +shorter than the radius, prolonged inside into twenty very thin connecting +beams (fig. 4). + +_Dimensions._--Diameter of the outer shell 0.08, middle 0.04, inner 0.02; +cortical pores 0.01; bars 0.005; length of the spines 0.03, basal breadth +0.01. + +_Habitat._--South Pacific, Station 297, depth 1775 fathoms. + + + +Subgenus 3. _Actinommilla_, Haeckel. + +_Definition._--Pores of the cortical shell irregular, of different size and +form; spines over the entire surface (commonly one spine at each +nodal-point). + + +10. _Actinomma spinigerum_, Stoehr. + + _Actinomma spinigerum_, Stoehr, 1880, Palaeontogr., vol. xxvi. p. 92, + Taf. ii. fig. 10. + +Cortical shell thick walled, with irregular, roundish, or subcircular +pores, twice to four times as broad as the bars. Radial proportion of the +three spheres = 1 : 3 : 8; between them eight (?) {255}connecting radial +beams. Entire surface densely covered with small conical spines, not larger +than the pores. + +_Dimensions._--Diameter of the outer shell 0.17, middle 0.07, inner 0.023; +cortical pores 0.006 to 0.012, bars 0.003; length of the spines 0.01. + +_Habitat._--Fossil in Tertiary rocks of Sicily, Grotte, Stoehr. + + +11. _Actinomma hirsutum_, n. sp. + +Cortical shell thick walled, with irregular, roundish pores, about the same +breadth as the bars. Radial proportion of the three spheres = 1 : 2 : 8; +between them numerous (twenty to thirty or more) cylindrical connecting +beams. Entire surface densely covered with innumerable small bristle-shaped +spines, as long as the diameter of the inner shell. + +_Dimensions._--Diameter of the outer shell 0.25, middle 0.06, inner 0.03; +cortical pores and bars 0.004 to 0.008; length of the spines 0.03. + +_Habitat._--Central Pacific, Station 265, depth 2900 fathoms. + + + +Subgenus 4. _Actinommura_, Haeckel. + +_Definition._--Pores of the cortical shell irregular, of different size and +form; spines not over the entire surface, but scattered at intervals (their +number smaller than that of the nodal-points). + + +12. _Actinomma capillaceum_, n. sp. (Pl. 29, fig. 6). + +Cortical shell very thin walled, with irregular, polygonal meshes (sixteen +to eighteen on the radius), three to six times as broad as the bars. Both +medullary shells with smaller pores of the same structure. Radial +proportion of the three spheres = 1 : 2.5 : 7; radial connecting beams +between them very thin and numerous (one hundred and twenty to one hundred +and fifty or more), each prolonged outside into a short three-sided +pyramidal spine, as long as the radius of the inner shell. (Similar to +_Haliomma capillaceum_.) + +_Dimensions._--Diameter of the outer shell 0.27, middle 0.1, inner 0.04; +cortical pores 0.01 to 0.02, bars 0.003; length of the spines 0.02, basal +breadth 0.005. + +_Habitat._--Central Pacific, Stations 266 to 274, surface. + + +13. _Actinomma arcadophorum_, n. sp. (Pl. 29, figs. 7, 8). + +Cortical shell very thin walled, with irregular, polygonal meshes, ten to +twenty times as broad as the bars; twelve to sixteen on the radius. Both +medullary shells with similar delicate network. Radial proportion of the +three spheres = 1 : 2 : 6; numerous thin radial beams (forty to eighty or +more) connect both medullary shells and alternate with other beams, which +arise from arcade-shaped {256}protuberances of the outer medullary shell, +and connect it with the cortical shell. Outer prolongations of these form +the bristle-shaped spines of the surface. + +_Dimensions._--Diameter of the outer shell 0.22, middle 0.09, inner 0.04; +cortical pores 0.01 to 0.02, bars 0.001 to 0.002; length of the radial +spines 0.2. + +_Habitat._--Central Pacific, Station 266, surface. + + +14. _Actinomma schwageri_, Stoehr. + + _Actinomma schwageri_, Stoehr, 1880, Palaeontogr., vol. xxvi. p. 92, Taf. + ii. fig. 9_a_, _b_. + +Cortical shell thick walled, with irregular, large, polygonal meshes, five +to twelve times as broad as the bars; six to eight on the radius. Both +medullary shells with very small, circular, regular pores. Radial +proportion of the three spheres = 1 : 2 : 9; connecting radial beams +between them nine, prolonged outside into nine short stout, three-sided +pyramidal spines, as long as the diameter of the inner shell. + +_Dimensions._--Diameter of the outer shell 0.17, middle 0.04, inner 0.02; +cortical pores 0.01 to 0.03, bars 0.006 and less; length of the spines +0.02, basal breadth 0.01. + +_Habitat._--Fossil in Tertiary rocks of Sicily, Grotte, Stoehr. + + +15. _Actinomma dodecomma_, n. sp. + +Cortical shell thin walled, with irregular, roundish pores, three to six +times as broad as the bars. Both medullary shells with regular, circular +pores, twice as broad as the bars. Radial proportion of the three shells = +1 : 2.5 : 7; connecting radial beams between them twelve, regularly +disposed, prolonged outside into twelve strong, three-sided pyramidal +spines, as long as the radius. + +_Dimensions._--Diameter of the outer shell 0.14, middle 0.05, inner 0.02; +cortical pores 0.008 to 0.018, bars 0.003; length of the spines 0.08, +breadth 0.02. + +_Habitat._--Tropical Atlantic, Station 348, depth 2450 fathoms. + + +16. _Actinomma pachycapsa_, n. sp. + +Cortical shell very thick walled, with irregular, roundish pores, twice to +four times as broad as the bars; twelve to sixteen on the radius. Radial +proportion of the three spheres = 1 : 3 : 12. Both medullary shells of +similar irregular structure, connected with the cortical shell by twelve +regularly disposed radial beams, which are prolonged outside into twelve +short stout conical spines, as long as the diameter of the middle shell. + +_Dimensions._--Diameter of the outer shell 0.25, middle 0.06, inner 0.02; +cortical pores 0.006 to 0.012, bars 0.003; length of the spines 0.05, +breadth 0.02. + +_Habitat._--Central Pacific, Station 268, depth 2900 fathoms. + + +17. _Actinomma giganteum_, n. sp. + +Cortical shell thick walled, little larger than the outer medullary shell, +whilst the inner is only one-tenth as large. Pores of all three shells +irregular, roundish, or subcircular, twice to three times {257}as broad as +the bars, on an average twice as large in the outer and middle as in the +inner shell. Sixty to eighty short conical radial spines on the surface, +about as long as the diameter of the inner shell, and one-fourth as broad +at the base. Radial proportion of the three spheres = 1 : 9 : 10. + +_Dimensions._--Diameter of the outer shell 0.4 to 0.5, middle 0.35 to 0.45, +inner 0.05 to 0.06. + +_Habitat._--Fossil in Barbados. + + + +Genus 102. _Echinomma_,[138] Haeckel, 1881, Prodromus, p. 453. + +_Definition._--#Astrosphaerida# with three concentric lattice-spheres and +numerous simple radial spines of two different kinds; larger main spines +and smaller by-spines. + +The genus _Echinomma_, differs from its ancestral form, _Actinomma_, in the +differentiation of the radial spines. Whilst a large number of small +by-spines cover the entire surface, a smaller number of large main spines +are scattered over it, or limited to certain regularly distributed points. +It represents _Heliosoma_ among the Haliommida. + + + +Subgenus 1. _Echinommetta_, Haeckel. + +_Definition._--Pores of the cortical shell regular, of nearly equal size +and similar form. + + +1. _Echinomma echinidium_, n. sp. + +Cortical shell thin walled, with regular, hexagonal pores, four times as +broad as the bars; ten to twelve on the radius. Both medullary shells with +regular, circular pores, twice as broad as the bars. Radial proportion of +the three spheres = 1 : 2 : 5. Surface covered with short bristle-shaped +by-spines (one in every hexagon-corner); twenty main spines regularly +disposed, three-sided pyramidal, as long as the diameter of the inner +shell. + +_Dimensions._--Diameter of the outer shell 0.1, middle 0.045, inner 0.02; +cortical pores 0.008, bars 0.002; length of the main spines 0.02, breadth +0.01. + +_Habitat._--South Pacific, Station 295, surface. + + +2. _Echinomma cidaris_, n. sp. + +Cortical shell thin walled, with regular, circular, hexagonally framed +pores, twice as broad as the bars; six to eight on the radius. Both +medullary shells with simple, circular pores. Radial proportion of the +three spheres = 1 : 2 : 6. Surface covered with short bristle-shaped +by-spines, half as long as the forty to fifty main spines, which are +three-sided pyramidal, and reach the radius of the shell. + +_Dimensions._--Diameter of the outer shell 0.18, middle 0.06, inner 0.03; +cortical pores 0.01, bars 0.005; length of the main spines 0.08, basal +breadth 0.015. + +_Habitat._--Central Pacific, Station 272, surface. + + +{258}3. _Echinomma aculeatum_, Haeckel. + + _Actinomma aculeatum_, Stoehr, 1880 Palaeontogr., vol. xxvi. p. 92, Taf. + ii. fig. 11. + +Cortical shell thick walled with regular circular pores, of the same +breadth as the bars; eight to ten on the radius. Radial proportion of the +three spheres = 1 : 2 : 8. Surface covered with short conical by-spines +about twenty strong main spines, three-sided pyramidal, one-third as long +as the shell diameter. + +_Dimensions._--Diameter of the outer shell 0.16, middle 0.04, inner 0.02; +cortical pores and bars 0.003; length of the main spines 0.05, basal +breadth 0.013. + +_Habitat._--Fossil in the Tertiary rocks of Sicily and Barbados; living in +the Atlantic, Station 332, depth 2200 fathoms. + + +4. _Echinomma diadema_, n. sp. + +Cortical shell thick walled with regular circular pores, twice as broad as +the bars; sixteen to eighteen on the radius. Radial proportion of the three +spheres = 1 : 3 : 11. Surface covered with short bristle-shaped by-spines +one third as long as the twelve stout conical main spines, which reach in +length the radius, and lie opposite in pairs in six axes. + +_Dimensions._--Diameter of the outer shell 0.22, middle 0.06, inner 0.02; +cortical pores 0.006, bars 0.003 length of the main spines 0.12, basal +breadth 0.02. + +_Habitat._--Central Pacific, Station 268, depth 2900 fathoms. + + + +Subgenus 2. _Echinommura_, Haeckel. + +_Definition._--Pores of the cortical shell irregular, of different size or +form. + + +5. _Echinomma sphaerechinus_, n. sp. (Pl. 29, fig. 2). + + _Actinomma sphaerechinus_, Haeckel, 1879, Atlas (pl. xxix. fig. 2). + +Cortical shell thin walled, with irregular, roundish pores, twice to five +times as broad as the bars; five to seven on the radius. Both medullary +shells with regular, circular pores, twice as broad as the bars. Radial +proportion of the three spheres = 1 : 2 : 4. Surface covered with thirty to +fifty pyramidal main spines, as long as the diameter of the inner shell, +and with numerous small conical by-spines of half the length. + +_Dimensions._--Diameter of the outer shell 0.11, middle 0.05, inner 0.025; +cortical pores 0.01 to 0.02, bars 0.004; length of the main spines 0.03, +basal breadth 0.005. + +_Habitat._--North Atlantic, Station 353, surface. + + +6. _Echinomma trinacrium_, Haeckel. + + _Actinomma trinacrium_, Haeckel, 1862, Monogr. d. Radiol., p. 441, Taf. + xxiv. figs. 6-8. + +Cortical shell thin walled, with irregular, roundish pores, twice to three +times as broad as the bars. Both medullary shells with regular, circular +pores. Radial proportion of the three spheres {259}= 1 : 3 : 9. On the +surface about twenty three-sided pyramidal main spines, as long as the +radius, and numerous (forty to sixty) by-spines of half the length. +(Compare with this species _Actinomma trinacrium_, with which it is +connected by transitional forms.) + +_Dimensions._--Diameter of the outer shell 0.09, middle 0.03, inner 0.01; +cortical pores 0.008 to 0.012, bars 0.004; length of the spines 0.02 to +0.05, basal breadth 0.01. + +_Habitat._--Mediterranean (Messina). + + +7. _Echinomma toxopneustes_, n. sp. (Pl. 29, fig. 1). + +Cortical shell thin walled, with large, irregular roundish, polygonally +framed pores, twice to four times as broad as the crested bars. Both +medullary shells of similar structure. Radial proportion of the three +spheres = 1 : 2.5 : 6. Numerous (thirty to fifty or more) thin radial beams +connecting them, prolonged outside into strong three-sided pyramidal +spines, shorter than the radius; each of the three wings with two teeth. +Between these, numerous smaller angular by-spines of one-quarter to +one-half the length. + +_Dimensions._--Diameter of the outer shell 0.12, middle 0.05, inner 0.02; +cortical pores 0.01 to 0.03, bars 0.008; length of the main spines 0.05, +basal breadth 0.01. + +_Habitat._--South-east Pacific (South of Juan Fernandez), Station 300, +surface. + + + +Genus 103. _Pityomma_,[139] Haeckel, 1881, Prodromus, p. 453. + +_Definition._--#Astrosphaerida# with three concentric lattice-shells and +numerous branched radial spines. + +The genus _Pityomma_ differs from its ancestral form, _Actinomma_, in the +ramification of its radial spines, and exhibits therefore the same relation +to it that _Elatomma_, among the Haliommida, bears to _Haliomma_. + + +1. _Pityomma scoparium_, n. sp. + +Cortical shell thick walled, connected with both concentric medullary +shells by twenty thin radial beams, which are prolonged outside into twenty +large cylindrical radial spines; these are somewhat shorter than the shell +radius, simple in the proximal inner half, irregularly branched in the +outer half. All three spheres with regular, circular pores, twice to three +times as broad as the bars; radial proportion = 1 : 2 : 6. (Similar to +_Cladococcus scoparius_, Pl. 27, fig. 2, and _Elatomma scoparium_, but +differs from both in the double medullary shell.) + +_Dimensions._--Diameter of the outer shell 0.15, middle 0.05, inner 0.025; +length of the spines 0.1. + +_Habitat._--Central Pacific, Station 273, surface. + + +{260}2. _Pityomma piniferum_, n. sp. + +Cortical shell thin walled, with irregular, roundish pores, connected with +both medullary shells by twenty stout radial beams, which are prolonged +outside into twenty large three-sided prismatic spines. These are longer +than the shell diameter and have three dentate edges, being branched like a +pine tree (with four to six ramified branches on each edge, decreasing in +size towards the distal end); similar to those of _Cladococcus abietinus_ +(Pl. 27, fig. 3). Radial proportion of the three spheres = 1 : 2 : 8. Both +medullary shells with regular, circular pores, twice as broad as the bars. + +_Dimensions._--Diameter of the outer shell 0.2, middle 0.05, inner 0.025; +length of the spines 0.25. + +_Habitat._--South Pacific, Station 299 (Juan Fernandez), surface. + + +3. _Pityomma drymodes_, n. sp. (Pl. 29, fig. 9). + +Cortical shell thin walled, connected with both medullary shells by very +numerous (one hundred to two hundred or more) very thin radial beams, which +are prolonged outside into thin branched radial spines, scarcely half as +long as the shell radius, each spine bearing six to nine simple branches. +Outer and middle shell uneven, with hill-shaped protuberances and valleys +between them; the connecting radial beams, which arise from the top of the +protuberances of the middle shell, are inserted into the deepest part of +the valleys of the outer shell. Radial proportion of the three spheres = +1 : 3 : 8. Outer medullary shell with small, irregular, roundish, or +polygonal pores, not much broader than the bars; innermost shell with +polygonal pores and very thin bars. + +_Dimensions._--Diameter of the outer shell 0.28, middle 0.1, inner 0.033; +length of the spines 0.07, breadth 0.004. + +_Habitat._--Central Pacific, Station 271, surface. + + + +Subfamily CROMYOMMIDA,[140] Haeckel, 1881, Prodromus, pp. 449, 453. + +_Definition._--#Astrosphaerida# with four concentric spherical +lattice-shells. + + + +Genus 104. _Cromyomma_,[141] Haeckel, 1881, Prodromus, p. 454. + +_Definition._--#Astrosphaerida# with four concentric lattice-spheres and +numerous simple radial spines of one kind. + +The genus _Cromyomma_ is the common ancestral form of the Cromyommida, or +of those Astrosphaerida in which the shell is composed of four concentric +spheres, connected by radial beams. Usually two of these are intracapsular +or medullary {261}shells, two extracapsular or cortical shells; the +distance between the former and the latter is greater than the distance +between either the two inner or the two outer shells. In some cases, +however (_e.g._, _Cromyomma zonaster_), the distance between all four +shells is equal. + + + +Subgenus 1. _Cromyommetta_, Haeckel. + +_Definition._--Pores of the outer cortical shell regular, of nearly equal +size and similar form. + + +1. _Cromyomma villosum_, n. sp. (Pl. 30, fig. 2). + +Radial proportion of the four spheres = 1 : 2 : 4 : 5. Outer cortical shell +thick walled, densely covered with innumerable bristle-shaped radial +spines, half as long as the radius. Pores regular, circular, double-edged, +of the same breadth as the bars; ten to twelve on the radius. The thick +outer shell is so dark, that the outlines only of the other three shells +can be seen. + +_Dimensions._--Diameter of the four shells--(A) outer cortical shell 0.2, +(B) inner cortical shell 0.16, (C) outer medullary shell 0.08, (D) inner +medullary shell 0.04; pores and bars of the outer shell 0.008; length of +the spines 0.04. + +_Habitat._--Central Pacific, Station 267, depth 2700 fathoms. + + +2. _Cromyomma zonaster_, Haeckel. + + _Acanthosphaera zonaster_, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. + Berlin, p. 285, Taf. ii. fig. 2. + +Radial proportion of the four spheres = 2 : 3 : 4 : 5. Outer cortical shell +thick walled, densely covered with numerous bristle-shaped radial spines, +as long as the radius. Pores regular, circular, twice as broad as the bars; +eight to ten on the radius. The thick outer shell is so dark, that the +outlines only of the other three shells can be seen. + +_Dimensions._--Diameter of the four shells--(A) 0.15, (B) 0.12, (C) 0.09, +(D) 0.06; pores of the outer shell 0.01, bars 0.005; length of the spines +0.08. + +_Habitat._--Arctic Ocean, Greenland (depth 1000 fathoms), "Alert" +Expedition. + + +3. _Cromyomma perplexum_, Stoehr. + + _Cromyomma perplexum_, Stoehr, 1880, Palaeontogr., vol. xxvi. p. 95, Taf. + iii. fig. 5. + +Radial proportion of the four spheres = 1 : 2 : 3 : 4. Outer cortical shell +thick walled, densely covered with short conical spines, as long as the +diameter of the pores. These are regular, circular, three times as broad as +the bars; six to eight on the radius. The thick outer shell is so dark, +that the outlines only of the three other shells can be seen. + +_Dimensions._--Diameter of the four shells--(A) 0.17, (B) 0.13, (C) 0.087, +(D) 0.043; pores of the outer shell 0.015, bars 0.005; length of the spines +0.02. + +_Habitat._--Fossil in the Tertiary rocks of Sicily (Grotte) Stoehr. + + + +{262}Subgenus 2. _Cromyommura_, Haeckel. + +_Definition._--Pores of the outer cortical shell irregular, of different +size and form. + + +4. _Cromyomma perspicuum_, n. sp. (Pl. 30, fig. 8). + + _Cromyosphaera perspicua_, Haeckel, 1879, Atlas (pl. xxx. fig. 8). + +Radial proportion of the four shells = 1 : 2.5 : 6 : 9. Outer cortical +shell very thin walled, with thread-like bars, and irregular, polygonal +pores; inner cortical shell with similar pores, but with thicker bars. Both +medullary shells with regular, circular pores (the outer three times as +broad as the inner). Numerous thin radial beams connect the latter with the +former; other very thin and numerous beams connect the two cortical shells, +and are prolonged outside into short bristle-shaped spines (often longer +than in the figure). + +_Dimensions._--Diameter of the four shells--(A) 0.18, (B) 0.12, (C) 0.05, +(D) 0.02; pores of the outer shell 0.01 to 0.02; length of the spines 0.01 +to 0.03. + +_Habitat._--Central Pacific, Station 274, surface. + + +5. _Cromyomma quadruplex_, Haeckel. + + _Cromyomma quadruplex_, Haeckel, 1862, Monogr. d. Radiol., p. 446. + + _Haliomma quadruplex_, Ehrenberg, 1854, Monatsber. d. k. preuss. Akad. d. + Wiss. Berlin, p. 243. + +Radial proportion of the four spheres = 1 : 3 : 7 : 10. Outer cortical +shell thin walled, irregularly covered with numerous angular spines, as +long as the radius. Pores of all four shells irregular, roundish, +increasing in size from the first to the fourth. + +_Dimensions._--Diameter of the four shells--(A) 0.15, (B) 0.1, (C) 0.045, +(D) 0.015; pores of the outer shell 0.01 to 0.02; length of the spines +0.07. + +_Habitat._--North Atlantic, Station 353, depth 2965 fathoms. + + +6. _Cromyomma macroporum_, Stoehr. + + _Cromyomma macroporum_, Stoehr, 1880, Palaeontogr., vol. xxvi. p. 95, + Taf. iii. fig. 4. + +Radial proportion of the four spheres = 1 : 3 : 6 : 9. Outer cortical shell +thick walled, densely covered with short conical spines, as long as the +diameter of the pores; the latter are irregular, roundish, or polygonal, +larger and smaller alternating. + +_Dimensions._--Diameter of the four shells--(A) 0.1, (B) 0.066, (C) 0.033, +(D) 0.011; pores of the outer shell 0.033 to 0.016, bars 0.003; length of +the spines 0.01. + +_Habitat._--Fossil in the Tertiary rocks of Sicily, Grotte, Stoehr. + + +7. _Cromyomma circumtextum_, n. sp. (Pl. 30, fig. 4). + +Radial proportion of the four spheres = 1 : 2 : 5 : 7. Outer cortical +shell very delicate and thin walled, with thread-like bars and large, +irregular, polygonal meshes (larger than the innermost shell); {263}inner +cortical shell also with irregular, polygonal pores, three to nine times as +broad as the thick bars. Both medullary shells with subregular, circular +pores (the outer three times as broad as the inner). Radial spines twelve +to twenty, three-sided prismatic, stout, piercing the three outer shells, +inserted on the innermost; their outer part pyramidal, half as long as the +radius. + +_Dimensions._--Diameter of the four shells--(A) 0.22, (B) 0.15, (C) 0.07, +(D) 0.03; meshes of the outer shell 0.02 to 0.04; length of the outer +spines 0.05. + +_Habitat._--Central Pacific, Station 266, depth 2750 fathoms. + + +8. _Cromyomma mucronatum_, n. sp. (Pl. 30, figs. 5, 5_a_). + +Radial proportion of the three spheres = 1 : 2 : 3 : 6. Outer cortical +shell thin walled, with large, irregular, roundish pores and crested +three-sided bars; inner cortical shell with regular, circular, hexagonally +formed pores (four times as broad as the bars). Both medullary shells with +simple, small, regular, circular pores (fig. 5_a_). Twelve radial spines +three-sided prismatic, dagger-shaped, with three teeth, as long as the +diameter of the innermost shell. + +_Dimensions._--Diameter of the four shells--(A) 0.24, (B) 0.12, (C) 0.08, +(D) 0.04; meshes of the outer shell 0.02 to 0.04; length of the spines +0.04. + +_Habitat._--Central Pacific, Station 274, depth 2750 fathoms. + + + +Genus 105. _Cromyechinus_,[142] Haeckel, 1881, Prodromus, p. 454. + +_Definition._--#Astrosphaerida# with four concentric lattice-spheres and +numerous simple spines of two different kinds; larger main spines and +smaller by-spines. + +The genus _Cromyechinus_ differs from _Cromyomma_ in the same way as +_Echinomma_ from _Actinomma_; the radial spines being differentiated into +two different kinds; a larger number of small by-spines, and a smaller +number of large main spines. + + +1. _Cromyechinus icosacanthus_, n. sp. (Pl. 30, fig. 1). + +Radial proportion of the three spheres = 1 : 2 : 6 : 8. Outer cortical +shell very delicate, with very small, regular, circular pores, covered with +very numerous bristle-shaped by-spines, half as long as the radius; inner +cortical shell with very large, irregular, polygonal pores, three to eight +times as broad as the bars. Both medullary shells with regular, circular +pores, connected with the former by twenty regularly disposed, very thin +bars; these are prolonged outside into twenty very stout, three-sided +prismatic main spines, as long as the radius, which arise from the inner +cortical shell, and at the distal end are cuspidate. + +_Dimensions._--Diameter of the four shells--(A) 0.16, (B) 0.13, (C) 0.04, +(D) 0.02; pores of the outer cortical shell 0.003, of the inner 0.03, bars +0.003; length of the spines 0.08. + +_Habitat._--Central Pacific, Station 271, depth 2425 fathoms. + + +{264}2. _Cromyechinus dodecacanthus_, n. sp. (Pl. 30, figs. 3, 3_a_). + +Radial proportion of the four spheres = 1 : 3 : 10 : 12. Outer cortical +shell very delicate, with very small, regular, circular pores, covered with +numerous short bristle-shaped by-spines, scarcely one-fourth as long as the +radius; inner cortical shell with very large, irregular, polygonal pores, +twice to six times as broad as the bars. Both medullary shells with very +small, regular, circular pores, connected with the former by twelve +regularly disposed, thin radial beams; these are prolonged outside into +twelve strong, three-sided pyramidal main spines, one-third as long as the +shell diameter. (Differs from the foregoing only in the number and form of +the radial spines.) + +_Dimensions._--Diameter of the four shells--(A) 0.12, (B) 0.1, (C) 0.03, +(D) 0.01; pores of the outer cortical shell 0.002, of the inner 0.02, bars +0.002; length of the spines 0.04, basal breadth 0.01. + +_Habitat._--South Atlantic, Station 325, surface. + + +3. _Cromyechinus polyacanthus_, n. sp. + +Radial proportion of the four spheres = 1 : 2 : 8 : 10. Outer cortical +shell of the same structure as the inner, with irregular, roundish pores, +twice to six times as broad as the bars. Both medullary shells with small, +regular, circular pores, twice as broad as the bars. Connecting radial +beams forty to sixty, thin, cylindrical, prolonged outside into forty to +sixty strong conical main spines, about as long as the radius. Between +these, numerous thin bristle-shaped by-spines, nearly of the same length. + +_Dimensions._--Diameter of the four shells--(A) 0.25, (B) 0.2, (C) 0.05, +(D) 0.025; pores of both cortical shells 0.01 to 0.03; length of the spines +0.12. + +_Habitat._--North Pacific, Station 237, surface. + + + +Genus 106. _Cromyodrymus_,[143] Haeckel, 1881, Prodromus, p. 454. + +_Definition._--#Astrosphaerida# with four concentric lattice-spheres and +numerous branched radial spines. + +The genus _Cromyodrymus_ differs from its ancestral form, _Cromyomma_, in +the ramification of the radial spines, and exhibits therefore the same +relation to it that _Pityomma_ among the Actinommida bears to _Actinomma_. + + +1. _Cromyodrymus quadricuspis_, n. sp. (Pl. 30, figs. 7, 7_a_). + +Radial proportion of the four shells = 1 : 3 : 6 : 12. All four shells with +regular, circular pores, about twice as broad as the bars. Radial +proportion of the pores in the four shells = 2 : 4 : 2 : 1. Radial spines +fifty to sixty, three-sided prismatic, half as long as the radius, with +three recurved teeth, each spine in this way bearing four points. + +{265}_Dimensions._--Diameter of the four shells--(A) 0.16, (B) 0.08, (C) +0.04, (D) 0.013; length of the spines 0.03 to 0.04, breadth 0.007. + +_Habitat._--Central Pacific, Station 272, depth 2600 fathoms. + + +2. _Cromyodrymus abietinus_, n. sp. (Pl. 30, fig. 6). + +Radial proportion of the four shells = 1 : 2 : 5 : 11. All four shells with +irregular, roundish pores, twice to four times as broad as the bars. Radial +proportion of the pores in the four shells = 9 : 3 : 2 : 1. Radial spines +eighty to one hundred and twenty, about as long as the radius, branched +like a pine tree, with six to twelve ramified branches. + +_Dimensions._--Diameter of the four shells--(A) 0.22, (B) 0.1, (C) 0.04, +(D) 0.02; length of the spines 0.12, breadth 0.006. + +_Habitat._--South-east Pacific (Juan Fernandez), Station 299, surface. + + + +Subfamily CARYOMMIDA,[144] Haeckel. + +_Arachnosphaerida_, Haeckel, 1862, Monogr. d. Radiol., p. 354; Prodromus, +1881, p. 454. + +_Definition._--#Astrosphaerida# with five or more concentric spherical +lattice-shells. + + + +Genus 107. _Caryomma_,[145] n. gen. + +_Definition._--#Arachnosphaerida# with five to six or more concentric +spherical lattice-shells; two inner (intracapsular) medullary and three or +more outer (extracapsular) cortical shells, composed of ordinary +lattice-work; distance between the former and the latter greater than +between any other two shells. + +The genus _Caryomma_ may be regarded as a _Cromyomma_, in which the number +of the cortical shells is increased to three, four, or more. These lie +outside the central capsule, whilst two medullary shells lie within it, and +are connected with the former by numerous radial spines piercing the wall +of the capsule. The ordinary lattice-work is not arachnoidal, as in the +three following genera. + + +1. _Caryomma regulare_, n. sp. + +Radial proportion of the five shells = 1 : 2 : 6 : 8 : 10. All five shells +with regular, circular pores, twice to three times as broad as the bars, +and gradually increasing in size from the innermost to the outermost shell. +Radial beams connecting them twenty, prolonged on the surface into twenty +stout, three-sided pyramidal, radial spines, half as long as the radius, +regularly disposed. + +_Dimensions._--Diameter of the five shells--(A) 0.25, (B) 0.2, (C) 0.15, +(D) 0.05, (E) 0.025. + +_Habitat._--Central Pacific, Station 268, depth 2900 fathoms. + + +{266}2. _Caryomma irregulare_, n. sp. + +Radial proportion of the six shells = 1 : 2.5 : 8 : 10.5 : 13 : 15. Both +inner (medullary) shells with regular, circular pores, the other four +(cortical) shells with irregular, roundish pores, gradually increasing in +size from the innermost to the outermost shell. Radial spines sixty to +eighty, pyramidal, irregularly disposed. + +_Dimensions._--Diameter of the six shells--(A) 0.3, (B) 0.26, (C) 0.21, (D) +0.16, (E) 0.05, (F) 0.02. + +_Habitat._--Central Pacific, Station 265, depth 2900 fathoms. + + + +Genus 108. _Arachnopila_,[146] n. gen. + +_Definition._--#Astrosphaerida# with five to ten or more cortical, +concentric, polyhedral, or spherical lattice-shells, composed of a very +thin cobweb-like network; innermost shell with hexagonal (regular) or +polygonal (irregular) meshes; other shells with simple triangular meshes, +without diagonal threads between them. + +The genus _Arachnopila_, together with the two following genera, forms the +peculiar small group of large Arachnosphaerida, separated from the true +Caryommida by the totally different structure and disposition of the +numerous concentric shells; the former exhibits a similar relation to the +latter that the Diplosphaerida bears to the Elatommida among the +dispherical Haliommida. The concentric shells (five to ten or more) lie +outside the central capsule, and are composed of very delicate, cobweb-like +threads. From the innermost shell arise numerous, three-sided prismatic, +very long spines, from which at equal regular distances arise lateral +branches (three pairs from each spine, and one pair from each corner). In +_Arachnopila_ these threads pass directly from one spine to the other, and +form simple, large, triangular meshes between them. The concentric shells +are not connected by interwoven diagonal threads. + + +1. _Arachnopila hexagonella_, n. sp. + +Innermost shell with regular hexagonal pores; its diameter twice as long as +the equal distance between every two concentric shells. Radial spines +twenty to forty, each with twenty to twenty-four verticils. + +_Dimensions._--Diameter of the innermost shell 0.1; distance between the +concentric shells 0.05. + +_Habitat._--Central Pacific, Station 271, surface. + + +2. _Arachnopila polygonella_, n. sp. + +Innermost shell with irregular, polygonal pores; its diameter fully as long +as the equal distance between every two concentric shells. Radial spines +sixty to eighty, each with twelve to sixteen verticils. + +_Dimensions._--Diameter of the innermost shell 0.04; distance between the +concentric shells 0.04. + +_Habitat._--Central Pacific, Station 266, surface. + + + +{267}Genus 109. _Arachnopegma_,[147] Haeckel, 1881, Prodromus, p. 454. + +_Definition._--#Astrosphaerida# with five to ten or more cortical, +concentric, polyhedral, or spherical lattice-shells, composed of a very +thin, cobweb-like network; innermost shell with hexagonal or polygonal +meshes; other shells with simple triangular meshes, connected to one +another by diagonal threads between them. + +The genus _Arachnopegma_ differs from its ancestral form _Arachnopila_, in +the possession of peculiar diagonal threads, which connect the verticils or +nodal-points of every two neighbouring radial spines in two different +neighbouring concentric shells. In this case, therefore, not only do +triangular meshes lie in the spherical faces of the concentric spheres, but +also between them, in numerous oblique diagonal planes; a very rare and +remarkable structure, and forming a transition to spongy shells. + + +1. _Arachnopegma verticillatum_, n. sp. + +Innermost shell with regular, hexagonal meshes; its diameter is the same as +the equal distance between each of the two shells. Threads of the network +smooth. Radial spines twenty to forty, each with fifteen to twenty +verticils. + +_Dimensions._--Diameter of the innermost shell 0.04, distance between the +concentric shells 0.03 to 0.04. + +_Habitat._--Central Pacific, Station 266, surface. + + +2. _Arachnopegma longispinum_, n. sp. + +Innermost shell with regular, hexagonal meshes; its diameter half as large +as the equal distance between every two shells. Threads of the network +dentated or with small knots. Radial spines fifty to sixty, each with +twenty to twenty-five verticils. + +_Dimensions._--Diameter of the innermost shell 0.02; distance between the +concentric shells 0.04 to 0.05. + +_Habitat._--Central Pacific, Station 272, surface. + + +3. _Arachnopegma increscens_, n. sp. + +Innermost shell with regular, hexagonal meshes; its diameter quite as large +as the distance between it and the second shell; only half as large as the +distance between the fourth and fifth shells. Forty to fifty radial spines, +each with fifteen to twenty verticils. + +_Dimensions._--Diameter of the innermost shell (A) 0.025; distance between +the following shells--A, B = 0.025, B, C = 0.03, C, D = 0.04, D, E = 0.048, +E, F = 0.056, F, G = 0.064, &c. + +_Habitat._--Central Pacific, Station 274, surface. + + + +{268}Genus 110. _Arachnosphaera_,[148] Haeckel, 1862, Monogr. d. Radiol., +p. 355. + +_Definition._--#Astrosphaerida# with five to ten or more cortical, +concentric, polyhedral, or spherical lattice-shells, composed of a very +thin cobweb-like network; innermost shell with hexagonal (regular) or +polygonal (irregular) meshes; other shells with larger, irregular, +polygonal meshes. + +The genus _Arachnosphaera_ (accurately described by me in 1862, _loc. +cit._) differs from the two preceding genera in the irregular form of the +large meshes in all shells (except often the innermost). This is caused by +the ramification of the thin threads, which on each shell connect the +neighbouring spines. In _Arachnopila_ and _Arachnopegma_ the threads pass +directly and undivided from each spine to the neighbouring spine (three +pairs from the three edges), and therefore all meshes are triangular. In +_Arachnosphaera_ they become polygonal by irregular ramification of the +threads. There are here no diagonal threads. + + + +Subgenus 1. _Arachnosphaerella_, Haeckel. + +_Definition._--Pores of the innermost shell regular, hexagonal. + + +1. _Arachnosphaera oligacantha_, Haeckel. + + _Arachnosphaera oligacantha_, Haeckel, 1862, Monogr. d. Radiol., p. 356, + Taf. x. fig. 2, Taf. xi. fig. 3. + +Innermost shell with regular, hexagonal meshes; its diameter three times as +long as the equal distances between every two concentric shells. Fifteen to +twenty radial spines scattered at wide intervals, each with six to eight +verticils. + +_Dimensions._--Diameter of the innermost shell 0.12; distance between the +concentric shells 0.04 to 0.05. + +_Habitat._--Mediterranean (Messina), surface, Haeckel. + + +2. _Arachnosphaera myriacantha_, Haeckel. + + _Arachnosphaera myriacantha_, Haeckel, 1862, Monogr. d. Radiol., p. 357, + Taf. x. fig. 3, Taf. xi. fig. 4. + +Innermost shell with regular, hexagonal meshes; its diameter twice as long +as the equal distances between every two concentric shells. At each +nodal-point occurs one radial spine with six to eight verticils (spines in +all one hundred to one hundred and twenty or more). + +_Dimensions._--Diameter of the innermost shell 0.1; distance between the +concentric shells 0.04 to 0.05. + +_Habitat._--Cosmopolitan; Mediterranean, Atlantic, Indian, Pacific, +surface. + + +{269}3. _Arachnosphaera dolichacantha_, n. sp. + +Innermost shell with regular, hexagonal meshes, very small; its diameter +only as long as the equal distances between every two concentric shells. At +each nodal-point occurs one radial spine with twelve to sixteen verticils +(altogether thirty to forty spines). + +_Dimensions._--Diameter of the innermost shell 0.05; distance between the +concentric shells 0.04 to 0.05. + +_Habitat._--Central Pacific, Station 265 to 274, surface. + + +4. _Arachnosphaera increscens_, n. sp. + +Innermost shell with regular, hexagonal meshes; its diameter three times as +long as the distance between it and the second shell, quite as long as the +distance between the fifth and sixth shells; the distances between the +concentric shells gradually increasing from the centre. Radial spines about +fifty to sixty, each with six to eight verticils. + +_Dimensions._--Diameter of the innermost shell (A) 0.75; distances between +the following shells--A, B = 0.025, B, C = 0.037, C, D = 0.05, D, E = +0.062, E, F = 0.075, &c. + +_Habitat._--Central Pacific, Station 271, surface. + + + +Subgenus 2. _Arachnosphaeromma_, Haeckel. + +_Definition._--Pores of the innermost shell irregular, polygonal. + + +5. _Arachnosphaera tenuissima_, n. sp. + +Innermost shell with irregular, polygonal meshes; its diameter twice as +long as the equal distance between every two concentric shells. Forty to +fifty radial spines, each with twelve to sixteen verticils. + +_Dimensions._--Diameter of the innermost shell 0.1, distance between the +concentric shells 0.04 to 0.05. + +_Habitat._--South Atlantic, Station 332, surface. + + +6. _Arachnosphaera velaris_, n. sp. + +Innermost shell with irregular, polygonal meshes; its diameter twice as +long as the distance between it and the second shell, quite as long as the +distance between the third and fourth shells; the distance between the +concentric shells gradually increasing from the centre. Radial spines +twenty to thirty, each with ten to twelve verticils. + +_Dimensions._--Diameter of the innermost shell (A) 0.5; distances of the +following shells--A, B = 0.025, B, C = 0.037, C, D = 0.05, D, E = 0.062, E, +F = 0.075. + +_Habitat._--Tropical Atlantic, Station 347, surface. + + + +{270}Subfamily SPONGIOMMIDA,[149] Haeckel. + +_Definition._--#Astrosphaerida# with spongy spherical or polyhedral shell +(with or without enclosed concentric lattice-shells). + + + +Genus 111. _Spongiomma_,[150] n. gen. + +_Definition._--#Astrosphaerida# with solid spongy sphere, with numerous +simple radial spines, but without latticed medullary shells. + +The genus _Spongiomma_ differs from its ancestral form, _Styptosphaera_, in +the development of simple radial spines on the surface of the solid sphere, +the entire mass of which is composed of an irregular, spongy wicker-work. + + + +Subgenus 1. _Spongiommella_, Haeckel. + +_Definition._--Radial spines on the surface of the spongy sphere all of the +same shape. + + +1. _Spongiomma radiatum_, n. sp. + +Spongy framework of the solid sphere of the same structure throughout, with +small, irregular, polyhedral meshes and very thin thread-like bars. From +the surface arise very numerous (one hundred and twenty to one hundred and +sixty or more) straight, bristle-shaped radial spines, as long as the +radius of the sphere (counting from the middle part of it). + +_Dimensions._--Diameter of the spongy sphere 0.2; length of the radial +spines 0.1. + +_Habitat._--Central Pacific, Station 272, surface. + + +2. _Spongiomma denticulatum_, n. sp. + +Spongy framework of the solid sphere of the same structure throughout, with +small, almost equal meshes, four to eight times as broad as the thin, +elegantly denticulated bars; from the surface arise very numerous (two +hundred to three hundred or more) curved, radial spines, as long as the +radius, and of the same form as the bars. + +_Dimensions._--Diameter of the sphere 0.25; length of the spines 0.12. + +_Habitat._--Central Pacific, Station 274, surface. + + +3. _Spongiomma spathillatum_, n. sp. + +Spongy framework in the central part of the sphere much denser and darker, +and with smaller meshes than in the peripheral part in which are very thin +bars. Entire surface covered with {271}innumerable short, bristle-shaped +radial spines, only one-eighth as long as the radius, of the same elegant +form as in _Octodendron spathillatum_ (Pl. 18, figs. 2, 4); each spine +developed in a zig-zag fashion, with very small beards, with a delicate +spathillum (or coronal of beard spines) at the distal end. + +_Dimensions._--Diameter of the spheres 0.16; length of the spines 0.01. + +_Habitat._--South Pacific, Station 295, surface. + + +4. _Spongiomma clavatum_, n. sp. + +Spongy framework in the central part of the sphere much denser and darker +than in the peripheral part. On the surface are sixty to eighty stout, +club-shaped radial spines, as long as the radius of the sphere, in the +proximal half three-sided prismatic, with three dentated edges; they begin +at the middle of the radius (where the denser inner framework changes into +the looser outer) and are very thin at first but increase slowly in +thickness towards the truncated distal end. (Similar to _Centrocubus +rhopalophorus_, Pl. 18, fig. 1, but without the cubical medullary shell.) + +_Dimensions._--Diameter of the sphere 0.4; length of the spines 0.2. + +_Habitat._--North Pacific, Station 241, surface. + + + +Subgenus 2. _Spongiommura_, Haeckel. + +_Definition._--Radial spines on the surface of the spongy sphere of two +different kinds; large main spines and small by-spines. + + +5. _Spongiomma helioides_, n. sp. + +Spongy framework of the sphere everywhere of the same structure, with +almost equal meshes, ten to twelve times as broad as the bars. Sixteen to +twenty radial main spines, longer than the shell diameter, three-sided +prismatic, with three serrated edges, beginning about the middle of the +radius and increasing in thickness to the truncated distal end. Between +them occur numerous thin, bent, bristle-shaped by-spines. (Very similar to +_Spongosphaera helioides_, Monogr. d. Radiol., Taf. xii. figs. 11-13, but +without medullary shells.) + +_Dimensions._--Diameter of the sphere 0.3; length of the main spines 0.4, +of the by-spines 0.01. + +_Habitat._--Tropical Atlantic, Station 352, surface. + + +6. _Spongiomma multiaculeum_, Haeckel. + + _Spongechinus multiaculeatus_, Dunikowski, 1882, Denkschr. d. k. Akad. d. + Wiss. Wien, Bd. xlv. p. 29, Taf. v. figs. 60-63. + +Spongy framework of the sphere very compact, with small meshes, scarcely +broader than the bars; four to eight large main spines, three-sided +pyramidal, longer than the shell radius; numerous (thirty to forty) thin +by-spines, scarcely half as long. + +{272}_Dimensions._--Diameter of the sphere 0.16; length of the main spines +0.11, of the by-spines 0.03. + +_Habitat._--Fossil in the Alpine Jura, Schafberg near Salzburg +(Dunikowski). + + +7. _Spongiomma asteroides_, n. sp. + +Spongy framework in the central part of the sphere much denser and darker +than in the peripheral part. Sixty to eighty cylindro-conical main spines, +as long as the radius, between them are numerous straight, bristle-shaped +by-spines half that length. + +_Dimensions._--Diameter of the sphere 0.28; length of the main spines 0.16, +of the by-spines 0.08. + +_Habitat._--South Atlantic, Station 325, surface. + + + +Genus 112. _Spongodrymus_,[151] Haeckel, 1881, Prodromus, p. 456. + +_Definition._--#Astrosphaerida# with solid spongy sphere, without latticed +medullary shell, with numerous branched radial spines. + +The genus _Spongodrymus_ differs from the preceding _Spongiomma_ in the +ramification of the numerous radial spines, covering the surface of the +solid spongy sphere. + + +1. _Spongodrymus elaphococcus_, n. sp. (Pl. 18, fig. 9). + +Spongy framework of the solid sphere equal throughout, on the surface +arising in the form of very numerous (sixty to eighty or more) spongy cones +with rather rhomboidal meshes. Each cone is prolonged into a very thin, +irregularly curved radial spine, which is twice as long as the shell +diameter, simple in the proximal half, branched like a tree in the distal +half; each arborescent spine has from sixteen to thirty-two terminal +branches, which fall in one spherical face. The branches of neighbouring +spines are partly connected by anastomoses, so that they begin to form an +outer spherical shell (cortical shell) with a looser spongy framework. + +_Dimensions._--Diameter of the whole spherical skeleton (sphere formed by +the distal ends of the dichotomous branches) 0.9, of the inner solid spongy +sphere 0.02. + +_Habitat._--Tropical Atlantic, Station 349, surface. + + +2. _Spongodrymus abietinus_, n. sp. + +Spongy framework denser and darker in the central part of the sphere than +in the peripheral part, with rather coarse meshes and thick bars. From the +surface arise very numerous (sixty to eighty) stout, radial branches, as +long as the shell radius, branched like a pine tree (with six to twelve +ramified branches). Similar in structure to _Cromyodrymus abietinus_ (Pl. +30, fig. 6), but with a quite irregular spongy texture in the central +sphere. + +_Dimensions._--Diameter of the sphere 0.3; length of the spines 0.015. + +_Habitat._--Central Pacific, Station 272, surface. + + + +{273}Genus 113. _Spongechinus_,[152] Haeckel, 1881, Prodromus, p. 456. + +_Definition._--#Astrosphaerida# with hollow, spongy sphere, without +latticed medullary shell in the central cavity, and with numerous simple +radial spines. + +The genus _Spongechinus_ differs from its ancestral form, _Plegmosphaera_, +in the development of numerous radial spines on the surface of the spongy +sphere, within which is enclosed a large spherical central cavity. + + +1. _Spongechinus setosus_, n. sp. + +Spongy sphere three times as broad as its inner cavity, with a very +delicate, equal framework. Entire surface covered with short, straight, +bristle-shaped radial spines, about half as long as the radius. + +_Dimensions._--Diameter of the sphere 0.2, of its inner cavity 0.07; length +of the spines 0.05. + +_Habitat._--North Atlantic, Azores, surface. + + +2. _Spongechinus serrulatus_, n. sp. + +Spongy sphere twice as broad as its inner cavity, with a delicate, equal +framework. Entire surface covered with short, curved, radial spines, which +are elegantly denticulated, and as long as the shell radius. + +_Dimensions._--Diameter of the sphere 0.3, of its cavity 0.15; length of +the spines 0.15. + +_Habitat._--Central Pacific, Station 274, surface. + + +3. _Spongechinus cavus_, n. sp. + +Spongy sphere only one-fourth broader than the large inner cavity, its +spongy wall being only one-fourth as thick as the radius, composed of three +to four strata of irregular, small meshes. Surface covered with short, +bristle-shaped, curved spines, one-third as long as the radius. + +_Dimensions._--Diameter of the sphere 0.5, of its inner cavity 0.4; length +of the spines 0.08. + +_Habitat._--North Atlantic, Station 354, surface. + + + +Genus 114. _Spongothamnus_,[153] n. gen. + +_Definition._--#Astrosphaerida# with hollow, spongy sphere, without +latticed medullary shell in the central cavity, and with numerous branched +radial spines. + +The genus _Spongothamnus_ differs from the preceding _Spongechinus_ in the +ramification of the numerous radial spines, covering the surface of the +hollow spongy sphere; {274}it therefore exhibits the same relation to the +latter that _Spongodrymus_ bears to _Spongiomma._ + + +1. _Spongothamnus furcatus_, n. sp. + +Spongy sphere twice as broad as its inner cavity, with very delicate bars, +and irregular, dense framework. From the surface arise one hundred and +fifty to one hundred and eighty thin, forked, bristle-shaped spines, half +as long as the radius; both fork branches one-third as long as the basal or +simple part. + +_Dimensions._--Diameter of the sphere 0.3, of its inner cavity 0.15; length +of the spines 0.08. + +_Habitat._--North Pacific, Station 241, surface. + + +2. _Spongothamnus scoparius_, n. sp. + +Spongy sphere four times as broad as its inner cavity, with thick bars and +rather loose framework. From the surface arise sixty to eighty broom-shaped +radial spines, as long as the radius, each in the basal half simple, in the +distal half with six to twelve irregularly ramified branches (similar to +the spines of _Cromyodrymus abietinus_, Pl. 30, fig. 6). + +_Dimensions._--Diameter of the sphere 0.4, of the inner cavity 0.1; length +of the spines 0.2. + +_Habitat._--Central Pacific, Station 271, surface. + + + +Genus 115. _Spongopila_,[154] Haeckel, 1881, Prodromus, p. 456. + +_Definition._--#Astrosphaerida# with a single, spherical, latticed +medullary shell, immediately enveloped by the spongy framework of the +cortical shell; on the surface of the latter are numerous radial spines. + +The genus _Spongopila_ is a _Spongoplegma_ with radial spines. On the other +hand it may be derived either from _Elaphococcus_, by communication of the +branched spines, or from _Arachnosphaera_, by development of spongy +branches between the concentric spheres. + + +1. _Spongopila dichotoma_, n. sp. + +Medullary shell with regular, hexagonal meshes, six times as broad as the +bars. From each nodal-point (between every three meshes) arises a +bristle-shaped radial spine, which is dichotomously branched. By +communication of the neighbouring branches the loose spongy framework of +the spherical cortical shell is formed, which is four times as broad as the +medullary shell. On the surface occur very numerous bristle-shaped radial +spines, as long as the diameter of the medullary shell. (May be derived +from _Elaphococcus_.) + +_Dimensions._--Diameter of the spongy cortical shell 0.3, of the medullary +shell 0.08. + +_Habitat._--Tropical Atlantic, Station 347, surface. + + +{275}2. _Spongopila verticillata_, n. sp. + +Medullary shell with regular, hexagonal meshes, four times as broad as the +bars. From its surface arise forty to sixty, three-sided prismatic radial +spines, bearing eight to ten verticils of lateral branches, each verticil +with six forked branches (two from each edge). By irregular ramification of +these branches, and communication in all directions, the loose spongy +framework of the cortical shell originates, which is six times as broad as +the medullary shell. The free distal ends of the spines are as long as the +shell radius. (May be derived from _Arachnosphaera_.) + +_Dimensions._--Diameter of the spongy cortical shell 0.6, of the medullary +shell 0.1. + +_Habitat._--Tropical Pacific, Station 200, surface. + + + +Genus 116. _Rhizoplegma_,[155] Haeckel, 1881, Prodromus, p. 456. + +_Definition._--#Astrosphaerida# with a single, spherical, latticed +medullary shell, which is not armed with by-spines, but connected by stout +radial main spines with the spongy cortical shell. + +The genus _Rhizoplegma_ is immediately allied to the foregoing +_Spongopila_, but differs from it in the large interval separating both +shells. In this interval lies the wall of the central capsule, which is +only pierced by the radial spines connecting both shells. + + + +Subgenus 1. _Rhizoplegmarium_, Haeckel. + +_Definition._--No free lateral branches of the radial spines between the +two shells. + + +1. _Rhizoplegma polyacanthum_, n. sp. + +Spongy cortical shell with a very fine dense framework and nearly smooth +surface (without superficial by-spines). Its inner cavity is four times as +broad as the medullary shell, which exhibits regular, hexagonal meshes. +Radial spines sixty to eighty, three-sided prismatic, with three smooth +edges, without lateral branches between both shells; their free outer part +as long as the shell radius. + +_Dimensions._--Diameter of the spongy cortical shell 0.3, of its inner +cavity 0.2, of the medullary shell 0.05. + +_Habitat._--Central Pacific, Station 274, surface. + + +2. _Rhizoplegma spirale_, n. sp. + +Spongy cortical shell with a very delicate loose framework and bristly +surface. Its inner cavity three times as broad as the medullary shell, +which exhibits regular, hexagonal meshes. {276}Radial spines thirty to +forty, prismatic, with three smooth, spirally contorted edges, without +lateral branches between the two shells; their free outer part half as long +as the shell radius. + +_Dimensions._--Diameter of the spongy cortical shell 0.2, of its inner +cavity 0.12, of the medullary shell 0.04. + +_Habitat._--Central Pacific, Station 265, surface. + + +3. _Rhizoplegma trigonacantha_, n. sp. + +Spongy cortical shell with a rather loose framework and coarse bars, with +nearly smooth surface (without by-spines). Its inner cavity twice as broad +as the medullary shell, which exhibits irregular, roundish pores. Radial +spines forty to sixty, prismatic, with three smooth straight edges, without +free branches between the two shells; their outer pyramidal part only +one-third of the shell radius. (Very similar to the common _Rhizosphaera +trigonacantha_, but with simple medullary shell.) + +_Dimensions._--Diameter of the spongy shell 0.2, of its inner cavity 0.16, +of the medullary shell 0.08. + +_Habitat._--North Atlantic, Station 353, surface. + + + +Subgenus 2. _Rhizoplegmidium_, Haeckel. + +_Definition._--Between the two shells free lateral branches arise from the +three edges of the radial spines. + + +4. _Rhizoplegma radicatum_, n. sp. (Pl. 15, figs. 9, 9_a_). + +Spongy cortical shell with a very loose framework; on the surface are +innumerable thin, forked, or repeatedly dichotomous by-spines. Its inner +cavity three times as broad as the medullary shell, which exhibits regular, +hexagonal meshes (fig. 9_a_). Radial spines twelve, prismatic, with +straight dentated edges, their outer pointed part as long as the shell +radius. Each spine between the two shells has a verticil of three forked +lateral branches (fig. 9_a_). The central capsule completely distends the +medullary shell, and forces out through each mesh a hernia-shaped process +(fig. 9). + +_Dimensions._--Diameter of the spongy shell 0.5, of its inner cavity 0.25, +of the medullary shell 0.08. + +_Habitat._--Central Pacific, Station 271, surface. + + +5. _Rhizoplegma lychnosphaera_, n. sp. (Pl. 11, fig. 5). + + _Lychnosphaera rhizoplegma_, Haeckel, 1879, Atlas (pl. xi. fig. 5). + +Spongy cortical shell with a very loose framework, composed of long thin +beams as in _Lychnosphaera regina_ (Pl. 11, figs. 1-4). Surface covered +with short bristles. Its inner cavity six times as broad as the medullary +shell, which exhibits regular, hexagonal meshes. Radial spines twelve, +prismatic, with three smooth edges; their outer pointed part half as long +as the shell radius. Each spine has three verticils of three forked +branches; the first verticil is free {277}between the two shells, while the +two following verticils, by communication of their ramules, form the +irregular framework. Central capsule with many herniae, forced out through +the meshes of the medullary shell (fig. 5). + +_Dimensions._--Diameter of the spongy shell 0.7, of its inner cavity 0.45, +of the medullary shell 0.07. + +_Habitat._--South Pacific, Station 284, surface. + + + +Genus 117. _Lychnosphaera_,[156] Haeckel, 1881, Prodromus, p. 453. + +_Definition._--#Astrosphaerida# with a single, spherical, latticed +medullary shell, which is armed with free radial by-spines, and connected +by stout radial main spines with the spongy cortical shell. + +The genus _Lychnosphaera_, known only by one single, large, and very +remarkable species, mainly differs from the foregoing in the development of +free radial by-spines on the surface of the medullary shell, and in the +free interval between it and the cortical shell; but beyond this the loose +spongy framework of the latter exhibits a very remarkable structure, +figured in Pl. 11. + + +1. _Lychnosphaera regina_ (Pl. 11, figs. 1-4). + +Medullary shell (fig. 3) with regular, circular, hexagonally framed pores, +twice as broad as the bars; from each hexagon-corner arises a radial, +bristle-shaped by-spine, as long as the diameter. Twelve radial main spines +each as broad as one of the meshes, three-sided prismatic, six to eight +times as long as the medullary shell. From their three leaf-shaped (often +somewhat denticulated or spirally contorted) edges arise four verticils of +lateral branches, each composed of three forked, thin branches. The forked +branches of the first verticil end free between the two shells (figs. 2, +3), while the two following verticils are ramified, and, by anastomosis of +their branches, compose the loose spongy framework of the cortical shell. +On the surface of the latter arise numerous radial (zig-zag-shaped) +by-spines. The fourth verticil is terminal, with three shorter, thicker, +dentated, simple branches, which constitute, together with the distal apex +of the spine itself, a bunch of four terminal spines. The large central +capsule completely distends the medullary shell, and forces out by its +pores numerous club-shaped herniae (fig. 1). + +_Dimensions._--Diameter of the spongy cortical shell 0.6, of its inner +cavity 0.4, of the central capsule 0.22, of the medullary shell 0.06; +length of the radial spines 0.4, breadth 0.01. + +_Habitat._--Central Pacific, Station 271, surface. + + + +Genus 118. _Centrocubus_,[157] n. gen. + +_Definition._--#Astrosphaerida# with a single, cubical medullary shell, +immediately surrounded by the spongy framework of the cortical shell; from +the eight corners {278}of the central cube arise eight primary radial +spines, and often others from the framework between them. + +The genus _Centrocubus_ and the following closely allied _Octodendron_ may +represent a peculiar small group of Spongiommida, remarkable for the +regular, cubical form of the medullary shell, which is composed of twelve +thin rods, corresponding to the twelve edges of a mathematical cube; from +the eight corners invariably arise eight primary radial spines, the +branches of which form the spongy cortical shell. + + +1. _Centrocubus octostylus_, n. sp. + +Radial spines eight, arising from the eight corners of the cubiform, +regular, medullary shell, gradually increasing in thickness towards the +club-shaped distal end, which is five to six times as broad as the central +end. From the three denticulate edges of each spine arise six to eight +lateral branches, which ramify irregularly and form by their anastomosis +the spongy framework which is of nearly similar structure throughout, and +with large loose meshes. The free distal part of each spine is half as long +as the enclosed part. + +_Dimensions._--Diameter of the sphere 0.6, of the central cube 0.02; length +of the spines 0.15, distal thickness 0.02. + +_Habitat._--Central Pacific, Station 271, surface. + + +2. _Centrocubus cladostylus_, n. sp. (Pl. 18, fig. 1). + +Radial spines thirty-two, club-shaped, at the distal end eight to ten times +as broad as at the basal end. Eight primary spines arise from the eight +corners of the regular, cubiform medullary shell, and from these, in the +form of lateral branches, twenty-four secondary spines arise with concavely +curved bases (three from the three denticulate edges of each spine, at +nearly equal distances from the centre). The free distal end of each of the +thirty-two spines is of the same shape, about half as long as the radius of +the spongy sphere; framework much looser in the outer than in the inner +part. + +_Dimensions._--Diameter of the sphere 0.8, of the central cube 0.02; length +of the spines 0.2, distal thickness 0.02. + +_Habitat._--North Pacific, Station 256, surface. + + +3. _Centrocubus polystylus_, n. sp. + +Radial spines sixty to eighty, club-shaped, four to six times as broad at +the distal as at the basal end. Eight primary spines arise from the eight +corners of the regular, cubiform medullary shell, the remainder either +springing as lateral branches from the three denticulate corners of the +former, or arising within the spongy framework, which is much denser and +darker in the central than in the peripheral part. The free distal end of +each spine is one-third as long as the radius. + +{279}_Dimensions._--Diameter of the sphere 0.9, of the central cube 0.02; +length of the spines 0.15, distal thickness 0.02. + +_Habitat._--South Pacific, Station 295, surface. + + + +Genus 119. _Octodendron_,[158] n. gen. + +_Definition._--#Astrosphaerida# with a single, cubical medullary shell, and +eight primary radial spines arising from its eight corners; these are +connected at equal distances by a latticed, spherical, cortical shell, from +which the spongy framework directly springs; often from the latter +secondary radial spines arise. + +The genus _Octodendron_ has the same regular, cubical medullary shell as +the preceding _Centrocubus_, but differs from it in the wide interval +separating the medullary shell from the inner spherical face of the spongy +cortical shell, the two being connected only by eight radial beams, arising +from the eight corners of the cube. + + + +Subgenus 1. _Octodendridium_, Haeckel. + +_Definition._--Only eight primary radial spines, arising from the eight +corners of the central cube. + + +1. _Octodendron cubocentron_, n. sp. (Pl. 18, fig. 3). + +Radial spines eight, club-shaped, with three denticulate, straight edges, +twice as long as the diameter of the central cavity of the cubical spongy +shell; the inner face of the latter (or the "inner cortical shell") +exhibits the form of a large cube, the spongy sides of which are parallel +with the simple square sides of the central cube. The thin eight radial +beams, connecting the corresponding corners of both cubes, are not thicker +than the edge-bars of the central cube, whilst their outer prolongations +are much thicker, with four to six verticils of lateral branches. Surface +of the thin walled, loose, spongy shell armed with short simple thorns. + +_Dimensions._--Diameter of the spongy shell 0.2, of its inner cavity 0.1, +of the central cube 0.02; length of the spines 0.2 (from the centre 0.3). + +_Habitat._--Central Pacific, Station 266, surface. + + +2. _Octodendron spirale_, n. sp. + +Radial spines eight, three-sided prismatic, three times as long as the +diameter of the inner shell-cavity; their three edges denticulated and +spirally contorted around the spine axis. Thickness of the loose spongy +shell-wall equal to the radius of the inner cavity, three times as large as +the central cube. Surface covered, with numerous thin, bristle-shaped, bent +spinules. + +{280}_Dimensions._--Diameter of the spongy shell 0.24, of its inner cavity +0.12, of the central cube 0.02; length of the spines 0.4, breadth 0.01. + +_Habitat._--North Pacific, Station 254, surface. + + +3. _Octodendron pinetum_, n. sp. + +Radial spines eight, three-sided prismatic, three to four times as long as +the diameter of the inner shell-cavity, with three spirally contorted +edges. From each spine arise at equal distances (equal to the half radius +of the cavity) fifteen to twenty verticils of branches which increase in +size from the base of the spine. Each verticil is composed of six forked +branches (two from each spine-edge); the inferior are richly branched, and +form by their connection the loose network of the spongy cortical shell, +the surface of which is covered with numerous bent threads. Each spine +bears a resemblance to a pine tree. + +_Dimensions._--Diameter of the spongy shell 0.3, of its inner cavity 0.15, +of the central cube 0.02; length of the spines 0.5 to 0.6, breadth 0.01. + +_Habitat._--Central Pacific, Station 272, surface. + + +4. _Octodendron araucaria_, n. sp. + +Radial spines eight, three-sided prismatic, with three spirally contorted +edges, eight to ten times as long as the diameter of the inner shell-cavity +(the free distal portion twice to three times as long). From each spine +arise at equal distances thirty to thirty-five verticils of branches, which +decrease in size towards the distal end. Each verticil is composed of six +forked branches (two from each spine-edge); the inferior are richly +ramified and form by their connection the loose spongy framework; the +distal branches bear on the free end elegant spathillae (as in the +following species). Surface covered with innumerable straight bristles, as +long as the cavity radius, and ending with a spathilla. Diameter of the +central capsule about equal to the radius of the spongy sphere, its +membrane is double-edged. + +_Dimensions._--Diameter of the spongy shell 1.4 mm., of its inner cavity +0.14, of the central cube 0.02, of the central capsule 0.5 to 0.6; length +of the spines 0.9 to 1.2, breadth 0.02. + +_Habitat._--South Pacific, Station 288, surface. + + +5. _Octodendron spathillatum_, n. sp. (Pl. 18, figs. 2, 4). + +Radial spines eight, three-sided prismatic, with contorted edges, five to +eight times as long as the diameter of the shell-cavity (the free part +twice as long). From each spine arise ten to twelve verticils of lateral +branches; each verticil composed of three forked branches. The proximal +larger branches ramify richly, and form by their connection the loose +spongy framework of the spherical shell; the distal smaller branches are +simple or bifurcated, and the ramules are provided with an elegant +spathillum at the end (fig. 4). Entire surface of the spongy sphere covered +with innumerable bristle-shaped radial spines (half as long as the cavity +radius), zig-zag, bent, with beards, and with a spathillum at the end. + +{281}_Dimensions._--Diameter of the spongy sphere 1 mm., of its central +cavity 0.15, of the central cube 0.02; length of the spines 1 to 1.2 mm., +breadth 0.008. + +_Habitat._--Central Pacific, Station 271, surface. + + + +Subgenus 2. _Octodendronium_, Haeckel. + +_Definition._--Radial spines thirty-two or more, eight primary (arising +from the eight corners of the central cube) and twenty-four or more +secondary (between them). + + +6. _Octodendron verticillatum_, n. sp. + +Radial spines thirty-two, with three denticulate straight edges, six to +eight times as long as the diameter of the shell-cavity; the distal parts +half free. Eight primary spines arise from the eight corners of the central +cube, twenty-four secondary from the edges of these (a verticil of every +three from each primary spine). Distal free parts of all thirty-two spines +equal. Each spine with eight to ten verticils of forked lateral branches, +without spathillae. Surface of the spongy sphere covered with short simple +bristles. + +_Dimensions._--Diameter of the spongy shell 0.3, of its cavity 0.12, of the +central cube 0.02; length of the spines 0.7 to 1 mm., breadth 0.02. + +_Habitat._--South Pacific, Station 291, surface. + + +7. _Octodendron contortum_, n. sp. + +Radial spines thirty-two, disposed in a similar manner to those of the +former species (eight primary and twenty-four secondary); also the spongy +shell of the same shape. The difference arises in the form of the spines, +the three edges of which are much broader and spirally contorted around the +axis; and thus the corresponding branches of the verticil do not lie in the +same meridian-plane, but alternate one with another. + +_Dimensions._--Diameter of the spongy shell 0.4, of its cavity 0.1, of the +central cube 0.02; length of the spines 0.8 to 1.2, breadth 0.04. + +_Habitat._--Central Pacific, Station 274, surface. + + +8. _Octodendron arboretum_, n. sp. + +Radial spines sixty to ninety, three-sided prismatic, with spirally +contorted and denticulate edges, six to eight times as long as the diameter +of the inner shell-cavity. Eight primary arise from the eight corners of +the central cube, twenty-four others from their three edges (as in the two +former species); the remaining thirty to sixty spines seem to arise between +the former and immediately from the dense spongy framework, which is twice +as thick as the diameter of the inner shell-cavity. The numerous verticils +of the free distal part are of equal shape in all the spines, composed of +three forked branches in the terminal, and of more ramified branches in the +inferior parts. Entire surface of the spongy shell covered with simple +radial bristles, without spathillae. + +{282}_Dimensions._--Diameter of the spongy shell 0.75, of its central +cavity 0.15, of the central cube 0.02; length of the spines 0.9 to 1.2, +breadth 0.02. + +_Habitat._--Tropical Pacific, Station 225, surface. + + + +Genus 120. _Spongosphaera_,[159] Ehrenberg, 1847, Monatsber. d. k. preuss. +Akad. d. Wiss. Berlin, p. 54. + +_Definition._--#Astrosphaerida# with two concentric latticed medullary +shells, connected by radial beams; the outer is immediately enveloped by +the spongy framework, and bears numerous radial spines. + +The genus _Spongosphaera_ (in the definition here restricted) differs from +_Spongopila_ in the double medullary shell, which in the latter is simple; +it exhibits to the latter the same relation that _Spongodictyon_ among the +Liosphaerida bears to _Spongoplegma_. The outer medullary shell of +_Spongosphaera_ is immediately enveloped by the spongy wicker-work, which +everywhere pierces the wall of the central capsule. + + +1. _Spongosphaera streptacantha_, Haeckel. + + _Spongosphaera streptacantha_, Haeckel, 1862, Monogr. d. Radiol., p. 455, + Taf. xxvi. figs. 1-3. + +Spongy shell of polyhedric, irregular outline, the framework being +prolonged sheath-like into the eight to twelve radial spines, which are +quite irregularly distributed, very large, three-sided prismatic, with +three serrated, spirally contorted edges; their length is twice to four +times as great as the diameter of the spongy body; they arise with thinner +bases from the outer medullary shell, which is three times as broad as the +inner, both having roundish pores, twice to four times as broad as the +bars; surface without radial by-spines. + +_Dimensions._--Diameter of the spongy shell 0.2 to 0.6, outer medullary +shell 0.04 to 0.06, inner 0.012 to 0.016. + +_Habitat._--Cosmopolitan; common in all warmer seas, surface. + + +2. _Spongosphaera polyacantha_, J. Mueller. + + _Spongosphaera polyacantha_, J. Mueller, 1858, Abhandl. d. k. Akad. d. + Wiss. Berlin, p. 32, Taf. iv. figs. 1-4. + +Spongy shell spherical, with ten to twenty large radial spines, which arise +with thinner bases from the medullary shell, and are prominent on the +surface at different lengths; they are three-sided prismatic (not +four-sided), with three leaf-shaped straight edges. Whilst the spongy +framework is much looser than in the preceding species, both medullary +shells have nearly the same shape. + +_Dimensions._--Diameter of the spongy shell 0.2 to 0.5, outer medullary +shell 0.04 to 0.06, inner 0.012 to 0.016. + +_Habitat._--Mediterranean (Nice); Atlantic, Station 353, surface. + + + +{283}Subgenus _Spongosphaeromma_, Haeckel. + +_Definition._--Radial spines on the surface of the spongy shell of two +different kinds; large piercing main spines and small superficial +by-spines. + + +3. _Spongosphaera helioides_, Haeckel. + + _Spongosphaera helioides_, Haeckel, 1862, Monogr. d. Radiol., p.456, Taf. + xii. figs. 11-13. + +Spongy shell spherical, with numerous curved, bristle-shaped by-spines on +the surface, as long as the radius. Main spines ten to twenty, irregularly +disposed, prismatic, with three dentated, spirally contorted edges, broader +toward the distal end. Outer medullary shell three times as broad as the +inner, with polygonal meshes (of the same size as those in the spongy +framework) and fine bars. + +_Dimensions._--Diameter of the spongy shell 0.2, outer medullary shell +0.02, inner 0.007. + +_Habitat._--Mediterranean (Messina). + + +4. _Spongosphaera quadricuspis_, n. sp. + +Spongy shell spherical, with numerous curved, bristle-shaped by-spines on +the surface, half as long as the radius. Main spines twenty to thirty, +irregularly disposed, prismatic, with three dentated, spirally contorted +edges, and at the distal end four strong pyramidal divergent teeth (three +as terminations of the edges, the fourth as end of the spine axis). Outer +medullary shell twice as broad as the inner, both having circular, regular +pores, twice to three times as broad as the bars. + +_Dimensions._--Diameter of the spongy shell 0.3, outer medullary shell +0.04, inner 0.013. + +_Habitat._--Central Pacific, Station 272, surface. + + + +Genus 121. _Rhizosphaera_,[160] Haeckel, 1860, Monatsber. d. k. preuss. +Akad. d. Wiss. Berlin, p. 840. + +_Definition._--#Astrosphaerida# with two concentric latticed medullary +shells, connected by radial beams; from the outer arise numerous radial +spines, which at equal distances are connected by a latticed spherical +cortical shell, surrounded by a spongy framework. + +The genus _Rhizosphaera_ exhibits the same relation to _Spongosphaera_ that +_Rhizoplegma_ bears to _Spongopila_; but in the latter the latticed +medullary shell is simple, in the two former double. The wall of the +central capsule is pierced only by the radial spines connecting the +medullary and the cortical shells. + + +1. _Rhizosphaera trigonacantha_, Haeckel. + + _Rhizosphaera trigonacantha_, Haeckel, 1862, Monogr. d. Radiol., p. 452, + Taf. xxv. figs. 1-7. + +Central cavity of the spongy cortical shell twice as broad as the diameter +of the outer medullary shell. Bars of all three shells of the same breadth +as the thirty to fifty (or more) radial spines, {284}which are three-sided +prismatic; their outer free distal end only as long as the diameter of the +inner medullary shell. + +_Dimensions._--Diameter of the spongy shell 0.25, of its inner cavity 0.2, +outer medullary shell 0.1, inner 0.05. + +_Habitat._--Cosmopolitan; Mediterranean, Atlantic, Indian, Pacific, surface +from many Stations. + + +2. _Rhizosphaera serrata_, n. sp. (Pl. 18, figs. 5-7). + +Central cavity of the spongy shell five times as broad as the diameter of +the outer medullary shell. Bars of all three shells of the same breadth as +the forty to sixty (or more) thin radial beams between them. These are +three-sided prismatic, with denticulate edges, scarcely half as broad as +their outer prolongations, which are half as long as the shell radius, and +possess three spirally contorted serrated edges. (The figured specimen is a +young one; in the older specimens the spongy framework of the cortical +shell is much more developed.) + +_Dimensions._--Diameter of the spongy shell 0.3, of its central cavity +0.22, outer medullary shell 0.06, inner 0.02. + +_Habitat._--Central Pacific, Stations 270 to 274, surface. + + +3. _Rhizosphaera leptomita_, Haeckel. + + _Rhizosphaera leptomita_, Haeckel, 1862, Monogr. d. Radiol., p. 453, Taf. + xxv. figs. 8-10. + +Central cavity of the spongy cortical shell twice as broad as the diameter +of the outer medullary shell; bars of both very thin, only one-third as +broad as the bars of the inner medullary shell. Radial spines thirty to +fifty (or more), curved, three-sided prismatic; inside the spongy shell as +thin as their bars, outside three times as broad. + +_Dimensions._--Diameter of the spongy shell 0.27, of its inner cavity 0.2, +outer medullary shell 0.1, inner 0.05. + +_Habitat._--Mediterranean (Messina); Atlantic, Stations 348 to 354, +surface. + + +---- + + +Suborder PRUNOIDEA, Haeckel, 1883 (Pls. 13-17, 39, 40). + +_Definition._--SPUMELLARIA with an ellipsoidal or cylindrical central +capsule, prolonged into one axis (sometimes articulate by annular +transverse strictures); with an ellipsoidal or cylindrical, fenestrated +siliceous shell (often articulate by annular strictures), invariably +prolonged into one axis. Fundamental form monaxon, usually with the poles +of the prolonged dimensive main axis equal. + +The suborder #Prunoidea# comprises those SPUMELLARIA in which the +fenestrated spherical shell appears prolonged into one axis. The geometric +fundamental form of the shell, which in the #Sphaeroidea# was a sphere, in +this case therefore becomes an ellipsoid, and whilst in the former all axes +originally have the same value (Homaxonia), {285}here one main axis is +constantly larger than all other axes (Monaxonia). Usually both poles of +this main axis are equal (Haplopola); but in some genera both poles become +different (Diplopola). + +In the #Sphaeroidea# all planes going through the centre of the shell are +circular, whereas in the #Prunoidea# only those planes are circular which +are perpendicular to the main axis; all other planes going through the +centre are elliptical; the largest of these are the meridian planes, in +which is situated the main axis. Commonly all meridian planes are equal, as +no transverse axes (or cross axes) are differentiated. + +In my Monograph (1862) only very few forms of #Prunoidea#, such as +_Didymocyrtis_ and _Spongurus_, are described, and the greater part of them +are distributed under different genera of #Sphaeroidea#, such as _Haliomma_ +and _Actinomma_. In my Prodromus (1881) I separated them as the family +Zygartida (p. 462). But it seems now much more convenient to restrict this +term to a particular family and to give a wider extension to the whole +suborder under the name #Prunoidea# (called after the characteristic +ellipsoidal form of a plum, or _Prunus_, with its stone). + +The suborder #Prunoidea# comprises seven different families, of which the +Ellipsida constitutes the simplest and the probable common ancestral group. +In all Ellipsida the fenestrated shell is simple, and never composed of +concentric or twin shells. In their primitive genus _Cenellipsis_, the +whole shell is geometrically nothing more than a simple ellipsoid (Pl. 39, +figs. 1, 2). By development of radial spines it passes into _Ellipsidium_, +by development of spongy framework into _Spongellipsis_. In the greater +part of this family large spines are developed on both poles of the main +axis of the shell, but sometimes instead of these solid spines, two +opposite hollow fenestrated tubes are developed (_Pipettella_, Pl. 39, fig. +6). + +The second family of #Prunoidea#, the Druppulida, is much richer in +different forms than the simple Ellipsida. In this case the ellipsoidal +shell is composed of two or three (rarely more) concentric shells. +Constantly one or two of these fenestrated shells are enclosed in the +central capsule, and may therefore be called "medullary shells"; and one or +two (rarely more) lie outside the central capsule, "cortical shells." The +inner medullary shells (one or two) are either spherical or ellipsoidal; +the outer cortical shells (one or two, rarely more) are always ellipsoidal. +All concentric shells are connected by radial beams. In the simplest form +of the subfamily, _Druppula_ (Pl. 39, fig. 3), one medullary shell is +connected with one cortical shell. By duplication of the medullary shell +arises _Prunulum_ (Pl. 39, fig. 4), and by duplication or multiplication of +the cortical shell _Cromyodruppa_ (Pl. 15, figs. 1-4) is formed. In by far +the greater portion of this subfamily large spines are developed on both +poles of the main axis of the cortical shell (Pls. 16, 17), but sometimes +also instead of these solid spines two opposite hollow fenestrated tubes +are developed (_Pipetta_, Pl. 39, figs. 7, 8). + +{286}A third family of #Prunoidea#, closely allied to the two preceding +families, is the Spongurida, in which we include all #Prunoidea# with an +ellipsoidal or cylindrical, unjointed shell, in which the lattice-work of +the cortical shell is transformed into an irregular, siliceous framework. +In the simplest form, _Spongellipsis_, the simple lattice-shell of +_Cenellipsis_ is substituted by an external spongy envelope. In other cases +(_Spongurus_ and allied genera) the whole cavity of this external spongy +shell is distended with a fine spongy framework. The subfamily of +Spongodruppida is distinguished by the possession of a simple or double +latticed medullary shell; this lies in the midst of the central capsule, +and is connected by radial beams (perforating its membrane) with the +enveloping spongy cortical shell. The surface of the latter may bear either +radial spines, or two opposite strong polar spines, at the poles of the +main axis (Pl. 17, fig. 12). + +Closely allied to the Ellipsida and Druppulida are two other families of +the #Prunoidea#, the Artiscida and Cyphinida, which differ from the former +by a circular constriction in the equatorial plane of the ellipsoidal +shell; and in this way assume a characteristic twin form, like a figure of +eight. In the Artiscida the shell is simple (as in the Ellipsida), whereas +in the Cyphinida it is composed of two or more concentric shells (as in the +Druppulida). The simplest form of the Artiscida is _Artiscus_ (Pl. 39, fig. +9), differing from _Cenellipsis_ in the ring-shaped, equatorial +constriction. In other Artiscida polar appendages are developed on both +poles of the main axis, either in the form of solid, strong spines +(_Stylartus_), or hollow fenestrated tubes (_Cannartus_, Pl. 39, fig. 10). + +The family Cyphinida differs from the Druppulida in the equatorial +constriction of the shell, and from the Artiscida in the presence of two or +more concentric shells. One or two of these concentric fenestrated shells +are enclosed in the central capsule (and therefore may be called "medullary +shells"); the others (one or two, rarely more) lie outside of the central +capsule (therefore "cortical shells"). The internal "medullary shells" are +always spherical or somewhat lenticular, compressed from both sides; the +external "cortical shells" have constantly a ring-like constriction in the +equatorial plane, and "twin-shells" are therefore like a figure of eight. +The simplest form of this subfamily is _Cyphanta_, composed of a simple +medullary shell and a simple cortical shell, the two being connected in the +equatorial plane by radial beams. In Cyphonium (Pl. 39, fig. 12) the +medullary shell is doubled, and in _Cypassis_ (Pl. 39, fig. 13) the +cortical shell likewise. On both poles of the main axis strong spines are +often developed (_Cyphinus_, Pl. 39, fig. 14), or hollow fenestrated tubes +(_Cannartidium_, Pl. 39, figs. 16-19). + +The equatorial constriction of the ellipsoidal shell, which characterises +the Artiscida and Cyphinida, is repeated or multiplied in the two following +families, in the Panartida and Zygartida; in the former we find three +ring-like strictures, in the latter five or more (lying in parallel +transverse planes); therefore the fenestrated shell is composed in the one +instance of four chambers, in the other of six or {287}more; all the +chambers form a single series and have a common main axis. All +constrictions lie in planes parallel to the equatorial plane of the +original ellipsoid; in the centre of the latter constantly lies a double +"medullary shell," composed of two concentric, either spherical or +lenticular, compressed shells. In all Panartida we call the two inner +chambers (on both sides of the equatorial constriction) "proximal +chambers," the two outer chambers (on the poles of the main axis) "distal +chambers." The four-chambered cortical shell of the Panartida is either +simple (in _Panartus_, Pl. 40, figs. 1-4) or double, with an external +mantle (as in _Peripanartus_, Pl. 40, figs. 5-7). The simplest form of the +subfamily is _Panartus_ (_loc. cit._). In this case also on both poles of +the main axis may be developed solid spines, or hollow fenestrated tubes +(_Panarium_, Pl. 40, fig. 9). + +The seventh and last family of the #Prunoidea#, the Zygartida is most +nearly allied to the Panartida, and appears as a further developmental step +from that family. Whilst in the Panartida the cortical shell is constantly +four-chambered, with three parallel ring-like constrictions, in the +Zygartida it is always prolonged and composed of six or more chambers, +separated by five or more ring-shaped constrictions, in the middle of which +is the equatorial stricture. In the centre of the latter (as also in the +Panartida) always lies the double medullary shell, composed of two +concentric, spherical, or lenticular shells. The number of the chambers of +the cortical shells is commonly six or eight (with five to seven ring +strictures), but it often mounts to ten and sometimes to twenty (with +nineteen strictures), as in some species of _Zygartus_ (Pl. 40, fig. 13). +All the chambers lie in one series, one behind another, with a common main +axis. The cortical shell is usually simple (in _Ommatocampe_, Pl. 40, fig. +10), sometimes double (in _Desmocampe_, Pl. 40, fig. 12), rarely triple (in +ZYGOCAMPE, Pl. 40, fig. 13). In all three cases hollow fenestrated tubes +may be developed on the poles of the main axis. + +The morphological references and the phylogenetic affinities of all +#Prunoidea# are so complex, that they seem to represent a quite natural +group; all forms of it may be derived from the common ancestral form +_Cenellipsis_. But a far more difficult question is the manner in which its +pedigree may be constructed. The oldest family is probably the simplest, +namely, Ellipsida. From this the Druppulida may be derived by production of +medullary shells, the Artiscida by equatorial constriction. The Cyphinida +can be produced either from the Druppulida by equatorial constriction or +from the Artiscida by development of medullary shells. The Panartida appear +as further developmental steps of the Cyphinida, by duplication of the +chamber number; and the Zygartida as further productions of the Panartida, +by increasing the number of the chambers. + +The seven subfamilies of the #Prunoidea# can be arranged in two sections +according to the presence or absence of medullary shells. The Ellipsida, +Spongellipsida, and Artiscida possess a simple cortical shell, without a +medullary shell; they represent the {288}section Cenoprunida. All other +families possess medullary shells, and so represent the section +Coccoprunida. + +Another character, which can be employed in the arrangement of the seven +subfamilies in some larger groups, is the presence or absence of ring-like +constrictions, by which the cortical shell is divided into chambers. I. The +Monoprunida comprise all forms without any constriction, of which the +Ellipsida are without a medullary shell, the Druppulida with one or two +medullary shells, and the Spongurida with a spongy cortical shell. II. The +Dyoprunida contain all forms with a cortical twin shell, or with two +chambers separated by one equatorial constriction, of which the Artiscida +are without a medullary shell and the Cyphinida have one or two medullary +shells. III. The Polyprunida comprise all forms with several (three or +more) constrictions, which separate four or more chambers, of which the +Panartida have three constrictions and four chambers, and the Zygartida +five or more constrictions and six or more chambers. + +_The Central Capsule_ of the #Prunoidea# is originally ellipsoidal +(monaxial), and preserves this form in the greater part of the genera. In +some groups, where the axis of the ellipsoid is much prolonged, it passes +over to the cylindrical form (with hemispherical vaultings on both poles), +as in _Spongurus_ and _Spongocore_, in many Panartida and Zygartida. Very +often the ellipsoidal or cylindrical capsule gets annular transverse +constrictions, corresponding to those of the enveloping cortical shell (one +single, equatorial stricture in the Artiscida and Cyphinida, three +strictures in the Panartida, five or more in the Zygartida). In the +Cenoprunida (Ellipsida and Artiscida, also in _Spongellipsis_) the central +capsule lies freely in the cavity of the cortical shell, separated from its +inner surface by the jelly-envelope; in all other groups it contains a part +of the skeleton, the medullary shell and the beams which connect it with +the enveloping cortical shell. + +_Synopsis of the Families of_ #Prunoidea#. + + {a. Shell simple, latticed (not + { spongy), without enclosed internal + { enclosed internal shells, 1. ELLIPSIDA. + A. MONOPRUNIDA. { + {b. Shell composed of two or more + Shell without { concentric latticed shells + transverse stricture { (not spongy), 2. DRUPPULIDA. + { + {c. Shell partially or wholly + { composed of an irregular spongy + { framework, 3. SPONGURIDA. + + B. DYOPRUNIDA. { + {d. Shell simple, without enclosed + Shell bilocular, { internal shells, 4. ARTISCIDA. + divided by an { + equatorial stricture { + into two communicating{e. Shell composed of two or more + hemi-ellipsoidal { concentric shells, 5. CYPHINIDA. + shells. { + + C. POLYPRUNIDA. {f. Shell with three parallel + { strictures and therefore four + Shell multilocular, { camerae, 6. PANARTIDA. + divided by three { + or more parallel {g. Shell with five or more parallel + transverse strictures { strictures and therefore six + into four or more { or more camerae, 7. ZYGARTIDA. + serial camerae. { + + + +{289}Family XI. #ELLIPSIDA#, Haeckel, 1882 (Pls. 13, 14, 39). + +_Definition._--#Prunoidea# with simple ellipsoidal shell, without +equatorial stricture (without enclosed medullary shell); network a simple +lattice lamella, not spongy. Central capsule ellipsoidal or cylindrical, +without annular equatorial constriction. + +The family #Ellipsida# comprises the simplest forms of #Prunoidea#, and +probably represents the ancestral forms of this whole suborder. The +fenestrated shell, which encloses the ellipsoidal central capsule, is a +perfectly simple "cortical shell" of the same form, without enclosed +"medullary shell." Its form is commonly a regular monaxial ellipsoid; +sometimes a little modified by unequal growth of the two poles of the main +axis. Two opposite large spines are often developed at these poles, or it +may be that instead of these, two hollow fenestrated tubes are present. + +The ellipsoidal fenestrated shell exhibits in the regular Ellipsida all the +characters of a geometric ellipsoid; one main axis surpasses in length all +other possible axes. All sections going through this main axis are +"meridian sections," with elliptical periphery; all sections perpendicular +to the main axis are "transverse sections," with circular periphery. The +largest of these is the equatorial section, which divides the main axis +into halves. The diameter of this equatorial plane is the "minor axis" of +the ellipsoid. + +The proportion of the two axes of the ellipsoidal shell, of the major +vertical or main axis and the minor horizontal or equatorial axis, is +commonly between 6 : 5 and 3 : 2. In the former case it approaches the +spherical shell, from which it is derived; in the latter case it becomes +almost fusiform or cylindrical. The network of silex, constituting the +shell, is constantly a simple latticed lamella, never composed of +concentric shells (as in Druppulida) or spongy (as in Spongurida). The +network is often very regular and elegant, in other cases irregular. + +The simplest genus among the Ellipsida, and probably the common ancestral +form of the whole subfamily, is the genus _Cenellipsis_, possessing a +simple ellipsoidal shell without any appendages. It is derived from +_Cenosphaera_ (the simplest spherical shell) by the prolongation of one +axis. _Cenellipsis_ passes over into _Ellipsidium_ by the production of +radial spines on the surface (corresponding to _Heliosphaera_). +_Axellipsis_ is a peculiar genus differing from _Cenellipsis_ in an axial +rod, which corresponds to the minor or equatorial axis. In all other genera +of the subfamily both poles of the main axis are distinguished by peculiar +polar prolongations, either hollow fenestrated tubes (as in _Pipettella_) +or strong solid spines. Both polar spines are of equal size and similar +form in _Ellipsoxiphus_, unequal in _Ellipsostylus_. From the latter is +derived _Lithapium_, by reduction and loss of one spine (so that only one +remains); _Lithomespilus_, by production of a bunch of several spines at +one pole. In the three latter genera both poles of the main axis are +unequal, in all others equal. + +{290}The central capsule of the Ellipsida is in all cases ellipsoidal, and +occupies the largest part of the shell, being separated from its inner +surface by a thinner or thicker jelly-mantle. + +_Synopsis of the Genera of Ellipsida._ + + ------------------------------------------------------------------------- + Ellipsoidal shell without polar appendages (neither solid spines nor + hollow tubes at the poles of the axis). + ------------------------------------------------------------------------- + Surface without {Shell cavity + radial spines. { simple, without + { an axial rod, 122. _Cenellipsis_. + { + {Shell cavity + { with a transverse + { axial rod, 123. _Axellipsis_. + + Surface covered with radial spines, 124. _Ellipsidium_. + ------------------------------------------------------------------------- + Ellipsoidal shell with polar appendages (either solid spines or hollow + fenestrated tubes) at the poles of the main axis. + ------------------------------------------------------------------------- + Solid spines of {Shell cavity + similar shape, { simple, without + at both poles of { axial rods, 125. _Ellipsoxiphus_. + the main axis. { + {Shell cavity + { with a cross of + { axial rods, 126. _Axoprunum_. + + Solid spines of {Two polar spines + different shape, { of different + at both poles { shape, 127. _Ellipsostylus_. + of the main { + axis. {A bunch of spines + { at one pole + { only, 128. _Lithomespilus_ + { + {Only a single + { spine at one + { one pole, 129. _Lithapium_. + + Two hollow fenestrated tubes opposite, + at the poles of the main axis, 130. _Pipettella_. + + + +Genus 122. _Cenellipsis_,[161] n. gen. + +_Definition_.--#Ellipsida# with simple ellipsoidal shell, without radial +spines and without polar tubes. + +The genus _Cenellipsis_ is the simplest and most primitive form, not only +among the Ellipsida, but also among the #Prunoidea#, and it may therefore +be regarded as the common ancestral form of the whole family. It +corresponds to _Cenosphaera_ among the #Sphaeroidea#, to _Cenodiscus_ among +the #Discoidea#, to _Cenolarcus_ among the #Larcoidea#. Probably it is +derived from _Cenosphaera_ by prolongation of one axis. + + + +Subgenus 1. _Cenellipsium_, Haeckel. + +_Definition._--Network of the shell regular, with meshes of equal size and +similar form. + + +{291}1. _Cenellipsis primitiva_, n. sp. + +Proportion of the longer axis of the ellipsoid to the shorter = 3 : 2. +Network of the thin wall very delicate and regular, with hexagonal pores. +All pores of nearly the same size and form, ten to twelve times as broad as +the bars; nine to twelve on the half equator of the shell. Surface smooth. + +_Dimensions._--Longer axis of the ellipsoid 0.09 to 0.11, shorter axis 0.06 +to 0.08; pores 0.01, bars between them 0.001. + +_Habitat._--Pacific, central area, Station 272, surface. + + +2. _Cenellipsis faceta_, n. sp. (Pl. 39, fig. 1). + +Proportion of the longer axis of the ellipsoid to the shorter = 4 : 3. +Network of the thin wall delicate and regular. All the pores of the same +size and form, circular, with a hexagonal frame, twice to three times as +broad as the bars; eight to ten on the half equator. Surface smooth or +slightly spiny. + +_Dimensions._--Longer axis of the ellipsoid 0.12 to 0.13, shorter axis 0.09 +to 0.1; pores 0.013, bars 0.005. + +_Habitat._--Pacific, central area. Station 274, surface. + + +3. _Cenellipsis ehrenbergii_, Haeckel. + + _Haliomma (?) cenosphaera_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. + Wiss. Berlin, p. 74, Taf xxvi. fig. 5. + +Proportion of the longer axis to the shorter = 2 : 1. Network of the thin +wall regular or subregular. All pores circular, nearly of the same size, +without hexagonal frame, three to four times as broad as the bars; eight to +nine on the half equator. Surface covered with small thorns. + +_Dimensions._--Longer axis of the ellipsoid 0.16 to 0.2, shorter axis 0.08 +to 0.1; pores 0.1, bars 0.003. + +_Habitat._--Fossil in the Tertiary rocks of Barbados (Ehrenberg, Haeckel). + + +4. _Cenellipsis circopora_, n. sp. + +Proportion of the longer axis to the shorter = 5 : 3. Network of the thin +wall delicate and regular. All pores circular, nearly of the same size, +without hexagonal frame, twice as broad as the bars; fifteen to twenty on +the half equator. Surface quite smooth. + +_Dimensions._--Longer axis of the ellipsoid 0.15 to 0.2, shorter axis 0.09 +to 0.12; pores 0.08, bars 0.4. + +_Habitat._--North Pacific, Station 236, surface. + + +5. _Cenellipsis micropora_, n. sp. + +Proportion of the longer axis to the shorter = 5 : 4. Network of the thick +wall quite regular. All pores circular, without hexagonal frame, very +small, scarcely half as broad as the bars; six to eight on the half +equator. Surface quite smooth. + +{292}_Dimensions._--Longer axis of the ellipsoid 0.1, shorter axis 0.08; +pores 0.004, bars 0.01. + +_Habitat._--South Pacific, Station 289, surface. + + + +Subgenus 2. _Cenellipsula_, Haeckel. + +_Definition._--Network of the shell irregular, with meshes of different +size or form. + + +6. _Cenellipsis heteropora_, n. sp. + +Proportion of the longer axis to the shorter = 3 : 2 or = 5 : 3. Network of +the thin wall very irregular, with polygonal meshes of different size and +form (for the most part pentagonal or hexagonal, but also many tetragonal +or heptagonal). The largest pores four to six times as broad as the +smallest; ten to twenty pores on the half equator; bars between them thin. +Surface smooth or somewhat spiny. + +_Dimensions._--Longer axis of the ellipsoid 0.18 to 0.22, shorter axis 0.1 +to 0.12; pores 0.004 to 0.008, bars 0.001. + +_Habitat._--Indian Ocean, near the Cocos Islands, surface, Rabbe. + + +7. _Cenellipsis maxima_, n. sp. + +Proportion of the longer axis to the shorter = 3 : 2. Network of the thin +wall very irregular, with polygonal meshes of very different size and form, +twice to eight times as broad as the bars; fifty to sixty on the half +equator. Surface smooth. + +_Dimensions._--Longer axis of the ellipsoid 0.36, shorter axis 0.25; pores +0.004 to 0.015, bars 0.002. + +_Habitat._--Equatorial Atlantic, Station 347, surface. + + +8. _Cenellipsis ovulum_, n. sp. + +Proportion of the longer axis to the shorter = 3 : 2. Network of the thin +wall very irregular, with roundish or longish pores of very different size +and form. Pores flat, with even margins, thirty to forty on the half +equator, twice to six times as broad as the bars. Surface smooth. (This +species being observed alive, showed a transparent central capsule of +ellipsoidal form, two-thirds as large as the shell.) + +_Dimensions._--Longer axis of the ellipsoid 0.3, shorter axis 0.2; pores +0.04 to 0.012, bars 0.002. + +_Habitat._--Indian Ocean, Ceylon, Haeckel; Pacific, central area, Station +266, surface. + + +9. _Cenellipsis infundibulum_, n. sp. (Pl. 39, fig. 2). + +Proportion of the longer axis to the shorter = 3 : 2. Network of the thick +wall irregular, with roundish pores of different size and form. Pores +funnel-like, with prominent, irregular, spiny {293}crests between them, +their outer aperture three to four times as broad as the inner; twelve to +fifteen pores on the half equator. Surface prickly. + +_Dimensions._--Longer axis of the ellipsoid 0.14, shorter axis 0.11; outer +aperture of the pores 0.01 to 0.012, inner aperture 0.003 to 0.004. + +_Habitat._--South Atlantic, Station 332, depth 2200 fathoms. + + +10. _Cenellipsis oblonga_, n. sp. + +Proportion of the longer axis to the shorter = 2 : 1. Network of the thick +wall irregular, with roundish pores of different size and form. Pores with +prominent conical edges, about as broad as the bars; twenty to twenty-five +on the half equator. Sometimes each pore is prolonged into a short conical +tubulus. + +_Dimensions._--Longer axis of the ellipsoid 0.22, shorter axis 0.12; pores +and bars 0.008 to 0.012. + +_Habitat._--Pacific, central area, Station 265, depth 2900 fathoms. + + + +Genus 123. _Axellipsis_,[162] n. gen. + +_Definition._--#Ellipsida# with simple ellipsoidal shell, without radial +spines or polar tubes, but with an inner transverse axial rod, which +corresponds to the shorter axis of the ellipsoid. + +The genus _Axellipsis_ differs from the simple _Cenellipsis_ in a very +peculiar character, namely, the presence of an inner siliceous bar marking +the minor axis of the ellipsoidal shell. If in some forms of _Druppula_ +(e.g., Pl. 39, fig. 3) we remove the central medullary shell and prolong +both beams (connecting it with the cortical shell) till they unite in the +centre, we shall arrive at _Axellipsis_. Therefore _Axellipsis_ may be +derived in the same way from _Druppula_ as _Axoprunum_ is from +_Lithatractus_, by phyletic loss of the medullary shell. + + +1. _Axellipsis perforata_, n. sp. + +Proportion of the major axis of the ellipsoid to the minor = 3 : 2. Pores +of the shell regular, circular, twice as broad as the bars; ten to twelve +on the half equator. Surface smooth. + +_Dimensions._--Longer axis of the shell 0.12, shorter axis 0.08; pores +0.006, bars 0.003. + +_Habitat._--Central area of the Pacific, Station 266, depth 2750 fathoms. + + +2. _Axellipsis lobata_, n. sp. + +Proportion of the major axis to the minor = 5 : 4. Meshes of the shell +irregular, roundish, lobed, with three to six indentations (each mesh +formed by the confluence of three to six, commonly {294}four or five, +smaller pores); eight to nine meshes on the half equator, these being twice +to four times as broad as the bars. + +_Dimensions._--Longer axis of the shell 0.1, shorter axis 0.08; pores 0.007 +to 0.01, bars 0.003. + +_Habitat._--Tropical zone of the Western Pacific, Station 225, surface. + + + +Genus 124. _Ellipsidium_,[163] n. gen. + +_Definition._--#Ellipsida# with simple ellipsoidal shell, with numerous +radial spines on the surface, without polar spines or tubes. + +The genus _Ellipsidium_ differs from _Cenellipsis_ solely in the +development of numerous radial spines on the surface, and exhibits the same +phylogenetic relation to it that _Heliosphaera_ bears to _Cenosphaera_. + + +1. _Ellipsidium pandanidium_, n. sp. + +Proportion of the longer axis of the ellipsoid to the shorter = 5 : 4. +Shell thick walled, with regular and hexagonal meshes, twice as broad as +the bars; eighteen to twenty on the half equator. In each hexagon-corner +(between three pores) arises a short, three-sided pyramidal spine, half as +long as the equatorial radius, and as thick at the base as a single mesh. + +_Dimensions._--Major axis of the ellipsoid 0.15, minor 0.12; pores 0.006, +bars 0.003; length of the radial spines 0.03, basal breadth 0.006. + +_Habitat._--Fossil in the Tertiary rocks of Barbados (Haeckel). + + +2. _Ellipsidium datura_, n. sp. + +Proportion of the longer axis of the ellipsoid to the shorter = 4 : 3. +Shell thick walled, with regular, circular meshes, twice as broad as the +thick bars between them eight to ten meshes on the half equator. Outer +surface of the shell thorny, covered with short, conical, radial spines, +which are regularly distributed (one spine between every three meshes), and +about as long as the diameter of the meshes. (The shell is similar to the +outer shell of _Haliomma castanea_, Haeckel, Monogr. d. Radiol., Taf. xxiv. +fig. 4.) + +_Dimensions._--Major axis of the ellipsoid 0.12, minor axis 0.09; meshes +0.012, bars 0.006. + +_Habitat._--Western part of the Tropical Pacific, Station 225, depth 4475 +fathoms. + + +3. _Ellipsidium artocarpus_, n. sp. + +Proportion of the longer axis to the shorter = 3 : 2. Shell thick walled, +with regular, circular meshes, separated by deep furrows, which represent a +regular, hexagonal framework; on the half equator twelve to fifteen meshes, +scarcely broader than the broad bars between them. Outer {295}surface +spiny; between every three meshes arises a strong radial spine, twice to +three times as long as the diameter of the meshes; the base of the spine is +like a three-sided pyramid. + +_Dimensions._--Major axis of the ellipsoid 0.12, minor axis 0.08; meshes +0.006, bars 0.005. + +_Habitat._--Central area of the Pacific, Station 268, depth 2900 fathoms. + + +4. _Ellipsidium opuntia_, n. sp. + +Proportion of the longer axis to the shorter = 5 : 4. Shell thin walled, +with irregular, roundish meshes of different size and form, about twice to +three times as broad as the irregular, thin bars between them; ten to +fifteen meshes on the half equator. Between the meshes arise numerous thin, +bristle-like, radial spines, about as long as the shorter radius of the +shell. The number of the meshes may be three to four times as great as the +number of the spines. + +_Dimensions._--Major axis of the ellipsoid 0.15, minor axis 0.12; pores +0.006 to 0.01, bars 0.003 to 0.004. + +_Habitat._--Southern Pacific, Station 284, surface. + + +5. _Ellipsidium echinidium_, n. sp. + +Proportion of the longer axis to the shorter = 4 : 3. Shell thick walled, +with irregular, roundish pores of different size and form, about as large +or somewhat smaller than the broad bars; twelve to sixteen pores on the +half equator. On the surface, irregularly scattered, twenty to thirty +strong, three-sided pyramidal, radial spines, one-fourth to one-half as +long as the main axis. + +_Dimensions._--Major axis of the ellipsoid 0.16, minor 0.12; pores and bars +0.002 to 0.008; length of the radial spines 0.04 to 0.08, basal breadth +0.01. + +_Habitat._--Equatorial Atlantic, Station 347, depth 2250 fathoms. + + + +Genus 125. _Ellipsoxiphus_,[164] Dunikowski, 1882, Denkschr. d. k. Akad. d. +Wiss. Wien, vol. xlv. p. 25. + +_Definition._--#Ellipsida# with simple ellipsoidal shell, the main axis of +which is prolonged at both poles into two strong opposite spines of equal +size and similar form. + +The genus _Ellipsoxiphus_ was established by Dunikowski (in 1882, _loc. +cit._) for those simple amphistylous fenestrated shells, formerly united +with _Xiphosphaera_, in which the mathematical form of the shell itself is +not a true sphere, but an ellipsoid. It may therefore be derived from +_Xiphosphaera_ by prolongation of the axis in which lie both polar spines; +but it may also be derived from _Cenellipsis_ by the production of two +equal spines at the poles of the main axis. + + + +{296}Subgenus 1. _Ellipsoxiphetta_, Haeckel. + +_Definition._--Network of the shell regular, with pores of equal size and +similar form. + + +1. _Ellipsoxiphus elegans_, n. sp. (Pl. 14, fig. 7). + +Proportion of the major axis of the ellipsoid to the minor = 5 : 4. Shell +thick walled, with regular, circular meshes, separated by a regular, +hexagonal elevated framework. From each hexagon-corner arises (between +every three meshes) a short thin spine, about as long as the diameter of a +mesh; twelve to fourteen meshes on the half equator, of the same breadth as +the bars. Polar spines three-sided prismatic, cuspidate, about as long as +the axis of the shell. (This elegant and not uncommon species is remarkable +for its variations. By unequal development of both spines it passes over to +_Ellipsostylus_.) In the figured variety (Pl. 14, fig. 7) the ends of the +surface spines are connected by a very delicate network, so as to form an +outer veil. This may further be separated as a peculiar genus +_Ellipsoxiphium palliatum_. + +_Dimensions._--Longer axis 0.08 to 0.13, shorter axis 0.06 to 0.11; pores +and bars 0.008; length of the polar spines 0.06 to 0.12, basal breadth +0.01. + +_Habitat._--Pacific, central area, Stations 270 to 274, from 2350 to 2925 +fathoms. + + +2. _Ellipsoxiphus flosculus_, n. sp. + +Proportion of the major axis to the minor = 6 : 5. Shell very thick walled, +with regular, hexagonal meshes, eight to nine on the half equator, three to +four times as broad as the bars. The inner contour of the meshes is +circular, the outer six-lobed (similar to _Xiphostylus phasianus_, Pl. 13, +fig. 9). Polar spines three-sided pyramidal, about as long as the major +axis of the shell; their basal thickness equals one mesh. + +_Dimensions._--Longer axis 0.12, shorter axis 0.1; pores 0.012 to 0.015, +bars 0.004; length of the polar spines 0.12 to 0.15, basal breadth 0.015. + +_Habitat._--Fossil in the Tertiary rocks of Barbados (Teuscher). + + +3. _Ellipsoxiphus fragilis_, n. sp. + +Proportion of the major axis to the minor = 4 : 3. Shell thin walled, with +regular, circular meshes, twice as broad as the bars; ten to twelve on the +half equator. Surface smooth. Polar spines cylindrical, at the apex +conical, half as long as the major axis. + +_Dimensions._--Longer axis 0.16, shorter axis 0.12; pores 0.008, bars +0.004; length of the polar spines 0.09, basal breadth 0.008. + +_Habitat._--South Atlantic, Station 325, surface. + + + +Subgenus 2. _Ellipsoxiphilla_, Haeckel. + +_Definition._--Network of the shell irregular, with pores of different size +or form. + + +{297}4. _Ellipsoxiphus claviger_, n. sp. (Pl. 14, fig. 3). + + _Xiphosphaera clavigera_, Haeckel, 1881, Prodromus et Atlas. + +Proportion of the major axis to the minor = 5 : 4. Shell thick walled, with +irregular network; meshes roundish or circular, double contoured, of +unequal size, twice to four times as broad as the bars; eight to ten on the +half equator. Polar spines club-shaped, with prominent edges, about as long +as the minor axis; thicker in their middle part than at both ends (differs +from _Xiphosphaera clavigera_ by the ellipsoidal form of the shell, and the +double length of the spines). + +_Dimensions._--Longer axis 0.15. shorter axis 0.12; pores 0.007 to 0.015, +bars 0.004; length of the polar spines 0.12, thickness in the middle part +0.02. + +_Habitat._--Central area of the Pacific, Station 272, depth 2600 fathoms. + + +5. _Ellipsoxiphus suessi_, Dunikowski. + + _Ellipsoxiphus suessi_, Dunikowski, 1882, Denkschr. d. k. Akad. d. Wiss. + Wien, Bd. xlv. p. 26, Taf. v. fig. 50. + +Proportion of the major axis to the minor = 7 : 5. Shell thick walled, with +irregular, roundish meshes, six to eight on the half equator, twice to +three times as broad as the bars. Polar spines nearly cylindrical, blunt, +as long as the major axis. + +_Dimensions._--Longer axis 0.14; shorter axis 0.1; pores 0.018 to 0.023, +bars 0.01; length of the polar spines 0.12; thickness of them 0.035. + +_Habitat._--Fossil in the Alpine Lias, Schafberg near Salzburg, Dunikowski. + + +6. _Ellipsoxiphus parvoforaminus_, Dunikowski. + + _Ellipsoxiphus parvoforaminus_, Dunikowski, 1882, Denkschr. d. k. Akad. + d. Wiss. Wien, Bd. xlv. p. 26, Taf. v. fig. 51. + +Proportion of the major axis to the minor = 7 : 6. Shell thick walled, +with irregular, roundish or oval meshes, ten to twelve on the half equator, +scarcely as broad as the bars. Polar spines conical, shorter than the +minor axis. + +_Dimensions._--Longer axis 0.14, shorter axis 0.12; pores 0.016 to 0.01, +bars 0.01 to 0.02; length of the polar spines 0.1, basal thickness 0.045. + +_Habitat._--Fossil in the Alpine Lias, Schafberg near Salzburg, Dunikowski. + + +7. _Ellipsoxiphus bipolaris_, n. sp. (Pl. 14, fig. 11). + + _Xiphosphaera bipolaris_, 1881, Prodromus et Atlas. + +Proportion of the major axis to the minor = 8 : 7. Shell thick walled, +with irregular, roundish meshes, twice to three times as broad as the bars; +sixteen to twenty on the half equator. Polar spines short and thick, +three-sided pyramidal, scarcely half as long as the shorter radius of the +shell; surrounding the base of every spine is a circle of eight to nine +shorter spines. + +_Dimensions._--Longer axis 0.08, shorter axis 0.07; pores 0.003 to 0.007, +bars 0.002; length of the polar spines 0.02 to 0.03, basal thickness 0.02. + +_Habitat._--Tropical part of the Western Pacific, Station 225, depth 4475 +fathoms. + + +{298}8. _Ellipsoxiphus atractus_, n. sp. (Pl. 14, fig. 1). + +Proportion of the major axis to the minor = 3 : 2. Shell spindle-shaped, +very thick walled, with roundish, very irregular meshes, twice to five +times as broad as the bars; eight to twelve on the half equator. The meshes +are partly simple, oblong, partly lobed or composed of two to four +(commonly three) confluent meshes. Surface smooth. Polar spines very short +and thick, shorter than the minor radius of the shell, three-sided +pyramidal, with prominent, somewhat contorted edges. + +_Dimensions._--Longer axis 0.15, shorter axis 0.1; meshes 0.007 to 0.02, +bars 0.004; length of the polar spines 0.04, basal thickness 0.03. + +_Habitat._--Central area of the Pacific, Station 268, depth 2900 fathoms. + + + +Genus 126. _Axoprunum_,[165] n. gen. + +_Definition._--#Ellipsida# with simple ellipsoidal shell, the main axis of +which is prolonged at both poles into two opposite spines of equal size and +similar form. Within the cavity of the shell four radial rods arise from +its inner surface, two in the main axis, two in the smallest axis, +perpendicular to the former; their free inner ends are at the same distance +from the centre. + +The genus _Axoprunum_ possesses precisely the same shell as the foregoing +_Ellipsoxiphus_, but differs from it in a very remarkable peculiarity. The +two polar spines are centripetally prolonged into two internal beams, and +perpendicular to these are two other, opposite, transverse beams, marking +the minor axis of the ellipsoid. The free inner ends of all four radial +rods bear little thickened knobs, and are at the same distance from the +centre. It therefore appears as though a central, spherical, medullary +shell had been lost, and this gives a strong support to the important +hypothesis, that in many #Sphaerellaria#, where the medullary shell is +absent, it may have been lost by phylogenetic reduction or retrograde +metamorphosis. In this case _Axoprunum_ (and _Ellipsoxiphus_) would arise +from _Lithatractus_. + + +1. _Axoprunum stauraxonium_, n. sp. (Pl. 48, fig. 4). + +Shell ellipsoidal, one and one-third times as long as broad, with smooth +surface. Network regular, with circular meshes four times as broad as the +bars. Two polar spines three-sided pyramidal, half as long as the shell, as +thick at the base as a single mesh. Four inner radial beams (lying, two in +the major and two in the minor axis of the ellipsoid) very thin, at the +central free ends knob-like, thickened. The distance between two opposite +beams equals one-third of the minor axis, and indicates probably the +diameter of the lost spherical medullary shell. (Three perfect and complete +specimens of the same size and shape were observed.) + +{299}_Dimensions._--Major axis of the ellipsoid 0.14, minor axis 0.11; +pores 0.012, bars 0.003; length of the polar spines 0.07, basal breadth +0.012. (Diameter of the lost medullary shell 0.03?) + +_Habitat._--South Atlantic, Station 338, depth 1990 fathoms. + + + +Genus 127. _Ellipsostylus_,[166] n. gen. + +_Definition._--#Ellipsida# with simple ellipsoidal shell, the main axis of +which is prolonged at both poles into two opposite spines of different size +or form. + +The genus _Ellipsostylus_ differs from _Ellipsoxiphus_ only in the unequal +size or different form of the polar spines, which in the former are equal. +This difference does not seem important at first, but in the further +development it produces very singular and strange forms. Theoretically it +is always important, because the fundamental haplopolar form of the monaxon +body becomes diplopolar by this differentiation. + + + +Subgenus 1. _Ellipsostyletta_, Haeckel. + +_Definition._--Network of the shell regular, with pores of equal size and +similar form. + + +1. _Ellipsostylus ornithoides_, n. sp. + +Proportion of the major axis of the ellipsoid to the minor = 4 : 3. Shell +thin walled, with regular, circular meshes and hexagonal framework between +them, like that of _Xiphostylus favosus_ (Pl. 13, fig. 4). Circular pores +about as broad as the bars; eight to nine on the half equator. Surface +smooth. Polar spines three-sided pyramidal, as broad at the base as a +single hexagon; the longer spine as long as the major axis, the shorter +half as long. + +_Dimensions._--Longer axis of the ellipsoidal shell 0.16, shorter axis +0.12; pores and bars 0.006; length of the longer polar spine 0.16, of the +shorter 0.08. + +_Habitat._--North Pacific, Station 241, depth 2300 fathoms. + + +2. _Ellipsostylus avicularis_, n. sp. + +Proportion of the major axis to the minor = 3 : 2. Shell thick walled, with +regular, rosette-shaped meshes, three times as broad as the bars; ten to +twelve on the half equator. Every mesh on the outer margin with five to six +rounded lobes, as in _Xiphostylus phasianus_ (Pl. 13, fig. 9). Surface +smooth. Polar spines sharp edged, thick; the longer straight and equal to +the longer axis, the shorter half as long, shaped like a bird's head. + +_Dimensions._--Longer axis 0.18, shorter axis 0.12; pores 0.015, bars +0.005. + +_Habitat._--South Pacific, Station 300, depth 1375 fathoms. + + +{300}3. _Ellipsostylus psittacus_, n. sp. (Pl. 13, fig. 6). + +Proportion of the major axis to the minor = 4 : 3. Shell thin walled, with +regular or subregular rosette-shaped meshes, twice as broad as the bars; +eight to nine on the half equator; each mesh with three to four rounded +lobes. Surface smooth. Polar spines sharp edged, very unequal; longer spine +about twice as long as the major axis, somewhat curved; shorter spine +scarcely longer than the radius, shaped like a bird's head. + +_Dimensions._--Longer axis 0.08, shorter axis 0.06; pores 0.01, bars 0.005; +length of the polar spines--longer 0.15, shorter 0.05. + +_Habitat._--Central area of the Pacific, Station 266, depth 2750 fathoms. + + +4. _Ellipsostylus aquila_, n. sp. (Pl. 13, fig. 1). + +Proportion of the major axis to the minor = 7 : 6. Shell thick walled, with +subregular, circular meshes, five to six times as broad as the bars; ten to +twelve on the half equator. Surface smooth. Polar spines sharp edged +(six-sided?), very unequal; longer spine straight, about equal to the minor +axis; shorter spine obliquely inserted, scarcely half as long, shaped like +a bird's head. + +_Dimensions._--Longer axis 0.15, shorter axis 0.13; pores 0.02, bars 0.004; +length of the polar spines--longer 0.1, shorter 0.05. + +_Habitat._--Central area of the Pacific, Station 272, depth 2600 fathoms. + + +5. _Ellipsostylus columba_, n. sp. (Pl. 13, fig. 3). + +Proportion of the major axis to the minor = 4 : 3. Shell egg-shaped, thin +walled, with regular, circular meshes, three times as broad as the bars; +ten to twelve on the half equator. Surface somewhat thorny. Polar spines +nearly of equal length (equal to the major axis), but of very different +form; one straight, pyramidal, and obliquely inserted, the other like a +bird's head. + +_Dimensions._--Longer axis 0.08, shorter 0.06; pores 0.003, bars 0.01; +length of the spines 0.09. + +_Habitat._--South Atlantic, Station 332, surface. + + +6. _Ellipsostylus ciconia_, n. sp. (Pl. 13, fig. 8). + +Proportion of the major axis to the minor = 7 : 5. Shell egg-shaped, thick +walled; the meshes very small, regular, circular, three times as broad as +the bars; sixteen to twenty on the half equator. Surface uneven. Polar +spines nearly cylindrical, pointed; the smaller obliquely inserted, equal +to the major axis; the larger more than twice as long and thick, furrowed +at its base. (Compare with this and the allied species _Rhabdolithis pipa_, +Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, Taf. i. fig. 27.) + +_Dimensions._--Longer axis 0.07, shorter 0.05; pores 0.003, bars 0.001; +length of the polar spines--longer 0.2, shorter 0.08. + +_Habitat._--North Pacific, Station 253, depth 3125 fathoms. + + + +{301}Subgenus 2. _Ellipsostylissa_, Haeckel. + +_Definition._--Network of the shell irregular, with pores of different size +or form. + + +7. _Ellipsostylus megadictya_, Haeckel. + + _Stylosphaera megadictya_, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. + Berlin, p. 299, Taf. viii. fig. 13. + +Proportion of the major axis to the minor = 5 : 4. Shell thin walled, with +irregular, roundish, large meshes, four to five times as broad as the bars; +only four to five on the half equator. Surface smooth. Polar spines +straight, thin, angular; the shorter equal to the minor axis, the longer +four times as large. + +_Dimensions._--Longer axis 0.05, shorter axis 0.04; meshes 0.01, bars +0.002; length of the polar spines--longer 0.12, shorter 0.03. + +_Habitat._--Philippine Sea, 3300 fathoms, Ehrenberg. + + +8. _Ellipsostylus gallinula_, n. sp. + +Proportion of the major axis to the minor = 3 : 2. Shell thick walled, with +irregular, roundish meshes, twice to four times as broad as the bars; eight +to ten on the half equator. Surface thorny. Polar spines conical, straight; +the longer twice as long as the major axis, the minor scarcely half as +long. + +_Dimensions._--Longer axis 0.15, shorter 0.12; pores 0.01 to 0.02, bars +0.002 to 0.004. + +_Habitat._--North Pacific, Station 253, surface. + + +9. _Ellipsostylus hirundo_, n. sp. (Pl. 13, fig. 2). + +Proportion of the major axis to the minor = 4 : 3. Shell thick walled, with +irregular, roundish meshes, three to five times as broad as the bars; eight +to ten on the half equator. The inner aperture of every mesh is fenestrated +by a delicate lamella of silex, perforated by six to eight very small +circular pores. Polar spines sharp edged, more or less curved, the shorter +equal to the minor axis, the longer twice as long. + +_Dimensions._--Longer axis 0.16, shorter 0.12; pores 0.01 to 0.02, bars +0.003 to 0.006; length of the polar spines--longer 0.24, shorter 0.12. + +_Habitat._--Pacific, central area, Station 268, depth 2900 fathoms; the +same form also fossil in the rocks of Barbados. + + + +Genus 128. _Lithomespilus_,[167] Haeckel, 1881, Prodromus, p. 450. + +_Definition._--#Ellipsida# with simple ellipsoidal or oviform shell, the +main axis of which bears at one pole a single spine, at the other a bunch +of several spines. + +{302}The genus _Lithomespilus_ differs from the closely allied +_Ellipsoxiphus_ in the further differentiation of both poles of the main +axis. One pole exhibits only a single polar spine, the other pole a group +of several spines, peculiarly grouped together. It differs from the similar +_Sphaeromespilus_ (Pl. 14, figs. 12, 13) in the ellipsoidal form of the +shell. + + +1. _Lithomespilus phloginus_, n. sp. (Pl. 14, fig. 16). + +Proportion of the major axis of the ellipsoid to the minor = 4 : 3. Shell +thick walled, with circular pores of different size, the breadth of which +equals that of the bars; twelve to fifteen pores on the half equator. +Surface smooth, with the exception of a circumpolar region covered with +numerous thick spines of unequal size, which surround the large single +polar spine and are curved like a bow against its axis. This larger polar +spine is straight, and equals in length the major axis of the shell. The +other and opposite polar spine is scarcely one-fourth as long, perfectly +simple, very stout, and of a three-sided pyramidal shape. + +_Dimensions._--Longer axis of the ellipsoidal shell 0.08, shorter axis +0.06; pores 0.002 to 0.006, bars 0.003 to 0.005; length of the polar +spines--longer 0.08, shorter 0.02. + +_Habitat._--Indian Ocean, near Madagascar, depth 1200 fathoms, Smith. + + +2. _Lithomespilus phlogoides_, n. sp. (Pl. 14, fig. 17). + +Proportion of the major axis to the minor = 5 : 4. Shell very thick walled, +with roundish, double-contoured pores of different size and form, twice to +three times as broad as the bars; sixteen to eighteen pores on the half +equator. Surface smooth, with the exception of a circumpolar region covered +with numerous thin spines of unequal size, which surround the large single +polar spine and are curved like a bow against its axis. This larger polar +spine is straight, and equals half the size of the major axis of the shell; +the other polar spine (sometimes double, as in the figured specimen) is +much shorter, being scarcely one-fourth as long. + +_Dimensions._--Longer axis of the shell 0.08, shorter axis 0.065; pores +0.003 to 0.006, bars 0.002 to 0.004; length of the polar spines--longer +0.04, shorter 0.01. + +_Habitat._--Central area of the Pacific, Stations 270 to 272, depth 2425 to +2925 fathoms. + + +3. _Lithomespilus flammeus_, n. sp. + + _Stylosphaera species_, Bury, 1862, Polycystins of Barbados, pl. xi. fig. + 3. + +Proportion of the major axis to the minor = 4 : 3. Shell thick walled, with +irregular, roundish pores, about as broad as the bars; ten to twelve pores +on the half equator. Surface spiny. Length of the conical straight spines +increasing towards the poles; each polar spine surrounded by a circumpolar +group of larger, somewhat curved spines. The larger polar spine equals in +length the major axis; the smaller is scarcely half as long. (The figure, +given by Bury, is not quite exact; there the spines are situated in the +pores, instead of between them. In my specimen the polar spines were not +branched.) + +{303}_Dimensions._--Longer axis of the shell 0.12, shorter axis 0.09; pores +and bars 0.004 to 0.006; length of the polar spines--longer 0.12, shorter +0.06. + +_Habitat._--Fossil in Barbados. + + +4. _Lithomespilus flammabundus_, n. sp. (Pl. 14, fig. 14). + +Proportion of the major axis to the minor = 4 : 3. Shell thin walled, with +irregular, roundish pores, partly simple, partly composed of three to six +confluent pores; only six to eight pores on the half equator, twice to four +times as broad as the bars. Surface spiny. Length of the conical irregular +spines increasing towards the poles; each polar spine surrounded by a +flame-shaped, circumpolar area of longer spines; all large spines (also the +polar spines) curved or contorted at one pole and much stronger and more +numerous than at the other; length variable, often equal to the longer +axis. + +_Dimensions._--Longer axis of the shell 0.12, shorter axis 0.09; pores +0.005 to 0.015, bars 0.003 to 0.005; length of the polar spines 0.1 to +0.15. + +_Habitat._--Western part of the Tropical Atlantic, Station 347, depth 2250 +fathoms. + + + +Genus 129. _Lithapium_,[168] n. gen. + +_Definition._--#Ellipsida# with simple ellipsoidal or pear-shaped shell; +with a single spine only situated at one pole of the main axis. + +The genus _Lithapium_ represents a peculiar modification of +_Ellipsoxiphus_; one of the two opposite polar spines disappears by +reduction, and in this way only a single spine remains, at one pole of the +main axis. For this reason the shell assumes a characteristic pear-shape, +and may easily be confounded with some similar Monocyrtida (_Halicapsa_). + + +1. _Lithapium pyriforme_, n. sp. (Pl. 14, fig. 9). + +Proportion of the longer axis to the shorter = 6 : 5. Shell thin walled, +with regular, circular pores, four times as broad as the bars; six to eight +on the half equator. Surface a little thorny. The single polar spines +three-sided pyramidal, as broad at the base as one mesh, about as long as +the radius of the shell. (In the specimen figured, there was on the +opposite pole a little rudiment of the other lost polar spine; it is +missing in other specimens.) + +_Dimensions._--Major axis of the ellipsoidal shell 0.12, minor axis 0.1; +pores 0.02, bars 0.005; length of the single polar spine 0.05, basal +thickness 0.02. + +_Habitat._--Central area of the Pacific, Station 266, depth 2750 fathoms. + + +2. _Lithapium halicapsa_, n. sp. (Pl. 14, fig. 8). + +Proportion of the longer axis to the shorter = 6 : 5. Shell thin walled, +with irregular, lobed meshes, six to eight on the half equator, twice to +five times as broad as the bars; each mesh {304}composed of two to five +confluent roundish pores. Surface a little thorny. The single polar spine +pyramidal, as broad at the base as one mesh, one-third as long as the axis. + +_Dimensions._--Major axis 0.12, minor axis 0.1; pores 0.01 to 0.02, bars +0.002 to 0.006; length of the single polar spine 0.03, basal thickness +0.02. + +_Habitat._--Central area of the Pacific, Station 270, depth 2925 fathoms. + + +3. _Lithapium monocyrtis_, n. sp. (Pl. 14, fig. 10). + +Proportion of the longer axis to the shorter = 7 : 6. Shell thick walled, +with irregular, lobed meshes, four to six on the half equator, three to six +times as broad as the bars; each mesh composed of three to six confluent +roundish pores. Surface quite smooth, without thorns. The single polar +spine pyramidal, as broad at the base as the largest mesh, half as long as +the radius. (This species is closely allied to the foregoing, but differs +in the smooth surface and the larger meshes.) + +_Dimensions._--Major axis 0.15, minor axis 0.13; pores 0.01 to 0.03, bars +0.003 to 0.01; length of the single spine 0.04, basal thickness 0.03. + +_Habitat._--Central area of the Pacific, Station 268, depth 2900 fathoms. + + + +Genus 130. _Pipettella_,[169] n. gen. + +_Definition._--#Ellipsida# with simple ellipsoidal shell, the main axis of +which is prolonged at the pole into two opposite hollow fenestrated tubes +of equal size and similar form. + +The genus _Pipettella_ is distinguished from the other Ellipsida by two +hollow perforated tubes, which are directed in the longer axis of the +ellipsoidal shell and arise from opposite poles of this axis. It may be +derived from _Cenellipsis_ by prolongation of both poles of the main axis. +As the same peculiar production of two opposite latticed tubuli at the +poles of the main axis obtains in nearly all families of #Prunoidea# +(_Pipetta_, _Cannartus_, _Panarium_, _Zygartus_, &c.), it may possess a +peculiar value in this group. + + +1. _Pipettella fusiformis_, n. sp. + +Shell spindle-shaped, thin walled, the two opposite tubes being conical and +not longer than the short transverse axis of the ellipsoidal shell; no +sharp demarcation between them. The two axes of the ellipsoid bear the +proportion of 3 : 2. Network of the shell and of the tubes equal, delicate, +regular, hexagonal, with circular apertures of equal size; fourteen to +sixteen on the half equator of the shell. Bars very thin. The shell of this +species is similar to that of _Cannartiscus amphiconiscus_ (Pl. 39, fig. +19), but possesses no equatorial stricture and no medullary shell. + +_Dimensions._--Longer axis of the ellipsoid 0.18, shorter axis 0.12; length +of the tubes 0.1, their basal breadth 0.05; pores of the network 0.01, bars +0.001. + +_Habitat._--Northern Pacific, Station 244, depth 2900 fathoms. + + +{305}2. _Pipettella tubulosa_, n. sp. + +Shell ellipsoidal, thin walled, distinctly separated from the two opposite +tubes, which are cylindrical, longer than the main axis of the ellipsoid, +and one-sixth as broad as the shorter axis. The longer axis of the +ellipsoid bears to the shorter the proportion of 5 : 4. Network of the +shell and of the tubes equal, regular, with very small circular pores, +about as broad as the bars; sixteen to eighteen pores on the half equator +of the shell. + +_Dimensions._--Longer axis of the ellipsoid 0.15, shorter axis 0.12; length +of the tubes 0.16 to 0.2, breadth of them 0.02; pores of the network 0.003, +bars 0.003. + +_Habitat._--Western Tropical Pacific, Station 225, depth 4475 fathoms. + + +3. _Pipettella elongata_, n. sp. + +Shell ellipsoidal, thick walled, distinctly separated from both opposite +tubes, which are cylindrical, much prolonged, twice to three times as long +as the main axis of the ellipsoid, and one-fifth as broad as the shorter +axis. Both axes of the ellipsoid bear the proportion of 3 : 2. Network of +the shell and of the tubes irregular with small rounded pores of different +size, separated by broader bars (often twice to three times as broad), four +to six pores on the half equator of the shell. (This species somewhat +recalls _Solenosphaera serpentina_, Pl. 7, fig. 7; but the tubes are +straight, not contorted.) + +_Dimensions._--Longer axis of the ellipsoid 0.2, shorter axis 0.14; length +of the tubes 0.4 to 0.5, breadth 0.03; pores of the network 0.001 to 0.002, +bars 0.003 to 0.004. + +_Habitat._--Central area of the Pacific, Station 271, depth 2425 fathoms. + + +4. _Pipettella prismatica_, n. sp. (Pl. 39, fig. 6). + +Shell ellipsoidal, thick walled, distinctly marked off from the two +opposite tubes, which are longer than its main axis and as broad as +one-fifth of it; they are nearly four-sided prismatic, with four strong +ribs or edges; these are directed parallel to the main axis, in two +meridian planes, perpendicular to one another. The wall of the shell is +thickened in the equatorial plane, so as to form a slight stricture on the +inside, separating its two halves. Both axes of the ellipsoid bear the +proportion of 7 : 6. Network regular, with circular pores, somewhat broader +than the bars. The meshes of the shell (fourteen to sixteen on the half +equator) are twice as great as those of the tubes, which are arranged in +two longitudinal rows between every two ribs (there being eight +longitudinal rows on the whole tube). This species is very remarkable for +the rudimentary internal equatorial stricture of the shell (transition to +the genus _Cannartus_, Pl. 39, fig. 10), and by the four edges of the +tubes, which indicate two of the dimensive axes, the third being +represented by the main axis. + +_Dimensions._--Longer axis of the ellipsoid 0.14, shorter axis 0.12; length +of the tubes 0.15 to 0.16, breadth 0.03; pores of the shell 0.008 to 0.01, +pores of the tubes 0.004. + +_Habitat._--Western Tropical Pacific, Station 225, depth 4475 fathoms. + + + +{306}Family XII. #DRUPPULIDA#, Haeckel, 1882 (Pls. 15, 16, 17, 39). + +_Definition._--#Prunoidea# with ellipsoidal, latticed (not spongy) shell, +composed of two or more concentric shells; a simple or double cortical +shell enclosing one or two internal concentric shells (medullary shells), +without equatorial stricture. Central capsule ellipsoidal or cylindrical, +without annular equatorial constriction. + +The family #Druppulida# differs from the Ellipsida only in the possession +of a simple or double medullary shell, which is enclosed in the centre of +the central capsule, and connected with the ellipsoidal cortical shell +(lying outside it) by radial beams, perforating the membrane of the +capsule. The Druppulida exhibit therefore the same relation to the +Ellipsida that the Dyosphaerida among the #Sphaeroidea# bear to the +Monosphaerida. The cortical shell may be simple or multiple. The whole +fenestrated shell is thus composed of a variable number (two at least) of +concentric shells, which are connected by radial beams. + +_The Medullary Shell_--enclosed in the centre of the central capsule--is +either simple or double, and composed of two small concentric shells. Their +form is either spherical, or ellipsoidal, or lenticular. If the medullary +shell be ellipsoidal, the main axis of the ellipsoid is the same as in the +cortical shell. Sometimes the inner medullary shell is spherical, the outer +ellipsoidal or lenticular. If the medullary shell be lenticular (arising +from both poles of the main axis) its vertical axis is also identical with +that of the cortical shell (Pl. 39, fig. 5). + +_The Radial Beams_, which connect the medullary and cortical shell, are +either developed in all possible directions (Pls. 16, 17), or limited to +the equatorial plane, more rarely to the meridional plane. Sometimes the +connection is produced only by two opposite beams which lie in the minor or +equatorial axis (Pl. 39, figs. 3, 7, 8); more rarely in the major or +meridional axis (Pl. 17, figs. 7, 8). + +_The Cortical Shell_ is constantly ellipsoidal, rarely with modifications, +similar to those which appear in the simple shell of some Ellipsida. As a +rule it is simple, rarely composed of two or more (sometimes six or more) +concentric ellipsoidal shells (in _Cromyodruppa_ and _Cromyocarpus_). The +outer surface is commonly smooth, more rarely covered with radial spines +(in _Druppocarpus_, _Prunocarpus_, &c.). In the majority peculiar polar +appendages are developed at both poles of the main axis, these being +prolongations of them, either in the form of hollow fenestrated tubes +(_Pipetta_, _Pipettaria_, Pl. 39, figs. 7, 8), or solid strong spines. The +two polar spines are either equal in size and similar in form (as in +_Lithatractus_, _Stylatractus_) or unequal (as in _Druppatractus_, +_Xiphatractus_, Pls. 16, 17). + +The most primitive of all Druppulida is _Druppula_, with simple medullary +shell and simple cortical shell (Pl. 39, fig. 3); _Prunulum_ differs from +it only in the possession {307}of a double medullary shell (Pl. 39, fig. +4). From these two genera all other forms of the subfamily may be derived. + +_The Central Capsule_ of the Druppulida is constantly ellipsoidal, larger +than the concentric enclosed medullary shells, smaller than the surrounding +cortical shell; it is separated from the inner surface of the latter by a +thinner or thicker jelly-mantle. + +_Synopsis of the Genera of the Druppulida._ + + ------------------------------------------------------------------------- + Cortical shell without polar appendages (neither solid spines nor hollow + tubes at the poles of the main axis). + ------------------------------------------------------------------------- + { {Surface + {Medullary { smooth, 131. _Druppula_. + { shell simple.{ + { {Surface + Cortical shell { { spiny, 132. _Druppocarpus_. + simple, { + ellipsoidal. { {Surface + {Medullary { smooth, 133. _Prunulum_. + { shell double.{ + { {Surface + { { spiny, 134. _Prunocarpus_. + + Cortical shell }Medullary {Surface + composed of } shell { smooth, 135. _Cromyodruppa_. + two or more } double. { + concentric } {Surface + shells. } { spiny, 136. _Cromyocarpus_. + ------------------------------------------------------------------------- + Two opposite solid spines, arising from the poles of the main axis. + ------------------------------------------------------------------------- + { {Both polar + {Medullary { spines equal, 137. _Lithatractus_. + { shell { + { simple. {Both polar + Cortical { { spines + shell { { unequal, 138. _Druppatractus_. + simple, { + ellipsoidal.{ {Both polar + { { spines equal, 139. _Stylatractus_. + {Medullary { + { shell {Both polar + { double. { spines + { { unequal, 140. _Xiphatractus_. + + Cortical shell composed of two or more + concentric shells; medullary shell + double; both polar spines equal, 141. _Cromyatractus_. + ------------------------------------------------------------------------- + Two opposite hollow fenestrated tubes, arising from the poles of the + main axis. + ------------------------------------------------------------------------- + Medullary shell simple, 142. _Pipetta_. + + Medullary shell double, 143. _Pipettaria_. + + + +Genus 131. _Druppula_,[170] n. gen. + +_Definition._--#Druppulida# with simple ellipsoidal, cortical shell, and +simple medullary shell, without spines or polar tubes. + +The genus _Druppula_, as the simplest form of the Druppulida, may be +regarded as the common ancestral form of this subfamily. It may be derived +phylogenetically either {308}from _Carposphaera_ by prolongation of one +axis, or from _Cenellipsis_ by duplication of the fenestrated shell. The +outer (or cortical) shell is always more or less ellipsoidal; the inner (or +medullary) shell also is sometimes ellipsoidal, sometimes spherical. Both +shells are concentric, connected by a variable number of radial beams. +Compare _Haliomma oblongum_, Harting, 1863, L. N. 18, p. 15, pl. 2, fig. +42. + + + +Subgenus 1. _Druppuletta_, Haeckel. + +_Definition._--Pores of the cortical shell regular, hexagonal, or circular. + + +1. _Druppula drupa_, n. sp. + +Cortical shell thin walled, with smooth surface and regular network; both +its axes bear the proportion of 4 : 3. Pores regular, hexagonal, three +times as broad as the bars; twelve to fifteen on the half equator. +Medullary shell spherical, about one-third as broad as the cortical shell. + +_Dimensions._--Major axis of the ellipsoidal cortical shell 0.1 to 0.12, +minor axis 0.08 to 0.09; pores 0.06, bars 0.02; diameter of the medullary +shell 0.03. + +_Habitat._--Western Tropical Pacific, Station 225, depth 4475 fathoms; also +fossil in Barbados. + + +2. _Druppula pandanus_, n. sp. (Pl. 39, fig. 3). + +Cortical shell thin walled, somewhat rough, with regular network; both its +axes bear the proportion of 3 : 2. Pores subregular, circular, hexagonally +framed, one and a half times as broad as the elevated bars; ten to twelve +on the half equator. Medullary shell spherical, one-fourth as broad as the +cortical shell. + +_Dimensions._--Major axis of the cortical shell 0.16 to 0.17, minor axis +0.11 to 0.12; pores 0.01, bars 0.007; diameter of the medullary shell +0.035. + +_Habitat._--Pacific, central area, Station 268, depth 2900 fathoms. + + +3. _Druppula cocos_, n. sp. + +Cortical shell thick walled, somewhat rough, with regular network; +proportion of both axes = 6 : 5. Pores regular, circular, hexagonally +framed, quite as broad as the elevated bars; fourteen to sixteen on the +half equator. Medullary shell ellipsoidal (with longitudinal main axis), +nearly half as large as the cortical shell. + +_Dimensions._--Major axis of the cortical shell 0.07 to 0.08, minor axis +0.6 to 0.65; pores and bars 0.003 to 0.004; diameter of the medullary shell +0.03 and 0.035. + +_Habitat._--Western Tropical Pacific, Station 222, surface, Indian Ocean, +Ceylon, Haeckel. + + +4. _Druppula phoenix_, n. sp. + +Cortical shell thick walled, smooth, with regular network; proportion of +both axes = 5 : 4. Pores regular, circular, hexagonally lobulate (in the +same manner as in _Stauroxiphus gladius_, {309}Pl. 15, fig. 7), three times +as broad as the bars; ten to twelve on the half equator. Medullary shell +ellipsoidal (with longitudinal main axis), one-third as broad as the +cortical shell. + +_Dimensions._--Major axis of the cortical shell 0.1, minor axis 0.08; pores +0.009, bars 0.003; axis of the medullary shell 0.03 and 0.025. + +_Habitat._--Mediterranean, Smyrna, Haeckel, surface. + + +5. _Druppula areca_, n. sp. + +Cortical shell thin walled, with smooth surface and regular network; both +its axes bear the proportion of 4 : 3. Pores regular, circular, four times +as broad as the bars; fifteen to eighteen on the half equator. Medullary +shell spherical, half as broad as the cortical shell. + +_Dimensions._--Major axis of the ellipsoidal cortical shell 0.12 to 0.14, +minor axis 0.1 to 0.11; pores 0.008, bars 0.002; diameter of the medullary +shell 0.05 to 0.06. + +_Habitat._--Indian Ocean, off Bombay, Haeckel. + + +6. _Druppula ovata_, Haeckel. + + _Haliomma ovatum_, Ehrenberg, 1854, Mikrogeol., pl. xx. I. fig. 20. + + _Haliomma ovatum_, Haeckel, 1862, Monogr. d. Radiol., p. 432. + +Cortical shell thin walled, with smooth surface and regular network; +proportion of both axes = 3 : 2. Pores regular, circular, three times as +broad as the bars; nine to ten on the half equator. Medullary shell +spherical, one-third as broad as the cortical shell. + +_Dimensions._--Major axis 0.08 to 0.1, minor axis 0.05 to 0.06; pores +0.003, bars 0.001; diameter of the medullary shell 0.02. + +_Habitat._--Fossil in the Tertiary rocks of the Mediterranean coast, Greece +(Zante), Ehrenberg; Sicily (Caltanisetta), Haeckel. + + +7. _Druppula caryota_, n. sp. + +Cortical shell thick walled, with rough surface and regular network; +proportion of both axes = 5 : 4. Pores regular, circular, twice as broad as +the bars; sixteen to twenty on the half equator. Medullary shell +ellipsoidal, one-third as large as the cortical shell. + +_Dimensions._--Major axis 0.2 to 0.22, minor 0.16 to 0.18, pores 0.008, +bars 0.004; axes of the medullary shell 0.07 and 0.055. + +_Habitat._--Pacific, central area, Stations 266 to 268, depth 2700 to 2900 +fathoms. + + + +Subgenus 2. _Druppulissa_, Haeckel. + +_Definition._--Pores of the cortical shell irregular, of different form or +size, usually subcircular or roundish, sometimes lobed or compound. + + +{310}8. _Druppula nucula_, n. sp. + +Cortical shell thin walled, smooth, with irregular network; its two axes +bear the proportion 3 : 2. Pores subcircular or irregular, roundish, twice +to four times as broad as the bars; fifteen to twenty on the half equator. +Medullary shell spherical, about one-third as broad as the cortical shell. + +_Dimensions._--Major axis of the cortical shell 0.15 to 0.2, minor axis 0.1 +to 0.14; pores 0.006 to 0.012, bars 0.03; diameter of the medullary shell +0.04. + +_Habitat._--Cosmopolitan; Mediterranean, Atlantic, Pacific, surface. + + +9. _Druppula elliptica_, Haeckel. + + _Haliomma ellipticum_, Stoehr, 1880, Palaeontogr., _loc. cit._, p. 88, + Taf. i. fig. 11. + +Cortical shell thin walled, rough, or thorny, with irregular network; +proportion of the axes = 3 : 2. Pores subcircular or irregular, roundish, +about as broad as the bars; ten to twelve on the half equator. Medullary +shell half as broad as the cortical shell, irregularly polyhedral (with +crooked beams in its interior). + +_Dimensions._--Major axis 0.15, minor 0.06; pores and bars 0.006; diameter +of the medullary shell 0.03. + +_Habitat._--Fossil in the Tertiary rocks of Sicily: Grotte (Stoehr), +Caltanisetta (Haeckel). + + +10. _Druppula prunum_, n. sp. + +Cortical shell thick walled, smooth, with irregular network; proportion of +the axes = 5 : 4. Pores subcircular or irregular, roundish, three to four +times as broad as the bars; seven to eight on the half equator; every pore +is closed at the bottom by a thin membrane, perforated by four to six +irregular pores (like _Stylatractus sethoporus_, Pl. 17, fig. 3). Medullary +shell spherical, one-third as broad as the cortical shell. + +_Dimensions._--Major axis 0.2, minor axis 0.16; pores 0.03, bars 0.01; +small enclosed porules 0.01; diameter of the medullary shell 0.05. + +_Habitat._--Mediterranean, surface, Portofino near Genoa, Haeckel. + + +11. _Druppula oliva_, n. sp. + +Cortical shell thick walled, rough, with irregular network; proportion of +the axes = 5 : 4. Pores irregular, roundish, three to four times as broad +as the bars; lobed or composed of several conjugated porules (as in +_Lithapium halicapsa_, Pl. 14, fig. 8); five to six large pores on the half +equator. Medullary shell ellipsoidal, about one-third as broad as the +cortical shell. + +_Dimensions._--Major axis of the cortical shell 0.15, minor 0.12; pores +0.02 to 0.03, bars 0.007; diameter of the medullary shell 0.04. + +_Habitat._--Mediterranean (Corfu), Canary Islands (Lanzerote), Haeckel. + + + +{311}Genus 132. _Druppocarpus_,[171] n. gen. + +_Definition._--#Druppulida# with simple ellipsoidal cortical shell and +simple medullary shell, with numerous radial spines, without polar tubes. + +The genus _Druppocarpus_ differs from _Druppula_ only in the radial spines, +which arise between the pores of the cortical shell, and therefore exhibits +the same relation to it that _Ellipsidium_ bears to _Cenellipsis_, or +_Prunocarpus_ to _Prunulum_. + + + +Subgenus 1. _Druppocarpetta_, Haeckel. + +_Definition._--Network of the cortical shell regular, with meshes of equal +size and similar form. + + +1. _Druppocarpus ananassa_, n. sp. + +Cortical shell thin walled, with regular, circular, hexagonally framed +pores, of about the same breadth as the elevated bars; fourteen to sixteen +on the half equator. From each hexagon-corner (between every three pores) +arises a short thin radial spine, about as long as two pores, three-sided +pyramidal at the base. Proportion of both cortical axes = 4 : 3. Medullary +shell spherical, half as broad as the cortical shell. (Greatly resembles +_Druppula pandanus_, Pl. 39, fig. 3, but differs in the larger medullary +shell and the spines on the surface.) + +_Dimensions._--Major axis of the ellipsoidal cortical shell 0.16, minor +0.12; pores and bars 0.006; length of the radial spines 0.02; diameter of +the medullary shell 0.06. + +_Habitat._--South Pacific, Station 289, surface. + + +2. _Druppocarpus castanea_, n. sp. + +Cortical shell thin walled, with regular circular pores (without hexagonal +frames), of about the same breadth as the bars; twelve to fourteen on the +half equator. Between every three meshes arise a short conical spine with +bristle-like apex, twice to four times as long as one pore. Proportion of +both cortical axes = 3 : 2. Medullary shell spherical, one-third as broad +as the cortical. (Resembles very closely the spherical _Haliomma castanea_, +Haeckel, figured in my Monograph. pl. xxiv. fig. 4.) + +_Dimensions._--Major axis 0.15, minor axis 0.1; pores and bars 0.005; +length of the radial spines 0.01 to 0.02; medullary shell 0.035. + +_Habitat._--North Atlantic, surface; Canary Islands, Lanzerote, Haeckel. + + + +Subgenus 2. _Druppocarpissa_, Haeckel. + +_Definition._--Network of the cortical shell irregular, with meshes of +different size or form. + + +{312}3. _Druppocarpus chamaerops_, n. sp. + +Cortical shell thin walled, with irregular, roundish, or subcircular pores +of very different size, twice to six times as broad as the thin bars; eight +to twelve on the half equator. Between them arise numerous thin, +bristle-like radial spines, about half as long as the equatorial axis, and +equal to the diameter of the spherical medullary shell; pores of the latter +subregular, circular, very small. (Resembles _Prunocarpus artocarpus_, Pl. +39, fig. 5, but differs in the simple spherical medullary shell.) + +_Dimensions._--Major axis 0.12, minor 0.09; meshes 0.005 to 0.02, bars +0.003; length of the radial spines 0.05; diameter of the medullary shell +0.04. + +_Habitat._--Mediterranean, in the Strait of Gibraltar, Algesiras, Haeckel, +surface. + + +4. _Druppocarpus borassus_, n. sp. + +Cortical shell thick walled, with irregular, roundish, or subcircular +pores, three to five times as broad as the bars; twelve to fifteen on the +half equator. Irregularly scattered on the surface about twenty to thirty +short conical spines; their length equals their basal breadth and the +diameter of the largest pores. Medullary shell ellipsoidal, half as large +as the cortical. + +_Dimensions._--Major axis 0.1, minor 0.08; pores 0.006 to 0.01, bars 0.002; +length and thickness of the radial spines 0.01; axes of the medullary shell +0.05 and 0.04. + +_Habitat._--Pacific, central area, Station 268, depth 2900 fathoms. + + +5. _Druppocarpus corypha_, n. sp. + +Cortical shell thick walled, with irregular, funnel-like, roundish pores, +scarcely as broad as the bars; sixteen to twenty on the half equator. +Irregularly scattered on the surface about fifteen to twenty three-sided +pyramidal radial spines, half as long as the equatorial axis, and as the +diameter of the medullary shell. + +_Dimensions._--Major axis 0.17, minor 0.14; pores and bars 0.003 to 0.009; +length of the radial spines 0.08; diameter of the medullary shell 0.09. + +_Habitat._--Fossil in the Tertiary rocks of the Nicobars, Haeckel. + + + +Genus 133. _Prunulum_,[172] n. gen. + +_Definition._--#Druppulida# with simple ellipsoidal cortical shell and +double medullary shell; without spines or polar tubes. + +The genus _Prunulum_ differs from _Druppula_ in the double (not simple) +medullary shell, which is sometimes spherical, sometimes ellipsoidal; it +may be derived either from _Druppula_ by duplication of the medullary +shell, or from _Thecosphaera_ by prolongation of one axis. + + + +{313}Subgenus 1. _Prunuletta_, Haeckel. + +_Definition._--Network of the cortical shell regular, with meshes of equal +size and similar form. + + +1. _Prunulum frugulum_, n. sp. + +Cortical shell thin walled, smooth, with regular, hexagonal pores, three +times as broad as the bars; ten to twelve on the half equator. Proportion +of the major axis of the ellipsoid to the minor = 4 : 3. Both medullary +shells spherical. (Differs from _Druppula drupa_ almost entirely in the +double medullary shell.) + +_Dimensions._--Major axis of the ellipsoidal cortical shell 0.12, minor +0.09; pores 0.006, bars 0.002; diameter of both medullary shells 0.05 and +0.03. + +_Habitat._--Pacific, central area, Station 266, depth 2750 fathoms. + + +2. _Prunulum cerasum_, n. sp. + +Cortical shell thick walled, smooth, with circular, hexagonally framed +pores, of the same breadth as the bars; sixteen to eighteen on the half +equator. Proportion of the two axes of the ellipsoid = 5 : 4. Both +medullary shells spherical. (The cortical shell resembles that of _Pipetta +tuba_, Pl. 39, fig. 7, without the polar tubes.) + +_Dimensions._--Major axis 0.15, minor 0.12; pores and bars 0.007; diameter +of the medullary shells 0.08 and 0.04. + +_Habitat._--South Atlantic, Station 332, depth 2200 fathoms. + + +3. _Prunulum amygdalum_, n. sp. + +Cortical shell thick walled, smooth, with regular, circular, hexagonally +lobulated pores, three times as broad as the bars; twelve to fourteen on +the half equator (of the same form as in _Druppula phoenix_ and in +_Stauroxiphos gladius_, Pl. 15, fig. 7). Proportion of the two axes = +6 : 5. Inner medullary shell spherical, outer ellipsoidal. + +_Dimensions._--Major axis 0.12, minor 0.1; pores 0.009, bars 0.003; +diameter of the medullary shells 0.07 and 0.04. + +_Habitat._--Mediterranean (Corfu), surface. + + +4. _Prunulum coccymelium_ (Pl. 39, fig. 4). + +Cortical shell thin walled, slightly rough, with regular, circular pores, +twice as broad as the bars; twelve to fifteen on the half equator. +Proportion of both axes = 4 : 3. Both medullary shells spherical. + +_Dimensions._--Major axis 0.12, minor 0.09; pores 0.006, bars 0.003; +diameter of the medullary shells 0.06 and 0.03. + +_Habitat._--Pacific, central area, Station 273, depth 2350 fathoms. + + +{314}5. _Prunulum crenatum_, Haeckel. + + ? _Haliomma crenatum_, Ehrenberg, 1854, Mikrogeol., Taf. xxii. fig. 36. + + _Actinomma crenatum_, Stoehr, 1880, Palaeontogr., vol. xxvi. p. 94, Taf. + iii. fig. 3. + + _Caryolithis crenata_, Ehrenberg, 1847, Monatsber. d. k. preuss. Akad. d. + Wiss. Berlin, p. 43. + +Cortical shell thick walled, slightly rough or thorny, with small, regular, +circular pores, of the same breadth as the bars; sixteen to eighteen on the +half equator. Proportion of the two axes = 4 : 3. Both medullary shells +ellipsoidal. (The figure of Stoehr represents exactly the fossil form, as I +have observed it myself in the Caltanisetta rocks, whilst the figure of +Ehrenberg is inaccurate and doubtful. The same form, somewhat variable in +size and in the number of the pores, I have also observed in the Pacific +ooze.) + +_Dimensions._--Major axis 0.14 to 0.17, minor 0.1 to 0.13; pores and bars +0.006; main axes of the medullary shells 0.09 and 0.03. + +_Habitat._--Fossil in the Tertiary rocks of Sicily (Grotte and +Caltanisetta); living in the Central Pacific, Station 268, depth 2900 +fathoms. + + +6. _Prunulum triplex_, Haeckel. + + _Haliomma triplex_, Ehrenberg, 1854, Microgeol., Taf. xxxvB. fig. Biv., + q. + + _Actinomma triplex_, Haeckel, 1862, Monogr. d. Radiol., p. 444. + +Cortical shell thin walled, covered with numerous very thin, short, +bristle-like spines. Pores small, regular, circular, of the same breadth as +the bars; fourteen to sixteen on the half equator. Proportion of the two +axes = 3 : 2. Both medullary shells ellipsoidal. The description of +Ehrenberg--as is very often the case--is quite incongruent with his figure. +From a combination of both I give here the diagnosis of a deep-sea species, +which is possibly identical with it. The velvet-like covering of very short +and thin bristles is peculiarly characteristic of this species. + +_Dimensions._--Major axis 0.1, minor 0.065; pores and bars 0.004; main axes +of the medullary shells 0.04 and 0.02. + +_Habitat._--North Atlantic, 1800 fathoms, Ehrenberg; Station 353, depth +2965 fathoms. + + + +Subgenus 2. _Prunulissa_, Haeckel. + +_Definition._--Network of the cortical shell irregular, with meshes of +different form or size (usually roundish, but sometimes lobed or compound). + + +7. _Prunulum persicum_, n. sp. + +Cortical shell thick walled, with smooth surface and irregular, roundish, +double-contoured pores, twice to four times as broad as the bars; eight to +ten on the half equator. Some of the pores are simple, often subcircular, +others lobed, i.e., composed of from two to three confluent pores as in +_Amphisphaera pluto_ (Pl. 17, fig. 7). Proportion of the two axes = 3 : 2. +Both medullary shells ellipsoidal (or the inner spherical). + +{315}_Dimensions._--Major axis 0.12, minor 0.08; pores 0.06 to 0.012, bars +0.003; main axes of the medullary shells 0.05 and 0.025. + +_Habitat._--Indian Ocean, between Socotra and Ceylon, surface, Haeckel. + + +8. _Prunulum fenestratum_, Haeckel. + + _Actinomma fenestratum_, Stoehr, 1880, Palaeontogr., vol. xxvi. p. 94, + Taf. iii. fig. 2. + +Cortical shell thick walled, rough, with irregular, roundish pores, once to +three times as broad as the bars; twelve to fourteen on the half equator. +Proportion of the two axes = 9 : 8. Both medullary shells ellipsoidal. (The +pores in Stoehr's description are by mistake called "regular"; in the +figure they are very irregular, as also in the fossil specimens observed by +myself. Between the cortical pores arise very short irregular thorns.) + +_Dimensions._--Major axis 0.12 to 0.15, minor 0.1 to 0.12; pores 0.003 to +0.01, bars 0.003; main axis of the outer medullary shell 0.07 to 0.09, of +the inner 0.03 to 0.04. + +_Habitat._--Fossil in the Tertiary rocks of Sicily; Grotte, Stoehr, +Caltanisetta, Haeckel. + + +9. _Prunulum pyrenium_, n. sp. + +Cortical shell very thick walled, smooth, with large irregular, roundish +pores, three to four times as broad as the bars; six to eight on the half +equator. The bottom of each funnel-like pore is closed by a thin siliceous +membrane, perforated by three to five irregular roundish pores. Proportion +of the two axes = 4 : 3. Both medullary shells ellipsoidal. (Closely +resembles _Stylatractus sethoporus_, Pl. 17, figs. 2, 3, but is devoid of +the polar spines.) + +_Dimensions._--Major axis 0.16, minor 0.12; pores 0.015 to 0.02, bars +0.005; porules 0.01; main axes of the medullary shells 0.07 and 0.03. + +_Habitat._--Western Tropical Pacific, Station 225, depth 4475 fathoms. + + + +Genus 134. _Prunocarpus_,[173] n. gen. + +_Definition._--#Druppulida# with simple ellipsoidal cortical shell and +double medullary shell, with numerous radial spines, but without polar +tubes. + +The genus _Prunocarpus_ differs from _Prunulum_ only in the radial spines +of the cortical shell, and exhibits therefore the same relation to it that +_Druppocarpus_ bears to _Druppula_. While in the latter the medullary shell +is simple, in the former it is double. + + + +Subgenus 1. _Prunocarpetta_, Haeckel. + +_Definition._--Network of the cortical shell regular, with meshes of equal +size and similar form. + + +{316}1. _Prunocarpus datura_, n. sp. + +Cortical shell thick walled, with regular, circular pores, twice as broad +as the bars; ten to twelve on the half equator. Between every three meshes +arises a short conical spine, twice to three times as long as one pore. +Both medullary shells spherical. (Differs mainly from _Ellipsidium datura_ +and from _Druppocarpus castanea_ in the double medullary shell. The outer +network resembles _Haliomma castanea_, figured 1862 in my Monograph, Taf. +xxiv. fig. 4.) + +_Dimensions._--Major axis of the ellipsoid 0.16, minor 0.12; pores 0.012, +bars 0.006; length of the radial spines 0.03; diameter of the medullary +shells 0.06 and 0.04. + +_Habitat._--North Atlantic, Faeroee Channel, John Murray, surface. + + +2. _Prunocarpus sparganium_, n. sp. + +Cortical shell thick walled, with very small, numerous, regular, circular +pores, of the same size as the bars; forty to fifty on the half equator. +Between them over the entire surface occur small conical spines. +Irregularly scattered over the surface ten to twenty larger conical spines, +three to six times as thick at the base as one pore, one-fourth to one-half +as long as the main axis. Both medullary shells ellipsoidal. + +_Dimensions._--Major axis of the cortical shell 0.16, of the outer +medullary shell 0.11, of the inner 0.06; equatorial axis of the first shell +0.12, of the second 0.08, of the third 0.04; pores and bars on an average +0.005; length of the spines 0.05 to 0.1, basal breadth 0.02 to 0.03. + +_Habitat._--Fossil in the Barbados deposits (Haeckel). + + + +Subgenus 2. _Prunocarpilla_, Haeckel. + +_Definition._--Network of the cortical shell irregular, with meshes of +different size or form. + + +3. _Prunocarpus artocarpium_, n. sp. (Pl. 39, fig. 5). + +Cortical shell thin walled with irregular, roundish pores of very different +sizes, twice to nine times as broad as the thin bars; ten to fifteen on the +half equator. Between them arise numerous bristle-shaped, radial spines, +with conical base, on an average one-fourth to two-thirds as long as the +equatorial axis. The outer medullary shell, with irregular, roundish pores, +presents a transverse ellipsoid, its main axis lying in the equatorial axis +of the cortical shell, whilst its equatorial axis corresponds to the main +axis of the latter. Inner medullary shell very small, spherical, with very +small pores. + +_Dimensions._--Major axis of the cortical shell 0.14, of the outer +medullary shell 0.05; minor axis of the former 0.1, of the latter 0.035; +diameter of the inner medullary shell 0.014; pores of the cortical shell +0.005 to 0.02, bars 0.002; length of the radial spines 0.02 to 0.06. + +_Habitat._--Indian Ocean, surface; Ceylon, Belligemma, Haeckel. + + +{317}4. _Prunocarpus melocactus_, n. sp. + +Cortical shell thick walled, with irregular, roundish pores, twice to five +times as broad as the bars; eighteen to twenty-four on the half equator. +Between them arise over the entire surface small conical thorns, not longer +than the largest pores. Irregularly scattered over the surface twenty to +thirty strong, conical, radial spines, about half as long as the main axis, +as broad at the base as a large pore. Both medullary shells ellipsoidal, +their main axis identical with that of the cortical shell. + +_Dimensions._--Major axis of the outer shell 0.18, of the middle 0.09, of +the inner 0.05; minor axis of the first 0.14, of the second 0.07, of the +third 0.04; pores of the cortical shell 0.006 to 0.02, bars 0.004; length +of the spines 0.1, basal breadth 0.01. + +_Habitat._--Pacific, central area, Station 268, depth 2900 fathoms; also +fossil in the Tertiary rocks of Sicily; Caltanisetta, Haeckel. + + + +Genus 135. _Cromyodruppa_,[174] n. gen. + +_Definition._--#Druppulida# with four or more concentric shells (two +medullary and two or more cortical shells), without spines or polar tubes. + +The genus _Cromyodruppa_ is characterised by the multiplication of the +concentric fenestrated shell, which is composed of two medullary shells +(enclosed in the central capsule) and two or more cortical shells (outside +it). The former may be either spherical or ellipsoidal. The latter are +always ellipsoidal, and in this it differs from _Cromyosphaera_. Probably +_Cromyodruppa_ has arisen from _Prunulum_ by secondary apposition of more +cortical envelopes. + + + +Subgenus 1. _Cromyodruppium_, Haeckel. + +_Definition._--Shell composed of four concentric shells, two medullary and +two cortical. + + +1. _Cromyodruppa cepa_, n. sp. + +Shell composed of two ellipsoidal, cortical, and two spherical medullary +shells. Proportion of the main axes of the four shells = 1 : 2 : 4 : 5. +Network of all four shells nearly of the same form, subregular, with +circular pores of almost equal size in every shell. The absolute size of +the pores increases from the innermost to the outermost shell, but the +breadth of the bars does not increase in a similar degree. The bars of the +outermost shell are only twice as broad as those of the innermost; but the +pores are three to four times larger. Surface of all four shells smooth. +(The shell greatly resembles that of _Cromyatractus tetraphractus_, Pl. 15, +fig. 2, but is devoid of polar spines; it differs also in the spherical +form of both medullary shells and their relative size.) + +{318}_Dimensions._--Main axes of the four shells--(A) innermost 0.035, (B) +second 0.08, (C) third 0.15, (D) outermost 0.2; their equatorial axes--(A) +0.03, (B) 0.08, (C) 0.12, (D) 0.16; pores 0.004 to 0.016, bars 0.002 to +0.004. + +_Habitat._--Western Tropical Pacific, Station 198, depth 2150 fathoms. + + + +Subgenus 2. _Caryodruppula_, Haeckel. + +_Definition._--Shell composed of five or more concentric shells (two +medullary and three or more cortical). + + +2. _Cromyodruppa mango_, n. sp. + +Shell composed of six ellipsoidal, concentric shells, two medullary and +four cortical. Proportion of their main axes = 2 : 3 : 8 : 11 : 14 : 18. +Network of the two medullary shells and of the innermost cortical shell +subregular, with subcircular pores, about the same breadth as the bars. +Network of the three outer cortical shells more lax, with larger, +irregular, roundish pores, twice to six times as broad as the bars. The +size of the pores and bars increases gradually from the innermost to the +outermost shell. Surface smooth. + +_Dimensions._--Main axis of the six shells--(A) innermost 0.04, (B) 0.06, +(C) 0.16, (D) 0.22, (E) 0.28, (F) 0.35; their equatorial axes--(A) +innermost 0.03, (B) 0.05, (C) 0.12, (D) 0.16, (E) 0.2, (F) 0.25; pores +0.003 to 0.02, bars 0.003 to 0.005. + +_Habitat._--Indian Ocean, surface; Matura, Ceylon, Haeckel. + + + +Genus 136. _Cromyocarpus_,[175] n. gen. + +_Definition._--#Druppulida# with four or more concentric shells (two +medullary and two or more cortical shells), with numerous radial spines, +but without polar tubes. + +The genus _Cromyocarpus_ differs from _Cromyodruppa_ only in the +development of numerous large radial spines which start from the outer +surface of the shell. It exhibits therefore the same relation to the latter +that _Prunocarpus_ bears to _Prunulum_, or _Druppocarpus_ to _Druppula_. It +differs from both in the multiplication of the cortical shell. + + +1. _Cromyocarpus quadrifarius_, n. sp. + +Shell composed of four concentric shells, two ellipsoidal cortical shells, +and two spherical medullary shells. Proportion of their main axes = +10 : 8 : 3 : 2. Pores of the two cortical shells irregular, roundish, twice +to four times as broad as the bars. Pores of the two medullary shells +subregular, circular, about the same size as the bars. Outer surface +covered with numerous conical radial spines, about half as long as the main +axis, half as broad at the base as the innermost shell. + +{319}_Dimensions._--Major axis of the outer cortical shell 0.2, of the +inner 0.15; equatorial axis of the former 0.16, of the latter 0.12; +diameter of the outer medullary shell 0.06, of the inner 0.04; pores of the +cortical shells 0.01 to 0.02, of the medullary shells 0.004 to 0.008, bars +0.003 to 0.006; length of the radial spines 0.1, basal breadth 0.02. + +_Habitat._--Indian Antarctic Ocean, Station 157, depth 1950 fathoms. + + + +Genus 137. _Lithatractus_,[176] n. gen. + +_Definition._--#Druppulida# with simple ellipsoidal cortical shell and +simple medullary shell, with two large opposite polar spines in the main +axis of equal size and similar form. + +The genus _Lithatractus_, rich in common and widely distributed species, +begins the series of those Druppulida which are characterised by peculiar +polar spines at both poles of the main axis. It repeats the formation of +_Stylosphaera_ and _Ellipsostylus_, and differs from the former in the +ellipsoidal form of the cortical shell, from the latter in the possession +of a medullary shell. Formerly all these forms were united in the one genus +_Stylosphaera_ (see above, p. 121). + + + +Subgenus 1. _Lithatractara_, Haeckel. + +_Definition._--Network of the outer shell regular or subregular, with +meshes of nearly equal size and similar form; surface smooth, without +thorns or papillae. + + +1. _Lithatractus hexagonalis_, n. sp. + +Outer shell thin walled, smooth, without thorns or papillae, with regular +delicate network; the meshes hexagonal, three to four times as broad as the +thin bars; ten to twelve on the half equator. Proportion of the major axis +of the ellipsoid to the minor = 4 : 3. Minor axis three times as large as +that of the inner spherical shell; pores of the latter, small, circular. +Two spines three-sided pyramidal, as long as the radius of the outer shell, +each as broad at its base as one mesh. + +_Dimensions._--Longer axis of the ellipsoidal cortical shell 0.16, shorter +axis 0.12; pores 0.011, bars 0.003; diameter of the spherical medullary +shell 0.04; length of the polar spines 0.07; basal breadth 0.01. + +_Habitat._--North Pacific, Station 253, depth 3125 fathoms. + + +2. _Lithatractus fragilis_, n. sp. (Pl. 16, fig. 3). + + _Stylosphaera fragilis_, Haeckel, 1881, Prodromus et Atlas, pl. xvi. fig. + 3. + +Outer shell thin walled, smooth, without thorns or papillae, with regular +network; the meshes circular, of equal size, eight to ten times as broad as +the thin bars; six to eight on the half equator. {320}Proportion of the +major axis of the ellipsoid to the minor = 5 : 4. Minor axis once and +one-third as broad as that of the ellipsoidal inner shell, the pores of +which are also circular, but of half the size. Two spines strong, +three-sided pyramidal, acute, as broad as a large mesh, as long as the +equatorial axis. The stout inner prolongations of these form the only +connection between the two shells. + +_Dimensions._--Longer axis of the ellipsoidal cortical shell 0.12, shorter +axis 0.1; pores 0.02, bars 0.002; longer axes of the ellipsoidal medullary +shell 0.09, shorter axis 0.07; pores 0.01, bars 0.002; length of the polar +spines 0.1, basal breadth 0.002. + +_Habitat._--Central area of the Pacific, Station 272, depth 2600 fathoms. + + +3. _Lithatractus leptostylus_, n. sp. + +Outer shell thin walled, smooth, with regular, circular pores of equal +size, three to four times as broad as the thin bars; ten to twelve on the +half equator. Proportion of the major axis to the minor = 7 : 6. Minor axis +three times as large as that of the inner spherical shell; pores of the +latter half as large. Polar spines cylindrical, blunt, longer than the +major axis, scarcely half as broad as one larger pore. + +_Dimensions._--Longer axis of the cortical shell 0.14, shorter axis 0.12; +pores 0.015 to 0.02, bars 0.004; diameter of the medullary shell 0.04; +length of the polar spines 0.15 to 0.2, its thickness 0.01. + +_Habitat._--Central area of the Pacific, Stations 270 to 272, depth 2425 to +2925 fathoms. + + +4. _Lithatractus pachystylus_, n. sp. + +Outer shell thick walled, smooth, with regular, circular pores of equal +size; twelve to fifteen on the half equator. Each pore is deep, +funnel-shaped, its outer aperture double the size of the inner, its breadth +about three times that of the high bars. Proportion of the major axis to +the minor = 6 : 5. Major axis double as long as the diameter of the +spherical medullary shell. Polar spines very thick and short, tetrahedral, +one-fourth as long and broad as the major axis. + +_Dimensions._--Longer axis of the cortical shell 0.17, shorter axis 0.14; +pores 0.01, bars 0.003; diameter of the medullary shell 0.08; length and +thickness of the polar spines 0.04. + +_Habitat._--Central area of the Pacific, Station 271, depth 2425 fathoms. + + +5. _Lithatractus convallaria_, n. sp. + +Outer shell thick walled, smooth, with elegant regular network; the meshes +circular, six-lobed, rosette-like (of the same form as _Stauroxiphos +gladius_, Pl. 15, fig. 7), twice to three times as broad as the bars; six +to eight on the half equator. Proportion of the major axis of the ellipsoid +to the minor = 4 : 3. Minor axis twice as long as the diameter of the +inner spherical shell, which has regular, simple, circular pores of half +the size. Polar spines short and thick, conical, only one-fourth to +one-sixth as long as the minor axis, and quite as thick. + +_Dimensions._--Longer axis of the cortical shell 0.16, shorter axis 0.12; +pores 0.016, bars 0.006; diameter of the medullary shell 0.06; length of +the polar spines 0.02 to 0.03, basal thickness the same. + +_Habitat._--Central area of the Pacific, Station 268, depth 2900 fathoms. + + + +{321}Subgenus 2. _Lithatractylis_, Haeckel. + +_Definition._--Network of the outer shell regular, with meshes of equal +size and similar form; surface thorny or papillose, covered with small +conical spines or tubercles. + + +6. _Lithatractus echiniscus_, n. sp. + +Outer shell thorny, thin walled, with regular network; meshes circular, +with hexagonal frame, four to five times as broad as the thin bars; +eighteen to twenty on the half equator. From every corner between the three +meshes, where three hexagons unite, starts one short, straight, triangular +thorn (as in _Ellipsoxiphus elegans_, Pl. 14, fig. 7). Proportion of the +major axis of the ellipsoid to the minor = 4 : 3. Minor axis twice the +diameter of the inner spherical shell, the pores of which are half as +broad, circular. Polar spines three-sided pyramidal, about as long as the +minor axis, as broad at the base as one hexagonal frame. + +_Dimensions._--Longer axis of the cortical shell 0.08, shorter axis = 0.06; +pores 0.004, bars 0.001; length of the polar spines 0.05, basal thickness +0.005; diameter of the inner shell 0.03. + +_Habitat._--South Atlantic, off Tristan da Cunha, Station 334, surface. + + +7. _Lithatractus carduelis_, n. sp. + +Outer shell thin walled, thorny, with regular network; meshes circular, +simple, four to six times as broad as the thin bars; ten to twelve on the +half equator. Between every three meshes is one short conical spine. +Proportion of the major axis to the minor = 6 : 5. Minor axis equals three +times the diameter of the inner spherical shell. Polar spines conical, +thick, half as long as the major axis, thicker at the base than one pore. +(This species differs from _Stylatractus carduus_ only by the simple +medullary shell.) + +_Dimensions._--Longer axis of the ellipsoid 0.12 to 0.16, shorter axis 0.1 +to 0.14; pores 0.02 to 0.03, bars 0.005; length of the polar spines 0.05 to +0.10, basal breadth 0.04; diameter of the medullary shell 0.03 to 0.04. + +_Habitat._--Central area of the Pacific, Stations 268 to 274, depth 2350 to +2900 fathoms; also fossil in the rocks of Barbados. + + +8. _Lithatractus cirsium_, n. sp. + +Outer shell thin walled, thorny, with regular network; pores circular, +simple, small, two to three times as broad as the thin bars; eighteen to +twenty-four on the half equator. Proportion of the major axis to the minor += 4 : 3. Inner shell ellipsoidal, half as large as the outer. Polar spines +cylindrical, blunt, thin, very variable in length (one-fourth to +three-fourths of the major axis, not thicker than a mesh). + +_Dimensions._--Longer axis of the ellipsoid 0.07 to 0.09, shorter axis 0.05 +to 0.07; pores 0.005 to 0.006, bars 0.002; length of the polar spines 0.02 +to 0.06, basal breadth 0.004; length of the inner shell 0.04, breadth 0.03. + +_Habitat._--North Pacific, Station 244, surface. + + +{322}9. _Lithatractus rosetta_, n. sp. + +Outer shell thick walled, thorny, with regular network; meshes circular, +funnel-shaped, its outer aperture elegant, rosette-like, with eight to ten +incisions (like _Stylosphaera calliope_, Pl. 16, fig. 6); eight to ten +meshes on the half equator, three to four times as broad as the bars. +Proportion of the longer axis to the shorter = 5 : 4. Shorter axis equals +three times the diameter of the inner spherical shell. Polar spines +three-sided pyramidal, about half as long as the shorter axis, as broad at +the base as a mesh. + +_Dimensions._--Longer axis of the cortical shell 0.15, shorter 0.12; pores +0.02, bars 0.005; length of the polar spines 0.05, basal breadth 0.02; +diameter of the inner shell 0.04. + +_Habitat._--South-eastern part of the Pacific, Station 302, depth 1450 +fathoms. + + + +Subgenus 3. _Lithatractona_, Haeckel. + +_Definition._--Network of the outer shell irregular, with meshes of unequal +size or dissimilar form; surface smooth, without thorns or papillae. + + +10. _Lithatractus conifer_, n. sp. + +Outer shell thin walled, smooth, with irregular, roundish pores, two to +four times as broad as the thin bars; fifteen to twenty on the half +equator. Margin of the pores simple. Proportion of the major axis to the +minor = 3 : 2. Minor axis twice as large as the diameter of the inner +spherical shell, the pores of which are also irregular, roundish, but of +half the size. Polar spines conical, somewhat shorter than the main axis, +on the base two to three times as thick as a large pore. + +_Dimensions._--Longer axis of the outer shell 0.15, shorter axis 0.1; pores +0.002 to 0.004, bars 0.001; diameter of the inner shell 0.05; length of the +polar spines 0.12, basal breadth 0.012. + +_Habitat._--South Atlantic, Station 325, surface. + + +11. _Lithatractus lobatus_, n. sp. + +Outer shell thick walled, smooth, with irregular, roundish pores, four to +eight times as broad as the bars; six to eight on the half equator. Margin +of the pores lobed, very irregular, bluntly dentate, by five to twenty +slight incisions. Proportion of the major axis to the minor very variable, +between 3 : 2 and 9 : 8. Diameter of the inner shell also variable, between +one-third and one-half of the outer; pores of the former scarcely half the +size of the latter, simple, roundish, or circular. The inner shell is at +some parts quite spherical, at other parts more or less ellipsoidal. Polar +spines conical, very variable in size and form, sometimes in the basal half +triangular; they are sometimes somewhat longer than the main axis, at other +times considerably shorter; their basal breadth is occasionally the same as +that of the largest pores, sometimes, however, scarcely half as large. This +deep-sea species is very common in the central area of the Tropical Pacific +(Stations 266 to 272), and occurs also fossil in the Barbados deposits. It +is interesting from its great variability, and sometimes constitutes a +transitional form to _Stylosphaera_. + +{323}_Dimensions._--Longer axis of the outer shell 0.1 to 0.15, shorter +axis 0.05 to 0.12; pores 0.018 to 0.024, bars 0.002 to 0.004; diameter of +the inner shell 0.04 to 0.08; length of the polar spines 0.08 to 0.2, basal +thickness 0.01 to 0.02. + +_Habitat._--Central area of the Pacific, common; Stations 266 to 272, depth +2425 to 2900 fathoms; also fossil in Barbados. + + +12. _Lithatractus jugatus_, n. sp. (Pl. 16, fig. 2). + + _Stylosphaera jugata_, Haeckel, 1881, Prodromus et Atlas (pl. xvi. fig. + 2). + +Outer shell thick walled, smooth, or somewhat reticulated, with a peculiar, +irregular, double network. The pores are roundish, of very different sizes, +with double margin of the outer aperture, and so irregularly distributed in +polygonal groups that every group contains two to six pores immediately +touching each other; the groups are separated by broader bars. On the half +equator of the shell are about six to eight groups and twelve to eighteen +pores. Proportion of the longer axis of the ellipsoidal shell to the +shorter = 6 : 5 or 5 : 4. Inner ellipsoidal shell about half the size; its +pores are not easy to make out. Polar spines three-sided pyramidal, with +prominent edges, about half as long as the major axis, as broad at the base +as a group of pores. (Nearly allied to _Stylosphaera jugata_, p. 137.) + +_Dimensions._--Longer axis of the cortical shell 0.12 to 0.16, shorter axis +0.1 to 0.13; pores 0.01 to 0.02; length of the polar spines 0.06 to 0.08, +basal breadth 0.03 to 0.4. + +_Habitat._--Central area of the Pacific, Stations 266 to 272, depth 2425 to +2900 fathoms. + + + +Subgenus 4. _Lithatractium_, Haeckel. + +_Definition._--Network of the outer shell irregular, with meshes of unequal +size or dissimilar form; surface thorny or papillose, covered with small +conical spines or tubercles. + + +13. _Lithatractus conostylus_, n. sp. + +Outer shell thorny, thin walled, with irregular network; pores roundish, of +unequal size, twice to four times as broad as the thin bars; sixteen to +twenty on the half equator. Proportion of the longer axis to the shorter = +5 : 4. Shorter axis twice the diameter of the inner spherical shell. Polar +spines conical, very stout, longer than the main axis, its base equals +one-third of the minor axis. + +_Dimensions._--Major axis of the cortical shell 0.1, shorter axis 0.08; +pores 0.004 to 0.002, bars 0.001; diameter of the medullary shell 0.04; +polar spines--length 0.12, thickness 0.03. + +_Habitat._--Central area of the Pacific, Station 271, depth 2425 fathoms. + + +14. _Lithatractus gamoporus_, n. sp. + +Outer shell thorny, thick walled, with irregular network; pores roundish, +of unequal size, so irregularly distributed in polygonal groups that in +every group two to six pores (commonly three to four) are near together; +the groups are separated by broader bars. On the half equator {324}six to +eight groups and eighteen to twenty-four pores. Proportion of the longer +axis to the shorter = 6 : 5. Shorter axis equals twice the diameter of the +inner ellipsoidal shell. Polar spines three-sided pyramidal, about as long +as the equatorial axis, as broad at the base as a group of pores. + +_Dimensions._--Major axis of the cortical shell 0.12, minor axis 0.1; pores +0.004 to 0.012, bars 0.003; length of the polar spines 0.1, basal breadth +0.03. + +_Habitat._--Central area of the Pacific, Stations 271 to 274, depth 2350 to +2750 fathoms. + + + +Genus 138. _Druppatractus_,[177] n. gen. + +_Definition._--#Druppulida# with simple ellipsoidal cortical shell and +simple medullary shell, with two large opposite polar spines in the main +axis of different size or dissimilar form. + +The genus _Druppatractus_ differs from its near relation _Lithatractus_ in +the differentiation of the two polar spines, which are different in size or +form, often to a very considerable degree. It has therefore the same +relation to the latter that _Ellipsoxiphus_ bears to _Ellipsostylus_. + + + +Subgenus 1. _Druppatractara_, Haeckel. + +_Definition._--Network of the cortical shell regular or subregular, with +meshes of nearly equal size and similar form; surface smooth, without +thorns or papillae. + + +1. _Druppatractus ichthydium_, n. sp. + +Cortical shell thin walled, with smooth surface and regular network. +Proportion of the major axis to the minor = 3 : 2. Pores circular, +hexagonally framed, twice as broad as the bars; seven to eight on the half +equator (as in _Xiphostylus alcedo_, Pl. 13, fig. 4). Medullary shell +spherical, one-third as broad as the cortical shell. Polar spines straight, +three-sided pyramidal, as broad at the base as one mesh; the longer equals +the main axis of the cortical shell, the shorter only its half. + +_Dimensions._--Major axis of the ellipsoidal cortical shell 0.18, minor +axis 0.12; pores 0.01, bars 0.005; diameter of the medullary shell 0.04; +length of the major polar spine 0.16 to 0.2, of the minor 0.01 to 0.12, +basal breadth 0.01. + +_Habitat._--Mediterranean (Corfu), surface, Haeckel. + + +2. _Druppatractus hippocampus_, n. sp. (Pl. 16, figs. 10, 11). + + _Stylosphaera hippocampus_, Haeckel, 1881, Atlas, pl. xvi. figs. 10, 11. + +Cortical shell thick walled, with smooth surface and regular network. +Proportion of both axes = 7 : 6. Pores circular, hexagonally lobed, three +times as broad as the bars; nine to ten on the half {325}equator. Medullary +shell ellipsoidal, nearly half as large as the cortical. Larger polar spine +horn-like curved, as long as the main axis, smaller scarcely half as long, +pommel-shaped. + +_Dimensions._--Major axis 0.09, minor 0.075; pores 0.01, bars 0.003; axes +of the medullary shell 0.04 and 0.03; length of the larger polar spine 0.06 +to 0.09, of the smaller 0.04, basal breadth 0.02. + +_Habitat._--Pacific, central area, Stations 270 to 272, surface. + + +3. _Druppatractus belone_, n. sp. + +Cortical shell thin walled, with smooth surface and regular network. +Proportion of both axes = 4 : 3. Pores circular, twice as broad as the +bars; ten to twelve on the half equator. Medullary shell spherical, +one-third as broad as the cortical shell. Polar spines strong, straight, +cylindrical, with conical apex, as broad at the base as two pores; the +larger once and a half to twice as long as the main axis, the smaller only +one-third to one-fourth as long. + +_Dimensions._--Major axis 0.1 to 0.12, minor 0.08 to 0.09; pores 0.008, +bars 0.004; diameter of the medullary shell 0.03; length of the larger +polar spine 0.15 to 0.2, of the minor 0.04 to 0.05, basal thickness of them +0.02. + +_Habitat._--Cosmopolitan; Atlantic, Indian, and Pacific, surface. + + +4. _Druppatractus testudo_, Haeckel. + + _Stylosphaera testudo_, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. + Berlin, p. 299, Taf. viii. fig. 16. + +Cortical shell thick walled, spindle-shaped, with smooth surface and +regular network. Proportion of the two axes = 3 : 2. Pores circular, five +times as broad as the bars; only six to seven on the half equator. +Medullary shell ellipsoidal, about one-third as large as the cortical +shell. Polar spines strong, short, three-sided pyramidal; the larger as +long as half the transverse axis, the smaller only one-fourth as long. + +_Dimensions._--Major axis 0.12, minor 0.8; pores 0.015, bars 0.003; axes of +the medullary shell 0.04 and 0.03; length of the larger polar spine 0.04, +of the smaller 0.02, basal thickness 0.01. + +_Habitat._--Pacific, Philippine and Californian Sea (Ehrenberg), Stations +244, 266, 289, &c., depth 2550 to 2900 fathoms. + + + +Subgenus 2. _Druppatractylis_, Haeckel. + +_Definition._--Network of the cortical shell regular or subregular, with +meshes of nearly equal size and similar form; surface thorny or papillose, +covered with small conical spines or tubercles. + + +5. _Druppatractus accipenser_, n. sp. + +Cortical shell thick walled, thorny, with regular network. Proportion of +the two axes = 6 : 5. Pores circular, each with a six-lobed outer opening, +funnel-shaped, twice as broad as the bars; nine {326}to ten on the half +equator. Medullary shell spherical, one-third as broad as the cortical +shell. Polar spines very strong, three-sided pyramidal, as broad at the +base as three pores; the larger about as long as the main axis, the smaller +only one-third as long. + +_Dimensions._--Major axis 0.12, minor 0.1; pores 0.01, bars 0.005; +medullary shell 0.035; length of the larger polar spine 0.11, of the +smaller 0.04, basal breadth 0.03. + +_Habitat._--Indian Ocean, Madagascar, surface, Rabbe. + + +6. _Druppatractus ostracion_, n. sp. (Pl. 16, figs. 8, 9). + +Cortical shell thick walled, thorny, with regular network. Proportion of +the two axes = 4 : 3. Pores circular, hexagonally framed, three to four +times as broad as the crested bars; from every corner of the hexagon +(between three meshes) arises a short papilla; the bottom of every +funnel-like mesh is closed by a very thin plate with three regular, +circular pores (occasionally four), sometimes confluent, at other times +separate. Medullary shell (fig. 9) half as large as the cortical, +ellipsoidal and papillate, with regular, circular pores. Polar spines very +strong, three-sided prismatic, often somewhat irregular, with short apex; +the larger once to twice as long as the main axis, the smaller scarcely +half as long. + +_Dimensions._--Major axis 0.16, minor 0.12; pores 0.02 (porules at their +base 0.01), bars 0.006; axes of the medullary shell 0.07 and 0.06, its +pores 0.01, bars 0.003; length of the larger polar spine 0.15 to 0.3, of +the smaller 0.07 to 0.09, basal thickness 0.03. + +_Habitat._--Pacific, central area, Station 265, depth 2900 fathoms. + + +7. _Druppatractus coronatus_, Haeckel. + + _Stylosphaera coronata_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. + Berlin, p. 84, Taf. xxv. fig. 4. + +Cortical shell thick walled, thorny, with regular network. Proportion of +the two axes = 5 : 4. Pores circular, simple, twice as broad as the bars; +eight to ten on the half equator. Medullary shell circular, one-third as +broad as the cortical shell. Polar spines furrowed and angular; the longer +and thinner pyramidal about as long as the main axis, the shorter and +thicker scarcely half as long, thickened towards the short conical apex. + +_Dimensions._--Major axis 0.08 to 0.1, minor 0.06 to 0.08; pores 0.01, bars +0.005; diameter of the medullary shell 0.03; length of the large polar +spine 0.08 to 0.12, of the shorter 0.04 to 0.05. + +_Habitat._--Fossil in the Tertiary rocks of Barbados; also living in the +depths of the Pacific, central area, Stations 265 to 268, depth 2700 to +2900 fathoms. + + + +Subgenus 3. _Druppatractona_, Haeckel. + +_Definition._--Network of the cortical shell irregular, with meshes of +unequal size or dissimilar form; surface smooth, without thorns or +papillae. + + +{327}8. _Druppatractus laevis_, Haeckel. + + _Stylosphaera laevis_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. + Berlin, p. 84, Taf. xxv. fig. 6. + +Cortical shell thin walled, smooth, with irregular network. Proportion of +the two axes = 3 : 2. Pores roundish or subcircular, of different size, +one-half to twice as broad as the bars; eight to ten on the half equator. +Medullary shell ellipsoidal, one-third as large as the cortical shell. +Polar spines conical, the larger and thinner nearly as long as the main +axis, the shorter and thicker scarcely one-third as long. + +_Dimensions._--Major axis 0.07 to 0.1, minor 0.05 to 0.07; pores and bars +0.005 to 0.01; axes of the medullary shell 0.03 and 0.02; length of the +major polar spine 0.06 to 0.09, of the shorter 0.03 to 0.04. + +_Habitat._--Cosmopolitan; Atlantic, Indian, Pacific, surface. + + +9. _Druppatractus xiphias_, n. sp. + +Cortical shell thick walled, smooth, with irregular network. Proportion of +the two axes = 6 : 5. Pores funnel-shaped, composed of two to four +confluent smaller porules, twice to four times as broad as the bars; ten to +twelve on the half equator. Medullary shell spherical, half as broad. Polar +spines three-sided pyramidal, the larger about as long as the main axis, +the shorter one-third to one-half as long. + +_Dimensions._--Major axis 0.12, minor 0.1; pores 0.012 to 0.018, bars +0.004; diameter of the medullary shell 0.05; length of the major polar +spine 0.1, of the minor 0.03 to 0.05. + +_Habitat._--Pacific, central area, Station 268, depth 2900 fathoms. + + + +Subgenus 4. _Druppatractium_, Haeckel. + +_Definition._--Network of the cortical shell irregular, with meshes of +unequal size or dissimilar form; surface thorny or papillose, covered with +small spines or tubercles. + + +10. _Druppatractus diodon_, n. sp. + +Cortical shell thin walled, thorny, with irregular network. Proportion of +the two axes = 5 : 4. Pores simple, irregular, roundish, twice to four +times as broad as the bars; eight to ten on the half equator. Medullary +shell spherical, half as broad. Polar spines conical, more or less curved; +the major longer than the main axis, the minor scarcely half as long. +(Resembles _Sphaerostylus ophidium_, Pl. 16, figs. 14, 15, but differs from +it in the prolongation of the main axis.) + +_Dimensions._--Major axis 0.15, minor 0.12; pores 0.01 to 0.02, bars 0.005; +diameter of the medullary shell 0.06; length of the larger polar spine 0.12 +to 0.18, of the shorter 0.06 to 0.08, basal thickness 0.003. + +_Habitat._--Pacific, central area, Station 274, surface. + + +{328}11. _Druppatractus pisciculus_, n. sp. + +Cortical shell thick walled, spiny, with irregular network. Proportion of +the two axes = 3 : 2. Pores irregular, roundish, lobed, or composed of +three to five confluent porules, twice to six times as broad as the bars; +six to eight on the half equator. (Similar to _Ellipsoxiphus atractus_, Pl. +14, fig. 1.) Medullary shell ellipsoidal, nearly half as large as the +cortical shell. Polar spines three-sided pyramidal, the major longer than +the main axis, the minor scarcely one-third to one-fourth as long. + +_Dimensions._--Major axis 0.18, minor 0.12; pores 0.01 to 0.03, bars 0.004; +axes of the medullary shell 0.08 and 0.05; length of the major polar spine +0.2, of the minor 0.05, basal breadth 0.02. + +_Habitat._--South Atlantic, Station 332, depth 2200 fathoms. + + + +Genus 139. _Stylatractus_,[178] n. gen. + +_Definition._--#Druppulida# with simple ellipsoidal cortical shell and +double medullary shell, in the main axis with two large opposite polar +spines of equal size and similar form. + +The genus _Stylatractus_ differs from _Lithatractus_ in the double +medullary shell, from _Amphisphaera_ in the ellipsoidal form of the +cortical shell. As in these two genera, both opposite polar spines have the +same shape and size. + + + +Subgenus 1. _Stylatractara_, Haeckel. + +_Definition._--Network of the cortical shell regular or subregular, with +meshes of nearly equal size and similar form; surface smooth, without +thorns or papillae. + + +1. _Stylatractus neptunus_, n. sp. (Pl. 17, fig. 6). + + _Amphistylus neptunus_, Haeckel, 1878, Atlas, pl. xvii. fig. 6. + +Cortical shell thick walled, smooth, with subregular, circular, polygonally +framed pores, quite as broad as the bars; ten to twelve on the half +equator. Polar spines three-sided pyramidal, about as long as the half main +axis, three times as broad at the base as the pores. (Much resembles +_Amphisphaera neptunus_, p. 142, but differs from it by the prolongation of +the main axis, which equals one and a half or one and a fourth the +equatorial axis, and by the somewhat irregular formation of the cortical +hexagonal network. Sometimes also, as in the figured specimen, the length +of both polar spines is somewhat different.) + +_Dimensions._--Major axis of the cortical shell 0.15, minor axis 0.12; +pores and bars 0.007; main axes of both ellipsoidal medullary shells 0.08 +and 0.05; length of the polar spines 0.08 to 0.1, basal breadth 0.02. + +_Habitat._--Pacific, central area, Stations 266 to 268, depth 2700 to 2900 +fathoms. + + +{329}2. _Stylatractus fusiformis_, n. sp. + +Cortical shell thick walled, smooth, with regular, simple, circular pores, +quite as broad as the bars; fourteen to sixteen on the half equator. Polar +spines three-sided pyramidal, half as long as the main axis, as broad at +the base as the inner medullary shell. (Resembles very nearly _Xiphatractus +armadillo_, Pl. 17, fig. 11, but differs in the regular form and equal +length of the polar spines.) + +_Dimensions._--Major axis 0.17, minor axis 0.13; pores and bars 0.007; main +axes of both ellipsoidal medullary shells 0.09 and 0.05; length of the +polar spines 0.08, basal breadth 0.04. + +_Habitat._--Cosmopolitan; Atlantic, Indian, Pacific, at various depths. + + +3. _Stylatractus compactus_, n. sp. (Pl. 17, fig. 4). + +Cortical shell thick walled, smooth, with subregular, circular, +double-contoured pores, smaller than the bars; sixteen to eighteen on the +half equator. The thickness of the shell-wall equals the radius of the +inner medullary shell. Polar spines short, three-sided pyramidal; their +length and basal thickness variable, but commonly equal to the diameter of +the inner medullary shell. + +_Dimensions._--Major axis 0.16, minor axis 0.13; pores 0.007, bars 0.01; +main axes of both ellipsoidal medullary shells 0.09 and 0.04; length and +basal breadth of the polar spines 0.04 to 0.05. + +_Habitat._--Pacific, central area, Stations 270 to 272, depth 2425 to 2925 +fathoms. + + + +Subgenus 2. _Stylatractylis_, Haeckel. + +_Definition._--Network of the outer shell regular, with meshes of equal +size and similar form; surface thorny or papillose, covered with small +spinules or tubercles. + + +4. _Stylatractus giganteus_, n. sp. (Pl. 17, fig. 1). + + _Amphistylus giganteus_, Haeckel, 1879, Atlas (pl. xvii. fig. 1). + +Cortical shell papillose, very thick walled, with regular network; pores +circular, with double margin, about twice as broad as the bars; ten to +twelve on the half equator. The cortical shell is connected with the outer +medullary shell by numerous strong beams, and the inner prolongations of +both polar spines are much stronger. The circular pores of the outer +medullary shell are three times as large as those of the inner, and equal +to those of the cortical shell, but the bars are much thinner. Polar spines +very strong, three-sided pyramidal, with spirally contorted edges, as long +as the main axis, as broad at the base as the inner medullary shell. + +_Dimensions._--Major axis of the cortical shell 0.3, minor axis 0.22; pores +0.02, bars 0.01; main axes of the ellipsoidal medullary shells 0.14 and +0.07; length of the polar spines 0.3, basal thickness 0.06. + +_Habitat._--Western Tropical Pacific, Station 225, depth 4475 fathoms. + + +{330}5. _Stylatractus carduus_, Haeckel. + + _Stylosphaera carduus_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. + Berlin, p. 84, Taf. xxv. fig. 7. + +Cortical shell thin walled, spiny, with regular, circular pores, five times +as broad as the bars; ten to twelve on the half equator. Polar spines +conical, half as long as the main axis, at the base broader than the pores. +(The cortical shell is ellipsoidal as well as both medullary shells; the +figure of Ehrenberg, as is generally the case, is more correct than his +description. This interesting species occurs in the Barbados rocks, with +double as well as with simple medullary shell, and may in the latter case +be distinguished as _Lithatractus carduelis_.) + +_Dimensions._--Major axis of the cortical shell 0.12 to 0.16, minor 0.1 to +0.14; pores 0.01 to 0.02, bars 0.002 to 0.005; main axes of the ellipsoidal +medullary shells 0.05 and 0.03; length of the polar spines 0.06, basal +breadth 0.02. + +_Habitat._--Fossil in the Tertiary rocks of Barbados. + + + +Subgenus 3. _Stylatractona_, Haeckel. + +_Definition._--Network of the outer shell irregular, with meshes of +different size or form; surface smooth, without thorns or papillae. + + +6. _Stylatractus variabilis_, n. sp. + +Cortical shell thin walled, smooth, with irregular, roundish pores, twice +to six times as broad as the bars; twelve to sixteen on the half equator. +Polar spines conical, about half as long as the main axis, and as broad at +the base as the inner medullary shell. (The size and form of the pores and +of the polar spines in this species are very variable, so that the +proportions given are to be understood as averages.) + +_Dimensions._--Major axis 0.13, minor axis 0.11; pores 0.004 to 0.012, bars +0.002; main axes of the ellipsoidal medullary shells 0.07 and 0.04; length +of the polar spines 0.06, basal breadth 0.03. + +_Habitat._--Pacific, central area. Stations 272 to 274, depth 2350 to 2750 +fathoms. + + +7. _Stylatractus sethoporus_, n. sp. (Pl. 17, figs. 2, 3). + +Cortical shell thick walled, smooth, with large irregular, roundish pores, +twice to four times as broad as the bars; seven to eight on the half +equator. At the bottom of each pore a thin lamella of silex, perforated by +four to six irregular, roundish, double-contoured porules. Medullary shells +resemble those of _Stylatractus giganteus_. Polar spines three-sided +pyramidal; their length and basal thickness scarcely equal the diameter of +the inner medullary shell. + +_Dimensions._--Major axis 0.15, minor axis 0.13; pores 0.02, bars 0.005, +porules 0.01; length of the polar spines 0.04. + +_Habitat._--Pacific, central area, Station 272, depth 2600 fathoms. + + + +{331}Subgenus 4. _Stylatractium_, Haeckel. + +_Definition._--Network of the outer shell irregular, with meshes of +different size and form; surface thorny or papillose, covered with small +spinules or tubercles. + + +8. _Stylatractus papillosus_, n. sp. + +Cortical shell thin walled, with papillose surface, and irregular, simple, +roundish pores, ten to sixteen on the half equator, twice to three times as +broad as the bars. Conical papillae of the surface irregularly scattered. +Polar spines conical, about as long as the main axis, at the base half as +broad as the inner medullary shell. + +_Dimensions._--Major axis 0.12, minor 0.1; pores 0.006 to 0.01, bars 0.003; +main axes of the medullary shells 0.09 and 0.06; length of the polar spines +0.13, basal breadth 0.04. + +_Habitat._--Indian Ocean, surface (between Socotra and Ceylon), Haeckel. + + +9. _Stylatractus disetanius_, n. sp. + +Cortical shell thin walled, with spiny surface, and irregular, roundish +pores, eight to ten on the half equator, twice to three times as broad as +the bars. Every pore is divided by thinner bars into four to six small +roundish porules. Polar spines three-sided pyramidal, nearly as long as the +main axis, as broad at the base as the inner medullary shell. (Resembles +_Xiphatractus glyptodon_, Pl. 17, figs. 9, 10, but differs from it by the +irregular network and the equal size of both polar spines.) + +_Dimensions._--Major axis 0.14, minor 0.1; pores 0.02, bars 0.008, porules +0.007; main axes of the two medullary shells 0.08 and 0.05; length of the +polar spines 0.13, basal breadth 0.04. + +_Habitat._--South Pacific, near New Zealand, Station 169, surface. + + + +Genus 140. _Xiphatractus_,[179] n. gen. + +_Definition._--#Druppulida# with a simple ellipsoidal cortical shell and +double medullary shell, in the main axis with two large opposite polar +spines of different size or form. + +The genus _Xiphatractus_ differs from the nearly related _Stylatractus_ in +the differentiation of two polar spines (in the same manner as +_Druppatractus_ differs from _Lithatractus_). From the spherical +_Amphistylus_ it differs in the ellipsoidal form of the cortical shell. + + + +Subgenus 1. _Xiphatractara_, Haeckel. + +_Definition._--Network of the cortical shell regular or subregular, with +meshes of nearly equal size and similar form; surface smooth, without +thorns or papillae. + + +{332}1. _Xiphatractus armadillo_, n. sp. (Pl. 17, fig. 11). + +Cortical shell thick walled, smooth, with regular, circular pores, about as +broad as the bars; fifteen to sixteen on the half equator. Polar spines +three-sided pyramidal, with thick, prominent edges, of irregular form; the +longer about as long as the main axis, the shorter scarcely one-third as +long; their basal breadth equals the diameter of the inner medullary shell. + +_Dimensions._--Major axis of the cortical shell 0.13, minor axis 0.1, +thickness of its wall 0.01; pores and bars 0.005; main axes of the two +medullary shells 0.07 and 0.03; length of the major polar spine 0.12, of +the minor 0.04, basal thickness 0.04. + +_Habitat._--Pacific, central area, Station 272, depth 2600 fathoms. + + +2. _Xiphatractus euphractus_, n. sp. + +Cortical shell thick walled, smooth, with regular, circular pores, twice as +broad as the bars; eight to nine on the half equator. Each pore has six to +nine excisions (commonly eight), elegantly lobed, flower-like (as in +_Xiphostylus phasianus_, Pl. 13, fig. 9). Polar spines strong, angulate; +the major pyramidal, longer than the main axis, the shorter elegantly +pommel-like, scarcely one-third as long. + +_Dimensions._--Major axis 0.15, minor 0.12; pores 0.014, bars 0.007; main +axes of the two medullary shells 0.09 and 0.05; length of the larger polar +spine 0.16, of the shorter 0.05, greatest thickness 0.03. + +_Habitat._--South Atlantic, Station 332, depth 2200 fathoms. + + + +Subgenus 2. _Xiphatractylis_, Haeckel. + +_Definition._--Network of the cortical shell regular or subregular, with +meshes of nearly equal size and similar form; surface thorny or papillose. + + +3. _Xiphatractus spinulosus_, Haeckel. + + _Stylosphaera spinulosa_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. + Berlin, p. 84, Taf. xxv. fig. 8. + +Cortical shell thin walled, with spiny surface, and large, regular, +circular pores, four times as broad as the bars; seven to eight on the half +equator. Spines between the pores of the same size, conical. Polar spines +also conical, but much larger; the major about as long as the main axis, +the minor scarcely half as long; their basal thickness equals the largest +pores. + +_Dimensions._--Major axis 0.1, minor 0.08; pores 0.012, bars 0.003; +diameter of the spherical medullary shells 0.06 and 0.03; length of the +major polar spine 0.09, of the minor 0.04, basal thickness 0.02. + +_Habitat._--Fossil in the Tertiary rocks of Barbados. + + +{333}4. _Xiphatractus sulcatus_, Haeckel. + + _Stylosphaera sulcata_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. + Berlin, p. 84, Taf. xxiv, fig. 6. + +Cortical shell thick walled, with thorny surface, and regular, circular +pores, quite as broad as the bars; nine to ten on the half equator. Polar +spines cylindrical, with longitudinal basal furrows and conical apex, three +times as broad as the pores; the larger about as long as the main axis, the +shorter only one-half or two-thirds as long. + +_Dimensions._--Major axis 0.01, minor 0.08; pores and bars 0.007; main axes +of the two medullary shells 0.08 and 0.04; length of the major polar spine +0.1, of the minor 0.06, breadth of them 0.02. + +_Habitat._--Fossil in the Barbados deposits. + + +5. _Xiphatractus dasypus_, n. sp. + +Cortical shell thick walled, with spiny surface, and regular, elegant +network; pores circular, hexagonally framed, about as broad as the bars; +from every corner of the network (between three pores) arises a short +bristle-like spine. Polar spines three-sided prismatic, as broad as one +hexagon; the major once to twice as long as the main axis, the minor only +one-half to one-fourth as long. (The cortical shell much resembles +_Ellipsoxiphus elegans_, Pl. 14, fig. 7.) + +_Dimensions._--Major axis 0.15, minor 0.13; pores and bars 0.01; main axes +of the two medullary shells 0.1 and 0.06; length of the major polar spine +0.1 to 0.3, of the minor 0.05 to 0.1, thickness 0.01. + +_Habitat._--Tropical Western Pacific, Station 222, surface. + + + +Subgenus 3. _Xiphatractona_, Haeckel. + +_Definition._--Network of the cortical shell irregular, with meshes of +different size or form; surface smooth, without thorns or papillae. + + +6. _Xiphatractus chlamydophorus_, n. sp. + +Cortical shell thin walled, smooth, with irregular, roundish pores, twice +to four times as broad as the bars; eight to twelve on the half equator. +Polar spines angular, irregularly curved or contorted; the larger once to +twice as long as the main axis, the shorter and thicker pommel-shaped, only +one-third to one-half as long; their basal breadth equals two pores. + +_Dimensions._--Major axis 0.14, minor 0.1; pores 0.006 to 0.012, bars +0.003; main axis of the two ellipsoidal medullary shells 0.09 and 0.04; +length of the major polar spine 0.1 to 0.2, of the minor 0.05 to 0.08, +breadth 0.02. + +_Habitat._--Cosmopolitan; Atlantic, Pacific, many Stations, surface. + + + +{334}Subgenus 4. _Xiphatractium_, Haeckel. + +_Definition._--Network of the cortical shell irregular, with meshes of +unequal size or dissimilar form; surface thorny or papillose. + + +7. _Xiphatractus radiosus_, Haeckel. + + _Stylosphaera radiosa_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. + Berlin, p. 84, Taf. xxiv. fig. 5. + +Cortical shell very thick walled, with thorny surface, and irregular, +roundish pores, once to three times as broad as the bars; nine and ten on +the half equator. Polar spines conical, on the base about as broad as the +largest pores; the larger as long as the main axis, the smaller scarcely +one-fourth as long. (The radial striation, figured by Ehrenberg and applied +to the name of this species, is produced by the contours of the +funnel-shaped pores in the thick walls seen in optical section; the +ellipsoidal cortical shell is double.) + +_Dimensions._--Major axis 0.13, minor 0.09; pores 0.003 to 0.01, bars +0.003; main axes of the two medullary shells 0.05 and 0.03; length of the +major polar spine 0.12, of the minor 0.03, basal breadth 0.01. + +_Habitat._--Fossil in the Tertiary rocks of Barbados. + + +8. _Xiphatractus glyptodon_, n. sp. (Pl. 17, figs. 9, 10). + +Cortical shell thick walled, covered with radial spines of the size of the +pores; on the half equator eight to ten irregular or subregular roundish +pores, twice to four times as broad as the bars. In the bottom of each pore +a thin lamella of silex, perforated by four to six smaller roundish pores. +Both medullary shells (fig. 10) spherical, with smaller, regular, circular +pores. Larger polar spine three-sided pyramidal, in length equals the main +axis; shorter spine only half as long, but twice as thick, of elegant +pommel-form (fig. 9), with nine prominent edges. + +_Dimensions._--Major axis 0.12, minor, 0.1; pores and spines 0.01 to 0.02, +bars and porules 0.005; diameter of the two medullary shells 0.05 and 0.02; +length of the major polar spine 0.1, of the minor 0.06, greatest thickness +0.04. + +_Habitat._--Pacific, central area, Station 263, surface. + + + +Genus 141. _Cromyatractus_,[180] n. gen. + +_Definition._--#Druppulida# with four or more concentric shells (two +medullary shells and two or more cortical shells), in the main axis with +two large opposite polar spines of equal size and similar form. + +The genus _Cromyatractus_ is very nearly allied to all the foregoing +genera, which bear two equal spines opposite to one another on the poles of +the main axis; it differs {335}from them in the multiplication of the +cortical shell, and may be considered as the most highly developed form of +this amphistylous series, which proceeds from _Ellipsoxiphus_ to +_Lithatractus_ and _Stylatractus_. + + + +Subgenus 1. _Cromyatractium_, Haeckel. + +_Definition._--Shell composed of two medullary shells and two cortical +shells. + + +1. _Cromyatractus tetraphractus_, n. sp. (Pl. 15, fig. 2). + + _Stylocromium tetraphractum_, Haeckel, 1879, Atlas (pl. xv. fig. 2). + +Proportion of the main axes of the four concentric shells about = +1 : 3 : 5 : 7. Network of all four shells nearly of the same structure, +subregular, with circular pores of equal size (in one and the same shell). +The absolute size of the pores increases gradually from the innermost to +the outermost shell. The bars between the pores are smaller and quite +smooth. Surface of the outermost shell smooth. Polar spines cylindrical, +with conical apex, of variable length, nearly as broad as the innermost +shell. + +_Dimensions._--Main axes of the four shells--(A) inner medullary shell +0.03, (B) outer medullary shell 0.08, (C) inner cortical shell 0.15, (D) +outer cortical shell 0.2; equatorial axes of them--(A) 0.025, (B) 0.06, (C) +0.12, (D) 0.15; pores of (A) 0.004, (B) 0.007, (C) 0.01, (D) 0.013, bars +0.002 to 0.004; length of the polar spines 0.1 to 0.3 (and more), breadth +0.015. + +_Habitat._--Antarctic (Indian) Ocean, Station 157, depth 1950 fathoms. + + +2. _Cromyatractus tetralepas_, n. sp. + +Proportion of the main axes of the four concentric shells about = +1 : 2 : 4 : 6. Network of the two medullary shells regular, with small +circular pores, little larger than the bars. Network of the two cortical +shells irregular, with much larger polygonal pores, three to nine times as +broad as the thin bars. (Somewhat similar to _Cromyatractus ceparius_, Pl. +15, fig. 4.) Surface of the outermost shell smooth or a little thorny. +Polar spines cylindrical, very large, twice to three times as long as the +main axis of the outermost shell, about as broad as the innermost shell, +with conical apex; smooth or a little thorny. + +_Dimensions._--Main axes of the four shells--(A) 0.03, (B) 0.05, (C) 0.13, +(D) 0.18; equatorial axes of them--(A) 0.2, (B) 0.45, (C) 0.11, (D) 0.14; +pores of the two medullary shells 0.004 and 0.006, of both cortical shells +0.01 to 0.03, bars 0.003. + +_Habitat._--Indian Ocean, Zanzibar, Pullen, 2200 fathoms. + + +3. _Cromyatractus tetracelyphus_, n. sp. (Pl. 15, figs. 1, 1_a_). + +Proportion of the main axes of the four concentric shells about = +1 : 3 : 10 : 11. Network of the two spherical medullary shells (fig. 1_a_) +regular, with small circular pores, twice as broad as {336}the bars. +Network of the inner cortical shell regular with circular, +hexagonally-framed pores, twice as broad as the bars. From every corner of +the hexagons (between three pores) arises a very thin, hair-like, short +radial spinule. These spinules communicate with one another by tangential +branches (at equal distances from the inner cortical shell), and form +thereby an outer, delicate cortical network, with large polygonal meshes +and very thin bars. Polar spines very strong, pyramidal, with prominent +edges, as long as the main radius of the cortical shell, and half as broad +at the base. + +_Dimensions._--Main axes of the four shells--(A) 0.02, (B) 0.06, (C) 0.2, +(D) 0.22; equatorial axes of them--(A) 0.02, (B) 0.06, (C) 0.13, (D) 0.15; +pores of the four shells--(A) 0.002, (B) 0.004, (C) 0.008, (D) 0.02; bars +0.001 to 0.003; length of the polar spines 0.1, basal breadth 0.05. + +_Habitat._--South Atlantic, Station 335, depth 1425 fathoms. + + + +Subgenus 2. _Caryatractus_, Haeckel. + +_Definition._--Shell composed of two medullary shells and three or more +cortical shells. + + +4. _Cromyatractus cepicius_, n. sp. (Pl. 15, fig. 3). + + _Caryostylus cepicius_, Haeckel, 1879, Atlas (pl. xv. fig. 3). + + _Caryodoras cepicius_, Haeckel, 1881, Prodromus, p. 454. + +Proportion of the main axes of the five concentric shells about = +1 : 2 : 5 : 7 : 8. Network of both spherical medullary shells regular, with +small circular pores, about as broad as the bars. Network of the three +ellipsoidal cortical shells irregular, with large polygonal meshes, five to +ten times as broad as the thin bars. Surface of the outermost shell smooth. +Polar spines cylindrical, thorny, about as thick as the innermost shell and +as long as the outermost shell, against the apex with a spindle-like +intumescence, formed by delicate spongy framework (fig. 3). + +_Dimensions._--Main axes of the five concentric shells--(A) 0.03, (B) 0.05, +(C) 0.16, (D) 0.2, (E) 0.25; equatorial axes of them--(A) 0.03, (B) 0.05, +(C) 0.12, (D) 0.16, (E) 0.2; pores of the two medullary shells 0.002 to +0.004, of the three cortical shells 0.02 to 0.04, bars 0.002; length of the +polar spines 0.3, breadth 0.03. + +_Habitat._--Pacific, central area, Station 268, depth 2900 fathoms. + + +5. _Cromyatractus ceparius_, n. sp. (Pl. 15, fig. 4). + + _Caryostylus ceparius_, Haeckel, 1881, Prodromus et Atlas (pl. xv. fig. + 4). + +Proportion of the main axes of the six concentric shells about = +1 : 2 : 7 : 10 : 13 : 18. Network of the three inner shells regular, with +small, circular pores, which are about as broad as the bars and in the +third shell hexagonally framed. Network of the three outer shells +irregular, with large polygonal meshes, six to twelve times as broad as the +bars. Surface smooth. Polar spines strong, spindle-shaped, thorny, outside +of the sixth shell about as long as inside of it; broader than {337}the +innermost shell; the thorns of their outer free part (arising at equal +distances) represent perhaps the beginnings of three to four further +shells. + +_Dimensions._--Main axes of the six concentric shells--(A) 0.02, (B) 0.05, +(C) 0.14, (D) 0.2, (E) 0.26, (F) 0.37; equatorial axes--(A) 0.02, (B) 0.05, +(C) 0.09, (D) 0.15, (E) 0.21, (F) 0.3; pores of the three inner shells +0.003 to 0.006, of the three outer shells 0.02 to 0.04, bars 0.003 to +0.005; length of the polar spines, from the base of the innermost shell to +the apex, 0.35, greatest breadth 0.03. + +_Habitat._--South Pacific, Station 285, depth 2375 fathoms. + + + +Genus 142. _Pipetta_,[181] n. gen. + +_Definition._--#Druppulida# with simple ellipsoidal cortical shell and +simple medullary shell, with two hollow fenestrated tubes opposite on both +poles of the main axis. + +The genus _Pipetta_ differs from _Pipettella_ (p. 304) in the possession of +an inner (medullary) shell; it exhibits the same tubular prolongations of +the cortical shell at both poles of the main axis. + + +1. _Pipetta fusus_, n. sp. (Pl. 39, figs. 8, 8_a_). + +Cortical shell spindle-shaped, the middle ellipsoidal part gently passing +over on both poles into the conical tubes, which attain about the same +length. Network regular, with circular, hexagonally-framed pores, twice as +broad as the bars, sixteen to eighteen on the half equator. In the middle +part of the shell the pores arise from their hexagonal bases in the form of +short conical funnels; on both tubes they are much smaller and simple, +without frame. Medullary shell (fig. 8_a_) spherical, scarcely one-third as +broad as the cortical, with regular, circular pores, twice as broad as the +bars, eight to nine on the half equator. The two shells are connected only +by two opposite beams, lying in the equatorial axis and ramified at the +distal insertion (fig. 8_a_). + +_Dimensions._--Middle ellipsoidal part of the cortical shell 0.13 to 0.15; +polar tubes 0.15 long, 0.06 broad at the base; pores of the former 0.01, +bars 0.005; pores of the tubes 0.06, bars 0.003. Medullary shell 0.04, +pores 0.004, bars 0.002. + +_Habitat._--Pacific, central area, Station 268, depth 2900 fathoms. + + +2. _Pipetta tuba_, n. sp. (Pl. 39, fig. 7). + +Cortical shell nearly spherical in the middle part, which is sharply +separated at both poles from the long, nearly cylindrical tubes; these are +longer than the main axis, at the distal end open (always broken off). +Network regular, with circular, hexagonally-framed pores, of the same +breadth as the bars, eighteen to twenty on the half equator. The pores of +the polar tubes are of the same shape, only much smaller, and arranged in +sixteen to eighteen longitudinal rows. Medullary shell {338}spherical, +about one-third as broad as the cortical, with simple circular pores. The +connection between the two shells is only made by two simple opposite +beams, lying in the equatorial axis. + +_Dimensions._--Middle spheroidal part of the cortical shell 0.14 to 0.16; +polar tubes 0.15 to 0.2 or longer, 0.03 broad; pores and bars of the former +0.007, of the latter 0.003. Medullary shell 0.04, pores 0.006, bars 0.003. + +_Habitat._--Western Tropical Pacific, Station 225, depth 4475 fathoms. + + +3. _Pipetta salpinx_, n. sp. + +Cortical shell ellipsoidal, sharply separated from the cylindrical polar +tubes, which reach about the same length (or more). Network regular, with +circular pores, three times as broad as the bars, without hexagonal frames, +fourteen to fifteen on the half equator. Pores of the polar tubes smaller, +arranged in eight to ten longitudinal rows. Medullary shell spherical, +one-fourth as broad as the cortical, connected with it by a circle of four +to six radial beams, lying in the equatorial plane. Differs from +_Pipettella prismatica_ (Pl. 39, fig. 6) in the possession of a medullary +shell and the absence of the tube edges. + +_Dimensions._--Main axis of the ellipsoid 0.14, equatorial axis 0.12, pores +0.01, bars 0.003; length of the tubes 0.15 or more, breadth 0.03. Medullary +shell 0.03, pores 0.002, bars 0.001. + +_Habitat._--Pacific, central area, Stations 265 to 268, depth 2700 to 2900 +fathoms. + + +4. _Pipetta conus_, n. sp. + +Cortical shell spindle-shaped, the middle ellipsoidal part gently passing +over at both poles into the conical tubes, which attain only half its +length. Network irregular, with roundish or subcircular pores, twice to +three times as broad as the bars, twelve to sixteen on the half equator. +Medullary shell spherical, one-fourth as broad as the cortical. (Differs +from the foregoing species in the short conical tubes and the irregular +reticulation.) + +_Dimensions._--Middle part of the cortical shell 0.16 long, 0.13 broad; +tubes 0.09 long, 0.05 on the base broad; pores 0.005 to 0.01, bars 0.003. +Medullary shell 0.04. + +_Habitat._--North Pacific, Station 241, depth 2300 fathoms. + + + +Genus 143. _Pipettaria_,[182] n. gen. + +_Definition._--#Druppulida# with simple ellipsoidal cortical shell and +double medullary shell, with two hollow fenestrated tubes opposite on both +poles of the main axis. + +The genus _Pipettaria_ differs from the foregoing _Pipetta_ only in the +duplication of the medullary shell; as in this, the tubular prolongations +of the main axis of the cortical shell may be either conical (with closed +apex) or cylindrical (with apical opening?). + + +{339}1. _Pipettaria fusaria_, n. sp. + +Cortical shell spindle-shaped, the middle ellipsoidal part gently passing +over on both poles into the conical tubes, which attain about half its +length. Pores regular, circular, twice as broad as the bars, sixteen to +eighteen on the half equator; pores of the tubes smaller. Both medullary +shells spheroidal, compressed. (The appearance of the cortical shell +resembles that of _Cannartiscus amphiconus_, Pl. 39, fig. 19, but without +the equatorial constriction.) + +_Dimensions._--Main axis of the ellipsoid 0.15, equatorial axis 0.13; +length of the polar tubes 0.08, basal breadth 0.05; pores of the former +0.008, bars 0.004; diameter of the medullary shells 0.04 and 0.02. + +_Habitat._--South Pacific, Station 300, depth 1375 fathoms. + + +2. _Pipettaria tubaria_, n. sp. (Pl. 39, fig. 15). + + _Cannartidium tubarium_, Haeckel, 1882, Atlas (pl. xxxix. fig. 15). + +Cortical shell ellipsoidal, on both poles distinctly separated from the +short conical tubes, the length and breadth of which equal the outer +medullary shell. In the equatorial plane arises a circle of four to six +short conical protuberances, similar to the polar tubes. Pores subregular, +circular, or roundish, scarcely broader than the bars, sixteen to twenty on +the half equator. Both medullary shells spheroidal, somewhat compressed in +the direction of the two poles (as in fig. 18_a_). + +_Dimensions._--Main axis of the ellipsoid 0.12, equatorial axis 0.09; pores +0.005, bars 0.004; size of the equatorial protuberances and of the polar +tubes 0.02. + +_Habitat._--Pacific, central area, Station 265, depth 2900 fathoms. + + + +Family XIII. #SPONGURIDA#, Haeckel (Pl. 48, figs. 6, 7). + +_Spongurida_, Haeckel, 1862, Monogr. d. Radiol., p. 447 (_sensu emendato_). + +_Definition._--#Prunoidea# with spongy ellipsoidal or cylindrical shell, +composed wholly or partially of a spongy framework, without equatorial +stricture, with or without an enclosed medullary shell. + +The family #Spongurida# comprises, in the sense here restricted, all those +#Prunoidea# in which the ellipsoidal or cylindrical shell is composed +wholly or partially of an irregular siliceous framework, not of simple +lattice-work. It contains two subfamilies, differing in the absence or +presence of a latticed medullary shell in the middle of the central +capsule; in the Spongellipsida it is absent, in the Spongodruppida present; +the former are most nearly related to the Ellipsida, the latter to the +Druppulida, the difference consisting only in the spongy structure of the +cortical shell. + +In my Monograph (1862, p. 447) the family Spongurida had a much wider +extent, comprising also a number of #Sphaeroidea# and #Discoidea#, agreeing +in the spongy {340}structure of the shell. Here we restrict the definition +to those spongy #Sphaerellaria# in which the central capsule and the +enclosing spongy cortical shell are ellipsoidal or cylindrical, therefore +each transverse section is a circle, and each meridional section an +ellipse, as in all #Prunoidea#. + +_The Cortical Shell_ in all Spongurida is composed of a delicate framework +of irregularly branched and interwoven siliceous threads; commonly this +spongy structure is rather dense or compact, but sometimes also very loose. +In the simplest form, _Spongellipsis_, the spongy cortical shell contains a +large cavity, in which lies freely the central capsule. In _Spongurus_ this +cavity is completely distended by a spongy framework. In this case the +solid spongy shell becomes often prolonged, and its original ellipsoidal +form passes over into a cylindrical one (as in many Zygartida). Sometimes +(particularly in _Spongocore_, Pl. 48, fig. 6) the cylinder becomes +three-jointed by two more or less distinct annular constrictions. +_Spongocore_ is distinguished by an outer veil, a thin lattice-lamella, +which envelops the spongy shell and is connected with it by radial beams. + +_The Medullary Shell_, absent in the Spongellipsida, is constant in the +second subfamily Spongodruppida. It is either a simple latticed shell +(_Spongodruppa_) or double, composed of two concentric latticed shells +(_Spongoliva_); its form is either spherical or ellipsoidal. It lies in the +middle of the central capsule, and is connected by radial beams +(perforating the membrane of the latter) with the enveloping spongy +cortical shell. + +In many Spongurida the surface of the shell is armed with radial spines, +and in some genera (_Spongoprunum_, _Spongatractus_, &c., Pl. 17, fig. 12), +on both poles of the main axis, are developed two strong opposite polar +spines, as in many other #Prunoidea#. + +_The Central Capsule_ of the Spongurida is either ellipsoidal or +cylindrical. Only in _Spongellipsis_ it lies freely in the internal cavity +of the spongy shell. In all other genera it is perforated by a part of the +skeleton; in the Spongodruppida it contains the simple or double medullary +shell, and the radial beams which perforate its membrane and connect the +latter with the external spongy cortical shell. In _Spongurus_ and the +allied genera (_Spongocore_, _Spongoprunum_) the whole central capsule is +filled with a spongy framework which also envelops its surface. + +{341}_Synopsis of the Genera of Spongurida._ + + ------------------------------------------------------------------------- + I. Subfamily Spongellipsida. + (Ellipsoidal shell composed only of a spongy framework without a + latticed medullary shell in the centre.) + ------------------------------------------------------------------------- + Spongy shell }No polar spines, 144. _Spongellipsis_. + with internal } + cavity. } + + {Without lattice + Spongy shell { mantle. No polar + solid, without { spines, 145. _Spongurus_. + internal { + cavity. {With lattice + { mantle. + { No polar spines, 146. _Spongocore_. + { + {Without lattice + { mantle. Two + { opposite spines + { on the poles of + { the axis, 147. _Spongoprunum_ + ------------------------------------------------------------------------- + II. Subfamily Spongodruppida. + (Ellipsoidal shell composed of an outer spongy cortical shell and an + inner latticed medullary shell.) + ------------------------------------------------------------------------- + Medullary shell {No polar spines, 148. _Spongodruppa_. + simple. { + {Two opposite spines + { on the poles of + { the axis, 149. _Spongatractus_. + + Medullary shell {No polar spines, 150. _Spongoliva_. + double. { + { + {Two opposite spines + { on the poles of + { the axis, 151. _Spongoxiphus_. + + + +Subfamily 1. SPONGELLIPSIDA, Haeckel. + +_Definition._--#Spongurida# with a spongy ellipsoidal or cylindrical shell, +without an internal latticed medullary shell. + + + +Genus 144. _Spongellipsis_,[183] n. gen. + +_Definition._--#Spongurida# with an ellipsoidal or cylindrical spongy +shell, containing an internal cavity, without a latticed medullary shell. +Polar spines absent. + +The genus _Spongellipsis_ embraces those very simple Spongurida in which +the ellipsoidal central capsule is enclosed in a spongy cortical shell of +the same form. It corresponds, therefore, to _Plegmosphaera_ among the +#Sphaeroidea#, to _Plegmodiscus_ among the #Discoidea#, and to +_Spongolarcus_ among the #Larcoidea#. In some species the ellipsoidal form +is prolonged and passes into a cylindrical one. + + + +Subgenus 1. _Spongellipsarium_, Haeckel. + +_Definition._--Surface of the shell smooth or rough, without radial spines. + + +{342}1. _Spongellipsis laevis_, n. sp. + +Shell ellipsoidal, with smooth surface, its spongy wall scarcely one-tenth +as thick as the minor axis of the inner cavity. Spongy framework very +compact, with small meshes, three to six times as broad as the bars. +Proportion of the major axis to the minor = 3 : 2. + +_Dimensions._--Major axis (or length) of the shell 0.36, minor axis (or +breadth) 0.24. + +_Habitat._--Pacific, central area, Station 265, surface. + + +2. _Spongellipsis aspera_, n. sp. + +Shell ellipsoidal, with rough surface, its spongy wall nearly half as thick +as the minor axis of the inner cavity. Spongy framework very loose, with +large meshes, ten to twenty times as broad as the bars. Proportion of the +major axis to the minor = 4 : 3. + +_Dimensions._--Length of the shell 0.24, breadth 0.18. + +_Habitat._--North Pacific, Station 253, surface. + + +3. _Spongellipsis aplysina_, n. sp. + +Shell nearly cylindrical, with rough surface, its spongy wall about +one-fourth as thick as the minor axis of the internal cavity. Spongy +framework loose, with large meshes, four to eight times as broad as the +bars. Proportion of both axes = 6 : 1. (Similar to a spongy cylinder of +Aplysina.) + +_Dimensions._--Length of the shell 0.3, breadth 0.05. + +_Habitat._--North Atlantic, Station 64, surface. + + + +Subgenus 2. _Spongellipsidium_, Haeckel. + +_Definition._--Surface of the shell covered with radial spines. + + +4. _Spongellipsis setosa_, n. sp. + +Shell ellipsoidal, covered with numerous (sixty to eighty) thin, +bristle-shaped, radial spines, about half as long as the major axis. Spongy +framework loose, with large meshes, ten to twenty times as broad as the +bars. Minor axis of the inner cavity twice as long as the thickness of the +spongy wall. Proportion of both axes = 5 : 3. + +_Dimensions._--Length of the shell 0.2, breadth 0.12. + +_Habitat._--South Atlantic, Station 325, surface. + + +5. _Spongellipsis spinosa_, n. sp. + +Shell nearly cylindrical, covered with numerous thorns and thirty to forty +larger conical radial spines, somewhat longer than the major axis. Spongy +framework compact, with small meshes, four {343}to eight times as broad as +the bars. Minor axis of the inner cavity about six times as large as the +thickness of the spongy wall. Proportion of both axes = 4 : 1. + +_Dimensions._--Length of the shell 0.24, breadth 0.06. + +_Habitat._--South Pacific, Station 300, surface. + + + +Genus 145. _Spongurus_,[184] Haeckel, 1862, Monogr. d. Radiol., p. 465. + +_Definition._--#Spongurida# with ellipsoidal or cylindrical (sometimes +three-jointed) shell, of solid spongy framework, without internal cavity +and without latticed medullary shell. Polar spines and outer lattice-mantle +absent. + +The genus _Spongurus_ was founded by me in 1862 for the common cosmopolitan +_Spongurus cylindricus_, a massive spongy cylinder with radial spines. I +enlarge here the conception of the genus, in receiving also ellipsoidal, +massive spongy #Prunoidea#, with or without radial spines. Sometimes the +cylindrical shell is more or less distinctly three-jointed, with two +annular strictures, as also in the following and nearly allied genus. + + + +Subgenus 1. _Spongurantha_, Haeckel. + +_Definition._--Spongy framework everywhere of the same structure; surface +smooth or rough, but without radial spines. + + +1. _Spongurus stuparius_, n. sp. + +Shell ellipsoidal, one and a half times as long as broad, with nearly +smooth surface. Spongy framework everywhere of equal structure, with small +meshes, four to six times as broad as the bars. + +_Dimensions._--Length of the shell (or major axis) 0.2, breadth of it (or +minor axis) 0.14. + +_Habitat._--South Pacific, Station 295, depth 1500 fathoms. + + +2. _Spongurus stypticus_, n. sp. + +Shell ellipsoidal, twice as long as broad, with thorny surface. Spongy +framework everywhere of equal structure, with large meshes, ten to twenty +times as broad as the bars. + +_Dimensions._--Length of the shell 0.3, breadth 0.15. + +_Habitat._--Pacific, central area, Station 274, depth 2750 fathoms. + + +3. _Spongurus phalanga_, Haeckel. + + _Spongurus cylindricus_, Stoehr, 1880, Palaeontogr., vol. xxvi. p. 119, + Taf. vii. fig. 3. + +Shell nearly cylindrical, five times as long as broad, with thorny surface. +Spongy framework compact, everywhere of equal structure, with small meshes, +scarcely broader than the bars. + +{344}_Dimensions._--Length of the shell 0.24, breadth 0.05. + +_Habitat._--Pacific, central area, Station 268, depth 2600 fathoms; fossil +in the Tertiary rocks of Sicily, Stoehr. + + + +Subgenus 2. _Spongurella_, Haeckel. + +_Definition._--Spongy framework everywhere of the same structure; surface +armed with radial spines. + + +4. _Spongurus asper_, Haeckel. + + + _Haliomma asperum_, Joh. Mueller, 1858, Abhandl. d. k. Akad. d. Wiss. + Berlin, p. 40, Taf. ii. fig. 2. + + _Haliomma asperum_, Haeckel, 1862, Monogr. d. Radiol., p. 431. + +Shell ellipsoidal, one and a third times as long as broad, with thorny +surface and twenty symmetrically disposed, thin, bristle-shaped, radial +spines, about as long as the shell. Spongy framework everywhere of the same +structure, very compact, with small meshes, three to four times as broad as +the bars. + +_Dimensions._--Length of the shell 0.11, breadth 0.08. + +_Habitat._--Mediterranean, Ligurian coast (J. Mueller), Portofino +(Haeckel). + + +5. _Spongurus cylindricus_, Haeckel. + + _Spongurus cylindricus_, Haeckel, 1862, Monogr. d. Radiol., p. 465, Taf. + xxvii. fig. 1. + +Shell cylindrical, four to five times as long as broad, with nearly smooth +surface, and twenty to thirty thin, bristle-shaped, radial spines, about +half as long as the shell. Spongy framework everywhere of the same +structure, very compact, with small meshes, scarcely broader than the bars. + +_Dimensions._--Length of the shell 0.2, breadth 0.04 to 0.05. + +_Habitat._--Cosmopolitan; Mediterranean, Atlantic, and Pacific, surface. + + +6. _Spongurus tricolus_, n. sp. + +Shell nearly cylindrical, with two slight annular transverse strictures; +its middle part is somewhat broader. Surface thorny, with numerous (forty +to sixty or more) short, thin, radial spines, not longer than the breadth +of the shell. Spongy framework everywhere of the same structure, compact, +with small meshes, twice to three times as broad as the bars. + +_Dimensions._--Length of the shell 0.24, breadth 0.04 to 0.06. + +_Habitat._--Pacific, central area, Station 272, 2600 fathoms. + + + +Subgenus 3. _Sponguroma_, Haeckel. + +_Definition._--Spongy framework in the inner part of the shell very +compact, in the outer part very loose; surface armed with radial spines. + + +{345}7. _Spongurus radians_, n. sp. + +Shell ellipsoidal, one and a half times as long as broad, with thorny +surface, and eighty to one hundred and twenty (or more) thin, +bristle-shaped, radial spines, somewhat longer than the shell. Spongy +framework in the inner part very compact, in the outer part very loose, +with a gradual transition between the two parts. Meshes in the central part +not broader than the bars, in the superficial part ten to twenty times as +broad. + +_Dimensions._--Length of the shell 0.24, breadth 0.16. + +_Habitat._--Mediterranean, Portofino, near Genoa, Haeckel, surface. + + +8. _Spongurus spongechinus_, n. sp. + +Shell ellipsoidal, one and a third times as long as broad, with thorny +surface, and thirty to forty thick, conical radial spines, about half as +long as the shell. Spongy framework in the inner part of the shell compact, +in the outer loose, with a gradual transition between the two parts. Meshes +in the central part smaller than the bars, in the superficial part four to +eight times as broad. + +_Dimensions._--Length of the shell 0.18, breadth 0.14. + +_Habitat._--North Atlantic, Station 353, surface. + + + +Genus 146. _Spongocore_,[185] n. gen. + +_Definition._--#Spongurida# with ellipsoidal or cylindrical (sometimes +three-jointed) shell of solid spongy framework, without internal cavity and +without latticed medullary shell. Polar spines absent. An outer +lattice-mantle is connected with the spongy shell by radial beams. + +The genus _Spongocore_ contains some widely distributed Spongurida, which +are distinguished from the nearly related _Spongurus_ by the development of +a peculiar veil or mantle of delicate lattice-work, which envelops either +the whole shell or only the middle part of it, and is connected with it by +numerous radial beams. The distance of the simple fine lattice-lamella from +the spongy shell is everywhere the same. Often the cylindrical shell is +three-jointed, with two annular strictures, as also in the foregoing +_Spongurus._ It is derived from the latter by development of the veil +connecting the points of the radial spines. + + + +Subgenus 1. _Spongocorina_, Haeckel. + +_Definition._--Shell without distinct annular strictures, not evidently +three-jointed. + + +{346}1. _Spongocore velata_, n. sp. + +Shell ellipsoidal, one and a half times as long as broad, without annular +strictures. Spongy framework loose, with rather large meshes, four to six +times as broad as the bars. The whole spongy shell enveloped by a delicate +veil with smooth surface, connected with it by numerous thin radial beams. +Breadth of the spongy ellipsoid (or minor axis) six times as large as its +distance from the veil. + +_Dimensions._--Length of the whole shell (with veil) 0.3, breadth 0.2; +distance of the veil from the spongy ellipsoid 0.035. + +_Habitat._--South Atlantic, Station 325, surface. + + +2. _Spongocore diplocylindrica_, n. sp. + +Shell cylindrical, three times as long as broad, without annular +strictures. Spongy framework compact, with small meshes, twice to three +times as broad as the bars. The whole surface of the spongy cylinder, with +exception of both rounded polar faces, enveloped by a delicate cylindrical +veil with smooth surface, connected with it by numerous radial beams. +Diameter of the spongy cylinder twice as large as its distance from the +veil. + +_Dimensions._--Length of the shell 0.3, breadth (with veil) 0.1; distance +of the veil 0.025. + +_Habitat._--South Pacific, Station 302, surface. + + + +Subgenus 2. _Spongocorisca_, Haeckel. + +_Definition._--Shell distinctly three-jointed, with two transverse annular +strictures. + + +3. _Spongocore chrysalis_, n. sp. + +Spongy shell cylindrical, without the veil six times as long as broad, +three-jointed, with two annular strictures; all three joints of the same +length. The whole spongy shell enveloped by a thin veil with thorny +surface, connected with it by numerous radial beams. Breadth of the spongy +cylinder three times as large as its distance from the veil. + +_Dimensions._--Length of the shell (with veil) 0.4, breadth 0.1; distance +of the veil from the spongy shell 0.02. + +_Habitat._--South Atlantic (off Patagonia), Station 318, surface. + + +4. _Spongocore cincta_, n. sp. + +Spongy shell cylindrical, without the veil four times as long as broad, +three-jointed, with two annular strictures; all three joints of the same +length. Only the middle joint enveloped by a thin veil with smooth surface, +connected with it by radial beams. Both terminal joints with long, +{347}bristle-shaped, radial spines. Breadth of the spongy cylinder twice as +large as its distance from the veil. + +_Dimensions._--Length of the shell 0.24, breadth (with veil) 0.12; distance +of the veil 0.03. + +_Habitat._--Indian Ocean, Madagascar, Rabbe, surface. + + +5. _Spongocore pupula_, n. sp. + +Spongy shell cylindrical, without the veil six times as long as broad, +three-jointed, with two annular strictures; the middle joint half as long +as either terminal joint. Only the middle joint enveloped by a thin veil +with spiny surface, connected with it by twenty to thirty radial beams, +which are prolonged on the outside into short radial spines. Breadth of the +spongy cylinder about equal to its distance from the veil. + +_Dimensions._--Length of the shell 0.2, breadth (with veil) 0.1; distance +of the veil 0.033. + +_Habitat._--North Pacific, Station 244, surface. + + +6. _Spongocore puella_, n. sp. (Pl. 48, fig. 6). + +Spongy shell cylindrical, without the veil five times as long as broad, +three-jointed, with two annular strictures; the middle joint twice as long +as either terminal joint. Only the middle joint enveloped by a thin veil +with delicate lattice-work and smooth surface; both terminal joints armed +with numerous thin, bristle-shaped, radial spines. Breadth of the spongy +cylinder twice as large as the distance from the veil. + +_Dimensions._--Length of the shell 0.25 to 0.3, breadth (with veil) 0.1 to +0.12; distance of the veil 0.028 to 0.032. + +_Habitat._--South Pacific, Stations 295 to 304, surface. + + + +Genus 147. _Spongoprunum_,[186] n. gen. + +_Definition._--#Spongurida# with ellipsoidal or cylindrical shell of solid +spongy framework, without internal cavity and without latticed medullary +shell. On the poles of the axis occur two opposite strong spines. + +The genus _Spongoprunum_ differs from the most nearly allied _Spongurus_ by +the possession of two strong solid spines, lying in the axis of the +ellipsoidal or cylindrical massive spongy shell, on its two opposite poles. +_Spongoprunum_ bears therefore the same relation to _Spongurus_ that +_Ellipsoxiphus_ does to _Cenellipsis_. + + +1. _Spongoprunum amphilonche_, n. sp. (Pl. 48, fig. 7). + +Shell ellipsoidal, two and a third times as long as broad, with nearly +smooth surface. Spongy framework very compact, in the whole solid shell of +the same structure, with very small meshes, {348}scarcely broader than the +bars. Two polar spines conical, very strong, about half as long as the main +axis of the shell and three times as long as broad. + +_Dimensions._--Length of the shell (without spines) 0.2, breadth 0.08. + +_Habitat._--Central Pacific, Station 265, depth 2900 fathoms; fossil in the +rocks of Barbados. + + +2. _Spongoprunum atractus_, n. sp. + +Shell spindle-shaped, twice as long as broad, with thorny surface. Spongy +framework loose, in the whole shell of the same structure, with large +meshes, eight to twelve times as broad as the bars. Two polar spines +angular, pyramidal, very strong, about one-third as long as the shell, and +twice as long as broad. + +_Dimensions._--Length of the shell 0.2, breadth 0.11. + +_Habitat._--Western Tropical Pacific, Station 225, depth 4475 fathoms. + + +3. _Spongoprunum amphicylindrus_, n. sp. + +Shell nearly cylindrical, four times as long as broad, with rough surface. +Spongy framework compact, in the whole shell of equal structure, with small +meshes, twice to three times as broad as the bars. Two polar spines +cylindrical, very large, longer than the shell, and about one-fourth as +thick as its diameter. + +_Dimensions._--Length of the shell 0.2, breadth 0.05. + +_Habitat._--South Atlantic, Station 333, surface. + + + +Subfamily SPONGODRUPPIDA, Haeckel. + +_Definition._--#Spongurida# with latticed medullary shell, enclosed by a +spongy cortical shell. + + + +Genus 148. _Spongodruppa_,[187] n. gen. + +_Definition._--#Spongurida# with spongy ellipsoidal cortical shell, +enclosing a simple, spherical or ellipsoidal, latticed medullary shell. +Polar spines absent. + +The genus _Spongodruppa_ opens the series of Spongodruppida, or of those +Spongurida in which the ellipsoidal spongy cortical shell encloses a simple +or double, latticed, medullary shell. In _Spongodruppa_, the simplest and +probably the ancestral form of this subfamily, the medullary shell is +simple and the polar spines absent. It may be derived from _Druppula_ by a +spongy thickening of the simple latticed cortical shell. + + + +{349}Subgenus 1. _Spongodruppula_, Haeckel. + +_Definition._--Surface of the shell smooth or rough, without radial spines. + + +1. _Spongodruppa terebintha_, n. sp. + +Cortical shell one and a third times as long as broad, with smooth surface, +three times as broad as the spherical medullary shell. Spongy framework +very compact, with small meshes of the same breadth as the bars. Thickness +of the spongy wall equal to the radius of the medullary shell. + +_Dimensions._--Length of the cortical shell (or major axis of the +ellipsoid) 0.16, breadth (or minor axis) 0.12; thickness of its wall 0.02; +medullary shell 0.04. + +_Habitat._--Western Tropical Pacific, Station 225, depth 4475 fathoms. + + +2. _Spongodruppa pistacia_, n. sp. + +Cortical shell one and a half times as long as broad, with thorny surface, +nearly five times as broad as the spherical medullary shell. Spongy +framework compact, its thickness equal to the diameter of the medullary +shell. + +_Dimensions._--Length of the cortical shell 0.2, breadth 0.14; thickness of +its wall 0.03; medullary shell 0.03. + +_Habitat._--Fossil in the rocks of Barbados. + + +3. _Spongodruppa lentisca_, n. sp. + +Cortical shell twice as long as broad, with rough surface, four times as +large as the ellipsoidal medullary shell. Spongy framework loose, with +large meshes, its thickness equal to the length of the medullary shell. + +_Dimensions._--Length of the cortical shell 0.25, breadth 0.13; thickness +of its wall 0.06; length of the medullary shell 0.06, breadth 0.04. + +_Habitat._--Pacific, central area, Station 266, surface. + + + +Subgenus 2. _Spongodruppium_, Haeckel. + +_Definition._--Surface of the shell armed with radial spines. + + +4. _Spongodruppa frangula_, n. sp. + +Cortical shell one and a third times as long as broad, three times as broad +as the spherical medullary shell. Spongy framework loose, with large +meshes, its thickness half as large as the diameter of the medullary shell. +Surface covered with numerous (forty to fifty) thin, bristle-shaped, radial +spines, about as long as the cortical shell. + +{350}_Dimensions._--Length of the cortical shell 0.24, breadth 0.18; +thickness of its wall 0.035; diameter of the medullary shell 0.06. + +_Habitat._--North Pacific, Station 244, depth 2900 fathoms. + + +5. _Spongodruppa elliptica_, Haeckel. + + _Acanthosphaera elliptica_, Ehrenberg, 1872, Abhandl. d. k. Akad. d. + Wiss. Berlin, p. 285, Taf. vii. fig. 4. + +Cortical shell nearly twice as long as broad, four times as broad as the +ellipsoidal medullary shell. Spongy framework compact, with small meshes. +Surface covered with very numerous short radial spines, about as long as +the medullary shell. + +_Dimensions._--Length of the cortical shell 0.2, breadth 0.11; length of +the medullary shell 0.04, breadth 0.03. + +_Habitat._--Philippine Sea, Ehrenberg, Station 206, depth 2100 fathoms. + + +6. _Spongodruppa polyacantha_, Haeckel. + + _Haliomma polyacanthum_, J. Mueller, 1858, Abhandl., p. 36, Taf. i. figs. + 10, 11. + + _Haliomma polyacanthum_, Haeckel, 1862, Monogr. d. Radiol., p. 430. + +Cortical shell one and a third times as long as broad, twice as broad as +the ellipsoidal medullary shell. Spongy framework loose on the surface, +with large regular meshes. Surface covered with fifteen to twenty thick, +conical spines, about as long as the radius of the shell. + +_Dimensions._--Length of the cortical shell 0.12, of the medullary shell +0.09; diameter of the medullary shell 0.05 to 0.06. + +_Habitat._--Mediterranean (south coast of France); Atlantic (Canary +Islands), Station 354, surface. + + + +Genus 149. _Spongatractus_,[188] n. gen. + +_Definition._--#Spongurida# with spongy ellipsoidal cortical shell, +enclosing a simple, spherical or ellipsoidal, latticed medullary shell. On +the poles of the axis occur two opposite strong spines. + +The genus _Spongatractus_ differs from _Spongodruppa_ by development of two +strong spines in the axis of the shell, on its two opposite poles; +therefore it bears the same relation to the latter that _Lithatractus_ does +to _Druppula_, and can be derived from _Lithatractus_ by a spongy +thickening of the cortical shell. + + +1. _Spongatractus pachystylus_, Haeckel. + + _Spongosphaera pachystyla_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. + Wiss. Berlin, p. 82, Taf. xxvi. fig. 3. + +Cortical shell one and a half times as long as broad, with rough surface. +Spongy framework compact, with small meshes, about as thick as the +spherical medullary shell. Polar spines very {351}stout, conical, slightly +sulcated, about as long as the breadth of the cortical shell, as broad at +the base as the medullary shell. + +_Dimensions._--Length of the cortical shell 0.2, breadth 0.13; thickness of +the spongy wall 0.045; diameter of the medullary shell 0.04. + +_Habitat._--Fossil in the rocks of Barbados, Ehrenberg; living in the +Equatorial Atlantic, Station 348, depth (2450) fathoms. + + +2. _Spongatractus fusiformis_, n. sp. + +Cortical shell one and a third times as long as broad, with nearly smooth +surface. Spongy framework very compact, with very small meshes, about as +thick as the radius of the spherical medullary shell. Polar spines very +strong, three-sided pyramidal, about as long as the breadth of the cortical +shell, as broad at the base as the medullary shell. + +_Dimensions._--Length of the cortical shell 0.16 to 0.18, breadth 0.12 to +0.14; thickness of the spongy wall 0.02; diameter of the medullary shell +0.04. + +_Habitat._--Pacific, central area, Station 268, depth 2900 fathoms. + + +3. _Spongatractus streptacanthus_, n. sp. + +Cortical shell twice as long as broad, with thorny surface. Spongy +framework loose, with large meshes, about as thick as the ellipsoidal +medullary shell. Polar spines very long, three-sided prismatic, with three +spirally contorted edges, much longer than the cortical shell, half as +broad as the medullary shell. + +_Dimensions._--Length of the cortical shell 0.25, breadth 0.13; thickness +of the spongy wall 0.03; diameter of the medullary shell 0.03 to 0.04. + +_Habitat._--North Atlantic, off Canary Islands, Haeckel. + + + +Genus 150. _Spongoliva_,[189] n. gen. + +_Definition._--#Spongurida# with spongy ellipsoidal cortical shell, +enclosing a double, spherical or ellipsoidal, latticed medullary shell. +Polar spines absent. + +The genus _Spongoliva_ differs from the nearest _Spongodruppa_ by +duplication of the medullary shell; it bears therefore the same relation to +this that _Prunulum_ does to _Druppula_, and can be regarded as a +_Prunulum_, in which the simple latticed cortical shell is replaced by a +spongy framework. + + + +Subgenus 1. _Spongolivetta_, Haeckel. + +_Definition._--Surface of the shell smooth or rough, without radial spines. + + +{352}1. _Spongoliva cerasina_, n. sp. + +Cortical shell one and a fourth times as long as broad, with smooth +surface, four times as broad as the outer spherical medullary shell. Spongy +framework very compact, with very small meshes, its thickness equal to the +diameter of the outer medullary shell. + +_Dimensions._--Length of the cortical shell 0.2, breadth 0.16; thickness of +its wall 0.04; diameter of the outer medullary shell 0.04, of the inner +0.014. + +_Habitat._--Fossil in the rocks of Barbados. + + +2. _Spongoliva prunulina_, n. sp. + +Cortical shell one and a third times as long as broad, with smooth surface, +three times as large as the outer ellipsoidal medullary shell. Spongy +framework very compact, with small meshes, its thickness equal to the +diameter of the inner medullary shell. + +_Dimensions._--Length of the cortical shell 0.24, breadth 0.18; thickness +of its wall 0.03; size of the outer medullary shell 0.08 to 0.06, of the +inner 0.03. + +_Habitat._--Pacific, central area, Station 265, depth 2900 fathoms. + + +3. _Spongoliva persicina_, n. sp. + +Cortical shell one and a half times as long as broad, with rough surface, +five to six times as large as the ellipsoidal outer medullary shell. Spongy +framework loose, with large meshes, its thickness about equal to the outer +medullary shell. + +_Dimensions._--Length of the cortical shell 0.26, breadth 0.18; thickness +of its wall 0.04; size of the outer medullary shell 0.045 to 0.035, of the +inner 0.015. + +_Habitat._--Equatorial Atlantic, Station 348, depth (2450) fathoms. + + +4. _Spongoliva amygdalina_, n. sp. + +Cortical shell twice as long as broad, with thorny surface, ten times as +long as the small spherical outer medullary shell. Spongy framework loose, +with large meshes, its thickness one and a half times as large as the outer +medullary shell. + +_Dimensions._--Length of the cortical shell 0.3, breadth 0.16; thickness of +its wall 0.045; size of the outer medullary shell 0.03, of the inner 0.015. + +_Habitat._--Fossil in the Tertiary rocks of Sicily (Caltanisetta). + + + +Subgenus 2. _Spongolivina_, Haeckel. + +_Definition._--Surface of the shell armed with radial spines. + + +5. _Spongoliva opuntina_, n. sp. + +Cortical shell one and a third times as long as broad, armed with numerous +thin, bristle-shaped, radial spines, nearly as long as the shell. Spongy +framework loose, with large meshes, its thickness nearly equal to the +diameter of the outer spherical medullary shell. + +{353}_Dimensions._--Length of the cortical shell 0.18, breadth 0.14; +thickness of its wall 0.035; diameter of the outer medullary shell 0.04, of +the inner 0.02. + +_Habitat._--South Atlantic, Station 325, surface. + + +6. _Spongoliva daturina_, n. sp. + +Cortical shell one and a half times as long as broad, armed with numerous, +thick and short, conical radial spines, about as long as the outer +medullary shell. Spongy framework compact, with small meshes, its thickness +equal to half the length of the outer ellipsoidal medullary shell. + +_Dimensions._--Length of the cortical shell 0.24, breadth 0.16; thickness +of its wall 0.025; diameter of the outer medullary shell 0.045 to 0.035, of +the inner 0.025. + +_Habitat._--Pacific, central area, Station 272, surface. + + + +Genus 151. _Spongoxiphus_,[190] n. gen. + +_Definition._--#Spongurida# with spongy ellipsoidal cortical shell, +enclosing a double, spherical or ellipsoidal, latticed medullary shell. On +the poles of the axis occur two opposite strong spines. + +The genus _Spongoxiphus_ differs from _Spongoliva_ by the development of +two strong spines in the axis of the shell, on its two opposite poles. From +the similar _Spongatractus_ it differs in the duplication of the medullary +shell. It may also be regarded as a _Stylatractus_, in which the simple +latticed cortical shell is replaced by an irregular spongy framework. + + +1. _Spongoxiphus sphaerococcus_, n. sp. + +Cortical shell one and a half times as long as broad, with thorny surface. +Spongy framework compact, with small meshes, its thickness equal to the +radius of the outer medullary shell. Both medullary shells spherical, the +outer three times as broad as the inner. Polar spines very stout, conical, +slightly sulcated, about half as long as the cortical shell, as broad at +the base as the outer medullary shell. (Differs from _Spongatractus +pachystylus_ almost only in the double medullary shell.) + +_Dimensions._--Length of the cortical shell 0.18, breadth 0.12; thickness +of the spongy wall 0.025; diameter of the outer medullary shell 0.05, of +the inner 0.016. + +_Habitat._--Fossil in the rocks of Barbados (Haeckel); also living in the +Pacific, central area, Station 265, depth 2900 fathoms. + + +{354}2. _Spongoxiphus prunococcus_, n. sp. (Pl. 17, figs. 12, 13). + + _Spongostylus prunococcus_, Haeckel, 1881, Prodromus, p. 455, et Atlas, + pl. xvii. figs. 12, 13. + +Cortical shell one and a third times as long as broad, with smooth surface. +Spongy framework very compact, with very small meshes, its thickness about +equals the breadth of the outer medullary shell. Both medullary shells +ellipsoidal, the outer three times as large as the inner. Polar spines very +stout, three-sided pyramidal, about half as long as the cortical shell, on +the base about as broad as the outer medullary shell. (Differs from the +preceding in the ellipsoidal form of both medullary shells, and in the +finer structure of the spongy framework.) + +_Dimensions._--Length of the cortical shell 0.18 to 0.2, breadth 0.14 to +0.16; thickness of the spongy wall 0.035 to 0.04; length of the outer +medullary shell 0.04 to 0.06, breadth 0.03 to 0.04. + +_Habitat._--Pacific, central area, Stations 265 to 268, depths 2700 to 2900 +fathoms. + + + +Family XIV. #ARTISCIDA#, Haeckel (Pl. 39, figs. 9, 10; Pl. 48, fig. 5). + +_Artiscida_, Haeckel, 1881, Prodromus, p. 462. + +_Definition._--#Prunoidea# with an ellipsoidal twin-shell divided by an +equatorial stricture into two communicating hemiellipsoidal or +hemispherical chambers, without enclosed medullary shell. Central capsule +ellipsoidal, with or without equatorial stricture. + +The family #Artiscida# has a simple fenestrated outer shell, like that of +the Ellipsida, but differs from these in the presence of an equatorial +constriction, by which it assumes a characteristic twin form, somewhat +similar to a violin (Pl. 39, figs. 9, 10). From the Cyphinida, which have +the same form of the cortical shell, the Artiscida differ in the absence of +the medullary shell. It is possible that the Artiscida are descended from +the Cyphinida (by loss of the medullary shell), but it is more probable +that they arise from the Ellipsida by an annular constriction in the +equatorial plane (perhaps the formation of the shell originally took place +while the central capsule was undergoing division). Both halves of the twin +shell are always of the same size and form. Its outer surface is either +smooth or covered with radial spines (_Artiscus_, Pl. 39, fig. 9). +Sometimes on the opposite poles of the main axis are developed solid spines +(_Stylartus_, Pl. 48, fig. 5) or hollow fenestrated tubes (_Cannartus_, Pl. +39, fig. 10). + +_The Central Capsule_ is either simply ellipsoidal, or has also an +equatorial constriction, which divides it into two equal halves. It is +constantly smaller than the surrounding shell, and separated from its inner +surface by a thicker or thinner jelly-mantle, the calymma. + +_Synopsis of the Genera of Artiscida._ + + On the poles of the main axis neither solid spines + nor hollow tubes, 152. _Artiscus_. + + On the poles of the main axis two solid spines (or + bunches of spines), 153. _Stylartus_. + + On the poles of the main axis two hollow fenestrated + tubes, 154. _Cannartus_. + + + +{355}Genus 152. _Artiscus_,[191] Haeckel, 1881, Prodromus, p. 462. + +_Definition._--#Artiscida# without peculiar polar appendages (without +strong solid spines or hollow fenestrated tubes on the poles of the main +axis). + +The genus _Artiscus_ represents the most simple and primitive form of the +Artiscida, and may therefore be regarded as the ancestral form of this +subfamily. It resembles an ordinary double loaf, composed of two equal, +nearly ellipsoidal fenestrated shells separated by the stricture in the +equatorial plane. _Artiscus_ can be derived from _Cenellipsis_ simply by +this equatorial constriction. But it can also be derived from _Cyphanta_ by +loss of the medullary shell. + + + +Subgenus 1. _Artiscium_, Haeckel. + +_Definition._--Surface of the shell smooth or rough, without radial rods or +spines. + + +1. _Artiscus paniscus_, n. sp. + +Pores of the shell regular, hexagonal, four times as broad as the bars; ten +to twelve pores on the half meridian, eight to nine on the half equator. +Surface smooth. (The network of this species is quite the same as that of +the proximal camerae of _Panartus diploconus_, Pl. 40, fig. 1.) + +_Dimensions._--Main axis of the shell 0.12, equatorial axis 0.07; meshes +0.013, bars 0.003. + +_Habitat._--Pacific, central area, Station 271, depth 2425. + + +2. _Artiscus facetus_, n. sp. + +Pores of the shell regular, circular, with prominent hexagonal frame, twice +as broad as the bars; twenty-two to twenty-four pores on the half meridian, +fourteen to fifteen on the half equator. Surface a little thorny. (The +shell of this species exhibits nearly the same formation as that of +_Cyphonium virgineum_, Pl. 39, fig. 12, but without enclosed medullary +shells.) + +_Dimensions._--Main axis of the shell 0.15, equatorial axis 0.09; meshes +0.01, bars 0.005. + +_Habitat._--Pacific, central area, Station 266, depth 2750 fathoms. + + +3. _Artiscus paniculus_, n. sp. + +Pores of the shell regular, circular, without hexagonal frame, as broad as +the bars; fourteen to sixteen pores on the half meridian, ten to eleven on +the half equator. Surface quite smooth. + +_Dimensions._--Main axis of the shell 0.13, equatorial axis 0.06; meshes +0.01, bars 0.01. + +_Habitat._--Fossil in the Tertiary rocks of Barbados (Haeckel). + + +{356}4. _Artiscus panarius_, n. sp. + +Pores of the shell irregular, roundish, twice to four times as broad as the +bars; sixteen to eighteen pores on the half meridian, twelve to thirteen on +the half equator. Surface smooth. + +_Dimensions._--Main axis of the shell 0.11, equatorial axis 0.06; meshes +0.005 to 0.02, bars 0.001 to 0.004. + +_Habitat._--Western Tropical Pacific, Station 224, depth 1850 fathoms. + + + +Subgenus 2. _Artidium_, Haeckel, 1881, Prodromus, p. 462. + +_Definition._--Surface of the shell covered with radial rods or spines. + + +5. _Artiscus elegans_, n. sp. + +Pores of the shell regular, circular, with hexagonal frames, twice as broad +as the bars; fourteen pores on the half meridian, eight to nine on the half +equator. From every corner of the hexagonal frames (between every three +pores) starts a thin, three-sided pyramidal spine, twice as large as a +pore. + +_Dimensions._--Main axis 0.13, equatorial axis 0.08; meshes 0.007, bars +0.004; spines 0.015 long. + +_Habitat._--South Atlantic, Station 332, depth 2200 fathoms. + + +6. _Artiscus nodosus_, n. sp. (Pl. 39, fig. 9). + +Pores of the shell subregular, circular, without hexagonal frame, three +times as broad as the bars; sixteen to eighteen on the half meridian, ten +to twelve on the half equator. Irregularly scattered on the whole surface a +variable number (twenty-five to thirty in all) of stout short radial spines +or rather blunt rods; the length and thickness of these is the same, and +equals the size of two to three meshes; its form resembles a truncated +six-sided pyramid. + +_Dimensions._--Main axis 0.11, equatorial axis 0.08; meshes 0.01, bars +0.003; length and thickness of the radial sticks 0.02. + +_Habitat._--Pacific, central area, Station 272, depth 2600 fathoms. + + +7. _Artiscus hystrix_, n. sp. + +Pores of the shell irregular, roundish, of very unequal size and dissimilar +form, twice to eight times as broad as the bars; ten to fifteen on the half +meridian, seven to nine on the half equator. Irregularly scattered on the +whole surface a large number of thin conical spines, about as large as the +meshes, partly directed radially, partly obliquely. (The shell of this +species resembles very much that of _Cyphonium ceratospyris_ (p. 366) = +_Didymocyrtis ceratospyris_, Monogr. d. Radiol., 1862, Taf. xxii. fig. 14, +but is without the enclosed inner shells.) + +{357}_Dimensions._--Main axis 0.12, equatorial axis 0.07; meshes 0.004 to +0.02, bars 0.002 to 0.005; spines 0.01 to 0.02. + +_Habitat._--Atlantic, Eastern Tropical part, Station 346, surface. + + + +Genus 153. _Stylartus_,[192] Haeckel, 1881, Prodromus, p. 462. + +_Definition._--#Artiscida# with two strong, solid, polar spines, or two +bunches of polar spines, opposite on the two poles of the main axis. + +The genus _Stylartus_ differs from _Artiscus_ by the production of two +large opposite spines in the main axis, starting from both poles of it; +sometimes every spine is surrounded by a group of smaller radial spines. +The genus is nearly allied to _Ellipsoxiphus_ (p. 295), and differs from it +only in the equatorial stricture of the ellipsoidal shell. But it may also +be derived from the similar _Cyphinus_ (Pl. 39, fig. 14) by loss of the +medullary shell. + + + +Subgenus 1. _Stylartella_, Haeckel. + +_Definition._--On each pole of the main axis only one single large spine. + + +1. _Stylartus bipolaris_, n. sp. (Pl. 48, fig. 5). + +Shell thick walled, rough; both its chambers nearly spherical, with +irregular, roundish pores, twice to four times as broad as the bars; eight +to ten on the half equator of each chamber. Polar spines very strong, +conical, as long as the greatest breadth. + +_Dimensions._--Length of the shell (without spines) 0.18, greatest breadth +0.13; length of the polar spines 0.13, basal breadth 0.03. + +_Habitat._--Western Tropical Pacific, Station 224, depth 1850 fathoms. + + +2. _Stylartus bicuspis_, n. sp. + +Shell thin walled, smooth, with regular, circular pores, twice as broad as +the bars; twelve to fourteen on the half equator of each chamber. Polar +spines very stout, straight, three-sided pyramidal, half as long as the +shell. + +_Dimensions._--Length of the shell 0.16, greatest breadth 0.12; length of +the polar spines 0.08, basal thickness 0.025. + +_Habitat._--Pacific, central area. Station 266, depth 2750 fathoms. + + + +Subgenus 2. _Stylartura_, Haeckel. + +_Definition._--On each pole of the main axis a bunch of several spines. + + +{358}3. _Stylartus palatus_, n. sp. + +Shell thick walled, thorny, with irregular, roundish pores, twice to three +times as broad as the bars; fifteen to eighteen on the half equator of each +chamber. On each pole of the main axis a large conical spine, surrounded by +a group of ten to fifteen smaller spines, one-third to two-thirds as long +as the breadth of the deep equatorial stricture. + +_Dimensions._--Length of the shell 0.14, greatest breadth 0.09; length of +the polar spines 0.03 to 0.06, basal breadth 0.005 to 0.015. + +_Habitat._--Indian Ocean, Madagascar, Rabbe, surface. + + +4. _Stylartus penicillus_, n. sp. + +Shell thin walled, smooth, with irregular, roundish pores, three to four +times as broad as the bars; ten to twelve on the half equator of each +chamber. On each pole of the main axis a brush-like bunch of twenty to +thirty thin conical radial spines, half as long as the shell. + +_Dimensions._--Length of the shell 0.15, greatest breadth 0.1; length of +the polar spines 0.08, basal breadth 0.005. + +_Habitat._--Equatorial Atlantic, Station 347, surface. + + + +Genus 154. _Cannartus_,[193] Haeckel, 1881, Prodromus, p. 462. + +_Definition._--#Artiscida# with two hollow polar tubes (fenestrated +cylindrical or conical tubuli, opposite on the two poles of the main axis). + +The genus _Cannartus_ differs from _Artiscus_ by the production of two +opposite hollow tubes on both poles of the main axis. The cavity of the +conical or cylindrical fenestrated tubes communicates freely with that of +the shell; the network in both is the same. The distal end of the tubes is +nearly always broken off, sometimes closed, with a conical apex. +_Cannartus_ can be derived either from _Pipettella_ by a transverse +equatorial constriction, or from _Cannartiscus_ by the loss of the +medullary shell, or from _Artiscus_ by the production of the polar tubes. + + +1. _Cannartus violina_, n. sp. (Pl. 39, fig. 10). + +Pores of the shell subregular, circular, twice to three times as broad as +the bars; eighteen to twenty on the half meridian, fourteen to sixteen on +the half equator. Shell-wall in the "tropical zone" of both halves +thickened. Polar tubes nearly cylindrical, about as long as the main axis, +distal ends broken off. + +_Dimensions._--Main axis 0.14, equatorial axis 0.09; meshes 0.008, bars +0.003; length of the polar tubes 0.12, breadth 0.02 to 0.03. + +_Habitat._--Pacific, central area, Station 268, depth 2900 fathoms. + + +{359}2. _Cannartus bitubulus_, n. sp. + +Pores of the shell regular, circular, hexagonally framed, of the same +breadth as the bars; fourteen to sixteen on the half meridian, ten to +twelve on the half equator. Polar tubes cylindrical, longer than the main +axis, sulcated, distal ends broken off. (Similar to _Pipetta tuba_, Pl. 39, +fig. 7, but with equatorial stricture and without medullary shell.) + +_Dimensions._--Main axis 0.16, equatorial axis 0.12; meshes and bars 0.006; +length of the polar tubes 0.2, breadth 0.025. + +_Habitat._--South Atlantic, Station 332, depth 2200 fathoms. + + +3. _Cannartus biscottus_, n. sp. + +Pores of the shell irregular, roundish, twice to three times as broad as +the bars; ten to twelve on the half meridian, six to eight on the half +equator. Polar tubes conical, shorter than the main axis, with closed +apex. (Similar to _Cannartidium bicinctum_, Pl. 39, fig. 18, but without +enclosed medullary shell.) + +_Dimensions._--Main axis 0.11, equatorial axis 0.07; meshes 0.005 to 0.01, +bars 0.003; length of the polar tubes 0.08, breadth on the base 0.03. + +_Habitat._--Equatorial Atlantic, Station 348, depth 2450 fathoms. + + + +Family XV. #CYPHINIDA#, Haeckel (Pl. 39, figs. 11-19). + +_Cyphinida_, Haeckel, 1881, Prodromus, p. 462. + +_Definition._--#Prunoidea# with ellipsoidal twin-shell, divided by an +equatorial stricture into two communicating hemiellipsoidal or +hemispherical chambers; this external twin-shell (cortical shell) is either +simple or double, and encloses one or more internal concentric shells +(medullary shells). Central capsule ellipsoidal, commonly with an +equatorial constriction. + +The family #Cyphinida# have the same characteristic twin-form of the +cortical shell as the Artiscida, but differ from them in the presence of a +simple or double internal medullary shell, connected with the cortical +shell by radial beams. The fenestrated shell is therefore composed of two +or more concentric shells as in the Druppulida, but differs from these in +the ring-like equatorial constriction. + +_The Medullary Shell_, in the middle of the central capsule, is either +single or double, composed of two concentric shells. As in the Druppulida, +the form of the medullary shells is either spherical (Pl. 39, fig. 12_a_) +or lenticular, compressed from both poles of the main axis (Pl. 39, fig. +18_a_); sometimes the inner medullary shell is spherical, the outer +lenticular. + +_The Radial Beams_, which connect the medullary shell with the equatorial +constriction of the cortical shell, lie either all in the equatorial plane +(Pl. 39, fig. 11) or near it on both sides (Pl. 39, figs. 12_a_, 18_a_). + +{360}The _Cortical Shell_ is commonly simple (Pl. 39, figs. 12, 18), +sometimes composed of two concentric shells (Pl. 39, fig. 13), rarely of +three. As in the Artiscida, also in the Cyphinida, from both poles of the +main axis solid spines or hollow fenestrated tubes are often developed (Pl. +39, figs. 14, 16-18). + +_The Central Capsule_ of the Cyphinida (Pl. 39, fig. 13) is of the same +form as in the Artiscida, generally ellipsoidal, but with an equatorial +ring-like stricture, which divides it into two equal halves. It encloses +the simple or double medullary shell, and is perforated by the radial beams +starting from this. From the inner surface of the surrounding cortical +shell it is separated by a thicker or thinner jelly-layer, the calymma. +(Compare also Taf. xxii. fig. 14 of my Monograph, 1862.) + +_Synopsis of the Genera of Cyphinida._ + + ------------------------------------------------------------------------- + Cortical shell without peculiar spines or hollow fenestrated tubes on + both poles of the main axis. + ------------------------------------------------------------------------- + Cortical twin- {Medullary shell + shell simple { simple, 155. _Cyphanta_. + { + {Medullary shell + { double, 156. _Cyphonium_. + + Cortical twin- {Cortical shell + shell double { double, 157. _Cypassis_. + or triple; { + medullary {Cortical shell + shell double. { triple, 158. _Cyphocolpus_. + ------------------------------------------------------------------------- + Cortical shell simple, with peculiar spines or hollow fenestrated tubes + on both poles of the main axis. + ------------------------------------------------------------------------- + Two opposite {Medullary shell + polar spines { simple, 159. _Cyphinus_. + (or bunches { + of spines). {Medullary shell + { double, 160. _Cyphinidium_. + + Two opposite {Medullary shell + hollow { simple, 161. _Cannartiscus_. + fenestrated { + polar tubes. {Medullary shell + { double, 162. _Cannartidium_. + + + +Genus 155. _Cyphanta_,[194] n. gen. + +_Definition._--#Cyphinida# with simple cortical shell and simple medullary +shell, without polar spines or tubes. + +The genus _Cyphanta_ is the most simple of all Cyphinida, and can be +regarded as the common ancestral form of this family. It may be derived +phylogenetically from _Druppula_ by a ring-like constriction in the +equatorial plane of the ellipsoidal cortical shell, or from _Artiscus_ by +secondary formation of a central (spherical or ellipsoidal) medullary +shell. + + + +Subgenus 1. _Cyphantella_, Haeckel. + +_Definition._--Surface of the cortical shell smooth, without spines or +thorns. + + +{361}1. _Cyphanta colpodes_, n. sp. + +Cortical shell thin walled, with smooth surface; its pores regular, +hexagonal, three to four times as broad as the bars; ten to twelve on the +half meridian, seven to eight on the half equator. Medullary shell +spherical, its diameter one-third of the equatorial axis of the cortical +shell. (The cortical shell of this species is nearly identical with the +central half of the cortical shell of _Panartus diploconus_, Pl. 40, fig. +1.) + +_Dimensions._--Main axis of the cortical shell 0.12, equatorial axis 0.07; +meshes 0.013; bars 0.003; diameter of the medullary shell 0.025. + +_Habitat._--South Pacific, Station 285, depth 2375 fathoms. + + +2. _Cyphanta circopora_, n. sp. + +Cortical shell thick walled, with smooth surface; pores subregular, +circular, twice as broad as the bars; eighteen to twenty on the half +meridian, twelve to fourteen on the half equator. Medullary shell +spherical, its diameter one-half of the equatorial axis of the cortical +shell. (The shell of this species is very similar to that of _Cannartiscus +amphiconiscus_, Pl. 39, fig. 19, but without the polar tubes of that +species.) + +_Dimensions._--Main axis of the cortical shell 0.13, equatorial axis 0.08; +meshes 0.007, bars 0.003; diameter of the medullary shell 0.04. + +_Habitat._--Pacific, central area. Station 266, depth 2750 fathoms. + + +3. _Cyphanta laevis_, Haeckel. + + _Ommatospyris laevis_, Ehrenberg, 1872, Monatsber. d. k. preuss. Akad. d. + Wiss. Berlin, p. 318. + +Cortical shell thin walled, with smooth surface; pores of it irregular, +roundish, of very different size (some very large in the tropical circles +of both hemispheres). Pores twice to six times as broad as the bars; ten to +twelve on the half meridian, six to eight on the half equator. Medullary +shell spheroidal, compressed, its main axis somewhat shorter than its +equatorial axis, which attains half the length of that of the cortical +shell. (This species may be perhaps identical with _Ommatospyris laevis_ of +Ehrenberg, the diagnosis of which is insufficient and figure not given.) + +_Dimensions._--Main axis of the cortical shell 0.1, equatorial axis 0.06; +meshes 0.005 to 0.02, bars 0.002 to 0.04; diameter of the medullary shell +0.03. + +_Habitat._--Philippine Sea (Ehrenberg), Station 213, depths 2650 and 3300 +fathoms. + + +4. _Cyphanta arachnoides_, n. sp. + +Cortical shell very delicate and thin walled, cobweb-like, with smooth +surface; pores irregular, polygonal (mostly pentagonal or hexagonal), eight +to ten times as broad as the thread-like bars; ten to twelve on the half +meridian, six to eight on the half equator. Medullary shell spheroidal, +compressed, its main axis shorter than its equatorial axis, which is about +one-third that of the cortical shell. (This species is very similar to the +middle part of the shell of _Ommatocampe profundissima_, Ehrenberg, 1872, +Abhandl. d. k. Akad. d. Wiss. Berlin, Taf. viii. fig. 6.) + +{362}_Dimensions._--Main axis of the cortical shell 0.11, equatorial axis +0.06; meshes 0.01 to 0.02, bars 0.002; diameter of the medullary shell +0.02. + +_Habitat._--Atlantic, Canary Islands (Lanzerote), surface. + + + +Subgenus 2. _Cyphantissa_, Haeckel. + +_Definition._--Surface of the cortical shell spiny, everywhere scattered +with numerous thorns or spines. + + +5. _Cyphanta hispida_, n. sp. + +Cortical shell thick walled, with spiny surface; pores regular, circular, +with hexagonal frame, twice as broad as the bars; twelve to fourteen on the +half meridian, eight to ten on the half equator. From the corners of the +hexagonal frames (between every three pores) arise short, straight, conical +radial spines, somewhat longer than the breadth of the pores. Medullary +shell subspherical, its diameter about one-third of the equatorial axis of +the cortical shell. (The appearance of the cortical shell is the same as +that of the middle part of _Peripanartus amphiconus_, Pl. 40, fig. 5.) + +_Dimensions._--Main axis of the cortical shell 0.12, equatorial axis 0.07; +meshes 0.01, bars 0.005; length of the spines 0.012; diameter of the +medullary shell 0.02. + +_Habitat._--Pacific, central area, Station 274, depth 2750 fathoms. + + +6. _Cyphanta hystrix_, n. sp. + +Cortical shell thin walled, with thorny surface; pores irregular, roundish, +of very unequal size, twice to six times as broad as the bars; twelve to +eighteen on the half meridian, eight to thirteen on the half equator. +Between the pores irregularly scattered, bristle-like, thin spines about +the same size, partly straight, partly oblique, rising from the surface. +Medullary shell lenticular, compressed, its equatorial axis one and a half +times the length of the main axis, and about half that of the cortical +shell. + +_Dimensions._--Main axis of the cortical shell 0.15, equatorial axis 0.09; +meshes 0.004 to 0.02, bars 0.003 to 0.006; length of the spines 0.02; +diameter of the medullary shell 0.04. + +_Habitat._--South Atlantic, Station 318, surface. + + + +Genus 156. _Cyphonium_,[195] n. gen. + +_Definition._--#Cyphinida# with simple cortical shell and double medullary +shell, without polar spines or tubes. + +The genus _Cyphonium_ contains a number of very common species, among which +are the earliest known forms of this family, partly described by Ehrenberg +as Ommatospyris {363}(which genus contains also a number of other +#Prunoidea#), partly by me (1862) as _Didymocyrtis_. Both names are +inadequate, as allusions to quite different families of Nassellaria, but +may be retained as significations of subgeneric divisions. _Cyphonium_ +differs from _Cyphanta_ by the double medullary shell, which is either +spherical or lenticular. + + + +Subgenus 1. _Ommatospyris_, Ehrenberg (_partim_). + +_Definition._--Surface of the cortical shell smooth, without thorns or +spines. + + +1. _Cyphonium coscinoides_, n. sp. + + _Ommatospyris coscinoides_, Haeckel, 1881, Prodromus, p. 462. + +Cortical shell thin walled, with smooth surface; pores regular, hexagonal, +three to four times as broad as the bars; five to six on the half meridian, +eight to nine on the half equator of each chamber. Medullary shells both +spherical. (The cortical shell of this species is nearly the same as that +of _Cyphanta colpodes_, and as the middle part of the cortical shell of +_Panartus diploconus_, Pl. 40, fig. 1.) + +_Dimensions._--Main axis of the cortical shell 0.11, equatorial axis 0.06; +greatest breadth of the chambers 0.08; pores 0.013, bars 0.003. + +_Habitat._--North Pacific, Station 244, surface. + + +2. _Cyphonium virgineum_, n. sp. (Pl. 39, figs. 12, 12_a_). + + _Ommatospyris virginea_, Haeckel, 1881, Prodromus et Atlas (pl. xxxix. + fig. 12_a_). + +Cortical shell thick walled, with smooth surface (sometimes a little rough +with very small thorns); pores subregular, circular, with hexagonal +elevated frames, about as broad as the bars; ten to twelve on the half +meridian, sixteen to eighteen on the half equator of each chamber. +Medullary shells (fig. 12_a_) both spherical. (Sometimes, as in the figured +specimen, the shell is somewhat irregular, an individual abnormality.) + +_Dimensions._--Main axis of the cortical shell 0.13 to 0.15; equatorial +axis of the structure 0.08 to 0.09, of each chamber 0.1 to 0.12, pores and +bars 0.005 to 0.007. + +_Habitat._--Pacific, western tropical part, Station 225, depth 4475 +fathoms. + + +3. _Cyphonium ethmarium_, n. sp. + + _Ommatospyris ethmaria_, Haeckel, 1881, Prodromus, p. 462. + +Cortical shell thin walled, with quite smooth surface; pores subregular, +circular (without hexagonal frame), twice as broad as the bars; nine to ten +on the half meridian of each chamber, sixteen to eighteen on its half +equator. Medullary shells both spherical. (This species resembles the +proximal internal chambers of _Peripanartus atractus_, Pl. 40, fig. 7.) + +_Dimensions._--Main axis 0.13, equatorial axis 0.07; greatest breadth 0.09; +pores 0.006, bars 0.003. + +_Habitat._--Equatorial Atlantic, Station 347, surface. + + +{364}4. _Cyphonium trinacrium_, n. sp. + +Cortical shell thick walled, with rough surface; pores subregular, circular +(without hexagonal frame), not broader than the bars; five to six on the +half meridian of each chamber, nine to ten on its half equator. Medullary +shells both compressed, lenticular. This species resembles _Cypassis +entomocora_ vel _Ommatocampe trinacria_, Stoehr, 1880, _loc. cit._, p. 90, +Taf. ii. fig. 1, but has not its external mantle. It may be the ancestral +form of it (both in an ontogenetic and phylogenetic sense). + +_Dimensions._--Main axis 0.11, equatorial axis 0.07; greatest breadth 0.08; +pores 0.005, bars 0.005. + +_Habitat._--Fossil in Tertiary rocks of Sicily, Caltanisetta, Haeckel +(Grotte, Stoehr?). + + +5. _Cyphonium diattus_, n. sp. + +Cortical shell thin walled, with quite smooth surface; pores irregular, +polygonal, mostly pentagonal or hexagonal, three to six times as broad as +the bars; six to seven on the half meridian of the chamber, ten to twelve +on its half equator. Medullary shells both spherical. (Resembles _Cyphonium +profundum_, Ehrenberg, 1872, _loc. cit._, Taf. x. fig. 5, but does not +possess the spines of the surface.) + +_Dimensions._--Main axis 0.13, equatorial axis 0.06; greatest breadth 0.08; +pores 0.005 to 0.012, bars 0.002 to 0.004. + +_Habitat._--Indian Ocean, western part (Zanzibar), Pullen, depth 2200 +fathoms. + + +6. _Cyphonium mammarium_, n. sp. + +Cortical shell thick walled, with smooth surface (sometimes a little +rough); pores irregular, roundish, twice to three times as broad as the +bars; eleven to twelve on the half meridian of each chamber, sixteen to +nineteen on its half equator. Internal medullary shell spherical, external +lenticular compressed, sometimes both spherical or both compressed. +(Resembles the internal cortical twin-shell of _Cyphocolpus virginis_, Pl. +40, fig. 11.) + +_Dimensions._--Main axis 0.14, equatorial axis 0.08, greatest breadth 0.09; +pores 0.004 to 0.006, bars 0.002. + +_Habitat._--South Pacific, Station 285, depth 2375 fathoms. + + + +Subgenus 2. _Ommatocyrtis_, Haeckel. + +_Definition._--Surface of the cortical shell thorny or spiny. + + +7. _Cyphonium hexagonium_, n. sp. + + _Didymocyrtis hexagonia_, Haeckel, 1881, Prodromus. + +Cortical shell thin walled, with spiny surface; pores regular or +subregular, hexagonal, twice to three times as broad as the bars; five to +six on the half meridian, nine to ten on the half equator {365}of each +chamber. Radial spines between them conical, about as long as the pores. +Medullary shells both spherical. + +_Dimensions._--Main axis 0.14, equatorial axis 0.08; greatest breadth of +each chamber 0.1; pores 0.012, bars 0.004. + +_Habitat._--Pacific, central area, Station 268, depth 2900 fathoms. + + +8. _Cyphonium facettarium_, n. sp. + + _Didymocyrtis facettaria_ Haeckel, 1881, Prodromus. + +Cortical shell thick walled, with spiny surface; pores subregular, +circular, with elevated hexagonal frames, twice as broad as the bars; eight +to nine on the half meridian, fourteen to sixteen on the half equator of +each chamber. In the corners of the hexagons (between every three meshes) +arise radial spines, about twice as long as the pores. Both medullary +shells spheroidal compressed. (This species is nearly identical with the +internal cortical twin-shell of _Peripanartus amphiconiscus_, Pl. 40, fig. +5.) + +_Dimensions._--Main axis 0.12, equatorial axis 0.07; greatest breadth of +both chambers 0.09; pores 0.01, bars 0.005, spines 0.02. + +_Habitat._--Western Tropical Pacific, Station 225, depth 4475 fathoms. + + +9. _Cyphonium cribellum_, n. sp. (Pl. 39, fig. 11). + +Cortical shell thick walled, with spiny surface; pores regular, circular, +about as broad as the bars; seven to eight on the half meridian of each +chamber, thirteen to fifteen on its half equator. Radial spines between +them conical, twice as long as the pores. Medullary shells both lenticular. + +_Dimensions._--Main axis 0.11, equatorial axis 0.06; greatest breadth 0.08; +pores and bars 0.004. + +_Habitat._--North Atlantic, Station 353, surface. + + +10. _Cyphonium profundum_, Haeckel. + + _Ommatospyris profunda_, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. + Berlin, p. 297, Taf. viii. fig. 5, Taf. x. fig. 5. + +Cortical shell thin walled, with thorny surface; pores irregular, +polygonal, three to six times as broad as the thin bars; five to six on the +half meridian of each chamber, ten to twelve on its half equator. Thorns +of the surface short. Medullary shells both spherical. + +_Dimensions._--Main axis 0.1, equatorial axis 0.06; greatest breadth 0.07; +pores 0.005 to 0.012, bars 0.002, spines 0.005. + +_Habitat._--Pacific, tropical zone; Philippine Sea, depth 3300 fathoms, +Ehrenberg; Stations 266 to 274, depth 2350 to 2925 fathoms. + + +{366}11. _Cyphonium ceratospyris_, Haeckel. + + _Didymocyrtis ceratospyris_, Haeckel, 1862, Monogr. d. Radiol., p. 445, + pl. xxii. figs. 14-16. + + _Haliomma didymocyrtis_, Haeckel, 1860, Monatsber. d. k. preuss. Akad. d. + Wiss. Berlin, p. 816. + +Cortical shell thin walled, with spiny surface; pores irregular, roundish, +three to nine times as broad as the bars; five to six on the half meridian +of each chamber, eight to nine on its half equator. Spines of the surface +partly very short, partly as long as the largest pores, either radially or +obliquely inserted. Medullary shells both spherical. (Compare the detailed +description and figures also of the soft body in my Monograph, _loc. cit._) + +_Dimensions._--Main axis of the cortical shell 0.12, equatorial axis (in +the stricture) 0.06; greatest breadth 0.08; pores 0.03 to 0.2, bars 0.002 +to 0.006, spines 0.05 to 0.015. + +_Habitat._--Mediterranean (Messina), Canary Islands (Lanzerote), Haeckel. + + + +Genus 157. _Cypassis_,[196] n. gen. + +_Definition._--#Cyphinida# with double cortical shell and double medullary +shell, without polar spines or tubes. + +The genus _Cypassis_ differs from _Cyphonium_ by duplication of the +cortical twin-shell; from the outer surface of the simple twin-shell arise +numerous radial spines, which become connected by anastomosing transverse +branches, and in this manner form an outer envelope or mantle. _Cypassis_ +may also be regarded as a _Cromyodruppa_, the double cortical shell of +which is constricted in the equatorial plane. + + + +Subgenus 1. _Didymospyris_, Haeckel (1881). + +_Definition._--Surface of the shell smooth, without thorns or spines. + + +1. _Cypassis palliata_, n. sp. + +Inner cortical shell thin walled, with regular, circular, +hexagonally-framed pores, twice as broad as the bars; seven to eight on the +half meridian of each chamber, ten to twelve on its half equator. Outer +cortical shell very thin, with smooth surface, and very small, irregular, +roundish pores, twice to five times smaller than those of the inner shell. +Distance between the two cortical shells equals the diameter of the outer +medullary shell, which, like the inner, is spherical. (The network of this +species resembles that of _Peripanartus amphiconiscus_, Pl. 40, fig. 5.) + +_Dimensions._--Main axis of the external cortical shell 0.18, of the +internal 0.12; greatest breadth (in the equator of each chamber) of the +former 0.13, of the latter 0.09; pores of the outer 0.002 to 0.005, of the +inner shell 0.01, bars 0.002 to 0.005. + +_Habitat._--South Pacific, Station 288, surface. + + +{367}2. _Cypassis eucolpos_, n. sp. + +Inner cortical shell thick walled, with regular, circular pores, twice as +broad as the bars (without hexagonal frames); nine to ten on the half +meridian of each chamber, fifteen to seventeen on its half equator. Outer +cortical shell very thin, with smooth surface, and very small, irregular, +roundish pores, twice to three times smaller than those of the inner shell. +Distance between the two cortical shells about one and a half times the +diameter of the inner medullary shell, which, like the outer, is spherical. +(The inner cortical shell resembles that of _Cannartiscus amphiconiscus_, +Pl. 39, fig. 19, but without polar tubes.) + +_Dimensions._--Main axis of the external cortical shell 0.2, of the +internal 0.15; greatest breadth of the former 0.16, of the latter 0.12; +pores of the outer 0.002, of the inner 0.006, bars 0.003. + +_Habitat._--South Atlantic, Station 319, surface. + + + +Subgenus 2. _Didymocyrtis_, Haeckel (1862). + +_Definition._--Surface of the cortical shell thorny or spiny. + + +3. _Cypassis entomocora_, Haeckel. + + _Astromma entomocora_, Ehrenberg, 1847, Mikrogeol., Taf. xxii. fig. 32. + + _Haliomma didymum_, Ehrenberg, 1844, Monatsber. d. k. preuss. Akad. d. + Wiss. Berlin, p. 83. + + ? _Haliomma amphisiphon_, Ehrenberg, 1844, Monatsber. d. k. Akad. d. + Wiss. Berlin, p. 267. + + _Ommatospyris entomocora_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. + Berlin, pp. 66, 74. + + ? _Ommatocampe trinacria_, Stoehr, 1880, Palaeontogr., vol. xxvi. p. 90, + Taf. ii. fig. 1. + + _Didymospyris entomocora_, Haeckel, 1881, Prodromus. + + _Didymocyrtis entomocora_, Haeckel, 1862, Monogr. d. Radiol., p. 445. + +Inner cortical shell thick walled, with regular, circular pores, twice as +broad as the bars (without hexagonal frames); eight to nine on the half +meridian of each chamber, ten to eleven on its half equator. Outer cortical +shell thin walled, with regular, circular pores like those of the inner. +Distance between the two cortical shells equals about twice the diameter of +one pore (or the short axis of the lenticular double medullary shell). +Surface covered with short conical spines (in the figure of Ehrenberg +broken off). + +_Dimensions._--Main axis of the external cortical shell 0.2, of the +internal 0.15; greatest breadth of the former 0.13, of the latter 0.1; +pores of the outer 0.005 to 0.01, of the inner 0.01, bars 0.004; length of +the surface spines 0.005 to 0.01. + +_Habitat._--Fossil in the Tertiary rocks of Barbados, Bermuda, and Sicily +(Caltanisetta); also living in the greatest depth of the Pacific, Stations +268, 225, depth 2900 to 4475. + + +4. _Cypassis puella_, n. sp. (Pl. 39, fig. 13). + + _Didymospyris colpodes_, Haeckel, 1881, Prodromus et Atlas (pl. xxxix., + fig. 13). + +Internal cortical shell thin walled, with irregular, circular pores of very +different size, once to four times as broad as the bars; fourteen to +fifteen on the half meridian of each chamber, eighteen {368}to twenty on +its half equator. Outer cortical shell thin walled, with irregular, +circular pores, only one-third to one-half as large as those of the inner. +Distance between the two shells equals the largest diameter of the double +lenticular medullary shell. Surface of both cortical shells covered with +short conical spines (not longer than the largest pores). + +_Dimensions._--Main axis of the external cortical shell 0.2, of the +internal 0.15, of the central capsule 0.1; greatest breadth of the first +0.14, of the second 0.1, of the third 0.07; pores of the outer shell 0.001 +to 0.005, of the inner 0.002 to 0.01, bars 0.002 to 0.003; length of the +surface spines 0.005 to 0.01. + +_Habitat._--Pacific, central area; Stations 266 to 274, surface; Atlantic, +Canary Islands (Haeckel), Station 354, surface. + + +5. _Cypassis halicora_, n. sp. + +Internal cortical shell thin walled, with irregular, roundish pores, once +to three times as broad as the bars; ten to eleven on half meridian of each +chamber, fourteen to sixteen on its half equator. Outer cortical shell thin +walled, with very delicate network, spindle-like, with conical +prolongations at both poles. Distance between the two shells larger than +the greatest diameter of the double lenticular medullary shell. Surface of +both cortical shells covered with innumerable small thorns. (Resembles +closely _Cyphocolpus virginis_, Pl. 40, fig. 11, but without the third +shell.) + +_Dimensions._--Main axis of the external cortical shell 0.21, of the +internal 0.14, greatest breadth of the former 0.13, of the later 0.09; +pores 0.003 to 0.009; bars of the outer shell 0.001, of the inner 0.004. + +_Habitat._--Indian Ocean, Ceylon (Haeckel), surface. + + + +Genus 158. _Cyphocolpus_,[197] n. gen. + +_Definition._--#Cyphinida# with triple cortical shell and double medullary +shell, without polar spines or tubes. + +The genus _Cyphocolpus_ differs from both foregoing genera by the increased +number of the cortical twin-shells. Whilst these are simple in _Cyphonium_, +double in _Cypassis_, they are triple in _Cyphocolpus_, composed of three +concentric envelopes. The three genera named represent a phylogenetic +series, which is repeated in the ontogenetic development of _Cyphocolpus_. + + +1. _Cyphocolpus didymus_, n. sp. + +Inner cortical shell with circular, subregular pores, twice as broad as the +bars; five to six on the half meridian of each chamber, eight to ten on its +half equator. Middle cortical shell also with subregular, circular pores of +the same size. Outer cortical shell with smooth surface, with more +irregular, roundish pores of very different size. The distance between +every two shells equals the diameter of the inner medullary shell, which, +like the outer, is spheroidal. + +{369}_Dimensions._--Main axis of the outer cortical shell 0.3, of the +middle 0.22, of the inner 0.15; greatest breadth of the inner cortical +shell 0.1, its pores 0.01, bars 0.005. + +_Habitat._--Indian Ocean, Madagascar, Rabbe, surface. + + +2. _Cyphocolpus virginis_, n. sp. (Pl. 40, fig. 11). + + _Zygartus virginis_, Haeckel, 1881, Prodromus et Atlas (pl. xl. fig. 11). + +Inner cortical shell with irregular, roundish pores, twice to three times +as broad as the bars; eleven to twelve on the half meridian of each +chamber, sixteen to eighteen on its half equator. Middle cortical shell +with very delicate network, its irregular, polygonal pores of the same size +as those of the inner, but separated by extremely thin bars. Outer cortical +shell with spiny surface, and with more irregular, roundish pores of +different size. The distance between each two shells is variable, and +attains more than the diameter of the outer medullary shell, which, like +the inner, is spheroidal, slightly compressed. + +_Dimensions._--Main axis of the outer cortical shell 0.26, of the middle +0.22, of the inner 0.14; greatest breadth of the inner cortical shell 0.09, +its pores 0.004 to 0.006, bars 0.002. + +_Habitat._--Pacific, central area, Station 271, surface. + + + +Genus 159. _Cyphinus_,[198] Haeckel, 1881, Prodromus, p. 463. + +_Definition._--#Cyphinida# with simple cortical shell and simple medullary +shell, with two opposite polar spines (or bunches of polar spines) on the +poles of the main axis. + +The genus _Cyphinus_ differs from _Cyphanta_ by the development of two +opposite spines (or bunches of spines) on both poles of the main axis. It +simulates therefore the bipolar formation of _Stylartus_, and differs from +this in the possession of a medullary shell. + + + +Subgenus 1. _Cyphinoma_, Haeckel. + +_Definition._--On both poles of the main axis only one single large spine. + + +1. _Cyphinus amphacanthus_, n. sp. + +Cortical shell with smooth surface, and circular, regular pores, twice as +broad as the bars; five to six pores on the half meridian of each chamber, +ten to twelve on its half equator. On both poles of the main axis, one +single, very strong, conical spine, about half as long as this axis, and +half as broad at the base as the spherical medullary shell. + +_Dimensions._--Main axis of the cortical shell (without spines) 0.2, +greatest breadth (in the equator of each chamber) 0.1; pores 0.006, bars +0.003; length of the polar spines 0.1, basal thickness of them 0.02. + +_Habitat._--North Pacific, Station 244, depth 2900 fathoms. + + +{370}2. _Cyphinus dixiphus_, n. sp. + +Cortical shell with rough surface, and irregular, roundish pores, twice to +four times as broad as the bars; eight to nine pores on the half meridian +of each chamber, twelve to fourteen on its half equator. On both poles of +the main axis, one single, strong, conical spine, with prominent edges at +the base, and nearly as broad as the spherical medullary shell, nearly as +long as the main axis. + +_Dimensions._--Main axis (without spines) 0.18, greatest breadth 0.13; +pores 0.003 to 0.008, bars 0.002; length of the polar spines 0.16, basal +thickness 0.03. + +_Habitat._--South Pacific, Station 295, depth 1500 fathoms. + + + +Subgenus 2. _Cyphinura_, Haeckel. + +_Definition._--On both poles of the main axis a bunch or circle of several +spines. + + +3. _Cyphinus amphilophus_, n. sp. (Pl. 39, fig. 14). + + _Cyphinidium amphilophus_, Haeckel, 1882, Atlas (pl. xxxix. fig. 14). + +Cortical shell thick walled, with rough surface, and subregular, circular +pores of different size, twice to five times as broad as the bars; nine to +ten pores on the half meridian of each chamber, twelve to fourteen on its +half equator. On both poles of the main axis a bunch of six to eight strong +conical spines, the largest of which are about as long as the greatest +breadth of the shell; their basal part is furrowed, and nearly half as +thick as the spherical medullary shell. + +_Dimensions._--Main axis of the cortical shell (without spines) 0.18 to +0.2, greatest breadth 0.1 to 0.12; pores 0.004 to 0.01, bars 0.002; length +of the polar spines 0.04 to 0.12, basal thickness 0.02 to 0.04. + +_Habitat._--Pacific, central area, Station 271, depth 2425 fathoms. + + +4. _Cyphinus penicillatus_, Haeckel. + + _Ommatospyris penicillata_, Ehrenberg, 1872, Monatsber. d. k. preuss. + Akad. d. Wiss. Berlin, p. 318; Abhandl. d. k. Akad. d. Wiss. Berlin, Taf. + viii. fig. 4. + +Cortical shell thin walled, with rough surface, and irregular, polygonal +pores, six to eight times as broad as the bars; five to six pores on the +half meridian of each chamber, nine to ten on its half equator. Around both +poles of the main axis a polar circle of eight to ten divergent radial +spines, scarcely thicker than the bars, and about as long as the diameter +of the spherical medullary shell. (In the figure of Ehrenberg the network +is too thin and the spines too short.) + +_Dimensions._--Main axis (without spines) 0.1, greatest breadth 0.09; pores +0.008 to 0.014, bars 0.001 to 0.002; length of the spines 0.02 to 0.04. + +_Habitat._--Pacific, Philippine Sea, 3300 fathoms, Ehrenberg; Station 206, +depth 2100 fathoms. + + + +{371}Genus 160. _Cyphinidium_,[199] n. gen. + +_Definition._--#Cyphinida# with simple cortical shell and double medullary +shell, with two opposite polar spines (or bunches of polar spines) on the +poles of the main axis. + +The genus _Cyphinidium_ differs from _Cyphinus_ only in the duplication of +the medullary shell, which is composed of two concentric spheres or +somewhat compressed lenticular spheroids. It exhibits therefore the same +relation to _Cyphinus_ that _Stylatractus_ in the Druppulida bears to +_Lithatractus_. Possibly the two former genera are derived from the two +latter by an annular constriction in the equatorial plane. + + + +Subgenus 1. _Cyphinidoma_, Haeckel. + +_Definition._--On both poles of the cortical shell one single polar spine +or a bunch of polar spines. + + +1. _Cyphinidium amphistylium_, n. sp. + +Cortical shell thick walled, with smooth surface, and subregular, circular +pores, twice to three times as broad as the bars; eight to ten on the half +meridian, sixteen to eighteen on the half equator of each chamber. Both +medullary shells spherical. The cortical shell resembles very much that of +_Cannartiscus amphiconiscus_ (Pl. 39, fig. 19), but exhibits instead of the +hollow polar tubes two strong solid polar spines of conical form, half as +long as the main axis, and as broad at the base as the inner medullary +shell. + +_Dimensions._--Main axis of the cortical shell (without polar spines) 0.14, +greatest breadth 0.1; pores 0.008, bars 0.004; length of the polar spines +0.08, basal thickness 0.02. + +_Habitat._--North Pacific, off Japan, Station 241, depth 2300 fathoms. + + +2. _Cyphinidium apicatum_, Haeckel. + + _Ommatospyris apicata_, Ehrenberg, 1872, Monatsber. d. k. preuss. Akad. + d. Wiss. Berlin, p. 317. + +Cortical shell thin walled, with thorny surface, and irregular, polygonal +pores, three to five times as broad as the thin bars; eight to nine on the +half meridian, thirteen to fifteen on the half equator of each chamber. On +both poles a bunch of four to eight strong conical spines, the central of +which (in the main axis) is much larger than the others, and twice as long +as the diameter of the outer spheroidal medullary shell; size and number of +the polar spines is very variable (commonly five to six). + +{372}_Dimensions._--Main axis (without spines) 0.12, greatest breadth 0.08; +pores 0.005 to 0.01, bars 0.002; length of the polar spines 0.02 to 0.06, +basal thickness 0.01. + +_Habitat._--Northern Pacific, Californian Sea, depth 2500 fathoms, +Ehrenberg; Station 253, depth 3125 fathoms. + + + +Subgenus 2. _Cyphinidura_, Haeckel. + +_Definition._--On both poles of the cortical shell, a circle of divergent +polar spines. + + +3. _Cyphinidium coronatum_, n. sp. + +Cortical shell with thorny surface, and irregular, roundish pores, twice to +four times as broad as the bars; seven to eight on the half meridian, +eleven to thirteen on the half equator of each chamber. Around both poles +of the main axis occurs a circle of ten to twelve strong, radially +divergent spines, about as long as the diameter of the outer medullary +shell, which, like the inner, is spheroidal. (This species is identical +with the younger developmental stage of _Panicium coronatum_, Pl. 40, fig. +4, before the formation of two distal chambers.) + +_Dimensions._--Main axis 0.12, greatest breadth 0.1; pores 0.008 to 0.016, +bars 0.004; length of the polar spines 0.02, thickness 0.005. + +_Habitat._--Pacific, central area, Stations 270 to 274, depth 2350 to 2925 +fathoms. + + + +Genus 161. _Cannartiscus_,[200] n. gen. + +_Definition._--#Cyphinida# with simple cortical shell and simple medullary +shell, with two hollow fenestrated polar tubes, opposite on both poles of +the main axis. + +The genus _Cannartiscus_ differs from _Cyphanta_ in the development of two +hollow fenestrated tubes, opposite on both poles of the main axis. It +simulates therefore the characteristic formation of _Cannartus_, and +differs from this Artiscid in the possession of a medullary shell. + + +1. _Cannartiscus amphiconiscus_, n. sp. (Pl. 39, fig. 19). + + _Cannartidium amphiconiscus_, Haeckel, 1882, Atlas (pl. xxxix. fig. 19). + +Cortical shell thick walled, smooth, with regular, circular pores, twice as +broad as the bars; nine to ten on the half meridian, sixteen to eighteen on +the half equator of each chamber. Polar tubes conical, about as long as one +single chamber, on the base somewhat broader than the simple spherical +medullary shell. Pores of the tubes only one-third as great as those of the +chambers. + +_Dimensions._--Main axis of the cortical shell (without tubes) 0.14, +greatest breadth 0.1; {373}pores 0.008, bars 0.004. Length of the polar +tubes 0.07, basal breadth 0.04; pores 0.003, bars 0.002. + +_Habitat._--North Pacific, Station 253, depth 3125 fathoms. + + +2. _Cannartiscus amphicylindrus_, n. sp. + +Cortical shell thick walled, rough, with subregular, circular pores, twice +to four times as broad as the bars; six to seven on the half meridian, ten +to twelve on the half equator of each chamber. Polar tubes cylindrical, on +the distal end open (broken off?) nearly as long as the main axis, somewhat +narrower than the spherical medullary shell. Pores of the tubes much +smaller than those of the chambers. + +_Dimensions._--Main axis (without tubes) 0.17, greatest breadth 0.12; pores +0.006 to 0.012, bars 0.003. Length of the polar tubes 0.15, breadth of them +0.03; pores 0.003, bars 0.002. + +_Habitat._--Pacific, central area, Station 268, 2900 fathoms; the same form +occurs fossil in the rocks of Barbados. + + + +Genus 162. _Cannartidium_,[201] n. gen. + +_Definition._--#Cyphinida# with simple cortical shell and double medullary +shell, with two hollow fenestrated polar tubes, opposite on both poles of +the main axis. + +The genus _Cannartidium_ differs from _Cannartiscus_ and _Cannartus_ in the +duplication of the medullary shell, which is composed of two concentric +spheres or compressed lenticular spheroids. The three genera named form +therefore one morphological series, with identical cortical shell, and only +differing in the absence or presence of a simple or double medullary shell. + + + +Subgenus 1. _Cannartidella_, Haeckel. + +_Definition._--Surface of the cortical shell smooth or a little rough, but +without spines or fenestrated protuberances. + + +1. _Cannartidium amphiconicum_, n. sp. + +Cortical shell thick walled, smooth with regular circular pores twice as +broad as the bars; eight to nine on the half meridian, fifteen to sixteen +on the half equator of each chamber. Polar tubes conical, with smaller +pores, tapering towards the closed apex, about as long as one single +chamber, at the base one-third as broad as the equatorial constriction. +Both concentric medullary shells spherical. (Nearly identical with +_Cannartiscus amphiconiscus_, Pl. 39, fig. 19, but differs in the +possession of the double medullary shell.) + +{374}_Dimensions._--Main axis of the cortical shell (without tubes) 0.15, +greatest breadth 0.11; pores 0.009, bars 0.004; length of the polar tubes +0.08, basal breadth 0.04. + +_Habitat._--Pacific, western tropical part, Station 225, depth 4475 +fathoms. + + +2. _Cannartidium amphicanna_, Haeckel. + + "Curious twin Polycystin," Bury, 1862, Polycystins of Barbados, pl. xx. + fig. 4. + +Cortical shell thick walled, rough, with regular, circular pores, not +broader than the bars; six to seven on the half meridian, ten to twelve on +the half equator of each chamber. Polar tubes cylindrical, at the distal +end open (broken off?), nearly as long as the main axis, about one-third as +broad as the equatorial constriction. Both concentric medullary shells +spherical. + +_Dimensions._--Main axis 0.14, greatest breadth 0.11; pores and bars 0.005; +length of the polar tubes 0.13, breadth of them 0.03. + +_Habitat._--Fossil in the Barbados deposits. + + +3. _Cannartidium amphisiphon_, Haeckel. + + ? _Haliomma amphisiphon_, Ehrenberg, 1844, Monatsber. d. k. preuss. Akad. + d. Wiss. Berlin, p. 267. + +Cortical shell thick walled, rough, with irregular, roundish pores, twice +to five times as broad as the bars; five to six on the half meridian, nine +to ten on the half equator of each chamber. Polar tubes conical, with +smaller pores, about as long as one single chamber, half as broad at the +base as the equatorial constriction. (This deep-sea form is probably +identical with that fossil species which Ehrenberg, in 1844, described as +_Haliomma amphisiphon_, and which he afterwards, in 1875, erroneously +identified with his _Astromma entomocora_ (= _Cypassis entomocora_). But +the figure given of the latter is quite different from the given diagnosis +of the former.) + +_Dimensions._--Main axis of the cortical shell (without tubes) 0.13, +greatest breadth 0.1; pores 0.006 to 0.12, bars 0.003; length of the polar +tubes 0.07, basal breadth of them 0.04. + +_Habitat._--Tropical Atlantic, Antilles, Station 24, depth 390 fathoms; +fossil in the Tertiary rocks of Bermuda. + + +4. _Cannartidium bicinctum_, n. sp. (Pl. 39, fig. 18). + +Cortical shell thick walled, with a thickened ring-shaped protuberance in +the greatest breadth of both chambers. Pores subregular, circular, twice to +three times as broad as the bars; seven to eight on the half meridian, +thirteen to fifteen on the half equator of each chamber. Polar tubes +conical, with smaller pores, somewhat shorter than the greatest breath, +nearly as thick at the base as the outer spheroidal medullary shell (fig. +18_a_). + +_Dimensions._--Main axis (without tubes) 0.12, greatest breadth 0.08; pores +0.003 to 0.006, bars 0.002; length of the polar tubes 0.08, basal thickness +0.03. + +_Habitat._--South Atlantic, Station 332, depth 2200 fathoms. + + + +{375}Subgenus 2. _Cannartidissa_, Haeckel. + +_Definition._--Surface of the cortical shell with conical fenestrated +protuberances in the greatest breadth of both chambers. + + +5. _Cannartidium mammiferum_, n. sp. (Pl. 39, fig. 16). + +Cortical shell-thin walled, having a circle of six to eight conical +protuberances in the greatest breadth of both chambers, each of which +exhibits a central apical pore, surrounded by a circle of six to eight +oblique larger pores. Between the protuberances occur nine to ten pores on +the half meridian of each chamber, circular, subregular, twice to three +times as broad as the bars. Polar tubes cylindrical, conical at the closed +end, with smaller pores, about as long as the greatest breadth of the +chambers, as broad as the spherical outer medullary shell. + +_Dimensions._--Main axis (without tubes) 0.13, greatest breadth (including +the protuberances) 0.1; pores 0.005 to 0.008, bars 0.003; length of the +polar tubes 0.09, basal thickness 0.02. + +_Habitat._--Pacific, central area, Station 268, depth 2900 fathoms. + + +6. _Cannartidium mastophorum_, n. sp. (Pl. 39, fig. 17). + +Cortical shell thin walled, of the same form and structure as in the +foregoing species, differs from this mainly in the form of the polar tubes, +which are not cylindrical but conical, tapering gradually from the base +towards the closed apex. Besides this, the conical protuberances (six in +the greatest periphery of each chamber) are more regular and acute, with +smaller and more numerous pores. Both medullary shells are here also +spherical. + +_Dimensions._--Main axis (without tubes) 0.14, greatest breadth (including +the protuberances) 0.13; pores 0.006 to 0.009, bars 0.004; length of the +polar tubes 0.07, basal thickness 0.03. + +_Habitat._--Pacific, central area, Station 266, depth 2750 fathoms. + + + +Family XVI. #PANARTIDA#, Haeckel (Pl. 40, figs. 1-9). + +_Definition._--#Prunoidea# with a four-jointed cortical shell, the external +shell being divided by three parallel transverse constrictions into four +chambers, in the centre enclosing two internal concentric shells (medullary +shells). Central capsule cylindrical, commonly four-jointed (with three +transverse annular constrictions). + +The family #Panartida# (Pl. 40, figs. 1-9) is characterised by its +four-jointed cortical shell, constantly composed of four chambers, lying +one behind another in the elongated main axis. They are separated by three +ring-like constrictions lying in three parallel transverse planes; the +middle of these is the equatorial plane. In the centre of this latter lies +constantly a double medullary shell. + +The Panartida must be derived from the Cyphinida by further increase in the +longitudinal or main axis, and by repetition of the equatorial constriction +in two transverse planes parallel to it and at an equal distance from it. + +{376}_The Medullary Shell_ is always double in this family, composed of two +small concentric shells lying in the middle of the central capsule. They +are either spherical or lenticular, compressed towards both poles of the +main axis; sometimes the inner is spherical, the outer lenticular. From the +equatorial circumference of the latter starts a number of radial beams, +which perforate the central capsule, and are inserted into the equatorial +constriction of the cortical shell. Commonly all radial beams lie in the +equatorial plane, sometimes also a part of them on both sides of it. + +_The Cortical Shell_ is constantly composed of four completely latticed +chambers, which are only separated by the three annular constrictions. In +many species all four chambers have the same form and size (Pl. 40, fig. +3), but in the greater number of species both proximal (or central) +chambers are different in size, shape, or structure from both distal (or +polar) chambers. The cortical shell is either simple or double, composed of +two concentric four-jointed shells; rarely it is triple or multiple, +composed of three or more shells fitting one inside the other. Very often +the outer cortical shell is incomplete, and only developed around the two +proximal chambers of the complete inner cortical shell, both distal +chambers of the latter remaining simple. + +On both poles of the main axis often are developed solid spines +(_Panicium_, Pl. 40, fig. 4) or hollow fenestrated tubes (_Panarium_, Pl. +40, fig. 9), as in the foregoing families. Besides this, the surface of the +cortical shell may be armed with spines. + +_The Central Capsule_ of the Panartida is always cylindrical, on both poles +hemispherical; commonly it is more or less distinctly four-jointed, with +three ring-like constrictions corresponding to those of the enclosing +cortical shell. From the inner surface of the latter it is separated by a +thinner or thicker jelly-mantle. + +_Synopsis of the Genera of Panartida._ + + On both poles of the main { Cortical shell simple, 163. _Panartus_. + axis neither peculiar { + polar spines nor { Cortical shell double or + fenestrated tubes. { triple, 164. _Peripanartus_. + + On both poles of the main { Cortical shell simple, 165. _Panicium_. + axis a large apical { + spine or a group of { Cortical shell double or + polar spines. { triple, 166. _Peripanicium_. + + On both poles of the main { Cortical shell simple, 167. _Panarium_. + axis a conical or { + cylindrical fenestrated { Cortical shell double or + tube. { triple, 168. _Peripanarium_. + + + +Genus 163. _Panartus_,[202] n. gen. + +_Definition._--#Panartida# with simple cortical shell and double medullary +shell, without polar spines or tubes on both poles of the main axis. + +{377}The genus _Panartus_ represents the common ancestral form of all +Panartida, as all other genera of this subfamily must be derived from it +and are only further developmental stages, from an ontogenetic as well as +from a phylogenetic point of view. The cortical shell of _Panartus_ is +constantly composed of four fenestrated chambers jointed to one another in +the main axis; both proximal chambers are separated from one another by the +equatorial ring-like constriction, in the centre of which lies the double +medullary shell; both distal chambers are separated from the former by two +other annular constrictions (in planes parallel to the equatorial plane). +All four chambers may exhibit the same (kidney-shaped) form and structure +(in the subgenera _Panartella_ and _Panartoma_); or the proximal chamber +may differ more or less in shape and size from the distal (in the subgenera +_Panartissa_ and _Panartura_). The outer surface of the cortical shell is +sometimes smooth (as in _Panartella_ and _Panartissa_), at other times +spiny or thorny (as in _Panartoma_ and _Panartura_). The double medullary +shell is sometimes spherical, or commonly compressed at both poles and +spheroidal or lenticular. + + + +Subgenus 1. _Panartella_, Haeckel. + +_Definition._--Surface of the cortical shell smooth, without spines or +thorns. All its four chambers exhibit nearly the same form and structure. + + +1. _Panartus tetraplus_, n. sp. + +All four chambers of the cortical shell of the same form, size, and +structure, kidney-shaped, twice as broad as long. Pores rather regular, +hexagonal, all nearly of the same size and form, four times as broad as the +thin bars; five to six pores on the half meridian, nine to ten on the half +equator of each chamber. Surface of the cortical shell smooth, its main +axis three times as long as its equatorial axis (in the median +constriction). Both concentric medullary shells spherical; the equatorial +axis of the outer half as long as that of the cortical shell. (All four +chambers of this species have the same appearance as the two proximal +chambers of _Panartus diploconus_, Pl. 40, fig. 1.) + +_Dimensions._--Main axis of the cortical shell 0.21, equatorial axis 0.07; +breadth of every chamber 0.09; meshes 0.013, bars 0.03. + +_Habitat._--Central area of the Pacific, Stations 270 to 274, depth 2350 to +2925 fathoms. + + +2. _Panartus tetracolus_, n. sp. + +All four chambers of the cortical shell of the same form, size, and +structure, kidney-shaped, twice as broad as long. Pores regular, circular, +with hexagonal frame, twice as broad as the bars; six to seven pores on the +half meridian, ten to twelve on the half equator of each chamber. Surface +of the cortical shell smooth; its main axis three times as long as the +equatorial axis. Both concentric medullary shells spheroidal, somewhat +compressed at both poles; the equatorial axis {378}of the outer almost +equals half that of the cortical shell. (All four chambers of this species +exhibit the structure of the two proximal chambers of _Peripanartus +amphiconus_, Pl. 40, fig. 5.) + +_Dimensions._--Main axis of the cortical shell 0.24, equatorial axis 0.08; +breadth of every chamber 0.01; meshes 0.01, bars 0.005. + +_Habitat._--Equatorial Atlantic, Station 348, depth 2450 fathoms. + + +3. _Panartus tetrameres_, n. sp. + +All four chambers of the cortical shell of the same form, size, and +structure, kidney-shaped, twice as broad as long. Pores rather regular, +circular, without hexagonal frame, about as broad as the bars; five to six +pores on the half meridian, ten to twelve on the half equator of each +chamber. Surface of the cortical shell smooth, its main axis three times as +long as the equatorial axis. Both concentric medullary shells spheroidal, +compressed; the outer half as broad as the constriction. (This species is +very much like _Ommatocampe increscens_, Stoehr, 1880, _loc. cit._, Taf. +ii. fig. 2, and may be considered as the ancestral form of it.) + +_Dimensions._--Main axis of the cortical shell 0.2, equatorial axis 0.065; +breadth of every chamber 0.08; meshes and bars 0.005. + +_Habitat._--Fossil in the Tertiary rocks of Sicily, Caltanisetta, Haeckel. + + +4. _Panartus tetraphalangus_, n. sp. + +All four chambers of the cortical shell of the same form, size, and +structure, kidney-shaped, twice as broad as long. Pores irregular, +polygonal (mostly pentagonal or hexagonal), four to eight times as broad as +the thin bars; four to seven on the half meridian, eight to fifteen on the +half equator of each chamber. Surface of the cortical shell smooth, its +main axis three times as long as its equatorial axis. Both concentric +medullary shells compressed, the outer, half as broad as the constriction. + +_Dimensions._--Main axis of the cortical shell 0.26, equatorial axis 0.09; +breadth of every chamber 0.12; meshes 0.003 to 0.02, bars 0.001 to 0.003. + +_Habitat._--Fossil in the rocks of Barbados, Haeckel. + + +5. _Panartus tetrathalamus_, n. sp. (Pl. 40, fig. 3). + +All four chambers of the cortical shell of the same form, size, and +structure, kidney-shaped, twice as broad as long. Pores irregular, +roundish, twice to three times as broad as the bars; a circle of larger +pores at the base of both distal chambers; five to six pores on the half +meridian, ten to twelve on the half equator of each chamber. Surface of the +cortical shell smooth; its main axis two and a half times as long as the +equatorial axis. Both medullary shells spheroidal, compressed, the outer +one-third as broad as the constriction. (In the specimen figured spines +begin to arise from both distal chambers; this forms a transition to +_Panartus quadrijugus_.) + +_Dimensions._--Main axis of the cortical shell 0.18, equatorial axis 0.07; +breadth of every chamber 0.09; meshes 0.003 to 0.01, bars 0.002 to 0.004. + +_Habitat._--Cosmopolitan; Mediterranean, Atlantic, Pacific, in various +depths. + + + +{379}Subgenus 2. _Panartissa_. + +_Definition._--Surface of the cortical shell smooth, without spines or +thorns. Both its proximal chambers differ in form and structure from the +two distal chambers. + + +6. _Panartus diploconus_, n. sp. (Pl. 40, fig. 1). + +Both proximal chambers nearly ellipsoidal, one and a half times as broad as +long, with regular hexagonal pores, four times as broad as the bars; five +to six pores on the half meridian, nine to ten on the half equator of each +chamber. Both distal chambers conical, with a circle of ten to twelve large +square pores at the base; the other pores very small and numerous, +roundish, sixteen to twenty in the height of each cone, and the same number +on the half periphery of its base. Both concentric medullary shells +compressed, the outer, half as broad as the constriction of the cortical +shell, the surface of which is quite smooth. + +_Dimensions._--Total length of the shell (or main axis) 0.34; greatest +breadth of each chamber 0.09; pores of the proximal chambers 0.013, bars +0.003; pores and bars of the distal chambers 0.003; large basal square +pores 0.02. + +_Habitat._--Pacific, central area, Station 272, depth 2600 fathoms. + + +7. _Panartus amphiconus_, n. sp. + +Both proximal chambers nearly kidney-shaped, one and a half times as broad +as long, with regular, circular pores, with hexagonal frames, twice as +broad as the bars; six to seven pores on the half meridian, ten to twelve +on the half equator of each chamber. Both distal chambers conical, with a +circle of ten to twelve very large pores at the base; the other pores very +small, roundish, ten to fifteen in the height of each cone, twenty to +thirty on the half basal periphery. Both concentric medullary shells +compressed, the outer one-third as broad as the constriction of the +cortical shell, whose surface is smooth. (This species resembles +_Peripanartus amphiconus_, Pl. 40, fig. 5, but is without the surface +spines and the outer envelope.) + +_Dimensions._--Total length of the shell 0.28; greatest breadth of the +proximal chambers 0.1, of the distal chambers 0.14; pores of the former +0.008, of the latter 0.004; bars of both 0.003 to 0.005. + +_Habitat._--North Pacific, Station 244, depth 2900 fathoms. + + +8. _Panartus fusiformis_, n. sp. + +Both proximal chambers nearly ellipsoidal, one and a half times as long as +broad, with irregular, roundish pores, twice to three times as broad as the +bars; eight to ten pores on the half meridian, twelve to fifteen on the +half equator of each chamber. Both distal chambers hemiellipsoidal or +egg-shaped, somewhat higher and narrower than the proximal chambers, with a +circle of larger square pores at their base; the other pores roundish and +very irregular. Both medullary shells spheroidal, one-third as broad as the +constriction of the cortical shell, whose surface is quite smooth. (This +{380}species is similar to _Peripanartus atractus_, Pl. 40, fig. 7, but is +without the superficial spines and the equatorial girdle-like envelope of +the latter.) + +_Dimensions._--Total length of the shell 0.25 to 0.3; greatest breadth (in +the equator of the proximal chambers) 0.08 to 0.1; pores of the proximal +chambers 0.008 to 0.012, pores of the distal chambers half their size, bars +0.002 to 0.006. + +_Habitat._--North Pacific, Station 237, surface. + + +9. _Panartus profundissimus_, Haeckel. + + _Ommatocampe profundissima_, Ehrenberg, 1872, Abhandl. d. k. Akad. d. + Wiss. Berlin, p. 297, Taf. viii. fig. 6. + +Both proximal chambers nearly ellipsoidal, with irregular, polygonal pores, +six to eight times as broad as the bars; four to five pores on the half +meridian, eight to nine on the half equator of each chamber. Both distal +chambers hemispherical, with a very delicate irregular network. Medullary +shells spherical; surface of the shell smooth. + +_Dimensions._--Total length of the shell 0.15; greatest breadth in the +equator of the proximal chambers 0.08; pores of the proximal chambers +0.015, bars 0.002. + +_Habitat._--Philippine Sea, depth 3300 fathoms, Ehrenberg; Station 213, +depth 2050 fathoms. + + + +Subgenus 3. _Panartoma_, Haeckel. + +_Definition._--Surface of the cortical shell thorny, covered with scattered +spines. All its four chambers exhibit the same form and structure. + + +10. _Panartus quadriceps_, n. sp. + +All four chambers of the cortical shell of the same form, size, and +structure, kidney-shaped, twice as broad as long. Pores rather regular, +circular, with hexagonal frames, twice to three times as broad as the bars; +six to seven pores on the half meridian, ten to twelve on the half equator +of each chamber. Surface spiny; from the corners of the hexagonal frames +(between every three pores) arise short radial spines. Both medullary +shells spherical, the outer one-third as broad as the constriction of the +cortical shell. (All the four chambers of this species have the same form +as the two proximal chambers of _Peripanartus amphiconus_, Pl. 40, fig. 5.) + +_Dimensions._--Main axis of the cortical shell 0.24, equatorial axis 0.08; +meshes 0.01, bars 0.003 to 0.005; length of the spines 0.01 to 0.02. + +_Habitat._--Pacific, central area, Station 274, depth 2750 fathoms. + + +11. _Panartus quadrijugus_, n. sp. + +All four chambers of the cortical shell of the same form and size, +kidney-shaped, twice as broad as long. Pores irregular, roundish, twice to +three times as broad as the bars; a circle of larger pores at the base of +both distal chambers; six to eight pores on the half meridian, twelve to +{381}fourteen on the half equator of each chamber. Surface spiny, +everywhere covered with small irregular thorns. (This species differs from +the smooth _Panartus tetrathalamus_, Pl. 40, fig. 3, almost entirely by the +thorny surface.) + +_Dimensions._--Main axis 0.2, equatorial axis 0.08; breadth of every +chamber 0.1; meshes 0.005 to 0.01, bars 0.003, spines 0.01 to 0.02. + +_Habitat._--Cosmopolitan; on the surface of the Atlantic, Indian, and +Pacific Oceans. + + +12. _Panartus quadrigeminus_, n. sp. + +All four chambers of the cortical shell nearly of the same size and form, +kidney-shaped, twice as broad as long. Pores irregular, polygonal (mostly +pentagonal or hexagonal), six to eight times as broad as the thin bars; +five to seven on the half meridian, twelve to sixteen on the half equator +of each chamber. Surface of the cortical shell spiny, covered with numerous +irregularly scattered, often oblique, bristle-like thorns. + +_Dimensions._--Main axis 0.27, equatorial axis 0.1; breadth of each chamber +0.13; meshes 0.01 to 0.02, bars 0.001 to 0.005. + +_Habitat._--Cosmopolitan; surface of the Atlantic and Pacific, many +Stations. + + + +Subgenus 4. _Panartura_, Haeckel. + +_Definition._--Surface of the cortical shell thorny, covered with scattered +spines. Both its proximal chambers differ in form or structure from the two +distal chambers. + + +13. _Panartus spinosus_, n. sp. + +Both proximal chambers nearly ellipsoidal, with regular, circular pores +enclosed by hexagonal frames. Both distal chambers conical, with a circle +of ten to twelve large square pores at the base; the other pores small, +roundish. The cortical shell of this species is quite the same as that of +_Panartus amphiconus_ (Pl. 40, fig. 5), but differs in the absence of the +external envelope (or the second cortical shell), and is covered with +short, conical spines on the whole surface. + +_Dimensions._--Total length of the cortical shell 0.25, greatest breadth +(on the base of the distal chambers) 0.12; meshes of the proximal chambers +0.008, of the distal chambers 0.004; bars 0.002 to 0.04, spines 0.01 to +0.02. + +_Habitat._--North Pacific, Station 240, surface. + + +14. _Panartus setosus_, Haeckel. + + _Ommatocampe setosa_, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. + Berlin, p. 297, Taf. viii. fig. 7. + +Both proximal chambers kidney-shaped, broader than the two hemispherical +distal chambers. Meshes of the cortical shell irregular, polygonal, or +subregular hexagonal; at the base of each {382}distal chamber a circle of +large square meshes. The breadth of the pores is eight to twelve times that +of the bars between them. The whole surface is covered with small +bristle-like spines. + +_Dimensions._--Total length of the cortical shell 0.14, greatest breadth +(in the equator of each proximal chamber) 0.07; meshes 0.008 to 0.015, bars +0.002, spines 0.01. + +_Habitat._--Pacific (Philippine and Californian Sea) 3300 and 2300 fathoms, +Ehrenberg; Station 200, depth 250 fathoms; Station 253, depth 3125 fathoms. + + +15. _Panartus pluteus_, n. sp. (Pl. 40, fig. 2). + +Both proximal chambers kidney-shaped, with irregular, roundish pores, twice +to four times as broad as the bars; their surface everywhere covered with +short conical thorns. From both polar circles arise ten to twelve radial +rods, which bear a fenestrated cap, and form thus either the beginning of a +second, external, cortical shell, or (if remaining thus) two imperfect +distal chambers. The spherical segment, which forms their surface, is +concentric with the proximal chambers, is perforated by the same irregular, +roundish pores, and covered with numerous bristle-like spines. + +_Dimensions._--Main axis of the cortical shell 0.17, equatorial axis (in +the constriction) 0.06; distance between the proximal and distal chambers +0.03; pores 0.003 to 0.01, bars 0.003 to 0.005. + +_Habitat._--Pacific, central area, Station 272, depth 2600 fathoms. + + + +Genus 164. _Peripanartus_,[203] n. gen. + +_Definition._--#Panartida# with double cortical shell and double medullary +shell, without polar spines or tubes on both poles of the main axis. + +The genus _Peripanartus_ differs from _Panartus_ only in the development of +an outer reticulated envelop, which mantle-like surrounds the shell and +represents a second or external cortical shell. This mantle or veil +envelops either the whole internal cortical shell or only both proximal +chambers. _Peripanartus_ exhibits the same relation to _Panartus_ as in the +foregoing ancestral family _Cypassis_ bears to _Cyphonium_. + + + +Subgenus 1. _Peripanartula_, Haeckel. + +_Definition._--Surface of the outer cortical shell smooth, without spines +or thorns. + + +1. _Peripanartus palliatus_, n. sp. + +Internal cortical shell with four kidney-shaped chambers of equal size and +similar form, identical with the cortical shell of _Panartus tetrathalamus_ +and _Panartus quadrijugus_ (Pl. 40, fig. 3), with irregular, roundish +pores, twice to three times as broad as the bars. It differs from these two +species {383}only by the external cortical shell enveloping the whole +internal one, in the same manner as in _Peripanartus cylindrus_ (Pl. 40, +fig. 6). The two shells are connected by numerous radial rods. The surface +of the outer cortical shell is quite smooth, its irregular, roundish pores +about half as large as those of the inner cortical shell. + +_Dimensions._--Main axis of the external cortical shell 0.27, of the +internal 0.2; greatest breadth of the former (in the equator of each +chamber) 0.13, of the latter 0.09; pores of the external cortical shell +0.002 to 0.004, of the internal 0.004 to 0.008; bars of the former 0.002, +of the latter 0.003. + +_Habitat._--Pacific, central area, Stations 271, 272, depth 2425 to 2600 +fathoms. + + +2. _Peripanartus laevigatus_, n. sp. + +Internal cortical shell with four unequal chambers, both proximal +kidney-shaped (with subregular polygonal pores, twice to three times as +broad as the bars), both distal nearly hemispherical, with subregular, +roundish pores of half that size. External cortical shell envelops only the +proximal chambers, and appears as the direct continuation of the internal +shell of the distal chambers, with the same small roundish pores. The outer +surface is quite smooth. This species has nearly the same structure as +_Peripanicium amphicorona_ (Pl. 40, fig. 8), but differs from it by the +absence of the polar spine-circles, and by the perfect smoothness of the +surface. + +_Dimensions._--Main axis of the shell 0.25, greatest breadth (in the +equator of the proximal chambers) 0.15; equatorial stricture of the +external shell 0.10, of the internal 0.07; pores of the internal shell of +the proximal chambers 0.013, of the external 0.006; bars 0.003. + +_Habitat._--Pacific, central area, Station 274, depth 2750 fathoms. + + +3. _Peripanartus amphiconus_, n. sp. (Pl. 40, fig. 5). + +Inner cortical shell with four very unequal chambers; both proximal +chambers kidney-shaped (with regular, circular, hexagonally framed pores, +twice as broad as the bars); both distal chambers conical, with a circle of +large square pores at the base, the other pores very small, roundish. +Outer cortical shell very thin, quite smooth, with irregular, roundish +pores, envelops in younger specimens only the distal chambers. But the +radial spines on the surface of the internal cortical shell of the proximal +chambers indicate that these will also be afterwards enclosed by the +growing of the external shell. This species exhibits the progressive +(ontogenetic as well as phylogenetic) development of _Panartus amphiconus_. + +_Dimensions._--Main axis of the outer cortical shell 0.3, its greatest +breadth (at the prominent distal ends of the radial rods between the large +square pores) 0.15; pores 0.003 to 0.001, bars 0.005; main axis of the +inner cortical shell 0.26, its greatest breadth 0.13; pores of its distal +chambers 0.003, of its proximal chambers 0.01; large square pores 0.03; +bars 0.004. + +_Habitat._--Pacific, central area, Station 270, depth 2925 fathoms. + + + +{384}Subgenus 2. _Peripanartium_, Haeckel. + +_Definition._--Surface of the outer cortical shell covered with spines or +thorns. + + +4. _Peripanartus atractus_, n. sp. (Pl. 40, fig. 7). + +Inner cortical shell with four very unequal chambers; both proximal +chambers spheroidal (with subregular, roundish pores, twice to three times +as broad as the bars), both distal chambers nearly conical, with a circle +of eight to ten very large square pores at the base; the other pores very +small, roundish. Outer cortical shell envelops only the proximal chambers +and the basal half of the distal chambers, appearing as the direct +continuation of the microporous covering of their apical half. The whole +external cortical shell is inflated in the equatorial zone, and hence +assumes an irregular, spindle-like appearance. Its whole surface is rough +with innumerable very short thorns. + +_Dimensions._--Main axis 0.28, equatorial axis 0.17; pores of the external +cortical shell 0.002 to 0.004, bars 0.002; main axis of the proximal +chambers of the internal cortical shell 0.07, equatorial axis 0.09; pores +0.007, bars 0.004. + +_Habitat._--North Pacific, Station 244, depth 2900 fathoms. + + +5. _Peripanartus cylindrus_, n. sp. (Pl. 40, fig. 6). + +Internal cortical shell with four unequal chambers; both proximal chambers +kidney-shaped (with regular, circular, hexagonally framed pores of the same +breadth as the bars), both distal chambers nearly hemispherical, with a +circle of eight to ten very large square pores at their base; the other +pores very small, roundish. External cortical shell envelops the whole +internal like a perfect hollow cylinder, which is closed at both poles by a +hemispherical cap. The whole surface of this cylindrical mantle is +perforated by innumerable very small roundish pores, and covered with small +bristle-like spines. + +_Dimensions._--Main axis of the cylinder 0.3, equatorial axis 0.12; pores +and bars 0.006; spines of its surface 0.012 to 0.15; main axis of the +internal cortical shell 0.2; equatorial axis (in the constriction) 0.06; +pores and bars of its proximal chambers 0.007, of its distal chambers +0.003; large square pores at their base 0.02. + +_Habitat._--Pacific, central area, Stations 270 to 274, depth 2350 to 2925 +fathoms. + + + +Genus 165. _Panicium_,[204] n. gen. + +_Definition._--#Panartida# with simple cortical shell and double medullary +shell, with two opposite apical spines on both poles of the main axis, or +with a group of polar spines. + +The genus _Panicium_ comprises those forms of _Panartus_ which develop a +peculiar armature on both poles of the cortical shell. This may be only a +single strong spine {385}on each pole, lying in the main axis (subgenus +_Panicidium_); or a bunch or a circle of polar spines diverging radially +(subgenus _Panartidium_); in the latter case the polar spines can either +form a bunch on the pole itself, or a crown of thorns around it. + + + +Subgenus 1. _Panicidium_, Haeckel. + +_Definition._--On both poles of the main axis only a single large spine. + + +1. _Panicium amphacanthum_, n. sp. + +All four chambers of the cortical shell nearly of the same size and form, +kidney-shaped, with subregular, circular pores, twice as broad as the bars; +five to six pores on the half meridian, ten to eleven on the half equator +of each chamber. Surface covered with small spines. On both poles of the +main axis is a very strong, conical, apical spine, half as long as the main +axis, on the base one-fourth as broad as the equatorial axis. + +_Dimensions._--Main axis (without polar spines) 0.22, equatorial axis 0.06; +pores 0.01, bars 0.005; length of the polar spines 0.12, basal thickness +0.015. + +_Habitat._--Antarctic, Station 152, depth 1260 fathoms. + + +2. _Panicium amphistylus_, n. sp. + +Both proximal chambers kidney-shaped, both distal chambers nearly +hemispherical, somewhat smaller. Pores irregular, roundish, twice to three +times as broad as the bars; four to six on the half meridian, eight to ten +on the half equator of each chamber; a circle of larger square pores on the +base of each distal chamber. Surface thorny. On both poles of the main axis +one strong, pyramidal, apical spine, one-third as long as the main axis, on +the base one-fourth as broad as the equatorial constriction. (Similar to +_Panarium tubularium_, Pl. 40, fig. 9, but without tubes.) + +_Dimensions._--Main axis (without polar spines) 0.2, equatorial axis 0.05; +pores 0.005 to 0.01, bars 0.003; length of the polar spines 0.07, basal +thickness 0.012. + +_Habitat._--Antarctic, Station 156, depth 1975 fathoms. + + + +Subgenus 2. _Panartidium_, Haeckel. + +_Definition._--On both poles of the main axis a bunch or a circle of +aggregated spines. + + +3. _Panicium scoparium_, n. sp. + +Both proximal chambers kidney-shaped, both distal chambers nearly +hemispherical, somewhat smaller. Pores irregular, polygonal, twice to five +times as broad as the bars; six to eight on the half meridian, twelve to +fourteen on the half equator of each chamber. Surface spiny, covered with +thin, {386}bristle-like spines. On both poles of the main axis a bunch of +six to eight aggregated larger conical spines, about as high as a single +chamber. + +_Dimensions._--Main axis (without polar spines) 0.2, equatorial axis 0.06; +pores 0.005 to 0.015, bars 0.003; length of the polar spines 0.05, basal +thickness 0.005. + +_Habitat._--Pacific, central area, Stations 270 to 274, depth 2350 to 2925 +fathoms. + + +4. _Panicium coronatum_, n. sp. (Pl. 40, fig. 4). + +Both proximal chambers kidney-shaped, covered with short stout spines. +Pores irregular, roundish, twice to four times as broad as the bars; seven +to eight on the half meridian, eleven to thirteen on the half equator of +each chamber. Both distal chambers cap-like, separated from the former by a +circle of ten to twelve very large square pores; the other pores very +small, roundish. The circumpolar area is smooth, surrounded by a circle of +ten to twelve very stout, conical, radial spines, which arise from the +distal ends of the bars separating the large square meshes. + +_Dimensions._--Main axis (without spines) 0.22, equatorial axis 0.08; +greatest breadth in the equator of the chambers 0.1; pores of the proximal +chambers 0.007 to 0.015, bars 0.004; square pores of the distal chambers +0.02 to 0.03, small pores 0.005, bars 0.004; length of the radial spines of +the polar circles 0.07, basal thickness 0.007. + +_Habitat._--Pacific, central area, Station 271, depth 2425 fathoms. + + + +Genus 166. _Peripanicium_,[205] n. gen. + +_Definition._--#Panartida# with double cortical shell and double medullary +shell, on both poles of the main axis with two opposite apical spines, or +with a bunch or circle of polar spines. + +The genus _Peripanicium_ differs from _Panicium_ only in the development of +an outer reticulated envelope, which mantle-like surrounds the shell, and +represents a second or external cortical shell. As in _Panicium_, its +ancestral form, so also in _Peripanicium_, there can be distinguished two +subgenera:--_Peripanicea_, where only a single large spine arises from each +pole (lying in the main axis), and _Peripanicula_, where a variable number +of spines is to be found, either diverging bunch-like from the pole itself, +or surrounding it as a crown-like polar circle. + + + +Subgenus 1. _Peripanicea_, Haeckel. + +_Definition._--On both poles of the main axis only a single large spine. + + +1. _Peripanicium amphixiphus_, n. sp. + +Internal cortical shell with four unequal chambers, with thorny surface. +Both proximal chambers kidney-shaped (with subregular hexagonal pores, +three times as broad as the bars). {387}Both distal chambers nearly +hemispherical (with a circle of ten to twelve very large square pores at +their base, the other pores very small). From both poles arises a single, +strong, conical spine, half as long as the main axis. The internal cortical +shell is very much like that of _Panarium tubularium_ (Pl. 40, fig. 9), but +differs by the solid polar spines (instead of the hollow tubules) and by +the formation of an external, cylindrical, very thin, cortical shell, which +envelops the whole internal, and is connected with it by numerous beams. +The surface of the external shell is quite smooth, and perforated by +innumerable very small roundish pores. + +_Dimensions._--Main axis of the external cortical shell 0.25, of the +internal 0.19; transverse axis of the former 0.13, of the latter 0.08; +pores of the proximal chambers of the internal shell 0.01, bars 0.003; +pores of external cortical shell 0.002, bars 0.001; length of both polar +spines 0.12, basal thickness of them 0.02. + +_Habitat._--South Atlantic, near Tristan da Cunha, Station 333, depth 2025 +fathoms. + + + +Subgenus 2. _Peripanicula_, Haeckel. + +_Definition._--On both poles of the main axis a bunch or a circle of +aggregated polar spines. + + +2. _Peripanicium amphicorona_, n. sp. (Pl. 40, fig. 8). + + _Peripanartus amphicorona_, Haeckel, 1881, Prodromus et Atlas (pl. xl. + fig. 8). + +Internal cortical shell with four very unequal chambers. Both proximal +chambers kidney-shaped, with subregular, polygonal pores, three times as +broad as the bars. Both distal chambers double cone-shaped; the proximal +cone of these formed by a circle of ten to twelve radial beams, which +separate the same number of large square meshes; the distal cone with five +to six circles of very small roundish, irregular pores. The continuation of +the thin porous lamella of this distal cone forms the external cortical +shell, whose surface is a little rough with innumerable very small thorns. +On both poles is a large circular opening (nearly as broad as the +equatorial constriction of the inner shell), surrounded by a delicate crown +of thorns. The spines of this crown equal the diameter of the polar +opening; they are very thin and bristle-like, connected by a few bridges +and diverge outwards. + +_Dimensions._--Main axis (without the crowns of polar thorns) 0.26, +greatest breadth (in the equator of the proximal chambers) 0.15; equatorial +constriction of the external shell 0.12, of the internal 0.07; pores of the +proximal chambers of the internal cortical shell 0.01, of the external +0.005, bars 0.003; diameter of the circular polar opening 0.05; length of +the polar spines 0.05. + +_Habitat._--Pacific, central area, Station 271, depth 2425 fathoms. + + +3. _Peripanicium coronarium_, n. sp. + +Internal cortical shell with four unequal chambers. Both proximal chambers +kidney-shaped, with irregular, roundish pores, twice to four times as broad +as the bars. Both distal chambers cap-like, with a basal circle of ten to +twelve large square meshes, the other pores very small. External +{388}cortical shell very thin, with smooth surface, and very small, +irregular, roundish pores; it envelops the whole internal shell at a +constant distance, which equals the breadth of the square meshes. From the +distal ends of the radial beams between the square meshes arise on every +polar circle ten to twelve strong spines, as direct prolongations of those +beams. These form two regular, polar crowns of thorns. The inner part of +the thorns (between both shells) has only one-third to one-fourth the +length of the outer free part. (This species represents a further +development of _Panicium coronatum_, Pl. 40, fig. 4, by secondary formation +of an external mantle, like that of _Peripanartus atractus_, Pl. 40, fig. +7.) + +_Dimensions._--Main axis 0.27, greatest breadth 0.15; pores of the internal +proximal chambers 0.008 to 0.016, bars 0.004; square meshes of the distal +chambers 0.03; pores of the outer cortical shell 0.003; length of the +spines of the polar circles 0.1 to 0.15. + +_Habitat._--Pacific, central area, Station 274, depth 2750 fathoms. + + + +Genus 167. _Panarium_,[206] Haeckel, 1881, Prodromus, p. 463. + +_Definition._--#Panartida# with simple cortical shell and double medullary +shell, with two hollow fenestrated tubes, opposite on the poles of the main +axis. + +The genus _Panarium_ differs from _Panartus_ by two hollow latticed tubes, +which start from both poles of the main axis and lie in it. It repeats +therefore in this family the same peculiar and remarkable formation, which +we find in _Pipettella_ among the Ellipsida, in _Pipetta_ among the +Druppulida, in _Cannartidium_ among the Cyphinida, in _Cannartus_ among the +Artiscida, &c. + + + +Subgenus 1. _Panarelium_, Haeckel. + +_Definition._--Surface of the shell smooth, without spines or thorns. + + +1. _Panarium facettarium_, n. sp. + +Surface of the cortical shell smooth. All the four chambers nearly of the +same size and form, kidney-shaped, about twice as broad as long. Pores of +these subregular, circular, with hexagonal frames, about as broad as the +bars; nine to ten on the half meridian, twelve to fourteen on the half +equator of each chamber. Polar tubuli nearly cylindrical, longer than half +the main axis of the cortical shell, about one-fourth as broad as the +equatorial constriction. Pores of the tubuli of the same shape as those of +the chambers, but only half as large. (This species is like _Pipetta tuba_, +Pl. 39, fig. 7, but distinguished by three parallel transverse +constrictions.) + +_Dimensions._--Total length of the shell (without tubuli) 0.26; breadth of +each chamber 0.12; pores 0.01, bars 0.01; length of the tubuli 0.15, +breadth of them 0.03. + +_Habitat._--Pacific central area, Station 268, depth 2900 fathoms. + + +{389}2. _Panarium pipettarium_, n. sp. + +Surface of the cortical shell smooth. Both proximal chambers nearly +kidney-shaped; both distal chambers somewhat smaller, hemispherical. Pores +of all four chambers subregular, circular, without hexagonal frames, twice +as broad as the bars; six to seven pores on the half meridian, ten to +eleven on the half equator of each chamber. Polar tubuli slender, conical, +nearly half as long as the main axis of the shell, one-third as broad at +the base as the equatorial constriction. Pores of the tubuli of the same +shape as those of the chambers, but only half as large. (This species +resembles somewhat _Cannartiscus amphiconiscus_, Pl. 39, fig. 19, but with +double the number of chambers.) + +_Dimensions._--Total length of the shell (without tubuli) 0.25, greatest +breadth 0.1; pores 0.008, bars 0.004; length of the polar tubuli 0.11, +basal breadth 0.03. + +_Habitat._--Pacific, western tropical part, Station 225, depth 4475 +fathoms. + + + +Subgenus 2. _Panaromium_, Haeckel. + +_Definition._--Surface of the shell spiny, covered with short thorns. + + +3. _Panarium annularium_, n. sp. + +Surface of the cortical shell thorny, everywhere covered with small +bristle-like spines. All four chambers nearly of the same size and form, +kidney-shaped. Their pores subregular, circular, three to four times as +broad as the bars; seven to eight on the half meridian, ten to eleven on +the half equator of each chamber. Polar tubuli conical, nearly half as long +as the main axis, half as broad at the base as the equatorial constriction. +Pores of the tubuli like those of the chambers, but only half as broad. + +_Dimensions._--Total length of the shell (without tubuli) 0.16; breadth of +each chamber 0.07; pores 0.006 to 0.008, bars 0.002; length of the polar +tubuli 0.07, basal breadth 0.03. + +_Habitat._--Northern Pacific, Station 253, depth 3125 fathoms. + + +4. _Panarium artophorum_, n. sp. + +Surface of the shell thorny, with scattered small spines. Both proximal +chambers nearly kidney-shaped; both distal hemispherical, somewhat smaller. + Pores of all chambers irregular, roundish, little broader than the bars; +four to five on the half meridian, six to eight on the half equator of each +chamber. Polar tubuli cylindrical, longer than the half main axis, only +one-fourth as broad the equatorial constriction. Pores of the tubuli only +one-third to one-fourth as broad as those of the chambers. + +_Dimensions._--Total length of the shell (without tubuli) 0.22, greatest +breadth (in the equator of the proximal chambers) 0.09; pores and bars +0.008 to 0.012; length of the polar tubuli 0.14, breadth of them 0.02. + +_Habitat._--Southern Pacific, Station 289, depth 2550 fathoms. + + +{390}5. _Panarium tubularium_, n. sp. (Pl. 40, fig. 9). + +Surface of the cortical shell thorny, covered with small spines. Both +proximal chambers nearly kidney-shaped, with irregular, polygonal pores, +three to four times as broad as the bars; five to six pores on the half +meridian, nine to ten on the half equator of each chamber. Both distal +chambers nearly hemispherical, with a circle of ten to twelve large square +pores at their base; the other pores much smaller, irregular, roundish. +Polar tubuli prismatic, with prominent edges, nearly half as long as the +main axis, only one-fourth as broad as the equatorial constriction. Pores +of the tubuli very small, in longitudinal series between the edges. + +_Dimensions._--Total length of the shell (without tubuli) 0.18 to 0.2, +greatest breadth (in the equator of the proximal chambers) 0.07 to 0.09; +pores 0.003 to 0.01, bars 0.002 to 0.004; length of the polar tubuli 0.06 +to 0.09, breadth of them 0.015 to 0.02. + +_Habitat._--Pacific, central area, Stations 270 to 272, depth 2425 to 2925 +fathoms. + + + +Genus 168. _Peripanarium_,[207] n. gen. + +_Definition._--#Panartida# with double cortical shell and double medullary +shell, with two hollow fenestrated tubes, opposite on the poles of the main +axis. + +The genus _Peripanarium_ differs from _Panarium_ only in the development of +an outer reticulated envelop, which mantle-like surrounds the shell and +represents a second or external cortical shell. It bears therefore to +_Panarium_ the same relation as _Peripanartus_ to _Panartus_, &c. + + +1. _Peripanarium cenoconicum_, n. sp. + +Internal cortical shell with four kidney-shaped chambers of nearly the same +form and size; their pores irregular, roundish, twice to four times as +broad as the bars. External cortical shell cylindrical, hemispherical at +both poles, with irregular, very small, roundish pores, only one-third to +one-half as large as those of the internal. From both poles of the +internal cortical shell arises a hollow conical fenestrated tube, which +perforates the external. The outer free part of this slender cone equals +in length the inner part or the distance between the two cortical shells, +which is about equal to the length of one chamber. External surface covered +with small thorns. (This species has the same appearance as _Desmartus +larvalis_, Pl. 40, fig. 12, but has only four chambers instead of six.) + +_Dimensions._--Main axis (without cones) 0.23, greatest breadth 0.11; pores +of the inner cortical shell 0.004 to 0.009, of the outer 0.002 to 0.003; +bars of the former 0.002, of the latter 0.001; total length of the polar +cones 0.05, basal thickness of them 0.03. + +_Habitat._--West Tropical Pacific, Station 225, depth 4475 fathoms. + + +{391}2. _Peripanarium cenocylindricum_, n. sp. + +Internal cortical shell with four unequal chambers, the two proximal +kidney-shaped, the two distal conical, and somewhat smaller; pores +irregular, polygonal-roundish, twice to five times as broad as the bars. +External cortical shell nearly spindle-shaped, in the equatorial zone +inflated, conical, tapering towards both poles, its pores very small, +roundish, its surface covered with small thorns. The shell of this species +resembles very much _Peripanartus atractus_ (Pl. 40, fig. 7), but differs +by the hollow cylindrical polar tubes, which arise from both poles of the +inner cortical shell and attain more than half the length of the main axis. +They are open at their ends (broken away), about as broad as the outer +medullary shell, and perforated by irregular, roundish pores. + +_Dimensions._--Main axis (without polar tubes) 0.28, greatest breadth (in +the equator) 0.16; pores of the inner cortical shell 0.004 to 0.01, of the +outer 0.002 to 0.005; bars of the former 0.004, of the latter 0.002; total +length of the polar tubes 0.16, breadth of them 0.03. + +_Habitat._--Pacific, central area, Station 268, depth 2900 fathoms. + + + +Family XVII. #ZYGARTIDA#, Haeckel (Pl. 40, figs. 10-13). + +_Zygartida_, Haeckel, 1881, Prodromus, p.462 (_sensu restricto_). + +_Definition._--#Prunoidea# with annulated cortical shell, the external +shell being divided by five or more parallel transverse constrictions into +six or more chambers, enclosing in the centre two internal concentric +shells (medullary shells). Central capsule cylindrical, commonly annulated +(corresponding to the transverse annular constrictions of the cortical +shell). + +The family #Zygartida#, the seventh and last of the #Prunoidea#, comprises, +in the sense here restricted, all those #Prunoidea# in which the cortical +shell is annulated and composed of six to twenty or more (at least six) +camerae, lying one behind another in the elongated main axis, and separated +by five or more annular constrictions. When I constituted this family in +1881 (_loc. cit._), I had given to it a much wider extent, embracing all +those #Prunoidea# which exhibit annular constrictions of the cortical +shell; as the number of these, in consequence of further researches, is +much increased, it seems now more convenient to restrict the family to the +extent here given. + +No doubt the Zygartida must be derived from the Panartida by progressive +growth of the cortical shell in the main axis and accompanying increase of +the number of its chambers. Whilst this number in the Panartida is +constantly restricted to four, in the Zygartida it amounts to ten, twenty, +or more, and is in the lowest case six (Pl. 40, fig. 10). The maximum +number is variable in the different species, but of course also different +in the various degrees of individual development. Each Zygartid is at the +beginning of its growth a Cyphinid, later a Panartid. The number of the +annular constrictions separating the chambers and lying in parallel +transverse planes is at least {392}five, but may amount to nineteen, to +twenty-one or more; they lie constantly in pairs on both sides of the +equatorial constriction (Pl. 40, figs. 12, 13). + +The cortical shell may either remain simple (_Ommatocampe_, Pl. 40, fig. +10), or become double (_Desmocampe_, Pl. 40, fig. 12), or sometimes triple +(_Zygocampe_, Pl. 40, fig. 13). In the latter cases the outer (secondary +and tertiary) cortical shells are commonly incomplete, and only developed +around the proximal chambers of the complete first (primary) cortical +shell, its distal chambers remaining simple. + +_The Medullary Shell_ is constantly double, as in the Panartida; its form +is either spherical or lenticular, compressed in the direction of the main +axis. It is always connected with the equatorial constriction of the +cortical shell by a number of radial beams, lying either in the equatorial +plane or on each side of it (Pl. 40, figs. 10-13). + +_The Central Capsule_ of the Zygartida is constantly cylindrical; its +increasing growth on both poles of the axis corresponds to that of the +including cortical shell. Commonly (but not always) its cylindrical surface +is annulated, with five or more transverse strictures, corresponding to +those of the cortical shell. From the inner surface of the latter it is +separated by a jelly-mantle, the calymma. + +_Synopsis of the Genera of Zygartida._ + + I. Ommacampida. { Without polar tubes, 169. _Ommatocampe_. + 1. Cortical shell { + simple. { With two hollow fenestrated + (Medullary shell { tubes, on the poles of + double.) { the axis, 170. _Ommatartus_. + + II. Desmocampida. { Without polar tubes, 171. _Desmocampe_. + 2. Cortical shell { + double. { With two hollow fenestrated + (Medullary shell { tubes, on the poles of + double.) { the axis, 172. _Desmartus_. + + III. Zygocampida. { Without polar tubes, 173. _Zygocampe_. + 3. Cortical shell { + triple. { With two hollow fenestrated + (Medullary shell { tubes, on the poles of + double.) { the axis, 174. _Zygartus_. + + + +Genus 169. _Ommatocampe_,[208] Ehrenberg, 1860, Monatsber. d. k. preuss. +Akad. d. Wiss. Berlin, p. 832. + +_Definition._--#Zygartida# with simple cortical shell and double medullary +shell, without polar tubes. + +The genus _Ommatocampe_ was founded by Ehrenberg in 1860 for one of his +"_Haliommatina_," with the following diagnosis:--"Shell rod-like, long, +articulate, with nucleus, without spines, with four or more joints." The +species figured by him, _Ommatocampe {393}polyarthra_, exhibits five pairs +of chambers on both sides of the meridian plane of the cortical shell, the +centre of which includes a double medullary shell. It represents the most +simple form of all Zygartida, and may be derived phylogenetically from +_Cyphonium_ simply by multiplication of the chambers of the cortical shell, +growing on both poles of the main axis. + + + +Subgenus 1. _Ommatocampium_. + +_Definition._--Surface of the cortical shell smooth or rough, without +thorns or spines, also without polar spines. + + +1. _Ommatocampe polyarthra_, Ehrenberg. + + _Ommatocampe polyarthra_, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. + Berlin, p. 279, Taf. vi. fig. 9. + +Cortical shell with smooth surface, composed of six to ten chambers of the +same size and form. Every chamber kidney-shaped, about twice as broad as +long, with three transverse rows of circular, subregular pores, twice to +three times as broad as the bars. Both medullary shells spherical. + +_Dimensions._--Length of the six-chambered cortical shell 0.15; greatest +breadth of each chamber 0.04; pores 0.005 to 0.007, bars 0.002 to 0.003. + +_Habitat._--Californian Sea, depth 2600 fathoms, Ehrenberg; Pacific, +central area, Station 268, depth 2900 fathoms; fossil in the Tertiary rocks +of Barbados, Haeckel. + + +2. _Ommatocampe increscens_, Stoehr. + + _Ommatocampe increscens_, Stoehr, 1880, Palaeontogr., vol. xxvi. p. 90, + Taf. ii. fig. 2, _a_, _b_. + +Cortical shell with rough surface, composed of six to ten chambers of +nearly the same size and form; the breadth of the chambers a little +increasing towards both poles. Every chamber kidney-shaped, the proximal +chambers twice as broad as long, with four or five transverse rows of +pores; the distal chambers three to four times as broad as long, with two +or three transverse rows of pores. Form of the pores irregular, roundish, +bars between them in the distal part smaller, in the proximal part larger +than the pores. Both medullary shells compressed lenticular. + +_Dimensions._--Length of the six-chambered cortical shell 0.22; greatest +breadth of the chambers 0.09 to 0.1; pores and bars 0.003 to 0.006. + +_Habitat._--Fossil in the Tertiary rocks of Sicily, Grotte, Stoehr. + + +3. _Ommatocampe annulata_, n. sp. + +Cortical shell with smooth surface, composed of six to twelve chambers of +nearly the same size and form. Each chamber kidney-shaped, twice as broad +as long, with four to five transverse rows of {394}irregular, roundish +pores, once to five times as broad as the bars. On the base of each distal +chamber (beginning in the second or third pair) a circle of twelve to +sixteen larger square pores. Both medullary shells compressed lenticular. +(Resembles the inner cortical shell of _Desmartus larvalis_, Pl. 40, fig. +12, but is without the polar tubes and the outer envelope of this species.) + +_Dimensions._--Length of the six-chambered cortical shell 0.23; greatest +breadth of each chamber 0.07; pores 0.002 to 0.01, bars 0.002. + +_Habitat._--Cosmopolitan; Mediterranean, Atlantic, Pacific, in various +depths. + + + +Subgenus 2. _Ommatocampula_, Haeckel. + +_Definition._--Surface of the cortical shell thorny or spiny, but without +peculiar polar spines and without regular coronals of spines. + + +4. _Ommatocampe erucaeformis_, n. sp. + +Cortical shell with spiny surface, composed of six to twelve chambers of +nearly the same size and form, the distal chambers a little smaller. The +form and structure of the cortical shell is nearly the same as in the +foregoing species, only the pores are somewhat larger, and the whole +surface is covered with bristle-like radial spines, about half as long as +the breadth of one chamber. Both medullary shells compressed and +lenticular. + +_Dimensions._--Length of the six-chambered cortical shell 0.24; greatest +breadth of each chamber 0.08; pores 0.005 to 0.012, bars 0.002. + +_Habitat._--North Atlantic, Canary Islands, Station 353, depth 2965 +fathoms. + + +5. _Ommatocampe nereis_, n. sp. (Pl. 40, fig. 10). + +Cortical shell with spiny surface, composed of six (or more) chambers of +different size and structure. Both proximal chambers kidney-shaped, with +subregular, circular, hexagonally framed pores, twice as broad as the bars. +All following chambers cap-like, with much smaller, irregular, roundish +pores, at the base of every chamber a circle of ten to twelve large square +pores. Spines of the surface short, irregularly scattered. Both medullary +shells spherical. (All the observed specimens possessed only six chambers.) + +_Dimensions._--Length of the six-chambered cortical shell 0.25; greatest +breadth of each chamber 0.08; pores of both proximal chambers 0.01, bars +0.005; basal pores of the other chambers 0.02; pores of their distal caps +0.003 to 0.006, bars 0.003. + +_Habitat._--Pacific, central area, Stations 271 to 274, depth 2350 to 2750 +fathoms. + + + +Subgenus 3. _Ommatocorona_, Haeckel. + +_Definition._--Surface of the cortical shell spiny, on every chamber a +regular circle or coronal of radial spines. + + +{395}6. _Ommatocampe chaetopodum_, n. sp. + +Cortical shell with spiny surface, composed of six (or more) kidney-shaped +chambers of different size and form. Both proximal chambers kidney-shaped, +with subregular, circular, hexagonally framed pores, about as broad as the +bars. All the following chambers hemispherical, with irregular, roundish +pores; at the base of every chamber a circle of ten to twelve larger square +pores. The beams between these latter are prolonged into free radial +spines, twice as thick as the bars. Therefore every chamber is surrounded +by a circle of radial spines, like those of _Panicium coronatum_ (Pl. 40, +fig. 4). Both medullary shells lenticular. + +_Dimensions._--Length of the six-chambered cortical shell 0.3, greatest +breadth 0.08, pores and bars of both proximal chambers 0.01; pores of the +other chambers 0.002 to 0.008; square pores 0.02, bars 0.005; length of the +coronal spines 0.03, thickness 0.01. + +_Habitat._--Indian Ocean, Madagascar, Rabbe. + + + +Subgenus 4. _Ommatacantha_, Haeckel. + +_Definition._--Surface of the shell smooth or spiny, on the poles of the +main axis occur two strong opposite polar spines. + + +7. _Ommatocampe amphilonche_, n. sp. + +Cortical shell composed of six kidney-shaped chambers of nearly the same +size and structure; every chamber twice as broad as long, with four to five +transverse rows of irregular, roundish pores, once to four times as broad +as the bars. Both medullary shells lenticular. Surface of the cortical +shell covered with bristle-like spines. On both poles of the main axis one +larger, strong, conical spine, about half as long as this axis, and on the +base as broad as the inner medullary shell. (Resembles on the whole +_Desmartus larvalis_, Pl. 40, fig. 12, but without external mantle, and +with two solid polar spines instead of the polar tubes.) + +_Dimensions._--Length of the six-chambered cortical shell 0.24; greatest +breadth of each chamber 0.08; pores 0.002 to 0.08, bars 0.002; length of +the polar spines 0.12, basal thickness 0.02. + +_Habitat._--Pacific, central area, Station 266, depth 2750 fathoms. + + + +Genus 170. _Ommatartus_,[209] Haeckel, 1881, Prodromus, p. 463. + +_Definition._--#Zygartida# with simple cortical shell and double medullary +shell, with two hollow fenestrated tubes, opposite on both poles of the +main axis. + +The genus _Ommatartus_ differs from _Ommatocampe_ by the development of two +hollow fenestrated tubes on both poles of the main axis, and bears +therefore the same relation to it as _Cannartidium_ to _Cyphonium_. The +former two genera differ from the two latter by the augmentation of the +chambers of the cortical shell. + + +{396}1. _Ommatartus amphicanna_, n. sp. + +Cortical shell with spiny surface, composed of six chambers of equal size +and kidney-shaped; every chamber with four to five transverse rows of +irregular, roundish pores, twice to three times as broad as the bars. Both +medullary shells lenticular. Polar tubes conical, about as long as one +chamber, with smaller pores. Both medullary shells spheroidal, more or less +compressed. (Resembles _Desmartus larvalis_, Pl. 40, fig. 12, but is +without the external shell.) + +_Dimensions._--Length of the six-chambered cortical shell 0.24; greatest +breadth of each chamber 0.07; pores 0.008 to 0.012, bars 0.004; length of +the polar tubes 0.04 to 0.05, basal thickness 0.02. + +_Habitat._--Pacific, central area, Stations 270 to 274, depth 2350 to 2925 +fathoms. + + +2. _Ommatartus amphisiphon_, n. sp. + +Cortical shell with spiny surface, composed of six or eight chambers of +different size and form. Both proximal chambers kidney-shaped, each with +five to six transverse rows of irregular, polygonal pores, three to four +times as broad as the bars. The other (four to six) chambers somewhat +smaller, more hemispherical, with smaller, irregular pores, but on the base +of each a circle of ten to twelve larger square pores. Polar tubuli +prismatic, about half as long as the main axis, with prominent edges and +longitudinal rows of smaller pores between them. Both medullary shells +lenticular. (Resembles closely _Panarium tubularium_, Pl. 40, fig. 9, but +with six to eight chambers instead of four, and with longer tubuli.) + +_Dimensions._--Length of the six-chambered cortical shell 0.26; greatest +breadth of the proximal chambers 0.09, of the distal chambers 0.07; pores +of the former 0.01, of the latter 0.004; large square pores 0.013, bars +0.003; length of the polar tubes 0.1 to 0.12, thickness 0.02. + +_Habitat._--South Pacific, Station 297, depth 1775 fathoms. + + +3. _Ommatartus amphobolus_, n. sp. + +Cortical shell with spiny surface, composed of six chambers of different +size and form. Both proximal chambers kidney-shaped, with four to five +transverse rows of subregular, circular pores, twice as broad as the bars. +Both middle chambers cap-like, with a basal circle of ten to twelve larger +square pores, and small roundish pores on the cap. Both distal chambers +smaller, conical, with very small roundish pores. Polar tubuli conical, +nearly half as long as the main axis, also with very small pores. Both +medullary shells lenticular. + +_Dimensions._--Length of the six-chambered shell 0.28, greatest breadth +0.08; pores of the proximal chambers 0.01, bars 0.005; pores of the distal +chambers and the polar tubes 0.002 to 0.004, bars 0.002; length of the +polar tubes 0.13, basal thickness 0.03. + +_Habitat._--North Pacific, Station 253, depth 3125 fathoms. + + + +Genus 171. _Desmocampe_,[210] n. gen. + +_Definition._--#Zygartida# with double cortical shell and double medullary +shell, without polar tubes. + +{397}The genus _Desmocampe_ differs from _Ommatocampe_ in the duplication +of the jointed cortical shell; the radial spines, which start from the +surface of the inner cortical shell, are connected one with another by +transverse communicating branches which form an outer envelop around it; +but this reticulated mantle is commonly not quite perfect and more or less +irregular. + + +1. _Desmocampe catenula_, n. sp. + +Inner cortical shell with six to eight chambers of the same size and form. +Every chamber kidney-shaped, with three to four transverse rows of +circular, subregular pores, twice as broad as the bars. Outer cortical +shell cylindrical, hemispherical at both poles, with smooth surface and +irregular, roundish pores of very different size. Distance between the two +cortical shells equals the diameter of the outer medullary shell, which, +like the inner, is spherical. (Resembles Ommatocampe polyarthra, Ehrenberg, +1872, _loc. cit._, Taf. vi, fig. 9, but differs in the external mantle.) + +_Dimensions._--Length of the six-chambered inner cortical shell 0.16, of +the outer 0.21; greatest breadth of each chamber of the former 0.05, of the +latter 0.09; pores of the inner 0.006, bars 0.003; pores of the outer 0.002 +to 0.008, bars 0.002. + +_Habitat._--North Pacific, Station 237, off Japan, surface. + + +2. _Desmocampe taenioides_, n. sp. + +Inner cortical shell with six to ten chambers of nearly the same size and +form; the distal chambers somewhat smaller. Every chamber kidney-shaped, +with four to five transverse rows of irregular roundish pores, twice to +three times as broad as the bars. Outer cortical shell cylindrical, +hemispherical at both poles, with spiny surface; its pores like those of +the inner, but the bars between them much thinner. Distance between the two +cortical shells equals the diameter of the outer medullary shell. Both +medullary shells lenticular. (Resembles _Desmartus larvalis_, Pl. 40, fig. +12, but is without polar tubes.) + +_Dimensions._--Length of the six-chambered inner cortical shell 0.25, of +the outer 0.3; greatest breadth of the former 0.07, of the latter 0.11; +pores 0.005 to 0.012; bars of the inner shell 0.004, of the outer 0.001. + +_Habitat._--Pacific, central area, Station 268, depth 2900 fathoms. + + +3. _Desmocampe aphrodite_, n. sp. + +Inner cortical shell with six to ten chambers of different size and +structure. Both proximal chambers kidney-shaped, with five to six +transverse rows of subregular, circular, hexagonally-framed pores, twice as +broad as the bars. All following chambers cap-like, with much smaller, +irregular, roundish pores, on the base of each a circle of ten to twelve +large square pores. Outer cortical shell cylindrical, on both poles +hemispherical, with spiny surface and very delicate network of small +polygonal pores. Both medullary shells spherical. (The inner cortical shell +of this species resembles that of _Ommatocampe nereis_, Pl. 40, fig. 10; +the outer that of _Cyphocolpus virginis_, Pl. 40, fig. 11.) + +{398}_Dimensions._--Length of the six-chambered internal cortical shell +0.25, of the outer 0.3; greatest breadth of the former 0.08, of the latter +0.12; pores of the proximal chambers of the inner shell 0.01, bars 0.005; +pores of the distal chambers 0.003 to 0.005, square pores 0.02, bars 0.003; +pores of the external cortical shell 0.002 to 0.006, bars 0.001. + +_Habitat._--North Atlantic, Station 353, depth 2965 fathoms. + + +4. _Desmocampe atractus_, n. sp. + +Inner cortical shell with six chambers of very different size and +structure. Both proximal chambers kidney-shaped, with seven to eight +transverse rows of subregular, roundish pores, twice to three times as +broad as the bars. Both middle chambers cap-like, on the base with a circle +of eight to ten very large square pores, on the distal cap with small +irregular, roundish pores. Both distal chambers conical, also with small +irregular, roundish pores. Outer cortical shell spindle-shaped, inflated in +the equatorial zone, tapering conically towards both poles, with very +delicate network of small roundish pores and thin bars. Surface covered +with innumerable very small spines. Both medullary shells lenticular. +(Resembles very much _Peripanartus atractus_, Pl. 40, fig. 7, but differs +in the number of the chambers and their proportion to the outer mantle, +which envelops spindle-like all six chambers.) + +_Dimensions._--Length of the six-chambered internal cortical shell 0.27, of +the outer 0.32; greatest breadth of the former 0.09, of the latter 0.15; +pores of the inner cortical shell (on an average)--proximal chambers 0.008, +middle chambers 0.02, distal chambers 0.004, bars 0.004; pores of the outer +cortical shell 0.002 to 0.004, bars 0.002. + +_Habitat._--North Pacific, Station 241, depth 2300 fathoms. + + + +Genus 172. _Desmartus_,[211] n. gen. + +_Definition._--#Zygartida# with double cortical shell and double medullary +shell, with two hollow fenestrated tubes, opposite on both poles of the +main axis. + +The genus _Desmartus_ differs from _Desmocampe_ by the development of two +hollow fenestrated tubes, opposite on both poles of the main axis, and +bears therefore the same relation to it as _Ommatartus_ to _Ommatocampe_. +Both the former genera can be produced from the two latter by duplication +of the cortical shell. + + +1. _Desmartus larvalis_, n. sp. (Pl. 40, fig. 12). + + _Zygartus larvalis_, Haeckel, 1881, Prodromus et Atlas (pl. xl, fig. 12). + +Inner cortical shell composed of six kidney-shaped chambers of nearly the +same size and structure; every chamber twice as broad as long, with four to +five transverse rows of irregular, roundish pores, twice to five times as +broad as the bars; the basal pores of the distal chambers {399}somewhat +larger and more square. Outer cortical shell cylindrical, hemispherical at +both poles, with irregular, polygonal pores, on an average twice as large +as those of the inner, but the bars between them much thinner. Outer +surface spiny. Both medullary shells lenticular. Polar tubes conical, a +little longer than one internal chamber, as broad at the base as the inner +medullary shell. Sometimes the tubes exhibit prominent edges (as in the +lower spine of fig. 12); the pores of these are very small, and roundish. + +_Dimensions._--Length of the six-chambered internal cortical shell 0.23, of +the external 0.3; greatest breadth of the former 0.07, of the latter 0.11; +pores of the inner shell 0.004 to 0.01, of the outer 0.01 to 0.02; bars of +the former 0.002, of the latter 0.001; length of the polar tubes 0.05, +basal thickness 0.02. + +_Habitat._--North Pacific, Station 241, depth 2300 fathoms. + + +2. _Desmartus tubulatus_, n. sp. + +Inner cortical shell composed of six to ten kidney-shaped chambers, +tapering in size towards both poles, every chamber with six to seven +transverse rows of irregular, roundish pores, twice to six times broader +than the bars. Outer cortical shell spindle-shaped, in the equatorial zone +inflated, tapering towards both poles, its network similar to the inner, +only more delicate. Polar tubes conical, twice as long as an inner chamber, +as broad at the base as the outer medullary shell. Both medullary shells +lenticular. + +_Dimensions._--Length of the six-chambered internal cortical shell 0.25, of +the external 0.32; greatest breadth of the former 0.08, of the latter 0.12; +pores of the inner shell 0.002 to 0.012, of the outer 0.003 to 0.01; bars +of the former 0.002, of the latter 0.001; length of the polar tubes 0.07, +basal thickness 0.03. + +_Habitat._--North Pacific, Station 256, depth 2950 fathoms. + + + +Genus 173. _Zygocampe_,[212] n. gen. + +_Definition._--#Zygartida# with triple (or multiple) cortical shell and +double medullary shell, without polar tubes. + +The genus _Zygocampe_ differs from _Desmocampe_ and _Ommatocampe_ by the +multiplication of the cortical shell, which is composed of three or more +concentric envelopes. The three mentioned genera form therefore a +phylogenetic series, produced by the concentric increase on the outside of +the jointed cortical shell. Commonly the second cortical shell is not as +complete as the first (or innermost), and the third (or outermost) is yet +more incomplete. Rarely the number of the concentric cortical shells +surpasses three. + + +1. _Zygocampe pupula_, n. sp. + +Inner cortical shell with six to twelve chambers of nearly the same size +and form. Every chamber kidney-shaped, with four to five transverse rows of +circular, subregular pores, twice as {400}broad as the bars. Middle +cortical shell cylindrical, hemispherical at both poles, with subregular +circular pores somewhat smaller than those of the inner; the bars also +thinner. Outer cortical shell of the same form as the middle, but with very +delicate network, and quite irregular, roundish pores and very thin bars. +Surface quite smooth. Both medullary shells lenticular. (May be regarded in +a phylogenetic as well as an ontogenetic sense, as the further +developmental form of _Desmocampe catenula_ and _Ommatocampe polyarthra_.) + +_Dimensions._--Length of the six-chambered inner cortical shell 0.17, of +the middle 0.22, of the outer 0.27; greatest breadth of the first 0.05, of +the second 0.09, of the third 0.12; pores of the inner cortical shell +0.005, of the middle 0.004, of the outer 0.003 to 0.012; bars of the first +0.003, of the second 0.002, of the third 0.001. + +_Habitat._--Pacific, central area, Station 266, depth 2750 fathoms. + + +2. _Zygocampe corasium_, n. sp. + +Inner cortical shell with six to eight chambers of different size and form. +Both proximal chambers kidney-shaped, with five to six transverse rows of +subregular, circular, hexagonally framed pores, twice as broad as the bars. +All following chambers cap-like, the distal somewhat smaller; their pores +much smaller, irregular, roundish; only at the base of each chamber a +circle of ten to twelve large square pores. Middle cortical shell +cylindrical, in the equatorial zone a little constricted, hemispherical at +both poles, with irregular delicate network of roundish, polygonal meshes. +Outer cortical shell of the same form as the middle, but with a very +delicate and quite irregular network of polygonal meshes. Commonly this +outer mantle is incomplete, and sometimes interwoven in a spongy manner +with the middle (or also with the inner). Surface covered with many +irregular, thin, bristle-like spines. Both medullary shells lenticular. +(May be considered in a phylogenetic and ontogenetic sense as a further +developmental stage of _Desmocampe aphrodite_ and _Ommatocampe nereis_, Pl. +40, fig. 10.) + +_Dimensions._--Length of the six-chambered inner cortical shell 0.24, of +the middle 0.3, of the outer 0.36; greatest breadth of the first 0.08, of +the second 0.12, of the third 0.16, pores of the first (on an average) +0.005 to 0.02, of the second 0.003 to 0.015, of the third 0.01 to 0.05; +bars corresponding 0.005 or 0.003 or 0.001. + +_Habitat._--North Pacific, Station 253, depth 3125 fathoms. + + +3. _Zygocampe chrysalidium_, n. sp. (Pl. 40, fig. 13). + +Inner cortical shell with six to eighteen chambers of different size and +form. Both proximal chambers kidney-shaped, with six to seven transverse +rows of subregular, circular pores, three to four times as broad as the +bars. All following chambers with more irregular pores, with a circle of +ten to twelve larger square pores at the base. Middle cortical shell with +smaller, irregular, roundish pores. Outer cortical shell with larger +polygonal, quite irregular pores. Both outer shells appear commonly +incomplete or somewhat irregularly developed, and sometimes in a spongy +manner interwoven with one another. Surface covered with irregular, +bristle-like spines. Both medullary shells spherical. The breadth of the +chambers decreases gradually towards both poles, so that the whole shell +assumes a spindle form. Sometimes on both poles is developed a short +conical {401}polar tube (in fig. 13 only on the upper pole), and so this +species is transformed into _Zygartus chrysalis_. + +_Dimensions._--Length of the six-chambered inner cortical shell 0.25, of +the middle 0.3, of the outer 0.35; greatest breadth of the first 0.07, of +the second 0.11, of the third 0.14; pores (on an average) 0.01 (0.002 to +0.02), bars 0.002 to 0.005. + +_Habitat._--Pacific, central area, Stations 272 to 274, depth 2350 to 2750 +fathoms. + + + +Genus 174. _Zygartus_,[213] Haeckel, 1881, Prodromus, p. 463. + +_Definition._--#Zygartida# with triple (or multiple) cortical shell and +double medullary shell, with two hollow fenestrated tubes, opposite on both +poles of the main axis. + +The genus _Zygartus_ differs from Zygocampe by the development of two +hollow fenestrated tubes, on the two opposite poles of the main axis. It +exhibits therefore to the latter the same relation that _Desmartus_ does to +_Desmocampe_ and _Ommatartus_ to _Ommatocampe_; it differs from these by +the multiplication of the cortical shell, which is composed of at least +three concentric envelopes. + + +1. _Zygartus doliolum_, n. sp. + +Inner cortical shell composed of six (or more) kidney-shaped chambers, all +nearly of the same size and structure, every chamber with four to five +transverse rows of irregular, roundish pores, twice to four times as broad +as the bars; the basal pores scarcely larger than the apical pores. Middle +cortical shell nearly of the same structure as the inner, only the pores +larger and the bars thinner. Outer cortical shell cylindrical, +hemispherical at both poles, its network very delicate, with large +irregular, polygonal pores, and very thin bars between them; its surface +covered with thin bristle-like spines. Both medullary shells lenticular. +Polar tube cylindrical, with conical apex, and with very small pores; its +length equals the breadth of two internal chambers, its breadth that of the +inner medullary shell. (This species appears to be a further developed form +of _Ommatocampe annulata_ and _Desmartus larvalis_, Pl. 40, fig. 12.) + +_Dimensions._--Length of the six-chambered inner cortical shell 0.25, of +the middle 0.3, of the outer 0.35; greatest breadth of the first 0.07, of +the second 0.11, of the third 0.15; pores of the inner shell 0.005 to 0.01, +of the middle 0.003 to 0.007, of the outer 0.008 to 0.02; bars of the first +0.002, of the second and third 0.001; length of the polar tubes 0.15, basal +thickness 0.02. + +_Habitat._--Pacific, central area, Station 270, depth 2925 fathoms. + + +2. _Zygartus chrysalis_, n. sp. (Pl. 40, fig. 13). + +Inner cortical shell composed of six to twenty (commonly eight to twelve) +chambers of different size and form. Both proximal chambers nearly +hemispherical, with spiny surface and subregular, {402}circular pores, +three to four times as broad as the bars. All following chambers cap-like, +tapering towards both poles, with more irregular, roundish pores, with a +circle of ten to twelve larger square pores at the base. Middle cortical +shell with smaller roundish pores. Outer cortical shell with larger +polygonal, quite irregular pores. Both medullary shells lenticular. Polar +tubes conical or cylindrical with conical apex, of very variable length, +sometimes not longer than one internal chamber, at other times twice to +four times as long (in the figured specimen not fully developed, as also a +part of the shells). Differs from _Zygocampe chrysalis_ only by the +production of polar tubes. + +_Dimensions._--Length of the six-chambered inner cortical shell 0.25, of +the middle 0.3, of the outer 0.35; greatest breadth of the first 0.07, of +the second 0.11, of the third 0.14; other measures the same as in +_Zygocampe chrysalis_; length of the tubes 0.05 to 0.12 or more. + +_Habitat._--Pacific, central area, Stations 270 to 274, depth 2350 to 2925 +fathoms. + + +---- + + +Suborder V. DISCOIDEA, Haeckel (Pls. 31-38, 41-48). + + _Discida_ vel _Discoidea_, Haeckel, 1862, Monogr. d. Radiol., pp. 56, + 476. + _Discoida_, _Discoidea_, _Discida_, Haeckel, 1878, Protistenreich, p. + 103. + +_Definition._--SPUMELLARIA with discoidal or lenticular central capsule +(often with radial prolongations, rarely allomorphic); with discoidal or +lenticular fenestrated siliceous shell (often with radial spines or +fenestrated arms, rarely allomorphic). Growth reduced or diminished in the +direction of one dimensive axis. + +The section #Discoidea# comprises those SPUMELLARIA in which the +fenestrated shell is more or less discoidal or lenticular, flattened or +compressed in the direction of one axis. The geometric fundamental form of +the latticed shell, which in the #Sphaeroidea# is a sphere, here becomes a +flat disk, like a medal, or a biconvex lens, sometimes also a biconcave +lens. The #Discoidea# can be derived from the #Sphaeroidea# by shortening +of one axis. This shortened vertical axis is the main axis of the disk; +both its poles are constantly equal. Perpendicular to this axis is the +equatorial plane of the disk by which it becomes divided into equal halves. +In the simplest forms of #Discoidea# all axes of this horizontal equatorial +plane (all "equatorial axes" or "cross axes") are equal; in the most of the +genera and species these cross axes are different, so that rays of stronger +growth ("perradii") alternate with rays of weaker growth ("interradii"). +The number of these cross axes distinguishable is commonly two to four, +rarely more. In the direction of these are developed either radial marginal +spines or spongy arms. + +The order #Discoidea# was founded in my Monograph (1862, p. 476) as the +family "Discida" (Radiolaria with flat discoidal or biconvex lenticular +shell), comprising the {403}"_Calodictya_ and _Lithocyclidina_" of +Ehrenberg and a great part of his "_Haliommatina_." As three different +subfamilies of that family I separated the Coccodiscida (with five genera), +the Trematodiscida (with seven genera), and the Discospirida (with two +genera; Monogr. d. Radiol., p. 485). A fourth group of #Discoidea# was +constituted by the Spongodiscida (with eight genera, including the +_Spongocyclida_), which at that time I united with the Spongurida, because +of their spongy structure (_loc. cit._, p. 452). + +As the number of fossil #Discoidea# found in the Tertiary rocks of Barbados +and of the Mediterranean shores (Sicily and Greece) is comparatively very +large, we find even in the first system of Polycystina of Ehrenberg (1847), +not less than twelve genera distinguished, viz., six _Calodictya_, two +_Haliommatina_, and four _Lithocyclidina_ (Monatsber. d. k. preuss. Akad. +d. Wiss. Berlin, 1847, p. 53). The whole number of Radiolarian genera +distinguished in that first system was forty-four. The diagnoses of them +given by Ehrenberg were as usual very insufficient. The characters of the +three families given by him were the following:--_Calodictya_--"Testarum +intus spongiosarum et nucleo destitutarum orbes; _Haliommatina_--Testae +subglobosae nucleus radiatus; _Lithocyclidina_--Testarum disci in media +parte nucleati margine celluloso." In the latest work of Ehrenberg (1875, +p. 157) the same system was repeated, but some new genera added; and +thirty-eight different species, appertaining to the #Discoidea#, were +figured in the same work (Abhandl. d. k. Akad. d. Wiss. Berlin, 1875, Tafs. +xx.-xxx.). + +Richard Hertwig, 1879, in his excellent work, Der Organismus der +Radiolarien (pp. 57-68), gave a detailed description of the skeleton of +some #Discoidea#, and arrived at the conclusion that this whole family had +a spirally constructed skeleton, and should therefore be derived from the +Lithelida. But this conclusion is certainly erroneous, and in my opinion +the whole explanation of that spiral structure, and of its signification in +the development of #Discoidea#, is the weakest part of that otherwise very +important work. + +In my Prodromus (1881, p. 456) I gave a provisional system of the #Discida# +or #Discoidea# from the immense quantity of new material collected by the +Challenger, and could distinguish not less than eighty-four genera. This +number is from subsequent research only augmented by seven, so that in the +following pages ninety-one genera with five hundred and one species are +described. In the Prodromus I had disposed them in four different families, +which number is now increased to six. These six families can be again +disposed in two main groups or sections, the #Phacodiscaria# and the +#Cyclodiscaria#, each section with three families. + +The #Phacodiscaria# are characterised by the possession of a typical +"phacoid shell," and contain the three families Cenodiscida, Phacodiscida, +and Coccodiscida. On the other hand, the #Cyclodiscaria# are distinguished +by the absence of such a "phacoid shell," and contain the three families +Porodiscida, Pylodiscida, and Spongodiscida. Both sections exhibit an +analogous development. + +{404}The #Cenodiscida# (Pl. 48, figs. 1-3) open the series of the +#Discoidea# as their simplest forms; a discoidal or lenticular simple +lattice-shell encloses a central capsule of the same form, and is separated +from it by the calymma or jelly-veil. The common ancestral form of this +family is _Cenodiscus_, without radial marginal spines; it can be derived +from _Cenosphaera_ in the most simple way, by flattening in one axis. If on +the equatorial margin of the lens a peculiar solid girdle be developed, we +obtain _Zonodiscus_; in all other genera of the Cenodiscida radial spines +are developed on the margin. As the simple lenticular cortical shell of +_Cenodiscus_, in which the central capsule is enclosed, is most +characteristic not only of this family, but also of the two following +families, we call it the phacoid shell (that is, a lenticular extracapsular +or cortical lattice-shell). + +The #Phacodiscida# (Pls. 31-35), the second family, have the same +extracapsular "phacoid shell" as the Cenodiscida, but differ from these by +the possession of one or two intracapsular concentric medullary shells, +which are connected with the former by radial beams, perforating the +lenticular central capsule. The radial beams are commonly numerous, and +arranged in two opposite bunches around the shortened main axis. But often +also besides these occur other longer radial beams, situated in the +equatorial plane; the number of these is commonly four, and they form a +regular rectangular cross, lying opposite in pairs in two equatorial +diameters, perpendicular one to another. In the simplest genera of this +family (the _Sethodiscida_) the equatorial margin of the phacoid shell is +simple or surrounded by a solid smooth girdle; in all other genera are +developed on the margin solid radial spines lying in the equatorial plane, +either regularly disposed in a somewhat constant number (two to eight, +_Heliosestrida_), or irregularly disposed, in a larger and more variable +number (ten to twenty or more, _Heliodiscida_). + +The #Coccodiscida# (Pls. 36-38) form a third family of the #Discoidea#, +directly associated with the Phacodiscida; both have the same +characteristic extracapsular "phacoid shell," which is connected by radial +beams with a simple or double, intracapsular medullary shell. But whilst in +the foregoing family the equatorial margin of the phacoid shell is simple +or only armed with radial spines, in the Coccodiscida it is surrounded by +peculiar concentric chambered girdles, or rings, which resemble those of +the following family, the Porodiscida. Each of these "chambered girdles" is +composed of a circular ring in the equatorial plane, a variable number of +radial beams dividing it into incomplete chambers, and two porous +cover-plates or "sieve-plates," covering the upper and lower face of the +disk. These sieve-plates may be regarded as incomplete lenticular cortical +shells, which are only developed in the peripheral part of the disk, whilst +their central part is represented by the only complete cortical shell, the +"phacoid shell." The number of these concentric chamber-girdles amounts to +from one to ten or more. The margin of the disk is either simple +(Lithocyclida) or armed with radial spines (Stylocyclida), or provided with +two to five chambered radial arms (Astracturida); the structure of the arms +is the same as that of the girdles. + +{405}The #Porodiscida# (Pls. 41-47), the largest family of all #Discoidea#, +begins the series of #Cyclodiscaria#, or those #Discoidea# in which there +is no "phacoid shell," but a small simple central chamber surrounded by a +number of small latticed chambers of nearly the same size and form. In the +Porodiscida these chambers are arranged in complete circular concentric +rings or spiral convolutions; in the small family of Pylodiscida the +central chamber is surrounded by three radial arm-chambers separated by +three open spaces; in the third family of #Cyclodiscaria#, the +Spongodiscida, all the chambers are arranged more or less irregularly, and +the whole disk becomes spongy; also the surface of the disk is spongy, +whilst in both former families it is covered by two regular even porous +plates or "sieve-plates." Probably all #Cyclodiscaria# can be derived +phylogenetically from _Archidiscus_, a very small and simple lenticular +disk, which is composed of a small spherical latticed central chamber and +of a single concentric chambered ring or girdle; the margin of this ring is +connected with the central chamber by a variable number of radial beams. +This _Archidiscus_ can be derived either from _Saturnalis_ (Pl. 13, fig. +16.) by the development of lattice-work between the equatorial ring and +both polar faces of the concentric central chamber, or from _Sethodiscus_ +(Pl. 33, figs. 1-3) by flattening of the lenticular shell, so that the +enclosed inner medullary shell (the central chamber) meets the outer +phacoid shell at both poles. + +The Porodiscida are commonly flat or biconvex (rarely biconcave) disks, the +central chamber of which is surrounded not by a single, but by a variable +number (commonly three to six) of concentric chambered girdles or rings; +they arise from _Archidiscus_ by apposition of new concentric chambered +rings around the first ring, all lying in the equatorial plane. Afterwards +the disk often becomes thickened by apposition of concentric chamber-rings +on both flat sides also, so that two to four or more layers are stratified +one over the other. The circular concentric rings often become interrupted, +or spirally convoluted (wholly or partially); also the chambers sometimes +become irregularly crowded. But in all cases both surfaces of the disk +(upper and lower) continue to be porous plates or sieve-plates, at least in +the centre, but they never become spongy. + +The margin of the disk exhibits in the Porodiscida a great variety of +different forms, serving for distinction of subfamilies and of genera. In +the Trematodiscida the margin remains quite simple, as in the Archidiscida, +or is only surrounded by a hyaline equatorial girdle. In the Ommatodiscida +it is distinguished by one or two peculiar oscula, surrounded by a corona +of spines. The Stylodictyida are distinguished by a number of solid radial +spines, and the Euchitonida by a number of chambered, or spongy, radial +arms, arising from the margin of the disk and lying in the equatorial +plane. The variety of these radial marginal appendages is in the +Porodiscida much greater than in the Coccodiscida. + +The #Pylodiscida# (Pl. 48, figs. 12-20) represent a new, small, but very +remarkable family of #Discoidea#, all triradial, and distinguished by the +peculiar formation of {406}large open spaces in the latticed discoidal +shell, which reappear in a similar shape among the #Larcoidea# in the +Pylonida (_Tetrapyle_, &c.). We get the best understanding of this peculiar +formation if we return to _Archidiscus_, probably the common ancestral form +of all #Cyclodiscaria#, of the Porodiscida as well as of the Pylodiscida +and Spongodiscida. In some species of _Archidiscus_ (_Archidiscus +hexoniscus_, _Archidiscus pyloniscus_, &c.) the small lenticular shell is +composed of a spherical latticed central chamber and of a concentric +equatorial girdle composed of six such chambers, either all six equal, or +alternately larger and smaller. This latter form is nearly identical with +_Triodiscus_, and if we imagine the lattice-work of only three +ring-chambers complete, whilst that of the three alternating chambers is +reduced to the marginal ring, we get _Triopyle_, by loss of this ring +_Triolene_ (a disk composed of four simple lattice-chambers, lying in one +plane, three radial around one central spherule). The genera mentioned form +together the subfamily of Triopylida. In the second subfamily, Hexapylida, +the same formation is doubled; here three double arm-chambers are separated +by three double spaces (two in each radius). Also here the three distal +spaces may be either quite open (_Pylolena_), or half closed by the +marginal girdle (_Hexapyle_), or quite loosely latticed (_Pylodiscus_). If +the margin of this latter form become surrounded by a perfect chambered +equatorial girdle, we get _Discozonium_, and if this acquire a peculiar +marginal ostium (surrounded by a corona of spines) we arrive at +_Discopyle_. These two latter genera form the third subfamily, the +Discopylida. The eight genera of Pylodiscida represent therefore a +continuous phylogenetic series. + +The #Spongodiscida# are the sixth and last family of the #Discoidea#, +differing from the five other families in the irregular, spongy structure +of the discoidal skeleton; both surfaces of the flat disk (upper and lower) +are here principally covered with a rough, spongy framework, whilst in the +five other families they are covered by the flat and smooth porous plates +or sieve-plates. Nevertheless there is no sharp boundary between the +Spongodiscida and the closely allied Porodiscida. In these latter also the +discoidal shell becomes often more or less spongy (mainly in the peripheral +part, _e.g._, in _Myelastrum_, Pl. 47); but at least the central part of +the disk here remains constantly covered by sieve-plates. The massive +skeleton of the Spongodiscida is either of perfectly irregular structure, +only composed of innumerable fine branched siliceous threads, interwoven in +all possible directions; or only the outer part of the disk is composed of +such spongy framework, whilst the central part is more or less distinctly +composed of concentric chambered rings, as in the Porodiscida. These latter +forms indeed exhibit an immediate transition to this family, and were +formerly (in 1862) separated by me as Spongocyclida. Also the polymorphous +shape of the disk margin in the Spongodiscida is quite analogous to that of +the Porodiscida. Whilst in the first subfamily, the Spongophacida, the +margin is quite simple; in the second, the Spongotrochida, it is armed with +solid radial spines; and in the third, the Spongobrachida, it is provided +with two, three, {407}or four spongy, radial arms--the former as well as +the latter lying in the equatorial plane of the disk, either regularly or +irregularly disposed. + +_The Equatorial Margin_ of the lenticular disk exhibits in all six families +of #Discoidea# similar characters, mainly serving for the distinction of +subfamilies and genera. In the most primitive genera of all six families +the margin is simple, without radial prolongations (spines or arms); it is +quite simple in _Cenodiscus_, _Sethodiscus_, _Phacodiscus_, _Lithocyclia_, +_Coccodiscus_, _Archidiscus_, _Porodiscus_, _Pylodiscus_, and +_Spongodiscus_. In some genera the simple margin of the lenticular disk is +bordered and surrounded by a thin, hyaline, equatorial girdle of silex, +either quite solid or slightly porous (_Zonodiscus_, _Periphaena_, +_Perizona_, _Perichlamydium_, and _Spongophacus_). + +A quite peculiar and remarkable character of few genera is the development +of one or two oscula, larger marginal openings, which are surrounded by a +corona of spines, and probable are fit for the issue a peculiar bunch of +pseudopodia or of a "sarcode flagellum." Such oscula occur only in two +families of #Cyclodiscaria#; in the Porodiscida and Pylodiscida; in the +former _Ommatodiscus_, in the latter _Discopyle_ (Pl. 48, figs. 19, 20) is +distinguished by a single marginal osculum; besides this, in the former +occurs _Stomatodiscus_, with two such oscula, opposite on the poles of one +axis (Pl. 48, fig. 8). These oscula may be compared with the similar polar +formations in some Ellipsida (_Lithomespilus_) and in many Cyrtoidea; but +they do not prove a nearer affinity with the latter, and are only +analogous, not homologous. + +_Radial Spines_ occur on the margin in the equatorial plane of the +#Discoidea# in the greatest variety of number, form, size, and disposition. +If the number be low (between two and eight) they are commonly regularly +disposed; if the number be larger (ten to twenty or more) their disposition +becomes commonly more or less irregular. The regular disposition is of +great promorphological importance, as indicating the axes in which the +growth is preponderant, and introduces other peculiar radial formations. +Regarding these axes we can generally distinguish two groups, _Artiacantha_ +with a paired number (two, four, eight), and _Perissacantha_ with odd +numbers (usually three). The section of _Artiacantha_ could be divided into +three following groups:--A. Stylodiscida, with two radial spines only, +lying opposite on both poles of one equatorial axis (the "first cross +axis")--_Stylodiscus_, _Sethostylus_, _Stylocyclia_, _Xiphodictya_, +_Spongolonche_ (Pl. 31, figs. 9-12; Pl. 38, fig. 1; Pl. 42, figs. 10-12, +&c.); B. Staurodiscida, with four radial spines, lying opposite in pairs on +the poles of two crossed equatorial axes, perpendicular to one another +(first and second cross axes)--_Crucidiscus_, _Sethostaurus_, +_Staurocyclia_, _Staurodictya_, _Spongostaurus_ (Pl. 31, figs. 1-8; Pl. 37, +figs. 1-4; Pl. 42, figs. 1-6; Pl. 48, fig. 2, &c.); C. Octostylida, with +eight radial spines, opposite in pairs in four axes, which are crossed at +angles of 45d--_Heliosestrum_, _Astrosestrum_, &c. (Pl. 32, figs. 4, 5; Pl. +34, figs. 3, 6); in this latter case sometimes the radial symmetry is the +same as in many Medusae, four larger (perradial) {408}spines alternating +with four smaller (interradial), indicating radii of first and second +order. The section of _Perissacantha_ is much smaller, and commonly +represented only by triradial forms, with three spines at equal distances +(120d)--_Triactis_, _Tripocyclia_, _Tripodictya_, _Spongotripus_, &c. (Pl. +33, fig. 6; Pl. 37, fig. 5; Pl. 42, figs. 7-9). + +_Radial Arms_ on the margin of the disk appear in similar variety of +number, form, and disposition as the radial spines; but the number is here +commonly limited to from two to four, rarely five to six. The arms are +absent in the families Cenodiscida and Phacodiscida; in the four other +families they return under similar forms. These arms are direct +prolongations of the disk, and exhibit the same structure, so that they may +be regarded both as centrifugal productions of certain radii, and also +inversely as peripheral parts of a disk, the interjacent radii of which are +reduced. The regular disposition and shape of the arms, an important +character for the distinction of genera and species, is repeated in a quite +analogous manner in the four above mentioned families, so that we can +distinguish the following groups--A. Amphibrachida, with two radial arms, +opposite on the poles of one equatorial axis (the first cross +axis)--_Diplactura_, _Amphibrachium_, _Spongobrachium_ (Pl. 38, figs. 3-5; +Pl. 44, figs. 6-11); B. Triobrachida, with three radial arms; the most +important group (with all Pylodiscida); either all three arms are equal and +disposed at equal distances (_Trigonactura_, _Dictyastrum_, +_Rhopalodictyum_, Pl. 38, figs. 6-9; Pl. 43, figs. 5, 13, 16; Pl. 48, figs. +12-19), or a single odd arm differs in size and position, and is often +larger than both the opposite paired arms (_Rhopalastrum_, _Euchitonia_, +Pl. 43, figs. 6, 10, 15, &c.); C. Tetrabrachida, with four radial arms, +opposite in pairs in two crossed axes, commonly perpendicular one to +another, _Stauractura_, _Stauralastrum_, _Spongaster_, &c. (Pls. 46, 47). + +The arms are commonly simple, undivided, but sometimes also forked or +branched (Pl. 43, figs. 15, 16; Pl. 47). Their basal parts are either free, +separately inserted into the margin of the circular central disk, or they +are connected by a "patagium," a peculiar connecticulum, like a +web-membrane, which is composed of a chambered, commonly more or less +spongy framework, different in texture from the lattice-work of the arms +(Pl. 38, figs. 8, 9; Pl. 43, figs. 9-16; Pl. 46). Sometimes the patagium +overgrows the whole shell. A peculiar modification of it appears in +_Stephanastrum_ (Pl. 44, fig. 1), where only the distal parts of the arms +are connected by the ring-shaped patagium, whilst the basal parts are free; +therefore open gates rest between them, like those of the Pylodiscida (Pl. +48, figs. 12-20). + +The _Central Capsule_ of the #Discoidea# is constantly discoidal, more or +less lenticular; in some cases more biconvex, with vaulted faces and thin +margin; in others more medal-shaped, with flat faces and thick margin. In +the Cenodiscida alone the capsule lies freely inside the simple phacoid +shell, and is separated from it by the jelly-veil. In the other five +families the capsule encloses the central parts of the skeleton, and is +enveloped by the superficial parts of it, whilst its membrane is perforated +by radial beams {409}connecting the latter with the former. In the +Phacodiscida and Coccodiscida the capsule encloses the simple or double +medullary shell, but is itself enclosed by the cortical phacoid shell. In +all #Cyclodiscaria# (in the Porodiscida, Pylodiscida, and Spongodiscida) +the capsule fills out the greatest part of the chambered or spongy +skeleton, and is only protected by the superficial parts of it, in the +Porodiscida and Pylodiscida by the covering sieve-plates, in the +Spongodiscida by the spongy cortical substance of the shell. The growth of +the capsule corresponds to that of the including shell, gradually +increasing on the margin in the equatorial plane. Whilst in the greater +number of #Discoidea# its form continues circular, in many forms provided +with radial arms it enters into the arms and assumes their form. The +protoplasm of the capsule is commonly coloured by brown or red pigment, and +often contains many oil-globules. The nucleus is originally enclosed by the +medullary shell or the central chamber, and with increasing size enters +into the surrounding parts; in the #Cyclodiscaria# it often fills out the +internal concentric rings. The extracapsular jelly or the calymma is +commonly thick, and envelops the greater part or the whole body. + +_Synopsis of the Families of the_ #Discoidea#. + + ------------------------------------------------------------------------- + I. Section #Phacodiscaria#. + Discoidea with external phacoid shell (or lenticular latticed cortical + shell). + ------------------------------------------------------------------------- + Phacoid shell simple, without enclosed 1. CENODISCIDA. + medullary shell + + Phacoid shell with { Margin without + simple or { chambered girdles, 2. PHACODISCIDA. + double { + enclosed { Margin surrounded by + medullary shell. { by chambered + { girdles. 3. COCCODISCIDA. + ------------------------------------------------------------------------- + II. Section #Cyclodiscaria#. + Discoidea without external phacoid shell (no lenticular latticed + cortical shell). + ------------------------------------------------------------------------- + Surface of the { Concentric rings around + shell covered { the central chamber + by convex or { complete (without + even porous { open spaces), 4. PORODISCIDA. + sieve-plates { + (not spongy). { Concentric rings around + { the central chamber + { interrupted by three + { open spaces, 5. PYLODISCIDA. + + Surface of the shell spongy, not covered + by peculiar porous sieve-plates, 6. SPONGODISCIDA. + + + +Family XVIII. #CENODISCIDA#, n. fam. (Pl. 31, fig. 11; Pl. 48, figs. 1-3). + +_Definition._--#Discoidea# with simple extracapsular phacoid shell (or +lenticular latticed cortical shell), without medullary shell and without +chambered equatorial girdles. + +The new family #Cenodiscida# opens the long series #Discoidea#, as their +most simple and primitive form. The circular lenticular central capsule is +enclosed by a {410}simple latticed shell of the same form, only separated +from it by a thinner or thicker jelly-veil. The lenticular or discoidal +fenestrated shell is therefore an extracapsular or "cortical shell," +without an enclosed medullary shell. + +The few genera of the Cenodiscida differ only in the shape of the +equatorial margin of the lenticular disk. In the first subfamily, +Zonodiscida, the margin is either quite simple (_Cenodiscus_) or surrounded +by a smooth, solid equatorial girdle (_Zonodiscus_). In the second +subfamily, Trochodiscida, the margin is armed with solid radial spines, +lying in the equatorial plane. According to the number and disposition of +these marginal spines, we distinguish _Stylodiscus_ (with two spines, +opposite in one equatorial axis), _Crucidiscus_ (with four spines, opposite +in pairs in two equatorial axes, perpendicular one to another), +_Theodiscus_ (with three marginal spines), and _Trochodiscus_ (with +numerous, commonly twenty to thirty, irregularly disposed spines). The +spines are constantly simple, not branched; sometimes more conical or +cylindrical, at other times more angular or pyramidal. + +The two convex faces of the lenticular shell are constantly of similar +shape, commonly smooth, sometimes more or less thorny, or armed with +bristle-shaped radial spines. The pores are commonly more or less regular, +circular, and disposed in series, which are occasionally more radial, at +other times more concentric. If the wall of the hollow lens be rather +thick, the difference in the shape of the central and peripheral pores is +often striking. The central pores perforating the thick wall +perpendicularly are short cylindrical tubes; the marginal pores perforating +it in an oblique direction are longer conical tubes. The bars between the +central pores are often somewhat smaller. + +_The Central Capsule_ of the Cenodiscida is in all cases a perfect, +circular, biconvex lens, the equatorial diameter of which is commonly +between two-thirds and three-fourths of the enclosing lattice-shell. The +interval between the two is filled up by the jelly-veil, or the hyaline +"calymma," which is perforated by the numerous pseudopodia that pass +through the shell-pores. + +As the Cenodiscida possess the most simple shell-form of all #Discoidea#, +we may regard _Cenodiscus_ as the common ancestral form of this large +section, in the same manner as _Cenosphaera_ is the ancestral form of +#Sphaeroidea#, _Cenellipsis_ of the Prunoidea, Cenolarcus of the Larcoidea. +But it is also possible that a part of Cenodiscida (or all?) arises from +the Phacodiscida by reduction and loss of the medullary shell. For in some +cases we find arising from the inside of the shell centripetal radial +beams, which end at a certain equal distance from the hollow centre (Pl. +31, fig. 11; Pl. 38, fig. 2). Cenodiscus itself can be derived either from +_Cenosphaera_ by compression of the spheroidal shell in one axis, or from +_Sethodiscus_ by loss of the intracapsular medullary shell, or from +_Actidiscus_ (the lenticular Actissa) by formation of a cortical shell +around the lenticular central capsule. + +{411}_Synopsis of the Genera of the Cenodiscida._ + + I. Subfamily {Margin quite simple, + Zonodiscida. { without equatorial girdle, 175. _Cenodiscus_. + Margin of the disk { + without radial {Margin surrounded by a solid + spines. { siliceous equatorial girdle, 176. _Zonodiscus_. + + II. Subfamily {Two spines opposite in one + Trochodiscida. { equatorial axis, 177. _Stylodiscus_. + Margin of the disk { + armed with radial {Three spines on the margin of + spines (lying in { the disk, 178. _Theodiscus_. + the equatorial { + plane). {Four spines opposite in pairs + { in two perpendicularly + { crossed equatorial axes, 179. _Crucidiscus_. + { + {Ten to twenty or more radial + { spines (variable in number + { and commonly irregular + { in disposition), 180. _Trochodiscus_. + + + +Subfamily 1. ZONODISCIDA, Haeckel. + +_Definition._--#Cenodiscida# without radial spines on the margin of the +disk. + + + +Genus 175. _Cenodiscus_,[214] n. gen. + +_Definition._--#Cenodiscida# with simple margin of the circular disk, +without surrounding equatorial girdle and without radial spines. + +The genus _Cenodiscus_ is the most simple and primitive form of all +#Discoidea#, and represents possibly the common ancestral form of this +order. The latticed shell is a simple biconvex lens, and encloses a smaller +central capsule of the same form, separated from it by the jelly-veil. +_Cenodiscus_ can be derived phylogenetically either from _Cenosphaera_ by +lenticular flattening of a simple latticed sphere, or directly from +_Actissa_ by formation of a lenticular fenestrated shell around the +lentiform central capsule. Possibly also some forms of _Cenodiscus_ can be +derived from _Sethodiscus_ by reduction and loss of the medullary shell. + + +1. _Cenodiscus phacoides_, n. sp. (Pl. 48, figs. 1, 1_a_). + +Disk with smooth surface, without radial ribs or spines. Margin of the +lenticular biconvex disk thin, simple. Pores regular, circular; fifteen to +sixteen on the radius of the disk. (Very similar to _Sethodiscus +phacoides_, but without medullary shell.) + +_Dimensions._--Diameter of the disk 0.2, of the pores 0.005. + +_Habitat._--Pacific, central area, Station 271, depth 2425 fathoms. + + +{412}2. _Cenodiscus rotula_, n. sp. + +Disk with smooth surface, without medial ribs or spines. Margin of the disk +blunt, very thick, rounded; both faces little convex. Pores regular, +circular; thirteen to fourteen on the radius of the disk. (Similar to +_Phacodiscus rotula_, Pl. 35, fig. 7, but without medullary shell.) + +_Dimensions._--Diameter of the disk 0.16, of the pores 0.006. + +_Habitat._--North Pacific, Station 241, depth 2300 fathoms. + + +3. _Cenodiscus lenticula_, n. sp. + +Disk with thorny surface, scattered with small, conical spines. Margin of +the lenticular biconvex disk thin. Pores irregular, roundish; ten to eleven +on the radius of the disk. + +_Dimensions._--Diameter of the disk 0.15, of the pores 0.008. + +_Habitat._--South Pacific, Station 295, depth 1500 fathoms. + + + +Genus 176. _Zonodiscus_,[215] n. gen. + +_Definition._--#Cenodiscida# with surrounding solid equatorial girdle on +the margin of the lenticular disk, without radial spines. + +The genus _Zonodiscus_ differs from the preceding _Cenodiscus_ only in the +development of a solid siliceous girdle around the keen margin of the +lenticular disk. This form can also be derived from _Periphaena_ or +_Perizona_ by reduction and loss of the medullary shell. The same girdle +formation returns not only in both these Phacodiscida (Pl. 32, fig. 7; Pl. +33, fig. 4), but also in the Porodiscid _Perichlamydium_. + + +1. _Zonodiscus saturnalis_, n. sp. + +Disk with smooth surface, without radial spines. Pores regular, circular, +fifteen to sixteen on the radius of the disk, in its distal half arranged +in fifty to sixty radial series, which are separated by prominent radial +crests or ribs. The crests are prolonged into the proximal half of the thin +solid equatorial girdle, which is one-third as broad as the radius of the +disk. + +_Dimensions._--Diameter of the disk 0.25, of the pores 0.05. + +_Habitat._--South Atlantic, Station 335, depth 1425 fathoms. + + + +Subfamily 2. TROCHODISCIDA, Haeckel. + +_Definition._--#Cenodiscida# with radial spines on the margin of the disk, +disposed in the equatorial plane. + + + +Genus 177. _Stylodiscus_,[216] n. gen. + +_Definition._--#Cenodiscida# with two radial spines on the margin of the +disk, opposite in one equatorial axis. + +{413}The genus _Stylodiscus_ opens the series of the Trochodiscida or of +those Cenodiscida in which the thin margin of the hollow lenticular disk is +armed with a number of solid radial spines, situated in its equatorial +plane. _Stylodiscus_ is at the same time the most simple form of the +Stylodiscida, or of the numerous #Discoidea# (belonging to different +families) in which the disk bears only two spines, opposite in one +equatorial axis. Hitherto only two species of this genus have been +observed, but they seem to represent two different subgenera. + + + +Subgenus 1. _Stylentodiscus_, Haeckel. + +_Definition._--Internal cavity of the shell with centripetal axial rods. + + +1. _Stylodiscus endostylus_, n. sp. (Pl. 31, fig. 11). + + _Sethostylus endostylus_, Haeckel, 1881, Prodromus et Atlas (pl. xxxi, + fig. 11). + +Disk with smooth surface and dentated margin. Pores irregular, roundish; +ten to twelve on the radius of the disk. Marginal teeth conical, short, +irregular. Both opposite polar spines cylindrical, longer than the diameter +of the disk, and as broad as one larger pore. On the inside of the hollow +disk both spines are prolonged into two strong centripetal axial rods, +which do not reach the centre. Also a number of smaller centripetal axial +rods surrounds the central cavity, so that an original medullary shell +(_Sethostylus_) seems to have been lost (comp. above, p. 410). + +_Dimensions._--Diameter of the disk 0.25, of the pores 0.005 to 0.02; +length of the polar spines 0.3 and more, thickness 0.012. + +_Habitat._--Pacific, central area, Station 265, depth 2900 fathoms. + + + +Subgenus 2. _Stylexodiscus_, Haeckel. + +_Definition._--Internal cavity of the shell without axial rods. + + +2. _Stylodiscus amphistylus_, n. sp. + +Disk with smooth surface and smooth margin. Pores regular, circular; eight +to nine on the radius of the disk. Both opposite polar spines pyramidal, +sulcated, about as long as the radius of the disk, and three times as long +as broad at the base. Inner cavity of the disk simple, without centripetal +rods. + +_Dimensions._--Diameter of the disk 0.15, of the pores 0.007; length of the +polar spines 0.08, basal breadth 0.03. + +_Habitat._--Pacific, central area, Station 274, depth 2750 fathoms. + + + +{414}Genus 178. _Theodiscus_,[217] n. gen. + +_Definition._--#Cenodiscida# with three radial spines on the margin of the +disk, placed in its equatorial plane. + +The genus _Theodiscus_ is the most simple form of those very numerous +#Discoidea# in which three rays are developed on the margin of the disk; a +symbol of the Christian dogma of the Trinity. Commonly the three angles +between the three spines are equal, more rarely one angle is larger than +the two others which are equal. The shell of some species is nearly +spherical (formerly separated by me as _Theosphaera_), whilst in others it +is a flattened biconvex lens. + + + +Subgenus 1. _Theodiscoma_, Haeckel. + +_Definition._--Angles between the three radial spines equal (triangle +equilateral). + + +1. _Theodiscus divinus_, n. sp. + +Disk nearly spherical, with smooth surface. Pores regular, circular, +hexagonally framed; seven to eight on the radius. Three angles between the +spines equal. Spines prismatic, straight, twice as broad as one pore, eight +to eleven times as long as the shell diameter. + +_Dimensions._--Diameter of the disk 0.1, of the pores 0.006; length of the +spines 0.8 to 1.1, breadth 0.01. + +_Habitat._--Central Pacific, Station 265, surface. + + +2. _Theodiscus christianus_, n. sp. + +Disk nearly spherical, with smooth surface. Pores regular, circular, +prolonged into short cylindrical, prominent tubuli, half as high as broad; +eight to nine on the radius. Three angles between the spines equal. Spines +prismatic, straight, twice as broad as one pore, twelve to fifteen times as +long as the shell diameter. + +_Dimensions._--Diameter of the disk 0.08, of the pores 0.005; length of the +spines 1.1 to 1.2, breadth 0.01. + +_Habitat._--Central Pacific, Station 271, surface. + + +3. _Theodiscus trinitatis_, n. sp. + +Disk a rather flattened, biconvex lens, about twice as broad as thick. +Pores regular, circular, not prolonged into tubuli; five to six on the +radius. Three angles between the spines equal. Spines pyramidal, three +times as broad as one pore, about twice as long as the shell diameter. + +{415}_Dimensions._--Diameter of the disk 0.06, of the pores 0.007; length +of the spine 0.12, basal breadth 0.02. + +_Habitat._--Central Pacific, Station 274, depth 2750 fathoms. + + + +Subgenus 2. _Theodiscura_, Haeckel. + +_Definition._--Angles between the three radial spines unequal, two paired +angles equal, larger or smaller than the odd angle (triangle isosceles). + + +4. _Theodiscus vanitatis_, n. sp. + +Disk nearly spherical, with smooth surface. Pores irregular, roundish; +eight to ten on the radius. Three angles between the spines unequal; one +odd angle larger than both others. Spines pyramidal, of unequal size; one +odd spine larger, both others smaller than the shell diameter. + +_Dimensions._--Diameter of the disk 0.12, pores 0.004 to 0.006; length of +the odd spine 0.2, of the paired spines 0.1. + +_Habitat._--South Atlantic, Station 335, depth 1425 fathoms. + + +5. _Theodiscus nirvana_, n. sp. + +Disk a flat biconvex lens, about twice as broad as thick. Pores regular, +circular; ten to twelve on the radius. Three angles between the spines +unequal; one odd angle smaller than both others. Spines prismatic, very +long and thin, twice as broad as one pore, ten to twelve times as long as +the shell diameter. + +_Dimensions._--Diameter of the disk 0.1, pores 0.005; length of the spines +1 to 1.2 or more, breadth 0.01. + +_Habitat._--Indian Ocean, Ceylon, surface, Haeckel. + + + +Genus 179. _Crucidiscus_,[218] n. gen. + +_Definition._--#Cenodiscida# with four radial spines on the margin of the +disk, crossed in the equatorial plane. + +The genus _Crucidiscus_ is the most simple form of the Staurodiscida, or of +the numerous #Discoidea# (belonging to different families) in which the +margin of the disk bears four radial spines, lying in the equatorial plane, +and crossed at right angles. Whilst commonly the internal shell-cavity of +_Crucidiscus_ is quite simple, in one case it bears four centripetal axial +rods, as inner prolongations of the outer radial cross-spines, perhaps +indications of a lost medullary shell (comp. p. 410). + + + +{416}Subgenus 1. _Staurentodiscus_, Haeckel. + +_Definition._--Internal cavity of the shell with centripetal axial rods. + + +1. _Crucidiscus endostaurus_, n. sp. (Pl. 48, fig. 2). + +Disk with smooth surface and smooth simple margin. Pores regular, circular; +thirteen to fourteen on the radius of the disk. Four crossed spines +conical, strong, longer than the radius of the disk, on the inside +prolonged into four thinner centripetal axial rods, which do not reach the +centre. In the middle part of the disk also some other short axial rods +arise from the inside, not reaching the centre (as in _Stylodiscus +endostylus_, Pl. 31, fig. 11). + +_Dimensions._--Diameter of the disk 0.16, of the pores 0.004; length of the +spines 0.2, breadth 0.014. + +_Habitat._--North Pacific, Station 253, depth 3125 fathoms. + + + +Subgenus 2. _Staurexodiscus_, Haeckel. + +_Definition._--Internal cavity of the shell without centripetal axial rods. + + +2. _Crucidiscus cuspidatus_, n. sp. + +Disk with smooth surface and simple smooth margin. Pores regular, circular; +seven to eight on the radius of the disk. Four crossed spines pyramidal, +with prominent edges, somewhat shorter than the radius of the disk, twice +as broad at their thick base as one pore. No internal axial rods in the +shell cavity. + +_Dimensions._--Diameter of the disk 0.12, of the pores 0.005; length of the +spines 0.05, basal breadth 0.025. + +_Habitat._--Pacific, central area, Station 268, depth 2900 fathoms. + + +3. _Crucidiscus echinatus_, n. sp. + +Disk with thorny surface and thorny margin. Pores regular, circular, six to +seven on the radius. Four crossed spines pyramidal (four sided?), about as +long as the radius of the disk, as broad at their base as one pore. No +internal axial rods. Spines of the surface short, conical. + +_Dimensions._--Diameter of the disk 0.14, of the pores 0.008; length of the +spines 0.08, basal breadth 0.02. + +_Habitat._--Pacific, central area, Station 271, depth 2425 fathoms. + + +4. _Crucidiscus cruciatus_, n. sp. + +Disk with smooth surface and broad dentated margin. Pores regular, +circular; eleven to twelve on the radius. Four crossed spines pyramidal, +sulcated, about as long as the radius of the disk, as {417}broad at their +base as the radiated margin, which bears fifty to sixty triangular pointed +teeth of irregular size. (Similar to _Sethostaurus cruciatus_, Pl. 31, fig. +5, but without internal axial rods and medullary shell.) + +_Dimensions._--Diameter of the disk 0.2, of the pores 0.007; length of the +spines 0.1, basal breadth 0.02. + +_Habitat._--Pacific, central area, Station 274, depth 2750 fathoms. + + + +Genus 180. _Trochodiscus_,[219] n. gen. + +_Definition._--#Cenodiscida# with numerous (ten to twenty or more) radial +spines on the margin of the disk, situated in its equatorial plane. + +The genus _Trochodiscus_ bears on the thin margin of the latticed disk a +variable number of radial spines (commonly ten to twenty, sometimes fifty +to eighty or more). Their size and disposition are commonly more or less +irregular. For the most part all the marginal spines lie in the equatorial +plane; but sometimes part of them are crowded into two or four parallel +girdles. Several species of this genus are very similar to some species of +_Heliodiscus_, and only differ in the absence of the medullary shell, +perhaps in consequence of the phylogenetic loss of it; if this be the case, +the former are to be derived from the latter (compare p. 410). + + + +Subgenus 1. _Trochodisculus_, Haeckel. + +_Definition._--Bases of the marginal spines free, not connected by a solid +equatorial girdle. + + +1. _Trochodiscus cenophacus_, n. sp. + +Disk with smooth surface. Pores regular, circular; eleven to twelve on the +radius. Marginal spines sixteen to twenty, conical, of irregular size and +disposition, about three times as long as broad, and as long as the radius +of the disk. + +_Dimensions._--Diameter of the disk 0.15, of the pores 0.006; length of the +spines 0.06 to 0.09, basal breadth 0.02 to 0.03. + +_Habitat._--Central Pacific, Station 266, depth 2750 fathoms. + + +2. _Trochodiscus medusinus_, n. sp. + +Disk with smooth surface. Pores regular, circular; nine to ten on the +radius. Marginal spines ten to twelve, equilateral triangular, deeply +sulcated, about half as long and broad as the radius of the disk. (Very +similar to _Heliosestrum medusinum_, Pl. 34, fig. 6, but without enclosed +medullary shell. Compare p. 410.) + +_Dimensions._--Diameter of the disk 0.2, of the pores 0.01; length of the +spines 0.05, basal breadth 0.05. + +_Habitat._--North Pacific, Station 241, depth 2300 fathoms. + + +{418}3. _Trochodiscus odontotrochus_, n. sp. + +Disk with smooth surface, in the distal part radially sulcated. Pores +irregular, roundish; twelve to fourteen on the radius. Marginal spines very +short and numerous (thirty to forty), conical, scarcely one-fourth as long +as the radius of the disk, which resembles a wheel with marginal teeth. + +_Dimensions._--Diameter of the disk 0.18, of the pores 0.004; length of the +spines 0.02, basal breadth 0.01. + +_Habitat._--South Atlantic, Station 332, depth 2200 fathoms. + + +4. _Trochodiscus solaris_, n. sp. + +Disk with smooth surface. Pores subregular, circular; eight to nine on the +radius. Marginal spines very numerous (sixty to eighty), in two to four +girdles densely crowded together, the largest as long as the diameter of +the disk, bent and conical. (Similar to _Heliodiscus solaster_, Pl. 34, +fig. 4, but without medullary shell.) + +_Dimensions._--Diameter of the disk 0.15, of the pores 0.008; length of the +spines 0.05 to 0.15, basal breadth 0.01. + +_Habitat._--South Pacific, Station 300, depth 1375 fathoms. + + +5. _Trochodiscus echiniscus_, n. sp. + +Disk with spiny surface. Pores irregular, roundish; ten to eleven on the +radius. Marginal spines conical, very numerous (forty to fifty), irregular +in size and disposition, the largest half as long as the radius of the +disk. (Similar to _Heliodiscus echiniscus_, Pl. 34, fig. 5, but without +medullary shell.) + +_Dimensions._--Diameter of the disk 0.18, of the pores 0.005 to 0.015; +length of the spines 0.02 to 0.04, basal breadth 0.01. + +_Habitat._--North Atlantic, Faeroee Channel, John Murray. + + + +Subgenus 2. _Pristodiscus_, Haeckel. + +_Definition._--Bases of the marginal spines connected by a solid siliceous +equatorial girdle. + + +6. _Trochodiscus stellaris_, n. sp. (Pl. 48, fig. 3). + +Disk with smooth surface. Pores subregular, circular; seven to eight on the +radius. Marginal spines twelve to sixteen, triangular, of subregular size +and disposition, about half as long as the radius of the disk, connected at +their broad base by a solid equatorial girdle of half the breadth; girdle +and spines radially striped. + +_Dimensions._--Diameter of the disk 0.25, of the pores 0.015; length of the +spines 0.04 to 0.06, basal breadth 0.02 to 0.04. + +_Habitat._--Central Pacific, Station 268, depth 2900 fathoms. + + +{419}7. _Trochodiscus cingillum_, n. sp. + +Disk with smooth surface, in the distal part radially sulcated. Pores +regular, circular; twelve to thirteen on the radius. Marginal spines twenty +to twenty-four, triangular, of equal size and at regular distances, only +one-fourth as long as the radius of the disk, connected at their broad base +by a solid equatorial girdle of the double breadth. (Similar to +_Heliodiscus cingillum_, Pl. 33, fig. 7, but without medullary shell.) + +_Dimensions._--Diameter of the disk 0.22, of the pores 0.004; length of the +spines 0.02, basal breadth 0.02 + +_Habitat._--South Pacific, Station 285, depth 2375 fathoms. + + + +Family XIX. #PHACODISCIDA#, Haeckel (Pls. 31-35). + +_Phacodiscida_, Haeckel, 1881, Prodromus, p. 456. + +_Definition._--#Discoidea# with simple extracapsular phacoid shell (or +lenticular latticed cortical shell), connected by radial beams with an +intracapsular, simple or double, concentric medullary shell, without +chambered equatorial girdles. + +The family #Phacodiscida# comprises a large number of splendid forms (about +a hundred species), which agree with the preceding Cenodiscida in the +possession of the characteristic extracapsular "phacoid shell," but differ +from them in having one or two intracapsular "medullary shells"; these +concentric spherical medullary shells are connected with the lenticular +cortical shell or phacoid shell by means of radial beams perforating the +central capsule. The Phacodiscida bear therefore the same relation to the +Cenodiscida that the Disphaerida and Trisphaerida do to the Monosphaerida. + +Formerly several species belonging to the family were described by +Ehrenberg and Johannes Mueller, but not distinguished from the Sphaeroidea, +genus _Haliomma_ (_e.g._, _Haliomma sol_ et _Haliomma humboldtii_ of the +former, _Haliomma amphidiscus_ of the latter). For these oldest known +species I constituted in 1862 my genus _Heliodiscus_ (Monogr. d. Radiol., +p. 436). Some other genera were afterwards (1875) figured by Ehrenberg as +_Periphaena_ and _Chilomma_. The rich material of the Challenger revealed +this family as very polymorphic and widely distributed, so that in my +Prodromus (1881, p. 457) I could enumerate eighteen different genera of +Phacodiscida. This number is here reduced to fifteen, uniting several of +them into one genus as "subgenera." + +_The Medullary Shell_ of the Phacodiscida, or the intracapsular latticed +shell, is either simple and spherical, or double, composed of two +concentric spheres, which are united by a variable number of radial beams. +We could distinguish therefore as two subfamilies the Carpodiscida (with +simple medullary shell) and the Thecodiscida (with double concentric +medullary shell); the former corresponding to the Carposphaerida (or +_Dyosphaeria_), the latter to the Thecosphaerida (or _Triosphaeria_). But +as this difference seems not to be so important as the different shape of +the disk margin, we prefer this latter as a character {420}for the +separation of subfamilies. The form of the medullary shells is commonly +quite spherical (as also in the above mentioned #Sphaeroidea#); sometimes +it is a little compressed in the same direction as the enclosing lenticular +phacoid shell. The diameter of the latter is commonly three to four times +as large as the diameter of the medullary shell; if this be double (in the +Thecodiscida) then the diameter of the outer medullary shell is commonly +three to four times as large as that of the inner. The radial beams +connecting the two seem to be very variable in number and disposition +(compare Pl. 31, fig. 8; Pl. 32, figs. 3, 4_a_, 7, 8_a_; Pl. 33, figs. 2, +3; Pl. 35, figs. 4, 8, 9, &c.). + +_The Radial Beams_, which connect the medullary shell with the cortical or +"phacoid shell," and which pierce the membrane of the lenticular central +capsule, are commonly aggregated into two polar bunches around the +shortened axis of the disk (compare Pl. 31, fig. 8; Pl. 32, figs. 3, 8; Pl. +33, figs. 2, 3, &c.). Their number seems to be usually between ten and +thirty. More rarely piercing radial beams lie also in the equatorial plane, +and then commonly as inner prolongations of the outer marginal spines; so +we find two opposite in one axis, in _Heliostylus_ (Pl. 34, figs. 1, 2), or +four opposite in pairs in two crossed axes, in _Phacostaurus_ (Pl. 31, +figs. 1, 2, 7). Often the thickness of the beams increases from the centre +towards the periphery. + +_The Phacoid Shell_, or the lenticular extracapsular cortical shell, +exhibits in the Phacodiscida quite the same general character as in the +Cenodiscida, above described (p. 410). Commonly the equatorial diameter of +the lens is twice to three times as large as the vertical diameter or the +shortened "main axis." The convexity of both opposite faces is either quite +even to the sharp margin (Pl. 31, fig. 2; Pl. 33, figs. 2, 5), or the +central part of the lens is more strongly vaulted, and often the margin is +thickened or truncated (Pl. 31, fig. 10; Pl. 35, fig. 7). The surface of +the lens is commonly smooth, but sometimes also covered with bristle-shaped +radial spines (Pl. 34, figs. 3, 5; Pl. 32, figs. 2, 3); rarely these spines +are prolonged and branched (Pl. 35, figs. 3, 5). The pores of the phacoid +shell are usually quite regular, circular, and regularly arranged, either +in more concentric or in more radial rows; the latter are sometimes +separated by radial crests arising towards the margin (Pl. 35, fig. 6). If +the wall of the phacoid shell be much thickened, the pores in its central +part are shorter and cylindrical, in its marginal part longer and conical +(Pl. 31, fig. 7; Pl. 32, fig. 1). + +_The Margin of the Lens_ of the Phacodiscida is very polymorphic, and +serves mainly for the separation of genera. In the first subfamily, +Sethodiscida, it is either quite simple (Pl. 35, figs. 6-8) or surrounded +by a thin solid equatorial girdle, the basal part of which is often +radially striped (Pl. 32, figs. 7, 8). In the second subfamily, +Heliosestrida, we find on the margin a small number of radial spines in the +equatorial plane regularly disposed, either two opposite in one axis (Pl. +31, figs. 9-12) or four opposite in pairs in two crossed axes (Pl. 31, +figs. 1-8), or eight opposite in pairs in four axes, crossed at angles of +45d (Pl. 34, figs. 3, 6); in the latter case we can sometimes distinguish +{421}(as in many Medusae) four larger perradial spines alternating with +four smaller interradial spines. Often in one and the same species occur +abnormalities in number and disposition of the radial spines, three or five +spines instead of four, or also seven or nine spines instead of eight; +often both halves of the disk become asymmetrical. If the number of the +marginal spines exceed eight to ten, they commonly become very variable in +size and irregular in disposition; these variations characterise the third +subfamily, Heliodiscida. Commonly also here all spines lie in the +equatorial plane; but sometimes they become crowded in several parallel +circles on both sides of the margin (Pl. 32, fig. 1). The form of the +marginal spines is commonly conical or flattened triangular, often also +pyramidal or deeply furrowed (Pl. 31, figs. 6-9). Very rarely the spines +are fenestrated (Pl. 35, fig. 1); only in one genus (_Heliodrymus_) they +are all or partly branched (Pl. 33, fig. 9; Pl. 35, figs. 3, 5). + +The peculiar development of the phacoid shell has been already described by +J. Mueller (compare my Monograph, 1862, pp. 156, 438). + +_The Central Capsule_ of the Phacodiscida is everywhere circular, +lenticular, envelops the medullary shell, and is enclosed by the phacoid +shell, perforated by the radial beams, which connect the latter to the +former. + +_Synopsis of the Genera of the Phacodiscida._ + + ------------------------------------------------------------------------- + I. Subfamily Sethodiscida. + Margin of the disk without radial spines. + ------------------------------------------------------------------------- + Margin simple, without {Medullary shell simple, 181. _Sethodiscus_. + equatorial girdle. { + {Medullary shell double, 182. _Phacodiscus_. + + Margin surrounded by a {Medullary shell simple, 183. _Periphaena_. + hyaline equatorial girdle. { + {Medullary shell double, 184. _Perizona_. + ------------------------------------------------------------------------- + II. Subfamily Heliosestrida. + Margin of the disk with two to eight solid radial spines, usually + quite regularly disposed. (Number usually constant.) + ------------------------------------------------------------------------- + Two radial spines {Medullary shell simple, 185. _Sethostylus_. + (opposite in one axis). { + {Medullary shell double, 186. _Phacostylus_. + + Three radial spines. Medullary shell simple, 187. _Triactiscus_. + + Four radial spines (in {Medullary shell simple, 188. _Sethostaurus_. + cross form). { + {Medullary shell double, 189. _Phacostaurus_. + + Six radial spines. Medullary shell simple, 190. _Distriactis_. + + Eight radial spines. {Medullary shell simple, 191. _Heliosestrum_. + { + {Medullary shell double, 192. _Astrosestrum_. + ------------------------------------------------------------------------- + III. Subfamily Heliodiscida. + Margin of the disk with numerous (ten to twenty or more) radial + spines, usually irregularly disposed. (Number variable.) + ------------------------------------------------------------------------- + Radial spines all simple, {Medullary shell simple, 193. _Heliodiscus_. + not branched. { + {Medullary shell double, 194. _Astrophacus_. + + Radial spines all or }Medullary shell simple, 195. _Heliodrymus_. + partly branched. } + + + +{422}Subfamily 1. SETHODISCIDA, Haeckel, 1881, Prodromus, p. 457. + +_Definition._--#Phacodiscida# without radial spines on the margin of the +disk. + + + +Genus 181. _Sethodiscus_,[220] Haeckel, 1881, Prodromus, p. 457. + +_Definition._--#Phacodiscida# with simple medullary shell and simple margin +of the circular disk, without surrounding equatorial girdle and without +radial spines. + +The genus _Sethodiscus_ is the most simple and primitive form of all +Phacodiscida, and may be regarded as the common ancestral form of this +family. The simple spherical medullary shell is connected by a variable +number of radial beams with the lenticular or discoidal cortical shell (or +"phacoid shell"). The margin of this latter is quite simple, circular, +without solid equatorial girdle or radial spines. From the nearly allied +genus _Carposphaera_ of the #Sphaeroidea#, its probable ancestral form, +_Sethodiscus_ can be derived simply by lenticular compression of the +spheroidal cortical shell. + + + +Subgenus 1. _Sethodiscinus_, Haeckel. + +_Definition._--Surface of the disk smooth, without radial ribs or spines. + + +1. _Sethodiscus phacoides_, n. sp. + +Disk with smooth surface, three times as broad as the medullary shell. +Pores regular, circular; fourteen to fifteen on the radius of the disk. +(Very similar to _Periphaena cincta_, Pl. 33, fig. 4, but without the +girdle of the margin.) + +_Dimensions._--Diameter of the disk 0.2, of the medullary shell 0.07, of +the pores 0.005. + +_Habitat._--Pacific, central area, Stations 270 to 274, in various depths. + + +2. _Sethodiscus macroporus_, n. sp. + +Disk with smooth surface, twice as broad as the medullary shell. Pores +regular, circular, very large; five to six on the radius of the disk. +(Remarkable for the extraordinary size of the pores, which reaches half the +radius of the medullary shell.) + +_Dimensions._--Diameter of the disk 0.1, of the medullary shell 0.05, of +the pores 0.012. + +_Habitat._--North Atlantic, Gulf Stream, Faeroee Channel, John Murray. + + +3. _Sethodiscus microporus_, n. sp. + +Disk with smooth surface, four times as broad as the medullary shell. Pores +regular, circular, very small; twenty-two to twenty-four on the radius of +the disk. (The small pores are scarcely half as broad as the thick bars +between them.) + +{423}_Dimensions._--Diameter of the disk 0.25, of the medullary shell 0.06, +of the pores 0.002. + +_Habitat._--South Pacific, Station 288, surface. + + +4. _Sethodiscus lenticula_, n. sp. (Pl. 33, figs. 1, 2). + +Disk with smooth surface, four times as broad as the medullary shell. Pores +irregular, polygonal; eight to nine on the radius of the disk. (The pores +of the medullary shell, fig. 2, are also irregular, polygonal, or +roundish.) + +_Dimensions._--Diameter of the disk 0.17, of the medullary shell 0.04, of +the pores 0.01. + +_Habitat._--Pacific, central area, Station 274, depth 2750 fathoms. + + +5. _Sethodiscus macrococcus_, n. sp. (Pl. 33, fig. 3). + +Disk with smooth surface, two and a half times as broad as the medullary +shell. Pores irregular, polygonal; eleven to twelve on the radius of the +disk. (The pores of the medullary shell, fig. 3, are regular, circular, +with elevated hexagonal frames between them. The figured specimen is a +young one, both halves of the biconvex disk being not yet united in the +equatorial plane.) + +_Dimensions._--Diameter of the disk 0.16, of the medullary shell 0.065, of +the pores 0.01. + +_Habitat._--North Pacific, Station 244, depth 2900 fathoms. + + +6. _Sethodiscus micrococcus_, n. sp. + +Disk with smooth surface, five times as broad as the medullary shell. Pores +irregular, roundish, very small; twenty-six to twenty-eight on the radius +of the disk. (The pores of the small medullary shell are regularly +circular, of the same size as those of the disk.) + +_Dimensions._--Diameter of the disk 0.2, of the medullary shell 0.04, of +the pores 0.002. + +_Habitat._--South Atlantic, Station 335, depth 1425 fathoms. + + + +Subgenus 2. _Sethodisculus_, Haeckel. + +_Definition._--Surface of the disk with elevated radial ribs or spines. + + +7. _Sethodiscus radiatus_, Haeckel. + + _Haliomma radians_, Ehrenberg, 1854, Mikrogeol., Taf. xix. fig. 50. + + _Haliomma radiatum_, Ehrenberg, 1854, Mikrogeol., Taf. xxi. fig. 54. + +Disk with radiated surface, four times as broad as the medullary shell. +Pores regularly circular; nine to ten on the radius of the disk, arranged +in radial series (about forty), which are separated by smooth crests, not +prominent on the smooth margin. + +_Dimensions._--Diameter of the disk 0.12, of the medullary shell 0.03, of +the pores 0.003. + +_Habitat._--Fossil in Tertiary deposits of the Mediterranean, Greece, +Sicily, Oran, &c. + + +{424}8. _Sethodiscus echinatus_, Haeckel. + + _Haliomma echinatum_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. + Berlin, p. 74, Taf. xxvii. fig. 2. + +Disk with radiated thorny surface, three times as broad as the medullary +shell. Pores regular, circular; eleven to twelve on the radius of the disk, +arranged in radial series (about sixty), which are separated by thorny +crests, prominent a little on the dentated margin. + +_Dimensions._--Diameter of the disk 0.18, of the medullary shell 0.06, of +the pores 0.01. + +_Habitat._--Fossil in the rocks of Barbados. + + +9. _Sethodiscus cristatus_, n. sp. + +Disk with radiated surface, four times as broad as the medullary shell. +Pores regularly circular; sixteen to seventeen on the radius of the disk, +arranged in radial series (about eighty), which are separated in the distal +half by smooth elevated crests, strongly prominent on the dentated margin. +(Very similar to _Phacodiscus cristatus_, Pl. 35, fig. 6, but with simple +medullary shell.) + +_Dimensions._--Diameter of the disk 0.2, of the medullary shell 0.05, of +the pores 0.005. + +_Habitat._--South Pacific, Station 285, depth 2375 fathoms. + + + +Genus 182. _Phacodiscus_,[221] Haeckel, 1881, Prodromus, p. 457. + +_Definition._--#Phacodiscida# with double medullary shell and simple margin +of the circular disk, without surrounding equatorial girdle and without +radial spines. + +The genus _Phacodiscus_ differs from the ancestral genus _Sethodiscus_ only +in the duplication of the medullary shell, and has therefore the same +relation to it that _Thecosphaera_ in the #Sphaeroidea# exhibits to +_Carposphaera_. Both former discoidal genera differ from the two latter +spheroidal by the lenticular flattening of the cortical shell. + + + +Subgenus 1. _Phacodiscinus_, Haeckel. + +_Definition._--Surface of the disk smooth, without radial ribs or spines. + + +1. _Phacodiscus rotula_, n. sp. (Pl. 35, fig. 7). + +Disk with smooth surface, four and a half times as broad as the outer and +fourteen times as broad as the inner medullary shell. Pores regularly +circular; sixteen to eighteen on the radius of the disk. Margin of the lens +very thick, truncated, nearly as broad as the outer medullary shell. + +_Dimensions._--Diameter of the disk 0.21, of the outer medullary shell +0.045, of the inner 0.015; pores 0.008. + +_Habitat._--North Pacific, Station 224, depth 1850 fathoms. + + +{425}2. _Phacodiscus lentiformis_, n. sp. (Pl. 35, fig. 8). + +Disk with smooth surface, three and a half times as broad as the outer, and +ten times as broad as the inner medullary shell. Pores regularly circular; +twelve to thirteen on the radius of the disk. Margin of the disk sharp, as +in a biconvex lens. + +_Dimensions._--Diameter of the disk 0.25, of the outer medullary shell +0.07, of the inner 0.025; pores 0.01. + +_Habitat._--Central Pacific, Station 265, depth 2900 fathoms; fossil in +Barbados. + + +3. _Phacodiscus grandis_, n. sp. + +Disk with thorny surface, five times as broad as the outer, and fifteen +times as broad as the inner medullary shell. Pores regularly circular; +twenty-two to twenty-four on the radius of the disk. Margin of the disk +thick, rounded. + +_Dimensions._--Diameter of the disk 0.45, of the outer medullary shell +0.09, of the inner 0.03; pores 0.01. + +_Habitat._--Western Tropical Pacific, Station 225, depth 4475 fathoms. + + + +Subgenus 2. _Phacodisculus_, Haeckel. + +_Definition._--Surface of the disk with elevated radial ribs or spines. + + +4. _Phacodiscus echiniscus_, n. sp. + +Disk with spiny surface, four times as broad as the outer, and ten times as +broad as the inner medullary shell. Pores irregularly roundish; fourteen to +fifteen on the radius of the disk. Margin of the disk sharp, as in a +biconvex lens. + +_Dimensions._--Diameter of the disk 0.3, of the outer medullary shell 0.75, +of the inner 0.03; pores 0.007. + +_Habitat._--South Atlantic, Station 332, depth 2200 fathoms. + + +5. _Phacodiscus clypeus_, n. sp. (Pl. 35, figs. 6, 9). + +Disk with radiated surface, four times as broad as the outer, and twelve +times as broad as the inner medullary shell. Pores regularly circular; +sixteen to eighteen on the radius of the disk; in the distal half disposed +in sixty to seventy radial series, which are separated by prominent crests; +the sharp margin therefore a little jagged. + +_Dimensions._--Diameter of the disk 0.2, of the outer medullary shell 0.05, +of the inner 0.017; pores 0.006. + +_Habitat._--Pacific, central area, Station 266, depth 2750 fathoms. + + + +{426}Genus 183. _Periphaena_,[222] Ehrenberg, 1873 Monatsber. d. k. preuss. +Akad. d. Wiss. Berlin, p. 246. + +_Definition._--#Phacodiscida# with simple medullary shell, without radial +spines, but with a solid equatorial girdle around the margin of the +lenticular disk. + +The genus _Periphaena_, founded by Ehrenberg in 1873 for the fossil +_Periphaena decora_ of Barbados, differs from its ancestral form +_Sethodiscus_ in the development of a very thin siliceous solid girdle +around the margin of the lenticular disk; this girdle lies in the +equatorial plane of the shell, and reappears in similar form in +_Perichlamydium_ among the Porodiscida, in _Spongophacus_ among the +Spongodiscida, and in _Zonodiscus_ among the Cenodiscida. + + +1. _Periphaena cincta_, n. sp. (Pl. 33, fig. 4). + +Disk with smooth surface, four times as broad as the medullary shell. Pores +regularly circular; fourteen to sixteen on the radius of the disk. Girdle +of the margin about half as broad as the radius of the medullary shell, in +the distal half structureless, in the proximal half with seventy to eighty +short radial ribs. + +_Dimensions._--Diameter of the disk 0.2, of the medullary shell 0.05, of +the pores 0.005. + +_Habitat._--Central Pacific, Station 268, depth 2900 fathoms. + + +2. _Periphaena decora_, Ehrenberg. + + _Periphaena decora_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. + Berlin, p. 80, Taf. xxviii. fig. 6. + +Disk with smooth surface, three times as broad as the medullary shell. +Pores regular, circular; twenty to twenty-two on the radius of the disk, +disposed in radial series. Girdle of the margin nearly as broad as the +radius of the medullary shell, in the distal half structureless, in the +proximal half with eighty to ninety short radial ribs. + +_Dimensions._--Diameter of the disk 0.25, of the medullary shell 0.08, of +the pores 0.06. + +_Habitat._--Fossil in Barbados. + + +3. _Periphaena statoblastus_, n. sp. + +Disk with smooth surface, five times as broad as the medullary shell. Pores +regularly circular; twenty-four to twenty-six on the radius of the disk, +disposed in radial series, those in the distal half of the disk being +separated by piercing radial beams. Girdle of the margin twice as broad as +the radius of the medullary shell, in the whole breadth with one hundred +and twenty to one hundred and thirty piercing radial ribs, the +prolongations of the beams. + +_Dimensions._--Diameter of the disk 0.3, of the medullary shell 0.06, of +the pores 0.04. + +_Habitat._--South Pacific, Station 300, depth 1375 fathoms. + + + +{427}Genus 184. _Perizona_,[223] Haeckel, 1881, Prodromus, p. 457. + +_Definition._--#Phacodiscida# with double medullary shell, without radial +spines, but with a solid equatorial girdle around the margin of the +lenticular disk. + +The genus _Perizona_ differs from its ancestral form _Phacodiscus_ in the +development of a thin solid siliceous girdle, lying in the equatorial +plane around the margin of the disk. The two genera bear the same relation +to each other that _Periphaena_ bears to _Sethodiscus_. But in the two +latter genera the spherical medullary shell is simple, in the two former +double. + + +1. _Perizona scutella_, n. sp. (Pl. 32, fig. 7). + +Disk with smooth surface, in the distal third radiated, four times as broad +as the outer, and ten times is broad as the inner medullary shell. Pores +subregular, circular; thirteen to fourteen on the radius of the disk, in +the marginal part separated by eighty to ninety prominent radial crests, +which are prolonged into the proximal half of the solid girdle. Breadth of +the girdle equal to that of the inner medullary shell. + +_Dimensions._--Diameter of the disk 0.25, of the outer medullary shell +0.06, of the inner 0.025; pores 0.007. + +_Habitat._--Pacific, central area, Station 268, depth 2900 fathoms. + + +2. _Perizona pterygota_, n. sp. (Pl. 32, figs. 8, 8_a_). + +Disk with smooth surface, six times as broad as the outer, and fifteen +times as broad as the inner medullary shell. Pores regularly circular; +eighteen to twenty on the radius of the disk. Margin much thickened and +truncated, abruptly separated in the equatorial circumference from the +peripheral sharp margin of the solid girdle; breadth of the girdle equal to +that of the outer medullary shell. + +_Dimensions._--Diameter of the disk 0.25, of the outer medullary shell +0.04, of the inner 0.015; pores 0.006. + +_Habitat._--Pacific, central area, Station 266, depth 2750 fathoms. + + + +Subfamily 2. HELIOSESTRIDA, Haeckel. + +_Definition._--#Phacodiscida# with a constant number of radial spines on +the margin of the disk (two, three, four, six, or eight), which are +commonly regularly disposed (sometimes more or less irregularly). + + + +{428}Genus 185. _Sethostylus_,[224] Haeckel, 1881, Prodromus, p. 457. + +_Definition._--#Phacodiscida# with simple medullary shell and with two +radial spines on the margin of the disk, opposite in the equatorial axis. + +The genus _Sethostylus_ opens the series of the Heliosestrida or of those +Phacodiscida in which a constant number of radial spines (two to eight) is +more or less regularly disposed on the margin of the disk. All these +marginal spines lie in the equatorial plane of the lens, and have in the +same species a rather constant number and similar size, a certain form and +disposition. Sometimes they incline more or less to irregular variations. +In _Sethostylus_ there are only two spines, opposite in the equatorial +diameter of the lens; it corresponds to _Stylocyclia_ among the +Coccodiscida, and to _Xiphodictya_ among the Porodiscida. + + + +Subgenus 1. _Sethostylium_, Haeckel. + +_Definition._--Margin of the disk simple, smooth, without equatorial girdle +and without a corona of marginal spines. + + +1. _Sethostylus distyliscus_, n. sp. (Pl. 31, fig. 9). + +Disk with smooth surface, three times as broad as the medullary shell. +Pores regular, circular; nine to ten on the radius of the disk, in the +outer rows cylindrical. Margin of the disk simple, smooth, thin, without +peculiar equatorial girdle, radially striped by the prominent beams of the +peripheral series of pores. Both marginal spines of equal size, pyramidal, +sulcated, about as long as the radius of the disk and as broad at the base +as the medullary shell. + +_Dimensions._--Diameter of the disk 0.13 to 0.16, of the medullary shell +0.04 to 0.05; length of both opposite spines 0.06 to 0.08, basal breadth +0.03 to 0.04. + +_Habitat._--Pacific, central area, Station 265, depth 2900 fathoms. + + +2. _Sethostylus dicylindrus_, n. sp. (Pl. 31, fig. 10). + +Disk with smooth surface, four times as broad as the medullary shell. Pores +regular, circular; sixteen to eighteen on the radius of the disk. Margin of +the disk simple, smooth, thick, without peculiar equatorial girdle. Both +marginal spines cylindrical, about as long as the diameter of the disk, +about twice as broad as a single pore. (Walls of the disk in the central +part twice to three times as thick as in the peripheral part.) + +_Dimensions._--Diameter of the disk 0.2, of the medullary shell 0.05; +length of both spines 0.2 to 0.3, breadth 0.008. + +_Habitat._--Pacific, central area, Station 268, depth 2900 fathoms. + + + +{429}Subgenus 2. _Heliostylus_, Haeckel, 1881, Prodromus, p. 457. + +_Definition._--Margin of the disk with a solid equatorial girdle or a +corona of radial spines. + + +3. _Sethostylus dentatus_, n. sp. (Pl. 34, fig. 1). + + _Heliostylus dentatus_, Haeckel, 1881, Prodromus et Atlas (pl. xxxiv. + fig. 1). + +Disk with smooth surface, six times as broad as the medullary shell. Pores +regular, circular; eighteen to twenty on the radius of the disk. Margin of +the disk with a broad solid equatorial girdle, which bears fifty to sixty +strong conical teeth on the periphery; teeth about as long as the diameter +of the medullary shell. Both opposite marginal spines cylindro-conical, +about as long as the diameter of the disk, and as broad as the girdle. + +_Dimensions._--Diameter of the disk 0.3, of the medullary shell 0.05; +length of both main spines 0.2 to 0.3, breadth 0.02. + +_Habitat._--Pacific, central area, Station 272, depth 2600 fathoms. + + +4. _Sethostylus serratus_, n. sp. (Pl. 34, fig. 2). + + _Heliostylus serratus_, Haeckel, 1881, Prodromus et Atlas (pl. xxxiv. + fig. 2). + +Disk with smooth surface, four times as broad as the medullary shell. Pores +regular, circular; fourteen to sixteen on the radius of the disk. Margin +with a broad solid equatorial girdle, which bears forty to fifty strong +conical teeth on the periphery; teeth about as long as the radius of the +medullary shell. Both opposite marginal spines spindle-shaped, about as +long as the diameter of the disk, and as broad as the girdle. + +_Dimensions._--Diameter of the disk 0.3, of the medullary shell 0.075; +length of both main spines 0.2 to 0.3, breadth 0.03. + +_Habitat._--South Atlantic, Station 332, depth 2200 fathoms. + + +5. _Sethostylus hastatus_, n. sp. + +Disk with smooth surface, two and a half times as broad as the medullary +shell. Pores irregular, roundish; ten to twelve on the radius of the disk. +Margin with a broad solid equatorial girdle, which bears on the periphery +six conical teeth, three on each half between the two main spines, which +are cylindrical, longer than the diameter of the disk, and half as broad as +the girdle. (This species can be derived from _Heliosestrum_, two opposite +spines of the eight marginal spines being much stronger developed than the +other six.) + +_Dimensions._--Diameter of the disk 0.15, of the medullary shell 0.06; +length of both main spines 0.2, breadth 0.01. + +_Habitat._--North Atlantic, Station 354, surface. + + +{430}6. _Sethostylus spicatus_, n. sp. + +Disk with spiny surface, four times as broad as the medullary shell. Pores +irregular roundish, with many unequal conical spines between them. Margin +with an equatorial girdle, composed of three to four concentric series of +conical radial spines, about as long as the radius of the medullary shell. +Both main spines very large, cylindrical, longer than the diameter of the +disk, and as broad as the radius of the medullary shell. + +_Dimensions._--Diameter of the disk 0.2, of the medullary shell 0.05; +length of the main spines 0.3 or more, breadth 0.025. + +_Habitat._--Fossil in the rocks of Barbados, Haeckel; living in the depths +of the Equatorial Atlantic, Station 348, depth (2450) fathoms. + + + +Genus 186. _Phacostylus_,[225] Haeckel, 1881, Prodromus, p. 457. + +_Definition._--#Phacodiscida# with double medullary shell and with two +radial spines on the margin of the disk, opposite in the equatorial axis. + +The genus _Phacostylus_ differs from the foregoing _Sethostylus_ by the +duplication of the medullary shell, and bears the same relation to it as +_Phacodiscus_ does to _Sethodiscus_, or as _Amphicyclia_ in the +Coccodiscida does to _Stylocyclia_. + + + +Subgenus 1. _Phacostylium_, Haeckel. + +_Definition._--Margin of the disk simple, smooth, without equatorial +girdle, and without a corona of marginal spines. + + +1. _Phacostylus amphistylus_, n. sp. (Pl. 31, fig. 12). + +Disk with smooth surface, four times as broad as the outer, and twelve +times as broad as the inner medullary shell. Pores regular, circular; +twelve to fourteen on the radius of the disk. Margin of the disk simple, +smooth, without spines and equatorial girdle. Both polar spines conical, +longer than the diameter of the disk, furrowed at the base, and twice as +broad as the inner medullary shell. + +_Dimensions._--Diameter of the disk 0.16 to 0.18, of the outer medullary +shell 0.045, of the inner 0.015; length of the polar spines 0.2, basal +breadth 0.03. + +_Habitat._--Pacific, central area, Station 272, depth 2600 fathoms. + + +2. _Phacostylus amphixiphus_, n. sp. + +Disk with smooth surface, three times as broad as the outer, and eight +times as broad as the inner medullary shell. Pores irregular, roundish; ten +to eleven on the radius. Margin of the disk {431}simple, smooth, without +spines and equatorial girdle. Both polar spines sword-shaped triangular, +two-edged, about as long as the radius of the disk, and as broad at the +base as the inner medullary shell. + +_Dimensions._--Diameter of the disk 0.15, of the outer medullary shell +0.05, of the inner 0.02; length of the polar spines 0.08, basal breadth +0.02. + +_Habitat._--Indian Ocean, Madagascar, Rabbe, surface. + + + +Subgenus 2. _Astrostylus_, Haeckel. + +_Definition._--Margin of the disk with a solid equatorial girdle or a +corona of radial spines. + + +3. _Phacostylus amphipyramis_, n. sp. + +Disk with spiny surface, four and a half times as broad as the outer, and +fourteen times as broad as the inner medullary shell. Pores irregular, +roundish; eight to ten on the radius. Margin of the disk with a corona of +irregular, radial spines. Both opposite polar spines pyramidal, twice as +long as broad, and nearly as long as the radius of the disk. + +_Dimensions._--Diameter of the disk 0.22, of the outer medullary shell +0.05, of the inner 0.016; length of the polar spines 0.1, basal breadth +0.05. + +_Habitat._--Western Tropical Pacific, Station 225, depth 4475 fathoms. + + +4. _Phacostylus caudatus_, n. sp. (Pl. 32, fig. 6). + + _Astrosestrum caudatum_, Haeckel, 1881, Prodromus et Atlas (pl. xxxii. + fig. 6). + +Disk with smooth surface, two and a half times as broad as the outer, and +six times as broad as the inner medullary shell. Pores regular, circular; +six to seven on the radius of the disk. Margin with a solid equatorial +girdle, and irregularly bordered with eight to ten conical spines; two +opposite of these are much longer than the others. (This species can be +derived from _Astrosestrum_, two opposite marginal spines being much more +strongly developed than the six to eight others.) + +_Dimensions._--Diameter of disk 0.12, of the outer medullary shell 0.05, of +the inner 0.02; length of the polar spines 0.1 to 0.25, basal breadth +0.025. + +_Habitat._--North Pacific, Station 244, depth 2900 fathoms. + + +5. _Phacostylus maximus_, n. sp. + +Disk with smooth surface, five times as broad as the outer, and ten times +as broad as the inner medullary shell. Pores regular, circular; twenty to +twenty-two on the radius. Margin with a solid equatorial girdle, bearing on +the periphery one hundred to one hundred and twenty plain teeth, and two +very large polar spines, which are cylindrical, longer than the diameter of +the disk, and as broad at the furrowed base as the radius of the outer +medullary shell. (Similar to _Sethostylus dentatus_, Pl. 34, fig. 1, but +much larger, and with a double medullary shell.) +{432}_Dimensions._--Diameter of the disk 0.4, of the outer medullary shell +0.08, of the inner 0.04; length of the polar spines 0.5, basal breadth +0.04. + +_Habitat._--Fossil in the rocks of Barbados. + + + +Genus 187. _Triactiscus_,[226] Haeckel, 1881, Prodromus, p. 457. + +_Definition._--#Phacodiscida# with simple medullary shell, and with three +radial spines on the margin of the disk, placed in the equatorial plane. + +The genus _Triactiscus_ exhibits on the margin of the lenticular phacoid +shell three radial solid spines, the distance between which is sometimes +equal, at other times unequal. Either all the three spines are of equal +size and similar form, or one odd arm is smaller than the two paired arms. +The triradial form of this genus is repeated in _Tripodocyclia_ among the +Coccodiscida, and in _Tripodictya_ among the Porodiscida. The medullary +shell of _Triactiscus_ is simple. + + +1. _Triactiscus tripyramis_, n. sp. (Pl. 33, fig. 6). + +Disk with smooth surface and smooth margin, three times as broad as the +medullary shell. Pores regular, circular; twelve to thirteen on the radius +of the disk. Three radial spines of nearly equal size and equidistant, or +one odd spine a little smaller, and the opposite angle (between the paired +spines) also smaller. Spines pyramidal, with broad prominent edges, one to +one and a half times as long as the radius of the disk, as broad at the +base as the radius of the medullary shell. + +_Dimensions._--Diameter of the disk 0.15; of the medullary shell 0.05, +pores 0.006. + +_Habitat._--Pacific, central area, Station 272, depth 2600 fathoms. + + +2. _Triactiscus tricuspis_, n. sp. (Pl. 33, fig. 5). + +Disk with smooth surface and smooth margin, five times as broad as the +medullary shell. Pores irregular, roundish; ten to eleven on the radius of +the disk. Three radial spines of unequal size and at unequal distances, +very short, conical, not longer than the radius of the medullary shell. + +_Dimensions._--Diameter of the disk 0.15, of the medullary shell 0.03; +pores 0.004 to 0.008. + +_Habitat._--Central Pacific, Station 268, depth 2900 fathoms. + + +3. _Triactiscus tripodiscus_, Haeckel. + + _Haliomma triactis_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. + Berlin, p. 236, Taf. xxviii. fig, 4. + +Disk with thorny surface and spiny margin, three times as broad as the +medullary shell. Pores regular, circular; eight to nine on the radius of +the disk. Three radial spines of different {433}size and at unequal +distances, one odd spine as long as the radius, both paired spines as long +as the diameter of the disk; the odd angle between the latter is smaller. +Spines pyramidal, with broad edges. + +_Dimensions._--Diameter of the disk 0.16, of the medullary shell 0.05, +pores 0.008. + +_Habitat._--Fossil in the rocks of Barbados. + + + +Genus 188. _Sethostaurus_,[227] Haeckel, 1881, Prodromus, p. 457. + +_Definition._--#Phacodiscida# with simple medullary shell and with four +radial spines on the margin of the disk, crossed in the equatorial plane. + +The genus _Sethostaurus_ exhibits four marginal spines, which form commonly +a more or less regular cross in the equatorial plane. Sometimes the size +and disposition of the four spines become more or less different, and also +the angles between them vary; the regular rectangular cross passes over +into a bilateral or irregular form. The medullary shell is simple. The same +cross-form of the disk is seen in _Staurocyclia_ among the Coccodiscida, +and in _Staurodictya_ among the Porodiscida. + + + +Subgenus 1. _Sethostaurium_, Haeckel. + +_Definition._--Margin of the disk without a solid equatorial girdle or a +corona of spines. + + +1. _Sethostaurus orthostaurus_, n. sp. (Pl. 31, figs. 1, 2). + +Disk with smooth surface, three times as broad as the medullary shell. +Pores regular, circular; thirteen to fourteen on the radius of the disk. +Margin simple, smooth, without girdle. Four crossed spines equal, +pommel-shaped, angular, contracted at the base, scarcely as long as the +diameter of the medullary shell. + +_Dimensions._--Diameter of the disk 0.16, of the medullary shell 0.05; +length of the crossed spines 0.04, breadth 0.02. + +_Habitat._--Pacific, central area, Station 266, depth 2750 fathoms. + + +2. _Sethostaurus conostaurus_, n. sp. (Pl. 34, figs. 7, 8). + +Disk with spiny surface, three times as broad as the medullary shell. Pores +irregular, roundish; seven to eight on the radius. Margin simple, smooth, +without girdle. Four crossed spines subregular, equal, conical, about as +long as the diameter and as broad at the base as the radius of the +medullary shell. (Fig. 7 exhibits the normal form, fig. 8 an abnormality +with five spines.) + +_Dimensions._--Diameter of the disk 0.2, of the medullary shell 0.06; +length of the crossed spines 0.05, basal breadth 0.03. + +_Habitat._--South Atlantic, Station 333, surface. + + +{434}3. _Sethostaurus rhombostaurus_, n. sp. (Pl. 31, fig. 4). + +Disk with smooth surface, two and a half times as broad as the medullary +shell. Pores regular, circular; ten to eleven on the radius. Margin simple, +smooth, without girdle. Two opposite spines longer than the diameter of the +disk, four times as long as the two others, which only equal its radius. +Spines sword-shaped, angular. + +_Dimensions._--Diameter of the disk 0.14, of the medullary shell 0.06; +length of the major spines 0.2, of the minor 0.05, breadth 0.025. + +_Habitat._--North Atlantic, Station 353, depth 2965 fathoms. + + +4. _Sethostaurus recurvatus_, n. sp. (Pl. 31, fig. 3). + +Disk with smooth surface, three times as broad as the medullary shell. +Pores irregular, roundish; eight to nine on the radius. Margin simple, +smooth, without girdle. Four spines cylindrical, irregularly curved, of +different sizes; one single very large, much longer than the three others; +two opposite lateral spines recurved, hook-shaped. + +_Dimensions._--Diameter of the disk 0.15, of the medullary shell 0.05; +length of the major spine 0.32, of the opposite spine 0.16, of both lateral +spines 0.08. + +_Habitat._--South Pacific, Station 295, depth 1500 fathoms. + + + +Subgenus 2. _Heliostaurus_, Haeckel 1881, Prodromus, p. 457. + +_Definition._--Margin of the disk with a solid equatorial girdle or a +corona of spines. + + +5. _Sethostaurus cruciatus_, n. sp. (Pl. 31, fig. 5). + + _Heliostaurus cruciatus_, Haeckel, 1881, Prodromus et Atlas (pl. xxxi. + fig. 5). + +Disk with smooth surface, three times as broad as the medullary shell. +Pores regular, circular; eleven to twelve on the radius. Margin with a +solid, radially striped girdle, which bears on the periphery forty to fifty +triangular pointed teeth of unequal length. Four crossed spines of equal +size and similar form, pyramidal, sulcated, about as long as the radius of +the disk, as broad at the base as the girdle. + +_Dimensions._--Diameter of the disk 0.2, of the medullary shell 0.06; +length of the crossed spines 0.1, basal breadth 0.02. + +_Habitat._--Pacific, central area, Station 271, depth 2425 fathoms. + + +6. _Sethostaurus coronatus_, n. sp. + +Disk with spiny surface, twice as broad as the medullary shell. Pores +irregular, roundish; nine to ten on the radius. Margin of the disk with a +solid broad girdle, bearing on the periphery a corona of thirty to forty +flat tongue-shaped teeth of different length. Four crossed spines +{435}prismatic with prominent edges, about as long as the diameter of the +disk, and as broad as the girdle. + +_Dimensions._--Diameter of the disk 0.16, of the medullary shell 0.08, +length of the crossed spines 0.18, breadth 0.02. + +_Habitat._--Pacific, central area, Station 268, depth 2900 fathoms. + + +7. _Sethostaurus gigas_, n. sp. + +Disk with smooth surface, four times as broad as the medullary shell. Pores +regular, circular; twenty to twenty-two on the radius. Margin of the disk +with a narrow solid girdle, bearing on the periphery one hundred to one +hundred and twenty slender flat pointed teeth. Four crossed spines equal, +conical, about as long as the radius of the disk, as broad at their +furrowed base as the radius of the medullary shell. + +_Dimensions._--Diameter of the disk 0.4, of the medullary shell 0.1; length +of the crossed spines 0.5, basal breadth 0.05. + +_Habitat._--Western Tropical Pacific, Station 225, depth 4475 fathoms. + + + +Genus 189. _Phacostaurus_,[228] Haeckel, 1881, Prodromus, p. 457. + +_Definition._--#Phacodiscida# with double medullary shell and with four +radial spines on the margin of the disk, crossed in the equatorial plane. + +The genus _Phacostaurus_ differs from the foregoing _Sethostaurus_ by the +duplication of the medullary shell, and bears to it the same relation as +_Phacodiscus_ does to _Sethodiscus_. Also in this genus the cross of the +shell is commonly regular, rectangular, sometimes more or less irregular. + + + +Subgenus 1. _Phacostaurium_, Haeckel. + +_Definition._--Margin of the disk without a solid equatorial girdle or a +corona of spines. + + +1. _Phacostaurus oceanidum_, n. sp. (Pl. 31, fig. 6). + +Disk with smooth surface, three times as broad as the outer and eight times +as broad as the inner medullary shell. Pores regular, circular; eleven to +twelve on the diameter of the disk. Margin smooth. Four crossed spines +pyramidal, deeply sulcate, about as long as the diameter of the outer +medullary shell, and two-thirds as broad at the base. + +_Dimensions._--Diameter of the disk 0.15, of the outer medullary shell +0.05, of the inner 0.02; length of the spines 0.05, basal breadth 0.03. + +_Habitat._--Central Pacific, Station 266, depth 2750 fathoms. + + + +{436}Subgenus 2. _Astrostaurus_, Haeckel, 1881, Prodromus, p. 457. + +_Definition._--Margin of the disk with a solid equatorial girdle, or a +corona of spines. + + +2. _Phacostaurus quadrigatus_, n. sp. + +Disk with smooth surface, four times as broad as the outer and ten times as +broad as the inner medullary shell. Pores irregular, roundish; fifteen to +sixteen on the diameter of the disk. Margin with a broad solid equatorial +girdle, from which arise four crossed spines, conical, as long as the +radius of the disk. + +_Dimensions._--Diameter of the disk 0.2, of the outer medullary shell 0.05, +of the inner 0.02; length of the spines 0.1, basal breadth 0.03. + +_Habitat._--South Pacific, Station 300, depth 1375 fathoms. + + +3. _Phacostaurus magnificus_, n. sp. (Pl. 31, figs. 7, 8). + + _Astrostaurus magnificus_, Haeckel, 1881, Prodromus et Atlas (pl. xxxi. + figs.7, 8). + +Disk with smooth surface, three times as broad as the outer and nine times +as broad as the inner medullary shell. Pores regular, circular; thirteen to +fourteen on the diameter of the disk. Margin with a corona of fifty to +sixty conical spines of unequal length. Four spines of the cross very large +pyramidal, deeply sulcated, longer than the radius of the disk, and as +broad at the base as the radius of the medullary shell. + +_Dimensions._--Diameter of the disk 0.22, of the outer medullary shell +0.07, of the inner 0.025; length of the four spines 0.16, basal breadth +0.04. + +_Habitat._--Indian Ocean, Madagascar, Rabbe, surface. + + + +Genus 190. _Distriactis_,[229] n. gen. + +_Definition._--#Phacodiscida# with simple medullary shell and with six +radial spines on the margin of the disk placed in the equatorial plane. + +The genus _Distriactis_ exhibits on the margin of the lenticular phacoid +shell six radial solid spines. Their distance is commonly equal, rarely +unequal. Either all six spines are of equal size and similar form, or three +larger (perradial) alternating with three smaller (interradial), so that +_Distriactis_ appears to be derived from _Triactiscus_ by development of +three secondary between three primary spines. + + +1. _Distriactis liriantha_, n. sp. + +Disk smooth, four times as broad as the medullary shell, with regular, +circular pores (about ten on the radius). Six marginal spines of equal size +and at equal distances, triangular, sulcate, half as long as the radius. +(Similar to _Heliosestrum medusinum_, Pl. 34, fig. 6.) + +{437}_Dimensions._--Diameter of the disk 0.2, of the medullary shell 0.05; +length of the spines 0.05, basal breadth 0.04. + +_Habitat._--Central Pacific, Station 265, depth 2900 fathoms. + + +2. _Distriactis corallantha_, n. sp. + +Disk thorny, three times as broad as the medullary shell, with regular, +circular pores, about eight on the radius. Six marginal spines of equal +size and equidistant, conical, nearly as long as the diameter of the disk, +half as broad at the base as the medullary shell. + +_Dimensions._--Diameter of the disk 0.12, of the medullary shell 0.04; +length of the spines 0.1, breadth 0.02. + +_Habitat._--South Pacific, Station 300, surface. + + +3. _Distriactis alterna_, n. sp. + +Disk smooth, five times as broad as the medullary shell, about twelve pores +on the radius. Six marginal spines pyramidal, at equal distances, but +unequal alternating size; three larger (perradial) spines as long as the +shell radius, three smaller between them (interradial) half as long and +broad. + +_Dimensions._--Diameter of the disk 0.15, of the medullary shell 0.03; +length of the three major spines 0.08, of the three minor 0.05. + +_Habitat._--North Atlantic, Station 353, surface. + + +4. _Distriactis palmantha_, n. sp. + +Disk rough, four times as broad as the medullary shell, about ten pores on +the radius. Six marginal spines conical, at equal distances, but unequal +alternating size; three larger (perradial) spines as long as the shell +diameter, three smaller between them (interradial) as long as the radius. + +_Dimensions._--Diameter of the disk 0.2, of the medullary shell 0.05; +length of the three major spines 0.2, of the three minor 0.1, + +_Habitat._--South Atlantic, Station 325, surface. + + +5. _Distriactis amphithecta_, n. sp. + +Disk thorny, three times as broad as the medullary shell. Six marginal +spines conical, of very different size; one single (anterior) much larger +than the five others, the opposite (posterior) much smaller. The other four +spines are paired, the anterior pair larger than the posterior. + +_Dimensions._--Diameter of the disk 0.15, of the medullary shell 0.05; +length of the longest spine 0.2, of the shortest 0.04, of the anterior pair +0.1, of the posterior 0.07. + +_Habitat._--Indian Ocean, Cocos Islands, surface, Rabbe. + + + +{438}Genus 191. _Heliosestrum_,[230] Haeckel, 1881, Prodromus, p. 457. + +_Definition._--#Phacodiscida# with simple medullary shell and with eight +radial spines on the margin of the disk (more or less regularly disposed, +sometimes seven or nine). + +The genus _Heliosestrum_ (with simple medullary shell) and the following +_Astrosestrum_ (with double medullary shell) contain those Phacodiscida in +which the margin of the lenticular disk bears eight radial spines, commonly +more or less regularly disposed in the equatorial plane, so that the equal +angles between them amount to 45d. There are, however, many exceptions to +this regular eight-rayed form, either the angles between the eight spines +becoming unequal or the number of the spines amounting to seven or nine +(sometimes also six or ten) in one and the same species. But the regular +form is as prevalent, and also in the abnormal forms indicated by the +position of the spines, that we separate the genus _Heliosestrum_ from +_Heliodiscus_. Both genera are rich in common species, and in some of the +former four perradial (larger) spines alternate regularly with four +interradial (smaller) spines. + + + +Subgenus 1. _Heliosestantha_, Haeckel. + +_Definition._--Surface of the disk smooth, without radial spines. Bases of +the marginal spines free, not connected by an equatorial girdle. + + +1. _Heliosestrum medusinum_, n. sp. (Pl. 34, fig. 6). + + _Heliodiscus medusinus_, Haeckel, 1881, Atlas (pl. xxxiv. fig. 6). + +Disk with smooth surface, four times as broad as the medullary shell. Pores +regular, circular; about ten on the radius of the disk. Eight marginal +spines regularly distributed (sometimes seven or nine, more or less +irregular), angular, nearly pyramidal (with equilateral triangular +outline), about as long and broad as the diameter of the medullary shell, +without connecting equatorial girdle. From the broad base of each spine run +eight to ten deep furrows convergent to its apex. + +_Dimensions._--Diameter of the disk 0.2, of the medullary shell 0.05; +length of the radial spines 0.05, basal breadth 0.05. + +_Habitat._--North Pacific, Station 266, surface. + + +2. _Heliosestrum octastrum_, n. sp. + +Disk with smooth surface, three times as broad as the medullary shell. +Pores irregular, roundish; eight to nine on the radius. Eight marginal +spines regularly distributed (sometimes {439}seven or nine, more or less +irregular), conical, about as long as the diameter of the disk, without a +connecting equatorial girdle. + +_Dimensions._--Diameter of the disk 0.15, of the medullary shell 0.05; +length of the radial spines 0.16, basal breadth 0.01. + +_Habitat._--Pacific, central area, Station 271, depth 2425 fathoms. + + +3. _Heliosestrum solarium_, Haeckel. + + _Haliomma sol_ (_partim_), Ehrenberg, 1875 (_non_ 1844), Abhandl. d. k. + Akad. d. Wiss. Berlin, p. 74, Taf. xxviii. fig. 1. + +Surface of the disk smooth; its diameter six times as large as that of the +medullary shell. Pores regular, circular; nine to ten on the radius. Eight +marginal spines regularly distributed (sometimes seven or nine, more or +less irregular), conical, about as long as the diameter of the medullary +shell, without a connecting equatorial girdle. + +_Dimensions._--Diameter of the disk 0.18, of the medullary shell 0.03; +length of the radial spines 0.03, basal breadth 0.01. + +_Habitat._--Fossil in the Tertiary rocks of Barbados. + + +4. _Heliosestrum liriope_, n. sp. + +Surface of the disk smooth; its diameter four times as large as that of the +medullary shell. Pores subregular, circular; seven to eight on the radius. +Eight marginal spines regularly distributed, conical, compressed, +alternating longer and shorter; the longer equal to the diameter of the +disk, the shorter to the radius. + +_Dimensions._--Diameter of the disk 0.16, of the medullary shell 0.4; +length of the major radial spines 0.15, of the minor 0.09. + +_Habitat._--North Pacific, Station 236, surface. + + +5. _Heliosestrum quadrigeminum_, n. sp. + +Surface of the disk smooth; its diameter four times as large as that of the +medullary shell. Pores irregular, roundish; six to seven on the radius. +Eight marginal spines triangular, flat, regularly disposed, alternating +longer and shorter, the major as long as the radius of the shell, and half +as broad at the base, with three to four deep furrows on both sides, +without a connecting equatorial girdle. + +_Dimensions._--Diameter of the disk 0.16, of the medullary shell 0.04; +length of the larger radial spines 0.08, of the smaller 0.04, basal breadth +0.04. + +_Habitat._--Pacific, central area, Station 266, depth 2750 fathoms. + + +6. _Heliosestrum contiguum_, Haeckel. + + _Haliomma contiguum_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. + Berlin, p. 74, Taf. xxvii. fig. 5. + +Disk with smooth surface, four times as broad as the medullary shell. +Pores irregular, roundish, touching, with very thin bars; nine to ten on +the radius. Eight marginal spines (often {440}seven or nine) conical, half +as long as the radius, twice as long as broad, without a connecting +equatorial girdle. + +_Dimensions._--Diameter of the disk 0.17, of the medullary shell 0.04; +length of the radial spines 0.04, basal breadth 0.02. + +_Habitat._--Fossil in Barbados. + + +7. _Heliosestrum irregulare_, n. sp. + +Disk with smooth surface, four times as broad as the medullary shell. Pores +irregular, roundish; nine to eleven on the radius. Eight conical radial +spines of irregular size and distribution, often seven or nine, about as +long as the radius of the disk (in some cases longer, in others shorter). +No connecting equatorial girdle. + +_Dimensions._--Diameter of the disk 0.2, of the medullary shell 0.05; +length of the radial spines 0.1, basal breadth 0.02. + +_Habitat._--Central Pacific, Stations 270 to 272, depth 2425 to 2925 +fathoms. + + + +Subgenus 2. _Heliosestilla_, Haeckel. + +_Definition._--Surface of the disk armed with radial spines. Bases of the +marginal spines free, without a connecting equatorial girdle. + + +8. _Heliosestrum octonum_, n. sp. (Pl. 34, fig. 3). + +Disk with spiny surface, three times as broad as the medullary shell. Pores +circular, of very different sizes; eight to ten on the radius. Eight +conical marginal spines of equal size and equidistant, as long as the +radius of the disk, and one-third as broad at the base as the medullary +shell. Numerous spines on the surface bristle-shaped, on the margin half as +long as the eight main spines, in the central part shorter. + +_Dimensions._--Diameter of the disk 0.18, of the medullary shell 0.06; +length of the marginal spines 0.1, basal breadth 0.02. + +_Habitat._--Central Pacific, Station 271, surface. + + +9. _Heliosestrum aegineta_, n. sp. + +Disk with spiny surface, four times as broad as the medullary shell. Pores +irregular, roundish, of different sizes; twelve to fourteen on the radius. +Eight pyramidal marginal spines regularly disposed, four larger (perradial) +alternating with four smaller (interradial); the former as long as the +radius of the disk, the latter half as long. + +_Dimensions._--Diameter of the disk 0.2, of the medullary shell 0.05; +length of the marginal spines 0.05 to 0.1, basal breadth 0.03. + +_Habitat._--South Atlantic, Station 330, surface. + + + +{441}Subgenus 3. _Heliosestomma_, Haeckel. + +_Definition._--Surface of the disk smooth, without radial spines. Bases of +the marginal spines connected by a solid equatorial girdle. + + +10. _Heliosestrum octangulum_, n. sp. + +Disk with smooth surface, octagonal, twice as broad as the medullary shell. +Pores regular, circular; nine to ten on the radius. Equatorial girdle +narrow, radially striped, connecting the points of the eight short, +regularly disposed, marginal spines in such a manner that the whole shell +forms a regular octagon with rectilinear sides. + +_Dimensions._--Diameter of the disk 0.11 to 0.12, of the medullary shell +0.05 to 0.06; length of the sides of the octagon 0.06. + +_Habitat._--Central Pacific, Station 268, depth 2900 fathoms. + + +11. _Heliosestrum octogonium_, n. sp. + +Disk with smooth surface, octagonal, four times as broad as the medullary +shell. Pores irregular, roundish; eight to nine on the radius. Equatorial +girdle broad, smooth, connecting the points of the eight short, triangular, +flat marginal spines in such a manner that the whole shell forms a +subregular octagon with concave, nearly equal sides. (Sometimes seven or +nine spines instead of eight are developed.) + +_Dimensions._--Diameter of the disk 0.16 to 0.18, of the medullary shell +0.04 to 0.05; length of the radial spines 0.02 to 0.04, basal breadth 0.03. + +_Habitat._--Central Pacific, Station 266, depth 2750 fathoms. + + +12. _Heliosestrum craspedotum_, n. sp. + + _Haliomma humboldti_, var., Bury, 1862, Polycystins of Barbados, pl. + viii. fig. 4 (below). + +Disk with smooth surface, three times as broad as the medullary shell. +Pores subregular, circular; ten to twelve on the radius. Eight marginal +spines (sometimes seven or nine) triangular, deeply sulcated, half as long +and one-third as broad as the radius of the disk, connected by a narrow, +radially striped equatorial girdle. + +_Dimensions._--Diameter of the disk 0.18, of the medullary shell 0.06; +length of the radial spines 0.05, basal breadth 0.03. + +_Habitat._--Central Pacific, Stations 271 to 274, at various depths, also +fossil in Barbados. + + + +Genus 192. _Astrosestrum_,[231] Haeckel, 1881, Prodromus, p. 457. + +_Definition._--#Phacodiscida# with double medullary shell and with eight +radial spines on the margin of the disk (more or less regularly disposed, +sometimes seven or nine). + +{442}The genus _Astrosestrum_ differs from the foregoing _Heliosestrum_ by +the duplication of the medullary shell. The eight marginal spines in the +majority of individuals are regularly formed and disposed, of equal size +and equidistant. But there are frequent exceptions to this rule, either the +angles between the eight spines being more or less different, or the number +amounting to seven or nine, instead of eight. Here also in some species +four larger (perradial) spines alternate regularly with four smaller +(interradial spines), after the same law of symmetry, which is common in +the Medusae. + + + +Subgenus 1. _Astrosestantha_, Haeckel. + +_Definition._--Surface of the disk smooth, without radial spines. Bases of +the marginal spines free, not connected by an equatorial girdle. + + +1. _Astrosestrum ephyra_, n. sp. (Pl. 32, figs. 4, 4_a_). + +Disk with smooth surface, three times as broad as the outer and nine times +as broad as the inner medullary shell. Pores subregular, circular; seven to +eight on the radius of the disk. Eight marginal spines (sometimes seven or +nine) more or less irregularly disposed, of variable size, commonly as long +as the radius of the disk, twice as long as broad, pyramidal, sulcate, +without a connecting equatorial girdle. + +_Dimensions._--Diameter of the disk 0.12, of outer medullary shell 0.04, of +the inner 0.014; length of the marginal spines 0.05 to 0.07, basal breadth +0.03. + +_Habitat._--Central Pacific, Stations 270 to 274, depths 2350 to 2925 +fathoms. + + +2. _Astrosestrum nauphanta_, n. sp. (Pl. 32, fig. 5). + +Disk with smooth surface, two and a half times as broad as the outer and +five times as broad as the inner medullary shell. Pores regular, circular; +eight to nine on the radius of the disk. Eight marginal spines (often seven +or nine) more or less regularly disposed, of equal size, half as long as +the radius of the disk, and quite as broad at the base, compressed +triangular, sulcate, without a connecting equatorial girdle. + +_Dimensions._--Diameter of the disk 0.15, of the outer medullary shell +0.06, of the inner 0.03; length of the marginal spines 0.04, basal breadth +0.04. + +_Habitat._--Pacific, central area, Stations 266 to 268, depth 2700 to 2900 +fathoms. + + +3. _Astrosestrum octacanthum_, Haeckel. + + _Haliomma octacanthum_, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. + Berlin, p. 295, Taf. viii. fig. 11. + +Disk with smooth surface, twice as broad as the outer and six times as +broad as the inner medullary shell. Pores regular, circular; six to seven +on the radius of the disk. Eight marginal spines {443}regularly disposed, +of variable size, the longest as long as the radius, pyramidal, not broader +at the base than one pore, without a connecting equatorial girdle. + +_Dimensions._--Diameter of the disk 0.12, of the outer medullary shell +0.06, inner 0.02; length of the marginal spines 0.03 to 0.06, basal breadth +0.01. + +_Habitat._--Western Pacific, Philippine Sea, 3300 fathoms, Ehrenberg; +Station 225, depth 4475 fathoms. + + +4. _Astrosestrum acraspedum_, n. sp. + +Disk with smooth surface, three times as broad as the outer and six times +as broad as the inner medullary shell. Pores regular, circular; nine to ten +on the radius of the disk. Eight marginal spines regularly disposed, of +alternating size; four major (perradial) spines as long as the diameter of +the disk, four minor (interradial) half as long; spines cylindrical, not +broader at the base than one pore, without a connecting equatorial girdle. + +_Dimensions._--Diameter of the disk 0.2, of the outer medullary shell 0.07, +of the inner 0.035; length of the larger spines 0.2, of the smaller 0.1, +basal breadth 0.01. + +_Habitat._--South Atlantic, Station 332, depth 2200 fathoms. + + + +Subgenus 2. _Astrosestilla_, Haeckel. + +_Definition._--Surface of the disk covered with radial spines. Bases of the +marginal spines free, not connected by an equatorial girdle. + + +5. _Astrosestrum acanthastrum_, n. sp. + +Disk with spiny surface, three times as broad as the outer and nine times +as broad as the inner medullary shell. Pores subregular, circular; ten to +eleven on the radius. Eight marginal spines (sometimes seven or nine) +regularly disposed, triangular, about half as long as the radius of the +disk, and one-third as broad at the base, without a connecting equatorial +girdle. + +_Dimensions._--Diameter of the disk 0.18, of the outer medullary shell +0.06, of the inner 0.02; length of the radial spines 0.05, basal breadth +0.03. + +_Habitat._--North Atlantic, Gulf Stream, Faeroee Channel, surface, John +Murray. + + +6. _Astrosestrum echinastrum_, n. sp. + +Disk with spiny surface, twice as broad as the outer and four times as +broad as the inner medullary shell. Pores irregular, roundish; eight to +nine on the radius. Eight marginal spines more or less regularly disposed, +pyramidal, nearly as long as the radius of the disk, and not broader at the +base than one large pore, without a connecting equatorial girdle. + +_Dimensions._--Diameter of the disk 0.15, of the outer medullary shell +0.07, of the inner 0.04; length of the radial spines 0.07, basal breadth +0.01. + +_Habitat._--Fossil in the Tertiary rocks of Sicily, Caltanisetta, Teuscher. + + + +{444}Subgenus 3. _Astrosestomma_, Haeckel. + +_Definition._--Surface of the disk smooth, without radial spines. Bases of +the marginal spines connected by a solid equatorial girdle. + + +7. _Astrosestrum pelagia_, n. sp. + +Disk with smooth surface, three times as broad as the outer and eight times +as broad as the inner medullary shell. Pores regular, circular; eight to +nine on the radius. Eight marginal spines conical, about as long as the +radius of the disk, of nearly equal length, one-third as broad at the base, +connected by a radially striped equatorial girdle. + +_Dimensions._--Diameter of the disk 0.18, of the outer medullary shell +0.06, of the inner 0.023; length of the radial spines 0.09, basal breadth +0.03. + +_Habitat._--Indian Ocean, Ceylon, Haeckel, surface. + + +8. _Astrosestrum floscula_, n. sp. + +Disk with smooth surface, two and a half times as broad as the outer and +five times as broad as the inner medullary shell. Pores irregular, +roundish; ten to eleven on the radius. Eight marginal spines triangular, +plain, scarcely half as long as the radius of the disk, nearly as broad at +the base, connected by an even equatorial girdle. + +_Dimensions._--Diameter of the disk 0.2, of the outer medullary shell 0.08, +of the inner 0.04; length of the radial spines 0.09, basal breadth 0.07. + +_Habitat._--South Atlantic, Station 325, surface. + + + +Subfamily 3. HELIODISCIDA, Haeckel, 1881, Prodromus, p. 457. + +_Definition._--#Phacodiscida# with a variable number of radial spines on +the margin of the disk (ten to twenty or more), which are commonly more or +less irregular (sometimes regularly formed and disposed). + + + +Genus 193. _Heliodiscus_,[232] Haeckel, 1862, Monogr. d. Radiol., p. 436. + +_Definition._--#Phacodiscida# with simple medullary shell and with numerous +(ten to twenty or more) simple radial spines on the margin of the disk +(commonly with a variable number and an irregular disposition of the +undivided spines). + +The genus _Heliodiscus_, the most common and polymorphic of all +#Phacodiscida#, was founded by me in 1862 as the first known type of this +family (_loc. cit._). I use {445}here the diagnosis of this genus in a +restricted sense, including only the species, in which the number of +marginal spines amounts to ten, twenty, or more (sometimes fifty to eighty, +rarely more than one hundred). The number of spines is in the different +species variable, and their disposition commonly more or less irregular, +whilst in the preceding genera (with two, three, four, six, or eight +marginal spines) their distance and form are commonly regular. + + + +Subgenus 1. _Heliodiscetta_, Haeckel. + +_Definition._--Surface of the disk smooth, without radial spines. Bases of +the marginal spines free, without a connecting equatorial girdle. + + +1. _Heliodiscus asteriscus_, n. sp. (Pl. 33, fig. 8). + +Disk with smooth surface, three times as broad as the medullary shell. +Pores regular, circular; ten to twelve on the radius of the disk. Marginal +spines fifteen to twenty, conical, often double contoured, of variable size +and disposition, the largest as long as the radius of the disk, as broad at +the base as one pore. + +_Dimensions._--Diameter of the disk 0.15, of the medullary shell 0.05; +length of the radial spines 0.04 to 0.07, basal breadth 0.01. + +_Habitat._--Cosmopolitan; Mediterranean (Corfu), Indian Ocean (Madagascar), +Atlantic and Pacific, many Stations, surface and various depths. + + +2. _Heliodiscus trochiscus_, n. sp. (Pl. 34, figs. 10, 13). + +Disk with smooth surface, four times as broad as the medullary shell. Pores +regular, circular; fourteen to sixteen on the radius. Marginal spines +twelve to sixteen, conical, of variable size and disposition, the largest +as long as the diameter of the medullary shell, twice as broad as one pore. + +_Dimensions._--Diameter of the disk 0.2, of the medullary shell 0.05; +length of the radial spines 0.01 to 0.025, basal breadth 0.005. + +_Habitat._--Central Pacific, Stations 272 to 274, surface. + + +3. _Heliodiscus trigonodon_, n. sp. + +Disk with smooth surface, four times as broad as the medullary shell. Pores +regular, circular; eighteen to twenty on the radius. Marginal spines +sixteen to twenty, equilateral triangular, flat, smooth, about as long and +broad as the radius of the medullary shell. + +_Dimensions._--Diameter of the disk 0.2, of the medullary shell 0.05; +length of the radial spines 0.03, basal breadth 0.03. + +_Habitat._--Central Pacific, Stations 266 to 274, depths 2350 to 2925 +fathoms. + + +{446}4. _Heliodiscus glyphodon_, n. sp. (Pl. 35, fig. 2). + + _Heliosestrum glyphodon_, Haeckel, 1881, Prodromus et Atlas (pl. xxxv. + fig. 2). + +Disk with smooth surface, four times as broad as the medullary shell. Pores +subregular, circular; seven to eight on the radius. Marginal spines ten to +twelve, equilateral triangular, flat, deeply furrowed, twice as long as +broad, and as long as the radius of the disk. + +_Dimensions._--Diameter of the disk 0.14, of the medullary shell 0.035; +length of the radial spines 0.07, basal breadth 0.035. + +_Habitat._--North Pacific, Station 253, depth 3125 fathoms. + + +5. _Heliodiscus helianthus_, Haeckel. + + _Haliomma helianthus_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. + Berlin, p. 74, Taf. xxvii. fig. 1. + +Disk with smooth surface, five times as broad as the medullary shell. Pores +regular, oblong, disposed regularly in sixty to eighty radial series; +fourteen to sixteen on the radius. Marginal spines sixty to eighty, +conical, about as long as the diameter of the medullary shell, twice as +broad as one pore. + +_Dimensions._--Diameter of the disk 0.2, of the medullary shell 0.04; +length of the radial spines 0.04, basal breadth 0.005. + +_Habitat._--Fossil in Barbados. + + +6. _Heliodiscus sol_, Haeckel. + + _Haliomma sol_, Ehrenberg, 1854, Mikrogeol., Taf. xix. fig. 52. + + _Heliodiscus sol_, Haeckel, 1862, Monogr. d. Radiol., p. 438. + +Disk with smooth surface, four times as broad as the medullary shell. Pores +irregular, roundish; eight to ten on the radius. Marginal spines twenty to +thirty, conical, the largest as long as the radius of the medullary shell, +their bases widely distant. (The species from Barbados figured by +Ehrenberg, 1875, as _Haliomma sol_, appertains to _Heliosestrum solare_.) + +_Dimensions._--Diameter of the disk 0.2, of the medullary shell 0.05; +length of the radial spines 0.02 to 0.025, basal breadth 0.01. + +_Habitat._--Fossil in Tertiary rocks of Greece (Aegina), Ehrenberg. + + +7 _Heliodiscus siculus_, Stoehr. + + _Heliodiscus siculus_, Stoehr, 1880, Palaeontogr., vol. xxvi. p. 89, Taf. + i. fig. 14. + +Disk with smooth surface, three times as broad as the medullary shell. +Pores irregular roundish; seven to eight on the radius. Marginal spines +forty to fifty, conical, very irregular, the largest as long as the radius +of the medullary shell, their bases coming in contact. + +_Dimensions._--Diameter of the disk 0.13 to 0.15, of the medullary shell +0.04 to 0.05; length of the radial spines 0.02 to 0.03, basal breadth 0.002 +to 0.006. + +_Habitat._--Fossil in Tertiary rocks of Sicily, Grotte (Stoehr), +Caltanisetta (Teuscher). + + +{447}8. _Heliodiscus polymorphus_, n. sp. (Pl. 34, figs. 11, 12). + +Disk with smooth surface, four times as broad as the medullary shell. Pores +irregular, roundish; ten to twelve on the radius. Marginal spines ten to +fifteen, pyramidal, angular, very irregular and variable in size and +distribution, the largest nearly as long as the diameter of the disk, as +broad at the base as the radius of the medullary shell. + +_Dimensions._--Diameter of the disk 0.15 to 0.2, of the medullary shell +0.04 to 0.05; length of the radial spines 0.06 to 0.18, basal breadth 0.02 +to 0.03. + +_Habitat._--Central Pacific, Stations 265 to 268, depths 2700 to 2900 +fathoms. + + +9. _Heliodiscus solaster_, n. sp. (Pl. 34, fig. 4). + +Disk with smooth surface, three times as broad as the medullary shell. +Pores subregular, roundish; nine to ten on the radius. Marginal spines +fifty to sixty, cylindro-conical, flexuose, very variable in size, the +largest nearly as long as the diameter of the disk. The spines lie not only +in the equatorial plane (as usual), but also in two to four crowded girdles +on both sides of it. + +_Dimensions._--Diameter of the disk 0.15, of the medullary shell 0.05; +length of the radial spines 0.05 to 0.15, basal breadth 0.008. + +_Habitat._--Indian Ocean, Madagascar, Rabbe, surface. + + + +Subgenus 2. _Heliodiscilla_, Haeckel. + +_Definition._--Surface of the disk covered with radial spines. Bases of +the marginal spines free, without a connecting equatorial girdle. + + +10. _Heliodiscus phacodiscus_, Haeckel. + + _Heliodiscus phacodiscus_, Haeckel, 1862, Monogr. d. Radiol., p. 437, + Taf. xvii. figs. 5-7. + + _Haliomma phacodiscus_, Haeckel, 1860, Monatsber. d. k. preuss. Akad. d. + Wiss. Berlin, p. 815. + +Disk with spiny surface, three times as broad as the medullary shell. Pores +regular, circular; six to eight on the radius. Marginal spines twelve to +sixteen, conical, as long as the radius of the disk, and one-third as broad +as the diameter of the medullary shell. + +_Dimensions._--Diameter of the disk 0.12 to 0.16, of the medullary shell +0.04 to 0.05; length of the marginal spines 0.06 to 0.08, basal breadth +0.01 to 0.02. + +_Habitat._--Mediterranean (Messina), Canary Islands (Lanzerote). + + +11. _Heliodiscus amphidiscus_, Haeckel. + + _Heliodiscus amphidiscus_, Haeckel, 1862, Monogr. d. Radiol., p. 437. + + _Haliomma amphidiscus_, J. Mueller, 1858, Abhandl. d. k. Akad. d. Wiss. + Berlin, p. 154, Taf. ii. figs. 3-7. + +Disk with spiny surface, three times as broad as the medullary shell. +Pores regular, circular; eight to ten on the radius. Marginal spines twelve +to fifteen, bristle-shaped, not larger than the surface spines, about as +long as the radius of the medullary shell. + +{448}_Dimensions._--Diameter of the disk 0.16, of the medullary shell 0.05; +length of the marginal spines 0.03, basal breadth 0.002. + +_Habitat._--Mediterranean (south shore of France), J. Mueller. + + +12. _Heliodiscus echiniscus_, n. sp. (Pl. 34, fig. 5). + +Disk with spiny surface, three times as broad as the medullary shell. Pores +irregular, roundish or polygonal; eight to ten on the radius. Marginal +spines thirty to fifty, pyramidal, angular, of very variable size, number, +and disposition, gradually passing into the surface-spines; the largest +nearly as long as the diameter of the medullary shell. + +_Dimensions._--Diameter of the disk 0.14, of the medullary shell 0.045; +length of the radial spines 0.02 to 0.04, basal breadth 0.006. + +_Habitat._--Central Pacific, Station 272, depth 2600 fathoms. + + +13. _Heliodiscus pertusus_, n. sp. (Pl. 35, fig. 1). + + _Heliosestrum pertusum_, Haeckel, 1881, Prodromus et Atlas (pl. xxxv. + fig. 1). + +Disk with spiny surface, three times as broad as the medullary shell. Pores +irregular, circular, hexagonally framed; eight to ten on the radius. +Marginal spines ten to thirty, very variable in size and disposition; +commonly eight to twelve larger spines, which are pyramidal, about as long +as the radius of the disk and perforated by two to four irregular, longish +pores. Between these fenestrated large spines are commonly ten to twenty +smaller conical spines, gradually passing into those of the surface. + +_Dimensions._--Diameter of the disk 0.13 to 0.16, of the medullary shell +0.04 to 0.05; length of the marginal spines 0.04 to 0.08, basal breadth +0.01 to 0.015. + +_Habitat._--North Pacific, Stations 241 to 244, depths 2300 to 2900 +fathoms. + + + +Subgenus 3. _Heliodiscomma_, Haeckel. + +_Definition._--Surface of the disk smooth, without radial spines. Bases of +the marginal spines connected by a solid equatorial girdle. + + +14. _Heliodiscus cingillum_, n. sp. (Pl. 33, fig. 7). + +Disk with smooth surface, five times as broad as the medullary shell. Pores +regular, circular; twelve to fourteen on the radius. Equatorial girdle +about as broad as the medullary shell, in the proximal half radially +striped, on the margin with twenty to twenty-four short, flat, triangular +spines, which are shorter than the breadth of the girdle. + +_Dimensions._--Diameter of the disk 0.25, of the medullary shell 0.05; +length of the marginal spines 0.02, basal breadth 0.02. + +_Habitat._--Central Pacific, Station 274, depth 2750 fathoms. + + +{449}15. _Heliodiscus humboldti_, Haeckel. + + _Heliodiscus humboldti_, Haeckel, 1862, Monogr. d. Radiol., p. 438. + + _Haliomma humboldti_, Ehrenberg, 1854, Mikrogeol., Taf. xxxvi. fig. 27; + Abhandl. d. k. Akad. d. Wiss. Berlin, 1875, Taf. xxvii. fig. 3. + + _Haliomma humboldti_, Bury, 1862, Polycystins of Barbados, pl. viii. fig. + 3 (at left). + +Disk with smooth surface, four times as broad as the medullary shell. Pores +regular, circular; eighteen to twenty on the radius. Equatorial girdle half +as broad as the medullary shell, in the proximal half radially striped, on +the margin with sixteen to twenty short, flat, triangular teeth, which are +longer than the breadth of the girdle. + +_Dimensions._--Diameter of the disk 0.12 to 0.2, of the medullary shell +0.03 to 0.05; length of the marginal spines 0.02 to 0.04, basal breadth +0.02. + +_Habitat._--Fossil in Barbados (common and very variable). + + +16. _Heliodiscus marginatus_, n. sp. (Pl. 34, fig. 9). + +Disk with smooth surface, three times as broad as the medullary shell. +Pores regular, circular; nine to ten on the radius. Equatorial girdle +one-fourth to one-half as broad as the medullary shell, in the whole +breadth radially striped, on the margin with twelve to eighteen very short +and broad, triangular, marginal spines. + +_Dimensions._--Diameter of the disk 0.15 to 0.2, of the medullary shell +0.05 to 0.06; length of the marginal spines 0.01 to 0.02, basal breadth +0.02. + +_Habitat._--Central Pacific, Stations 265 to 268, depth 2900 fathoms. + + +17. _Heliodiscus sulcatus_, n. sp. + +Disk with smooth surface, four times as broad as the medullary shell. Pores +subregular, circular; twelve to fifteen on the radius. Equatorial girdle as +broad as the medullary shell, in the whole breadth radially striped on the +margin with ten to fifteen triangular, deeply sulcated teeth, about as long +and broad as the medullary shell. (Similar to _Heliodiscus glyphodon_, Pl. +35, fig. 2, but with broad sulcated girdle and shorter, more numerous +spines.) + +_Dimensions._--Diameter of the disk 0.15 to 0.2, of the medullary shell +0.04 to 0.05; length of the radial spines 0.05 to 0.06, basal breadth 0.04 +to 0.05. + +_Habitat._--Atlantic and Pacific, tropical part, many Stations, surface. + + +18. _Heliodiscus umbonatus_, Haeckel. + + _Haliomma umbonatum_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. + Berlin, p. 74, Taf. xxvii. fig. 4. + +Disk with smooth surface, three times as broad as the medullary shell. +Pores irregular, roundish; eight to ten on the radius. Equatorial girdle +half as broad as the medullary shell, hyaline, not radially striped, on the +margin with ten to twenty triangular, irregular, smooth teeth, very +variable in size and disposition. + +{450}_Dimensions._--Diameter of the disk 0.15 to 0.2, of the medullary +shell 0.05 to 0.06; length of the marginal spines 0.02 to 0.08, basal +breadth 0.01 to 0.03. + +_Habitat._--Cosmopolitan; Atlantic, Pacific, in various depths; also fossil +in Barbados and Sicily. + + + +Subgenus 4. _Heliodiscura_, Haeckel. + +_Definition._--Surface of the disk covered with radial spines. Bases of the +marginal spines connected by a solid equatorial girdle. + + +19. _Heliodiscus apollinis_, n. sp. + +Disk with spiny or bristly surface, three times as broad as the medullary +shell. Pores regular, circular; eleven to twelve on the radius. Equatorial +girdle narrow, on the margin with sixteen to twenty broad, flat, triangular +teeth, which are half as long and one-fourth as broad as the medullary +shell. (Very similar to _Astrophacus apollinis_, Pl. 32, fig. 2, but with +simple medullary shell.) + +_Dimensions._--Diameter of the disk 0.18, of the medullary shell 0.06; +length of the marginal spines 0.03, basal breadth 0.015. + +_Habitat._--Mediterranean (Corfu), Haeckel, surface. + + +20. _Heliodiscus zoroaster_, n. sp. + +Disk with spiny surface, four times as broad as the medullary shell. Pores +subregular, circular; fourteen to sixteen on the radius. Equatorial girdle +broad, radially striped, on the margin with ten to twelve pyramidal, deeply +sulcated radial spines, which are nearly as long as the radius of the disk, +and one-fourth as broad at the base. + +_Dimensions._--Diameter of the disk 0.24, of the medullary shell 0.06; +length of the marginal spines 0.11, basal breadth 0.03. + +_Habitat._--Indian Ocean, between Aden and Ceylon, Haeckel, surface. + + + +Genus 194. _Heliodrymus_,[233] Haeckel, 1881, Prodromus, p. 457. + +_Definition._--#Phacodiscida# with simple medullary shell and with numerous +(ten to twenty or more) branched radial spines on the margin of the disk +(commonly with a variable number and an irregular disposition of the +ramified spines). + +The genus _Heliodrymus_ differs from the nearly allied _Heliodiscus_ by the +ramification of the marginal spines, a character hitherto observed in no +other genus of Phacodiscida. The branching is more or less irregular, +either a simple bifurcation or a repeated fissure; the spines and their +branches are commonly more or less flexuose. {451}We can distinguish two +subgenera: in _Heliocladus_ the surface of the disk is smooth, in +_Heliodendrum_ covered with bristle-shaped radial spines, which are either +simple or also branched, sometimes longer than the thick marginal spines. + + + +Subgenus 1. _Heliocladus_, Haeckel, 1881, Prodromus, p. 457. + +_Definition._--Surface of the disk smooth, without radial spines. + + +1. _Heliodrymus dendrocyclus_, n. sp. (Pl. 33, fig. 9). + + _Heliocladus dendrocyclus_, Haeckel, 1881, Prodromus et Atlas (pl. + xxxiii. fig. 9). + +Disk with smooth surface, three times as broad as the medullary shell. +Pores regular, circular, hexagonally framed; eight to nine on the radius. +Marginal spines sixteen to twenty, cylindrical, very strong, flexuose, +irregularly branched, nearly as long as the diameter of the disk. Between +these main spines, each of which bears two to six irregular branches, are +scattered on the margin numerous smaller simple spines. + +_Dimensions._--Diameter of the disk 0.16, of the medullary shell 0.05; +length of the main spines 0.1 to 0.14, breadth 0.01 to 0.02. + +_Habitat._--Central Pacific, Station 271, surface. + + +2. _Heliodrymus furcatus_, n. sp. + +Disk with smooth surface, four times as broad as the medullary shell. Pores +irregular, roundish; ten to twelve on the radius. Marginal spines twenty to +twenty-five, cylindrical, flexuose, forked, about as long as the radius of +the disk; fork-branches irregular, of unequal size. Some smaller simple +spines are scattered between the forked ones. + +_Dimensions._--Diameter of the disk 0.15, of the medullary shell 0.04; +length of the radial spines 0.07 to 0.09, breadth 0.01. + +_Habitat._--Central Pacific, Station 265, surface. + + +3. _Heliodrymus grottensis_, Haeckel. + + _Heliodiscus grottensis_, Stoehr, 1880, Palaeontogr., vol. xxvi. p. 89, + Taf. i. fig. 13. + +Disk with smooth surface, two and a half times as broad as the medullary +shell. Pores irregular, roundish; eight to nine on the radius. Marginal +spines twenty to thirty, conical, very irregular in form, size, and +disposition; the smaller simple, the larger irregularly branched and half +as long as the radius of the disk. + +_Dimensions._--Diameter of the disk 0.17, of the medullary shell 0.07; +length of the marginal spines 0.02 to 0.04, basal breadth 0.01 to 0.02. + +_Habitat._--Fossil in Tertiary rocks of Sicily, Grotte, Stoehr. + + + +{452}Subgenus 2. _Heliodendrum_, Haeckel. + +_Definition._--Surface of the disk armed with simple or branched radial +spines. + + +4. _Heliodrymus setosus_, n. sp. + +Disk with spiny surface, four times as broad as the medullary shell. Pores +regular, circular; twelve to thirteen on the radius. Marginal spines ten to +twelve, cylindrical, irregularly branched, each with two to eight flexuose +branches of different sizes; the largest as long as the diameter of the +disk. Spines of the surface bristle-shaped, half as long, not branched. + +_Dimensions._--Diameter of the disk 0.2, of the medullary shell 0.05; +length of the marginal spines 0.12 to 0.18, breadth 0.025. + +_Habitat._--North Pacific, Station 254, surface. + + +5. _Heliodrymus ramosus_, n. sp. (Pl. 35, figs. 3, 4). + +Disk with spiny surface, three times as broad as the medullary shell. Pores +regular, circular, hexagonally framed; eleven to twelve on the radius. +Marginal spines sixteen to twenty, cylindrical, about as long as the +radius, irregularly forked or branched, with unequal flexuose branches. +Spines of the surface nearly as long, bristle-shaped, also irregularly +branched. + +_Dimensions._--Diameter of the disk 0.15, of the medullary shell 0.05; +length of the spines 0.06 to 0.08, basal breadth 0.01 to 0.015. + +_Habitat._--South Pacific, Station 288, surface. + + +6. _Heliodrymus viminalis_, n. sp. (Pl. 35, fig. 5). + +Disk with spiny surface, two and a half times as broad as the medullary +shell. Pores irregular, roundish; ten to twelve on the radius. Marginal +spines fifteen to twenty, cylindro-conical, strong, partly simple, partly +forked, about as long as the diameter of the disk. Spines of the surface +very numerous, bristle-shaped, longer than the marginal spines, and more +branched. + +_Dimensions._--Diameter of the disk 0.15, of the medullary shell 0.06; +length of the marginal spines 0.11 to 0.14, basal breadth 0.01 to 0.015; +length of the surface spines 0.2 to 0.03. + +_Habitat._--Central Pacific, Station 271, surface. + + + +Genus 195. _Astrophacus_,[234] Haeckel, 1881, Prodromus, p. 457. + +_Definition._--#Phacodiscida# with double medullary shell and with numerous +(ten to twenty or more) simple radial spines on the margin of the disk +(commonly with a variable number and an irregular disposition of the +undivided spines). + +The genus _Astrophacus_ differs from the similar _Heliodiscus_ in the +duplication of the medullary shell. The number and disposition of the +radial spines of the margin {453}(commonly between ten and twenty) is also +here variable in one and the same species. The greater number of observed +species of _Astrophacus_ resemble in a very remarkable manner the +corresponding species of _Heliodiscus_, and differ only in the double +medullary shell. + + + +Subgenus 1. _Astrophacetta_, Haeckel. + +_Definition._--Surface of the disk smooth, without radial spines. Bases of +the marginal spines free, without a connecting equatorial girdle. + + +1. _Astrophacus asteriscus_, n. sp. + +Disk with smooth surface, three times as broad as the outer and eight times +as broad as the inner medullary shell. Pores regular, circular; twelve to +fourteen on the radius. Marginal spines fifteen to twenty, of variable size +and disposition; the largest as long as the radius of the disk, as broad at +the base as one pore. (Very similar to _Heliodiscus asteriscus_, Pl. 33, +fig. 8, but differing in the double medullary shell.) + +_Dimensions._--Diameter of the disk 0.2, of the outer medullary shell 0.07, +of the inner 0.025; length of the marginal spines 0.05 to 0.1, basal +breadth 0.01. + +_Habitat._--Central Pacific, Station 265, depth 2900 fathoms. + + +2. _Astrophacus trochiscus_, n. sp. (Pl. 34, fig. 14). + +Disk with smooth surface, three times as broad as the outer and seven times +as broad as the inner medullary shell. Pores irregular, roundish; twelve to +thirteen on the radius. Marginal spines sixteen to twenty, conical, of +irregular variable size and disposition; the largest as long as the inner +medullary shell. (Differs from _Heliodiscus trochiscus_ in the double +medullary shell.) + +_Dimensions._--Diameter of the disk 0.22, of the outer medullary shell +0.08, of the inner 0.03. + +_Habitat._--North Atlantic, Station 354, surface. + + +3. _Astrophacus solaris_, n. sp. (Pl. 32, fig. 1). + +Disk with smooth surface, three times as broad as the outer and seven times +as broad as the inner medullary shell. Pores subregular, roundish; twelve +to fourteen on the radius. Marginal spines one hundred to one hundred and +twenty, conical, flexuose, of irregular size and form; the largest +one-third as long as the diameter of the disk. The spines lie not only in +the equatorial plane (as is usual) but also in two to four crowded girdles +on both sides of it. (Very similar to _Heliodiscus solaster_, Pl. 34, fig. +4, but of double the size, with double the number of spines and with a +double medullary shell.) + +_Dimensions._--Diameter of the disk 0.3, of the outer medullary shell 0.11, +of the inner 0.045; length of the spines 0.03 to 0.1, basal breadth 0.01 to +0.02. + +_Habitat._--Indian Ocean, Sunda Strait, Rabbe, surface. + + + +{454}Subgenus 2. _Astrophacilla_, Haeckel. + +_Definition._--Surface of the disk covered with radial spines. Bases of the +marginal spines free, without a connecting equatorial girdle. + + +4. _Astrophacus phacodiscus_, n. sp. (Pl. 32, fig. 3). + +Disk with spiny surface, two and a half times as broad as the outer and +seven times as broad as the inner medullary shell. Pores subregular, +circular; ten to twelve on the radius. Marginal spines twelve to sixteen, +conical, stout, nearly as long as the radius of the disk, and as broad at +the base as the inner medullary shell. The numerous bristle-shaped spines +of the surface are scarcely half as long. (Similar to _Heliodiscus +phacodiscus_, Haeckel, Monogr. d. Radiol., Taf. xvii. figs. 5-7, but +differing in the double medullary shell.) + +_Dimensions._--Diameter of the disk 0.18, of the outer medullary shell +0.07, of the inner 0.025; length of the marginal spines 0.08 to 0.09, basal +breadth 0.03. + +_Habitat._--South Pacific, Station 300, surface. + + + +Subgenus 3. _Astrophacomma_, Haeckel. + +_Definition._--Surface of the disk smooth, without radial spines. Bases of +the marginal spines connected by a solid equatorial girdle. (Perhaps = +_Chilomma_(?) Ehrenberg, 1847, Monatsber. d. k. preuss. Akad. d. Wiss. +Berlin, p. 54.) + + +5. _Astrophacus cingillum_, n. sp. + + _Haliomma humboldti_, var., Bury, 1862, Polycystins of Barbados, pl. + viii. fig. 3 (at right). + +Disk with smooth surface, three times as broad as the outer and eight times +as broad as the inner medullary shell. Pores regular, circular; eleven to +thirteen on the radius. Equatorial girdle about as broad as the inner +medullary shell, in the proximal half radially striped, on the margin with +eighteen to twenty-four short, flat, triangular spines, about as long as +the breadth of the girdle. (Similar to _Heliodiscus cingillum_, but with +double medullary shell.) + +_Dimensions._--Diameter of the disk 0.2, of the outer medullary shell 0.07, +of the inner 0.025; length of the spines 0.02, basal breadth 0.02. + +_Habitat._--Western Tropical Pacific, Station 225, depth 4475 fathoms; also +fossil in Barbados. + + +6. _Astrophacus saturnus_, Haeckel. + + ? _Chilomma saturnus_, Ehrenberg, 1861, Monatsber. d. k. preuss. Akad. d. + Wiss. Berlin, p. 297; 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 286, + Taf. ii. fig. 5. + + ? _Chilomma saturnus_, Haeckel, 1862, Monogr. d. Radiol., p. 447. + +Disk with smooth surface, two and a half times as broad as the outer, six +times as broad as the inner medullary shell. Pores large, irregular, +roundish; five to seven on the radius (?). Equatorial girdle very broad, +radially striped, nearly as broad as the outer medullary shell, perforated +by {455}twenty to thirty (or more?) radial spines. (The position of this +species, and the identity of _Chilomma_ with _Astrophacomma_, remains +doubtful, as the imperfect figure given by Ehrenberg of _Chilomma +saturnus_, the only species of the genus, is in contradiction with his +vague description, as is very often the case.) + +_Dimensions._--Diameter of the disk 0.12 (with girdle 0.22) of the outer +medullary shell 0.05, of the inner 0.02. + +_Habitat._--Arctic Ocean (Greenland, depth 1000 fathoms), Ehrenberg. + + + +Subgenus 4. _Astrophacura_, Haeckel. + +_Definition._--Surface of the disk covered with radial spines. Bases of the +marginal spines connected by a solid equatorial girdle. + + +7. _Astrophacus apollinis_, n. sp. (Pl. 32, fig. 2). + +Disk with spiny surface, three times as broad as the outer, eight times as +broad as the inner medullary shell. Pores regular, circular; eleven to +twelve on the radius of the disk. Equatorial girdle narrow, smooth, on the +margin with twelve to sixteen broad, flat, triangular spines, of the same +length as the numerous bristle-shaped spines of the surface, which reach +half the radius of the disk. (Very similar to _Heliodiscus apollinis_, but +differing in the double medullary shell.) + +_Dimensions._--Diameter of the disk 0.24, of the outer medullary shell +0.08, of the inner 0.03; length of the radial spines 0.06, basal breadth +0.03. + +_Habitat._--Western Tropical Pacific, Station 225, depth 4475 fathoms. + + + +Family XX. #COCCODISCIDA#, Haeckel (Pls. 36-38). + + _Coccodiscida_, Haeckel, 1862, Monogr. d. Radiol., p. 485. + _Coccodiscida_, Haeckel, 1881, Prodromus, p. 458. + _Lithocyclidina_, Ehrenberg, 1847, Monatsber. d. k. preuss. Akad. + d. Wiss. Berlin, p. 214 (_partim_). + +_Definition._--#Discoidea# with extracapsular phacoid shell (or lenticular +latticed cortical shell), connected by radial beams with an intracapsular, +simple or double, concentric medullary shell, and surrounded by one or more +concentric chambered equatorial girdles on the margin. + +The family #Coccodiscida# was founded by me in 1862 for those #Discoidea# +which agree with the Phacodiscida in the formation of the lenticular +"phacoid shell" (including a simple or double medullary shell), but differ +from them in the development of peculiar concentric chambered rings or +girdles around the equatorial margin of the disk, similar to those of the +Porodiscida. + +The Coccodiscida represent a polymorphic family, in which we here +distinguish sixteen genera with fifty-seven species; it comprises the +greater part of those {456}#Discoidea# which Ehrenberg united in his group +Lithocyclidina (1875, represented by four genera and eight species); +several of these, however, appertain to quite different families, as his +_Astromma entomocora_, _Lithocyclia amphitrites_, &c. His knowledge of the +structure was very imperfect. The peculiar differentiation of the genera +and species exhibits the greatest analogy to that of the following family, +Porodiscida, though the structure of the central disk in both families is +quite different. + +_The Phacoid Shell_, or the circular, lenticular cortical shell exhibits in +the Coccodiscida quite the same structure and composition as in the +Phacodiscida, described above (p. 420), so that there can be no doubt as to +the phylogenetic origin of the former from the latter. Quite in the same +way in both families, the lenticular "phacoid shell" is connected by +numerous, short, radial beams with the intracapsular, simple or double, +medullary shell; and also here these beams are commonly disposed in two +groups around the poles of the shortened main axis of the lens, so that +their distal ends are implanted in both circumpolar areas (Pl. 36, figs. +2-6; Pl. 37, figs. 3, 7; Pl. 38, figs. 2, 7). The medullary shell is +commonly simple, spherical, sometimes a little lenticularly compressed; +more rarely it is double, composed of two concentric lattice-shells, which +are connected by radial beams; in this case either both concentric +medullary shells are spherical, or the inner is spherical, and the outer +lenticular, very rarely the inner is lenticular also. In average size and +structure they agree perfectly with those of the Phacodiscida. + +_The Chamber Girdles_ or "chambered rings" around the equatorial margin of +the disk, which constitute the only difference between the Coccodiscida and +the Phacodiscida, seem to exhibit a considerable degree of difference of +structure in the numerous species of this family; but I regret that I +cannot explain them here satisfactorily. The study of these structures is +extremely difficult because of the thickness and darkness of the massive +opaque shells; to get a perfect knowledge of them, it is indispensable to +compare slides made in different directions (horizontal slides through the +equatorial and parallel planes, vertical slides through radial and parallel +planes, oblique slides in different directions). But this requires a long +time and a most careful study of the slides, which are very difficult to +get in satisfactory condition. Therefore the following remarks can have +only a provisional value. + +In all Coccodiscida we can distinguish on the equatorial chamber-girdle of +the lens-margin (even on superficial inspection) three different elements +of structure, viz.:--(A) concentric circular rings in the equatorial plane; +(B) numerous radial beams piercing the former and dividing them into +imperfect chambers; (C) porous plates or sieve-plates on both convex faces +of the disk. The probable morphological significance of these three +elements is the following:--Each ring or girdle corresponds to an outer +lenticular cortical shell, which is only developed on the marginal part, +whilst its central part is represented by the phacoid shell. Therefore the +radial beams (separating the imperfect chambers) are the same as in the +concentric Polysphaerida, and the {457}sieve-plates of the surface are the +porous walls of the cortical shell itself. The correctness of this +explanation seems to be proved by such forms as figured in Pl. 38, figs. 2, +4, where the whole surface of the phacoid shell is covered by a concentric +chamber-work, as a central continuation of the marginal concentric rings. +If we imagine a system of perfect concentric lenticular phacoid shells, +compressed strongly from both poles of the shortened main axis, we get the +same figure. + +Rarely one single girdle only is developed on the equatorial margin of the +lenticular disk (Pl. 37, figs. 2, 3, 5). Commonly the number of concentric +girdles amounts to three to six, often to ten to twelve or more. Some of +these largest Coccodiscida reach a considerable size. Commonly all girdles +are of the same breadth, which is about equal to the radius or to the +diameter of the inner medullary shell. Rarely the first (or innermost) +girdle differs by its greater breadth from the succeeding ones (Pl. 36, +fig. 8). + +Only in few Coccodiscida the girdle-building remains restricted to the +equatorial planes, so that all the chambers lie in it. Commonly on both +sides of this plane become developed several layers, and often the number +of these (three to six or more) increases towards the periphery; in other +cases not their number, but their height increases. Therefore very often +the margin of the discoidal shell is much thickened, as thick as the centre +of the lenticular phacoid shell (or even more); whilst between the latter +and the former (on the proximal girdles) the disk is considerably thinner +(Pl. 36, figs. 2, 4; Pl. 37, figs. 7, 8; Pl. 38, figs. 2, 4). The +stratified layers communicate by large openings between their chambers. The +radial beams are commonly more or less regular and piercing, but also +frequently irregular and interrupted; often their number increases towards +the margin by intercalation of new beams. + +_The Pores_ of the sieve-plates, which cover both sides of the chambered +disk, appear on the margin of the phacoid shell as direct continuations of +the pores of the latter, and sometimes they are so regularly disposed that +one single circular pore is situated on the surface of each chamber (Pl. +36, fig. 7; Pl. 37, fig. 1). But commonly the pores are of variable size +and number, two to three on each chamber, and often quite irregularly +scattered. + +_The Margin_ of the chambered disk exhibits many differences, which afford +characters for the distinction of genera. In the first subfamily, the +Lithocyclida, the margin is quite simple without radial appendages. In the +second subfamily, the Stylocyclida, it is armed with solid radial spines +lying in the equatorial plane, and often regularly disposed in the same +manner as in the Phacodiscida (compare above, p. 421). In the third +subfamily, the Astracturida, the margin bears two or more (commonly three +or four) chambered arms, also situated in the plane of the disk, and of the +same structure as the circular chambered girdles (Pl. 38). In some cases +even the whole system of chamber-girdles is represented only by the radial +arms, which are inserted immediately on the margin of the phacoid shell. We +may regard therefore these formations as imperfect chambered disks, which +are developed only in the direction of certain rays {458}(perradii), and +reduced in the direction of the alternating rays (interradii). In some +Astracturida the chambered arms exhibit a structure different from the more +irregular chamber-work between them, so that we can distinguish the latter, +connecting the arms like a web-membrane, as a peculiar "patagium" (as in +many Porodiscida) (Pl. 38, figs. 8, 9). Often the distal ends of the +chambered arms are armed with a radial spine (Pl. 38, figs. 5, 6, 9). + +_The Central Capsule_ of the Coccodiscida is originally always of the same +form and shape as in their ancestral group, the Phacodiscida; a circular +lenticular disk, which envelops the simple or double medullary shell and is +enclosed by the cortical phacoid shell. But whilst in the Phacodiscida the +phacoid shell envelops the central capsule perfectly, in the Coccodiscida +it envelops only the capsule from the two flat sides (by the upper and +lower sieve-plates); the marginal part of the lenticular capsule overgrows +the margin of the phacoid shell by peripheral extension, and fills out the +chambered cavity of the concentric girdles. In the Lithocyclida and the +Stylocyclida, where there are no chambered arms, the central capsule +remains a simple circular lens or disk; in the Astracturida, where +chambered radial arms surround the margin of the circular central disk, the +capsule enters also into these arms and fills out the greatest part of +their chambered cavities. + +_Synopsis of the Genera of Coccodiscida_. + + ------------------------------------------------------------------------- + I. Subfamily Lithocyclida. + Margin of the disk simple, circular, without radial appendages. + ------------------------------------------------------------------------- + Neither radial spines nor {Medullary shell simple, 196. _Lithocyclia_. + chambered arms on the { + circular margin. {Medullary shell double, 197. _Coccodiscus_. + ------------------------------------------------------------------------- + II. Subfamily Stylocyclida. + Margin of the disk armed with solid radial spines. + ------------------------------------------------------------------------- + Two opposite spines. {Medullary shell simple, 198. _Stylocyclia_. + { + {Medullary shell double, 199. _Amphicyclia_. + + Three radial spines. Medullary shell simple, 200. _Trigonocyclia_. + + Four crossed spines. Medullary shell simple, 201. _Staurocyclia_. + + Five to ten or more {Medullary shell simple, 202. _Astrocyclia_. + radial spines. { + {Medullary shell double, 203. _Coccocyclia_. + ------------------------------------------------------------------------- + III. Subfamily Astracturida. + Margin of the disk with two to five or more (commonly three or four) + hollow radial chambered arms (with or without a connecting + patagium). (Medullary shell commonly simple.) + ------------------------------------------------------------------------- + Two arms, opposite in {Without patagium, 204. _Diplactura_. + one axis. { + {With patagium, 205. _Amphiactura_. + + Three radial arms (at {Without patagium, 206. _Trigonactura_. + equal distances). { + {With patagium, 207. _Hymenactura_. + + Four arms (in two {Without patagium, 208. _Astractura_. + crossed diameters). { + {With patagium, 209. _Stauractura_. + + Five radial arms (at {Without patagium, 210. _Pentactura_. + variable distances). { + {With patagium, 211. _Echinactura_. + + + +{459}Subfamily 1. LITHOCYCLIDA, Haeckel, 1881, Prodromus, p. 458. + +_Definition._--#Coccodiscida# with simple circular disk, without any radial +appendages of the margin (either solid radial spines or chambered arms). + + + +Genus 196. _Lithocyclia_,[235] Ehrenberg, 1847, Monatsber. d. k. preuss. +Akad. d. Wiss. Berlin, p. 54. + +_Definition._--#Coccodiscida# with simple circular margin of the disk, +without radial appendages. Medullary shell simple. + +The genus _Lithocyclia_ is the most simple form of Coccodiscida, and +represents the common ancestral form of this family, from which all other +genera of it can be derived. The lenticular, biconvex disk is quite simple, +composed of a variable number of concentric, circular, chambered rings, +which are pierced by radial beams, and which surround the circular +lenticular cortical shell or "phacoid shell." The latter contains a simple +spherical medullary shell in its centre, and is connected with it by radial +beams. The margin of the disk is circular, quite simple, without radial +spines or chambered arms. + + +1. _Lithocyclia cingulata_, n. sp. + +Phacoid shell (or lenticular porous cortical shell) three times as broad as +the spherical enclosed medullary shell, surrounded by one single chambered +girdle or ring (with about forty chambers of equal size, separated by +radial beams). Margin of the disk circular, smooth. Pores of the convex +covering plates regular, circular; eight on the radius of the phacoid +shell, two on the breadth of the ring. + +_Dimensions._--Diameter of the disk (with one ring) 0.13, of the phacoid +shell 0.1, of the medullary shell 0.033. + +_Habitat._--Western Tropical Pacific, Station 225, depth 4475 fathoms. + + +2. _Lithocyclia lenticula_, n. sp. (Pl. 36, figs. 3, 4). + +Phacoid shell two and a half times as broad as the enclosed medullary +shell, surrounded by three chambered girdles of equal size, which are +divided by piercing radial beams each into about fifty chambers. Margin of +the disk thorny. Pores irregular, roundish; seven on the radius of the +phacoid shell, two on the breadth of each girdle. + +_Dimensions._--Diameter of the disk (with three girdles) 0.2, of the +phacoid shell 0.11, of the medullary shell 0.045. + +_Habitat._--Pacific, central area, Station 268, depth 2900 fathoms. + + +{460}3. _Lithocyclia ocellus_, Ehrenberg. + + _Lithocyclia ocellus_, Ehrenberg, 1854, Mikrogeol., Taf. xxxvi. fig. 30; + Abhandl. d. k. Akad. d. Wiss. Berlin, 1875, Taf. xxix. fig. 3. + +Phacoid shell three times as broad as the medullary shell, surrounded by +numerous (seven to eleven) chambered rings, which are divided by piercing +radial beams each into sixty to ninety chambers. Margin of the disk smooth. +Pores regular, circular; nine on the radius of the phacoid shell, one +single pore on each chamber. + +_Dimensions._--Diameter of the disk (with eleven rings) 0.22, of the +phacoid shell 0.1, of the medullary shell 0.035. + +_Habitat._--Fossil in the rocks of Barbados. + + +4. _Lithocyclia monococcus_, n. sp. + + _Stephanopyxis dubiosa_ (?), Bury, 1862, Polycystins of Barbados, pl. + xiii. figs. 1, 2. + +Phacoid shell four times as broad as the medullary shell, surrounded by +numerous (five to eight) chambered rings, which are divided by piercing +radial beams each into fifty to seventy chambers. Margin of the disk +thickened, thorny. Pores regular, circular; seven on the radius of the +phacoid shell, one single pore on each chamber. + +_Dimensions._--Diameter of the disk (with eight rings) 0.18, of the phacoid +shell 0.12, of the medullary shell 0.03. + +_Habitat._--Pacific, central area, Station 267, depth 2700 fathoms; also +fossil in the rocks of Barbados. + + +5. _Lithocyclia heteropora_, n. sp. + +Phacoid shell two and a third times as broad as the medullary shell, +surrounded by five to nine chambered rings, which are divided by piercing +radial beams each into fifty to seventy chambers. Margin of the disk +smooth. Pores very different in the inner and outer part of the surface; in +the phacoid shell larger, regular, circular, eight on its radius, in the +chambered periphery very small and irregular, somewhat spongy. + +_Dimensions._--Diameter of the disk (with nine rings) 0.2, of the phacoid +shell 0.13, of the medullary shell 0.055. + +_Habitat._--Pacific, central area, Station 263, depth 2650 fathoms. + + + +Genus 197. _Coccodiscus_,[236] Haeckel, 1862, Monogr. d. Radiol., p. 485. + +_Definition._--#Coccodiscida# with simple circular margin of the disk, +without radial appendages. Medullary shell double. + +The genus _Coccodiscus_ has quite the same form and structure as the +preceding _Lithocyclia_, and differs from it only in the double medullary +shell, composed of two concentric latticed spheres; sometimes the inner +medullary shell is spherical, the outer {461}lenticular; the latter is +connected with the lenticular phacoid shell (or cortical shell) by radial +beams. + + +1. _Coccodiscus lamarckii_, n. sp. (Pl. 36, fig. 1). + +Phacoid shell (or lenticular porous cortical shell) very thick walled (as +thick as one ring), three times as broad as the outer and seven times as +broad as the inner medullary shell, surrounded by two to three chambered +rings of equal breadth, each of which is divided by piercing radial beams +into thirty-six to forty square chambers. Margin of the disk circular, +smooth. Pores regular, circular, of equal size; ten on the radius of the +phacoid shell, two on the breadth of each chamber. + +_Dimensions._--Diameter of the disk (with two rings) 0.2, of the phacoid +shell 0.14, outer medullary shell 0.05, inner 0.02. + +_Habitat._--Western Tropical Pacific, Station 220, depth 1100 fathoms. + + +2. _Coccodiscus darwinii_, Haeckel. + + _Coccodiscus darwinii_, Haeckel, 1862, Monogr. d. Radiol., p. 486, Taf. + xxviii. figs. 11, 12. + +Phacoid shell three times as broad as the outer and nine times as broad as +the inner medullary shell, surrounded by five to eight chambered rings of +equal breadth, each of which is divided by forty piercing radial beams into +forty square chambers of equal size. Margin of the disk smooth, circular. +Pores irregular, roundish, of unequal size; eleven on the radius of the +phacoid shell, one to two on each chamber. + +_Dimensions._--Diameter of the disk (with eight rings) 0.32, of the phacoid +shell 0.11, outer medullary shell 0.036, inner 0.012. + +_Habitat._--Mediterranean, Messina, surface. + + +3. _Coccodiscus goethei_, n. sp. (Pl. 36, fig. 2). + +Phacoid shell two and a half times as broad as the outer and five times as +broad as the inner medullary shell, surrounded by three to seven chambered +rings of equal breadth, each of which is divided by piercing radial beams +into sixty to eighty chambers. Margin of the disk thorny. Pores regular, +circular; eight on the radius of the phacoid shell, a single one on the +breadth of each chamber. + +_Dimensions._--Diameter of the disk (with seven rings) 0.25, of the phacoid +shell 0.1, of the medullary shell 0.04, inner 0.02. + +_Habitat._--South Atlantic, Station 332, depth 2200 fathoms. + + + +Subfamily 2. STYLOCYCLIDA, Haeckel, 1881, Prodromus, p. 458. + +_Definition._--#Coccodiscida# with solid radial spines on the margin of the +circular disk, situated in its equatorial plane (without chambered arms). + + + +{462}Genus 198. _Stylocyclia_,[237] Ehrenberg, 1847, Monatsber. d. k. +preuss. Akad. d. Wiss. Berlin, p. 54. + +_Definition._--#Coccodiscida# with two opposite solid radial spines on the +margin of the circular disk. Medullary shell simple. + +The genus _Stylocyclia_ opens the series of the Stylocyclida or of those +Coccodiscida in which the margin of the chambered disk is armed with solid +radial spines, situated in its equatorial plane, but without chambered +arms. _Stylocyclia_ is the most simple form of this subfamily, and bears +only two marginal spines, opposite in one equatorial axis of the disk. The +medullary shell is simple. This genus corresponds to _Xiphodictya_ in the +family Porodiscida. The genus was previously known only by one single +species described by Ehrenberg. + + +1. _Stylocyclia dimidiata_, Ehrenberg. + + _Stylocyclia dimidiata_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. + Berlin, p. 84, Taf. xxix. fig. 4. + +Phacoid shell three times as broad as the medullary shell, surrounded by +five to eight chambered rings of equal breadth, divided by eighty to ninety +piercing radial beams into square chambers. Pores subregular, circular; six +to seven on the radius of the phacoid shell, a single one on each chamber. +Both opposite marginal spines strong, club-shaped, their thickness +decreasing from the margin towards the centre of the disk. (The figure of +Ehrenberg is very incomplete.) + +_Dimensions._--Diameter of the disk (with eight rings) 0.25, of the phacoid +shell 0.11, of the medullary shell 0.035. + +_Habitat._--Fossil in the Tertiary rocks of Barbados; living in the depths +of the Equatorial Atlantic, Station 348, depth (2450) fathoms. + + +2. _Stylocyclia prionacantha_, n. sp. (Pl. 37, fig. 6). + +Phacoid shell two and a half times as broad as the medullary shell, +surrounded by five to six chambered rings, which are divided by fifty to +sixty piercing radial beams into square chambers. Pores in the thick-walled +phacoid shell regularly circular, increasing in size from the centre; eight +to nine on its radius. Pores on the surface of the chambered girdle +smaller, very irregular, two to three on each ring. Both marginal spines +longer than the diameter of the disk, with broad serrated edges. + +_Dimensions._--Diameter of the disk (with five rings) 0.23, of the phacoid +shell 0.12, of the medullary 0.05. + +_Habitat._--Pacific, central area, Station 268, depth 2900 fathoms. + + +{463}3. _Stylocyclia excavata_, n. sp. (Pl. 37, fig. 8). + +Phacoid shell four times as broad as the medullary shell, surrounded by +four chambered rings, which are divided by twenty to thirty radial beams +into broad chambers. The height of the rings increases strongly from the +centre, so that the fourth ring is two and a half times as high as the +first. Pores irregular, roundish; five to six on the radius of the phacoid +shell, one to two on the breadth of each ring. Margin of the disk smooth. +Both marginal spines thin and long, cylindrical, arising from the medullary +shell, longer than the diameter of the disk. + +_Dimensions._--Diameter of the disk (with four rings) 0.25, of the phacoid +shell 0.1, of the medullary shell 0.025. + +_Habitat._--Fossil in the rocks of Barbados. Indian Ocean, Cocos Islands, +Rabbe. + + +4. _Stylocyclia amphacantha_, n. sp. + +Phacoid shell twice as broad as the medullary shell, surrounded by five +chambered rings, divided by piercing beams each into forty to fifty +chambers. Pores regular, circular; eight to nine on the radius of the +phacoid shell, one on each chamber. Margin of the disk thorny. Both +marginal spines strong, conical, as long as its radius. + +_Dimensions._--Diameter of the disk (with five rings) 0.24, of the phacoid +shell 0.1, of the medullary shell 0.05. + +_Habitat._--Pacific, central area, Station 265, depth 2900 fathoms. + + + +Genus 199. _Amphicyclia_,[238] Haeckel, 1881, Prodromus, p. 458. + +_Definition._--#Coccodiscida# with two opposite solid radial spines on the +margin of the circular disk. Medullary shell double. + +The genus _Amphicyclia_ has the same form and structure as _Stylocyclia_, +and differs from it only in the double concentric medullary shell. It bears +therefore to the latter the same relation that _Coccodiscus_ does to +_Lithocyclia_. + + +1. _Amphicyclia chronometra_, n. sp. (Pl. 38, fig. 1). + +Phacoid shell three times as broad as the outer and nine times as broad as +the inner medullary shell, surrounded by two broad chambered rings, which +are divided into irregular chambers by fifty to sixty radial beams of +different distance. Margin of the disk thorny, lacerated. Pores irregular, +roundish; twelve to sixteen on the radius of the phacoid shell, two to +three on the breadth of each ring. The two opposite marginal spines strong, +prismatic, with prominent edges, about as long as the diameter of the disk. + +_Dimensions._--Diameter of the disk (with two rings) 0.24, of the phacoid +shell 0.15, outer medullary shell 0.05, inner 0.017. + +_Habitat._--Pacific, central area, Stations 265 to 268, depths 2700 to 2900 +fathoms. + + +{464}2. _Amphicyclia amphistyla_, n. sp. (Pl. 37, fig. 7). + + _Stylocyclia amphistyla_, Haeckel, 1879, MS. et Atlas (pl. xxxvii. fig. + 7). + +Phacoid shell thin walled, two and a half times as broad as the outer and +seven times as broad as the inner medullary shell, divided by eighty to +ninety radial beams into irregular chambers, which are stratified in four +to five floors. Pores regular, circular; eight to nine on the radius of +the phacoid shell, two on the breadth of each chamber. Both marginal +spines cylindrical. + +_Dimensions._--Diameter of the disk (with seven rings) 0.27, of the phacoid +shell 0.1, outer medullary shell 0.04, inner 0.014. + +_Habitat._--North Atlantic, Canary Islands, Station 354, surface. + + +3. _Amphicyclia pachydiscus_, n. sp. (Pl. 38, fig. 2). + +Phacoid shell very thick, spongy, twice as broad as the outer and five +times as broad as the inner medullary shell, divided by fifty to seventy +radial beams into subregular chambers, which are stratified in five to six +floors. Pores irregular, roundish; ten to twelve on the radius of the +phacoid shell, two to three on the breadth of each chamber. The two +opposite marginal spines quadrangular prismatic, very long, as broad as the +radius of the inner medullary shell. Fig. 2 exhibits a vertical section +(slide) through the centre. + +_Dimensions._--Diameter of the disk (with five rings) 0.22, of the phacoid +shell 0.1, outer medullary shell 0.05, inner 0.02. + +_Habitat._--South Atlantic, Station 332, depth 2200 fathoms; fossil in +Barbados. + + + +Genus 200. _Trigonocyclia_,[239] Haeckel, 1881, Prodromus, p. 458. + +_Definition._--#Coccodiscida# with three solid radial spines on the margin +of the circular disk. Medullary shell simple. + +The genus _Trigonocyclia_ (only known by one single species, once observed) +bears on the margin of the chambered disk three solid radial spines, at +equal distances one from another. It corresponds to the genus +_Tripodictya_ amongst the Porodiscida. + + +1. _Trigonocyclia triangularis_, n. sp. (Pl. 37, fig. 5). + +Phacoid shell three times as broad as the medullary shell, connected with +it by six equidistant radial beams, three of which are prolonged into +marginal spines. In the equatorial plane only one single chambered ring, +divided by forty-four radial beams into narrow chambers. Pores large, +irregular, roundish; five on the radius of the phacoid shell, two on each +chamber. Surface and margin of the disk spiny. Three strong conical +marginal spines, divergent at equal angles, as long as the radius of the +disk. + +_Dimensions._--Diameter of the disk 0.16, of the phacoid shell 0.12, of the +medullary shell 0.04. + +_Habitat._--Indian Ocean, Zanzibar, depth 2200 fathoms, Pullen. + + + +{465}Genus 201. _Staurocyclia_,[240] Haeckel, 1881, Prodromus, p. 458. + +_Definition._--#Coccodiscida# with four solid radial spines on the margin +of the disk, crossed in two equatorial diameters perpendicular one to +another. Medullary shell simple. + +The genus _Staurocyclia_ is characterised by four radial spines on the +margin of the disk, which are opposite in pairs and situated in two +equatorial diameters, commonly perpendicular one to another. They form +therefore a rectangular cross (rarely more or less irregular). The genus +corresponds exactly to _Staurodictya_ in the family Porodiscida. The +medullary shell is simple. + + +1. _Staurocyclia cruciata_, n. sp. (Pl. 37, fig. 1). + +Phacoid shell two and a half times as broad as the medullary shell, +surrounded by six to eight regular rings, which are divided by fifty to +seventy piercing beams into square chambers. Pores regular, circular; six +on the radius of the phacoid shell, one single pore on each chamber. Four +crossed radial spines, arising from the medullary shell by thin bases, +prolonged over the dentated margin as four strong quadrangular swords, as +long as the radius of the disk. + +_Dimensions._--Diameter of the disk (with eight rings) 0.23, of the phacoid +shell 0.09, of the medullary shell 0.035. + +_Habitat_--Pacific, central area, Station 267, depth 2700 fathoms. + + +2. _Staurocyclia serrata_, n. sp. + + ? _Haliomma_ sp., Bury, 1862, Polycystins of Barbados, pl. xxii. fig. 2. + +Phacoid shell twice as broad as the medullary shell, surrounded by three to +four spongy rings, which are divided by thirty to forty radial beams into +irregular chambers. Pores in the phacoid shell regular, circular, five on +its radius; in the chambered spongy girdle much smaller and irregular. +Margin dentated, with four crossed, very large, quadrangular spines, as +long as the radius of the disk, with wing-shaped, serrated edges. + +_Dimensions._--Diameter of the disk (with four rings) 0.2, of the phacoid +shell 0.1, of the medullary shell 0.05. + +_Habitat._--Fossil in the rocks of Barbados. + + +3. _Staurocyclia phacostaurus_, n. sp. (Pl. 37, figs. 2, 3). + + _Phacostaurus pyramidalis_, Haeckel, 1879, MS. (as a separate genus). + +Phacoid shell two and a quarter times as broad as the medullary shell, +connected with it by twelve radial beams (four equatorial and eight +divergent) and surrounded by one single ring, which is divided by forty +radial beams into regular chambers. Pores regular, honeycomb-like in the +{466}phacoid shell, seven on its radius; smaller on the equatorial ring, +three on its breadth. Four marginal spines pyramidal four-sided, as long +and as broad at the base as the ring. + +_Dimensions._--Diameter of the disk (with one ring) 0.14, of the phacoid +shell 0.11, of the medullary shell 0.048. + +_Habitat._--South Atlantic, Station 335, depth 1425 fathoms. + + +4. _Staurocyclia magniducis_, n. sp. (Pl. 37, fig. 4). + + _Coccostaurus magniducis_, Haeckel, 1881, MS. et Atlas (pl. xxxvii. fig. + 4). + +Phacoid shell twice as broad as the medullary shell, connected with it by +numerous radial beams and surrounded by eight chambered rings, which are +divided by one hundred to one hundred and twenty piercing radial beams into +small chambers. Pores subregular, circular; ten on the radius of the +phacoid shell, two on the breadth of each chamber. Margin of the disk armed +with numerous bristle-shaped radial spines, as long as the breadth of the +chambered girdle. Four very large crossed spines, nearly as long as the +diameter of the disk, quadrangular, with four dentated edges; at the +club-shaped distal end thorny, as broad as the medullary shell and three +times as broad as at the narrow base. I name this splendid species in the +honour of H.R.H. the Grand Duke of Saxe-Weimar, Carl Alexander, the +magnanimous protector of arts and sciences, the rector magnificentissimus +of the University of Jena. + +_Dimensions._--Diameter of the disk (with eight rings) 0.27, of the phacoid +shell 0.11, of the medullary shell 0.05; length of the four crossed +club-spines 0.2, basal breadth 0.02, distal breadth 0.06. + +_Habitat._--Indian Ocean, Ceylon, Belligemma, surface (Haeckel). + + + +Genus 202. _Astrocyclia_,[241] Haeckel, 1881, Prodromus, p. 458. + +_Definition._--#Coccodiscida# with numerous (five or more, commonly thirty +to sixty) solid radial spines on the margin of the circular disk. Medullary +shell simple. + +The genus _Astrocyclia_ exhibits on the margin of the circular chambered +disk a large but variable number of solid radial spines, commonly between +thirty and sixty. They are the external prolongations of the inner piercing +radial beams, which divide the concentric rings of the disk into chambers. +All the spines lie in the equatorial plane of the disk. The genus +corresponds to _Stylodictya_ in the family Porodiscida. + + +1. _Astrocyclia solaster_, n. sp. (Pl. 36, fig. 7). + +Phacoid shell two and a half times as broad as the medullary shell, +surrounded by four to six regular rings of equal breadth, which are divided +by thirty to forty piercing radial beams into broad {467}chambers. Pores +regular, circular; seven on the radius of the phacoid shell, one single +pore on each chamber (the size increasing from the centre). Margin with +thirty to forty angular, broad, dentate spines, the prolongations of the +inner radial beams. + +_Dimensions._--Diameter of the disk (with six rings) 0.22, of the phacoid +shell 0.1, of the medullary shell 0.04. + +_Habitat._--Pacific, central area, Station 268, depth 2900 fathoms. + + +2. _Astrocyclia stella_, Haeckel. + + _Lithocyclia stella_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. + Berlin, p. 78, Taf. xxix. fig. 2. + +Phacoid shell three times as broad as the medullary shell, surrounded by +four to eight rings of increasing breadth from the centre, the outer of +which are more or less spongy. Each ring is divided by forty to fifty +piercing radial beams into chambers of increasing size. Pores regular, +circular; a single one on each chamber, ten on the radius of the phacoid +shell. On the margin are scattered ten to twenty thick and short spines, +four-sided pyramidal, about as long and as broad at the base as the +diameter of the medullary shell. + +_Dimensions._--Diameter of the disk (with eight rings) 0.25, of the phacoid +shell 0.09, of the medullary shell 0.03. + +_Habitat._--Fossil in the rocks of Barbados. + + +3. _Astrocyclia rotula_, n. sp. + +Phacoid shell four times as broad as the medullary shell, surrounded by one +single ring, which is divided by forty radial beams into equal chambers. +Pores regular, circular; two on the breadth of the ring, six on the radius +of the phacoid shell. Margin with forty short, conical spines, the +prolongations of the inner radial beams, twice as long as the breadth of +the ring. + +_Dimensions._--Diameter of the disk 0.13, of the phacoid shell 0.1, of the +medullary shell 0.025. + +_Habitat._--South Atlantic, Station 332, depth 2200 fathoms. + + +4. _Astrocyclia arachnia_, n. sp. + +Phacoid shell twice as broad as the medullary shell, surrounded by four to +six rings of equal breadth, which are divided by twelve to twenty radial +beams into broad chambers. Pores regular, circular; two on the breadth of +each ring, eight on the radius of the phacoid shell. Margin with twelve to +twenty very long and thin, bristle-shaped, radial spines, the prolongations +of the inner beams, longer than the diameter of the disk. (Resembles +_Stylodictya arachnia_, but differs in the possession of a phacoid shell.) + +_Dimensions._--Diameter of the disk (with six rings) 0.22, of the phacoid +shell 0.09, of the medullary shell 0.045. + +_Habitat._--North Atlantic, Canary Islands. + + +{468}5. _Astrocyclia heterocycla_, n. sp. (Pl. 36, fig. 8). Phacoid shell +two and a half times as broad as the medullary shell, surrounded by three +rings of unequal breadth, the first ring as broad as the second and third +together. They are divided by fifty to sixty piercing radial beams into +chambers, which are square in the second and third rings, and half as large +as in the first. The radial beams are alternately thicker and thinner, +prolonged into short marginal spines. Pores subregular, circular; eight on +the radius of the phacoid shell, two on the breadth of the first ring, a +single one on each chamber of the second and third rings. + +_Dimensions._--Diameter of the disk (with three rings) 0.2, of the phacoid +shell 0.12, of the medullary shell 0.05. + +_Habitat._--Equatorial Atlantic, Station 348, depth (2450) fathoms; also +fossil in Barbados. + + + +Genus 203. _Coccocyclia_,[242] Haeckel, 1881, Prodromus, p. 458. + +_Definition._--#Coccodiscida# with numerous (five or more) solid radial +spines on the margin of the circular disk. Medullary shell double. + +The genus _Coccocyclia_ has the same form and structure as the foregoing +_Astrocyclia_, and differs from it only in the double concentric medullary +shell. It bears therefore to the latter the same relation as _Coccodiscus_ +to _Lithocyclia_. + + +1. _Coccocyclia liriantha_, n. sp. + +Phacoid shell three times as broad as the outer and ten times as broad as +the inner medullary shell, connected with both by six equidistant piercing +radial beams. The margin of the phacoid shell is surrounded by one or two +equatorial rings, each as broad as the outer medullary shell, and divided +by thirty to forty radial beams into narrow chambers. Pores subregular, +circular, about nine to ten on the radius of the phacoid shell, three to +four on the breadth of each ring. Margin of the disk ciliated, with six +regularly disposed radial spines as prolongations of the inner six piercing +beams. Each spine cylindrical, delicately crenulated, about as broad as the +inner medullary shell, and once to twice as long as the diameter of the +whole disk, elegantly undulated, with a conical terminal point. + +_Dimensions._--Diameter of the disk (with two rings) 0.32, of the phacoid +shell 0.2, of the outer medullary shell 0.06, of the inner 0.02. + +_Habitat._--Pacific, central area, Station 265, depth 2900 fathoms. + + +2. _Coccocyclia heliantha_, n. sp. (Pl. 36, figs. 5, 6). + +Phacoid shell two and a half times as broad as the outer and six times as +broad as the inner medullary shell, surrounded by six to eight rings of +nearly equal breadth, the outer somewhat smaller. They are divided by fifty +to sixty piercing radial beams into irregular chambers. Pores +{469}irregular, roundish; ten on the radius of the phacoid shell, a single +one on each chamber of the equatorial girdle. Margin of the disk with +numerous strong conical radial spines of different breadths, arranged in +several circles, the strongest in the equatorial plane, about as broad as +one ring and twice as long. Surface thorny. + +_Dimensions._--Diameter of the disk (with seven rings) 0.3, of the phacoid +shell 0.12, of the outer medullary shell 0.05, of the inner 0.02. + +_Habitat._--Pacific, central area, Station 268, depth 2900 fathoms; also +fossil in Barbados. + + + +Subfamily 3. ASTRACTURIDA, Haeckel, 1881, Prodromus, p. 458. + +_Definition._--#Coccodiscida# with two or more (commonly three or four) +chambered radial arms on the margin of the disk, situated in its equatorial +plane (with or without a connecting patagium between the arms). + + + +Genus 204. _Diplactura_,[243] Haeckel, 1881, Prodromus, p. 458. + +_Definition._--#Coccodiscida# with two opposite chambered arms on the +margin of the circular disk, without a connecting patagium. + +The genus _Diplactura_ is the simplest form of the Astracturida, or of +those Coccodiscida in which the margin of the disk bears chambered arms, +situated in its equatorial plane. This subfamily corresponds to the +Euchitonida among the Porodiscida, to the Spongobrachida among the +Spongodiscida. In _Diplactura_ there are only two free arms, opposite in +one equatorial diameter (corresponding to _Amphibrachium_ among the former, +to _Spongolena_ among the latter). + + + +Subgenus 1. _Diplacturium_, Haeckel. + +_Definition._--Arms blunt at the distal end, without radial spines. + + +1. _Diplactura diplobrachia_, n. sp. + +Phacoid shell twice as broad as the medullary shell, with six pores on its +radius, without a perfect chambered ring around it. Arms club-shaped, one +and a half times as long as the diameter of the phacoid shell, at the +distal end rounded, blunt, as broad as the latter, at the base only half as +broad. + +_Dimensions._--Diameter of the phacoid shell 0.08, of the medullary shell +0.04; length of the arms 0.12, basal breadth 0.04, distal breadth 0.08. + +_Habitat._--Pacific, central area, Station 265, depth 2900 fathoms. + + + +{470}Subgenus 2. _Diplactinium_, Haeckel. + +_Definition._--Arms on the distal end armed with a radial terminal spine. + + +2. _Diplactura diploconus_, n. sp. (Pl. 38, fig. 5). + + _Amphiactura diploconus_, Haeckel, 1877, MS. et Atlas (pl. xxxviii. fig. + 5). + +Phacoid shell three times as broad as the medullary shell, with eight pores +on its radius, surrounded by a single chambered ring. Arms club-shaped, +twice as long as the diameter of the phacoid shell, at the distal end as +broad as the latter, at the base only half as broad. Both poles of the +common axis of the arms are armed with a strong spindle-shaped terminal +spine. + +_Dimensions._--Diameter of the phacoid shell 0.09, of the medullary shell +0.03; length of the arms (without terminal spines) 0.17, basal breadth +0.05, distal breadth 0.09. + +_Habitat._--Pacific, central area, Station 268, depth 2900 fathoms. + + + +Genus 205. _Amphiactura_,[244] Haeckel, 1881, Prodromus, p. 458. + +_Definition._--#Coccodiscida# with two opposite chambered arms on the +margin of the circular disk, connected by a spongy patagium. + +The genus _Amphiactura_ differs from the foregoing _Diplactura_ in the +development of a patagium between the arms, and therefore bears the same +relation to it as _Amphymenium_ in the Porodiscida does to _Amphibrachium_, +or _Spongobrachium_ in the Spongodiscida does to _Spongolene_. In this and +in the following #Discoidea# provided with a patagium, this connecting web +constantly exhibits a different texture of its framework, which is +sometimes more regularly chambered, at other times more irregularly spongy. + + +1. _Amphiactura amphibrachia_, n. sp. (Pl. 38, figs. 3, 4). + +Phacoid shell three times as broad as the medullary shell, with eight pores +on its radius. Arms nearly equilateral triangular, twice as long as the +diameter of the phacoid shell, at the truncated distal end as broad as the +latter, at the base only one-third as broad. Patagium a circular lenticular +disk, enveloping only the basal third of the arms, with three to four +concentric circular rings, divided into chambers by about forty radial +beams, which are prolonged beyond the margin of the patagium into radial +spines. The vertical section (fig. 4) shows that the chambers of each arm +(eleven to twelve transverse rows in the radius) are disposed in two +layers. + +_Dimensions._--Diameter of the phacoid shell 0.09, of the medullary shell +0.03; length of the arms 0.18, basal breadth 0.03, distal breadth 0.09. + +_Habitat._--Pacific, central area, Station 263, depth 2650 fathoms. + + + +{471}Genus 206. _Trigonactura_,[245] Haeckel, 1881, Prodromus, p. 459. + +_Definition._--#Coccodiscida# with three chambered arms on the margin of +the circular or triangular disk, without a connecting patagium. + +The genus _Trigonactura_ exhibits three radial arms, which in all known +species are separated by three equal angles. The terminal points of the +arm-axes are the corners of an equilateral triangle. It corresponds +therefore to _Dictyastrum_ among the Porodiscida. + + + +Subgenus 1. _Trigonacturium_, Haeckel. + +_Definition._--Distal end of the arms blunt or truncated, without a +terminal spine. + + +1. _Trigonactura pythagorae_, Haeckel. + + _Astromma pythagorae_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. + Berlin, p. 66, Taf. xxx. fig. 2. + +Phacoid shell circular, twice as broad as the medullary shell, with five +pores on its radius, without a completely surrounding chambered girdle. +Arms nearly square, at the truncated distal end as broad as long, and +scarcely broader than at the base, two-thirds as long as the diameter of +the central disk. + +_Dimensions._--Diameter of the phacoid shell 0.1, of the medullary shell +0.05; length of the arms 0.07, distal breadth 0.07. + +_Habitat._--Cosmopolitan; Atlantic, Indian, Pacific, in various depths; +also fossil in Tertiary rocks of Barbados and Nicobar. + + +2. _Trigonactura rhopalastrella_, n. sp. + + _Stephanastrum_ sp., Bury, 1862, Polycystins of Barbados, pl. xv. fig. 7. + +Phacoid shell twice as broad as the medullary shell, with five pores on its +radius, without a perfect chambered ring around it. Arms club-shaped, at +the blunt distal end rounded, as long as the diameter of the phacoid shell; +their basal breadth is one-fourth, their distal breadth one-half of its +length. + +_Dimensions._--Diameter of the phacoid shell 0.1, of the medullary shell +0.05; length of the arms 0.1, basal breadth 0.025, distal breadth 0.05. + +_Habitat._--Pacific, central area, Stations 270 to 274, depths 2400 to 2800 +fathoms; also fossil in Tertiary rocks of Barbados. + + +{472}3. _Trigonactura trigonobrachia_, n. sp. + +Phacoid shell two and a half times as broad as the medullary shell, with +six pores on its radius, without a perfect chambered girdle. Arms nearly +equilateral triangular, twice as long as the diameter of the phacoid shell, +at the truncated distal end as broad as its diameter and three times as +broad as at the narrow base. (Resembles _Hymenactura hexagona_, but without +a patagium.) + +_Dimensions._--Diameter of the phacoid shell 0.11, of the medullary shell +0.045; length of the arms 0.2, basal breadth 0.035, distal breadth 0.1. + +_Habitat._--North Pacific, Station 244, depth 2900 fathoms. + + +4. _Trigonactura lanceolata_, n. sp. + +Phacoid shell three times as broad as the medullary shell, with eight pores +on its radius, surrounded by one perfect chambered ring. Arms lanceolate, +three times as long as the diameter of the phacoid shell, and four times as +long as broad in the middle part, at both ends very narrow, blunt. + +_Dimensions._--Diameter of the phacoid shell 0.09, of the medullary shell +0.03; length of the arms 0.25, breadth in the midst 0.06. + +_Habitat._--South Atlantic, Station 332, depth 2200 fathoms. + + + +Subgenus 2. _Trigonactinium_, Haeckel. + +_Definition._--Distal end of the arms armed with a radial spine. + + +5. _Trigonactura triacantha_, n. sp. (Pl. 38, figs. 6, 7). + +Phacoid shell two and a half times as broad as the medullary shell, with +eight pores on its radius, surrounded by one perfect chambered ring. Arms +nearly lanceolate, in the middle part one and a half times as broad as at +both ends, twice as long as the phacoid shell, at the distal end with a +strong pyramidal terminal spine. Through the spongy framework of each arm +shine sixteen to eighteen transverse bars (as septa of the joints) and six +to eight longitudinal piercing beams. + +_Dimensions._--Diameter of the phacoid shell 0.09, of the medullary shell +0.038; length of the arms 0.2, greatest breadth 0.08. + +_Habitat._--Pacific, central area, Station 265, depth 2900 fathoms. + + +6. _Trigonactura trigonodiscus_, n. sp. + + ? _Astromma_ sp., Bury, 1862, Polycystins of Barbados, Taf. xv. fig. 2. + +Phacoid shell triangular, twice as broad as the spherical medullary shell, +with six to seven pores on its radius, surrounded by one chambered ring. +Arms equilateral triangular, as long as {473}the diameter of the central +disk and at the base half as broad, slowly decreasing in breadth towards +the distal end, which is armed with a strong pyramidal spine. + +_Dimensions._--Diameter of the phacoid shell 0.1, of the medullary shell +0.05; length of the arms 0.12, basal breadth 0.07. + +_Habitat._--Pacific, central area, Station 268, depth 2900 fathoms; also +fossil in Barbados. + + +7. _Trigonactura trixiphos_, n. sp. + +Phacoid shell circular, twice as broad as the medullary shell, without a +completely surrounding chambered ring, with four pores on its radius. Arms +club-shaped, about as long as the diameter of the central disk, at the base +half as broad as long, at the rounded distal end broader, and armed with a +strong pyramidal terminal spine, nearly as long as the arm itself. + +_Dimensions._--Diameter of the phacoid shell 0.08, of the medullary shell +0.04; length of the arms (without terminal spine) 0.08, basal breadth 0.04, +distal breadth 0.06. + +_Habitat._--Fossil in the rocks of Barbados. + + + +Genus 207. _Hymenactura_,[246] Haeckel, 1881, Prodromus, p. 459. + +_Definition._--#Coccodiscida# with three chambered arms on the margin of +the circular or triangular disk, connected by a spongy patagium. + +The genus _Hymenactura_ differs from the foregoing _Trigonactura_ in the +spongy patagium between the arms, and bears therefore to it the same +relation that among the Porodiscida _Hymeniastrum_ does to the simpler +_Dictyastrum_. The oldest known species of this genus is _Hymenactura +pythagorae_, described by Ehrenberg as _Hymeniastrum pythagorae_, but +differing from this in the structure of the central disk. + + + +Subgenus 1. _Hymenacturium_, Haeckel. + +_Definition._--Distal end of the arms blunt or truncated, without terminal +spines. + + +1. _Hymenactura archimedis_, n. sp. (Pl. 38, fig. 8). + +Phacoid shell three times as broad as the medullary shell, with eight pores +on its radius. Arms nearly trapezoidal, somewhat longer than the diameter +of the central disk, at the truncated distal end nearly as broad, at the +base only half as broad. In each arm eleven to twelve transverse rows of +square chambers, each of which exhibits on the surface one large pore. +Patagium enveloping the basal half of the arms, with four to five convex +rows of chambers, forming together a circular concentric disk. + +_Dimensions._--Diameter of the phacoid shell 0.11, of the medullary shell +0.035; length of the arms 0.12, basal breadth 0.05, distal breadth 0.1. + +_Habitat._--Western Tropical Pacific, Station 225, depth 4475 fathoms. + + +{474}2. _Hymenactura pythagorae_, Haeckel. + + _Hymeniastrum pythagorae_, Ehrenberg, 1854, Mikrogeol., Taf. xxxvi. fig. + 31; Abhandl. d. k. Akad. d. Wiss. Berlin, 1875, p. 76, Taf. xxx. fig. 5. + +Phacoid shell three times as broad as the medullary shell, with six pores +on its radius. Arms nearly trapezoidal, somewhat longer than the diameter +of the central disk, at the truncated distal end nearly as broad, at the +base two-thirds as broad. In each arm eight to nine transverse rows of +square chambers, each chamber with one pore on the surface. Patagium +enveloping the basal half of the arms, with four to five rectilinear +parallel rows of chambers, forming together a regular triangle. Differs +from the preceding species mainly in the quite different structure of the +patagium, from the true _Hymeniastrum pythagorae_ in the phacoid shell of +the central disk, which encloses only one simple medullary shell. + +_Dimensions._--Diameter of the phacoid shell 0.11, of the medullary shell +0.04; length of the arms 0.13, basal breadth 0.07, distal breadth 0.12. + +_Habitat._--Fossil in the rocks of Barbados. + + +3. _Hymenactura trigona_, n. sp. + + _Astromma_ sp., Bury, 1862, Polycystins of Barbados, pl. xv. fig. 1. + +Phacoid shell twice as broad as the medullary shell, with four to five +pores on its radius. Arms slender, lanceolate, three times as long as the +diameter of the phacoid shell and five times as long as broad in the middle +part; distal ends blunt. Patagium enveloping only the basal half of the +arms, forming a regular triangle with concave sides. + +_Dimensions._--Diameter of the phacoid shell 0.08, of the medullary shell +0.035; length of the arms 0.2, greatest breadth 0.04. + +_Habitat._--South Atlantic, Station 332, depth 2200 fathoms; fossil in the +rocks of Barbados. + + +4. _Hymenactura hexagona_. + + _Hymeniastrum_ sp., Bury, 1862, Polycystins of Barbados, pl. xv. fig. 3. + +Phacoid shell twice as broad as the medullary shell, with four to five +pores on its radius. Arms nearly equilateral triangular, three times as +long as the diameter of the phacoid shell, at the truncated distal end +nearly three-fourths as broad as long, at the narrow base only one-fourth +as broad. Patagium complete, enveloping the arms completely, so that the +whole body represents a regular hexagonal disk. + +_Dimensions._--Diameter of the phacoid shell 0.08, of the medullary shell +0.04; length of the arms 0.18, basal breadth 0.04, distal breadth 0.16. + +_Habitat._--Fossil in the rocks of Barbados and Nicobar. + + + +{475}Subgenus 2. _Hymenactinium_, Haeckel. + +_Definition._--Distal ends of the arms armed with terminal spines. + + +5. _Hymenactura ptolemaei_, n. sp. + + _Astromma_ sp., Bury, 1862, Polycystins of Barbados, pl. xv. figs. 5, 6. + +Phacoid shell twice as broad as the medullary shell, with six to seven +pores on its radius. Arms nearly square, about as large as the phacoid +shell, at the truncated distal end little broader than at the base, and +armed with a strong pyramidal terminal spine. Patagium incomplete, +enveloping the basal half of the arms. + +_Dimensions._--Diameter of the phacoid shell 0.1, of the medullary shell +0.05; length and greatest breadth of the arms 0.08. + +_Habitat._--Pacific, central area, Station 268, depth 2900 fathoms; fossil +in the rocks of Barbados. + + +6. _Hymenactura copernici_, n. sp. (Pl. 38, fig. 9). + +Phacoid shell three times as broad as the medullary shell, with six pores +on its radius. Arms lanceolate, nearly twice as long as the phacoid shell, +in the middle part twice as broad as the medullary shell, with a strong +conical terminal spine at the distal end. In each arm about ten transverse +rows of chambers. Patagium enveloping the basal half of the arms, with four +convex parallel rows of chambers. + +_Dimensions._--Diameter of the phacoid shell 0.1, of the medullary shell +0.035; length of the arms 0.17, greatest breadth 0.07. + +_Habitat._--Pacific, central area, Station 266, depth 2750 fathoms. + + + +Genus 208. _Astractura_,[247] Haeckel, 1881, Prodromus, p. 459. + +_Definition._--#Coccodiscida# with four chambered arms on the margin of the +circular or quadrangular disk, crossed in two equatorial diameters, without +a connecting patagium. + +The genus _Astractura_ has the form of a regular cross, four radial arms +being opposite in two equatorial diameters perpendicular one to another. In +the Porodiscida the same form is repeated by _Stauralastrum_, in the +Spongodiscida by _Spongasteriscus_. The oldest known species of the genus +is _Astromma aristotelis_ of Ehrenberg, in which genus this author +confounded triradial and four-radial forms. + + + +{476}Subgenus 1. _Astracturium_, Haeckel. + +_Definition._--Distal end of the arms blunt or truncated, without terminal +spines. + + +1. _Astractura ordinata_, n. sp. + + ? _Astromma_ sp., Bury, 1862, Polycystins of Barbados, pl. xiv. fig. 3. + +Phacoid shell three times as broad as the medullary shell, with six pores +on its radius, without a completely developed chambered ring. Arms +trapezoidal, somewhat longer than the radius of the disk, at the truncated +distal end as broad as long, at the base one-third smaller. + +_Dimensions._--Diameter of the phacoid shell 0.08, of the medullary shell +0.03; length of the arms 0.05, distal breadth 0.05, basal breadth 0.035. + +_Habitat._--Tropical Atlantic, Station 348, depth 2450 fathoms; also fossil +in Barbados. + + +2. _Astractura clavigera_, n. sp. + + _Astromma aristotelis_, Bury, 1862, Polycystins of Barbados, pl. iv. fig. + 2. + +Phacoid shell twice as broad as the medullary shell, with ten pores on its +radius, surrounded by one perfect chambered ring. Arms club-shaped, about +as long as the radius of the central disk, at the rounded distal end +two-thirds, at the base one-third as broad as long. + +_Dimensions._--Diameter of the phacoid shell 0.1, of the medullary shell +0.05; length of the arms 0.06, basal breadth 0.02, distal breadth 0.04. + +_Habitat._--Pacific, central area, Stations 270 to 274, depths 2350 to 2925 +fathoms; fossil in the rocks of Barbados. + + + +Subgenus 2. _Astractinium_, Haeckel. + +_Definition._--Distal end of the arms furnished with a radial spine. + + +3. _Astractura aristotelis_, Haeckel. + + _Astromma aristotelis_, Ehrenberg, 1856, Microgeol., Taf. xxxvi. fig. 32; + Abhandl. d. k. Akad. d. Wiss. Berlin, 1875, p. 66, Taf. xxx. fig. 4. + + _Astromma aristotelis_, Haeckel, 1862, Monogr. d. Radiol., p. 489. + + ? _Astromma aristotelis_, Bury, 1862, Polycystins of Barbados, pl. xiv. + fig. 4. + +Phacoid shell three times as broad as the medullary shell, with six to +eight pores on its radius, surrounded by one perfect chambered ring. Arms +nearly trapezoidal, about as long as the diameter of the central disk, at +the base half as broad, at the truncated distal end nearly as broad as +long, and armed with a large pyramidal terminal spine. Each arm with about +eight transverse and longitudinal rows of chambers. + +{477}_Dimensions._--Diameter of the phacoid shell 0.11, of the medullary +shell 0.04; length of the arms 0.1, basal breadth 0.05, distal breadth +0.09. + +_Habitat._--Cosmopolitan; Atlantic, Indian, Pacific, at various depths; +fossil in the Tertiary rocks of Barbados and Nicobar. + + +4. _Astractura democriti_, n. sp. + + _Astromma aristotelis_, var., Ehrenberg, 1875, Abhandl. d. k. Akad. d. + Wiss. Berlin, p. 66, Taf, xxx. fig. 3. + + ? _Astromma aristotelis_, var., Bury, 1862, Polycystins of Barbados, pl. + xiv. fig. 4. + +Phacoid shell twice as broad as the medullary shell, with five to seven +pores on its radius, without perfect chambered ring. Arms about twice as +long as broad, longer than the diameter of the central disk, at the +truncated distal end a little broader than at the base, and armed with a +strong, pyramidal, terminal spine. + +_Dimensions._--Diameter of the phacoid shell 0.1, of the medullary shell +0.05; length of the arms 0.15, basal breadth 0.04, distal breadth 0.08. + +_Habitat._--Pacific, central area, Station 266, depth 2750 fathoms; fossil +in Barbados. + + +5. _Astractura hippocratis_, n. sp. + +Phacoid shell three times as broad as the medullary shell, with seven pores +on its radius, surrounded by two to three perfect chambered rings. Arms +nearly square, scarcely as long and nearly as broad as the diameter of the +central disk, at the rounded distal end armed with a very strong, +pyramidal, terminal spine, longer than the arm itself, and at the base as +broad as the medullary shell. + +_Dimensions._--Diameter of the phacoid shell 0.09, of the medullary shell +0.03; length of the arms 0.08, breadth 0.1. + +_Habitat._--Pacific, central area, Station 265, depth 2900 fathoms. + + + +Genus 209. _Stauractura_,[248] Haeckel, 1881, Prodromus, p. 459. + +_Definition._--#Coccodiscida# with four chambered arms on the margin of the +circular or quadrangular disk, crossed in two equatorial diameters, +connected by a spongy patagium. + +The genus _Stauractura_ differs from the foregoing in the patagium between +the arms, and bears therefore the same relation to it as _Histiastrum_ in +the Porodiscida does to _Stauralastrum_. All known species of this genus +form a regular square, if we connect the end points of the arm axes by +lines. + + + +Subgenus 1. _Stauracturium_, Haeckel. + +_Definition._--Distal end of the arms blunt or truncated, without terminal +spines. + + +{478}1. _Stauractura octogona_, n. sp. + +Phacoid shell twice as broad as the medullary shell, with eight pores in +its radius. Arms nearly square, little larger than the phacoid shell, with +broad truncated distal ends. The corners of the latter are so connected by +the complete patagium, that the whole shell forms a regular octagon. + +_Dimensions._--Diameter of the phacoid shell 0.1, of the medullary shell +0.05; length of the arms 0.12, distal breadth 0.11. + +_Habitat._--Pacific, central area, Station 266, depth 2750 fathoms. + + +2. _Stauractura tetragona_, n. sp. + +Phacoid shell three times as broad as the medullary shell, with eleven +pores on its radius. Arms club-shaped, nearly as long as the diameter of +the phacoid shell, and one and a half times as long as broad at the distal +part; at the distal end rounded, blunt, without terminal spine. The +terminal points of the arms are so connected by a thin, complete patagium, +that the whole shell becomes a regular square. + +_Dimensions._--Diameter of the phacoid shell 0.13, of the medullary shell +0.045; length of the arms 0.12, greatest breadth 0.08. + +_Habitat._--Pacific, central area, Station 265, depth 2900 fathoms. + + + +Subgenus 2. _Stauractinium_, Haeckel. + +_Definition._--Distal end of the arms furnished with a radial spine. + + +3. _Stauractura medusina_, n. sp. + +Phacoid shell two and a half times as broad as the medullary shell, with +nine pores on its radius. Arms club-shaped, one and a half times as long as +the diameter of the phacoid shell, and in the outer third nearly as broad +as the latter, at the base scarcely one-third as broad; their truncated +distal end armed with a strong pyramidal terminal spine. Patagium +incomplete, enveloping only the basal half of the arms, with three +rectilinear parallel rows of chambers, forming a square. + +_Dimensions._--Diameter of the phacoid shell 0.1, of the medullary shell +0.04; length of the arms 0.14, greatest breadth 0.08. + +_Habitat._--Pacific, central area, Station 268, depth 2900 fathoms. + + +4. _Stauractura quadrata_, n. sp. + +Phacoid shell twice as broad as the medullary shell, with seven pores on +the radius. Arms nearly square, about as large as the phacoid shell, with a +strong pyramidal terminal spine at the distal end. Patagium complete, +between every two arms triangular, with rectilinear parallel {479}rows of +chambers; it connects the end points of the arm radius in such a manner +that the whole shell becomes a regular square. + +_Dimensions._--Diameter of the phacoid shell 0.09, of the medullary shell +0.045; length of the arms 0.1, greatest breadth 0.08. + +_Habitat._--South Pacific, Station 295, depth 1500 fathoms. + + + +Genus 210. _Pentactura_,[249] Haeckel, 1881, Prodromus, p. 459. + +_Definition._--#Coccodiscida# with five chambered arms on the margin of the +circular or pentagonal disk, without a connecting patagium. + +The genus _Pentactura_ possesses five free radial arms, and resembles +_Pentalastrum_ among the Porodiscida. The distance of the five arms seems +to be sometimes equal, at other times different in one and the same +species. + + +1. _Pentactura pentactis_, Haeckel. + + _Astromma pentactis_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. + Berlin, p. 66, Taf. xxx. fig. 1. + +Phacoid shell two and a half times as broad as the medullary shell, with +eight pores on its radius. Arms regularly or irregularly disposed, nearly +square, about half as large as the phacoid shell, at the truncated distal +end little broader than at the base. In the specimen figured, and very +imperfectly described by Ehrenberg, (_loc. cit._), the arms were +asymmetrically disposed, two opposite in one axis of the disk, two others +on one side of this axis, the fifth opposite to these on the other side. +Another specimen which I found in the Barbados rocks had five arms of equal +size, regularly disposed, at equal intervals. + +_Dimensions._--Diameter of the phacoid shell 0.1, of the medullary shell +0.04; length and breadth of the arms 0.05 to 0.06. + +_Habitat._--Fossil in the rocks of Barbados. + + +2. _Pentactura astropecten_, n. sp. + +Phacoid shell three times as broad as the medullary shell, with ten pores +on its radius. Arms regularly disposed, club-shaped, nearly twice as long +as the diameter of the phacoid shell, and equal to it in breadth at the +rounded distal end. The latter is armed with a short conical spine, and is +twice as broad as the base. + +_Dimensions._--Diameter of the phacoid shell 0.09, of the medullary shell +0.03; length of the arms 0.17, basal breadth 0.05, distal breadth 0.08. + +_Habitat._--Pacific, central area, Station 265, depth 2900 fathoms. + + + +{480}Genus 211. _Echinactura_,[250] n. gen. + +_Definition._--#Coccodiscida# with five chambered arms on the margin of the +circular or pentagonal disk, connected by a spongy patagium. + +The genus _Echinactura_ differs from the foregoing _Pentactura_ in the +patagium between the arms, and bears therefore the same relation to it as +_Pentinastrum_ in the Porodiscida does to _Pentalastrum_. + + +1. _Echinactura culcita_, n. sp. + +Phacoid shell pentagonal, three times as broad as the medullary shell, with +nine pores on its radius. Arms egg-shaped, about as long as the diameter of +the phacoid shell, and in the distal part half as broad. The blunt ends of +the arms are so connected by the complete patagium that the whole shell +becomes a regular pentagonal disk. + +_Dimensions._--Diameter of the phacoid shell 0.1, of the medullary shell +0.035; length of the arms 0.11, basal breadth 0.04, distal breadth 0.06. + +_Habitat._--Pacific, central area, Station 266, depth 2750 fathoms. + + +2. _Echinactura asteriscus_, n. sp. + +Phacoid shell twice as broad as the medullary shell, with seven pores on +its radius. Arms lanceolate, twice as long as the diameter of the phacoid +shell, in the middle part nearly as broad as the latter, at the distal end +with a strong conical terminal spine. Patagium incomplete, enveloping only +the basal half of the arms. + +_Dimensions._--Diameter of the phacoid shell 0.09, of the medullary shell +0.045; length of the arms 0.2, greatest breadth 0.08. + +_Habitat._--Pacific, central area, Station 268, depth 2900 fathoms. + + +3. _Echinactura goniaster_, n. sp. + +Phacoid shell three times as broad as the medullary shell, with nine pores +on its radius. Arms club-shaped, one and a half times as long as the +diameter of the phacoid shell, in the distal part nearly as broad as the +latter, in the basal part one-third as broad; at the end a strong pyramidal +spine. Patagium nearly complete, with concave dentated margin between each +pair of arms, therefore the pentagonal disk of the whole shell with concave +sides. + +_Dimensions._--Diameter of the phacoid shell 0.12, of the medullary shell +0.04; length of the arms (without terminal spine) 0.18, basal breadth 0.04, +distal breadth 0.1. + +_Habitat._--Pacific, central area, Station 265, depth 2900 fathoms. + + + +{481}Family XXI. #PORODISCIDA#, Haeckel (Pls. 41-47). + + _Porodiscida_, Haeckel, 1881, Prodromus, p. 459. + _Trematodiscida_ et _Discospirida_, Haeckel, 1862, Monogr. d. Radiol., + pp. 485, 491, 513. + _Calodictya_, Ehrenberg, 1847, Monatsber. d. k. preuss. Akad. d. Wiss. + Berlin, p. 53 (_partim_). + +_Definition._--#Discoidea# without phacoid shell, with flat discoidal +shell, in which a simple spherical central chamber is surrounded by +concentric chambered rings (each ring divided by radial beams into +imperfect chambers). Surface of the disk on the two flat sides covered by +a porous sieve-plate. + +The family #Porodiscida# is by far the largest and richest in different and +common forms among all #Discoidea#; already in my Monograph (1862) nine +genera and twenty-eight species have been enumerated. Their number is here +increased to more than thirty genera and two hundred species. Many of these +species appertain to the most common and widely distributed SPUMELLARIA, +both living and fossil. But the study of their structure is not easy, and +requires (as in the foregoing Coccodiscida) not only careful examination of +the facial views of the disk, but also of the marginal view and of slides +and sections through different planes. + +In my Monograph (1862, pp. 485, 491, 513) I had constituted for these +#Discoidea# two different families, the Trematodiscida and Discospirida; +but the comparative study of a far greater number of different types in the +Challenger collection has since convinced me that those two families are +but little different, and united by transitional forms within one and the +same genus, so that they must be united as Porodiscida. Of the group, which +Ehrenberg formerly had called "Calodictya," many genera appertain to the +Porodiscida, whilst many others are true Spongodiscida. + +The Porodiscida represent the first and the most important family of the +#Cyclodiscaria#, or of those #Discoidea# which are devoid of the peculiar +extracapsular lenticular "phacoid shell," characteristic of the three +preceding families (united therefore as #Phacodiscaria#). Probably all +#Cyclodiscaria# can be derived from _Archidiscus_, from a morphological as +well as a phylogenetic point of view. _Archidiscus_ seems to be the common +ancestral form not only of the Porodiscida, but also of the nearly allied +Pylodiscida and Spongodiscida. This important _Archidiscus_ (Pl. 48, figs. +9-11) is a small lenticular circular disk, in which a simple latticed +spherical central chamber is surrounded by one single concentric ring, +connected with it by a variable number of radial beams in the equatorial +plane. From this typical _Archidiscus_, as from their "architype," all +other #Cyclodiscaria# may be derived; the Porodiscida by regular apposition +of new concentric chambered rings on the margin, the Spongodiscida by +irregular apposition of a spongy framework, the Pylodiscida by a peculiar +interrupted, concentric, triradial growth, three radial arm-chambers +alternating with three open gates or holes, so that already the first +chambered ring is not complete. + +{482}_Archidiscus_ (Pl. 48, figs. 9-11) is not only the common phylogenetic +ancestral form of all #Cyclodiscaria#, but also the common ontogenetic +original form of all Porodiscida, or at least of the greater part of them. +The numerous species of _Archidiscus_, which are distinguished in the +sequel, are at the same time the embryonic forms of different Porodiscida, +corresponding to the "biogenetic main law of development." The small shell +of _Archidiscus_ is sometimes completely lenticular, circular, at other +times more or less polygonal; commonly on the biconvex centre much thicker +than on the margin, but sometimes also of nearly equal thickness (like a +medal or a short cylinder). The latticed central chamber of it is probably +in the majority of species spherical, but in some more or less compressed, +lenticular; the number of small pores on its surface is probably commonly +between ten and twenty (four to eight usually being visible on each +hemisphere). The number of radial beams, which connect it with the +equatorial ring, varies commonly from four to eight; but sometimes only two +or three are to be found, in other cases nine to ten or more. The regular +disposition of these beams (in certain equatorial axes of the disk) is +probably of great importance, as determining the later development of +characteristic radial appendages of the margin in the more highly developed +Porodiscida. The equatorial ring itself, forming the margin of the +lenticular disk, is either a simple solid ring or a broader latticed +girdle; in the latter case it merges slowly into the opposite sieve-plates +of the two flat disk sides, or the porous "cover-plates," covering its +parallel or convex surfaces. These latter can be regarded as direct +peripheral continuations of the polar regions of the spherical central +chamber. The ring-chambers, surrounding the latter in a single circle, are +commonly of nearly the same breadth, but often also of different irregular +size. Their number varies between two and ten or more, but commonly between +four and eight; each ring-chamber is covered on the upper and lower side by +the sieve-plate, bounded on the inner (proximal) side by the wall of the +central chamber, on the outer (distal) side by the marginal ring, on both +lateral sides by the contiguous neighbouring ring-chambers. + +The important question as to the phylogenetic origin of _Archidiscus_ can +be answered in a twofold way. The most simple form of _Archidiscus_ +(_Archidiscus dioniscus_) can be derived immediately from the +Stylosphaerida, _Saturnalis_ (Pl. 13, fig. 16), only by the development of +lattice-work between the equatorial ring and the two polar faces of the +concentric central chamber (on the surface of the biconvex jelly-mantle). +But on the other hand _Archidiscus_ may also be derived from the simplest +Phacodiscida, _Sethodiscus_ (Pl. 33, figs. 1-3), by the stronger +compression of the biconvex lenticular shell, so that the enclosed +medullary shell on the two poles runs together with the lenticular phacoid +shell, of which only the peripheral part remains free, and thus forms the +chambered ring; this latter explanation seems the more natural in many +cases, as often in the Porodiscida the central chamber is enclosed in one +or two concentric spherical or lenticular lattice-shells. + +{483}The second subfamily of the Porodiscida are the Trematodiscida, which +are derived from the preceding Archidiscida by concentric growth in the +equatorial plane. In the same way in which the simple chambered ring of +_Archidiscus_ is connected by radial beams with the central chamber, so in +_Porodiscus_ a variable number of concentric rings is connected with that +first ring. The number of these concentric rings varies between two and ten +or more, but commonly amounts to between three and five. The radial beams +connecting them are either piercing or interrupted; their number increases +gradually from the centre towards the periphery. The chambers between them +are sometimes more regular, at other times more irregular in size and form. + Their upper and lower wall is formed by the two covering "sieve-plates," +or the porous cover-plates, which are continued from the central disk to +the margin. If these two sieve-plates continue being parallel, the disk +becomes medal-shaped or a short cylinder; if the two plates become more or +less concavely vaulted one against the other, the disk becomes biconvex +lenticular, the middle part thicker than the marginal part. Rarely the +contrary is the case, the margin thicker than the centre, and then the disk +biconcave. + +In my Monograph I had separated as two different subfamilies the true +Trematodiscida (with circular concentric rings) from the Discospirida (with +spirally convoluted rings). But the enormous mass of specimens, which I +afterwards examined in the Challenger collection, has convinced me that +this separation was not natural. For in one and the same genus of most +nearly allied forms we find on one hand quite regular concentric circular +forms (_Trematodiscus_), on the other hand spirally convoluted forms +(_Discospira_), and connecting between them such forms as are in the +central part concentric, in the marginal part spiral (_Perispira_)--or +conversely, these in the centre spiral, on the margin concentric +(_Centrospira_)--and frequently also more or less irregular forms with +interrupted rings (_Atactodiscus_); therefore, all those genera (Prodromus, +1881, Nos. 448-452) have only the value of subgenera of _Porodiscus_. But a +distinct genus is _Perichlamydium_, in which the two sieve-plates run on +the margin of the lens and form a broad hyaline porous or solid girdle. +More important is the distinction of the Ommatodiscida, in which the margin +of the disk exhibits one larger osculum, armed with a corona of spines +(_Ommatodiscus_), or two oscula, opposite on the poles of one axis +(_Stomatodiscus_). Whilst in many Porodiscida all chambers of the +concentric rings lie in one and the same (equatorial) plane, in many others +with further growth they become stratified in floors, and the whole disk is +therefore composed of two to four or more parallel disks, each with a +system of concentric chambered rings or girdles, quite as in the majority +of the Coccodiscida (p. 457). Often the central part of the lenticular +disk becomes thickened by apposition of such floors or strata, whilst the +marginal part remains simple, with one single stratum. The communication +between the chambers of the different strata seems to be the same as in the +similar Coccodiscida. + +Also the margin of the disk exhibits in the Porodiscida the same +characteristic {484}differences as in the foregoing family. In the +subfamily of Stylodictyida it bears a certain number of solid radial +spines, often regularly disposed (as in the Stylocyclida). In the subfamily +of Euchitonida the margin is distinguished by the possession of two to six +or more (commonly three or four) chambered arms, also situated in the plane +of the disk, and of the same structure (sometimes more or less irregular, +spongy). These arms are very variable in size, form, and structure, exhibit +the same peculiarities as in the Astracturida, and are sometimes free, at +other times connected by a "patagium" or an interbrachial spongy skeleton +of different structure, like a web membrane (compare above, p. 458). In +some genera the arms become forked or branched on the distal end. +Sometimes their distal end bears a terminal radial spine. + +_The Central Capsule_ of the Porodiscida assumes generally the form of the +including shell, with or without arms, but is constantly somewhat smaller, +as it remains enclosed by the sieve-plates of the disk surface. Often the +capsule is filled with many coloured oil-globules, disposed regularly in +the chamber rows. The nucleus of it is enclosed by the central chamber, and +in many cases by this and the innermost concentric rings. + +_Synopsis of the Genera of the Porodiscida._ + + ------------------------------------------------------------------------- + I. Section of the Porodiscida--Archidiscaria. + Central chamber of the disk surrounded only by one single chambered + ring. + -------------------- + 1. Subfamily Archidiscida. + Only one single chambered girdle surrounds the central chamber; margin + smooth or spiny. + ------------------------------------------------------------------------- + Margin smooth, without spines, 212. _Archidiscus_. + + Margin armed with radial spines, 213. _Axodiscus_. + + II. Section of the Porodiscida--Astrodiscaria. + + Central chamber of the disk surrounded by two or more (commonly three to + six) concentric chambered rings or radiated girdles. + ------------------------------------------------------------------------- + II. Section of the Porodiscida--Astrodiscaria. + Central chamber of the disk surrounded by two or more (commonly three + to six) concentric chambered rings or radiated girdles. + -------------------- + 2. Subfamily Trematodiscida. + Margin of the disk quite simple, without radial appendages (spines or + chambered arms), without peculiar oscula. + ------------------------------------------------------------------------- + Margin simple, without an equatorial girdle, 214. _Porodiscus_. + + Margin with a thin porous equatorial girdle, 215. _Perichlamydium_. + ------------------------------------------------------------------------- + 3. Subfamily Ommatodiscida. Margin of the disk without chambered arms but + distinguished by one or two large oscula, or wide openings armed with a + crown of spines. + ------------------------------------------------------------------------- + Disk with a single marginal osculum, 216. _Ommatodiscus_. + + Disk with two opposite marginal oscula, 217. _Stomatodiscus_. + ------------------------------------------------------------------------- + 4. Subfamily Stylodictyida. + Margin of the disk without peculiar oscular openings and without + chambered arms, but armed with solid radial spines. + ------------------------------------------------------------------------- + Radial spines of the { Two opposite spines, 218. _Xiphodictya_. + margin two, three, or{ + four, usually quite { Three equidistant + regularly disposed. { spines, 219. _Tripodictya_. + { + { Four crossed spines, 220. _Staurodictya_. + + Radial spines of the { Margin simple, without + margin five or more, { an equatorial girdle, 221. _Stylodictya_. + commonly irregularly { + disposed (generally {Margin with a thin porous + ten to twelve). { equatorial girdle, 222. _Stylochlamydium_. + ------------------------------------------------------------------------- + 5. Subfamily Euchitonida.{485} + Margin of the disk with radial chambered arms (or hollow chambered + appendages), on the distal end of the arms with or without solid + radial spines. + ------------------------------------------------------------------------- + { Two arms { Without a patagium, 223. _Amphibrachium_. + { simple, { + Two arms, { undivided. { With a patagium, 224. _Amphymenium_. + opposite { + in one { Two arms { Without a patagium, 225. _Amphirrhopalum_. + main axis.{ forked (or { + { one simple, { + { other { With a patagium, 226. _Amphicraspedum_. + { forked). { + + { { Regular, 227. _Dictyastrum_. + { { Without a { + Three { Three arms { patagium. { Bilateral, 228. _Rhopalastrum_. + arms { simple, { + (either { undivided. { + regular, { { { Regular, 229. _Hymeniastrum_. + equal, or { { With a { + bilateral,{ { patagium. { Bilateral, 230. _Euchitonia_. + with { { { + unequal { + arms). { { Without a + { { Either { patagium, 231. _Chitonastrum_. + { Three arms {regular or { + { forked. {bilateral. { With a + { { { patagium, 232. _Trigonastrum_. + + Four arms { { { Regular, 233. _Stauralastrum_. + (either { { Without a { + regular, { Four arms { patagium. { Bilateral, 234. _Hagiastrum_. + with four { simple, { + equal { undivided. { { Regular, 235. _Histiastrum_. + crossed { { With a { + arms, or { { patagium. { Bilateral, 236. _Tessarastrum_. + bilateral,{ { + with { { With a terminal + paired { { patagial girdle, 237. _Stephanastrum_ + arms). { + { { Regular, 238. _Dicranastrum_. + { Four arms { Without a { + { forked. { patagium. { Bilateral, 239. _Myelastrum_. + + { Five arms { Without a patagium, 240. _Pentalastrum_. + { simple, { + Five arms { undivided. { With a patagium, 241. _Pentinastrum_. + (equal or { + unequal). { Five arms { Without a patagium, 242. _Pentophiastrum_. + { forked. { + + Six arms { Six arms { Without a patagium, 243. _Hexalastrum_. + (equal or { simple, { + unequal). { undivided. { With a patagium, 244. _Hexinastrum_. + + + +Subfamily 1. ARCHIDISCIDA, Haeckel. + +_Definition._--#Porodiscida# with a simple spherical or lenticular latticed +central chamber, surrounded by a single concentric latticed ring, which is +divided by radial beams into two to six or more radial chambers. + + + +{486}Genus 212. _Archidiscus_,[251] n. gen. + +_Definition._--#Porodiscida# with a simple central chamber, surrounded by a +single concentric ring, which is divided by radial beams into two to six or +more radial chambers, without radial spines on the margin. + +The genus _Archidiscus_ begins the long and polymorphous series of the +#Cyclodiscaria# or of those #Discoidea# which do not possess the peculiar +"phacoid shell" characteristic of the three preceding families, united as +"#Phacodiscaria#." As already mentioned above, both these groups are +probably of independent origin, derived from the #Sphaeroidea# in different +ways (compare pp. 402, 405, &c.). Among all #Cyclodiscaria# _Archidiscus_ +is the most simple, and probably the common ancestral form, from which the +other genera may be derived. + + + +Subgenus 1. _Dioniscus_, Haeckel. + +_Definition._--Ring with two chambers, separated by two radial beams. + + +1. _Archidiscus dioniscus_, n. sp. + +Ring circular, connected with the central chamber by two radial beams, +opposite in one axis, therefore two equal semicircular ring chambers. (This +primitive form has an interesting reference to _Saturnalis_, Pl. 13, fig. +16, and differs from it only in the lattice-work covering both faces of the +lenticular disk, the margin of which forms the ring.) + +_Dimensions._--Diameter of the ring 0.05, of the central chamber 0.016. + +_Habitat._--Central Pacific, Station 271, depth 2425 fathoms. + + +2. _Archidiscus dithalamus_, n. sp. + +Ring roundish, connected with the central chamber by two radial beams, not +opposite in one axis; both semicircular ring chambers more or less unequal, +one of them larger than the other, and sometimes much more prominent. (If +this prominence increase, we can regard it as the beginning of spiral +convolutions, _Discospira_.) + +_Dimensions._--Diameter of the ring 0.06, of the central chamber 0.014. + +_Habitat._--Central Pacific, Station 266, depth 2750 fathoms. + + + +Subgenus 2. _Trioniscus_, Haeckel. + +_Definition._--Ring with three chambers, separated by three radial beams. + + +{487}3. _Archidiscus trioniscus_, n. sp. + +Ring triangular, roundish, equilateral, connected with the central chamber +by three radial beams at equal distances (120d); therefore three equal ring +chambers. (Resembles the central part of the disk of _Tripodictya +trigonaria_, Pl. 42, fig. 8, and may be the ancestral form of it.) + +_Dimensions._--Diameter of the ring 0.04, of the central chamber 0.014. + +_Habitat._--Central Pacific, Station 265, depth 2900 fathoms. + + +4. _Archidiscus trithalamus_, n. sp. + +Ring irregular, roundish, connected with the central chamber by three +radial beams at unequal distances; therefore three ring chambers of +different size. (If these differences be important, they introduce a spiral +convolution in the further development of the _Porodiscus_ arising from +it.) + +_Dimensions._--Diameter of the ring 0.06, of the central chamber 0.016. + +_Habitat._--South Pacific, Station 288, surface. + + + +Subgenus 3. _Tetroniscus_, Haeckel. + +_Definition._--Ring with four chambers, separated by four radial beams. + + +5. _Archidiscus stauroniscus_, n. sp. (Pl. 48, figs. 9, 9_a_). + +Ring regular, square, connected with the central chamber by four radial +beams at equal distances, opposite in pairs in two axes perpendicular one +to another; therefore four equal ring chambers (or congruent quadrants of +the ring). Resembles the central part of the disk of _Staurodictya medusa_, +&c. (Pl. 42, figs. 1-3); also of _Staurodictya gracilis_, Ehrenberg, 1875 +(Abhandl. d. k. Akad. d. Wiss. Berlin, Taf. xxiii. fig. 3). + +_Dimensions._--Diameter of the ring 0.05, of the central chamber 0.016. + +_Habitat._--North Pacific, Station 253, depth 3125 fathoms. + + +6. _Archidiscus tetroniscus_, n. sp. + +Ring elliptical, of rhomboidal fundamental form, connected with the central +chamber by four radial beams, halving the sides of the rhombus and opposite +in pairs in two axes which are not perpendicular one to another; therefore +four ring chambers in pairs different, two opposite equal and larger than +the two others. + +_Dimensions._--Diameter of the ring 0.05 to 0.07, of the central chamber +0.016. + +_Habitat._--Central Pacific, Station 263, depth 2650 fathoms. + + +7. _Archidiscus tetrathalamus_, n. sp. + +Ring irregular, quadrangular, connected with the central chamber by four +radial beams of increasing unequal length; therefore all four ring chambers +of different size, gradually increasing {488}in the following quadrants of +the ring. Important as an ancestral type of such spiral and semi-spiral +forms as _Staurodictya cruciata_ (Pl. 42, figs. 4, 12, &c.) and +_Stylodictya clavata_, _Stylodictya stellata_, &c., of Ehrenberg, 1875 +(Abhandl. d. k. Akad. d. Wiss. Berlin, Taf. xxiii. figs. 2, 7, 8, 9). + +_Dimensions._--Diameter of the ring 0.05 to 0.08, of the central chamber +0.06. + +_Habitat._--South Pacific, Station 295, depth 1500 fathoms. + + + +Subgenus 4. _Pentoniscus_, Haeckel. + +_Definition._--Ring with five chambers, separated by five radial beams. + + +8. _Archidiscus pentoniscus_, n. sp. + +Ring pentagonal or nearly circular, regular, connected with the central +chamber by five radial beams of equal length and at equal distances (72d); +therefore all five chambers of the ring of equal size and similar form. +(Resembles the central part of the disk of _Pentinastrum asteriscus_, Pl. +44, fig. 2.) + +_Dimensions._--Diameter of the ring 0.05, of the central chamber 0.015. + +_Habitat._--North Pacific, Station 244, surface. + + + +Subgenus 5. _Hexoniscus_, Haeckel. + +_Definition._--Ring with six chambers, separated by six radial beams. + + +9. _Archidiscus hexoniscus_, n. sp. (Pl. 48, figs. 10, 10_a_). + +Ring regular, hexagonal, or nearly circular, connected with the central +chamber by six radial beams of equal length and at equal distances (60d); +therefore all six chambers of the same size and form. (Resembles the +central part of the disk of _Hexinastrum geryonidum_, Pl. 44, fig. 4.) + +_Dimensions._--Diameter of the ring 0.06, of the central chamber 0.018. + +_Habitat._--Central Pacific, Station 271, depth 2425 fathoms. + + +10. _Archidiscus pyloniscus_, n. sp. (Pl. 48, figs. 11, 11_a_). + +Ring triangular, connected with the central chamber by six radial beams at +alternating distances; therefore three larger chambers (of looser network) +alternate with three smaller chambers (of denser network); pores of the +former twice to three times as large as those of the latter. This species +is of peculiar importance, as an immediate transitional form to the +Pylodiscida. If these three larger ring chambers lose their few +lattice-beams and so became open gates, we get _Triolene_ or _Triopyle_, +the original forms of the Pylodiscida. + +_Dimensions._--Diameter of the ring 0.05, of the central chamber 0.015. + +_Habitat._--Central Pacific, Station 266, depth 2750 fathoms. + + +{489}11. _Archidiscus hexathalamus_, n. sp. + +Ring irregular, roundish, or hexagonal, connected with the central chamber +by six radial beams of unequal increasing length; therefore all six ring +chambers of gradually increasing size (beginning a spiral convolution, +original form of some _Discospira_). + +_Dimensions._--Diameter of the ring 0.05 to 0.07, of the central chamber +0.014. + +_Habitat._--South Pacific, Station 300, depth 1375 fathoms. + + + +Subgenus 6. _Circoniscus_, Haeckel. + +_Definition._--Ring with seven or more chambers, separated by seven or more +radial beams. + + +12. _Archidiscus octoniscus_, n. sp. + +Ring circular or regular octagonal, connected with the central chamber by +eight equidistant radial beams; therefore eight ring chambers of equal +size. (Compare the central part of the disk of _Porodiscus quadrigatus_, +Pl. 41, fig. 3.) + +_Dimensions._--Diameter of the ring 0.04, of the central chamber 0.014. + +_Habitat._--Central Pacific, Station 268, depth 2900 fathoms. + + +13. _Archidiscus polythalamus_, n. sp. + +Ring circular, connected with the central chamber by nine to ten or more +radial beams at nearly equal distances. Ring chambers nine to ten, more or +less equal, sometimes also eleven to twelve, more different. (This species +is very variable, and may perhaps be divided into a number of different +"transformistic species.") + +_Dimensions._--Diameter of the ring 0.04 to 0.06, of the central chamber +0.015. + +_Habitat._--Central Pacific, Stations 265 to 274, depths 2350 to 2925 +fathoms. + + + +Genus 213. _Axodiscus_,[252] n. sp. + +_Definition._--#Porodiscida# with a simple central chamber, surrounded by +one single concentric ring, which is divided by radial beams into two to +six or more radial chambers; margin of the disk armed with radial spines. + +The genus _Axodiscus_ differs from the preceding _Archidiscus_ only in the +shape of the margin of the small lenticular disk, which is armed with a +variable number of radial spines, indicating certain axes or radii of the +shell. If these marginal spines at certain equal distances from the margin +branch and their distal ends become united by these branches forming a +concentric second ring, the genus passes into _Porodiscus_. The different +number and disposition of the marginal spines are probably very important, +{490}as determining the later development of two to four or more radii in +the different genera of Porodiscida. + + +1. _Axodiscus stylophorus_, n. sp. + +Ring circular, with two equal semicircular chambers, connected with the +central chamber by two opposite radial beams, which are prolonged outside +into two strong conical spines. + +_Dimensions._--Diameter of the ring 0.05, of the central chamber 0.016. + +_Habitat._--Central Pacific, Station 266, depth 2750 fathoms. + + +2. _Axodiscus triradiatus_, n. sp. + +Ring regular, triangular, equilateral, connected with the central chamber +by three equidistant radial beams, which are prolonged outside into three +short conical spines. (Differs from _Archidiscus trioniscus_ in the +possession of marginal spines.) + +_Dimensions._--Diameter of the ring 0.04, of the central chamber 0.013. + +_Habitat._--Central Pacific, Station 267, depth 2700 fathoms. + + +3. _Axodiscus staurophorus_, n. sp. + +Ring regular, square, connected with the central chamber by four radial +beams, which lie opposite in pairs in two perpendicularly crossed axes, and +are prolonged outside into four delicate cylindrical spines. + +_Dimensions._--Diameter of the ring 0.045, of the central chamber 0.015. + +_Habitat._--North Pacific, Station 244, depth 2900 fathoms. + + +4. _Axodiscus hexagonus_, n. sp. + +Ring regular, hexagonal, connected with the central chamber by six radial +beams at equal distances, which are prolonged outside into six strong +pyramidal spines. + +_Dimensions._--Diameter of the ring 0.06, of the central chamber 0.018. + +_Habitat._--Central Pacific, Station 271, depth 2425 fathoms. + + +5. _Axodiscus trigonus_, n. sp. + +Ring regular, triangular, equilateral, connected with the central chamber +by six radial beams of alternating length and distance; therefore three +smaller (perradial) chambers (with denser and darker network) alternating +with three larger (interradial) chambers (with looser and finer network). +On the margin three strong conical radial spines, arising in the radius of +the larger chambers. (Differs from _Archidiscus pyloniscus_, Pl. 48, fig. +11, mainly in the strong angular spines on the three corners of the +triangular shell.) + +_Dimensions._--Diameter of the ring 0.05, of the central chamber 0.014. + +_Habitat._--South Pacific, Station 296, depth 1825 fathoms. + + +{491}6. _Axodiscus octogonus_, n. sp. + +Ring circular or nearly octagonal, connected with the central chamber by +eight radial beams at nearly equal distances, which are prolonged outside +into eight short conical spines. (Differs from _Archidiscus octoniscus_ in +the marginal prolongation of the eight beams.) + +_Dimensions._--Diameter of the ring 0.04, of the central chamber 0.013. + +_Habitat._--Central Pacific, Station 274, depth 2750 fathoms. + + +7. _Axodiscus spinosus_, n. sp. + +Ring circular, connected with the central chamber by ten to twelve radial +beams at nearly equal distances, which are prolonged outside into short +conical spines of variable length. (May be regarded as an aculeate variety +of _Archidiscus polythalamus_.) + +_Dimensions._--Diameter of the ring 0.04 to 0.05, of the central chamber +0.014. + +_Habitat._--Central Pacific, Stations 265 to 274, depths 2350 to 2950 +fathoms. + + + +Subfamily 2. TREMATODISCIDA, Haeckel, 1862, Monogr. d. Radiol., p. 491 +(_sensu emendato et restricto_). + +_Definition._--#Porodiscida# without radial appendages of the disk (solid +spines or chambered arms on the margin), and without peculiar oscula on the +margin of the disk, which is composed of two to four or more concentric +rings. + + + +Genus 214. _Porodiscus_,[253] Haeckel, 1881, Prodromus, p. 459. + +_Definition._--#Porodiscida# with simple circular disk, composed of several +rings (without radial appendages or peculiar oscula on the margin of the +disk). + +The genus _Porodiscus_ is, next to its ancestral form, _Archidiscus_, the +simplest and most primitive form of the Porodiscida, from which all other +genera of this family can be derived. The disk is quite simple, without any +marginal appendages, composed of a variable number of rings, commonly of +circular form, sometimes more or less polygonal, elliptical, or irregular. +In my Monograph (1862, pp. 491, 513) I had separated the species, here +united in _Porodiscus_, into two different genera: _Trematodiscus_ with +concentric rings, and _Discospira_ with spiral rings. But the extended +study of these very common forms in a great number of specimens in the +Challenger collection has convinced me that the separation of those two +genera cannot be maintained. In one and the same locality, where one single +characteristic disk-form is very common, we find intermingled quite regular +disks with only concentric, circular rings (_Trematodiscus_), and other +disks with one single perfect spiral ring (_Discospira_); and between +{492}these a smaller number of specimens, in which the rings of the disk +are partly concentric, partly spiral; either the rings of the central part +of the disk are concentric, the outer spiral (_Perispira_), or the +proportion is inverse (_Centrospira_); and sometimes the whole disposition +of the concentric and spiral rings is irregular, and the rings often +interrupted (_Atactodiscus_). Therefore it appears more natural to give to +all these different forms only the value of subgenera of _Porodiscus_, as I +have already proposed in my Prodromus (1881, p. 459). Even the numerous +species of _Porodiscus_ (mainly characterised by the equal or different +breadth of the rings, and by the number, form, and size of the connecting +radial beams and of the superficial pores) are for the most part very +variable and hard to distinguish, as all those characters are not constant. +_Porodiscus_ is a quite "transformistic genus." + + + +Subgenus 1. _Trematodiscus_, Haeckel, 1860, Monatsber. d. k. preuss. Akad. +d. Wiss. Berlin, p. 841. + +_Definition._--All rings of the disk concentric (commonly circular, rarely +a little elliptical or polygonal). + + +1. _Porodiscus orbiculatus_, Haeckel. + + _Trematodiscus orbiculatus_, Haeckel, 1862, Monogr. d. Radiol., p. 492, + Taf. xxix. fig. 1. + + _Trematodiscus orbiculatus_, Stoehr, 1880, Palaeontogr., vol. xxvi. p. + 108. + +All rings of the disk circular, concentric, of equal breadth, connected by +numerous alternating radial beams. Chambers differing little in size, about +as large as the central chamber. Pores regular, circular, two to two and a +half on the breadth of each ring. + +_Dimensions._--Diameter of the disk (with nine rings) 0.18; breadth of each +ring 0.01; pores 0.003. + +_Habitat._--Cosmopolitan; Mediterranean, Atlantic, Indian, Pacific, +surface; also fossil in Tertiary rocks of Barbados, Sicily, and Nicobar. + + +2. _Porodiscus concentricus_, Haeckel. + + _Trematodiscus concentricus_, Haeckel, 1862, Monogr. d. Radiol., p. 493. + + _Trematodiscus concentricus_, Stoehr, 1880, Palaeontogr., vol. xxvi. p. + 108. + + _Flustrella concentrica_, Ehrenberg, 1838, Abhandl. d. k. Akad. d. Wiss. + Berlin, p. 132; _Ibid._, 1875, p. 72, Taf. xxii. fig. 13. + + ? _Flustrella concentrica_, Ehrenberg, 1854, Mikrogeol., Taf. xix. fig. + 61, Taf. xx. fig. 42, Taf. xxi. fig. 51, Taf. xxxvi. fig. 29. + +All rings of the disk circular, concentric, of equal breadth, connected by +numerous piercing radial beams. Chambers different in size, increasing +from the centre towards the periphery. Pores regular, circular, one and +half to two on the breadth of each ring. + +_Dimensions._--Diameter of the disk (with eight rings) 0.16; breadth of +each ring 0.01; pores 0.003. + +_Habitat._--Fossil in many Tertiary rocks--Barbados, Sicily, Greece, &c. + +_Porodiscus haeckelii_ = _Trematodiscus haeckelii_, Buetschli, 1882, L. N. +41, Taf. xxiv. figs. 5_a_, 5_b_. + + +{493}3. _Porodiscus flustrella_, n. sp. (Pl. 41, fig. 1). + + _Trematodiscus flustrella_, Haeckel, 1866, MS. Canar. Ins. + +All rings of the disk circular, concentric, of equal breadth, connected by +numerous piercing radial beams. Chambers different in size, increasing from +the centre towards the periphery. Pores very irregular, polygonal, or +roundish, one to three on the breadth of each ring. + +_Dimensions._--Diameter of the disk (with six rings) 0.12; breadth of each +ring 0.01; pores 0.002 to 0.006. + +_Habitat._--Cosmopolitan; Atlantic, Pacific, &c., many Stations, surface. + + +4. _Porodiscus sorites_, Haeckel. + + _Trematodiscus sorites_, Haeckel, 1862, Monogr. d. Radiol., p. 492, Taf. + xxix. fig. 2. + +All rings of the disk circular, concentric, of equal breadth, connected by +numerous alternating radial beams. Chambers different in size, increasing +from the centre. Pores regular, circular, one to one and a half on the +breadth of each ring. + +_Dimensions._--Diameter of the disk (with six rings) 0.12; breadth of each +ring 0.01; pores 0.006. + +_Habitat._--Mediterranean (Messina), surface. + + +5. _Porodiscus macroporus_, Haeckel. + + _Trematodiscus macroporus_, Haeckel, 1879, MS. + + _Flustrella macropora_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. + Berlin, p. 160. + +All rings of the disk circular, concentric, of equal breadth, connected by +numerous piercing radial beams. Chambers of different breadth, increasing +from the centre. Pores regular, very large, nearly square, one single pore +on the breadth of each ring. + +_Dimensions._--Diameter of the disk (with five rings) 0.11; breadth of each +ring 0.01; pores 0.005. + +_Habitat._--Fossil in the Tertiary rocks of Barbados. + + +6. _Porodiscus microporus_, Haeckel. + + _Trematodiscus microporus_, Stoehr, 1880, Palaeontogr., vol xxvi. p. 108, + Taf. iv. fig. 17. + +All rings of the disk concentric, either circular or a little elliptical; +the innermost rings of the same breadth as the central chamber, the third +ring much broader. Radial beams between them alternating; chambers of +different size. Pores very small, subregular, everywhere of the same size, +four to five pores on the breadth of each ring. + +_Dimensions._--Diameter of the disk (with three rings) 0.15; breadth of the +inner rings 0.02, of the outer 0.03; pores 0.0016. + +_Habitat._--Fossil in Tertiary rocks of Sicily, Grotte, Stoehr. + + +{494}7. _Porodiscus ellipticus_, Haeckel. + + _Trematodiscus ellipticus_, Stoehr, 1880, Palaeontogr., vol. xxvi. p. + 108, Taf. iv. fig. 16. + +All rings of the disk concentric, either circular or a little elliptical, +connected by eight piercing radial beams; central chamber elliptical, of +the same breadth as the first ring, broader than the following rings, the +breadth of which decreases towards the periphery. Pores irregular, in the +inner rings twice as broad as in the outer (third) ring, four to five on +the breadth of each ring. + +_Dimensions._--Diameter of the disk (with three rings) 0.18; breadth of the +inner rings 0.03, of the outer 0.02; pores 0.003 to 0.006. + +_Habitat._--Fossil in Tertiary rocks of Sicily, Grotte, Stoehr. + + +8. _Porodiscus heterocyclus_, Haeckel. + + _Trematodiscus heterocyclus_, Haeckel, 1862, Monogr. d. Radiol., p. 493, + Taf. xxix. fig. 3. + + ? _Flustrella cyclia_, Harting, 1863, Fauna Banda-Zee, p. 11, pl. i. fig. + 19. + + _Trematodiscus heterocyclus_, Stoehr, 1880, Palaeontogr., vol. xxvi. p. + 108. + +All rings of the disk concentric, circular, connected by numerous radial +beams, which are partly piercing, partly alternating. The breadth of the +rings increases gradually from the centre towards the periphery, +corresponding also to the size of the pores; two to three circular pores on +the breadth of each ring. + +_Dimensions._--Diameter of the disk (with six rings) 0.17; breadth of the +second ring 0.007, of the sixth 0.02; pores 0.002 to 0.006. + +_Habitat._--Cosmopolitan; Mediterranean, Atlantic, Pacific, surface; also +fossil in Tertiary rocks of Barbados and the Mediterranean. + + +9. _Porodiscus quadrigatus_, n. sp. (Pl. 41, fig. 3). + +All rings of the disk concentric, of nearly equal breadth, connected by +four interradial beams, perpendicular one to another. The first ring +(surrounding the central chamber) with eight chambers, the second only with +four (alternating with the four radial beams). Size of the four chambers of +each ring increases much towards the periphery. Pores regular, circular, +about two on the breadth of each ring. + +_Dimensions._--Diameter of the disk (with six rings) 0.18; breadth of each +ring 0.05; pores 0.004. + +_Habitat._--Pacific, central area, Station 271, depth 2425 fathoms. + + + +Subgenus 2. _Perispira_, Haeckel, 1881, Prodromus, p. 459. + +_Definition._--The inner rings of the disk concentric (commonly circular); +the outer rings spirally convoluted. + + +{495}10. _Porodiscus perispira_, n. sp. (Pl. 41, fig. 2). + + _Perispira perforata_, Haeckel, 1881, Prodromus. + +Inner rings of the disk (two or three) concentric, outer rings (three or +four) spirally convoluted, spiral line simple. All rings nearly of the same +breadth, connected by alternating irregular radial beams. Pores irregular, +two to three on the breadth of each ring. + +_Dimensions._--Diameter of the disk (with six rings) 0.17; breadth of each +ring 0.016; pores 0.003 to 0.005. + +_Habitat._--Pacific, central area, Stations 272 to 274, surface. + + +11. _Porodiscus radiatus_, n. sp. + + _Perispira radiata_, Haeckel, 1881, Prodromus. + +Inner rings of the disk (four or five) concentric, outer rings (three or +four) spirally convoluted, spiral line simple. All rings connected by +piercing radial beams (eight in the inner half, sixteen in the outer half). +Breadth of the rings and of the pores increasing from the centre towards +the periphery, three to four pores on the breadth of each ring. + +_Dimensions._--Diameter of the disk (with eight rings) 0.18; breadth of the +second ring 0.006, of the eighth ring 0.02; pores 0.002 to 0.006. + +_Habitat._--South Atlantic, Station 332, depth 2200 fathoms. + + + +Subgenus 3. _Centrospira_, Haeckel, 1881, Prodromus, p. 459. + +_Definition._--The inner rings of the disk spirally convoluted, the outer +rings concentric (commonly circular). + + +12. _Porodiscus centrospira_, n. sp. (Pl. 41, fig. 6). + + _Centrospira perispongidium_, Haeckel, 1881, Prodromus. + +Inner rings of the disk (two or three) spirally convoluted (with simple or +double spiral line), outer rings (three or four) concentric, subcircular. +All rings nearly of the same breadth, connected by alternating radial +beams. Pores subregular, two to three on the breadth of each ring. +Lattice-work in the periphery of the disk a little spongy (as in Pl. 41, +fig. 11). + +_Dimensions._--Diameter of the disk (with five rings) 0.15; breadth of each +ring 0.015; pores 0.003. + +_Habitat._--Pacific, central area, Station 267, depth 2700 fathoms. + + + +Subgenus 4. _Discospira_, Haeckel, 1862, Monogr. d. Radiol., p. 513. + +_Definition._--All rings of the disk spirally convoluted, forming parts of +a simple or double spiral turning. + + +{496}13. _Porodiscus helicoides_, Haeckel. + + _Discospira helicoides_, Haeckel, 1862, Monogr. d. Radiol., p. 514, Taf. + xxix. fig. 7. + + _Trematodiscus helicoides_, Haeckel, 1860, Monatsber. d. k. preuss. Akad. + d. Wiss. Berlin, p. 841. + +All rings of the disk spirally convoluted around the central chamber; +spiral line regular, simple. All rings nearly of the same breadth, +connected by numerous alternating radial beams. Chambers little different +in size, little longer than broad. Pores of equal size, regular, two on the +breadth of each ring. + +_Dimensions._--Diameter of the disk (with ten rings) 0.2; breadth of each +ring 0.01; pores 0.0025. + +_Habitat._--Cosmopolitan; Mediterranean, Atlantic, Pacific; also fossil in +the Tertiary rocks of the Mediterranean, Sicily, Oran, &c. + + +14. _Porodiscus spiralis_, Haeckel. + + _Flustrella spiralis_, Ehrenberg, 1840, Monatsber. d. k. preuss. Akad. d. + Wiss. Berlin, p. 210; Mikrogeol., 1854, Taf. xix. fig. 62. + + _Discospira spiralis_, Haeckel, 1862, Monogr. d. Radiol., p. 513. + +All rings of the disk spirally convoluted around the central chamber; +spiral line regular, simple. All rings nearly of the same breadth, +connected by numerous (twelve to sixteen) piercing radial beams. Chambers +increasing in size from the centre towards the periphery. Pores irregular, +of different size, one and a half to two on the breadth of each ring. + +_Dimensions._--Diameter of the disk (with eight rings) 0.16; breadth of +each ring 0.01; pores 0.004. + +_Habitat._--Cosmopolitan; Mediterranean, Atlantic, Indian, Pacific; also +fossil in the Tertiary rocks of Barbados, Sicily, Greece, &c. + + +15. _Porodiscus operculina_, Haeckel. + + _Discospira operculina_, Haeckel, 1862, Monogr. d. Radiol., p. 514, Taf. + xxix. fig. 8. + +All rings of the disk spirally convoluted around the central chamber, +spiral line regular, simple. Breadth of the rings and length of the +chambers increasing in size from the centre towards the periphery. Most +part of chambers twice as long as broad. Pores irregular, of very different +sizes, two to three on the breadth of each ring. + +_Dimensions._--Diameter of the disk (with six rings) 0.16; breadth of the +rings 0.012 to 0.016; pores 0.002 to 0.006. + +_Habitat._--Mediterranean (Messina), surface. + + +16. _Porodiscus bilix_, Haeckel. + + _Discospira bilix_, Stoehr, 1880, Palaeontogr., vol. xxvi. p. 113, Taf. + vi. fig. 3. + +All rings of the disk spirally convoluted around the large elliptical +central chamber. Spiral convolutions of the inner rings simple, of the +outer rings double; the latter twice as broad as the {497}former. Pores +regular, circular, in the inner rings one pore on the breadth, in the outer +rings two to three pores. Radial beams piercing, numerous, on the margin +prominent. + +_Dimensions._--Diameter of the disk (with six rings) 0.14; breadth of the +inner rings 0.007, of the outer 0.013; pores 0.0017. + +_Habitat._--Fossil in the Tertiary rocks of Sicily, Grotte, Stoehr. + + +17. _Porodiscus bispiralis_, Haeckel. + + _Stylodictya bispiralis_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. + Berlin, p. 160. Taf. xxiv. fig. 1. + +All rings of the disk spirally convoluted, in a perfect double spiral, with +increasing breadth of the rings; the fourth ring twice as broad as the +first. Pores regular, circular; in the inner rings one pore on the breadth, +in the outer rings two to three pores. Radial beams piercing, numerous, +prominent on the margin. + +_Dimensions._--Diameter of the disk (with four rings) 0.1; breadth of the +inner rings 0.006, of the outer 0.012; pores 0.0015. + +_Habitat._--Fossil in the rocks of Barbados; living in the depths of the +Central Pacific, Station 268, depth 2900 fathoms. + + +18. _Porodiscus duplex_, Haeckel. + + _Discospira duplex_, Stoehr, 1880, Palaeontogr., vol. xxvi. p. 114, Taf. + vi. fig. 4. + +All rings of the disk spirally convoluted, in a perfect double spiral, with +increasing breadth of the broad rings. Pores regular, circular; in the +inner rings two to three, in the outer four to five on the breadth. Radial +beams interrupted. Margin of the rings thorny. + +_Dimensions._--Diameter of the disk (with three rings) 0.15; breadth of the +rings 0.02 to 0.04; pores 0.007. + +_Habitat._--Fossil in Tertiary rocks of Sicily, Grotte, Stoehr. + + +19. _Porodiscus semispiralis_, n. sp. (Pl. 41, fig. 4). + +All rings of the disk spirally convoluted, divided by four radial, +perpendicularly crossed and zigzag shaped beams into four quadrants; the +quarter rings of each quadrant halving the rings of each adjacent quarter. +Half spiral line often irregular or partly interrupted. Breadth of all +rings nearly equal. Pores irregular, roundish, two on the breadth of each +ring. Margin of the disk dentated. + +_Dimensions._--Diameter of the disk (with nine rings) 0.22; breadth of each +ring 0.012; pores 0.002 to 0.006. + +_Habitat._--Pacific, central area, Station 272, depth 2600 fathoms. + + + +Subgenus 5. _Atactodiscus_, Haeckel, 1881, Prodromus, p. 459. + +_Definition._--Rings of the disk more or less irregular, partly concentric, +partly spirally convoluted, often interrupted. + + +{498}20. _Porodiscus deformis_, Haeckel. + + _Discospira deformis_, Stoehr, 1880, Palaeontogr., vol. xxvi. p. 114, + Taf. vi. fig. 6. + +Rings of the disk irregular, partly concentric, partly spiral, often +interrupted, increasing in breadth from the centre. Radial beams not +piercing; pores regular, circular, two to six on the breadth of the +different rings. (Very variable and irregular, sometimes more spiral, at +other times more concentric, but always with equal pores.) + +_Dimensions._--Diameter of the disk (with four rings) 0.18; breadth of the +first ring 0.014, of the second 0.03, of the fourth 0.06; pores 0.005. + +_Habitat._--Fossil in the Tertiary rocks of Barbados and Sicily; living in +the Central Pacific, Stations 266 to 268, depths 2700 to 2900 fathoms. + + +21. _Porodiscus irregularis_, n. sp. (Pl. 41, fig. 7). + + _Atactodiscus irregularis_, Haeckel, 1881, Prodromus, p. 459. + + _Perispongidium irregulare_, Haeckel, 1878, MS. et Atlas (pl. xli. fig. + 7). + +Rings of the disk irregular, partly concentric, partly spiral, often +interrupted, with nearly equal breadth. Radial beams not piercing; pores +irregular, roundish, two to four on the breadth of each ring; network in +the periphery of the disk spongy. (Very variable and irregular, sometimes +more spiral, at other times more concentric; disk in the peripheral part +often more or less spongy. Differs from the preceding by the equal breadth +of the rings and the different size of the pores.) + +_Dimensions._--Diameter of the disk (with six rings) 0.15; breadth of each +ring 0.011; pores 0.002 to 0.004. + +_Habitat._--Cosmopolitan; Mediterranean, Atlantic, Pacific, surface; also +fossil in Barbados. + + + +Genus 215. _Perichlamydium_,[254] Ehrenberg, 1847, Monatsber. d. k. preuss. +Akad. d. Wiss. Berlin, p. 54. + +_Definition._--#Porodiscida# with a simple circular disk (without radial +spines and chambered arms), surrounded on the margin by a thin porous (but +not chambered) equatorial girdle. + +The genus _Perichlamydium_ differs from _Porodiscus_ only in the +development of a thin, porous, equatorial girdle, which surrounds the +circular margin of the chambered disk. This girdle lies in the equatorial +plane of the lenticular disk, and represents a very delicate siliceous +plate, perforated by numerous small pores. Sometimes the proximal part of +the girdle is ribbed by thin radial beams, the distal prolongations of the +radial rods of the central disk. If these ribs reach the margin of the +girdle and are prominent over it, _Perichlamydium_ passes over into +_Stylochlamydium_. + + +{499}1. _Perichlamydium praetextum_, Ehrenberg. + + _Perichlamydium praetextum_, Ehrenberg, 1847, Monatsber. d. k. preuss. + Akad. d. Wiss. Berlin, p. 43; Mikrogeol., 1854, Taf. xxii. fig. 21 (non + 20). + + _Perichlamydium praetextum_, Haeckel, 1862, Monogr. d. Radiol., p. 495. + +All rings of the disk (three to four) concentric, circular, of equal +breadth, with interrupted (not piercing) radial beams. Equatorial girdle +without radial beams, nearly as broad as the disk; its circular pores of +the same size as those of the disk; about two pores on the breadth of each +ring. + +_Dimensions._--Diameter of the disk (without the girdle, with four rings) +0.11; breadth of each ring 0.012; breadth of the girdle 0.06 to 0.1; pores +0.004. + +_Habitat._--Cosmopolitan; Atlantic, Indian, Pacific, surface; also fossil +in the Tertiary rocks of Barbados and Sicily. + + +2. _Perichlamydium saturnus_, n. sp. (Pl. 41, fig. 5). + +All rings of the disk (three to four) concentric, circular (sometimes +partly concentric, circular, partly spiral, or irregular), with interrupted +(not piercing) radial beams. Equatorial girdle without radial beams, about +half as broad as the disk; its circular pores very small, scarcely half as +large as those of the disk; about three pores on the breadth of each ring. +(Very variable in the ring-form, differs from the preceding in the small +pores of the girdle.) + +_Dimensions._--Diameter of the disk (without the girdle, with three rings) +0.11; breadth of each ring 0.02, pores 0.004, breadth of the girdle 0.05, +pores 0.002. + +_Habitat._--Pacific, central area, Station 265, depth 2900 fathoms. + + +3. _Perichlamydium accrescens_, Haeckel. + + _Discospira accrescens_, Stoehr, 1880, Palaeontogr., vol. xxvi. p. 114, + Taf. vi. fig. 5. + +All rings of the disk (six to seven) not concentric, convoluted in a simple +spiral, of nearly equal breadth, with interrupted (not piercing) radial +beams. Equatorial girdle in the proximal part with numerous radial beams, +which do not reach its margin; its pores half as large as those of the +disk, where one to two pores arise on the breadth of each ring. (The girdle +becomes twice to three times as broad as in the figure of Stoehr.) + +_Dimensions._--Diameter of the disk (with seven rings, without the girdle) +0.13; breadth of each ring 0.007 to 0.01; pores 0.0036; breadth of the +girdle 0.05, pores of it 0.0017. + +_Habitat._--Fossil in Tertiary rocks of Sicily, Grotte (Stoehr), +Caltanisetta (Haeckel); living in the Central Pacific, Station 266, depth +2750 fathoms. + + +4. _Perichlamydium spirale_, Ehrenberg. + + _Perichlamydium spirale_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. + Berlin, p. 80, Taf. xxii. fig. 12. + +All rings of the disk (three to four) not concentric, convoluted in a +simple spiral, of increasing breadth from the centre; connected by numerous +piercing radial beams. Equatorial girdle about {500}half as broad as the +disk, without radial beams; its pores of the same size as those of the +disk, regular, circular; three pores on the breadth of the first ring, six +pores of the fourth ring. + +_Dimensions._--Diameter of the disk (with four rings, without the girdle) +0.12; breadth of the first ring 0.01, of the fourth 0.02; breadth of the +girdle 0.05; pores 0.003. + +_Habitat._--Fossil in the rocks of Barbados. + + + +Subfamily 3. OMMATODISCIDA, Stoehr, 1880, Palaeontographica, vol. xxvi. p. +115. + +_Definition._--#Porodiscida# without radial appendages of the +concentrically annulated disk, but distinguished by one single or two +opposite large marginal oscula, or wide openings on the margin of the disk, +armed with a coronet of spines. + + + +Genus 216. _Ommatodiscus_,[255] Stoehr, 1880, Palaeontographica, vol. xxvi. +p. 115. + +_Definition._--Porodiscida without chambered arms and radial spines on the +margin of the circular or elliptical disk, but with one large marginal +osculum or opening surrounded by a coronet of spines. + +The genus _Ommatodiscus_, together with the following _Stomatodiscus_, form +the peculiar small subfamily of Ommatodiscida, founded by Stoehr in 1880 +(_loc. cit._). These remarkable Porodiscida, very nearly allied to +_Porodiscus_, are distinguished by one or two large openings on the margin +of the disk, and these "marginal oscula" are constantly armed with a +coronet of spines (comparable to the osculum coronatum of _Sycon_ in the +Calcispongiae). Probably in the living Ommatodiscida the osculum is the +door from which a "sarcode-flagellum" issues (comp. above, p. 407). Perhaps +this osculum is comparable to the peculiar coronet of spines which is +developed on one pole of the shell axis in some Ellipsida (_Lithomespilus_, +_Lithapium_). The internal structure of the disk is commonly more or less +obscure, as the lenticular disk is much thickened, sometimes nearly +ellipsoidal. It is possible that the Ommatodiscida are more nearly related +to the Lithelida than to the Porodiscida; but there is no indication of an +internal trizonal medullary shell. Also the apparent resemblance to the +Cyrtida is of no morphological value; both groups are of quite independent +phylogenetic origin. + + + +Subgenus 1. _Ommatodiscinus_, Haeckel. + +_Definition._--Disk circular. + + +1. _Ommatodiscus decipiens_, Stoehr. + + _Ommatodiscus decipiens_, Stoehr, 1880, Palaeontogr., vol. xxvi. p. 115, + Taf. vi. figs. 8, 8_a._ + +Disk circular, with two chambered rings around the spherical central +chamber, of equal breadth. Chambers twice as high as broad. Pores very +small, one-third as broad as the bars {501}between them, two on the breadth +of each ring. Osculum of the same breadth as the central chamber, +surrounded by numerous very short teeth. + +_Dimensions._--Diameter of the disk 0.12; breadth of the central chamber +and of each ring 0.03; pores 0.0015. + +_Habitat._--Fossil in Tertiary rocks of Sicily, Grotte, Stoehr. + + +2. _Ommatodiscus stoehrii_, n. sp. + +Disk circular with three chambered rings around the spherical central +chamber, of equal breadth. Chambers broader than high. Pores of the same +breadth as the bars between them, four on the breadth of each ring. Osculum +of the same breadth as the central chamber, surrounded by a corona of ten +to twenty thin, bristle-shaped teeth, as long as its diameter. + +_Dimensions._--Diameter of the disk 0.2; breadth of the central chamber and +of each ring 0.03; pores 0.004. + +_Habitat._--North Pacific, Station 244, depth 2900 fathoms. + + +3. _Ommatodiscus circularis_, n. sp. + +Disk circular, with four circular chambered rings around the spherical +central chamber, of increasing breadth; the fourth ring twice as broad as +the second. Chambers about as broad as high. Pores large, twice as broad as +the bars, one to two on the breadth of each ring. Osculum twice as broad as +the central chamber, surrounded by a coronal of strong conical teeth, twice +as long as its diameter. + +_Dimensions._--Diameter of the disk 0.18; breadth of the central chamber +and inner rings 0.015, of the outer rings 0.03; pores 0.01. + +_Habitat._--South Pacific, Station 295, depth 1500 fathoms. + + + +Subgenus 2. _Ommatodisculus_, Haeckel. + +_Definition._--Disk elliptical. + + +4. _Ommatodiscus haeckelii_, Stoehr. + + _Ommatodiscus haeckelii_, Stoehr, 1880, Palaeontogr., vol. xxvi. p. 115, + Taf. vi. figs. 7, 7_a._ + +Disk elliptical (6 : 7), with four chambered rings around the elliptical +central chamber, of equal breadth. Chambers about as high as broad. Pores +small, half as broad as the bars, two on the breadth of each ring. Osculum +three times as broad as the central chamber, surrounded by a crown of +strong conical teeth. + +_Dimensions._--Length of the disk 0.18, breadth 0.16; breadth of each ring +and of the central chamber 0.02; pores 0.003. + +_Habitat._--Fossil in Tertiary rocks of Sicily, Grotte (Stoehr), +Caltanisetta (Haeckel). + + +{502}5. _Ommatodiscus laevigatus_, Stoehr. + + _Ommatodiscus laevigatus_, Stoehr, 1880, Palaeontogr., vol. xxvi. p. 116, + Taf. vi. figs. 9, 9_a._ + +Disk elliptical (3 : 4), with three chambered rings around the circular +central chamber, the third ring half as broad as the second. Chambers twice +as high as broad. Pores very small, one-third as broad as the bars. Osculum +twice as broad as the central chamber, armed with a crown of short conical +teeth. + +_Dimensions._--Length of the disk 0.15, breadth 0.11; breadth of inner +rings 0.02, of the outer 0.01; pores 0.0017. + +_Habitat._--Fossil in Tertiary rocks of Sicily, Grotte, Stoehr. + + +6. _Ommatodiscus fragilis_, Stoehr. + + _Ommatodiscus fragilis_, Stoehr, 1880, Palaeontogr., vol. xxvi. p. 116, + Taf. vi. figs. 10, 10_a._ + +Disk elliptical (4 : 5), with five chambered rings around the elliptical +central chamber, the fifth ring twice as broad as each of the others. +Chambers about as high as broad. Pores very small, one-fifth as broad as +the bars. Osculum three times as broad as the central chamber, surrounded +by a coronet of short teeth. + +_Dimensions._--Length of the disk 0.17, breadth 0.13; breadth of the inner +rings 0.01, of the outer 0.02; pores 0.001. + +_Habitat._--Fossil in Tertiary rocks of Sicily and Barbados; living in +depths of the Tropical Atlantic and Pacific, Station 353, depth 2965 +fathoms, Station 265, depth 2900 fathoms, &c. + + + +Genus 217. _Stomatodiscus_,[256] n. gen. + +_Definition._--#Porodiscida# without chambered arms and radial spines on +the margin of the circular or elliptical disk, but with two large, +opposite, marginal oscula, or openings surrounded by a coronet of spines. + +The genus _Stomatodiscus_ has the same characteristic structure as the +foregoing _Ommatodiscus_, and differs from it only in the duplication of +the large marginal openings. Whilst in the latter there is only one such +marginal osculum, here we find on the margin of the disk two oscula, +opposite on the poles of one equatorial axis. + + +1. _Stomatodiscus amphistomus_, n. sp. + +Disk circular, with three concentric rings of equal breadth around the +central chamber. Pores irregular, roundish, about two on the breadth of +each ring. Surface of the lenticular shell spiny. On two opposite points of +the margin a large osculum, three to four times as broad as the central +chamber, armed with a coronet of strong pyramidal spines of different +length, the longest equal to the radius of the disk. + +{503}_Dimensions._--Diameter of the disk (with three rings) 0.12; breadth +of each ring 0.016; pores 0.004. + +_Habitat._--South Pacific, Station 302, depth 1450 fathoms. + + +2. _Stomatodiscus osculatus_, n. sp. (Pl. 48, fig. 8). + +Disk elliptical, nearly twice as long as broad, with three concentric rings +around the elliptical central chamber, one piercing radial beam in the main +axis, the other beams interrupted. Surface of the shell with small +scattered thorns. Pores very irregular, roundish, partly aggregated in +groups of four to eight smaller porules. On both poles of the main axis a +large elliptical marginal osculum, about as large as the central chamber, +armed with a coronet of short conical spines. + +_Dimensions._--Length of the disk (with three rings) 0.18, breadth 0.1; +pores 0.001 to 0.006. + +_Habitat._--Western Tropical Pacific, Station 225, depth 4475 fathoms. + + + +Subfamily 4. STYLODICTYIDA, Haeckel, 1881, Prodromus, p. 459. + +_Definition._--#Porodiscida# with solid radial spines on the margin of the +concentrically annulated disk, situated in the equatorial plane of the disk +(without chambered arms and marginal oscula). + + + +Genus 218. _Xiphodictya_,[257] Haeckel, 1881, Prodromus, p. 460. + +_Definition._--#Porodiscida# with two opposite, solid, radial spines on the +margin of the circular or elliptical disk. + +The genus _Xiphodictya_ opens the series of the Stylodictyida or of those +Porodiscida in which the margin of the chambered disk is armed with solid +radial spines, all situated in the equatorial plane of the disk. +_Xiphodictya_ exhibits the minimum number of spines, two being opposite on +the poles of one equatorial axis of the disk. It repeats, therefore, in +this family the same amphistylic formation as _Sethostylus_ in the +Phacodiscida and _Stylocyclia_ in the Coccodiscida. + + + +Subgenus 1. _Xiphodictyon_, Haeckel. + +_Definition._--All rings of the disk concentric, circular. + + +1. _Xiphodictya amphibelonia_, n. sp. (Pl. 42, fig. 10). + +All rings of the disk concentric, circular, of equal breadth. Pores +irregular, roundish, one and a half to two on the breadth of each ring. +Margin of the disk thorny, of the same thickness as {504}the central part +of the medal-shaped or cylindrical disk. Two opposite radial spines very +long and thin, cylindrical, twice to three times as long as the diameter of +the disk, only half as thick as the breadth of one ring. + +_Dimensions._--Diameter of the disk (with five rings) 0.17; breadth of each +ring 0.014; pores 0.003 to 0.012. + +_Habitat._--North Pacific, Station 244, depth 2900 fathoms. + + +2. _Xiphodictya amphirrhopalia_, n. sp. (Pl. 42, fig. 11). + +All rings of the disk concentric, circular, with increasing breadth from +the centre; the fifth ring twice as broad as the second. Central chamber +very large. Margin of the lenticular disk thorny, much thinner than the +central part. Pores irregular, roundish, two to three on the breadth of +each ring. Two opposite radial spines club-shaped, about as long as the +diameter of the disk, in the outer spindle-shaped part three to four times +as broad as at the base. + +_Dimensions._--Diameter of the disk (with six rings) 0.17; breadth of the +second ring 0.008, of the fifth ring 0.016. + +_Habitat._--Pacific, central area, Station 265, depth 2900 fathoms; also +fossil in the Tertiary rocks of Sicily (Caltanisetta). + + + +Subgenus 2. _Xiphospira_, Haeckel. + +_Definition._--All rings of the disk or a part of them not concentric, +spirally convoluted; sometimes irregular or interrupted. + + +3. _Xiphodictya staurospira_, n. sp. (Pl. 42, fig. 12). + +All rings of the disk not concentric, half spiral. Four radial beams, +crossed perpendicularly and zigzag-shaped, divide each ring into four +quadrants; the quarter-ring of each quadrant halves the two adjacent rings. +All rings of equal breadth. Pores irregular, roundish, two on the breadth +of each ring. Two opposite radial spines pyramidal, somewhat shorter than +the diameter of the disk. + +_Dimensions._--Diameter of the disk (with six rings) 0.16; breadth of each +ring: 0.014; pores 0.003 to 0.007. + +_Habitat._--South Pacific, Station 295, depth 1500 fathoms. + + +4. _Xiphodictya heliospira_, n. sp. + +All rings of the disk not concentric, convoluted in a simple, regular, +spiral line; all nearly of equal breadth. Pores subregular, circular, two +on the breadth of each ring. Two opposite radial spines conical, about as +long as the radius of the disk. Margin of the disk thorny. (Differs from +_Stylodictya heliospira_, Pl. 41, fig. 8, mainly by the two strong, +opposite, radial spines.) + +{505}_Dimensions._--Diameter of the disk (with six rings) 0.14; breadth of +each ring 0.01 to 0.012; pores 0.002 to 0.006. + +_Habitat._--Pacific, central area, Station 272, depth 2600 fathoms. + + + +Genus 219. _Tripodictya_,[258] Haeckel, 1881, Prodromus, p. 460. + +_Definition._--#Porodiscida# with three solid, equidistant, radial spines +on the margin of the circular or triangular disk. + +The genus _Tripodictya_ exhibits three radial spines on the margin of the +disk, divergent at equal angles; rarely in some specimens the angles differ +more or less. Perhaps this genus bears a near relation to the Dictyastrida +(or to the Euchitonida with three chambered arms--_Dictyastrum_, +_Euchitonia_, &c.). + + +1. _Tripodictya trigonaria_, n. sp. (Pl. 42, fig. 8). + +All rings of the disk concentric, triangular, with three equal convex +sides, all of the same breadth; first and second rings with three simple +chambers, third and fourth rings with six chambers, fifth ring with twelve +chambers. Central chamber also equilateral triangular, from its three +corners arise three piercing perradial beams; from the second ring arise +three interradial beams, alternate with the latter; from the fourth ring +between these and the former arise six adradial beams. Pores subregular, +two on the breadth of each ring. Three marginal spines pyramidal, as long +as the radius of the disk and as broad as one ring. + +_Dimensions._--Diameter of the disk (with five rings) 0.11; breadth of each +ring 0.011; pores 0.004. + +_Habitat._--Pacific, central area, Station 265, depth 2900 fathoms. + + +2. _Tripodictya triacantha_, n. sp. (Pl. 42, fig. 7). + +All rings of the disk concentric, circular, of the some breadth, connected +by very numerous irregular radial beams, the number of which increases +towards the periphery. Pores irregular, roundish, two on the breadth of +each ring. Three marginal spines spindle-shaped, as long as the radius of +the disk, and in the middle part as broad as one ring. + +_Dimensions._--Diameter of the disk (with eight rings) 0.2; breadth of each +ring 0.012; pores 0.004. + +_Habitat._--North Pacific, Station 253, depth 3125 fathoms. + + +3. _Tripodictya tribelonia_, n. sp. (Pl. 42, fig. 9). + +All rings of the disk, or a part of them, not concentric, spirally +convoluted, of equal breadth, connected by numerous irregular, interrupted +radial beams, the number of which increases from the centre. (In one +marginal view of the disk, Pl. 42, fig. 9, the disk seemed to be composed +of seven {506}parallel chambered plates in the central part, and five +similar plates in the peripheral part.) Pores irregular, roundish, three on +the breadth of each ring. Three marginal spines long and thin, cylindrical +(as in _Staurodictya cruciata_, Pl. 42, fig, 4), longer than the diameter +of the disk, and half as thick as one ring. + +_Dimensions._--Diameter of the disk (with nine rings) 0.18; breadth of each +ring 0.01; pores 0.002 to 0.004. + +_Habitat._--Pacific, central area, Station 263, depth 2650 fathoms. + + + +Genus 220. _Staurodictya_,[259] Haeckel, 1881, Prodromus, p. 460. + +_Definition._--#Porodiscida# with four solid radial spines (commonly +crossed at right angles) on the margin of the circular or quadrangular +disk. + +The genus _Staurodictya_ is characterised by four marginal spines, lying +opposite in pairs in two crossed equatorial diameters of the disk, +perpendicular one to another. Sometimes the regular rectangular position of +the spines becomes more or less irregular. Commonly the marginal spines are +the extreme prolongations of four internal crossed radial beams, which are +either rectilinear or zigzag-shaped. In the latter case the concentric +disposition of the circular rings becomes more or less spiral. Perhaps +_Staurodictya_ has a near relation to the Stauralastrida (or to the +Euchitonida with four crossed chambered arms--_Stauralastrum_, +_Histiastrum_, &c.). + + + +Subgenus 1. _Staurodictyon_, Haeckel. + +_Definition._--All rings of the disk concentric (commonly circular, +sometimes with four incisions, produced by two crossed constrictions, or +nearly square). + + +1. _Staurodictya medusa_, n. sp. (Pl. 42, fig. 3). + +All rings of the disk concentric, of nearly equal breadth, divided into +four quadrants by two perradial constrictions (perpendicular one to +another). Pores irregular, roundish, two to three on the breadth of each +ring. Four marginal spines strong, pyramidal, nearly as long as the radius +of the disk. Margin between them denticulated. + +_Dimensions._--Diameter of the disk (with four rings) 0.13; breadth of each +ring 0.015; pores 0.002 to 0.01. + +_Habitat._--North Pacific, Station 244, depth 2900 fathoms. + + +2. _Staurodictya ciliata_, n. sp. (Pl. 42, fig. 2). + +All rings of the disk concentric, of nearly equal breadth, circular or +roundish, without perradial constrictions. Pores subregular, circular, +three to four on the breadth of each ring. Four marginal {507}spines short, +pyramidal, about as long as the breadth of one ring. Margin between them +ciliated, with thin radial bristles. + +_Dimensions._--Diameter of the disk (with four rings) 0.13; breadth of each +ring 0.015; pores 0.0025. + +_Habitat._--South Pacific, Station 295, depth 1500 fathoms. + + +3. _Staurodictya elegans_, n. sp. (Pl. 42, fig. 1). + +All rings of the disk concentric, circular, or roundish, of increasing +breadth towards the margin; the fifth ring twice as broad as the first. +Pores irregular, roundish, two to three on the breadth of each ring. Four +marginal spines very large, conical, with a thin pedicle at the base, +cancellated by ten to twelve deep furrows, about as long as the radius of +the disk and three times as long as broad at the base (above the pedicle). +Margin between them ciliated, with numerous short radial spines. + +_Dimensions._--Diameter of the disk (with six rings) 0.14; breadth of the +inner rings 0.006, of the outer 0.012; pores 0.002 to 0.008. + +_Habitat._--Pacific, central area, Station 272, depth 2600 fathoms. + + +4. _Staurodictya quadrispina_, Haeckel. + + _Stylodictya quadrispina_, Haeckel, 1862, Monogr. d. Radiol., p. 496, + Taf. xxix. fig. 4. + +All rings of the disk concentric, circular, of increasing breadth towards +the margin; the fourth ring twice as broad as the second. Pores irregular, +roundish, two to three on the breadth of each ring. Four marginal spines +short and thin, conical, about as long as the breadth of one ring. Margin +between them smooth. + +_Dimensions._--Diameter of the disk (with six rings) 0.12; breadth of the +inner rings 0.006, of the outer rings 0.012; pores 0.001 to 0.006. + +_Habitat._--Mediterranean, Atlantic (Canary Islands), surface. + + + +Subgenus 2. _Staurospira_, Haeckel. + +_Definition._--All rings of the disk or a part of them not concentric, +spirally convoluted; spiral line simple or double, sometimes half or +irregular, interrupted. + + +5. _Staurodictya cruciata_, n. sp. (Pl. 42, figs. 4, 5). + +All rings of the disk nearly of the same breadth, not concentric, +half-spiral, interrupted by four zigzag-shaped radial beams crossed in two +diameters perpendicular one to another. The quarter ring of each quadrant +halving both neighbouring quarters. Pores irregular, roundish, two on the +breadth of each ring. Pores of the outermost (eighth) ring much smaller +than the others. Four marginal spines cylindrical or nearly spindle-shaped, +thick, about as long as the radius of the disk. Margin between them smooth. + +_Dimensions._--Diameter of the disk (with eight rings) 0.2; breadth of each +ring 0.011; pores 0.004. + +_Habitat._--Pacific, central area, Station 265, depth 2900 fathoms. + + +{508}6. _Staurodictya splendens_, Haeckel. + + _Stylodictya splendens_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. + Berlin, p. 84, Taf. xxiii. fig. 9. + +All rings of the disk nearly of the same breadth, not concentric, +half-spiral, interrupted by four zigzag-shaped perradial beams, crossed in +two diameters. The quarter ring of each quadrant halving both neighbouring +quarters. Pores regular, circular, only one single on the breadth of each +ring. Four marginal spines conical or spear-shaped, about half as long as +the radius of the disk. Margin between them ciliated, with short +bristle-shaped radial spines. + +_Dimensions._--Diameter of the disk (with eight rings) 0.2; breadth of each +ring 0.012; pores 0.004. + +_Habitat._--Fossil in the rocks of Barbados. + + +7. _Staurodictya grandis_, n. sp. + +All rings of the disk (twelve to sixteen) of the same breadth, not +concentric, irregular, partly spiral, interrupted by irregular turnings, +and by ramified radial beams, which divide each ring into numerous square +chambers. Pores subregular, circular, only one single on the breadth of +each ring (and on each chamber). Four marginal spines short and stout, +conical, twice as long as broad at the base, four to five times as long as +the breadth of one ring. Margin between them dentated. + +_Dimensions._--Diameter of the disk (with sixteen rings) 0.3; breadth of +each ring 0.01; pores 0.005. + +_Habitat._--Pacific, central area, Stations 265 to 268, depth 2900 fathoms; +also fossil in the Tertiary rocks of Barbados. + + +8. _Staurodictya ocellata_, Haeckel. + + _Stylodictya ocellata_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. + Berlin, p. 84, Taf. xxiii. fig. 7. + +All rings of the disk irregular, not concentric, half-spiral, interrupted +by four zigzag-shaped, crossed, radial beams; the quarter ring of each +quadrant halving both neighbouring quarters. Breadth of the rings +increasing towards the periphery; the fourth ring twice as broad as the +second. Pores irregular, with increasing size from the centre, three on the +breadth of each ring. Four marginal spines thick and long, cylindrical; +margin between them smooth. + +_Dimensions._--Diameter of the disk (with four rings) 0.1; breadth of the +inner rings 0.01, of the outer 0.02; pores 0.002 to 0.006. + +_Habitat._--Fossil in the rocks of Barbados. + +_Stylodictya haeckelii_, Zittel, 1876, L. N. 29, p. 85, Taf. ii. fig. 9, is +a fossil Cretaceous species, related to _Stylodictya multispina_. + + + +{509}Genus 221. _Stylodictya_,[260] Ehrenberg, 1847, Monatsber. d. k. +preuss. Akad. d. Wiss. Berlin, p. 54. + +_Definition._--#Porodiscida# with numerous (five or more, commonly eight to +twelve) solid radial spines, regularly or irregularly disposed on the +margin of the circular or polygonal disk; margin simple, without a porous +equatorial girdle. + +The genus _Stylodictya_ comprises the majority of this subfamily, in which +the number of the marginal spines exceeds four. Commonly we find eight to +twelve spines, more or less regularly disposed (four perradial and four +interradial, or four perradial and eight adradial); but often also the +number and disposition become irregular (sometimes very large). In my +Monograph (1862 pp. 495, 515) I had separated the concentric disks with +closed circular rings (as true _Stylodictya_, s. str.) from the spiral +disks with convoluted rings (_Stylospira_). But I retain these two groups +here only as two subgenera, as intermediate forms between them are very +common, and often a part of the disk concentric, a part spiral (compare +above, p. 492). + + + +Subgenus 1. _Stylodictyon_, Haeckel, 1862, Monogr. d. Radiol., p. 495. + +_Definition._--All rings of the disk concentric, commonly circular (rarely +a little elliptical or polygonal). + + +1. _Stylodictya gracilis_, Ehrenberg. + + _Stylodictya gracilis_, Ehrenberg, 1854, Mikrogeol., Taf. xxxvi. fig. 28. + + _Stylodictya gracilis_, Ehrenberg, 1873, Monatsber. d. k. preuss. Akad. + d. Wiss. Berlin, p. 257; Abhandl. d. k. Akad. d. Wiss. Berlin, 1875, Taf. + xxiii. fig. 3. + + _Stylodictya gracilis_, Haeckel, 1862, Monogr. d. Radiol., p. 499. + +All rings of the disk concentric, circular, of equal breadth (the first +ring sometimes, but not constantly, four-lobed). Pores regular, circular, +small, three on the breadth of each ring. Four perradial beams (crossed in +two perpendicular diameters) beginning from the circular central chamber, +four interradial beams from the first or second ring (sometimes others +between them). Beams prolonged into eight to twelve (or more) marginal +spines, bristle-shaped, as long as the radius of the shell. + +_Dimensions._--Diameter of the disk (with four rings) 0.12; breadth of each +ring 0.013; pores 0.0025. + +_Habitat._--Fossil in Tertiary rocks of Barbados and Nicobar; living in the +depths of the Pacific and Atlantic. + + +{510}2. _Stylodictya multispina_, Haeckel. + + _Stylodictya multispina_, Haeckel, 1862, Monogr. d. Radiol., p. 496, Taf. + xxix. fig. 5. + + _Stylodictya forbesii_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. + Berlin, p. 160, Taf. xxiii. fig. 6. + +All rings of the disk concentric, circular, of equal breadth. Pores +regular, circular, two and a half to three on the breadth of each ring. +Eight to twelve radial beams beginning from the central chamber, others +from the inner rings. Commonly from the third or fourth ring arise +twenty-four to thirty (sometimes forty or more) piercing beams, which are +prolonged at the margin into bristle-shaped radial spines, as long as the +breadth of two to four rings. + +_Dimensions._--Diameter of the disk (with seven rings) 0.2; breadth of each +ring 0.013; pores 0.004. + +_Habitat._--Cosmopolitan; Mediterranean, Atlantic, Indian, Pacific, surface +and various depths. + + +3. _Stylodictya hastata_, Ehrenberg. + + _Stylodictya hastata_, Ehrenberg, 1873, Monatsber. d. k. preuss. Akad. d. + Wiss. Berlin, p. 257; Abhandl. d. k. Akad. d. Wiss. Berlin, 1875, Taf. + xxiii. fig. 5. + + _Stylodictya gracilis_, Bury, 1862, Polycystins of Barbados, pl. ii. fig. + 1. + +All rings of the disk concentric, circular, of equal breadth. Pores +regular, circular, very small, two on the breadth of each ring. Eight to +twelve marginal spines very large, spear-shaped, sulcated, pyramidal, +nearly as long as the diameter of the disk, with a thin pedicle at the +base, above this as thick as the breadth of one ring. + +_Dimensions._--Diameter of the disk (with five rings) 0.13; breadth of each +ring 0.012; pores 0.003. + +_Habitat._--Fossil in the rocks of Barbados. + + +4. _Stylodictya stellata_, Bailey. + + _Stylodictya stellata_, Bailey, 1856, Amer. Journ., vol. xxii. p. 6, pl. + i. fig. 20. + + _Stylodictya stellata_, Haeckel, 1862, Monogr. d. Radiol., p. 499. + +All rings of the disk concentric, circular, of equal breadth. Pores +regular, circular, very small, two on the breadth of each ring. Marginal +spines fourteen (probably variable in number, twelve to sixteen), very +thick and short, conical; their length seems to be equal to their basal +breadth and to the breadth of one ring. Related to _Stylochlamydium_? + +_Dimensions._--Diameter of the disk (with five rings) 0.11; breadth of each +ring 0.01; pores 0.003. + +_Habitat._--North Pacific, depths of the Kamtschatka Sea, Bailey; Station +241, depth 2300 fathoms. + + +5. _Stylodictya arachnia_, Haeckel. + + _Stylodictya arachnia_, Haeckel, 1862, Monogr. d. Radiol., p. 497. + + _Stylocyclia arachnia_, J. Mueller, 1856, p. 492; Abhandl. d. k. Akad. d. + Wiss. Berlin, 1858, p. 41, Taf. i. figs. 8, 9. + +All rings of the disk concentric, circular, or polygonal; their breadth +increases from the centre towards the periphery, so that the fourth or +fifth ring is twice as broad as the second. Pores {511}subregular, +circular, two on the breadth of each ring. Radial beams partly piercing. +Marginal spines eight to sixteen (commonly twelve), bristle-shaped, very +thin, once to three times as long as the diameter of the disk. (On the +numerous varieties of this common species compare my Monograph, 1862, p. +498.) + +_Dimensions._--Diameter of the disk (with ten rings) 0.22; breadth of the +inner rings 0.004 to 0.008, of the outer 0.012 to 0.015; pores 0.003 to +0.005. + +_Habitat._--Cosmopolitan; Mediterranean, Atlantic, Indian, Pacific, +surface. + + +6. _Stylodictya solmaris_, n. sp. + +All rings of the disk concentric, polygonal, with eight to sixteen rounded +corners; their breadth increases from the centre; eighth ring twice as +broad as the second. Pores subregular circular, large, only one pore on the +breadth of each ring. Twenty to thirty marginal spines, bristle-shaped, +undulating, about as long as (or longer than) the diameter of the disk. + +_Dimensions._--Diameter of the disk (with eight rings) 0.2; breadth of the +inner rings 0.005, of the outer 0.012; pores 0.004 to 0.008. + +_Habitat._--South Atlantic, Station 332, depth 2200 fathoms. + + +7. _Stylodictya octogonia_, n. sp. + +All rings of the disk concentric, increasing in breadth from the centre. +The outer rings (five to eight) regular, octogonal, twice as broad as the +circular inner rings. Pores subregular, circular, two to three on the +breadth of each ring. Eight piercing perradial spines (alternating with the +eight corners of the octogonal rings) bristle-shaped, longer than the +diameter of the disk. + +_Dimensions._--Diameter of the disk (with eight rings) 0.24; breadth of the +inner rings 0.006, of the outer 0.014; pores 0.005 to 0.01. + +_Habitat._--North Atlantic, Station 353, depth 2965 fathoms. + + + +Subgenus 2. _Stylodictula_, Haeckel. + +_Definition._--Rings of the disk partly concentric, completely annular; +partly spiral or interrupted, often irregular. + + +8. _Stylodictya perispira_, n. sp. + +Inner rings of the disk (two to four) concentric, circular, or roundish, +outer rings forming a simple spiral, breadth a little increasing from the +centre. Pores subregular, circular, about two on the breadth of each ring. +Marginal spines bristle-shaped, ten to fifteen, about as long as the +diameter of the disk. + +_Dimensions._--Diameter of the disk (with eight rings) 0.2; breadth of each +ring 0.013; pores 0.004. + +_Habitat._--Pacific, central area, Station 272, depth 2600 fathoms. + + +{512}9. _Stylodictya centrospira_, n. sp. (Pl. 41, fig. 9). + +Inner rings of the disk (three or four) convoluted in a simple or double +spiral, often interrupted or irregular; outer rings (two to three) +concentric, circular, or roundish. Breadth of the rings variable, +irregular. Pores irregular, of very different sizes, in the outer +concentric part twice to four times as large as in the inner spiral part. +Radial beams partly interrupted, partly piercing. Marginal spines fifty to +eighty, very variable in size and number, commonly fifteen to twenty strong +conical spines, twice to three times as long as the ring-breadth, and +numerous (thirty to sixty) smaller spines. Very variable. + +_Dimensions._--Diameter of the disk (with seven rings) 0.2; breadth of the +rings 0.01 to 0.02; pores 0.002 to 0.01. + +_Habitat._--Pacific, central area, Stations 263 to 274, depth 2350 to 2925 +fathoms. + + +10. _Stylodictya setigera_, Ehrenberg. + + _Stylodictya setigera_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. + Berlin, p. 84, Taf. xxiii. fig. 4. + +Inner rings of the disk (two to three) convoluted in a simple or double +spiral, outer rings (two to three) concentric, circular, or roundish. +Breadth of the rings nearly equal. Pores regular, circular, three on the +breadth of each ring. Marginal spines twenty to forty, bristle-shaped, +about twice as long as the ring-breadth. (The specimen figured by Ehrenberg +was a young one; in older specimens I found the inner spiral disk +surrounded by two to three concentric circular rings.) + +_Dimensions._--Diameter of the disk (with six rings) 0.16; breadth of the +rings 0.12; pores 0.003. + +_Habitat._--Fossil in the rocks of Barbados; also living in the depths of +the Central Pacific, Station 266, depth 2750 fathoms. + + + +Subgenus 3. _Stylospira_, Haeckel, 1862, Monogr. d. Radiol., p. 515. + +_Definition._--All rings of the disk convoluted in a simple or double +spiral (sometimes also in quartered half-spirals). + + +11. _Stylodictya heliospira_, n. sp. (Pl. 41, fig. 8). + + _Stylospira heliospira_, Haeckel, 1879, MS. + +All rings of the disk convoluted in a simple regular spiral, increasing in +breadth from the centre towards the periphery; the sixth ring twice as +broad as the second. Pores irregular, roundish, two on the breadth of each +ring. Marginal spines numerous, thirty to forty, bristle-shaped, nearly +half as long as the radius of the disk. + +_Dimensions._--Diameter of the disk (with seven rings) 0.16; breadth of the +inner rings 0.008, of the outer 0.016; pores 0.002 to 0.006. + +_Habitat._--Mediterranean, Portofino near Genoa, surface; also fossil in +the Tertiary rocks of Sicily; Caltanisetta, Haeckel. + + +{513}12. _Stylodictya hertwigii_, Haeckel. + + _Stylospira arachnia_, R. Hertwig, 1879, Organismus d. Radiol., p. 59, + Taf. vi. fig. 8. + +All rings of the disk convoluted in a simple regular spiral, with +increasing breadth from the centre; the fifth ring twice as broad as the +second. Pores regular, circular, two on the breadth of each ring. Twelve +piercing radial beams and some others interrupted, prolonged into twelve to +twenty radial marginal spines, bristle-shaped, about as long as the +diameter of the disk. + +_Dimensions._--Diameter of the disk (with five rings) 0.15; breadth of the +second ring 0.01, of the fifth 0.02; pores 0.006. + +_Habitat._--Mediterranean (Messina), R. Hertwig. + + +13. _Stylodictya dujardinii_, Haeckel. + + _Stylospira dujardinii_, Haeckel, 1862, Monogr. d. Radiol., p. 515, Taf. + xxix. figs. 9, 10. + +All rings of the disk convoluted in a simple regular spiral, of nearly +equal breadth. Pores regular, circular, two on the breadth of each ring. +Very numerous (twenty to thirty or more) piercing radial beams, prolonged +into bristle-shaped marginal spines, about as long as the diameter of the +disk. + +_Dimensions._--Diameter of the disk (with six rings) 0.12; breadth of each +ring 0.01; pores 0.004. + +_Habitat._--Mediterranean (Messina), Haeckel. + + +14. _Stylodictya echinastrum_, Ehrenberg. + + _Stylodictya echinastrum_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. + Berlin, p. 84, Taf. xxiii. fig. 1. + +All rings of the disk convoluted in a double spiral, of nearly equal +breadth. Pores irregular, roundish, two to three on the breadth of each +ring. Marginal spines numerous, twenty to thirty, of very different size, +the largest conical, strong, about as long as the diameter of the disk, and +on the base as broad as one ring. + +_Dimensions._--Diameter of the disk (with five rings) 0.12; breadth of each +ring 0.01; pores 0.002 to 0.006. + +_Habitat._--Fossil in the rocks of Barbados. + + +15. _Stylodictya clavata_, Ehrenberg. + + _Stylodictya clavata_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. + Berlin, p. 84, Taf. xxiii. fig. 2. + +All rings of the disk convoluted in a half spiral, of nearly equal breadth; +each ring by four zigzag beams (crossed in two perpendicular diameters) +divided into four equal quarters; the spiral line of each quarter ring +halving both neighbouring quarters. Pores regular, circular, two on the +breadth of each ring. Eight marginal spines short, conical, with thin +pedicle; four perradial (as {514}prolongations of the four internal beams) +alternating with four interradial spines arising from the margin of the +disk. + +_Dimensions._--Diameter of the disk (with five rings) 0.13; breadth of each +ring 0.014; pores 0.003. + +_Habitat._--Fossil in the rocks of Barbados. + + + +Genus 222. _Stylochlamydium_,[261] Haeckel, 1881, Prodromus, p. 460. + +_Definition._--#Porodiscida# with numerous (five or more, commonly eight to +twelve) solid radial spines, regularly or irregularly disposed on the +margin of the circular or polygonal disk; margin of the disk surrounded by +a thin, porous (but not chambered), equatorial girdle. + +The genus _Stylochlamydium_ is intermediate between _Perichlamydium_ (with +which it was formerly united) and _Stylodictya_. It deals with the former +in the peculiar equatorial girdle, with the latter in the radial spines of +the disk margin, which pierce the girdle. To both these genera it shows +slow transitions, and can hardly be subjected to a sharp definition. + + + +Subgenus 1. _Stylochlamys_, Haeckel. + +_Definition._--All rings of the disk concentric, circular (or somewhat +polygonal). + + +1. _Stylochlamydium asteriscus_, n. sp. (Pl. 41, fig. 10). + + _Perichlamydium asteriscus_, Haeckel, 1879, MS. + +All rings of the disk concentric, circular, or polygonal, with increasing +breadth from the centre; the fifth ring twice as broad as the second. Pores +irregular, roundish, three to four on the breadth of each ring; in the +rings two to six times as large as in the equatorial girdle, which is half +as broad or two-thirds as broad as the radius of the disk. Twelve +bristle-shaped radial spines are connected by the girdle near to the +points; four crossed spines arising from the central chamber; two others +between these in each quadrant arising from the first ring. + +_Dimensions._--Diameter of the disk (with five rings) 0.15, with the girdle +0.25; breadth of the second ring 0.01, of the fifth ring 0.02; pores 0.001 +to 0.005. + +_Habitat._--Pacific, central area, Station 272, depth 2600 fathoms. + + +2. _Stylochlamydium limbatum_, Haeckel. + + _Perichlamydium limbatum_, Ehrenberg, 1847, Monatsber. d. k. preuss. + Akad. d. Wiss. Berlin, p. 43; Mikrogeol., 1854, Taf. xxii. fig. 20. + + _Perichlamydium limbatum_, Haeckel, 1862, Monogr. d. Radiol., p. 494. + +All rings of the disk concentric, circular, of equal breadth. Pores +regular, circular, two on the breadth of each ring; twice to three times as +large as the fine pores of the equatorial girdle, which is {515}about half +as broad as the radius of the disk. Twelve (or eleven) bristle-shaped +radial spines are connected by the girdle near to the points, irregularly +disposed. + +_Dimensions._--Diameter of the disk (with five rings) 0.12, with the girdle +0.2, breadth of each ring 0.01; pores 0.001 to 0.003. + +_Habitat._--Fossil in the Tertiary rocks of Sicily, Caltanisetta, Grotte. + + +3. _Stylochlamydium venustum_, Haeckel. + + _Perichlamydium venustum_, Bailey, 1856, Amer. Journ., vol. xxii. p. 5, + pl. i. figs. 16, 17. + + _Perichlamydium venustum_, Haeckel, 1862, Monogr. d. Radiol., p. 495. + +All rings of the disk concentric, circular, of equal breadth. Pores +regular, circular, everywhere of nearly equal size, three on the breadth of +each ring, a little smaller in the equatorial girdle, which is about as +broad as the radius of the disk. Twenty to twenty-four bristle-shaped +radial spines, irregularly disposed, proceed with their free points over +the margin. + +_Dimensions._--Diameter of the disk (with four rings) 0.1, with the girdle +0.3; breadth of each ring 0.011; pores 0.002. + +_Habitat._--North Pacific, Kamtschatka, Bailey. + + +4. _Stylochlamydium aequale_, Haeckel. + + _Perichlamydium aequale_, Stoehr, 1880, Palaeontogr., vol. xxvi. p. 109, + pl. v. fig. 2. + +All rings of the disk concentric, circular, with increasing breadth from +the centre; the sixth ring twice as broad as the second. Pores regular, +circular, everywhere of equal size; on the breadth of the inner rings one, +of the outer two, of the girdle three pores. Girdle only one-fourth as +broad as the radius of the disk. About twenty bristle-shaped radial spines, +irregularly disposed, are connected by the girdle near to the points. + +_Dimensions._--Diameter of the disk (with six rings) 0.11, with the girdle +0.17; breadth of the second ring 0.006, of the sixth 0.013; pores 0.006. + +_Habitat._--Fossil in Tertiary rocks of Sicily, Grotte, Stoehr. + + + +Subgenus 2. _Stylochlamyum_, Haeckel. + +_Definition._--Rings of the disk all (or in part) not concentric, spirally +convoluted or irregular. + + +5. _Stylochlamydium perispirale_, Haeckel. + + _Perichlamydium limbatum_, var. Stoehr, 1880, Palaeontogr., vol. xxvi. p. + 109, Taf. v. fig. 1. + +Inner rings of the disk concentric, circular, outer rings convoluted +spirally, all rings of equal breadth. Pores regular, circular, two on the +breadth of each ring, twice as large as in the equatorial {516}girdle, +which is about half as broad as the radius of the disk. Twelve to sixteen +bristle-shaped radial spines, irregularly disposed, are connected by the +girdle near to the points. + +_Dimensions._--Diameter of the disk (with six rings) 0.12, with the girdle +0.2; breadth of each ring 0.011; pores in the central disk 0.004, in the +girdle 0.002. + +_Habitat._--Fossil in Tertiary rocks of Sicily, Grotte, Stoehr. + + +6. _Stylochlamydium spongiosum_, Haeckel. + + _Perichlamydium spongiosum_, Stoehr, 1880, Palaeontogr., vol. xxvi, p. + 109, Taf. v. fig. 3. + +Rings of the disk partly concentric, partly spiral, more or less irregular +and often interrupted, with increasing breadth from the centre. Central +part of the disk more or less spongy and obscure. Equatorial girdle half as +broad as the radius of the chambered disk, with smaller pores than the +latter, pierced by twenty to thirty thin, bristle-shaped radial beams, +which proceed over the margin of the disk. + +_Dimensions._--Diameter of the disk (with ten rings) 0.2, with the girdle +0.3; breadth of the rings 0.005 to 0.015; pores 0.001 to 0.005. + +_Habitat._--Pacific, central area, Station 268, depth 2900 fathoms; also +fossil in the Tertiary rocks of Barbados and Sicily. + + + +Subfamily 5. EUCHITONIDA, Haeckel. + +_Definition._--#Porodiscida# with two or more (commonly three or four) +radial chambered or spongy arms on the margin of the concentrically +annulated disk, situated in its equatorial plane (with or without a +connecting patagium between the arms). + + + +Genus 223. _Amphibrachium_,[262] Haeckel, 1881, Prodromus, p. 460. + +_Definition._--#Porodiscida# with two simple, undivided, chambered arms, +opposite in one axis, without a patagium. + +The genus _Amphibrachium_ opens the long series of the Euchitonida, or of +those Porodiscida which bear on the margin of the circular central disk a +certain number of chambered arms, composed of a series of chambers which +are separated by transverse septa. The first group or tribe of this +subfamily is formed by the Amphibrachida, in which the disk bears only two +arms opposite on the poles of one axis. The simplest form of these is +_Amphibrachium_, in which both arms are simple, equal, and without a +patagium or spongy connecticulum. + + + +{517}Subgenus 1. _Amphibrachella_, Haeckel. + +_Definition._--Both arms equal, of the same form and size, blunt at the +distal end, without a terminal spine. + + +1. _Amphibrachium sponguroides_, n. sp. + +Both opposite arms of the same form and size, nearly cylindrical, three +times as long as broad, with six to eight transverse septa or joints, at +the distal end rounded, blunt, without a terminal spine. + +_Dimensions._--Radius of each arm 0.22, breadth 0.065. + +_Habitat._--Antarctic Ocean, Station 154, surface. + + +2. _Amphibrachium lanceolatum_, n. sp. + +Both arms equal, lanceolate, in the middle part three times as broad as at +the two ends, two and a half times as long as broad, with eight to nine +transverse septa, at the distal end blunt, without a terminal spine. + +_Dimensions._--Radius of each arm 0.3, greatest breadth 0.09. + +_Habitat._--Pacific, central area, Station 267, depth 2700 fathoms. + + +3. _Amphibrachium dilatatum_, n. sp. (Pl. 44, fig. 6). + +Both arms equal, trapezoidal, somewhat broader than long, on the convex +distal end three times as broad as on the narrow base, with five to six +transverse septa, without a terminal spine. Central disk large, somewhat +irregular, with three to four rings, twice as broad as the base of the +arms. + +_Dimensions._--Radius of each arm 0.32, basal breadth 0.15, terminal +breadth 0.44. + +_Habitat._--South Atlantic, off Patagonia, Station 319, surface. + + + +Subgenus 2. _Amphibrachidium_, Haeckel. + +_Definition._--Both arms equal, of the same size and form, with terminal +spines. + + +4. _Amphibrachium amphilonche_, n. sp. + +Both arms equal, lanceolate, in the middle part four times as broad as at +the two ends, twice as long as broad; on the distal end of each arm is a +long conical spine. + +_Dimensions._--Radius of each arm (without terminal spine) 0.2, breadth +0.08. + +_Habitat._--Pacific, central area, Station 271, depth 2425 fathoms. + + +{518}5. _Amphibrachium capitatum_, n. sp. + +Both arms equal, club-shaped, three times as long as broad, in the outer +distal half thickened, three times as broad as at the narrow base; on the +distal end of each arm a strong, angular, terminal spine. (The form of the +arms like that of _Stephanastrum capitatum_, Pl. 44, fig. 1.) + +_Dimensions._--Radius of each arm 0.22, basal breadth 0.02, terminal +breadth 0.06. + +_Habitat._--Equatorial Atlantic, Station 347, surface. + + +6. _Amphibrachium armatum_, n. sp. + +Both arms equal, four times as long as broad, in the thickened distal part +twice as broad as at the base, thorny, with twenty to thirty larger spines +on the distal end, and a very large pyramidal spine in the longitudinal +axis. (The form of the arms like that of the odd arm in _Euchitonia +carcinus_, Pl. 43, fig. 10.) + +_Dimensions._--Radius of each arm 0.24, basal breadth 0.03, distal breadth +0.06. + +_Habitat._--North Pacific, Station 244, depth 2900 fathoms. + + + +Subgenus 3. _Amphibrachoma_, Haeckel. + +_Definition._--Both arms of different size or form, without terminal +spines. + + +7. _Amphibrachium indicum_, n. sp. + +Both arms club-shaped, but very different in size and form; larger arm +three times as long and twice as broad as the smaller arm; the larger with +nine joints slowly increasing in size, the smaller with four joints, +rapidly increasing; the terminal joint three times as broad as the basal. +Distal end blunt, rounded, without spines. + +_Dimensions._--Radius of the larger arm 0.24, of the smaller 0.08; distal +breadth of the former 0.06, of the latter 0.03; basal breadth 0.015. + +_Habitat._--Indian Ocean, Ceylon, Haeckel, surface. + + + +Subgenus 4. _Amphibrachura_, Haeckel. + +_Definition._--Both arms of different size or form, with terminal spines. + + +8. _Amphibrachium clavula_, n. sp. + +Both arms different in size and form; larger arm club-shaped, four times as +long as broad, at the distal end three times as broad as at the base, and +twice as long as the smaller arm, which resembles a stalked knob, with thin +basal peduncle and spherical distal part. Ends of the two arms {519}thorny +(with numerous smaller, and three to five larger spines); one very large +conical terminal spine on each pole of the main axis. + +_Dimensions._--Radius of the larger arm 0.3, of the smaller 0.15; distal +breadth of the former 0.06, of the latter 0.04; basal breath 0.02. + +_Habitat._--South Atlantic, Station 333, surface. + + + +Genus 224. _Amphymenium_,[263] Haeckel, 1881, Prodromus, p. 460. + +_Definition._--#Porodiscida# with two simple, undivided, chambered arms, +opposite in one axis, connected by a patagium. + +The genus _Amphymenium_ differs from the preceding _Amphibrachium_, its +ancestral form, by development of a patagium or connecticulum between both +arms. This forms a latticed or more spongy envelop, which surrounds either +the middle part of the shell, or the whole shell with exception of the +distal ends of both arms. If the envelop become very spongy, the shell may +be confounded with the cylindrical Ellipside _Spongocore_ (nearly allied to +_Spongurus_); possibly also _Ommatogramma_ of Ehrenberg belongs to this +genus. + + + +Subgenus 1. _Ommatogramma_, Ehrenberg (?). + +_Definition._--Both opposite arms of the same size and form, blunt, without +terminal spines. + + +1. _Amphymenium pupula_, n. sp. (Pl. 44, fig. 8). + +Both arms equal, twice as long as broad, three-jointed; the terminal joint +egg-shaped, as large as both other joints together; distal end rounded, +blunt. Patagium nearly complete, enveloping the arms with exception of the +distal end. Perimeter nearly spindle-shaped. + +_Dimensions._--Radius of each arm 0.17, greatest breadth 0.06; transverse +breadth of the patagium 0.13. + +_Habitat._--Pacific, central area, Station 273, depth 2350 fathoms. + + +2. _Amphymenium naviculare_, Haeckel. + + ? _Ommatogramma navicularis_, Ehrenberg, 1872, Monatsber. d. k. preuss. + Akad. d. Wiss. Berlin, p. 317; Abhandl. d. k. Akad. d. Wiss. Berlin, Taf. + vi. fig. 7. + +Both arms equal, three times as long as broad, spongy, not jointed; distal +end a little club-shaped, blunt. Patagium nearly complete, enveloping the +arms with exception of the distal end. Perimeter nearly lanceolate. The +imperfect diagnosis and figure of Ehrenberg make it doubtful {520}whether +this species belongs to the Porodiscida (_Amphymenium_) or to the +Spongodiscida (_Spongobrachium_) or perhaps to the Spongurida +(_Spongocore_). + +_Dimensions._--Radius of each arm 0.1, greatest breadth 0.03; transverse +breadth of the patagium 0.05. + +_Habitat._--North Pacific, Californian Sea, depth 2600 fathoms, Ehrenberg. + + +3. _Amphymenium zygartus_, n. sp. (Pl. 44, fig. 7). + +Both arms equal, four times as long as broad, with seven to eight joints, +slowly decreasing in size towards the blunt end. Patagium incomplete, +protecting only the middle part of the shell on both sides; on each side +two parallel lattice-plates, connected by transverse radial beams, +perpendicular to the surface. Perimeter nearly rectilinear. (Resembles much +certain forms of _Zygartus_, Pl. 40, but is a true Discoid, no Prunoid.) +Compare also Pl. 45, fig. 8. + +_Dimensions._--Radius of each arm 0.2, greatest breadth 0.05; transverse +breadth of the patagium 0.11. + +_Habitat._--Pacific, central area, Station 271, surface. + + +4. _Amphymenium monstrosum_, n. sp. (Pl. 44, fig. 11). + +Both arms equal, little longer than broad, with six to seven convex joints. +The axis of both arms is not common and straight, as in all other species +of this genus, but broken, therefore the incomplete patagium, which +envelops only two to three joints of the arms, is on one side convex, on +the other side concave; it is formed by a simple lattice-plate, connected +with the arms by numerous radial beams. This anomalous form, seen only +once, may perhaps be a monstrosity of _Euchitonia_. + +_Dimensions._--Radius of each arm 0.12, greatest breadth 0.06; transverse +breadth of the patagium 0.13. + +_Habitat._--South Pacific, Station 290, surface. + + + +Subgenus 2. _Ommathymenium_, Haeckel. + +_Definition._--Both opposite arms of the same size and form, armed at the +distal end with terminal spines. + + +5. _Amphymenium amphistylium_, n. sp. (Pl. 44, fig. 9). + +Both arms equal, three times as long as broad, thickened towards the +truncated distal end, and armed with a strong pyramidal terminal spine. +Each arm with seven joints, separated by convex, transverse septa, and +halved by a radial beam lying in the longitudinal axis. Patagium +incomplete, cylindrical, enveloping only the middle part of the shell. + +_Dimensions._--Radius of each arm 0.18, greatest breadth 0.06; transverse +breadth of the patagium 0.08. + +_Habitat._--North Atlantic, Station 354, surface. + + +{521}6. _Amphymenium fusiforme_, n. sp. + +Both arms equal, lanceolate, three times as long as broad in the width, +with seven to eight joints. Distal end pointed, armed with a strong conical +terminal spine. Patagium complete, enveloping the whole shell with +exception of the terminal spines. Whole form spindle-shaped. + +_Dimensions._--Radius of each arm 0.2, greatest breadth 0.07; transverse +breadth of the patagium 0.15. + +_Habitat._--South Atlantic, Station 330, surface. + + + +Genus 225. _Amphirrhopalum_,[264] Haeckel, 1881, Prodromus, p. 460. + +_Definition._--#Porodiscida# with two chambered arms, opposite in one axis, +without a patagium; one arm or both forked at the distal end. + +The genus _Amphirrhopalum_ differs from _Amphibrachium_, its ancestral +form, by bifurcation of the distal ends of the arms, which may affect +either both arms, or only one of them. + + + +Subgenus 1. _Amphirrhopalium_, Haeckel. + +_Definition._--Both opposite arms of similar size and form, with blunt +branches, without terminal spines. + + +1. _Amphirrhopalum ximorphum_, n. sp. + +Both arms equal, in the proximal half simple, in the distal half forked, +with six to seven transverse septa; distal end of each branch blunt, +without terminal spine, somewhat broader than the base of the whole arm. +Axis of the branches concavely curved. (Resembles _Amphicraspedum +maclaganium_, Pl. 45, fig. 11, but wants the patagium.) + +_Dimensions._--Radius of the arms 0.18, basal breadth 0.065; terminal +breadth of each branch 0.075. + +_Habitat._--North Pacific, off Japan, Station 240, surface. + + +2. _Amphirrhopalum amphidicranum_, n. sp. + +Both arms equal, in the proximal half simple, in the distal half forked, +with irregular septa; distal end of each arm blunt, without a terminal +spine, smaller than the basal breadth of the arm. Axis of the branches +straight. (Resembles _Dicranastrum furcatum_, Pl. 47, fig. 2, but without +lateral arms.) + +_Dimensions._--Radius of each arm 0.15, basal breadth 0.03; terminal +breadth of each branch 0.02. + +_Habitat._--Pacific, central area, Station 263, depth 2650 fathoms. + + + +{522}Subgenus 2. _Amphirrhopella_, Haeckel. + +_Definition._--Both opposite arms of similar size and form, with terminal +spines. + + +3. _Amphirrhopalum bigeminum_, n. sp. + +Both arms equal, in the proximal larger half simple, in the distal smaller +half forked; each branch triangular, with a strong conical terminal spine. +Axis of the branches straight. (Resembles _Dicranastrum cornutum_, Pl. 45, +fig. 2, but without lateral arms.) + +_Dimensions._--Radius of the arms (without spines) 0.15, basal breadth +0.03; breadth of the bifurcation 0.08. + +_Habitat._--South Pacific, Station 284, surface. + + +4. _Amphirrhopalum echinatum_, n. sp. (Pl. 45, fig. 10). + +Both arms equal, in the proximal smaller half simple, nearly square, in the +distal larger half forked; the branches thorny, armed at the end with +numerous spines, one larger on the terminal pole of the concavely curved +arm-axis. + +_Dimensions._--Radius of the arms (without spines) 0.15, basal breadth +0.05; breadth of branches 0.03. + +_Habitat._--Pacific, central area, Station 266, depth 2750 fathoms. + + + +Subgenus 3. _Amphirrhopoma_, Haeckel. + +_Definition._--Both opposite arms of different size or form, without +terminal spines. + + +5. _Amphirrhopalum ypsilon_, n. sp. + +Both arms very different. Larger arm simple, egg-shaped, twice as long as +broad; smaller arm in the basal half simple, nearly square, in the distal +half forked; both branches egg-shaped, blunt. (Resembles _Amphicraspedum +wyvilleanum_, Pl. 45, fig. 12, but wants the patagium.) + +_Dimensions._--Radius of the larger simple arm 0.18, breadth 0.09; radius +of the smaller forked arm 0.15, breadth of its branches 0.05. + +_Habitat._--Indian Ocean, Madagascar, Rabbe, surface. + + + +Genus 226. _Amphicraspedum_,[265] Haeckel, 1881, Prodromus, p. 460. + +_Definition._--#Porodiscida# with two chambered arms, opposite in one axis, +connected by a lateral patagium; one arm or both forked at the distal end. + +The genus _Amphicraspedum_ exhibits the same bifurcation of the arms as +does _Amphirrhopalum_, but differs from this ancestral form in the +development of a patagium, an external connecticulum between the arms, +which envelops the disk totally or partially. + + + +{523}Subgenus 1. _Amphicraspedon_, Haeckel. + +_Definition._--Both arms of equal size and form, without terminal spines of +the branches. + + +1. _Amphicraspedum maclaganium_, n. sp. (Pl. 45, fig. 11). + +Both arms equal, in the proximal half simple, in the distal half forked, +with six to seven transverse septa; distal end of each branch rounded, +blunt, somewhat broader than the base of the whole arm. Divergent axes of +both branches concavely curved. Patagium incomplete, with elliptical +perimeter, enveloping only the middle part of the shell. I call this +interesting species in honour of Miss Nellie Maclagan, the learned +translator of several zoological papers from German into English. + +_Dimensions._--Radius of each arm 0.25, basal breadth 0.07; distal breadth +of each branch 0.08; equatorial breadth of the patagium 0.25. + +_Habitat._--North Atlantic, off Halifax, Station 50, surface. + + + +Subgenus 2. _Amphicraspedina_, Haeckel. + +_Definition._--Both arms of different size or form, without terminal spines +on the branches. + + +2. _Amphicraspedum wyvilleanum_, n. sp. (Pl. 45, fig. 12). + +Both arms different. Larger arm simple, egg-shaped, with eleven convex +joints, one and a half times as long as broad; smaller arm in the basal +half simple, triangular, with six cap-like joints, in the distal half +forked; both branches egg-shaped, with five joints and blunt ends. Patagium +nearly complete with four to five concave chamber-rows. Called in honour of +Sir C. Wyville Thomson. + +_Dimensions._--Radius of the larger simple arm 0.18, breadth 0.08; radius +of the smaller forked arm 0.16; breadth of the branches 0.05; transverse +breadth of the patagium 0.2. + +_Habitat._--South Atlantic, Station 333, surface. + + + +Subgenus 3. _Amphicraspedula_, Haeckel. + +_Definition._--Both arms of different size or form, with terminal spines of +the branches. + + +3. _Amphicraspedum murrayanum_, n. sp. (Pl. 44, fig. 10). + + _Amphymenium murrayanum_, Haeckel, 1879, MS. et Atlas (pl. xliv. fig. + 10). + +Both arms different in size; the larger one and a half times as long and +broad as the smaller. Both arms triangular, forked at the broader distal +end, with two very strong, conical, divergent, {524}straight terminal +spines. Patagium broad, incomplete, with circular perimeter. Called in +honour of my friend Dr. John Murray. + +_Dimensions._--Radius of the larger arm (including the spines) 0.24, of the +smaller 0.16; distance of the terminal points of the former 0.18, of the +latter 0.09; diameter of the patagium 0.2. + +_Habitat._--North Atlantic, Faeroee Channel, Gulf Stream, surface, John +Murray. + + + +Genus 227. _Dictyastrum_,[266] Ehrenberg, 1860, Monatsber. d. k. preuss. +Akad. d. Wiss. Berlin, p. 830. + +_Definition._--#Porodiscida# with three simple, undivided, chambered arms, +without a patagium; triangular shell regular, with three equal arms and +three equal angles. + +The genus _Dictyastrum_ is the simplest form of the Trigonastrida, or of +the Porodiscida, in which the margin of the central disk is furnished with +three chambered arms. In _Dictyastrum_ these are quite simple and regular, +without a patagium, separated by equal angles, so that the whole shell +represents a regular, equilateral triangle, if we connect the distal points +of the arms by lines. The genus _Dictyastrum_, founded by Ehrenberg in +1860, differs from his _Rhopalodictyum_--after his own diagnosis--only by +an insignificant difference in the form of the simple arms, which is +scarcely a specific character. I therefore apply this name here in the +above amended sense, seeing that the only figured species of Ehrenberg +(_Dictyastrum angulatum_) occurs in two different, but externally very +similar forms: one of these is a true Porodiscid (_Dictyastrum_) with two +porous covering-plates and concentric rings; the other is a true +Spongodiscid (_Rhopalodictyum_) with quite spongy, irregular network, and +is probably identical with the _Rhopalodictyum truncatum_ of Ehrenberg. + + + +Subgenus 1. _Dictyastrella_, Haeckel. + +_Definition._--Arms with blunt ends, without terminal spines. + + +1. _Dictyastrum angulatum_, Ehrenberg. + + _Dictyastrum angulatum_, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. + Berlin, p. 289, Taf. viii. fig. 18. + +Arms nearly square with straight edges, towards the truncated end a little +broader, about the same diameter as the triangular central disk. The figure +of Ehrenberg seems to represent a Spongodiscid (_Rhopalodictyum +angulatum_), but in the same locality (Philippine Sea) occurs also a true +_Dictyastrum_ of quite the same form, but with three to four concentric +rings of the central disk, and with jointed arms. + +{525}_Dimensions._--Radius of each arm (length from the centre to the +distal end) 0.13; breadth of the truncated end 0.1. + +_Habitat._--Tropical Pacific, Philippine Sea, Station 200, depth 250 +fathoms. + + +2. _Dictyastrum bandaicum_, Haeckel. + + _Rhopalastrum bandaicum_, Harting, 1863, Mikr. Fauna Banda-Zee, p. 16, + Taf. iii. fig. 45. + +Arms nearly square, with convex edges, in the middle a little broader than +at both ends, about half the diameter of the central disk. Differs from the +nearly allied preceding species by the half size of the arms and the convex +edges. + +_Dimensions._--Radius of each arm 0.12, its greatest breadth 0.07. + +_Habitat._--Tropical Pacific, Banda Sea, Harting. + + +3. _Dictyastrum hexagonum_, n. sp. (Pl. 43, fig. 7). + + _Rhopalastrum hexagonum_, Haeckel, 1880, Atlas (pl. xliii. fig. 1). + +Arms nearly triangular, one and a third times as broad at the distal end as +long, and three times as broad as at the base. Central disk about the same +diameter. In each arm six simple broad chambers. If we connect the six +corners of the truncated distal ends by straight lines, we get a regular +hexagon. + +_Dimensions._--Radius of each arm 0.17, basal breadth 0.06, terminal +breadth 0.17. + +_Habitat._--Equatorial Atlantic, Station 347, surface. + + +4. _Dictyastrum trirrhopalum_, n. sp. + +Arms club-shaped, five times as long as broad at the base, at the thickened +end three times as broad as at the base. Diameter of the central disk +equals half the length of the arms. (Similar to _Rhopalastrum malleus_, Pl. +43, fig. 1, but with three equal angles and much smaller disk.) + +_Dimensions._--Radius of each arm 0.25, basal breadth 0.04, distal breadth +0.12. + +_Habitat._--Pacific, central area, Station 273, surface. + + + +Subgenus 2. _Dictyastromma_, Haeckel. + +_Definition._--Arms on the distal end provided with terminal spines. + + +5. _Dictyastrum trispinosum_, n. sp. (Pl. 43, fig. 5). + + _Rhopalastrum trispinosum_, Haeckel, 1881, Prodromus et Atlas (pl. xliii. + fig. 5). + +Arms trapezoid, at the rounded distal end twice as broad as at the base, +with a strong and short, conical, terminal spine. Diameter of the circular +central disk about equal to the length and the greatest breadth of the +arms. + +_Dimensions._--Radius of each arm 0.15, basal breadth 0.06, distal breadth +0.11. + +_Habitat._--Equatorial Atlantic, Station 347, surface. + + +{526}6. _Dictyastrum triactis_, Ehrenberg. + + _Dictyastrum triactis_, Ehrenberg, 1872, Monatsber. d. k. preuss. Akad. + d. Wiss. Berlin, p. 306. + +Arms rectilinear, four times as long as broad, with parallel edges, pointed +at the distal end, with a short terminal spine. Diameter of the circular +central disk equal to double the breadth of the arms. + +_Dimensions._--Radius of each arm 0.2, breadth 0.04. + +_Habitat._--Pacific, Philippine Sea, Station 206, depth 2100 fathoms. + + +7. _Dictyastrum aculeatum_, n. sp. + +Arms lanceolate, three times as long as broad, twice as broad in the middle +as at either end, with thorny surface and numerous conical terminal spines, +one very large in the radius. Central disk triangular, about as broad as +the arms. (Resembles _Rhopalastrum arcticum_, Pl. 43, fig. 6, but differs +by the equal angles and the triangular disk.) + +_Dimensions._--Radius of each arm 0.2, breadth 0.06. + +_Habitat._--Western Tropical Pacific, Station 225, depth 4475 fathoms. + + + +Genus 228. _Rhopalastrum_,[267] Ehrenberg, 1847, Monatsber. d. k. preuss. +Akad. d. Wiss. Berlin, p. 54. + +_Definition._--#Porodiscida# with three simple undivided, chambered arms, +without a patagium; triangular shell bilateral, one odd arm opposite to the +odd angle between two paired arms. + +The genus _Rhopalastrum_, founded by Ehrenberg (1847) with a very +insufficient diagnosis, is here retained for those Trigonastrida that agree +in the generic characters with the only species figured by him, viz., +_Rhopalastrum lagenosum_ (compare my Monograph, 1862, p. 500). It +comprises, therefore, such Euchitonida as agree with the preceding +_Dictyastrum_ in the simple form of the three arms and the absence of a +patagium, but differ from it in the different size of the three angles, and +often also in the divergent form and size of the three arms; one odd arm is +opposite to the odd angle between the two paired arms. + + + +Subgenus 1. _Rhopalastrella_, Haeckel. + +_Definition._--Arms with blunt ends, without terminal spines. + + +1. _Rhopalastrum truncatum_, Haeckel. + + _Rhopalastrum truncatum_, Haeckel, 1862, Monogr. d. Radiol., p. 500, Taf. + xxix. fig. 6. + +Distance of both paired arms about half as large as their distance from the +odd arm. All three arms nearly of the same form and size, very short and +broad; their breadth nearly equals that of {527}the roundish central disk, +whilst their length reaches only one-fourth of it. End of the arms convex +rounded, without spines. + +_Dimensions._--Radius of each arm 0.1, breadth 0.15. + +_Habitat._--Mediterranean (Messina), Atlantic (Canary Islands), surface, +Haeckel. + + +2. _Rhopalastrum pistillum_, Stoehr. + + _Rhopalastrum pistillum_, Stoehr, 1880, Palaeontogr., vol. xxvi. p. 110, + Taf. v. fig. 4. + +Distance between the paired arms about two-thirds as large as their +distance from the odd arm. All three arms nearly of the same form and size, +about three times as long as the diameter of the central disk, at the base +one-third as broad as at the convex rounded end, without spines. Stoehr has +only observed a fragment with one arm; some perfect specimens, which I +found in the Caltanisetta-rock, exhibited nearly the same form as +_Rhopalastrum malleus_ (Pl. 43, fig. 1), but differ from this by the +smaller disk, the broader arms, and the smaller angle between the paired +arms. + +_Dimensions._--Radius of all three arms 0.2; basal breadth of each arm +0.045, terminal breadth 0.13. + +_Habitat._--Fossil in Tertiary rocks of Sicily, Grotte (Stoehr), +Caltanisetta (Haeckel). + + +3. _Rhopalastrum malleus_, n. sp. (Pl. 43, fig. 1). + +Distance between the paired arms one and a third times as large as their +distance from the odd arm. All three arms nearly of the same form and size, +hammer-shaped, three times as broad at the truncated distal end as at the +base. Central disk broader than the arms. + +_Dimensions._--Radius of each arm 0.25, basal breadth 0.05, distal breadth +0.15. + +_Habitat._--South Atlantic, Station 325, surface. + + +4. _Rhopalastrum lagenosum_, Ehrenberg. + + _Rhopalastrum lagenosum_, Ehrenberg, 1847, Monatsber. d. k. preuss. Akad. + d. Wiss. Berlin, p. 43; Mikrogeol., 1854, Taf. xxii. fig. 22. + + _Rhopalastrum lagenosum_, Haeckel, 1862, Monogr. d. Radiol., p. 501. + + _Flustrella bilobata_, Ehrenberg, 1844, Monatsber. d. k. preuss. Akad. d. + Wiss. Berlin, p. 81. + + _Haliomma lagena_, Ehrenberg, 1840, Monatsber. d. k. preuss. Akad. d. + Wiss. Berlin, p. 200. + +Distance between the paired arms one and a half times as great as their +distance from the odd arm. All three arms nearly of the same form and size, +about one and a half times as long as the diameter of the central disk, at +the base half as broad as at the convex rounded end, without spines. +Ehrenberg has only observed a fragment with two paired arms; some perfect +specimens with three arms, observed by me, differed from the nearly allied +_Rhopalastrum pistillum_ (from the same locality) by the larger disk, the +broader arms, and the larger unpaired angle. + +_Dimensions._--Radius of all three arms 0.2, basal breadth 0.05, terminal +breadth 0.09. + +_Habitat._--Fossil in Tertiary rocks of Sicily, Caltanisetta. + + +{528}5. _Rhopalastrum ypsilinum_, n. sp. (Pl. 43, fig. 2). + +Distance between the paired arms half as large as their distance from the +odd arm. All three arms at the concavely curved distal end three times as +broad as at the narrow base. Odd arm twice as long and broad as the paired +arms. Central disk smaller than the latter. No terminal spines. + +_Dimensions._--Radius of the odd arm 0.32, of the paired arms 0.2; terminal +breadth of the former 0.2, of the latter 0.12. + +_Habitat._--Indian Ocean, Cocos Islands, Rabbe, surface. + + +6. _Rhopalastrum clavatum_, n. sp. + +Distance between the paired arms half as large as their distance from the +odd arm. All three arms club-shaped, at the thickened, nearly spherical, +distal end three times as broad as at the narrow base. Odd arm nearly twice +as long and broad as the paired arms. Central disk equal to the distal knob +of the latter. No terminal spines. + +_Dimensions._--Radius of the odd arm 0.3, of the paired arms 0.18; distal +breadth of the former 0.16, of the latter 0.08. + +_Habitat._--South Atlantic, Station 332, surface. + + +7. _Rhopalastrum irregulare_, n. sp. (Pl. 43, fig. 8). + +Distance between all three arm-points different. All three arms +cylindrical, nearly of the same length, but of different form, irregularly +curved, about four times as long as broad, with blunt ends. + +_Dimensions._--Length of each arm about 0.2, breadth 0.05. + +_Habitat._--Antarctic Sea, Station 157, depth 1950 fathoms. + + + +Subgenus 2. _Rhopalastromma_, Haeckel. + +_Definition._--Arms on the distal end provided with one or more terminal +spines. + + +8. _Rhopalastrum martellum_, n. sp. + +Distance between all three arm-points nearly the same; but the odd arm is +one and a half times as large as both paired arms, and is perpendicular to +the common axis of the latter, therefore the shell has the form of a +hammer. Each arm is twice as broad at the distal end as at the base, and +armed with a conical terminal spine; the latter is vertical in the odd arm, +horizontal in the paired arms. + +_Dimensions._--Radius of the odd arm 0.3, of the paired arms 0.15; distal +breadth of the former 0.12, of the latter 0.06. + +_Habitat._--North Atlantic, Station 354, surface. + + +{529}9. _Rhopalastrum triceros_, n. sp. (Pl. 43, fig. 4). + +Distance between the paired arms about two-thirds as large as their +distance from the odd arm. All three arms club-shaped, three times as broad +at the thickened distal part as at the base, and armed with one single, +conical, terminal spine. Odd arm of the same breadth, but twice as long as +the paired arms. + +_Dimensions._--Radius of the odd arm 0.35, of the paired arms 0.2; basal +breadth 0.04, distal breadth 0.12. + +_Habitat._--Pacific, central area, Station 274, surface. + + +10. _Rhopalastrum hexaceros_, n. sp. (Pl. 43, fig. 3). + +Distance between the paired arms equals four-fifths of their distance from +the odd arm. All three arms nearly of the same size, about square, a little +broader at the truncated distal end, which is armed at both corners with a +strong, conical, radial spine. + +_Dimensions._--Radius of each arm 0.2, basal breadth 0.1, distal breadth +0.12. + +_Habitat._--Indian Ocean, Ceylon, Belligemma, Haeckel, surface. + + +11. _Rhopalastrum arcticum_, n. sp. (Pl. 43, fig. 6). + +Distance between the paired arms half as large as their distance from the +odd arm, which is a little larger. All three arms of the same form, +lanceolate, twice to three times as long as broad, twice as broad in the +middle as at either end. Each arm with twelve to fourteen transverse septa, +at the distal end with a bunch of conical spines, and one single, very +large, pyramidal, terminal spine. + +_Dimensions._--Radius of each arm (without spine) 0.17, greatest breadth of +it 0.05 to 0.06. + +_Habitat._--Arctic Ocean, lat. 83d 19' N., North Polar expedition of the +"Alert." + + + +Genus 229. _Hymeniastrum_,[268] Ehrenberg, 1847, Monatsber. d. k. preuss. +Akad. d. Wiss. Berlin, p. 54. + +_Definition._--#Porodiscida# with three simple, undivided, chambered arms, +connected by a patagium; triangular shell regular, with three equal arms +and three equal angles. + +The genus _Hymeniastrum_ was founded by Ehrenberg (1847) with a very +incomplete diagnosis, and hitherto known only by one single species, +figured by him as _Hymeniastrum pythagorae_ (Mikrogeol., 1854, Taf. xxxvi. +fig. 31). This form occurs in two different states, externally quite +identical; in one state the central disk (as figured, _loc. cit._), is a +simple lens or hollow disk, containing a medullary shell or "central +chamber"; in the other state the central disk is composed of two concentric +rings surrounding the "central chamber." We retain here the name +_Hymeniastrum_ for this latter state, {530}expressed in the diagnosis given +above, and call the former state (the Coccodiscid) _Hymenactura_ (compare +above, p. 473). One practical advantage, obtained in this way, is that all +genera of #Discoidea# ending with "_-astrum_" belong to the Porodiscida. +_Hymeniastrum_ differs from _Dictyastrum_ by the possession of a patagium, +and from _Euchitonia_ by the equal size of the angles and the arms. + + + +Subgenus 1. _Hymenastrella_, Haeckel. + +_Definition._--Arms with blunt ends, without terminal spines. + + +1. _Hymeniastrum leydigii_, Haeckel. + + _Euchitonia leydigii_, Haeckel, 1862, Monogr. d. Radiol., p. 510, Taf. + xxxi. figs. 4, 5. + + _Hymeniastrum leydigii_, Haeckel, 1881, Prodromus, p. 460. + + _Histiastrum trinacrium_, Haeckel, 1860, Monatsber. d. k. preuss. Akad. + d. Wiss. Berlin, p. 843. + +Arms twice as long as broad, two-thirds as broad at the base as at the +blunt, nearly truncated distal end. Patagium nearly complete, perfectly +filling out the interbrachial spaces, with six to seven regular, concave +chamber-rows; only the truncate terminal faces of the arms free. + +_Dimensions._--Radius of the arms 0.15 to 0.18, breadth on their base 0.04 +to 0.05, on their broadest distal end 0.06 to 0.07. + +_Habitat._--Cosmopolitan; Mediterranean, Atlantic, Pacific, surface. Very +common and variable. + + +2. _Hymeniastrum koellikeri_, Haeckel. + + _Euchitonia koellikeri_, Haeckel, 1862, Monogr. d. Radiol., p. 511, Taf. + xxxi. figs. 6, 7. + + _Hymeniastrum koellikeri_, Haeckel, 1881, Prodromus, p. 460. + +Arms nearly lanceolate, twice as long as broad, half as broad at the base +as at the broadest middle part, pointed at the distal end. Patagium +complete, enveloping the whole triangular disk, with irregular +chamber-rows. + +_Dimensions._--Radius of the arms 0.2, breadth on their base 0.04, on the +broadest part 0.08. + +_Habitat._--Mediterranean (Messina), surface. + + +3. _Hymeniastrum guembelii_, Haeckel. + + _Stylactis guembelii_, Stoehr, 1880, Palaeontogr., vol. xxvi. p. 112, + Taf. vi. fig. 1. + +Arms twice as long as broad, nearly twice as broad in the circular distal +half as in the square proximal half. Patagium incomplete, circular, with +eight to nine convex chamber-rows, enveloping only the proximal square +halves of the arms; the lenticular distal halves remain free. + +_Dimensions._--Radius of the arms 0.14; breadth at the base 0.04, at the +distal lenticular part 0.07. + +_Habitat._--Fossil in the Tertiary rocks of Sicily, Grotte, Stoehr. + + +{531}4. _Hymeniastrum euclidis_, n. sp. (Pl. 43, fig. 13). + + _Euchitonia euclidis_, Haeckel, 1881, Prodromus, p. 460 et Atlas (pl. + xliii. fig. 13). + +Arms one and a half times as long as broad, club-shaped, three times as +broad in the oval distal part as in the narrow square proximal part. +Patagium complete, enveloping the whole triangular disk, and also the +convex ends of the arms, with eight to nine convex chamber-rows. + +_Dimensions._--Radius of the arms 0.18; breadth at the base 0.025, at the +broadest distal part 0.07. + +_Habitat._--Pacific, central area, Stations 270 to 274, surface. + + +5. _Hymeniastrum pythagorae_, Ehrenberg. + + _Hymeniastrum pythagorae_, Ehrenberg, 1854 (_partim_), Mikrogeol., Taf. + xxxvi. fig. 31. + +Arms nearly as broad as long, two-thirds as broad at the base as at the +truncated distal end. Patagium incomplete, enveloping only the basal half +of the arms, with four to five rectilinear parallel chamber-rows. (This +form has the greatest resemblance to the figure given by Ehrenberg, _loc. +cit._, but differs by the central disk, which is composed of two concentric +rings surrounding the small central chamber; compare above _Hymenactura +pythagorae_, p. 474.) + +_Dimensions._--Radius of the arms 0.18; breadth at the base 0.08, at the +truncated end 0.12. + +_Habitat._--Equatorial Atlantic, Station 347, depth 2250 fathoms. + + +6. _Hymeniastrum archimedis_, n. sp. + +Arms nearly triangular, at the truncated, slightly convex end three times +as broad as at the narrow base and one and a third times as broad as long; +each arm with six simple chambers. Patagium incomplete, enveloping only the +basal half of the arms with three to four convex chamber-rows. (Differs +from _Rhopalastrum hexagonum_, Pl. 43, fig. 7, only by the patagium.) + +_Dimensions._--Radius of the arms 0.2; breadth at the base 0.07, at the +truncated end 0.2. + +_Habitat._--Pacific, central area, Station 274, surface. + + + +Subgenus 2. _Hymenastromma_, Haeckel. + +_Definition._--Arms at the distal end provided with radial spines. + + +7. _Hymeniastrum ternarium_, Haeckel. + + _Histiastrum ternarium_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. + Berlin, p. 76, Taf. xxiv. fig. 2. + +Arms two and a half times as long as broad, three times as broad at the +truncated end as at the narrow base, with a strong, conical, radial spine +at the end. Patagium incomplete, enveloping only the basal half of the +arms, with three to four convex chamber-rows. + +_Dimensions._--Radius of the arms (without terminal spine) 0.02; breadth at +the base 0.025, at the broadest terminal part 0.08. + +_Habitat._--Fossil in the rocks of Barbados. + + +{532}8. _Hymeniastrum trigonarium_, n. sp. + +Arms one and a half times as long as broad, a little broader at the rounded +end than at the base, with three strong conical radial spines, one larger +(in the radius of each arm) and two smaller on both sides of this. Patagium +complete, with four to five rectilinear parallel chamber-rows, enveloping +the whole arms (with exception of the terminal spines) and forming a +perfect equilateral triangle. + +_Dimensions._--Radius of the arms (without terminal spines) 0.18; breadth +at the base 0.1, at the distal part 0.12. + +_Habitat._--Pacific, central area, Station 268, depth 2900 fathoms. + + + +Genus 230. _Euchitonia_,[269] Ehrenberg, 1860, Monatsber. d. k. preuss. +Akad. d. Wiss. Berlin, p. 831 (_sensu emendato_). + + +_Definition._--#Porodiscida# with three simple, undivided, chambered arms, +connected by a patagium; triangular shell bilateral, one odd arm opposite +to the odd angle between the two paired arms. + +The genus _Euchitonia_, quite insufficiently characterised by Ehrenberg, +was founded by him (1860) for one single species, afterwards (1872) +described and figured as _Euchitonia furcata_. Retaining this species +correctly as the type of this genus, I give to it here the above diagnosis. +In my Monograph (1862, p. 503) I described seven Mediterranean species of +_Euchitonia_. Three of these have in common the characters according to the +present diagnosis: _Euchitonia muelleri_, _Euchitonia virchowii_, +_Euchitonia beckmanni_; two others appertain (on account of the regular, +not bilateral form) to _Hymeniastrum_, and two others (on account of the +forked, not simple arms) to _Trigonastrum_. Afterwards (1880) three true +fossil species of _Euchitonia_ were described by Stoehr (_Euchitonia +cruciata_, _Euchitonia zittelii_, and _Euchitonia acuta_). Some species of +this genus are cosmopolitan, and appertain to the most common and +everywhere represented #Discoidea#. + + + +Subgenus 1. _Stylactis_, Ehrenberg, 1872 (_loc. cit._). + +_Definition._--Arms with blunt ends, without terminal spines. + + +1. _Euchitonia furcata_, Ehrenberg. + + _Euchitonia furcata_, Ehrenberg, 1872, Monatsber. d. k. preuss. Akad. d. + Wiss. Berlin, p. 308; Abhandl. d. k. Akad. d. Wiss. Berlin, Taf. vi. iii. + fig. 6. + +Distance between the paired arms about half as large as their distance from +the odd arm. All three arms nearly of the same size and form, about twice +as long as broad, one and a half times at the {533}blunt convex end as +broad as at the base. Patagium incomplete, with concave chamber-rows and +irregular network, only enveloping the basal half of the arms. + +_Dimensions._--Radius of all three arms 0.15, basal breadth of each arm +0.04, terminal breadth 0.06. + +_Habitat._--North Pacific, Californian Sea, depth 2600 fathoms, Ehrenberg. + + +2. _Euchitonia muelleri_, Haeckel. + + _Euchitonia muelleri_, Haeckel, 1862, Monogr. d. Radiol., p. 508, Taf. + xxx. figs. 5-10. + + _Euchitonia muelleri_, Stoehr, 1880, Palaeontogr., vol. xxvi. p. 110, + Taf. v. fig. 5. + +Distance between the paired arms about two-thirds as large as their +distance from the odd arm, which is somewhat larger. Length of the arms +equals two and a half times the breadth of the blunt convex end or five +times the breadth of the base. Patagium with concave chamber-rows, nearly +complete, enveloping the arms with exception of the terminal face. (This +common species is very variable; compare my Monograph.) + +_Dimensions._--Radius of all three arms 0.16 to 0.22, basal breadth 0.03 to +0.05, terminal breadth 0.06 to 0.08. + +_Habitat._--Cosmopolitan; one of the most common #Discoidea# in all seas, +on the surface as well as at different depths; also fossil in the Tertiary +rocks of Barbados and Sicily. + + +3. _Euchitonia triangulum_, Haeckel. + + _Stylactis triangulum_, Ehrenberg, 1872, Monatsber. d. k. preuss. Akad. + d. Wiss. Berlin, p. 320; Abhandl. d. k. Akad. d. Wiss. Berlin, Taf. viii. + fig. 9. + + _Stylactis triangulum_, Stoehr, 1880, Palaeontogr., vol. xxvi. p. 113, + Taf. vi. fig. 2. + +Distance between the paired arms about two-thirds as large as their +distance from the odd arm. All three arms nearly of the same size and form, +about one and a half times as long as broad, nearly as broad at the base as +at the blunt rounded end. Patagium incomplete, with convex chamber-rows, +enveloping about two-thirds of the arms. + +_Dimensions._--Radius of all three arms 0.15, basal breadth 0.05, terminal +breadth 0.06. + +_Habitat._--Pacific and Atlantic, Stations 253, 272, 354, surface; also +fossil in the Tertiary rocks of Barbados and Sicily. + + +4. _Euchitonia cruciata_, Stoehr. + + _Euchitonia cruciata_, Stoehr, 1880, Palaeontogr., vol. xxvi. p. 111, + Taf. v. fig. 7. + +Distance between the paired arms about one and a half times as large as +their distance from the odd arm, which is a little larger. Length of the +arm nearly equals twice the breadth, which is the same at the base and at +the rounded blunt ends. Patagium incomplete, with concave chamber-rows, +enveloping only the base of the arms, and forms between them three other +smaller arms; therefore the whole shell forms six angles with six +alternating arms. + +_Dimensions._--Radius of all three arms 0.15, basal breadth 0.05. + +_Habitat._--Fossil in Tertiary rocks of Sicily, Grotte, Stoehr. + + +{534}5. _Euchitonia lanceolata_, n. sp. (Pl. 43, fig. 9). + +Distance between the paired arms about one and a third times as large as +their distance from the odd arm. All three arms nearly of the same size and +form, three times as long as broad, lanceolate, much broader in the middle +part than at both ends; distal end cuspidate, but not spiny. Patagium +incomplete, with convex chamber-rows, envelops about two-thirds of the +arms. + +_Dimensions._--Radius of all three arms 0.18, greatest breadth (in the +width) 0.06. + +_Habitat._--North Atlantic, Station 353, depth 2965 fathoms. + + +6. _Euchitonia zittelii_, Haeckel. + + _Stylactis zittelii_, Stoehr, 1880, Palaeontogr., vol. xxvi. p. 112, Taf. + v. fig. 8. + +Distance between the paired arms about one-fifth as large as their distance +from the odd arm. All three arms nearly of the same size and form, in the +proximal half thinner and nearly square, in the distal half thicker and +circular; the latter half twice to three times as broad as the former. +Patagium incomplete, with convex chamber-rows, envelops only the proximal +square half of the arms. + +_Dimensions._--Radius of all three arms 0.15, basal breadth 0.03, terminal +breadth 0.08. + +_Habitat._--Fossil in Tertiary rocks of Sicily, Grotte, Stoehr. + + +7. _Euchitonia stoehrii_, n. sp. (Pl. 43, fig. 12). + +Distance between the paired arms about four-fifths as large as their +distance from the odd arm, which is one and a half times as long as the +former. Arms about three times as long as broad, twice as broad in the +distal half as in the proximal half, with rounded blunt ends. Patagium +complete, with concave chamber-rows, enveloping the whole shell, also the +ends of the arms. + +_Dimensions._--Radius of the paired arms 0.2, of the odd arm 0.25; basal +breadth 0.03, distal breadth 0.06. + +_Habitat._--Fossil in the rocks of Barbados and of Nicobar Islands, +Haeckel. Indian Ocean, Cocos Islands (Rabbe). Also in the Central Pacific, +Station 267. + + +8. _Euchitonia beckmannii_, Haeckel. + + _Euchitonia beckmannii_, Haeckel, 1862, Monogr. d. Radiol., p. 505, Taf. + xxxi. fig. 1. + +Distance between the paired arms scarcely half as large as their distance +from the odd arm, which is somewhat larger. Each arm with six simple broad +chambers (without radial septa), the terminal chambers semilunar, convex, +blunt, four times as broad as the first (basal) chamber. Patagium +incomplete, with convex chamber-rows, enveloping the arms with exception of +the broad blunt terminal face. + +_Dimensions._--Radius of the paired arms 0.15, of the odd arm 0.18; basal +breadth 0.02 to 0.03, terminal breadth 0.1 to 0.15. + +_Habitat._--Mediterranean (Messina), Haeckel, surface. + + +{535}9. _Euchitonia virchowii_, Haeckel. + + _Euchitonia virchowii_, Haeckel, 1862, Monogr. d. Radiol., p. 503, Taf. + xxx. figs. 1-4. + + _Histiastrum fasciatum_, Haeckel, 1860, Monatsber. d. k. preuss. Akad. d. + Wiss. Berlin, p. 842. + +Distance between the paired arms about half as large as their distance from +the odd arm, which is somewhat larger. Each arm with six broad chambers, +bisected by a radial septum; the terminal chamber convex, blunt, twice as +broad as the basal chamber. Patagium incomplete, with concave chamber-rows, +enveloping the arms with exception of the broad blunt terminal face. + +_Dimensions._--Radius of the paired arms 0.15, of the odd arm 0.16; basal +breadth 0.05, terminal breadth 0.1 to 0.12. + +_Habitat._--Mediterranean (Messina), Atlantic (Canary Islands). + + + +Subgenus 2. _Pteractis_, Ehrenberg, 1872 (_loc. cit._). + +_Definition._--Arms provided with radial spines at the distal end. + + +10. _Euchitonia elegans_, Haeckel. + + _Pteractis elegans_, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. + Berlin, p. 299, Taf. viii. fig. 3. + +Distance between the paired arms half as large as their distance from the +odd arm. This latter is straight, while both the former are concavely +curved towards the middle line. Arms five times as long as broad, at the +distal end pointed and armed with a short conical terminal spine. Patagium +nearly complete, enveloping four-fifths of the arms, with four to five +concave chamber-rows. + +_Dimensions._--Radius of the arms 0.2, breadth of them 0.03. + +_Habitat._--Tropical Pacific, Philippine Sea, depth 3300 fathoms +(Ehrenberg). + + +11. _Euchitonia carcinus_, n. sp. (Pl. 43, fig. 10). + +Distance between the paired arms scarcely one-fourth as great as their +distance from the odd arm. This latter is straight, twice as long as the +former, which are concavely curved towards the middle line. The odd arm is +three times as broad at the distal end as at the narrow base. The end of +each arm is furnished with a strong triangular radial spine and a group of +smaller spines. Patagium incomplete, with two to three concave +chamber-rows, enveloping only the basal half of the arms. + +_Dimensions._--Radius of the paired arms 0.15, breadth 0.03; radius of the +odd arm 0.3, breadth on its base 0.02, on its distal end 0.07. + +_Habitat._--South Atlantic, Station 332, depth 2200 fathoms. + + +{536}12. _Euchitonia acuta_, Stoehr. + + _Euchitonia acuta_, Stoehr, 1880, Palaeontogr., vol. xxvi. p. 111, Taf. + v. fig. 6. + +Distance between the paired arms two-thirds as great as their distance from +the odd arm. All three arms nearly of the same size and form, two and a +half times as long as broad, nearly lanceolate, at their broadest part one +and a half times as broad as at their base. Patagium complete, enveloping +the whole triangular disk, with five to six concave chamber-rows. In the +figure of Stoehr the ends of the arms are simply pointed, while I find in +the same fossil form a short terminal conical spine. + +_Dimensions._--Radius of all three arms 0.14; breadth at the base 0.04, at +the broadest part 0.06. + +_Habitat._--Fossil in Tertiary rocks of Sicily, Grotte (Stoehr), +Caltanisetta (Haeckel). + + +13. _Euchitonia ypsiloides_, Haeckel. + + _Histiastrum ypsiloides_, Haeckel, 1860, Monatsber. d. k. preuss. Akad. + d. Wiss. Berlin, p. 843. + +Distance between the paired arms two-thirds as great as their distance from +the odd arm, which is somewhat larger. Length of the arms equals five times +the breadth of the narrow base, which is half that of the distal end; this +latter is armed with three to five short conical spines. Patagium complete, +with six to seven concave chamber-rows, enveloping the whole arms with the +exception of the terminal spines. (Differs from _Euchitonia muelleri_ +almost solely by the possession of terminal spines.) + +_Dimensions._--Radius of the arms 0.18 to 0.2; breadth at the base 0.04, at +the distal end 0.08. + +_Habitat._--Mediterranean (Messina), Atlantic (Canary Islands), surface. + + +14. _Euchitonia echinata_, n. sp. (Pl. 43, fig. 11). + +Distance between paired arms three-fourths as great as their distance from +the odd arm, which is somewhat larger. Arms one and a half times as long as +broad, somewhat constricted in the middle part, armed at the rounded ends +with numerous (thirty to forty) strong, conical spines. Patagium complete, +with four or five rectilinear parallel chamber-rows, enveloping the whole +of the arms with the exception of the spiny ends. + +_Dimensions._--Radius of the arms (without spines) 0.2, breadth 0.06 to +0.09. + +_Habitat._--North Pacific, Station 253, depth 3125 fathoms. + + + +Genus 231. _Chitonastrum_,[270] Haeckel, 1881, Prodromus, p. 460. + +_Definition._--#Porodiscida# with three forked, chambered arms, without a +patagium. (Arms and angles between them either equal or unequal.) + +The genus _Chitonastrum_ differs from its ancestral form, _Dictyastrum_, by +the bifurcation of the distal ends of the arms. The few species of this +genus are partly {537}regular (like _Dictyastrum_), partly bilateral (like +_Rhopalastrum_). If the number of species increases much, these two +subgenera may be separated into two genera: _Chitonastrella_ corresponding +to the former, _Chitonastromma_ to the latter. + + + +Subgenus 1. _Chitonastrella_, Haeckel. + +_Definition._--All three arms of the same size and form, equidistant; +fundamental form of the shell therefore an equilateral triangle. + + +1. _Chitonastrum triglochin_, n. sp. + +All three arms equal and equidistant. Each arm has the form of an isosceles +triangle, twice as high as broad; the truncated apex of the triangle is +inserted into the large central disk, whilst its distal base (four times as +broad) is divided by a deep incision (half as long as the arm). Each arm +with ten to twelve joints, simple in its basal half, double in its distal +half. Axes of the six branches straight. (Resembles _Trigonastrum +regulare_, Pl. 43, fig. 16, but differs in the absence of a patagium.) + +_Dimensions._--Radius of each arm 0.24, greatest breadth 0.11, basal +breadth 0.03. + +_Habitat._--Pacific, central area, Station 271, depth 2425 fathoms. + + +2. _Chitonastrum bathybium_, n. sp. + +All three arms equal and equidistant, in the basal two-thirds simple, +rectilinear, three times as long as broad, in the distal third forked, both +branches equal, straight, blunt, half as broad as the basal part. + +_Dimensions._--Radius of each arm 0.18, basal breadth 0.04, breadth of the +branches 0.02. + +_Habitat._--Western Tropical Pacific, Station 225, depth 4475 fathoms. + + + +Subgenus 2. _Chitonastromma_, Haeckel. + +_Definition._--One odd arm different in size or form from the two other +arms, which are paired; distance between them different; fundamental form +of the shell therefore a bilateral, isosceles triangle. + + +3. _Chitonastrum jugatum_, n. sp. (Pl. 43, fig. 14). + + _Dictyastrum jugatum_, Haeckel, 1881, Prodromus et Atlas (pl. xliii. fig. + 14). + +Arms very different; odd arm club-shaped, twice as long as broad, at the +blunt distal end twice as broad as at the base; its axis is perpendicular +to the common axis of both paired arms, which are only two-thirds as long, +not so broad, and in the distal half divided into two branches; the +anterior branch is straight, nearly horizontal, the posterior shorter and +curved backwards. + +{538}_Dimensions._--Radius of the odd arm 0.2, of the paired arms 0.15; +distal breadth of the former 0.08, basal breadth 0.04; breadth of the +paired arms 0.04. + +_Habitat._--South Atlantic, Station 325, surface. + + +4. _Chitonastrum dicranoides_, n. sp. + +All three arms in the basal half simple, nearly square, in the distal half +forked; branches straight, blunt. Odd arm twice as large as the paired +arms; angle between the latter larger than the angles between them and the +odd arm. (The form of the arms resembles _Dicranastrum furcatum_, Pl. 47, +fig. 2.) + +_Dimensions._--Radius of the odd arm 0.24, of the paired arms 0.12; basal +breadth 0.06. + +_Habitat._--North Atlantic, Station 353, surface. + + +5. _Chitonastrum lyra_, n. sp. (Pl. 43, fig. 15). + + _Dictyastrum lyra_, Haeckel, 1881, Prodromus et Atlas (pl. xliii. fig. + 15). + +All three arms forked and nearly of the same size, but different in form +and position. The distance between the branches of the two paired arms is +only one-fourth of the distance between them and the odd arm. Each arm in +the basal two-thirds is simple, with eleven to twelve transverse septa, in +the distal third forked, each branch with four to five transverse septa. +The branches of each arm are curved convexly one to another, ending +obtusely. The axis of the simple proximal part is straight in the odd arm, +in the paired arms curved concavely towards the middle line. In the figured +specimen, which I observed living in Portofino (in September 1880), the +central chamber of the central disk and the first surrounding ring were +filled with the nucleus of the cell; both external rings were filled (like +all chambers of the arms) with pink oil-globules of the red central +capsule. From the mantle, enveloping the shell, radiated innumerable fine +pseudopodia (much too short in the figure), and between the two paired arms +a long "sarcode-flagellum." + +_Dimensions._--Radius of each arm 0.16; greatest breadth of the odd arm +0.04; basal breadth of the paired arms 0.02; distance of both branches of +each arm 0.08. + +_Habitat._--Mediterranean, Portofino, near Genoa, Haeckel. + + + +Genus 232. _Trigonastrum_,[271] n. gen. + +_Definition._--#Porodiscida# with three forked, chambered arms, connected +by a patagium. (Arms and angles between them either equal or unequal.) + +The genus _Trigonastrum_ differs from the preceding _Chitonastrum_, its +ancestral form, in the development of a patagium between the arms. It bears +therefore to the latter the same relation that _Euchitonia_ does to +_Rhopalastrum_. + + + +{539}Subgenus 1. _Trigonastrella_, Haeckel. + +_Definition._--All three arms of the same size and form, equidistant; +fundamental form of the shell therefore a regular, equilateral triangle. + + +1. _Trigonastrum regulare_, n. sp. (Pl. 43, fig. 16). + + _Chitonastrum regulare_, Haeckel, 1881, Prodromus et Atlas (pl. xliii. + fig. 16). + +All three arms equal and equidistant. Each arm has the form of an isosceles +triangle, twice as high as broad, the truncated apex of which is inserted +into the large circular central disk, whilst its distal base (four times as +broad) is divided by a deep incision (half as long as the arm). Each arm +with ten to twelve joints. Patagium between the arms nearly complete, +spongy. (Differs from _Chitonastrum triglochin_ mainly in the possession of +a patagium.) + +_Dimensions._--Radius of each arm 0.24, greatest breadth 0.11, basal +breadth 0.03; length of the sides of the regular triangle 0.45. + +_Habitat._--Pacific, central area, Station 274, surface. + + + +Subgenus 2. _Trigonastromma_, Haeckel. + +_Definition._--One odd arm different in form or size from the other two +arms, which are paired; distance between them different; fundamental form +of the shell therefore an isosceles triangle. + + +2. _Trigonastrum krohnii_, Haeckel. + + _Euchitonia krohnii_, Haeckel, 1862, Monogr. d. Radiol., p. 507. + +All three arms different; distance between the two paired arms smaller than +their distance from the odd arm. Odd arm with six joints. Each paired arm +with seven joints, increasing in breadth towards the distal end. Odd arm +and one paired arm forked at the end, the other paired arm simple. Patagium +nearly complete. (The asymmetry in this form may perhaps be an individual +anomaly, as also in _Myelastrum anomalum_, Pl. 47, fig. 9.) + +_Dimensions._--Radius of the arms about 0.13 to 0.16, breadth 0.05 to 0.08. + +_Habitat._--North Atlantic, Funchal, Madeira, Krohn, surface. + + +3. _Trigonastrum gegenbauri_, Haeckel. + + _Euchitonia gegenbauri_, Haeckel, 1862, Monogr. d. Radiol., p. 506, Taf. + xxxi. figs. 2, 3. + +Arms different; distance between the paired arms larger than their distance +from the odd arm, which is one-third shorter. Odd arm egg-shaped, simple, +with seven joints, undivided. Both paired arms equal, with ten joints, in +the distal third forked. Patagium nearly complete. + +_Dimensions._--Radius of the odd arm 0.14, greatest breadth 0.08; radius of +the paired arms 0.2. + +_Habitat._--Mediterranean (Messina), Haeckel, surface. + + + +{540}Genus 233. _Stauralastrum_,[272] n. gen. + +_Definition._--#Porodiscida# with four simple, undivided, chambered arms, +without a patagium; quadrangular shell a regular cross, with four equal +arms placed at right angles. + +The genus _Stauralastrum_ is the most simple form of the Tessarastrida, or +of those Porodiscida in which the margin of the central disk is armed with +four chambered arms. In _Stauralastrum_ these four arms are quite simple +and equal, without a patagium, separated by four right angles, so that the +whole shell represents a regular rectangular cross. If we connect the +distal points of the arms by lines, we get a complete square. (In my +Prodromus, 1881, the species of this genus were united with _Hagiastrum_, +which genus I now retain for the simple bilateral Tessarastrida.) + + + +Subgenus 1. _Stauralastrella_, Haeckel. + +_Definition._--Ends of the arms blunt, without terminal spines. + + +1. _Stauralastrum cruciforme_, n. sp. (Pl. 45, fig. 6). + +Arms very thin, nearly linear, four to five times as long as broad, of +equal breadth at the base and at the truncated distal end; their breadth +equals one-third of the radius of the central disk. Edges of the arms +parallel. + +_Dimensions._--Radius of each arm 0.8, breadth 0.016. + +_Habitat._--South Pacific, Station 293, surface. + + +2. _Stauralastrum lanceolatum_, n. sp. + +Arms lanceolate, three times as long as broad, in their middle part three +times as broad as at both ends; their greatest breadth nearly equals the +diameter of the central disk. (The arms have the same form as in +_Euchitonia lanceolata_, Pl. 43, fig. 9.) Edges of the arms convex. + +_Dimensions._--Radius of each arm 0.3, greatest breadth (in the middle +part) 0.08. + +_Habitat._--Pacific, central area, Station 273, depth 2350 fathoms. + + +3. _Stauralastrum ordo_, n. sp. + +Arms trapezoid, about as long as broad, twice as broad at their truncated +distal end as at the base; their basal breadth equals the radius of the +central disk, which exhibits two to three rings. (The arms have nearly the +same form as those in _Hagiastrum mosis_, Pl. 45, fig. 3.) Edges of the +arms rectilinear, divergent towards the ends. + +_Dimensions._--Radius of each arm 0.12, basal breadth 0.04, distal breadth +0.08. + +_Habitat._--Pacific, central area, Station 265, depth 2900 fathoms. + + +{541}4. _Stauralastrum clavigerum_, n. sp. + +Arms twice as long as broad, in their distal half lenticular, nearly +circular, twice as broad as in their square proximal half; their distal +breadth equals the diameter of the central disk, which exhibits three to +four rings. Edges of the arms concave. + +_Dimensions._--Radius of each arm 0.2, basal breadth 0.04, distal breadth +0.08. + +_Habitat._--Pacific, central area, Station 268, depth 2900 fathoms. + + +5. _Stauralastrum dilatatum_, n. sp. + +Arms of nearly equal length and breadth, at their convex distal end three +times as broad as at their narrow base; their distal breadth three times as +large as the radius of the central disk, which exhibits three to four +rings. (Resembles _Histiastrum quadrigatum_, Pl. 46, fig. 3, but has no +patagium.) Edges of the arms concave. + +_Dimensions._--Radius of each arm 0.15, basal breadth 0.04, terminal +breadth 0.12. + +_Habitat._--South Pacific, Station 300, depth 1375 fathoms. + + + +Subgenus 2. _Stauralastromma_, Haeckel. + +_Definition._--Ends of the arms with one or more terminal spines. + + +6. _Stauralastrum rhopalophorum_, n. sp. (Pl. 45, fig. 1). + + _Hagiastrum rhopalophorum_, Haeckel, 1881, Prodromus, p. 460. + +Arms cylindrical, eight times as long as broad at their base, at their +distal end club-shaped, three times as broad as at their base; their distal +breadth twice as large as the diameter of the central disk, which exhibits +two to three rings. Surface thorny, with larger spines towards the end, and +one radial, very strong, angular terminal spine. Edges of the arms +parallel. + +_Dimensions._--Radius of each arm (without terminal spine) 0.32, basal +breadth 0.03, terminal breadth 0.1. + +_Habitat._--Pacific, central area, Station 265, depth 2900 fathoms. + + +7. _Stauralastrum antiquum_, n. sp. + + _Rhopalastrum_ sp. Bury, 1862, Polycystins of Barbados, pl. xiv. fig. 5. + +Arms six times as long as broad at their base, in their distal half nearly +spherical, three times as broad as in their cylindrical basal half; their +distal breadth nearly equals the diameter of the central disk which +exhibits three to four rings. On the end of each arm one strong, angular, +terminal spine. (Differs from the preceding species by larger central disk +and stouter arms, also by less developed spines.) Edges of the arms +parallel. + +_Dimensions._--Radius of each arm 0.25, basal breadth 0.04, terminal +breadth 0.12. + +_Habitat._--Fossil in the Barbados rocks; and living in the depths of the +Central Pacific, Station 266, depth 2750 fathoms. + + +{542}8. _Stauralastrum staurolonche_, n. sp. + +Arms four times as long as broad at their base, gradually increasing +towards their truncated end, which is one and a half times as broad as +their base; their distal breadth equals the radius of the central disk, +which exhibits four to five rings. At the end of each arm is a very strong +conical terminal spine. (Resembles _Histiastrum quaternarium_, _Abhandl. k. +Akad. Wiss. Berlin_, 1875, Taf. xxiv. fig. 3, but has no patagium.) Edges +of the arms rectilinear, divergent. + +_Dimensions._--Radius of each arm 0.25, basal breadth 0.045, distal breadth +0.07. + +_Habitat._--Fossil in the Barbados rocks; and living in the depth of the +Equatorial Atlantic, Station 348, depth (2450) fathoms. + + +9. _Stauralastrum horridum_, n. sp. + +Arms three times as long as broad at their base, gradually increasing +towards their rounded end, which is twice as broad as their base, their +distal breadth equals the diameter of the central disk, which exhibits four +to five rings. Surface thorny, at the distal end of each arm is a group of +twenty to twenty-five smaller and five to six larger, straight, conical +spines. Edges of the arms rectilinear, divergent. + +_Dimensions._--Radius of each arm 0.15, basal breadth 0.05, distal breadth +0.1. + +_Habitat._--Pacific, central area, Station 270, depth 2925 fathoms. + + + +Genus 234. _Hagiastrum_,[273] Haeckel, 1881, Prodromus, p. 460. + +_Definition._--#Porodiscida# with four simple, undivided, chambered arms, +without a patagium; quadrangular shell bilateral, two opposite arms of the +main axis (or principal arms) different from the two others (or lateral +arms). + +The genus _Hagiastrum_, as here defined, was formerly united by me with the +foregoing _Stauralastrum_, but differs from it by the bilateral or +symmetrical form. Whilst in the latter all four arms and the four angles +between them are equal, they are here differentiated into pairs. + + + +Subgenus 1. _Hagiastrella_, Haeckel. + +_Definition._--Both longitudinal arms of equal size and form. + + +1. _Hagiastrum buddhae_, n. sp. (Pl. 45, fig. 5). + +Cross rectangular. Both longitudinal arms of equal size, twice as long as +the transverse arms; all arms smooth, club-shaped, twice as broad at their +globose distal part as at their base, each with three large conical +terminal spines. + +{543}_Dimensions._--Radius of the principal arms 0.4, of the lateral arms +0.2; basal breadth 0.06, distal breadth 0.12. + +_Habitat._--Indian Ocean, Belligemma, Ceylon, surface, Haeckel. + + +2. _Hagiastrum bramae_, n. sp. + +Cross rectangular. Both longitudinal arms of equal size, one and a half +times as long as the transverse arms; all arms thorny, club-shaped, at +their pear-shaped distal part three times as broad as at their base, +provided with numerous conical spines, one larger terminal spine at their +distal point. (Resembles _Stauralastrum rhopalophorum_, Pl. 45, fig. 1, but +is distinguished by the different size of the arm-pairs, and by the +stronger spines.) + +_Dimensions._--Radius of the principal arms 0.3, of the lateral arms 0.2; +basal breadth 0.04, distal breadth 0.12. + +_Habitat._--Indian Ocean, off Maldive Islands, surface, Haeckel. + + + +Subgenus 2. _Hagiastromma_, Haeckel. + +_Definition._--The two longitudinal arms different in size or form. + + +3. _Hagiastrum mosis_, n. sp. (Pl. 45, fig. 3). + +Cross rectangular. All four arms nearly isosceles, triangular, at their +narrow base half as broad as at their truncated, concavely fluted, distal +end. The posterior principal arm with twelve to thirteen joints, twice as +long as the anterior arm, which has six to seven joints and is one and a +half times as long as the two lateral arms (with four to five joints). + +_Dimensions._--Radius of the posterior arm 0.3, of the anterior 0.15, of +the lateral arms 0.1; basal breadth 0.05, terminal breadth 0.1. + +_Habitat._--Mediterranean (Smyrna), surface, Haeckel. + + +4. _Hagiastrum mohammedis_, n. sp. + +Cross with unequal angles, the anterior little smaller than the posterior. +All four arms club-shaped, thorny, three times as broad at their globose +distal end as at their narrow base, and furnished with ten to twelve +conical spines. Posterior principal arm twice as long as the anterior, and +four times as long as the rudimentary lateral arms. + +_Dimensions._--Radius of the posterior arm 0.4, of the anterior 0.2, of the +lateral arms 0.1; basal breadth 0.02 to 0.03, distal breadth 0.06 to 0.1. + +_Habitat._--Philippine Sea, Samboangan, Station 200, surface. + + +5. _Hagiastrum christi_, n. sp. + +Cross with unequal angles, the anterior somewhat smaller than the +posterior. All four arms of similar form, lanceolate, in their middle twice +as broad as at either obtuse end. The posterior {544}principal arm with +twelve joints, one and a half times as long as the anterior (with nine +joints) and twice as long as the two lateral arms (each with six joints). +The form and structure of the arms in this species are nearly the same as +in _Tessarastrum straussi_ (Pl. 45, fig. 8); but the arms are broader in +the middle, and are not connected by a patagium. + +_Dimensions._--Radius of the principal posterior arm 0.2, of the anterior +0.15, of each lateral arm 0.1; greatest breadth (in the width) 0.01, basal +breadth 0.03. + +_Habitat._--North Atlantic, Faeroee Channel, Gulf Stream, surface, John +Murray. + + + +Genus 235. _Histiastrum_,[274] Ehrenberg, 1847, Monatsber. d. k. preuss. +Akad. d. Wiss. Berlin, p. 54. + +_Definition._--#Porodiscida# with four simple, undivided, chambered arms, +connected by a patagium; square shell a regular cross, with four equal arms +and four right angles between them. + +The genus _Histiastrum_, quite insufficiently characterised by Ehrenberg +(1847), was afterwards (1875) illustrated by the figures of two different +fossil species. One of these, _Histiastrum ternarium_, with three arms, +belongs to _Hymeniastrum_; the other, _Histiastrum quaternarium_, is here +retained as the true, typical representative species of the genus. It +differs from its ancestral form _Stauralastrum_, by the possession of a +patagium, from _Tessarastrum_ by the regular square form of the shell. + + + +Subgenus 1. _Histiastrella_, Haeckel. + +_Definition._--Distal ends of the arms blunt, without terminal spines. + + +1. _Histiastrum quadrigatum_, n. sp. (Pl. 46, fig. 3). + +Arms at their distal end nearly as broad as long, and four times as broad +as at their narrow base; their lateral edges concave, their terminal edge +convex, without spines. Each arm is divided by seven to eight convex +transverse septa into eight to nine simple, broad chambers. Central disk +with three to four rings, about as broad as the fifth chamber. Patagium +complete, connecting all the lateral edges of the arms. + +_Dimensions._--Radius of each arm 0.15, basal breadth 0.03, terminal +breadth 0.12. + +_Habitat._--Equatorial Atlantic, Station 347, surface. + + +2. _Histiastrum excisum_, n. sp. + +Arms four times as long as broad at their base, and twice as broad at their +rounded blunt distal end as at their base; their lateral edges rectilinear, +divergent. Central disk with three to four rings, {545}somewhat broader +than their distal end. Patagium incomplete, connecting only the basal half +of the arms, with three to four concave chamber-rows, on the margin +concave. (May be regarded as _Euchitonia muelleri_, with four arms.) + +_Dimensions._--Radius of each arm 0.2, basal breadth 0.05, distal breadth +0.1. + +_Habitat._--Atlantic, surface, Canary Islands. + + +3. _Histiastrum velatum_, n. sp. (Pl. 46, fig. 4). + + _Dictyastrum velatum_, Haeckel, 1879, Atlas (pl. xlvi. fig. 4). + +Arms pear-shaped, rapidly increasing from their narrow base, nearly +circular, little longer than broad; each with eight to nine transverse +chamber-rows; their lateral edges at their base concave, at their end +circular. Central disk with three to four rings, somewhat smaller than one +arm. Patagium complete, with six to seven radial beams, filling out +perfectly the intervals between the arms. A peculiar girdle of finer +network and equal breadth surrounds the whole equatorial periphery of the +disk, and gives it the appearance of a square with rounded corners. + +_Dimensions._--Radius of each arm 0.2, basal breadth 0.03, distal breadth +0.12. + +_Habitat._--South Atlantic, Station 330, surface. + + + +Subgenus 2. _Histiastromma_, Haeckel. + +_Definition._--Distal ends of the arms spiny, furnished with one or more +terminal spines. + + +4. _Histiastrum quaternarium_, Ehrenberg. + + _Histiastrum quaternarium_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. + Wiss. Berlin, p. 74, Taf. xxiv. figs. 3, 4. + +Arms six times as long as broad at their base, with rectilinear, little +divergent edges; at their truncated distal end a little broader, with one +single, very strong, conical, terminal spine. Central disk with four to +five rings, somewhat broader than the arm. Patagium incomplete, enveloping +only the basal half of the arms. + +_Dimensions._--Radius of each arm 0.18, basal breadth 0.03, distal breadth +0.05. + +_Habitat._--Fossil in the rocks of Barbados. + + +5. _Histiastrum gladiatum_, n. sp. + + _Astromma_ sp., Bury, 1862, Polycystins of Barbados, pl. v. fig. 1. + +Arms triangular, eight times as long as broad at their base; at their +distal end three times as broad as at their base, with rectilinear, +divergent edges; their truncated end with a large conical, terminal spine. +Central disk with four to five rings, broader than the arms. Patagium +incomplete, enveloping only the basal half of the arms. + +{546}_Dimensions._--Radius of each arm 0.12, basal breadth 0.013, distal +breadth 0.04. + +_Habitat._--Fossil in the rocks of Barbados; and living in the depth of the +Central Pacific, Station 268, depth 2900 fathoms. + + +6. _Histiastrum boseanum_, n. sp. (Pl. 46, fig. 1). + +Arms linear, twelve times as long as broad at their base (at their distal +end twice as broad as at their base), with rectilinear, parallel edges. The +club-shaped end thickened, dentate, with two lateral rows of strong teeth +in the equatorial plane, and with one very stout, angular, terminal spine. +Central disk with two to three rings, broader than the arms. Patagium +incomplete, with four to five concave chamber-rows, enveloping only the +basal half of the arms. I call this splendid species in honour of Dr. Graf +Bose, the great friend of nature and patron of the University of Jena. + +_Dimensions._--Radius of each arm 0.25, basal breadth 0.02, distal breadth +0.05. + +_Habitat._--Indian Ocean, Madagascar, Rabbe. + + +7. _Histiastrum coronatum_, n. sp. + + _Stephanastrum_ sp., Bury, 1862, Polycystins of Barbados, pl. iv. fig. 1. + +Arms linear, eight times as long as broad, with rectilinear parallel edges; +the thickened, nearly spherical, distal end three times as broad, with five +strong conical spines, one middle (perradial) larger and two smaller on +each side of it. Central disk with two to three rings, of the same breadth +as the terminal knot of the arms. Patagium incomplete, square, enveloping +the arms, with the exception of the knot. + +_Dimensions._--Radius of each arm 0.16, basal breadth 0.02, terminal +breadth 0.06. + +_Habitat._--Fossil in the rocks of Barbados. + + +8. _Histiastrum circulare_, n. sp. + + _Stephanastrum_ sp., Bury, 1862, Polycystins of Barbados, pl. xxiii. fig. + 1. + +Arms linear in their inner half, egg-shaped and three times as broad in +their outer half, with ten to twelve strong terminal spines, the middle +(perradial) larger, in all three times as long as broad. Central disk with +three to four rings, broader than their distal knobs. Patagium nearly +complete, circular, enveloping the whole arms, with exception of the +outermost end. + +_Dimensions._--Radius of each arm 0.22, basal breadth 0.02, terminal +breadth 0.06. + +_Habitat._--Fossil in the rocks of Barbados; and living in the depths of +the Central Pacific, Station 268, depth 2900 fathoms. + + +9. _Histiastrum pentadiscus_, n. sp. (Pl. 46, fig. 2). + +Arms in their inner half linear, twice as long as broad, in their outer +half circular, three times as broad, with the same structure as the central +disk, exhibiting three concentric rings around one {547}central chamber. +Patagium complete, spongy, with radiating beams, enveloping the whole disk, +with the exception of the outermost end of the arms, which is armed with +twelve to sixteen strong conical spines, the middle (perradial) spine much +larger. + +_Dimensions._--Radius of each arm (without terminal spine) 0.18, basal +breadth 0.025, terminal breadth 0.08. + +_Habitat._--South Atlantic, Station 333, surface. + + + +Genus 236. _Tessarastrum_,[275] n. gen. + +_Definition._--#Porodiscida# with four simple, undivided, chambered arms, +connected by a patagium; quadrangular shell bilateral, two opposite arms of +the main axis (or principal arms) different from the two others (or lateral +arms). + +The genus _Tessarastrum_, formerly united by me with _Histiastrum_, differs +from the latter in its bilateral or symmetrical form, and bears therefore +the same relation to it that _Hagiastrum_ does to _Stauralastrum_. + + + +Subgenus 1. _Tessarastrella_, Haeckel. + +_Definition._--Both longitudinal arms of equal size and form. + + +1. _Tessarastrum straussii_, n. sp. (Pl. 45, fig. 8). + + _Histiastrum straussii_, Haeckel, 1881, Prodromus et Atlas (pl. xlv. fig. + 8). + +Cross not rectangular. Both principal arms of equal size and form, four +times as long as broad, and twice as long as the broader lateral arms; the +former with ten to eleven, the latter with five to six joints, separated by +convex transverse septa. Distal ends of the arms blunt. Axes of the smaller +arms not perpendicular to that of the larger arms; therefore the anterior +angles between them smaller than the posterior angles. Patagium between the +arms incomplete. I call this remarkable species after the great German +philosopher David Strauss. + +_Dimensions._--Radius of the principal arms 0.24, of the lateral arms 0.12; +greatest breadth (in the middle) of the former 0.05, of the latter 0.06. + +_Habitat._--North Pacific, _Hyalonema_-ground, March 5, 1875. + + +2. _Tessarastrum spinozae_, n. sp. + +Cross rectangular. Both principal arms of equal size and form, ten times as +long as broad, and twice as long as the lateral arms, which are only five +times as long as broad. All arms linear, at their distal end club-shaped, +and armed with twenty to thirty very strong angular spines. Patagium +incomplete, enveloping only the basal half of the arms. (Resembles +_Histiastrum boseanum_, {548}Pl. 46, fig. 1, but differs in the broader +arms and the unequal size of both pairs.) I call this species after the +great monistic philosopher Benedictus Spinoza. + +_Dimensions._--Radius of the principal arms 0.3, of the lateral arms 0.16; +basal breadth 0.025, distal breadth 0.05. + +_Habitat._--South Atlantic, Station 333, surface. + + +3. _Tessarastrum brunonis_, n. sp. (Pl. 45, fig. 9). + + _Histiastrum brunonis_, Haeckel, 1881, Prodromus et Atlas (pl. xlv. fig. + 9). + +Cross rectangular. Both principal arms of equal size and form, three times +as long as broad, each with ten joints, three times as long as the lateral +arms, which are nearly square, with four joints. All arms rounded, at their +truncated end little broader than at their base. No spines. Patagium +complete, envelops the whole shell, and is composed of two parallel +lattice-lamellae on each side of the flat disk, which are connected by very +fine perpendicular bars. This is shown clearly in fig. 9, Pl. 45, where the +disk is seen from the edge. I call this species after the great Italian +philosopher Giordano Bruno. + +_Dimensions._--Radius of the principal arms 0.22, of the lateral arms 0.12; +basal breadth 0.04, distal breadth 0.05. + +_Habitat._--South Pacific, Station 285, depth 2375 fathoms. + + + +Subgenus 2. _Tessarastromma_, Haeckel. + +_Definition._--The two principal arms of different size or form. + + +4. _Tessarastrum democriti_, n. sp. (Pl. 45, fig. 7). + + _Histiastrum democriti_, Haeckel, 1881, Prodromus et Atlas (pl. xlv. fig. + 7). + +Cross not rectangular; the two anterior angles smaller than the two +posterior. All four arms club-shaped, twice as broad at their rounded +obtuse distal end as at their base, of unequal length. Posterior principal +arm one and a fourth times as long as the posterior, and one and two-thirds +as long as the lateral arms. Patagium incomplete, enveloping only the basal +half of the arms. I call this species after the great Greek philosopher +Democritus. + +_Dimensions._--Radius of the posterior arm 0.3, of the anterior 0.25, of +each lateral arm 0.22; basal breadth 0.05, distal breadth 0.1. + +_Habitat._--Pacific, central area, Station 271, depth 2425 fathoms. + + + +Genus 237. _Stephanastrum_,[276] Ehrenberg, 1847, Monatsber. d. k. preuss. +Akad. d. Wiss. Berlin, p. 54. + +_Definition._--#Porodiscida# with four simple, undivided, chambered arms, +connected on the distal ends by a spongy, square or rhomboidal, patagial +girdle (or a patagium with four large, interbrachial openings). Shell +either regular or bilateral (with equal or unequal arms). + +{549}The genus _Stephanastrum_, founded (1847) by Ehrenberg for the very +peculiar _Stephanastrum rhombus_, differs from the nearly allied foregoing +genera in the imperfect development of the peculiar patagium, connecting +only the distal ends of the four arms, while it is absent at their base. +Two new species, different from _Stephanastrum rhombus_ by the regular +square form, were found in the Challenger collection. + + + +Subgenus 1. _Stephanastrella_, Haeckel. + +_Definition._--All four arms of the cross have the same size. + + +1. _Stephanastrum quadratum_, n. sp. (Pl. 46, fig. 5). + +All four arms of the same size, six times as long as broad at their base, +ending with a strong, short, four-sided pyramidal spine. In the outer half +of each arm are two opposite lateral spongy wings, which form an +equilateral triangle, and from union of the bases of the four triangles +arises the peculiar patagium, which forms a square with four large +interbrachial openings. + +_Dimensions._--Radius of each arm 0.25, basal breadth 0.035; length of the +sides of the square patagium 0.3. + +_Habitat._--Pacific, central area, Station 268, depth 2900 fathoms. + + +2. _Stephanastrum capitatum,_ n. sp. (Pl. 44, fig. 1). + +All four arms of the same size, five times as long as broad at their base, +at their distal end with a spongy, nearly spherical capitulum of twice +their breadth, provided with a very strong, angular, pyramidal, terminal +spine (half as long as the arm). All four arms connected by a square +patagium, arising immediately below the capitula, and perforated by four +large interbrachial openings. + +_Dimensions._--Radius of each arm (without the terminal spine) 0.25, basal +breadth 0.05; length of the sides of the square patagium 0.3. + +_Habitat._--Pacific, central area. Station 265, depth 2900 fathoms. + + + +Subgenus 2. _Stephanastromma_, Haeckel. + +_Definition._--Two opposite arms of the cross larger than the two others. + + +3. _Stephanastrum rhombus,_ Ehrenberg. + + _Stephanastrum rhombus_, Ehrenberg, 1854, Mikrogeol., Taf. xxxvi. fig. + 33; Abhandl. d. k. Akad. d. Wiss. Berlin, 1875, Taf. xxv. fig. 1. + +Two arms of the longitudinal axis one and a third times as long as two arms +of the transverse axis. All four arms linear, about eight times as long as +broad, at their distal end somewhat {550}thickened, club-shaped, with a +pyramidal terminal spine. The ends of the arms are connected by a +riband-shaped, straight, spongy patagium of the same breadth as the arms. +Between the rhomboidal patagium and the arms remain four large rectangular +triangles as interbrachial openings. + +_Dimensions._--Radius of the longer arms 0.2, of the shorter 0.15; basal +breadth 0.02; length of the sides of the rhombic patagium 0.25. + +_Habitat._--Fossil in the rocks of Barbados. + + + +Genus 238. _Dicranastrum_,[277] Haeckel, 1881, Prodromus, p. 460. + +_Definition._--#Porodiscida# with four forked, spongy, or chambered arms, +without a patagium; shell regular (not bilateral), with four equal arms +crossed at right angles. + +The genus _Dicranastrum_ comprises a number of very remarkable, hitherto +unknown, Euchitonida, which are rather common in the Pacific (mainly on the +surface), and characterised by the bifurcation of the cross-arms of the +regular square shell. It bears therefore to its probable ancestral form, +_Stauralastrum_, the same relation that in the triradiate Euchitonida +_Chitonastrum_ does to _Dictyastrum_. The arms are commonly of very +delicate structure, more or less spongy. + + + +Subgenus 1. _Dicranaster_, Haeckel. + +_Definition._--Each cross-arm with two simple branches. + + +1. _Dicranastrum furcatum_, n. sp. (Pl. 47, fig. 2). + +Arms simply forked, three times as long as broad at their base, with eight +blunt ends of the fork-branches. The simple proximal half of each arm about +the same size as each branch of the dichotomous distal part, twice as long +as broad. Edges of the arms ragged. + +_Dimensions._--Radius of each arm 0.38, basal breadth 0.12; breadth of the +forked part 0.3. + +_Habitat._--Pacific, central area, Station 271, surface. + + +2. _Dicranastrum dichotomum_, n. sp. + +Arms simply forked, four times as long as broad at their base; each arm +with two blunt branches. The simple proximal part of each arm is three +times as long and twice as broad as each branch of the dichotomous distal +part. Ends of the arms blunt, truncated. + +_Dimensions._--Radius of each arm 0.35, basal breadth 0.08; breadth of the +forked part 0.2. + +_Habitat._--South Pacific, Station 281, surface. + + +{551}3. _Dicranastrum cornutum_, n. sp. (Pl. 45, fig. 2). + + _Hagiastrum cornutum_, Haeckel, 1879, Atlas (pl. xlv. fig. 2). + +Four arms simply forked, four times as long as broad; each arm with two +triangular diverging branches ending in strong conical spines. The simple +basal part of each arm about of the same length as each branch of the +distal part, twice as long as broad. Distance between the terminal spines +of each arm nearly as great as its length. + +_Dimensions._--Radius of the arm 0.24, basal breadth 0.05; breadth across +the bifurcation 0.12. + +_Habitat._--South Atlantic, Station 325, surface. + + +4. _Dicranastrum antilope_, n. sp. + +Four arms simply forked, three times as long as broad; each arm with two +lanceolate diverging branches, ending in strong angular spines. The simple +basal part of each arm is twice as long as each branch of the distal part. +Distance of the two terminal spines of each arm scarcely half as great as +its length. + +_Dimensions._--Radius of the arm 0.32, basal breadth 0.11; breadth of the +branches 0.07. + +_Habitat._--Tropical Atlantic (off Ascension), Station 342, surface. + + + +Subgenus 2. _Tricranastrum_, Haeckel, 1881, Prodromus, p. 460. + +_Definition._--Each cross arm with three terminal branches, one middle +(perradial) and two lateral (adradial) branches. + + +5. _Dicranastrum wyvillei_, n. sp. (Pl. 47, fig. 3). + + _Tricranastrum wyvillei_, Haeckel, 1879, Natuerl. Schoepfungsgesch., p. + 705, Taf. xvi. fig. 5. + +Arms trifid, one and a half times as long as broad; each arm with three +blunt terminal branches of equal size. The simple basal part of each arm +twice as long as the trifid distal part. (The central capsule depicted in +fig. 3, Pl. 47, has the same form as the skeleton, and is only a little +smaller.) + +_Dimensions._--Radius of the arm 0.4, basal breadth 0.12, greatest breadth +(in the distal part) 0.24. + +_Habitat._--Pacific, central area, Station 271, surface. + + +6. _Dicranastrum tricuspis_, n. sp. + +Arms trifid, twice as long as broad; each arm with three pointed terminal +branches, ending in strong conical spines, the middle branch somewhat +larger than the other two. The simple basal part of each arm three times as +long as the trifid distal part. + +_Dimensions._--Radius of the arm 0.3, basal breadth 0.06, greatest breadth +(in their distal part) 0.15. + +_Habitat._--North Pacific, Station 244, surface. + + +{552}7. _Dicranastrum trifarium_, n. sp. + +Arms trifid, three times as long as broad at their base; each arm with +three pointed terminal branches, ending in strong sulcate spines; the +middle branch twice as large as the two others. The simple basal part of +each arm two and a half times as long as the trifid distal part. + +_Dimensions._--Radius of the arm 0.35, basal breadth 0.03, greatest breadth +(in the distal part) 0.05. + +_Habitat._--South Pacific, Station 298, surface. + + + +Subgenus 3. _Tetracranastrum_, Haeckel. + +_Definition._--Each cross-arm with four terminal branches, the two +fork-branches being again bifurcated. + + +8. _Dicranastrum bifurcatum_, n. sp. (Pl. 47, figs. 1, 1_a_). + +Arms doubly forked or quadripartite, six times as long as broad at their +base; each arm in its proximal half simple, three times as long as broad; +in its distal half doubly forked; the secondary branches with blunt, +roundish ends, nearly as large as the primary branches. Central disk (fig. +1_a_) with three concentric rings around the central chamber; from its +periphery radiate thin radial beams in the spongy framework of the delicate +arms. The central capsule has the same form as the skeleton, and is only a +little smaller. + +_Dimensions._--Radius of the arm 0.45, basal breadth 0.08; breadth of the +terminal branches 0.03. + +_Habitat._--North Pacific, east of Japan, Station 241, surface. + + + +Genus 239. _Myelastrum_,[278] Haeckel, 1881, Prodromus, p. 460. + +_Definition._--#Porodiscida# with four forked, spongy, or chambered arms, +without a patagium; shell bilateral, with paired different arms; two equal +anterior arms of different shape from the two equal posterior arms. + +The genus _Myelastrum_ differs from the foregoing _Dicranastrum_, the +ancestral form, by the twofold differentiation of the four arms. Whilst in +the latter all four arms are equal, separated by equal angles, here the two +anterior arms are constantly different from the two posterior. The lateral +angles between the two arm-pairs are equal, while the posterior and the +anterior angle (between the two arms of each pair) are more or less +different. The shell assumes, therefore, a very characteristic bilateral +form, similar to the "quadricorn cross" of the grey central substance in +the transverse section of the human medulla spinalis. Though the spongy +shell is commonly a most delicate and {553}thin disk it nevertheless +reaches unusual dimensions, its diameter in some species being more than a +millimetre. + + + +Subgenus 1. _Myelastrella_, Haeckel. + +_Definition._--Posterior arms simple, undivided; anterior arms lobated or +cleft, with one or more incisions at the distal end. + + +1. _Myelastrum medullare_, n. sp. (Pl. 47, fig. 13). + +Anterior arms bifid, nearly square, with a shallow incision at their broad +truncated end. Posterior arms somewhat smaller, nearly triangular, with +simple blunt ends. Sagittal constriction three-fourths as large as the +transverse one. Surface smooth. + +_Dimensions._--Radius of the anterior arms 0.36, of the posterior 0.3; +longitudinal constriction 0.24, transverse 0.36. + +_Habitat._--Pacific, central area, Station 271, surface. + + +2. _Myelastrum spinale_, n. sp. + +Anterior arms bifid, twice as long as broad, with a deep incision at their +truncated end. Posterior arms slender, half as large, with simple blunt +ends. Sagittal constriction one and a half times as large as the +transverse. Surface spiny. + +_Dimensions._--Radius of the anterior arms 0.4, of the posterior 0.2; +longitudinal constriction 0.3, transverse 0.2. + +_Habitat._--North Pacific, Station 248, surface. + + +3. _Myelastrum heteropterum_, n. sp. (Pl. 47, fig. 8). + +Anterior arms trifid, about as long as broad, with two incisions at their +broad truncated end. Posterior arms about half as large, simple, with +rounded blunt ends. Sagittal constriction two-thirds as large as the +transverse. Surface bristly. + +_Dimensions._--Radius of the anterior arms 0.65, of the posterior 0.035; +longitudinal constriction 0.4, transverse 0.6. + +_Habitat._--South Pacific, Station 291, surface. + + + +Subgenus 2. _Myelastromma_, Haeckel. + +_Definition._--All four arms (posterior as well as anterior) lobated or +cleft. + + +4. _Myelastrum octocorne_, n. sp. (Pl. 47, fig. 12). + +All four arms with a deep incision in their distal half; anterior arms +broader, but shorter than the posterior; in the anterior arms the two lobes +are of the same size, in the posterior arms the {554}median lobe is longer +than the lateral lobe. Sagittal constriction little smaller than the +transverse. Surface of the disk rough. + +_Dimensions._--Radius of the anterior arms 0.45, of the posterior 0.62; +longitudinal constriction 0.25, transverse 0.3. + +_Habitat._--Pacific, central area, Station 271, surface. + + +5. _Myelastrum farfalla_, n. sp. (Pl. 47, fig. 10). + +All four arms with a shallow incision at their distal end. Anterior arms +broader, but shorter than the posterior; in each arm the anterior lobe is +shorter than the posterior. Sagittal constriction smaller than the +transverse. Surface smooth. + +_Dimensions._--Radius of the anterior arms 0.4, of the posterior 0.6; +longitudinal constriction 0.5, transversal stricture 0.6. + +_Habitat._--Pacific, central area, Station 274, surface. + + +6. _Myelastrum papilio_, n. sp. (Pl. 47, fig. 6). + +All four arms with a shallow incision at their distal end. Anterior arms +triangular, of the same breadth, but of the double length of the square +posterior arms. Sagittal and transverse constrictions of the same length. +Surface ciliated. (Resembles a butterfly.) + +_Dimensions._--Radius of the anterior arms 0.7, of the posterior 0.4; +longitudinal and transverse constrictions 0.4. + +_Habitat._--North Pacific, near Japan, Station 241, surface. + + +7. _Myelastrum decaceros_, n. sp. (Pl. 47, fig. 7). + +Anterior arms bifid, with one shallow incision at their distal end. +Posterior arms of the same length, but much broader, trifid, with two +incisions (one larger and one smaller). Sagittal and transverse +constrictions of the same length. Surface spiny. + +_Dimensions._--Radius of all four arms 0.4; longitudinal and transverse +constrictions 0.35. + +_Habitat._--Pacific, central area, Station 272, surface. + + +8. _Myelastrum dodecaceros_, n. sp. (Pl. 47, figs. 11, 11_a_). + +Anterior arms trifid, with two shallow incisions at their distal end. +Posterior arms about one-third larger, also trifid, with one deeper +anterior and one shallower posterior incision. Sagittal constriction much +longer than the transverse. Surface ciliated, covered with numerous thin +and long radial bristles (fig. 11_a_). + +_Dimensions._--Radius of the anterior arms 0.5, of the posterior 0.7; +longitudinal constriction 0.5, transverse 0.35. + +_Habitat._--Pacific, central area, Station 270, surface. + + +{555}9. _Myelastrum ciliatum_, n. sp. + +Anterior arms trifid, with two shallow incisions. Posterior arms somewhat +smaller, also trifid, with two deeper incisions. Sagittal constriction a +little larger than the transverse. Margin of the disk ciliated, with radial +bristle-shaped spines, as prolongations of the inner radial beams, arising +from the central disk. + +_Dimensions._--Radius of the anterior arms 0.6, of the posterior 0.5; +longitudinal constriction 0.4, transverse 0.35. + +_Habitat._--South Pacific, Station 288, surface. + + +10. _Myelastrum lobatum_, n. sp. + +Anterior arms somewhat broader but shorter than the posterior arms. Each +arm four-lobed, with three terminal shallow incisions of nearly equal size. +Sagittal constriction smaller than the transverse. Surface of the disk +bristly. + +_Dimensions._--Radius of the anterior arms 0.4, of the posterior 0.5; +longitudinal constriction 0.3, transverse 0.35. + +_Habitat._--North Pacific, Station 253, surface. + + +11. _Myelastrum rotula_, n. sp. + +Anterior arms little broader than the posterior, but of the same length. +Each arm four-lobed, with three terminal deep incisions of equal size. +Sagittal and transverse constrictions equal. The whole disk nearly +circular, resembles a wheel with sixteen spokes. Surface smooth. + +_Dimensions._--Radius of all four arms 0.5; longitudinal and transverse +constrictions 0.3. + +_Habitat._--Pacific, central area, Station 274, surface. + + +12. _Myelastrum giganteum_, n. sp. + +Anterior arms somewhat broader and shorter than the posterior. Each arm +four-lobed, with three shallow terminal incisions, the middle incision +twice as deep as the two laterals. Sagittal constriction a little larger +than the transverse. Margin ciliated, with radial bristle-shaped spines as +prolongations of the inner radial beams, proceeding from the central disk +(as in _Myelastrum dodecaceros_, Pl. 47, figs. 11, 11_a_). + +_Dimensions._--Radius of the anterior arms 0.6, of the posterior 0.8; +longitudinal constriction 0.6, transverse 0.5. + +_Habitat._--Pacific, central area, Station 271, surface. + + +{556}13. _Myelastrum anomalum_, n. sp. (Pl. 47, fig. 9). + +All four arms of different size and form; anterior arms broader, posterior +longer; one anterior arm trifid, the three other arms bifid; length of the +branches unequal; all four angles between the arms unequal. (This anomalous +form, seen only once, may be an individual abnormality.) + +_Dimensions._--Radius of the arms 0.4 to 0.7; constrictions 0.3. + +_Habitat._--North Pacific, Station 237, surface. + + + +Genus 240. _Pentalastrum_,[279] Haeckel, 1881, Prodromus, p. 461. + +_Definition._--#Porodiscida# with five simple, undivided, chambered arms, +without a patagium. + +The genus _Pentalastrum_ opens the small series of Euchitonida, in which +the shell is not provided with three or four arms, as usual, but with five. +All forms of this little group are rare. Some species resemble in their +external form and in the articulation of their arms certain forms of +Asterida. In _Pentalastrum_, the most simple genus, the five arms are +simple, not forked, and without a patagium. It can be derived from +_Dictyastrum_ or _Stauralastrum_ by increase of the number of arms. + + + +Subgenus 1. _Pentalastrella_, Haeckel. + +_Definition._--All five arms equal, with equal angles between them. Shell a +regular pentagon. + + +1. _Pentalastrum asteracanthion_, n. sp. + +All five arms equal, club-shaped, at their thickened obtuse end three times +as broad as at their base, twice as long as broad. Angles between the arms +equal. + +_Dimensions._--Radius of each arm 0.2, basal breadth 0.03, distal breadth +0.08. + +_Habitat._--Pacific, central area, Station 272, depth 2600 fathoms. + + +2. _Pentalastrum astropecten_, n. sp. + +All five arms equal, with five to six distinct, simple joints, the basal +joint two-thirds as broad as the terminal joint, which bears a strong +conical spine. Angles between the arms equal. (Resembles _Pentinastrum +asteriscus_, Pl. 44, fig. 2, but has no patagium.) + +_Dimensions._--Radius of each arm 0.14, basal breadth 0.024, distal breadth +0.036. + +_Habitat._--Pacific, central area, Station 263, depth 2650 fathoms. + + + +{557}Subgenus 2. _Pentalastromma_, Haeckel. + +_Definition._--Arms of different sizes, one odd arm larger than the two +others; the opposite odd angle generally different from the four other +angles. + + +3. _Pentalastrum ophidiaster_, n. sp. (Pl. 44, fig. 3). + +Arms nearly triangular, at their obtuse truncated distal end twice as broad +as at their base. Four arms equal, with five joints each; the fifth arm +twice as long, with seven joints. Angles between the arms nearly equal; the +odd angle a little larger. + +_Dimensions._--Radius of the larger odd arm 0.25, of the four smaller arms +0.15; basal breadth 0.035, distal breadth 0.07. + +_Habitat._--Pacific, central area, Station 274, surface. + + +4. _Pentalastrum cometa_, n. sp. + +Arms nearly cylindrical, at their obtuse truncated distal end one and a +half times as broad as at their base. Posterior odd arm very large, with +eleven joints, about three times as long as the two lateral arms (with five +joints each) and four times as long as the two anterior arms (with three +joints each). Angles between the paired arms different; the two lateral +angles smaller than the two posterior, and these smaller than the odd +anterior angle. + +_Dimensions._--Radius of the odd posterior arm 0.5, of the lateral arms +0.25, of the anterior arms 0.18; basal breadth 0.05, distal breadth 0.08. + +_Habitat._--South Pacific, Station 288, surface. + + + +Genus 241. _Pentinastrum_,[280] Haeckel, 1881, Prodromus, p. 461. + +_Definition._--#Porodiscida# with five simple, undivided, chambered arms, +connected by a patagium. + +The genus _Pentinastrum_ differs from the foregoing _Pentalastrum_ only in +the development of a patagium or connecticulum between the arms, and bears +therefore the same relation to it that _Histiastrum_ does to +_Stauralastrum_, or _Hymeniastrum_ to _Dictyastrum_. + + +1. _Pentinastrum asteriscus_ , n. sp. (Pl. 44, fig. 2). + +All arms equal, twice as long as broad, at their base two-thirds as broad +as at their truncated distal end, which bears a strong, pyramidal, terminal +spine. Each arm is divided by five transverse septa into six joints or +chambers, and each of these by a radial beam into a pair of chambers. The +five radial beams arise from the innermost chamber of the central disk, and +end in the five terminal {558}spines. The diameter of the central disk is +larger than the length of the arms. The angles between the arms are equal +and filled up by an incomplete patagium, so that the whole disk forms a +regular pentagon with five concave sides. + +_Dimensions._--Radius of each arm (without terminal spine) 0.14; breadth at +their base 0.02, at their terminal joint 0.03; radius of the central disk +0.06. + +_Habitat._--Pacific, central area, Station 266, depth 2750 fathoms. + + +2. _Pentinastrum goniaster_, n. sp. + + ? _Stephanastrum_ sp., Bury, 1862, Polycystins of Barbados, pl. xx. fig. + 1. + +All five arms equal, four times as long as broad, club-shaped, at their +globose distal end twice as broad as at their base, and armed with a strong +conical terminal spine. Diameter of the central disk equals only one-third +of the length of the arms. The articulation of the spongy arms is somewhat +obscure. Patagium complete, totally fills up the interbrachial spaces, so +that the whole disk forms a regular pentagon with five rectilinear sides, +except that the terminal spines project at the corners. + +_Dimensions._--Radius of each arm 0.18, basal breadth 0.02, distal breadth +0.04; radius of the central disk 0.05. + +_Habitat._--South Pacific, Station 295, depth 1500 fathoms; also fossil in +the rocks of Barbados. + + + +Genus 242. _Pentophiastrum_,[281] n. gen. + +_Definition._--#Porodiscida# with five forked chambered arms, without a +patagium. + +The genus _Pentophiastrum_ differs from the two preceding genera by the +bifurcation of the five arms, and can be derived either from _Pentalastrum_ +by the ramification of the distal ends of the arms, or from the similar +_Myelastrum_ by the increase in the number of arms. + + +1. _Pentophiastrum dicranastrum_, n. sp. + +All five arms equal, with equal angles between them. Each arm in the basal +half simple, in the distal half forked; both branches of it equal, with +obtuse ends. (This regular species resembles _Dicranastrum furcatum_, Pl. +47, fig. 2, but with five rays instead of four; also the form of the arms +is more slender and the edges smooth.) + +_Dimensions._--Radius of each arm 0.25, breadth 0.05. + +_Habitat._--Equatorial Atlantic, Station 347, depth 2250 fathoms. + + + +Subgenus _Pentophiastromma_, Haeckel. + +_Definition._--Arms of different size, one odd arm opposite to the angle +between both arm-pairs. + + +{559}2. _Pentophiastrum caudatum_, n. sp. (Pl. 47, fig. 5). + +Arms in pairs different; four arms in the basal half simple, in the distal +half forked; the fifth (posterior) odd arm simple, undivided, cylindrical; +the anterior pair a little smaller than the posterior; the neighboring +branches of the two pairs on each side larger than the two others. Axes of +the arms and their branches straight. + +_Dimensions._--Radius of the arms about 0.5, breadth 0.12. + +_Habitat._--North Atlantic, Station 353, depth 2965 fathoms. + + +3. _Pentophiastrum forcipatum_, n. sp. (Pl. 47, fig. 4). + +Arms in pairs different, all in the basal two thirds simple, in the distal +third forked. Only in the posterior (odd) arm both branches are equal, in +the four others unequal. The common axis of the posterior lateral pair is +horizontal, perpendicular to the median line; the axes of the anterior pair +are pincer-like, concavely curved towards the median line or principal +axis. + +_Dimensions._--Radius of the arms about 0.5, breadth 0.14. + +_Habitat._--South Atlantic, Station 332, depth 2200 fathoms. + + + +Genus 243. _Hexalastrum_,[282] Haeckel, 1881, Prodromus, p. 461. + +_Definition._--#Porodiscida# with six simple chambered arms, without a +patagium. + +The genus _Hexalastrum_, together with the following _Hexinastrum_, +encloses those _Euchitonida_ in which the number of the chambered arms +surrounding the central disk amounts to six. This is the highest number of +these articulated marginal appendages which is reached in any #Discoidea#. +Formerly (1881) in my Prodromus, p. 459, I supposed that the same number +was reached also by one Coccodiscid, and called this genus _Hexactura_. +Afterwards I was convinced that this form was also a _Hexalastrum_. + + +1. _Hexalastrum palmanthum_, n. sp. + +All six arms equal, with equal angles between them. Each arm club-shaped, +three times as long as broad, twice as broad at the thickened distal end as +at the base, without a terminal spine. + +_Dimensions._--Radius of each arm 0.2, basal breadth 0.02, distal breadth +0.06. + +_Habitat._--Pacific, central area, Station 274, depth 2750 fathoms. + + +2. _Hexalastrum crinanthum_, n. sp. + +All six arms equal, with equal angles between them. Each arm club-shaped, +four times as long as broad, at the egg-shaped distal end three times as +broad as in the linear basal part, provided {560}with numerous short +conical spines and one longer terminal spine. (Resembles _Stauralastrum +rhopalophorum_, Pl. 45, fig. 1, but with six rays instead of four.) + +_Dimensions._--Radius of each arm 0.3, basal breadth 0.03, distal breadth +0.08. + +_Habitat._--Pacific, central area, Station 268, depth 2900 fathoms. + + + +Subgenus _Hexalastromma_, Haeckel. + +_Definition._--Arms more or less different in size or form; shell +bilateral. + + +3. _Hexalastrum orchidaceum_, n. sp. (Pl. 44, fig. 5). + + _Hexactura orchidacea_, Haeckel, 1881, Prodromus, p. 459. + +Arms different in length, so that two unequal opposite odd arms determine +the main axis, and the four other arms lie on both sides of this as two +different pairs. The proportion of their relative length is the +following:--anterior lateral arms five, anterior odd arm six; posterior +lateral arms seven, posterior odd arm eight. Each arm is club-shaped, two +to three times as long as broad, and divided into six to eight joints by +five to seven transverse septa; its distal end is armed with a terminal +spine and twice as broad as its base. + +_Dimensions._--Radius of the posterior odd arm 0.4, of the anterior odd arm +0.3; of the posterior lateral pair 0.35, of the anterior lateral pair 0.25; +basal breadth 0.08, distal breadth 0.16. + +_Habitat._--Pacific, central area, Station 266, depth 2750 fathoms. + + + +Genus 244. _Hexinastrum_,[283] Haeckel, 1881, Prodromus, p. 461. + +_Definition._--#Porodiscida# with six simple, undivided, chambered arms, +connected by a patagium. + +The genus _Hexinastrum_ differs from its ancestral form _Hexalastrum_ by +the development of a patagium between the arms. The only observed species +is regular. + + +1. _Hexinastrum geryonidum_, n. sp. (Pl. 44, fig. 4). + + _Hexalastrum geryonidum_, Haeckel, 1879, Atlas (pl. xliv. fig. 4). + +Disk quite regular with six radii; all six arms of the same size and form, +at their broad, convexly rounded, smooth end five times as broad as at +their narrow base, and little longer than broad. Each arm is divided by +eight transverse septa into nine simple joints or chambers of the same +height; the breadth of the distal chambers increases rapidly. The regular, +hexagonal, central disk exhibits four concentric rings around the central +chamber. Patagium between the arms incomplete, with concavely fluted edge. + +_Dimensions._--Radius of each arm 0.15, basal breadth 0.016, distal breadth +0.08; radius of the central disk 0.04. + +_Habitat._--Pacific, central area, Station 272, depth 2600 fathoms. + + + +{561}Family XXII. #PYLODISCIDA#, n. fam. (Pl. 48, figs. 12-20). + +_Definition._--#Discoidea# without phacoid shell, with flat discoidal +shell, in which a simple spherical central chamber is surrounded by one or +two concentric triradial girdles; each girdle with three gates, separated +by three simple arm-chambers. Surface of the disk with three open or +latticed gates on each flat side. + +The family #Pylodiscida# represents a new small but interesting group of +#Discoidea#, which exhibits rather complex affinities to different groups +of #Sphaerellaria#. In my Prodromus (1881, p. 464) I had enumerated only +two genera of this family, _Triopyle_ and _Hexapyle_, and had united them +with _Tetrapyle_ and allied genera in the family Pylonida. Indeed, the +resemblance of skeletal structure in the two groups is very great. The most +simple forms of both groups exhibit a simple spherical latticed central +chamber, which is surrounded by few latticed chambers of similar size and +form, separated by open gates. But in the Pylonida these chambers are +opposite in pairs, and form together a complete lattice-girdle around the +central chamber, whereas in the Pylodiscida the chambers are not opposite +in pairs in one axis, and form therefore only latticed half girdles, which +arise from the central chamber like radial arms, and may perhaps better be +called "arm-chambers"; their number is constantly three. The free open +spaces between these three arm-chambers form three gates, comparable to the +two or four gates of _Amphipyle_, _Tetrapyle_, &c., and become afterwards +closed by lattice-work in a similar way in both groups. A more important +difference between them is indicated by the further mode of growth. The +Pylonida build new girdles in all three dimensive planes (alternating in +the transverse, lateral and sagittal planes); their geometric fundamental +form is therefore the "lentellipsis" or the "triaxial ellipsoid." The +Pylodiscida, however, grow only at the periphery of the discoidal shell in +one single plane (the equatorial plane); their fundamental form is +therefore the biconvex lens or the flat disk (a shortened cylinder). This +important difference is my deciding motive, in separating the latter from +the former and in regarding the Pylodiscida as true #Discoidea#, the more +so as they can easily be derived from _Archidiscus_, the fundamental and +ancestral form of the Porodiscida. + +One single form of _Archidiscus_ seems to be of peculiar importance in this +relation, viz., _Archidiscus hexoniscus_ (Pl. 48, fig. 10). In this species +the simple central chamber is surrounded by a latticed ring or girdle, +composed of six equal chambers of the same size and form, all lying in the +same plane with the central chamber. In a nearly allied species, viz., +_Archidiscus pyloniscus_, the six ring-chambers are different, three +smaller (with denser network) alternating with three larger (of looser +network); if we imagine the network of the latter reduced to a marginal bar +we get _Triopyle_, and if also this bar disappear by reduction we get +_Triolena_, the most simple form of the Pylodiscida. {562}Even _Archidiscus +pyloniscus_ may possibly represent the same form among the Porodiscida as +_Triodiscus lenticula_ among the Pylodiscida; this important form indicates +clearly the close affinity of the two families. + +If we take the latter, nearly identical form as the common starting point +of both families of Cyclodiscaria, then probably _Triopyle_ and _Triolene_ +must be regarded as retrograde forms, derived from _Triodiscus_ in the one +case, from _Archidiscus_ in the other, by reduction of three interradial +arm-chambers, whilst three perradial only remain. But it is also possible +that the most simple form, _Triolene_, originated independently from some +_Cenosphaera_, three simple radial chambers, like the latticed central +chamber, being derived from the latter by apposition in three equidistant +radii, whilst three other radii between them remained free. In this case +the other genera of Pylodiscida are derived from their ancestral form +_Triolene_. + +Adopting this latter view, we find that all eight genera of Pylodiscida, +here distinguished, may be regarded as following members of a continuous +series. If the three simple arm-chambers of _Triolene_, surrounding the +equal central chamber, become united at their distal ends by a concentric +equatorial ring, then originates _Triopyle_; and this graduates into +_Triodiscus_ by fenestration of the three open gates between the three +latticed arms. Whilst these three genera form together the subfamily +Triopylida, a second family, Hexapylida, is composed of three other +analogous genera, in which the same process of development becomes +repeated. + +_Pylolena_, the most simple form of Hexapylida, arises from _Triodiscus_ by +the development of three new arm-chambers (of the second order) which are +apposed at the distal end of the three primary arm-chambers (of the first +order) in the same radius. If the distal ends of these three secondary +arm-chambers become united by a concentric latticed ring or girdle, we get +_Hexapyle_ (with six open gates, two in each radius), and if its six gates +become afterwards closed by loose lattice-work, we arrive at _Pylodiscus_ +(a repetition of _Triodiscus_). + +A third subfamily, Discopylida, is formed by the building of a chambered +equatorial girdle around the margin of _Pylodiscus_. This girdle has quite +the same structure as the similar chambered rings or girdles of the +Porodiscida and Coccodiscida. Between the two sieve-plates of the disk +surface is enclosed a variable number (twelve to twenty-four or more) of +chambers, imperfectly separated by radial beams, which connect the margin +of the _Pylodiscus_-shell with an outer peripheral concentric ring. In +_Discozonium_ this marginal ring is perfect, whilst in _Discopyle_ it is +interrupted by a peculiar large opening, a "marginal osculum" surrounded by +a corona of spines, quite the same remarkable formation which we +encountered in _Ommatodiscus_ among the Porodiscida. + +All Pylodiscida are therefore triradial (with three perradial arms and +three interradial gates between them), and many of them have a great +resemblance to certain triradial Porodiscida and Spongodiscida, perhaps not +only a morphological resemblance, but also {563}a true phylogenetic +relation. But it is remarkable that we do not find further forms of +development in this family, by multiplication either of the arm-chambers +(further growth in the three perradii) or of the concentric chambered rings +(in the periphery of the disk margin). + +The central capsule of the Pylodiscida is constantly flat, discoidal, and +enclosed between the two sieve-plates of the surface. Its form is either +circular or triangular. + +_Synopsis of the Genera of the Pylodiscida._ + + ------------------------------------------------------------------------- + I. Subfamily Triopylida. + Three gates between three simple arm-chambers. + ----------------------------------------------------------------------- + Three gates open, without a barring equatorial + girdle, 245. _Triolena_. + + Three gates barred by a { Gate-faces simple, 246. _Triopyle_. + latticed equatorial { + girdle. { Gate-faces latticed, 247. _Triodiscus_. + ------------------------------------------------------------------------- + II. Subfamily Hexapylida. + Six gates between three double arm-chambers (three inner and three + outer); no chambered marginal girdle. + ------------------------------------------------------------------------- + Three outer gates open, without a barring equatorial + girdle, 248. _Pylolena_. + + { Both faces of the outer + Three outer gates barred { gates simple, 249. _Hexapyle_. + by a latticed (second) { + equatorial girdle. { Both faces of the outer + { gates latticed, 250. _Pylodiscus_. + ------------------------------------------------------------------------- + III. Subfamily Discopylida. + Six gates between three double arm-chambers. + ------------------------------------------------------------------------ + { No peculiar osculum on + In the equatorial plane { the margin of the disc, 251. _Discozonium_. + on the margin of the { + Pylodiscus-shell is a { One pecuiar osculum (with + chambered equatorial { a corona of spines) on + girdle. { the margin of the disc, 252. _Discopyle_. + + + +Subfamily 1. TRIOPYLIDA, Haeckel. + +_Definition._--#Pylodiscida# with a simple, spherical or lenticular, +central chamber, surrounded by three simple arm-chambers, which are +separated by three notches or gates. + + + +Genus 245. _Triolena_,[284] n. gen. + +_Definition._--#Pylodiscida# with a simple, spherical or lenticular, +central chamber, surrounded by three simple arm-chambers. Notches between +the three arms open. + +The genus _Triolena_ is the most simple form of all Pylodiscida, and must +be regarded as their common ancestral form, from an ontogenetic as well as +a phylogenetic point of view. The small shell is composed of a simple, +spherical or lenticular, latticed, central chamber, and of three simple, +surrounding equal arms, which are also simple latticed chambers, lie in the +equatorial plane, and are separated by three equal angles or open gates. + + +{564}1. _Triolena primordialis_, n. sp. (Pl. 48, fig. 12). + +Arm-chambers trapezoid, nearly square, of the same size as the circular, +lenticular, primordial, central chamber. Surface of the disk smooth. + +_Dimensions._--Diameter of the shell 0.045, of the central chamber 0.015, +of each arm 0.015. + +_Habitat._--Central Pacific, Station 272, depth 2600 fathoms. + + +2. _Triolena tribelone_, n. sp. + +Arm-chambers lanceolate, of the same breadth as and twice the length of the +triangular, central chamber; at the pointed end of each arm is a conical +terminal spine (in the equatorial plane). Surface of the disk thorny. + +_Dimensions._--Diameter of the shell 0.05, of the central chamber 0.015; +length of the arms 0.02, breadth 0.016. + +_Habitat._--North Pacific, Station 244, depth 2900 fathoms. + + +3. _Triolena trispinosa_, n. sp. + +Arm-chambers ovate, in the basal half nearly as broad as the hexagonal +central chamber, at the pointed distal end with a strong conical radial +spine of double the length. Surface rough. + +_Dimensions._--Diameter of the shell 0.055, of the central chamber 0.02. + +_Habitat._--Western Tropical Pacific, Station 225, depth 4475 fathoms. + + +4. _Triolena hexabelone_, n. sp. + +Arm-chambers nearly triangular, at the base half as broad as the hexagonal +central chamber, at the truncate distal end one and a half times as broad, +and armed with two radial conical spines (in the equatorial plane). Surface +of the disk smooth. + +_Dimensions._--Diameter of the shell 0.06, of the central chamber 0.02. + +_Habitat._--South Pacific, Station 295, depth 1500 fathoms. + + +5. _Triolena trigonalis_, n. sp. + +Arm-chambers nearly triangular, at the base half as broad as the circular +central chamber, at the concave lunulate distal end twice as broad, and +armed with four conical radial spines (two on each side of the equatorial +plane). Surface thorny. + +_Dimensions._--Diameter of the shell 0.05, of the central chamber 0.015. + +_Habitat._--Central Pacific, Station 271, depth 2425 fathoms. + + + +{565}Genus 246. _Triopyle_,[285] Haeckel, 1881, Prodromus, p. 464. + +_Definition._--#Pylodiscida# with a simple, spherical or lenticular, +central chamber, surrounded by three simple arm-chambers. Notches between +the three arms transformed into gates by a connecting equatorial girdle. + +The genus _Triopyle_ differs from the preceding _Triolene_ in the +development of a simple ring or latticed equatorial girdle, which connects +the distal ends of the three arm-chambers, and transforms the open notches +between them into three gates. The ring may be circular, triangular, or +hexagonal. + + +1. _Triopyle circulus_, n. sp. + +Disk circular, three times as broad as the hexagonal central chamber. Three +arm-chambers trapezoidal, at the convex distal end as broad, at the base +half as broad as the three circular gates between them. Surface smooth. No +marginal spines on the girdle. + +_Dimensions._--Diameter of the disk 0.045, of the gates 0.015. + +_Habitat._--Central Pacific, Station 271, depth 2425 fathoms. + + +2. _Triopyle hexagona_, n. sp. (Pl. 48, fig. 13). + +Disk hexagonal, three times as broad as the circular central chamber. Three +arm-chambers trapezoidal, at the truncated distal end as broad, at the base +half as broad as the three triangular gates between them. Surface smooth. +No marginal spines. + +_Dimensions._--Diameter of the disk 0.05, of the gates 0.02. + +_Habitat._--North Pacific, Station 244, depth 2900 fathoms. + + +3. _Triopyle trigona_, n. sp. + +Disk triangular, four times as broad as the circular central chamber. Three +arm-chambers nearly triangular, at the narrow base half as broad, at the +distal end twice as broad as the circular or roundish gates. Surface +smooth. On the margin (in the equatorial plane) three strong pyramidal +spines (at the end of the arms). + +_Dimensions._--Diameter of the disk 0.04, of the gates 0.015. + +_Habitat._--Central Pacific, Station 274, depth 2750 fathoms. + + +4. _Triopyle cordigera_, n. sp. + +Disk hexagonal, four times as broad as the hexagonal central chamber. Three +arm-chambers triangular, at the base half as broad as at the truncated +distal end, about the same size as the {566}three heart-shaped gates. On +the six corners of the margin (which forms a regular hexagon) are six +pyramidal radial spines, as prolongations of the arm-edges. + +_Dimensions._--Diameter of the disk 0.05, of the gates 0.02. + +_Habitat._--Indian Ocean, Ceylon, surface, Haeckel. + + +5. _Triopyle renigera_, n. sp. + +Disk hexagonal, five times as broad as the circular central chamber. Three +arm-chambers trapezoidal, at the base one-third, at the distal end +two-thirds as broad as the three kidney-shaped gates. On the six corners of +the margin (which forms an irregular hexagon) six conical radial spines, as +prolongations of the arm-edges. + +_Dimensions._--Diameter of the disk 0.06, of the gates 0.02. + +_Habitat._--South Pacific, Station 295, depth 1500 fathoms. + + +6. _Triopyle spinigera_, n. sp. + +Disk roundish, triangular, four times as broad as the triangular central +chamber, which is armed with three radial spines between the arms. +Arm-chambers club-shaped, at the narrow base one-fourth, at the distal end +half as broad as the square gates. On the margin twelve large conical +spines, two opposite on each face of the distal end of each arm-edge. Three +smaller radial spines on the three corners of the girdle (in the same +interradial meridian planes as the three spines of the central chamber). +Compare _Triodiscus spinosus_. + +_Dimensions._--Diameter of the disk 0.05, of the gates 0.02. + +_Habitat._--South Atlantic, Station 332, depth 2200 fathoms. + + + +Genus 247. _Triodiscus_,[286] n. sp. + +_Definition._--#Pylodiscida# with a simple, spherical or lenticular, +central chamber, surrounded by three simple arm-chambers. Notches between +the three arms closed by lattice-work and by an equatorial girdle. + +The genus _Triodiscus_ differs from the preceding _Triopyle_ in the +development of loose lattice-work on both sides of the discoidal shell. +This network closes the gates and transforms the whole shell into a +fenestrated lens. The singular species of _Triodiscus_ correspond to +certain species of _Triopyle_. + + +1. _Triodiscus lenticula_, n. sp. + +Disk circular, lenticular, three times as broad as the central chamber. +Three arm-chambers trapezoidal, of the same size and form as the three +gates between them, which are closed by a loose {567}delicate network +(differs from _Triopyle circulus_ by the production of the two convex +latticed plates, which envelop the whole lens). Margin smooth. + +_Dimensions._--Diameter of the disk 0.045, of the gates 0.015. + +_Habitat._--Central Pacific, Station 268, depth 2900 fathoms. + + +2. _Triodiscus trigonus_, n. sp. + +Disk triangular, four times as broad as the central chamber. Three +arm-chambers at the base half as broad, at the distal end twice as broad as +the roundish gates. Surface smooth. On the three corners of the margin (in +the arm-radius) three strong spines. (Differs from _Triopyle trigona_ only +in the loose framework closing the gates.) + +_Dimensions._--Diameter of the disk 0.04, of the gates 0.015. + +_Habitat._--Central Pacific, Station 272, depth 2600 fathoms. + + +3. _Triodiscus spinosus_, n. sp. (Pl. 48, fig. 14). + +Disk subcircular, four times as broad as the triangular central chamber. +Three arm-chambers club-shaped, at the base one-third, at the distal end +two-thirds as broad as the semicircular gates. Surface thorny. On the +margin fifteen larger radial spines, three on the corners of the disk (in +the radius of the gates), twelve on the two faces of the arms ends (two +opposite on the edge of each end.) (Differs from _Triopyle spinigera_ +mainly by the delicate hexagonal network closing the gates.) + +_Dimensions._--Diameter of the disk 0.05, of the gates 0.02. + +_Habitat._--North Atlantic, Canary Islands (Lanzerote, Haeckel). + + + +Subfamily 2. HEXAPYLIDA, Haeckel. + +_Definition._--#Pylodiscida# with triopyle-shaped medullary shell, +surrounded by three distal arm-chambers, which are separated by three open +notches or gates. + + + +Genus 248. _Pylolena_,[287] n. gen. + +_Definition._--#Pylodiscida# with triopyle-shaped medullary shell, +surrounded by three distal arm-chambers. Notches between the three arms +open. + +The genus _Pylolena_ opens the series of the Hexapylida, or of those +Pylodiscida in which the centre of the shell is formed by a tri-radiated +medullary shell like _Triopyle_. In the equatorial plane of this +triopyle-shaped disk are developed on its margin three distal arm chambers, +as prolongations of the three arms of _Triopyle_, but much larger. In +_Pylolene_ the three angles or notches between the distal arms remain open, +repeating the form of _Triolene_. + + +{568}1. _Pylolena inermis_, n. sp. + +Arms club-shaped, at the base half as broad, at the rounded distal end as +broad as the triopyle-shaped medullary shell. Surface and margin smooth. + +_Dimensions._--Diameter of the cortical shell 0.15, of the medullary shell +0.05. + +_Habitat._--Equatorial Atlantic, Station 347, surface; Central Pacific, +Station 272, surface. + + +2. _Pylolena armata_, n. sp. (Pl. 48, fig. 15). + +Arms trapezoid, at the base half as broad, at the distal end twice as broad +as the triopyle-shaped medullary shell. Surface and margin thorny. Twelve +strong conical spines at the distal end of the three arms, two opposite on +both faces of the arm-edges. + +_Dimensions._--Diameter of the cortical shell 0.2, of the medullary shell +0.06. + +_Habitat._--South Atlantic, Station 325, surface. + + + +Genus 249. _Hexapyle_,[288] Haeckel, 1881, Prodromus, p. 464. + +_Definition._--#Pylodiscida# with triopyle-shaped medullary shell, +surrounded by three distal arm-chambers. Notches between the three arms +transformed into gates by a connecting equatorial girdle. + +The genus _Hexapyle_ differs from the preceding _Pylolene_ in the +development of an equatorial ring or latticed girdle, which connects the +free extremities of the three distal ends and transforms the open notches +between them into gates. It simulates therefore the formation of +_Triopyle_, from which it differs by duplication of the arm-joints and of +the gates (in each radius occur one proximal and one distal gate). + + +1. _Hexapyle triangula_, n. sp. + +Cortical shell triangular, with three rounded corners, three times as broad +as the triangular triopyle-shaped medullary shell. Surface smooth or rough, +but not spiny. Three arms two-thirds as broad as the three egg-shaped gates +of each side. + +_Dimensions._--Diameter of the cortical shell (or length of one side of the +triangle) 0.15, of the medullary shell 0.05; breadth of the gates 0.06, of +the bridges between them 0.04. + +_Habitat._--Pacific, central area, Station 272, depth 2600 fathoms. + + +2. _Hexapyle sexangula_, n. sp. + +Cortical shell hexagonal, with six equal sides, four times as broad as the +triangular triopyle-shaped medullary shell. Surface rough, but not spiny. +Three arms (on their smallest part) half as broad as the three triangular +gates (on their broadest part). + +{569}_Dimensions._--Diameter of the cortical shell 0.16, of the medullary +shell 0.04; breadth of the gates 0.06, of the bridges 0.03. + +_Habitat._--North Pacific, Station 244, depth 2900 fathoms. + + +3. _Hexapyle circularis_, n. sp. + +Cortical shell circular, four times as broad as the triangular, +Triopyle-shaped medullary shell. Surface smooth. Three arms half as broad +as the three kidney-shaped gates on each side of the shell. + +_Dimensions._--Diameter of the cortical shell 0.2, of the medullary shell +0.05; breadth of the gates 0.08, of the bridges between them 0.04. + +_Habitat._--Pacific, central area, Station 266, depth 2750 fathoms. + + +4. _Hexapyle triacantha_, n. sp. + +Cortical shell triangular, thorny, with three pointed corners, prolonged +into three strong conical radial spines; its diameter four times as great +as that of the medullary shell. Three arms of the same breadth as the three +egg-shaped gates of each side. + +_Dimensions._--Diameter of the cortical shell (or length of one side of the +triangle, without spines) 0.2, of the medullary shell 0.05; breadth of the +gates and of the bridges between them 0.06. + +_Habitat._--Indian Ocean, surface; Madagascar, Rabbe. + + +5. _Hexapyle hexacantha_, n. sp. + +Cortical shell hexagonal, thorny, three times as broad as the medullary +shell. Six stronger conical radial spines on the six corners at equal +distances, lying in the equatorial plane of the disk. Three half girdles +half as broad as the three triangular gates of each side. + +_Dimensions._--Diameter of the cortical shell 0.15, of the medullary shell +0.05; breadth of the gates 0.05, of the bridges 0.025. + +_Habitat._--North Pacific, Station 253, depth 3125 fathoms. + + +6. _Hexapyle dodecantha_, n. sp. (Pl. 48, fig. 16). + +Cortical shell triangular, thorny, with rounded corners, three and a half +times as broad as the medullary shell. Twelve stronger radial spines, six +opposite in pairs on each side of the discoidal shell, as prolongations of +the lateral edges of the triangular gates, which are about the same breadth +as the half girdles between them. + +_Dimensions._--Diameter of the cortical shell 0.21, of the medullary shell +0.06; breadth of the gates and of the bridges 0.06. + +_Habitat._--Pacific, central area, Station 270, surface. + + +{570}7. _Hexapyle polyacantha_, n. sp. + +Cortical shell circular, thorny, with a circle of numerous conical radial +spines in the periphery; its diameter nearly three times as great as that +of the medullary shell. Three half-girdles half as broad as the three +kidney-shaped gates on each side of the discoidal shell. + +_Dimensions._--Diameter of the cortical shell 0.11, of the medullary shell +0.04; breadth of the gates 0.04, of the bridges between them 0.02. + +_Habitat._--Pacific, central area, Station 271, depth 2425 fathoms. + + + +Genus 250. _Pylodiscus_,[289] n. gen. + +_Definition._--#Pylodiscida# with _Triopyle_-shaped medullary shell, +surrounded by three distal arm-chambers. Notches between the three arms +closed by lattice-work and by an equatorial girdle. + +The genus _Pylodiscus_ differs from _Hexapyle_ in the development of two +convex plates of lattice-work, which close the six open gates and transform +the disk into a biconvex fenestrated lens. _Pylodiscus_ simulates therefore +the characteristic form of _Triodiscus_; but whilst in the latter we find +only three arm-joints and three simple gates, their number is doubled in +the former. + + +1. _Pylodiscus triangularis_, n. sp. (Pl. 48, fig. 17). + + +Cortical shell triangular, with rounded corners, three times as broad as +the triangular, _Triopyle_-shaped medullary shell. Three arms about as +broad as the three egg-shaped gates between them. (Differs from _Hexapyle +triangula_ only by the delicate network of both triangular convex covering +plates, which close the open gates.) Six larger and many smaller spines on +the margin of the disk. + +_Dimensions._--Diameter of the disk 0.15, of the gates 0.05. + +_Habitat._--Pacific, central area, Station 270, depth 2925 fathoms. + + +2. _Pylodiscus sexangularis_, n. sp. + +Cortical shell hexangular, equilateral, four times as broad as the +circular, _Triopyle_-shaped medullary shell. Surface spiny. Three arms +nearly of the same form and size as the three triangular gates between +them. (Similar to _Hexapyle sexangularis_, but differing in the irregular +loose network closing the gates.) + +_Dimensions._--Diameter of the disk 0.18, of the gates 0.06. + +_Habitat._--North Pacific, south of Japan, Station 237, surface + + +{571}3. _Pylodiscus cardiopylus_, n. sp. + +Cortical shell hexangular, equilateral, five times as broad as the +triangular, _Triopyle_-shaped medullary shell. Surface smooth. Three arms +triangular, at the distal end as broad as the three heart-shaped gates. On +the margin six strong pyramidal spines in the equatorial plane (adradial, +as prolongations of the lateral arm-edges). + +_Dimensions._--Diameter of the disk 0.15, of the gates 0.05. + +_Habitat._--Indian Ocean, Sunda Strait, Rabbe. + + +4. _Pylodiscus nephropylus_, n. sp. + +Cortical shell circular, three times as broad as the circular, +_Triopyle_-shaped medullary shell. Surface spiny. Three arms trapezoidal, +half as broad as the three kidney-shaped gates. On the margin twelve +stronger, conical, radial spines, opposite in pairs on both sides of the +disk, disposed in six pairs at the distal end of the arms. + +_Dimensions._--Diameter of the disk 0.2, of the medullary shell 0.06. + +_Habitat._--Central Pacific, Station 268, depth 2900 fathoms. + + + +Subfamily 3. DISCOPYLIDA, Haeckel. + +_Definition._--#Pylodiscida# with _Triopyle_-shaped medullary shell and +_Pylodiscus_-shaped cortical shell, which is surrounded by a marginal +chambered equatorial girdle. + + + +Genus 251. _Discozonium_,[290] n. gen. + +_Definition._--#Pylodiscida# with _Triopyle_-shaped medullary shell and +_Pylodiscus_-shaped cortical shell, which is surrounded by an equatorial +chambered girdle. No peculiar osculum on the margin of the disk. + +The genus _Discozonium_ and the following _Discopyle_ make up together the +small group of the Discopylida, or those Pylodiscida in which a discoidal +shell like _Pylodiscus_ is surrounded by a marginal equatorial girdle; this +girdle is divided into twelve to twenty-four or more chambers by radial +beams, which are the external prolongations of the radial marginal spines +of _Pylodiscus_. The latter genus bears therefore to _Discozonium_ the same +relation as _Sethodiscus_ in the other #Discoidea# does to _Lithocyclia_, +or _Phacodiscus_ to _Coccodiscus_. + + +1. _Discozonium cyclonium_, n. sp. + +Disk circular, lenticular, with smooth margin, three times as broad as the +triangular, _Triopyle_-shaped medullary shell. Three gates of the cortical +shell kidney-shaped, twice as broad as the three {572}arms. Chambered +equatorial girdle with twenty to twenty-four subregular chambers (similar +to _Discopyle osculata_, Pl. 48, fig. 19, but without any marginal +osculum). + +_Dimensions._--Diameter of the disk 0.2, of the cortical shell 0.14, of the +medullary shell 0.07. + +_Habitat._--Central Pacific, Station 265, depth 2900 fathoms. + + +2. _Discozonium trigonium_, n. sp. + +Disk triangular, with thorny margin, four times as broad as the triangular, +_Triopyle_-shaped medullary shell. Three gates of the cortical shell +egg-shaped, scarcely as broad as the three arms. Chambered equatorial +girdle with twenty-four to thirty irregular chambers. + +_Dimensions._--Diameter of the disk 0.24, of the cortical shell 0.2, of the +medullary shell 0.06. + +_Habitat._--Central Pacific, Station 274, depth 2750 fathoms. + + +3. _Discozonium hexagonium_, n. sp. (Pl. 48, fig. 18). + +Disk hexagonal, with spiny margin, four times as broad as the triangular, +_Triopyle_-shaped medullary shell. Three gates of the cortical shell +kidney-shaped, one and a half times as broad as the arms. Chambered +equatorial girdle with twelve large regular chambers; the radial beams +between them are prolonged into twelve strong pyramidal marginal spines +(three perradial on the ends of the arms, three interradial on the radii of +the gates, six adradial between the former and latter). + +_Dimensions._--Diameter of the disk 0.2, of the cortical shell 0.12, of the +medullary shell 0.05. + +_Habitat._--Central Pacific, Station 271, depth 2425 fathoms. + + + +Genus 252. _Discopyle_,[291] n. gen. + +_Definition._--#Pylodiscida# with _Triopyle_-shaped medullary shell and +_Pylodiscus_-shaped cortical shell, which is surrounded by an equatorial +chambered girdle. One peculiar osculum, surrounded by a corona of spines, +on the margin of the disk. + +The genus _Discopyle_ differs from the preceding genus _Discozonium_ in the +development of a peculiar marginal osculum, and bears therefore to it the +same relation as, in the Porodiscida, _Ommatodiscus_ does to _Porodiscus_ +(compare above, p. 500). This peculiar osculum is here also surrounded by a +corona of spines, and serves probably for the exit or outlet of a bunch of +pseudopodia or a "sarcode-flagellum." Only two species of _Discopyle_ have +been observed, which represent perhaps better two different genera; in one +species the disk is circular, in the other elliptical. In this latter the +osculum lies on one pole of the main axis. + + +{573}1. _Discopyle osculata_, n. sp. (Pl. 48, fig. 19). + +Disk circular with spiny margin, three times as broad as the triangular, +_Triopyle_-shaped medullary shell. Three gates of the cortical shell +kidney-shaped, on the inside with an interradial spine, twice as broad as +the three pentagonal arms. Chambered equatorial girdle with twenty-four +subregular chambers, in the radius of one odd gate with a large marginal +osculum, which is as broad as the medullary shell, and surrounded by a +dense corona of twenty to thirty strong conical spines. + +_Dimensions._--Diameter of the disk 0.15, of the cortical shell 0.1, of the +medullary shell 0.05, of the marginal osculum 0.06. + +_Habitat._--Central Pacific, Station 272, depth 2600 fathoms. + + +2. _Discopyle elliptica_, n. sp. (Pl. 48, fig. 20). + +Disk elliptical, four-fifths as broad as long, with spiny margin, three +times as broad as the triangular, _Triopyle_-shaped medullary shell. Three +gates of the cortical shell roundish, on the inside with an interradial +spine, little broader than the quadrangular arms. Chambered equatorial +girdle with twenty to thirty irregular chambers, on one pole of the main +axis with a large marginal osculum, which is one-third as broad as the +length of the main axis, and armed with a corona of twenty to thirty short +conical spines. The osculum does not correspond to a certain radius. + +_Dimensions._--Diameter of the disk 0.15, of the cortical shell 0.08, of +the medullary shell 0.04, of the marginal osculum 0.05. + +_Habitat._--Central Pacific, Station 267, depth 2700 fathoms. + + + +Family XXIII. #SPONGODISCIDA#, Haeckel (Pl. 41, fig. 11). + + _Spongodiscida et Spongocyclida_, Haeckel, 1862, Monogr. d. Radiol., + pp. 452, 460, 469. + _Spongodiscida_, Haeckel, 1881, Prodromus, p. 461. + _Calodictya_, Ehrenberg, 1847, Monatsber. d. k. preuss. Akad. d. Wiss. + Berlin, p. 53 (_partim_). + +_Definition._--#Discoidea# without a phacoid shell, with a flat discoidal +shell, in which a simple spherical central chamber is surrounded by an +irregular spongy framework (sometimes with concentric rings around the +central chamber). Surface of the disk quite spongy, without porous +sieve-plates. + +The family #Spongodiscida# is the sixth and last family of the #Discoidea#, +and bears to the other families of this group the same relation as the +family Spongosphaerida does to the other #Sphaeroidea#, or the Spongurida +to the other #Prunoidea#. Its characteristic structure consists in the +irregular spongy framework of the disk, and mainly in the rough, irregular +shape of its spongy surface, which is never covered with porous plates +(neither phacoid shell nor corresponding sieve-plates), as in all other +#Discoidea#. Of course a little spongy structure occurs also in many +Porodiscida {574}and even in some Coccodiscida (principally in the +peripheral part of the disk or its chambered arms); but both flat (or +convex) surfaces of the disk (at least in the central part) remain here +constantly as simple lattice-plates, whilst in all Spongodiscida the whole +surface of the disk is spongy. + +When I constituted the family Spongodiscida in my Monograph (1862, pp. 452, +460) I had separated from them the Spongocyclida, exhibiting in the central +part of the disk a more or less distinct concentric arrangement of the +spongy chambers, whilst in the former the delicate spongy framework is +quite irregular, composed of branched siliceous threads, connected and +interwoven in all directions. But in all Spongocyclida the whole surface of +the spongy disk is quite as irregularly rough and deprived of smooth +sieve-plates as in all true Spongodiscida, and the more or less concentric +structure of the central part of the disk in the former (very variable and +often scarcely able to be recognised) seems not sufficient to separate both +groups; even the single genera cannot be sufficiently separated by this +character. I now therefore give up entirely the group of Spongocyclida (as +already done in my Prodromus, 1881). Nevertheless the concentric annular +structure in the dark central part of some Spongodiscida is very +interesting as transition to the Porodiscida; it indicates already that the +former are derived from the latter. Even the single genera in both +families are corresponding. + +In the new system of "Polycystina," which Ehrenberg gave, 1875 (Abhandl. d. +k. Akad. d. Wiss. Berlin, p. 157), are enumerated under the _Calodictya_ +four genera "with spongy disk," viz., _Spongodiscus_, _Rhopalodictyum_, +_Dictyocoryne_, _Spongaster_. Indeed these four genera, which I here +retain, are true Spongodiscida, and must be separated from the other +_Calodictya_, the greater part of which are Porodiscida. The number of +species of true Spongodiscida now amounts to sixty-seven, which I dispose +in thirteen genera. + +The whole family may be divided into three subfamilies. The first of these +are the Spongophacida (corresponding to the Trematodiscida among the +Porodiscida), in which the circular margin of the spongy disk bears no +radial appendages; either the margin is quite simple, spongy +(_Spongodiscus_), or surrounded by a hyaline, solid, or porous equatorial +girdle (_Spongophacus_). The disk is either more lenticular (biconvex) or +more flat discoidal (a shortened cylinder), rarely a little biconcave +(thicker at the margin than in the centre). The spongy framework of the +solid disk is either quite irregular (_Spongodisculus_), or in the central +part with concentric circular rings (_Spongocyclia_), or in the central +part spirally convoluted (_Spongospira_). + +The second subfamily, Spongotrochida, corresponds to the Stylodictyida +(among the #Porodiscida#), and is distinguished by solid radial spines on +the margin of the disk, disposed in the equatorial plane either irregularly +or regularly (after the same order as in the other families of +#Discoidea#). + +The third subfamily, Spongobrachida, correspond perfectly to the +Euchitonida {575}(among the Porodiscida), bearing on the disk-margin two, +three, or four spongy arms, commonly disposed regularly in the equatorial +plane. Here also occurs the peculiar formation of a "patagium," or of an +interbrachial spongy framework different from that of the arms, which +connects the arms like a web-membrane in the equatorial plane. + +The spongy framework exhibits in all these Spongodiscida no remarkable +differences, being everywhere composed of fine branched solid siliceous +threads, interwoven in all directions, with irregular meshes of very +different size. + +The central capsule of all Spongodiscida is filled up with the same spongy +framework which covers also both its sides. It grows according to the +enveloping skeleton, but remains constantly smaller. The form of the +central capsule is circular (lenticular or discoidal) in the Spongophacida +and Spongotrochida, whilst in the Spongobrachida it enters into the radial +spongy arms, developed from the margin of the spongy disk. + +_Synopsis of the Genera of the Spongodiscida._ + + {Spongy disk with simple + I. Subfamily { margin (without peculiar + Spongophacida. { equatorialgirdle), 253. _Spongodiscus_. + Spongy disk { + without radial {Spongy disk with a peculiar + appendages. { (solid or porous) equatorial + { girdle, 254. _Spongophacus_. + + { {Two opposite + { { spines, 255. _Spongolonche_. + II. Subfamily {Few (two, { + Spongotrochida. { three, or {Three marginal + Spongy disk with { four) radial { spines, 256. _Spongotripus_. + solid radial { spines { + spines on the { regularly {Four crossed + margin (in the { disposed. { spines, 257. _Spongostaurus_. + equatorial { + plane). { {Spines only + {Numerous (five { on the + { to ten or { margin + { more) radial { (equatorial), 258. _Stylotrochus_. + { spines, { + { often {Spines on both + { irregularly { sides of the + { disposed. { disk, 259. _Spongotrochus_. + + { {Without a + {Two arms, { patagium, 260. _Spongolena_. + { opposite in { + { one axis. {With a + { { patagium, 261. _Spongobrachium_. + III. Subfamily { + Spongobrachida. { {Without + Spongy disk with { { a patagium, 262. _Rhopalodictyum_. + spongy radial {Three arms on { + arms on the { the margin. {With a + margin (in the { { patagium, 263. _Dictyocoryne_. + equatorial { + plane). { {Without + { { a patagium, 264. _Spongasteriscus_. + {Four arms in { + { cross form. {With a + { { patagium, 265. _Spongaster_. + + + +Subfamily 1. SPONGOPHACIDA, Haeckel, 1881, Prodromus, p. 461. + +_Definition._--#Spongodiscida# with a simple circular disk, without radial +appendages on the margin (neither solid spines nor chambered arms). + + + +{576}Genus 253. _Spongodiscus_,[292] Ehrenberg, 1854, Monatsber. d. k. +preuss. Akad. d. Wiss. Berlin, p. 237. + +_Definition._--#Spongodiscida# with a simple circular disk, without radial +appendages and without an equatorial girdle on the margin. + +The genus _Spongodiscus_ represents the most simple and primitive form of +the Spongodiscida, or of those #Discoidea# in which the central disk is +more or less spongy, composed of an irregular fine framework. In my +Monograph (1862, pp. 452, 460, 469) I had separated the true _Spongodiscus_ +(first described by Ehrenberg, _loc. cit._) and the _Spongocyclia_; the +former being characterised by the irregular spongy framework of the whole +disk, whilst in the latter this framework includes in the central part some +concentric circular rings (approaching _Porodiscus_). In the same way +afterwards Stoehr (1880, _loc. cit._) separated the genus _Spongospira_ as +spongy disks, which include in the central part some spiral convolutions. +But as these differences are rather inconstant and not sharply discernible, +I think it now better to regard these three forms as subgenera of +_Spongodiscus_. All three have the common simple circular disk, without any +marginal appendages. + + + +Subgenus 1. _Spongodisculus_, Haeckel. + +_Definition._--Spongy framework of the disk quite irregular, without +concentric rings or spiral convolutions. + + +1. _Spongodiscus mediterraneus_, Haeckel. + + _Spongodiscus mediterraneus_, Haeckel, 1862, Monogr. d. Radiol., p. 461, + Taf. xii. figs. 14, 15. + +Spongy disk plain on both sides, with quite an irregular framework, without +concentric rings and without radial piercing beams. Texture everywhere +uniform; meshes eight to ten times as broad as the bars. + +_Dimensions._--Diameter of the disk 0.08 to 0.24, of the meshes 0.005 to +0.008. + +_Habitat._--Mediterranean (Messina), Haeckel; also fossil in the Tertiary +rocks of Sicily (Grotte), Stoehr. + + +2. _Spongodiscus radiatus_, n. sp. + +Spongy disk plain on both sides, with quite irregular framework, without +concentric rings, but with numerous piercing radial beams which are not +prolonged into marginal spines. Texture everywhere uniform; meshes once and +a half to twice as broad as the bars. + +_Dimensions._--Diameter of the disk 0.12 to 0.15, of the meshes 0.002 to +0.003. + +_Habitat._--Pacific, central area, Station 268, depth 2900 fathoms. + + +{577}3. _Spongodiscus resurgens_, Ehrenberg. + + _Spongodiscus resurgens_, Ehrenberg, 1854, Mikrogeol., Taf. xxxvB. B. + iv., fig. 16. + + _Spongodiscus resurgens_, Stoehr, 1880, Palaeontogr., xxvi. p. 117, Taf. + vi. fig. 11. + +Spongy disk lenticular, biconvex, in the darker centre much thicker than +towards the thin periphery, with an irregular framework, without concentric +rings, but with numerous piercing radial beams. Texture equal; meshes three +to four times as broad as the bars. + +_Dimensions._--Diameter of the disk 0.1 to 0.3, of the meshes 0.003 to +0.006. + +_Habitat._--Cosmopolitan; Mediterranean, Atlantic, Pacific, surface; also +fossil in the Tertiary rocks of Sicily and Barbados. + + +4. _Spongodiscus favus_, Ehrenberg. + + _Spongodiscus favus_, Ehrenberg, 1861, Monatsber. d. k. preuss. Akad. d. + Wiss. Berlin, p. 301. + +Spongy disk lenticular, biconvex, in the darker centre much thicker than +towards the periphery, with an irregular framework, without concentric +rings. Texture different, in the outer half with numerous radial beams and +loose network, the meshes of which are three to four times as large as in +the darker and denser framework of the centre. + +_Dimensions._--Diameter of the disk 0.2, of the outer meshes 0.008 to +0.012, of the inner meshes 0.002 to 0.003. + +_Habitat._--North Atlantic, Greenland, Faeroee Channel (John Murray), +surface. + + +5. _Spongodiscus biconcavus_, n. sp. + +Spongy disk biconcave, in the peripheral, ring-like, thickened part twice +as thick as in the hollowed central part, with an irregular framework, +without concentric rings. Texture different, in the outer half looser than +in the inner, darker part; meshes of the outer part five to six times, of +the inner twice to three times, as broad as the bars. + +_Dimensions._--Diameter of the disk 0.25, of the outer meshes 0.01 to +0.012, of the inner 0.004 to 0.006. + +_Habitat._--Pacific, central area, Station 265, depth 2900 fathoms. + + + +Subgenus 2. _Spongocyclia_, Haeckel, 1862, Monogr. d. Radiol., p. 469. + +_Definition._--Spongy framework of the disk in the inner part with +concentric, circular rings, in the outer part irregular. + + +{578}6. _Spongodiscus cycloides_, Haeckel. + + _Spongodiscus cycloides_, Haeckel, 1860, Monatsber. d. k. preuss. Akad. + d. Wiss. Berlin, p. 843. + + _Spongocyclia cycloides_, Haeckel, 1862, Monogr. d. Radiol., p. 469, Taf. + xxviii. fig. 1. + +Spongy disk on both sides plain, in the central part with five to ten +concentric, circular rings, in the peripheral part quite irregularly and +densely spongy. Meshes twice to four times as broad as the bars. + +_Dimensions._--Diameter of the disk 0.1 to 0.2, of the meshes 0.003 to +0.006. + +_Habitat._--Mediterranean (Messina), North Atlantic (Canary Islands). + + +7. _Spongodiscus spongocyclia_, Haeckel. + + _Spongocyclia triangularis_, Stoehr, 1880, Palaeontogr., vol. xxvi. p. + 119, Taf. vii. fig. 5. + +Spongy disk lenticular, in the thicker central part with eleven to twelve +circular, concentric rings, in the thinner, peripheral zone irregularly +spongy. Meshes twice to four times as broad as the bars. (The triangular +form in the specimen figured by Stoehr is accidental, produced by the +broken margin.) + +_Dimensions._--Diameter of the disk 0.2 to 0.3, of the meshes 0.006 to +0.008. + +_Habitat._--Fossil in Tertiary rocks of Barbados (Haeckel) and Sicily +(Stoehr). + + + +Subgenus 3. _Spongospira_, Stoehr, 1880, Palaeontogr., vol xxvi. p. 120. + +_Definition._--Spongy framework of the disk in the inner part with spiral +convolutions, in the outer part irregular. + + +8. _Spongodiscus florealis_, Haeckel. + + _Spongospira florealis_, Stoehr, 1880, Palaeontogr., vol. xxvi. p. 120, + Taf. vii. fig. 6. + +Spongy disk lenticular, in the thicker central part with five to six spiral +convolutions, in the outer peripheral zone irregularly spongy. No radial +beams piercing the framework. Meshes three to four times as broad as the +bars. + +_Dimensions._--Diameter of the disk 0.26, of the meshes 0.006 to 0.008. + +_Habitat._--Fossil in Tertiary rocks of Sicily (Grotte), Stoehr. + + +9. _Spongodiscus spiralis_, n. sp. + + _Spongospira spiralis_, Haeckel, 1881, Prodromus. + +Spongy disk on both sides plain, with twelve to sixteen spiral convolutions +in the central part, with irregular, spongy framework in the outer part, +pierced by numerous interrupted radial beams. Meshes five to six times as +broad as the bars. + +_Dimensions._--Diameter of the disk 0.2 to 0.3, of the meshes 0.01 to +0.012. + +_Habitat._--Antarctic Ocean, Station 157, depth 1950 fathoms. + + + +{579}Genus 254. _Spongophacus_,[293] Haeckel, 1881, Prodromus, p. 461. + +_Definition._--#Spongodiscida# with a simple circular disk, without radial +appendages, on the margin surrounded by a thin porous or solid equatorial +girdle. + +The genus _Spongophacus_, represented hitherto only by a single but +interesting species, differs from _Spongodiscus_ by the peculiar girdle +which surrounds the margin of the disk in the equatorial plane. It +simulates the same formation as _Perichlamydium_ in the Porodiscida, and +resembles also _Periphaena_, &c., in the Phacodiscida. + + +1. _Spongophacus periphaena_, n. sp. + +Spongy disk lenticular, with an irregular, dense framework, in the centre +darker than in the peripheral part. Margin of the disk very thin, +surrounded by a broad, circular girdle, lying in the equatorial plane, +about as broad as the half radius of the spongy disk. The inner part of the +girdle is perforated by numerous irregular, small pores, which pass over +gradually into the spongy meshes; the outer part is quite homogeneous, +solid, transparent, with an extremely thin margin. + +_Dimensions._--Diameter of the disk 0.2; breadth of the girdle 0.05. + +_Habitat._--Pacific, central area, Station 271, depth 2425 fathoms. + + + +Subfamily 2. SPONGOTROCHIDA, Haeckel, 1881, Prodromus, p. 461. + +_Definition._--#Spongodiscida# with a circular disk, the margin of which is +armed with solid radial spines, situated in the equatorial plane (rarely +also on both sides of the disk with radial spines). + + + +Genus 255. _Spongolonche_,[294] Haeckel, 1881, Prodromus, p. 461. + +_Definition._--#Spongodiscida# with two solid marginal spines, opposite in +one equatorial diameter of the disk. + +The genus _Spongolonche_ opens the series of the Spongotrochida, or of +those Spongodiscida in which the margin of the disk is armed with solid +radial spines, situated in the equatorial plane. _Spongolonche_ possesses +only two such spines, opposite in one equatorial diameter of the disk; it +corresponds therefore to _Stylocyclia_ among the Coccodiscida, to +_Xiphodictya_ among the Porodiscida. + + +{580}1. _Spongolonche conostyla_, n. sp.. + +Spongy disk circular, with irregular framework, without concentric rings. +Both opposite radial spines conical, about as long as the radius of the +disk, and four times as long as broad at the base. Margin of the disk +nearly smooth. + +_Dimensions._--Diameter of the disk 0.16; length of the radial spines 0.18, +basal thickness 0.045. + +_Habitat._--Pacific, central area, Station 268, depth 2900 fathoms. + + +2. _Spongolonche amphistyla_, n. sp. + +Spongy disk circular, with four to six concentric rings in the inner part, +with quite an irregular framework in the outer part. Both opposite radial +spines cylindrical, twice to three times as long as the diameter of the +disk, at the base about as broad as two meshes of the framework. Margin of +the disk ciliated. + +_Dimensions._--Diameter of the disk 0.2; length of the radial spines 0.4 to +0.6, basal thickness 0.01. + +_Habitat._--Pacific, central area, Station 271, depth 2425 fathoms. + + + +Genus 256. _Spongotripus_,[295] Haeckel, 1881, Prodromus, p. 461. + +_Definition._--#Spongodiscida# with three solid radial spines on the margin +of the circular or triangular disk. + +The genus _Spongotripus_ is characterised by three marginal spines, which +are commonly regularly disposed, more rarely in a bilateral or an irregular +manner. It corresponds to _Trigonocyclia_ among the Coccodiscida, to +_Tripodictya_ among the Porodiscida. + + + +Subgenus 1. _Spongotripodiscus_, Haeckel. + +_Definition._--Radial spines of equal size and distance; triangle regular. + + +1. _Spongotripus regularis_, n. sp. + +Spongy disk circular; three radial spines on its margin of equal size and +equidistant, strong, conical, about as long as the diameter of the disk, +and five times as long as broad at the base. + +_Dimensions._--Diameter of the disk 0.15; length of the spines 0.16, basal +breadth 0.03. + +_Habitat._--Pacific, central area, Station 272, surface. + + +{581}2. _Spongotripus neumayri_, Haeckel. + + _Spongechinus neumayri_, Dunikowski, 1882, Denskchr. d. k. Akad. d. Wiss. + Wien, xlv. p. 28, Taf. v. fig. 59. + +Spongy disk circular, nearly spherical; three radial spines on its margin +of equal size and equidistant, pyramidal, nearly as long as the diameter of +the disk, and three times as long as broad at the base. + +_Dimensions._--Diameter of the disk 0.15 to 0.2; length of the spines 0.11, +basal breadth 0.04. + +_Habitat._--Fossil in the Jura of the Alps and in Tertiary rocks of +Barbados. + + +3. _Spongotripus strepsiceros_, n. sp. + +Spongy disk circular; three radial spines on its margin of equal size and +equidistant, angular, twice as long as the diameter of the disk, spirally +twisted like the horns of Antilope strepsiceros. + +_Dimensions._--Diameter of the disk 0.15; length of the spines 0.3, basal +breadth 0.02. + +_Habitat._--Pacific, central area, Station 272, depth 2600 fathoms. + + + +Subgenus 2. _Spongotripodium_, Haeckel. + +_Definition._--Radial spines of different size or at different distances; +triangle either isosceles or irregular. + + +4. _Spongotripus ypsilon_, n. sp. + +Spongy disk triangular, isosceles, with convex sides; three spines angular, +of different size and at different distances; the odd spine straight and +twice as long as the two paired spines, which are more approximated and +curved concavely one to the other, like y. + +_Dimensions._--Diameter of the disk 0.12; length of the odd spine 0.2, of +the paired spines 0.1, basal breadth 0.04. + +_Habitat._--Pacific, central area, Station 274, depth 2750 fathoms. + + +5. _Spongotripus irregularis_, n. sp. + +Spongy disk circular; three spines conical, irregularly curved, all three +of different size, and at irregular distances; once to three times as long +as the diameter of the disk; margin of the disk thorny. + +_Dimensions._--Diameter of the disk 0.1; length of the spines 0.1 to 0.3, +basal breadth 0.05. + +_Habitat._--South Pacific, Station 300, depth 1375 fathoms. + + + +{582}Genus 257. _Spongostaurus_,[296] Haeckel, 1881, Prodromus, p. 461. + +_Definition._--#Spongodiscida# with four solid radial spines on the margin +of the circular or square disk, commonly crossed in two equatorial +diameters perpendicular one to another. + +The genus _Staurodictya_ exhibits four marginal spines in cross form. +Commonly the cross is regular and rectangular, the four spines being +opposite in pairs in two perpendicular diameters; sometimes more or less +irregular. The genus repeats _Staurodictya_ among the Porodiscida, +_Staurocyclia_ among the Coccodiscida. + + +1. _Spongostaurus cruciatus_, n. sp. + +Spongy disk circular; four radial spines on its margin opposite in two +crossed equatorial diameters, perpendicular one to another, conical, about +as long as the diameter of the disk. + +_Dimensions._--Diameter of the disk 0.16; length of the spines 0.18, basal +breadth 0.04. + +_Habitat._--North Pacific, Station 244, depth 2900 fathoms. + + +2. _Spongostaurus serratus_, n. sp. + +Spongy disk circular; four crossed radial spines very large, twice to three +times as long as the diameter of the central disk, serrated on both edges, +with two rows of strong conical perpendicular teeth (similar to the saw of +_Pristis antiquorum_). + +_Dimensions._--Diameter of the disk 0.1; length of the spines 0.2 to 0.3, +breadth 0.02. + +_Habitat._--Indian Ocean, Madagascar, Rabbe, surface. + + +3. _Spongostaurus hastatus_, n. sp. + +Spongy disk square, with concave sides; four crossed radial spines +cylindrical, on the broader distal end spear-shaped or nearly lanceolate, +one and a half times as long as the diameter of the disk. + +_Dimensions._--Diameter of the disk 0.13; length of the spines 0.2, basal +breadth 0.01, distal breadth 0.03. + +_Habitat._--Tropical Atlantic, Station 347, surface. + + +4. _Spongostaurus quadratus_, n. sp. + +Spongy disk square, with rectilinear sides; four crossed radial spines +pyramidal, arising from the corners of the square, about as long as its +half diagonal. + +_Dimensions._--Diameter of the disk 0.16; length of the spines 0.08, basal +breadth 0.02. + +_Habitat._--Pacific, central area, Station 271, surface. + + + +{583}Genus 258. _Stylotrochus_,[297] Haeckel, 1862, Monogr. d. Radiol., p. +463. + +_Definition._--#Spongodiscida# with numerous solid radial spines on the +margin of the disk (five to ten or more), all situated in the equatorial +plane. + +The genus _Stylotrochus_ comprises those Spongodiscida in which the margin +of the circular disk bears numerous radial spines. All these spines lie in +the same equatorial plane, whilst in the following genus they are disposed +over the whole surface of the disk. _Stylotrochus_ corresponds to +_Astrocyclia_ among the Coccodiscida, to _Stylodictya_ among the +Porodiscida. The spongy framework of the disk is either quite irregular +(_Stylotrochiscus_), or includes in the middle part some concentric +circular rings (_Stylospongia_). + + + +Subgenus 1. _Stylotrochiscus_, Haeckel. + +_Definition._--Spongy framework of the whole disk irregular, without +concentric circular rings or spiral convolutions. + + +1. _Stylotrochus arachnius_, Haeckel. + + _Spongotrochus arachnius_, Haeckel, 1862, Monogr. d. Radiol., p. 464. + +Spongy framework of the whole disk irregular. Eight to twelve marginal +spines very long and thin, bristle-shaped, twice to four times as long as +the diameter of the disk. (Very similar to the common _Stylodictya +arachnia_, but without concentric circular rings and sieve-plates, with +quite irregular network of fine bars.) + +_Dimensions._--Diameter of the disk 0.12 to 0.15; length of the radial +spines 0.2 to 0.6, basal breadth 0.001. + +_Habitat._--Cosmopolitan; Mediterranean, Atlantic, Indian, Pacific, +surface; also fossil in Tertiary rocks of Barbados and the Mediterranean. + + +2. _Stylotrochus craticulatus_, Haeckel. + + _Spongotrochus craticulatus_, Stoehr, 1880, Palaeontogr., vol. xxvi. p. + 118, Taf. vi. fig. 12. + + ? _Spongodiscus aculeatus_, Ehrenberg, 1854, Monatsber. d. k. preuss. + Akad. d. Wiss. Berlin, p. 246. + +Spongy framework of the whole disk irregular. Sixteen to twenty short +marginal spines (twice to four times as long as the diameter of one mesh of +the framework), free prolongations of internal radial beams which arise +from the darker centre of the disk. (The interruption of the disk-margin on +one point of its circumference, figured by Stoehr as osculum or +"Muendungs-Oeffnung," is probably an accidental abnormality; I did not find +it in other specimens.) + +{584}_Dimensions._--Diameter of the disk 0.2 to 0.25; length of the radial +spines 0.005 to 0.018, basal breadth 0.001 to 0.003. + +_Habitat._--Pacific, central area, Stations 266 to 268, surface; fossil in +Barbados and Sicily. + + +3. _Stylotrochus helianthus_, n. sp. + +Spongy framework of the whole disk irregular. Thirty to fifty very large, +conical radial spines, about as long as the diameter of the disk, and at +the base two to four times as broad as one mesh of the framework (without +internal prolongations). + +_Dimensions._--Diameter of the disk 0.15 to 0.2; length of the radial +spines 0.16 to 0.24, basal breadth 0.008 to 0.016. + +_Habitat._--Pacific, central area, Station 272, surface. + + +4. _Stylotrochus rhabdostylus_, Haeckel. + + _Spongosphaera rhabdostyla_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. + Wiss. Berlin, p. 256, Taf. xxvi. figs. 1, 2. + +Spongy framework of the whole disk irregular. Four very large marginal +primary spines crossed in two equatorial diameters, perpendicular one to +another, and between them numerous (twelve to twenty or more) smaller +secondary spines. The latter arise from the margin, whilst the former +pierce the disk and are nearly united in its centre. All the spines are +cylindrical, the smaller as broad as one mesh, the larger three to six +times as broad. + +_Dimensions._--Diameter of the disk 0.2; length of the four main spines +0.15 to 0.3, breadth 0.01 to 0.02; length of the accessory spines 0.05 to +0.1, breadth 0.005. + +_Habitat._--Fossil in the rocks of Barbados. + + +5. _Stylotrochus heteracanthus_, Haeckel. + + _Spongotrochus heteracanthus_, Haeckel, 1862, Monogr. d. Radiol., p. 464. + +Spongy framework of the whole disk irregular. Ten very long needle-shaped +marginal spines (symmetrically distributed), and between them numerous very +fine, shorter, accessory, bristle-shaped spines. + +_Dimensions._--Diameter of the disk 0.16; length of the main spines 0.16, +basal breadth 0.002; length of the secondary spines 0.03. + +_Habitat._--Mediterranean (Messina), surface. + + + +Subgenus 2. _Stylospongia_, Haeckel, 1862, Monogr. d. Radiol., p. 473. + +_Definition._--Spongy framework of the disk in the inner part with +concentric rings or spiral convolutions, in the outer part quite irregular. + + +{585}6. _Stylotrochus huxleyi_, Haeckel. + + _Stylospongia huxleyi_, Haeckel, 1862, Monogr. d. Radiol., p. 473, Taf. + xxviii. fig. 7. + +Spongy framework of the disk in the inner part with five concentric rings, +in the outer part quite irregular. Ten marginal spines, conical at the +base, about as long as the radius of the disk, without inner piercing +prolongations. + +_Dimensions._--Diameter of the disk 0.12; length of the radial spines 0.06, +basal breadth 0.003. + +_Habitat._--Mediterranean (Messina), Haeckel. + + +7. _Stylotrochus geddesii_, n. sp. (Pl. 41, fig. 11). + + _Stylospongidium geddesii_, Haeckel, 1881, Atlas (pl. xli. fig. 11). + +Spongy framework of the disk in the inner part with four to eight +concentric rings (or partially spiral convolutions), in the outer part +quite irregular. Thirty to fifty pyramidal marginal spines of variable +size, one-fourth to one-half as long as the radius of the disk, outer +prolongations of inner piercing radial beams, which arise from various +concentric rings. I call this interesting species, which is intermediate +between _Stylodictya_ and _Stylotrochus_, in honour of the morphologist Mr. +Patrick Geddes of Edinburgh. + +_Dimensions._--Diameter of the disk 0.15 to 0.25; length of the radial +spines 0.03 to 0.06, basal breadth 0.004 to 0.01. + +_Habitat._--Pacific, central area, Stations 270 to 274, in 2350 to 2925 +fathoms. + + + +Genus 259. _Spongotrochus_,[298] Haeckel, 1860, Monatsber. d. k. preuss. +Akad. d. Wiss. Berlin, p. 844. + +_Definition._--#Spongodiscida# with numerous solid radial spines (five to +ten or more), which are scattered over the whole surface and the margin of +the disk, or regularly disposed on both sides of it. + +The genus _Spongotrochus_ differs from the foregoing and nearly allied +genus by the distribution of the numerous radial spines. These are not +confined to the margin of the disk, but also scattered on its whole +surface, and sometimes symmetrically disposed on both its sides in a +regular manner. Also in this genus the spongy framework is sometimes quite +irregular (_Spongotrochiscus_), at other times in the middle part with +enclosed concentric rings (_Stylospongidium_). + + + +Subgenus 1. _Spongotrochiscus_, Haeckel, 1862, Monogr. d. Radiol., p. 463. + +_Definition._--Spongy framework of the whole disk irregular, without +concentric rings or spiral convolutions. + + +{586}1. _Spongotrochus brevispinus_, Haeckel. + + _Spongotrochus brevispinus_, Haeckel, 1862, Monogr. d. Radiol., p. 462, + Taf. xxvii. figs. 4, 5. + +Spongy framework of the whole disk irregular, everywhere equal. The whole +surface of the disk covered with numerous short, needle-shaped, radial +spines, about as long as the thickness of the disk, which is one-fifth of +its diameter. + +_Dimensions._--Diameter of the disk 0.18; length of the radial spines 0.03 +to 0.04, basal breadth 0.002. + +_Habitat._--Cosmopolitan; Mediterranean, Atlantic, Pacific, surface. + + +2. _Spongotrochus multispinus_, n. sp. + +Spongy framework of the whole disk irregular, in the centre darker. The +whole surface of the disk covered with numerous conical radial spines, +about as long as the radius of the disk. + +_Dimensions._--Diameter of the disk 0.22; length of the radial spines 0.1, +basal breadth 0.008. + +_Habitat._--Pacific, central area, Stations 271 to 274, surface. + + +3. _Spongotrochus longispinus_, Haeckel. + + _Spongotrochus longispinus_, Haeckel, 1862, Monogr. d. Radiol., p. 463, + Taf xxvii. figs. 2, 3. + +Spongy framework of the whole disk irregular, everywhere equal. Surface +thorny. Twenty long, needle-shaped, radial spines, about as long as the +diameter of the disk, symmetrically distributed in pairs on both flat sides +of the disk, so that the opposite pairs lie in five equidistant, meridian +planes (compare the figures). + +_Dimensions._--Diameter of the disk 0.2; length of the twenty radial spines +0.2, basal breadth 0.001. + +_Habitat._--Mediterranean (Messina), surface. + + + +Subgenus 2. _Stylospongidium_, Haeckel, 1881, Prodromus, p. 460. + +_Definition._--Spongy framework of the disk in the inner part with +concentric rings or spiral convolutions, in the outer part quite irregular. + + +4. _Spongotrochus scutella_, n. sp. + + _Spongotrochus ehrenbergii_, Buetschli, 1882, L. N. 41, Taf. xxvi. figs. + 1_a_, 1_b_. + +Spongy framework of the disk in the inner part with four to six concentric +rings, in the outer part quite irregular. The whole surface of the disk +covered with bristle-shaped radial spines, about half as long as the radius +of the disk. + +_Dimensions._--Diameter of the disk 0.24; length of the radial spines 0.06, +basal breadth 0.02. + +_Habitat._--Antarctic Ocean, Station 157, depth 1950 fathoms. + + +{587}5. _Spongotrochus parma_, n. sp. + +Spongy framework of the disk in the inner part with five to eight spiral +convolutions (or partly concentric rings), in the outer part quite +irregular. Thirty to forty long, bristle-shaped, radial spines, about as +long as the diameter of the disk, disposed on both flat sides of the disk, +but not on the margin. + +_Dimensions._--Diameter of the disk 0.16; length of the radial spines 0.18, +basal breadth 0.003. + +_Habitat._--South Atlantic, Station 325, surface. + + + +Subfamily 3. SPONGOBRACHIDA, Haeckel, 1881, Prodromus, p. 461. + +_Definition._--#Spongodiscida# with two or more (commonly three or four) +spongy radial arms on the margin of the disk, situated in its equatorial +plane (with or without a connecting patagium between the arms). + + + +Genus 260. _Spongolena_,[299] n. gen. + +_Definition._--#Spongodiscida# with two opposite spongy arms on the margin +of the disk, without a connecting patagium. + +The genus _Spongolena_ opens the series of the Spongobrachida, or of the +Spongodiscida provided with radial spongy arms on the margin of the disk. +_Spongolena_ is the most simple form of this subfamily, and bears only two +simple opposite arms, without a connecting patagium. It corresponds to +_Amphibrachium_ (Porodiscida) and to _Diplactura_ (Coccodiscida). Also +there is no patagium. _Spongolena_ may easily be confounded with +_Spongurus_ (compare my Prodromus, 1881, p. 461); but in the true +_Spongurus_ (an ellipsoid) the transverse section is circular, in +_Spongolena_ elliptical. + + +1. _Spongolena rhopalura_, n. sp. + +Arms club-shaped, three times as long as broad, at the rounded distal end +twice as broad as at the base, and twice as long as the diameter of the +circular central disk. Surface nearly smooth. + +_Dimensions._--Radius of the arms (or the distance from the centre to the +distal arm-end) 0.16, distal breadth 0.05, basal breadth 0.03. + +_Habitat._--Pacific, central area, Station 273, depth 2350 fathoms. + + +2. _Spongolena spongura_, n. sp. + +Arms nearly cylindrical, twice as long as broad, and a little longer than +the diameter of the elliptical central disk. Surface thorny, some longer +bristle-shaped spines on the distal end of the {588}arms. (Very similar to +the ellipsoid _Spongurus cylindricus_, Monogr. d. Radiol., p. 465, Taf. +xxvii. fig. 1, but differs in the compressed lenticular (not ellipsoidal) +form of the central disk; the transverse section of the arm is elliptical, +not circular.) + +_Dimensions._--Radius of the arms 0.1, breadth 0.04. + +_Habitat._--Pacific, central area, Station 270, depth 2925 fathoms. + + +3. _Spongolena cypselura_, n. sp. + +Arms nearly triangular, not longer than broad, about half as large as the +elliptical central disk, at the broader distal end with two very large, +widely divergent lateral spines, and between them several smaller, like the +tail of a swallow. Surface thorny. + +_Dimensions._--Radius of the arms 0.2, distal breadth (without spines) +0.15, basal breadth 0.07. + +_Habitat._--Pacific, central area, Station 272, depth 2600 fathoms. + + + +Genus 261. _Spongobrachium_,[300] Haeckel, 1881, Prodromus, p. 461. + +_Definition._--#Spongodiscida# with two opposite spongy arms on the margin +of the disk, connected by a spongy patagium of different texture. + +The genus _Spongobrachium_ differs from the foregoing only in the loose +spongy patagium, which envelops both opposite spongy arms. It corresponds +to _Amphymenium_ among the Porodiscida and to _Amphiactura_ among the +Coccodiscida. + + +1. _Spongobrachium ellipticum_, Haeckel. + + _Spongocyclia elliptica_, Haeckel, 1862, Monogr. d. Radiol., p. 470, Taf. + xxviii. fig. 2. + + _Spongodiscus ellipticus_, Haeckel, 1860, Monatsber. d. k. preuss. Akad. + d. Wiss. Berlin, p. 844. + +Arms nearly square, scarcely as long and broad as the radius of the +circular central disk, at the broader distal end truncated. Patagium +complete, enveloping the whole disk with the arms, and forming a larger +elliptical disk of looser framework. (In my Monograph, 1862, _loc. cit._, I +had not distinguished the opposite darker arms, opposite in the longer axis +of the elliptical disk, from the enveloping looser framework of the +patagium. In larger specimens of the Challenger collection this distinction +is very evident.) + +_Dimensions._--Radius of the arms 0.12, breadth 0.05; major axis of the +elliptical patagium 0.24, minor 0.16. + +_Habitat._--Cosmopolitan; Mediterranean, Atlantic, Pacific, surface. + + +2. _Spongobrachium lanceolatum_, n. sp. + +Arms club-shaped, twice as long as broad, at the distal end pointed, five +times as long as the radius of the circular central disk. Patagium +complete, enveloping the whole disk with the arms, {589}and forming a +larger lanceolate disk of looser framework. (Similar in form to +_Amphymenium pupula_, Pl. 44, fig. 8, but with an irregular spongy +framework and pointed ends.) + +_Dimensions._--Radius of the arms 0.16, breadth 0.05; major axis of the +lanceolate patagium 0.32, minor axis 0.12. + +_Habitat._--Pacific, central area, Station 270, surface. + + + +Genus 262. _Rhopalodictyum_,[301] Ehrenberg, 1860, Monatsber. d. k. preuss. +Akad. d. Wiss. Berlin, p. 830. + +_Definition._--#Spongodiscida# with three spongy arms on the margin of the +circular or triangular disk, without a connecting patagium. + +The genus _Rhopalodictyum_ comprises those very common forms of +Spongodiscida in which the margin of the disk is provided with three +simple, free, spongy arms. It corresponds to _Dictyastrum_ and +_Rhopalastrum_ among the Porodiscida, to _Trigonactura_ among the +Coccodiscida. The typical species of this genus is _Rhopalodictyum +abyssorum_ of Ehrenberg, the only species figured by him. His diagnosis of +the genus was very insufficient, and agreed with that of his _Dictyastrum_ +(compare above the improved diagnosis of this genus, p. 526, and my +Monograph, p. 466). + + + +Subgenus 1. _Rhopalodictya_, Haeckel. + +_Definition._--Triangular shell regular, with three arms of equal size and +equidistant. + + +1. _Rhopalodictyum abyssorum_, Ehrenberg. + + _Rhopalodictyum abyssorum_, Ehrenberg, 1872, Abhandl. d. k. Akad. d. + Wiss. Berlin, p. 299, Taf. viii. fig. 17. + +Arms of equal size and equidistant, club-shaped, about as long as the +diameter of the triangular central disk, and a little longer than the +breadth of the pear-shaped rounded distal end. Surface rough. + +_Dimensions._--Radius of the arms 0.11, basal breadth 0.03, distal breadth +0.06. + +_Habitat._--Cosmopolitan; Atlantic, Indian, Pacific; tropical zone, +surface. + + +2. _Rhopalodictyum truncatum_, Ehrenberg. + + _Rhopalodictyum truncatum_, Ehrenberg, 1861, Monatsber. d. k. preuss. + Akad. d. Wiss. Berlin, p. 301. + + ? _Dictyastrum angulatum_, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. + Berlin, p. 289, Taf. viii. fig. 18. + +Arms of equal size and equidistant, nearly square, with straight edges, +towards the truncated end a little broader, about of the same diameter as +the central triangular disk. This species is indicated {590}by Ehrenberg +only by the short diagnosis, "Radiis stellae tribus apice truncatis." It is +probably identical with his figure of _Dictyastrum angulatum_ (_loc. +cit._). This latter name I have retained for the similar Porodiscid (above, +p. 526), mainly because the genera _Dictyastrum_ and _Rhopalodictyum_, +according to the insufficient diagnosis of Ehrenberg, seem to be identical. +(Compare my Monograph, 1862, p. 466.) + +_Dimensions._--Radius of each arm 0.13, basal breadth 0.09, distal breadth +0.1. + +_Habitat._--Tropical Pacific, Philippine Sea, Station 200, depth 250 +fathoms; Atlantic (Mexican Gulf Stream). + + +3. _Rhopalodictyum subacutum_, Ehrenberg. + + _Rhopalodictyum subacutum_, Ehrenberg, 1861, Monatsber. d. k. preuss. + Akad. d. Wiss. Berlin, p. 301. + +Arms of equal size and equidistant, club-shaped, three times as long as the +diameter of the central disk, which equals the breadth of the thickened +distal end; the latter is armed with a strong pyramidal terminal spine. +(The diagnosis of Ehrenberg is "Radiis stellae tribus, apice cuneatis +subacutis.") + +_Dimensions._--Radius of the arms 0.2, basal breadth 0.04, distal breadth +0.07. + +_Habitat._--North Atlantic, surface and various depths; Greenland; Mexican +Gulf Stream; Faeroee Channel (John Murray). + + +4. _Rhopalodictyum bifidum_, n. sp. + +Arms of equal size and equidistant, in the distal half forked, twice as +long as the diameter of the central disk; both fork branches half as broad +as the simple basal part, truncated at the distal end. + +_Dimensions._--Radius of the arms 0.16, basal breadth 0.08, distal breadth +0.04. + +_Habitat._--North Pacific, Station 237, surface. + + + +Subgenus 2. _Triactinosphaera_, Dunikowski, 1882, Denkschr. d. k. Akad. d. +Wiss. Wien, vol. 45, ii. p. 192. + +_Definition._--Triangular shell bilateral or irregular, with three arms of +different size or distance. + + +5. _Rhopalodictyum zittelii_, Haeckel. + + _Triactinosphaera zittelii_, Dunikowski, 1882, Denkschr. d. k. Akad. d. + Wiss, Wien, vol. 45, ii. p. 192. + +Arms of different size and at unequal distances, one odd arm being a little +shorter than the two paired arms; the odd angle between the latter is +larger than the paired angles between them and the {591}former. Arms +club-shaped, their basal semi-cylindrical, half as broad as the spherical +distal half, which bears a strong, conical, terminal spine. The discoverer +of this remarkable, very old, Liassic species, Dunikowski, supposes that it +is not a true Discoid, from the absence of a central disk; in my opinion +the central disk (nearly spherical) has the same relation to the arms as in +many other #Discoidea#, their equatorial plane is the same. + +_Dimensions._--Radius of the odd arm 0.18, of the paired arms 0.24; basal +breadth 0.08, distal breadth 0.16. + +_Habitat._--Fossil in the Alpine Lias, Schafberg, near Salzburg, +Dunikowski. + + +6. _Rhopalodictyum elongatum_, n. sp. + +Arms of different size and at unequal distances, one odd arm being twice as +long as both paired arms; the odd angle between the latter much larger than +both equal paired angles. Arms nearly cylindrical, little flattened, three +to six times as long as broad, with rounded blunt distal end. + +_Dimensions._--Radius of the arms 0.15 to 0.3, breadth 0.05. + +_Habitat._--Pacific, central area, Station 274, surface. + + +7. _Rhopalodictyum curvatum_, n. sp. + +Arms of different size and at unequal distances, irregular, more or less +curved, nearly cylindrical, five to ten times as long as broad, with +rounded blunt distal end. (There were observed only two specimens of this +remarkable irregular species; in one specimen all three arms were simple, +in the other one odd arm forked. The length of the arms and the size of the +angles between them seems to be very different and variable.) + +_Dimensions._--Radius of the arms 0.3 to 0.6 to 1.15, breadth 0.06 to 0.12. + +_Habitat._--Pacific, central area, Station 271, surface. + + + +Genus 263. _Dictyocoryne_,[302] Ehrenberg, 1860, Monatsber. d. k. preuss. +Akad. d. Wiss. Berlin, p. 830. + +_Definition._--#Spongodiscida# with three spongy arms on the margin of the +circular or triangular disk, connected by a spongy patagium of different +texture. + +The genus _Dictyocoryne_ differs from the foregoing _Rhopalodictyum_ only +in the patagium, connecting the three spongy arms, and bears to it the same +relation as in the Porodiscida _Euchitonia_ does to _Rhopalastrum_. The +typical species of this genus is _Dictyocoryne profunda_, the only species +figured by Ehrenberg. After his {592}insufficient diagnosis _Dictyocoryne_ +was identical with his _Spongaster_ (compare my Monograph, p. 467); but as +the type of this latter genus (_Spongaster tetras_) figured by him, 1872, +had four crossed arms, we retain this genus here separate. + + + +Subgenus 1. _Dictyocorynula_, Haeckel. + +_Definition._--Triangular shell regular, with three arms of equal size and +equal distance. + + +1. _Dictyocoryne profunda_, Ehrenberg. + + _Dictyocoryne profunda_, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. + Berlin, p. 307, Taf. vii. fig. 23. + +Arms of equal size and equidistant, club-shaped, in the outer circular half +three times as broad as in the inner cylindrical half, and much larger than +the small triangular central disk. Patagium complete, forming an +equilateral triangle with rounded corners. + +_Dimensions._--Radius of the arms 0.14, basal breadth 0.025, distal breadth +0.07. + +_Habitat._--Pacific, Philippine Sea, depth 3300 fathoms, Ehrenberg; Station +198, depth 2150 fathoms; Station 274, depth 2750 fathoms. + + +2. _Dictyocoryne tetradiscus_, n. sp. + +Arms of equal size and equidistant, club-shaped, their outer circular half +is quite as large as the circular central disk, and is connected with it by +the thin cylindrical inner half, which is scarcely one-fourth as broad. +Patagium complete, forming an equilateral triangle with rounded corners and +convex sides. + +_Dimensions._--Radius of the arms 0.16, basal breadth 0.02, distal breadth +0.08. + +_Habitat._--Pacific, central area, Stations 271 to 274, in 2350 to 2750 +fathoms. + + +3. _Dictyocoryne euchitonia_, Haeckel. + + _Dictyocoryne euchitonia_, Haeckel, 1862, Monogr. d. Radiol., p. 468. + +Arms of equal size and equidistant, lanceolate, twice as long as broad in +the distal part, and three times as long as the small circular central +disk. Patagium complete, forming an equilateral triangle with pointed +corners. (Very similar to _Euchitonia koellikeri_, Monograph, 1862, p. 511, +Taf. xxxi. fig. 6, but quite spongy, not concentric.) + +_Dimensions._--Radius of the arms 0.15, basal breadth 0.03, distal breadth +0.06. + +_Habitat._--Mediterranean (Messina), Haeckel. + + +{593}4. _Dictyocoryne trigona_, n. sp. + +Arms of equal size and equidistant, lanceolate, three times as long as +broad in the middle part, and as the diameter of the triangular central +disk; their distal end armed with a strong conical radial spine. Patagium +complete, forming an equilateral triangle with pointed corners. + +_Dimensions._--Radius of the arms 0.2, basal breadth 0.02, distal breadth +0.06. + +_Habitat._--North Atlantic, Canary Islands, surface. + + + +Subgenus 2. _Dictyocorynium_, Haeckel. + +_Definition._--Triangular shell bilateral or irregular, with three arms of +different sizes or at different distances. + + +5. _Dictyocoryne charybdaea_, Haeckel. + + _Spongocyclia charybdaea_, Haeckel, 1862, Monogr. d. Radiol., p. 472, + Taf. xxviii. figs. 5, 6. + + _Spongodiscus charybdaeus_, Haeckel, 1860, Monatsber. d. k. preuss. Akad. + d. Wiss. Berlin, p. 844. + +Arms at different distances, nearly equilateral triangular, scarcely half +as long as the radius of the large circular central disk. Both paired arms +touching at their bases, separated by a great distance from the opposite +odd arm. Patagium complete, nearly pentagonal. (The illustration in my +Monograph, in the coloured plate xxviii., is better than my description, as +I had not exactly separated the arms from the patagium.) + +_Dimensions._--Radius of the arms 0.18, basal breadth 0.08. + +_Habitat._--Mediterranean (Messina), surface. + + +6. _Dictyocoryne pentagona_, Stoehr. + + _Dictyocoryne pentagona_, Stoehr, 1880, Palaeontogr., vol. xxvi. p. 118, + Taf. vii. fig. 2. + +Arms at different distances, club-shaped, little longer than broad at their +rounded distal end. Both paired arms smaller and more approximate than the +opposite odd arm. Patagium complete, very large, enveloping the whole +shell, and forming a pentagon with rectilinear base and transverse +constriction, and with five rounded corners. + +_Dimensions._--Radius of the arms 0.1 to 0.15, middle breadth 0.04. + +_Habitat._--Fossil in the Tertiary rocks of Sicily, Grotte, Stoehr. + + +7. _Dictyocoryne agrigentina_, Stoehr. + + _Dictyocoryne agrigentina_, Stoehr, 1880, Palaeontogr., vol. xxvi. p. + 118, Taf. vii. fig. 1. + +Arms at different distances, club-shaped, about twice as long as broad, and +smaller than the large triangular central disk. Both paired arms smaller +and more approximate than the opposite odd {594}arm. Patagium incomplete, +enveloping only the basal half of the arms as a circular spongy disk of +loose framework. + +_Dimensions._--Radius of the arms 0.18, basal breadth 0.05, distal breadth +0.08. + +_Habitat._--Fossil in the Tertiary rocks of Sicily, Grotte, Stoehr. + + +8. _Dictyocoryne echinata_, n. sp. + +Arms unequal and at different distances, club-shaped, in the distal half +twice as broad as in the basal half, three times as long as the small +triangular central disk, at their distal end armed with one larger and +several smaller conical spines. Both paired arms with touching bases, and +only half as large as the doubly remote odd arm. Patagium incomplete, +enveloping only the basal half of the arms, and forming a circular disk of +looser framework. Surface thorny. + +_Dimensions._--Radius of the arms 0.15 to 0.2, basal breadth 0.03, distal +breadth 0.06. + +_Habitat._--South Atlantic, Station 325, surface. + + + +Genus 264. _Spongasteriscus_,[303] Haeckel, 1862, Monogr. d. Radiol., p. +474 (_sensu restricto_). + +_Definition._--SPONGODISCIDA with four spongy arms on the margin of the +circular or quadrangular disk, crossed in two equatorial diameters, without +a connecting patagium. + +The genus _Spongasteriscus_ (in the restricted definition here stated) +exhibits on the margin of the disk four spongy arms, which form either a +regular or a bilateral cross. It corresponds to _Stauralastrum_ and +_Myelastrum_ among the Porodiscida, to _Astractura_ among the Coccodiscida. + + + +Subgenus 1. _Spongasteriscinus_, Haeckel. + +_Definition._--Cross formed by the four arms regular, rectangular, with +equal-sized and equidistant arms. + + +1. _Spongasteriscus ovatus_, n. sp. + +Arms at equal distances, forming a regular, rectangular cross, egg-shaped, +with a broader rounded distal end, one and a third times as long as broad, +and three times as long as the radius of the central disk; in the latter +three to four concentric rings. + +_Dimensions._--Radius of the arms 0.1, greatest breadth 0.06. + +_Habitat._--Western Tropical Pacific, Station 225. + + +{595}2. _Spongasteriscus clavatus_, n. sp. + +Arms at equal distances, forming a regular, rectangular cross, club-shaped, +about as long as the diameter of the central disk, and at their rounded +distal end one and a third times as long as broad, at their narrow base +only one third as broad. In the centre five to six concentric rings. + +_Dimensions._--Radius of the arms 0.13, distal breadth 0.06, basal breadth +0.02. + +_Habitat._--Pacific, central area. Station 271, surface. + + +3. _Spongasteriscus mucronatus_, n. sp. + +Arms at equal distances, forming a regular, rectangular cross, club-shaped, +three times as long as the radius of the central disk, in the distal half +nearly circular, three to four times as broad as at the narrow base. The +rounded distal end armed with a strong pyramidal spine. In the centre no +concentric rings. (Similar to _Stauralastrum rhopalophorum_, Pl. 45, fig. +1, but quite spongy.) + +_Dimensions._--Radius of the arms 0.12, basal breadth 0.03, distal breadth +0.02. + +_Habitat._--Pacific, central area, Station 265, depth 2900 fathoms. + + +4. _Spongasteriscus furcatus_, n. sp. + +Arms at equal distances, forming a regular, rectangular cross, in the +distal third forked; both fork branches half as long as the basal undivided +part of the arm, which is twice as long as broad. Distal ends of the eight +branches blunt, rounded. In the central disk no concentric rings. + +_Dimensions._--Radius of the arms 0.12, basal breadth 0.03; distal breadth +of the branches 0.02. + +_Habitat._--North Pacific, Station 244, depth 2900 fathoms. + + +5. _Spongasteriscus armatus_, n. sp. + +Arms at equal distances, forming a rectangular, regular cross, in the +distal half forked; both fork branches of the same length as the basal +undivided part of the arm, which is nearly square. Distal ends of the eight +branches armed with a strong pyramidal spine. In the central disk no +concentric rings. (Similar to _Dicranastrum cornutum_, Pl. 45, fig. 2, but +quite spongy.) + +_Dimensions._--Radius of the arms 0.18, basal breadth 0.03, distal breadth +0.015. + +_Habitat._--South Pacific, Station 295, depth 1500 fathoms. + + + +Subgenus 2. _Spongasterisculus_, Haeckel. + +_Definition._--Cross formed by the four arms, bilateral or irregular, with +the arms at different distances. + + +{596}6. _Spongasteriscus quadricornis_, Haeckel. + + _Spongasteriscus quadricornis_, Haeckel, 1862, Monogr. d. Radiol., p. + 474, Taf. xxviii. figs. 8-10. + + _Spongodiscus quadricornis_, Haeckel, 1860, Monatsber. d. k. preuss. + Akad. d. Wiss. Berlin, p. 844. + +Arms at different distances, forming a bilateral or irregular cross, +grouped in two opposite pairs; their form equilateral triangular; their +length smaller than the radius of the large circular central disk, which +exhibits in the interior eight to sixteen concentric rings. + +_Dimensions._--Radius of the arms 0.2, of the central disk 0.13; basal +breadth of the arms 0.08. + +_Habitat._--Mediterranean (Messina), Haeckel, surface. + + +7. _Spongasteriscus tetraceros_, Haeckel. + + _Spongasteriscus tetraceros_, Haeckel, 1862, Monogr. d. Radiol., p. 475. + +Arms at different distances, forming a bilateral or irregular cross, +grouped in two opposite pairs; their form isosceles triangular; their +length larger than the radius of the large elliptical central disk, which +exhibits in the interior six to twelve concentric rings. + +_Dimensions._--Radius of the arms 0.16, of the central disk 0.1; basal +breadth of the arms 0.06. + +_Habitat._--Mediterranean (Messina), North Atlantic (Canary Islands), +surface. + + +8. _Spongasteriscus myelastrum_, n. sp. + +Arms at different distances, forming a bilateral or irregular cross, +grouped in two opposite pairs; the arms of one pair broader and shorter +than the arms of the other pair. Each arm in its basal half simple, in the +distal half forked; ends of the fork branches blunt. In the central disk no +concentric rings. (Similar to _Myelastrum octocorne_, Pl. 47, fig. 12, but +quite spongy.) + +_Dimensions._--Radius of the arms 0.2, basal breadth 0.05, distal breadth +0.02. + +_Habitat._--North Pacific, Station 236, surface. + + + +Genus 265. _Spongaster_,[304] Ehrenberg, 1860, Monatsber. d. k. preuss. +Akad. d. Wiss. Berlin, p. 833. + +_Definition._--#Spongodiscida# with four spongy arms on the margin of the +circular or quadrangular disk, connected by a spongy patagium of different +texture. + +The genus _Spongaster_ differs from the foregoing _Spongasteriscus_ in the +patagium connecting the spongy arms, and bears therefore to it the same +relation as, in the Porodiscida, _Histiastrum_ does to _Stauralastrum_, or, +in the Coccodiscida, _Stauractura_ does to _Astractura_. The typical +specimen, figured by Ehrenberg (_Spongaster tetras_), exhibits a regular, +square disk, as also some other species. In a certain number of other +species (formerly united by me with _Spongocyclia_) the quadrangular disk +is bilateral. + + + +{597}Subgenus 1. _Spongastrella_, Haeckel. + +_Definition._--Cross formed by the four arms regular, rectangular, with the +arms of equal size and equidistant. + + +1. _Spongaster tetras_, Ehrenberg. + + _Spongaster tetras_, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. + Berlin, p. 299, Taf. vi. (iii.) fig. 8. + + _Dictyocoryne tetras_, Haeckel, 1862, Monogr. d. Radiol., p. 469. + +Arms at equal distances, forming a rectangular, regular Myelastrum, +papiliocross, club-shaped, about twice as long as the diameter of the +square central disk and eight times as long as broad at their base. Distal +ends rounded, perfectly enclosed by the complete patagium, which forms a +regular square, with slightly concave sides. + +_Dimensions._--Radius of the arms 0.12, distal breadth 0.03, basal breadth +0.015; length of the square side 0.2. + +_Habitat._--Cosmopolitan; Atlantic, Indian, Pacific, surface and in various +depths. + + +2. _Spongaster quadratus_, n. sp. + +Arms at equal distances, forming a regular, rectangular cross, club-shaped, +about four times as long as the diameter of the central circular disk, and +five times as long as broad at the base. Basal third of the arms square; +distal two thirds triangular, three times as broad, with a truncated distal +end. Patagium complete, perfectly enveloping the arms, and bordered by an +elegant, radially striated, broad edge, forming a regular square. (Similar +to _Histiastrum quadratum_, Pl. 46, fig. 4, but quite spongy.) + +_Dimensions._--Radius of the arms 0.15, distal breadth 0.06, basal breadth +0.02; length of the square side 0.25. + +_Habitat._--Pacific, central area, Stations 270 to 274, depths 2350 to 2925 +fathoms. + + +3. _Spongaster cruciatus_, n. sp. + +Arms at equal distances, forming a rectangular, regular cross, lanceolate, +three times as long as broad and as the diameter of the central circular +disk. Ends of the arms provided with a short conical spine. Patagium +incomplete, enveloping only the basal half of the arms, forming a regular +square with concave sides. + +_Dimensions._--Radius of the arms 0.18, greatest breadth 0.05; length of +the square side 0.2. + +_Habitat._--South Pacific, Station 288, surface. + + +{598}4. _Spongaster pentacyclus_, n. sp. + +Arms at equal distances, forming a rectangular, regular cross, of the same +size and form as the circular central disk, so that the dark interior part +of the shell is composed of five equal circular disks, situated in a +quincuncial manner. The clearer complete patagium, enveloping the whole +cross perfectly, forms a regular square with rounded edges. + +_Dimensions._--Radius of the arms 0.2; diameter of each of the five +circular disks 0.01; length of the square side 0.35. + +_Habitat._--West Indies, Cuba, surface (Thomson). + + + +Subgenus 2. _Spongastromma_, Haeckel. + +_Definition._--Cross formed by the four arms bilateral or irregular, with +the arms at different distances. + + +5. _Spongaster orthogonus_, Haeckel. + + _Spongocyclia orthogona_, Haeckel, 1862, Monogr. d. Radiol., p. 471, Taf. + xxviii. fig. 3. + + _Spongodiscus orthogonus_, Haeckel, 1860, Monatsber. d. k. preuss. Akad. + d. Wiss. Berlin, p. 844. + +Arms at different distances, forming a bilateral cross, grouped in two +opposite pairs of equal size and similar form. Arms club-shaped, about as +long as the diameter of the central circular disk, enveloped perfectly by +the complete patagium, which forms a regular rectangle, the longer side of +which is one and a half times as long as the shorter side. (The arms in my +figure are not distinctly enough marked.) + +_Dimensions._--Radius of the arms 0.08, breadth 0.02; length of the larger +side of the rectangle 0.15, of the smaller 0.1. + +_Habitat._--Mediterranean (Messina), surface. + + +6. _Spongaster scyllaeus_, Haeckel. + + _Spongocyclia scyllaea_, Haeckel, 1862, Monogr. d. Radiol., p. 471, Taf. + xxviii. fig. 4. + + _Spongodiscus scyllaeus_, Haeckel, 1860, Monatsber. d. k. preuss. Akad. + d. Wiss. Berlin, p. 844. + +Arms at different distances, forming a bilateral cross, grouped in two +opposite pairs of different size and form, one pair smaller and less +divergent than the other. Arms club-shaped, little longer than the radius +of the central circular disk, enveloped perfectly by the complete patagium, +which forms a trapezium; the convergent longer sides of the latter are one +and a half times as long as the larger, and twice as long as the smaller +parallel side. (The arms are in my figure, _loc. cit._, not distinctly +enough marked.) + +_Dimensions._--Radius of the arms 0.12 to 0.14, breadth 0.02; length of +both convergent sides 0.24, of the larger parallel side 0.18, of the +smaller 0.12. + +_Habitat._--Pacific, central area, Station 272, surface; Mediterranean +(Messina). + + +{599}---- + + +Suborder VI. LARCOIDEA, Haeckel, 1883 (Pls. 9, 10, 49, 50). + +_Definition_.--SPUMELLARIA with lentelliptical central capsule (rarely +somewhat modified or allomorphic), with a lentelliptical fenestrated +siliceous shell (often modified or allomorphic, and sometimes quite +irregular). Growth different in the three unequal dimensive axes, +perpendicular one to another. The typical Lentellipsis is characterised by +three elliptical dimensive planes of different sizes, perpendicular one to +another. + +The section #Larcoidea#, the fourth and last of the #Sphaerellaria#, +comprises all those forms of this group in which the fenestrated shell +originally is lentelliptical, characterised by different growth in three +different axes, perpendicular one to another, all three equal on both +poles. The geometrical fundamental form of the shell is therefore a +lentellipsis or a triaxial ellipsoid; and this typical form is preserved +completely in the majority of #Larcoidea# in the pure geometrical form of +the central capsule. + +The three dimensive axes, which determine the typical form of #Larcoidea#, +are commonly differentiated in such a way, that the first, the longitudinal +or principal axis, is the longest; both its poles, oral and aboral (or +anterior and posterior) are equal. The second, the lateral or transverse +axis, is commonly less than the first, greater than the third axis; both +its poles are the equal lateral poles (right and left not differentiated). +The third dimensive axis, the equatorial or sagittal axis, is commonly the +shortest; both its equal poles are the sagittal poles (dorsal and ventral +poles not different). The relative size of the three dimensive axes in the +human body exhibits similar relations. + +The three dimensive planes of the #Larcoidea#, the sagittal, lateral, and +transverse planes, are elliptical, all three of different sizes. The first +plane, the median or sagittal plane, is commonly as regards size between +the two others; its major axis is the principal, its minor the sagittal +axis; it separates the right half of the body from the left. The second +plane or lateral plane, is commonly larger than the two others; its major +axis the principal, its minor the transverse axis; it separates the dorsal +half of the body from the ventral. The third plane, the equatorial or zonal +plane, is commonly less than the two others; its major axis the lateral, +its minor the sagittal axis; it separates the two principal halves of the +body, the oral and aboral halves. + +In my Monograph (1862) only very few forms of #Larcoidea# are described, +_Tetrapyle_ and _Lithelius_ (the latter representing a peculiar family, +Lithelida). In my Prodromus (1881, pp. 463, 464) I disposed all observed +forms of #Larcoidea# in two different families, the Pylonida and Lithelida. +The rich materials of the Challenger collection have since offered an +astonishing number of new and interesting forms of this section, so that I +can enumerate here fifty-one genera and two hundred and sixty-five species. +I dispose them here in four subsections and nine families. Three of these +have regular lentelliptical shells, which are not articulate, and +{600}without annular constrictions (Larcarida, Larnacida, Pylonida); these +form the subsection Pylolarcida. Two other families (Tholonida and +Zonarida) are distinguished by annular constrictions, which divide the +regular lentelliptical shell into a number of dome-shaped chambers or +cupolas; we call these Thololarcida. A third group, Spirolarcida, comprises +the #Larcoidea# with spiral growth; the two families of Lithelida and +Streblemida. Finally a fourth group the Sorolarcida is formed by the +#Larcoidea# with irregular shells, also two families, the Phorticida and +Soreumida. + +The first family of #Larcoidea#, the Larcarida, contains the most simple +forms, beginning with _Cenolarcus_, a quite simple lentelliptical latticed +shell. In _Coccolarcus_ we find already two concentric shells, connected by +radial beams, an inner medullary and an outer cortical shell. In +_Spongolarcus_ the lentelliptical shell becomes spongy. + +The second family, Larnacida, is very similar to the Larcarida, and seems +to diverge only by the different mode of connection between the two +concentric lentelliptical shells. But in truth this slight difference is of +great morphological importance, as it depends on a quite different and +peculiar mode of growth. In the foregoing Larcarida (_Coccolarcus_, &c.), +the concentric shells originate in the same manner as in the concentric +#Prunoidea# and #Sphaeroidea#, by radial beams, which arise from the +surface of the inner (medullary) shell and become connected by a network to +form the outer (cortical) shell. Here, in the Larnacida, a quite similar +shell originates in a quite different way, first arrived at in the Pylonida +(_Trizonium_). Both concentric shells become here connected by peculiar +lattice girdles, which are developed in the perimeter of the three +elliptical dimensive planes. Firstly, on both sides of a simple, spherical, +or lentelliptical central chamber, arise two lateral wings (on the poles of +the transverse axis), and build around the former a transverse girdle. This +is crossed by a larger lateral girdle, the minor axis of which is the major +of the former, and perpendicular to both girdles is yet developed a third, +the sagittal girdle. If the open fissures or "gates" between these three +girdles become closed by network, we obtain _Larnacilla_, the probable +ancestral form of all Larnacida. + +Whilst in _Larnacilla_ and _Larnacidium_ this typical trizonal +lentelliptical shell constitutes by itself alone the whole skeleton, in the +other Larnacida it becomes overgrown by outer envelops, and so becomes +enclosed in the interior of the central capsule as a "_Larnacilla_-shaped +medullary shell." If the enclosing external envelops be simply latticed, we +get the subfamily Larnacalpida; if they be spongy, we get the +Larnacospongida. + +The third family, Pylonida, is the most important of all #Larcoidea#, as +not only the largest and most interesting number of species belong to it, +but also many other genera (far the greater part of all #Larcoidea#) may be +derived from it. The peculiar character of the Pylonida is determined by +the imperfect fenestration of the lentelliptical shell growing in the three +dimensive axes in a quite different manner. Each elliptical dimensive plane +becomes circumscribed by an elliptical latticed girdle (or fenestrated +{601}ring), and between these three girdles (perpendicular one to another) +remain wide open fissures of the shell or "gates" (_Pylae_). The beginning +of the shell-building is the same as in _Larnacilla_, the most simple form +of Larnacida. From a quite simple medullary shell, a spherical, +subspherical, ellipsoidal, or lentelliptical central chamber, arise two +latticed wings, opposite on the poles of the transverse axis +(_Monozonium_). Both wings are short and wide hollow fenestrated tubes, the +axes of which are parallel to the principal axis. Therefore they form +together with the central chamber an elliptical transverse girdle. This +first girdle becomes crossed by a second lateral girdle; from both poles of +the transverse axis arise latticed wings, which unite on the poles of the +principal axis, therefore the minor axis of this second larger ring is the +major axis of the first smaller ring (_Dizonium_). Between the two crossed +rings remain four wide open gates. Now follows the development of a third +sagittal girdle, arising from both poles of the principal axis and +overgrowing the four gates. But as this third girdle is larger than the +second, four other larger gates arise between the two (in planes +perpendicular to the former four gates). Now we have the characteristic and +most important trizonal shell (_Trizonium_), composed of three elliptical +lattice-girdles of different size, perpendicular one to another, and +enclosing a simple central chamber. If the four gates of this _Trizonium_ +become closed by lattice-work, it passes over into _Larnacilla_, the most +important ancestral form of the Larnacida. + +This most significant "trizonal shell," either incompletely latticed in +_Trizonium_ (with four open gates), or completely latticed by fenestration +of the four gates, in _Larnacilla_, is to be found in far the greater part +of all #Larcoidea#, representing the medullary shell, which is overgrown by +an outer cortical shell. In many #Larcoidea#, in which this +"_Larnacilla_-shell" is absent, it is perhaps lost by phylogenetic +reduction, or retrograde metamorphosis. + +The same process of triple girdle-building, by which the typical +_Trizonium_-shell or _Larnacilla_-shell is produced (Haplozonaria), is +repeated once or twice in the larger forms of Pylonida. The first system of +three girdles (perpendicular one to another) becomes overgrown by a second +system of the same formulation in the Diplozonaria, and this becomes +overgrown by a third system in the Triplozonaria; in the highest genus of +this group, _Pylozonium_, we find not less than nine girdles (three +systems, each of three girdles). Till now only one genus of the whole +polymorphous family was well known, _Tetrapyle_ (with five girdles, three +of the medullary, two of the cortical shell). If the gates between the +girdles remain open, all these forms must be regarded as Pylonida; if the +gates afterwards become closed by a network, they pass over into other +families. + +The fourth family of the _Larcoidea_ is the Tholonida, distinguished by the +polythalamous shell being composed of a certain number of roundish or +hemispherical chambers (domes or cupolas), which surround a primordial +central chamber in quite regular disposition, lying opposite in pairs on +the poles of the three dimensive axes. {602}If we imagine that each "wing" +(or open half-girdle) of the Pylonida becomes closed by a lattice-work, and +so transformed into a hemispherical or roundish cupola, we obtain the +characteristic shell of the Tholonida. Indeed every girdle of the former +corresponds to a pair of opposite domes of the latter. The axis of each +pair of domes is one of the three dimensive axes. + +The primordial chamber of the Tholonida (or the central chamber, around +which all cupolas are regularly disposed) is either a simple lentelliptical +lattice-shell, like _Cenolarcus_, or it is a trizonal shell (with an +enclosed concentric medullary shell), like _Larnacilla_. As in both cases +the building and the disposition of the cupolas around it are quite the +same, we can suppose that the whole family of Tholonida may have been +derived originally from _Larnacilla_ (or _Trizonium_), and that the +Cenotholida (with a simple central chamber) are sprung from the +Coccotholida (with a _Larnacilla_-shaped central chamber) by reduction and +loss of the original medullary shell. + +The family Tholonida can be divided into three subfamilies according to the +disposition of the cupola-pairs in one, two, or three dimensive axes. In +the Cubotholida lie two cupolas on the poles of the transverse axis of the +central chamber (corresponding to _Amphipyle_); in the Staurotholida we +find four cupolas crosswise disposed, on the poles of the transverse and +principal axes (corresponding to _Tetrapyle_); in the Cubotholida are at +least six cupolas, on the poles of all three dimensive axes (corresponding +to _Tholonium_). In all three cases the number of cupolas may be augmented +by the secondary apposition of other chambers or domes in the same +disposition. Sometimes also the whole cortical shell becomes enclosed by an +external veil or mantle of delicate network. The lentelliptical (or often +nearly cubical) central chamber becomes often reduced, so that its sides +are incompletely latticed or widely opened; in some Cubotholida only the +twelve edges of the eight cornered cubical central chamber remain; its six +sides are quite open and only over-vaulted by the six hemispherical +cupolas. From the opposite points of the latter (in the deep annular +constrictions between them) often arise radial spines, and these lie +commonly in diagonal planes, separating the dome-pairs. + +A similar dome-building or a composition of the polythalamous shell by +pairs of cupolas we find also in the next (fifth) family, the Zonarida. But +here the true cause of the peculiar dome-structure is quite different, not +an apposition of new chambers, but the constriction of a cortical +shell-like _Larnacalpis_ by two or more constrictions. These constrictions +lie in dimensive planes (or in planes parallel to these), and therefore the +cupolas are (all or partly) in diagonal planes, a condition quite opposite +to that found in the Tholonida. One of the annular constrictions is +constantly in the sagittal plane (separating the right and left halves of +the shell). The number of the constrictions in the few genera is two, +three, and four, and therefore the number of the cupolas four, six, or +eight. As this cortical shell constantly encloses a trizonal medullary +shell (or _Larnacilla_-shell), we cannot doubt that the Zonarida must be +derived from the Larnacida. + +{603}Whilst in all the foregoing five families of #Larcoidea# the +shell-form is regular and their geometrical fundamental form is a +lentellipsis (or a triaxial ellipsoid, with three unequal isopolar +dimensive axes), in the four remaining families of this suborder the shell +becomes bilateral or irregular (with the poles of the axes unequal). In two +of these families (Lithelida and Streblemida) the growth of the shell +becomes spiral, in the last two families (Soreumida and Phorticida) quite +irregular. But as in all four families we encounter the typical trizonal +medullary shell (or _Larnacilla_-shell), we are convinced that they must be +derived (wholly or partially) from the Larnacida. + +The Lithelida (the sixth family) are #Larcoidea# with spiral growth and +bilateral form (like _Nautilus_); therefore the spiral line lies in one +plane and this spiral plane divides the whole shell into two symmetrical +halves (right and left). The axis of the spiral (around which the shell +winds) is a straight line, one of the three dimensive axes. In the greater +part of Lithelida (in the Larcospirida) the primordial of central chamber +of the polythalamous shell is a trizonal medullary shell or +_Larnacilla_-shell, and the growth of the first spiral turning begins as +the development of the first (transverse) cortical girdle of _Amphipyle_; +but as one wing (or lateral half) of this girdle grows more rapidly than +the other, it overgrows the latter and begins the spiral winding; if the +other wing follow and overgrow the first, the spiral becomes double. Each +of the three dimensive girdles (of the Pylonida) may begin the spiral +winding. There can be no doubt that all these Lithelida (the Larcospirida) +must be derived from the Pylonida, by unequal growth of the two halves of +one girdle. Perhaps from these may also derived the other part of this +family, the Spiremida (_Spirema_ and _Lithelius_); in these the primordial +chamber of the spiral shell is simple, and may be derived by reduction of +the original _Larnacilla_-shell. But it is also possible that the Spiremida +proceed directly from the Larcarida, and that their ancestors did not +possess a _Larnacilla_-shell. + +The Streblemida (the seventh family) are #Larcoidea# with spiral growth and +asymmetrical form of the polythalamous shell (like _Helix_ or +_Turrilites_); therefore the spiral line is twisted like a winding stair, +and the spiral face is curved and divides the shell into two unequal +halves. The Streblemida have the same likeness and relation to the +turbinoid Foraminifera (_Rotalia_, _Globigerina_, &c.) as the Lithelida to +the nautiloid Foraminifera (_Polystomella_, _Nummulina_, &c.). As in these +calcareous Rhizopods also the peculiar growth of the siliceous Streblemida +begins from a primordial chamber to which a variable number of roundish +chambers (of increasing size) is apposed. But the building of these +chambers and of their septa is by no means so regular and complete as in +the greater number of turbinoid Foraminifera. As in a part of this family +the primordial chamber is _Larnacilla_-shell, these also may be derived +from the Larnacida, but the other part (with simple central chamber) is +perhaps produced directly from the Larcarida. + +The eighth family, Soreumida, is perhaps derived from the Streblemida by +the loss of the spiral growth. The polythalamous shell is similar to the +latter, but the chambers are {604}aggregated without any order, like the +Acervulinida among the Foraminifera. In some cases also here the primordial +chamber is a trizonal _Larnacilla_-shell, in other cases it is a simple, +subspherical or lentelliptical shell. + +The last family, the Phorticida, is formed of irregular #Larcoidea#, in +which a lentelliptical trizonal _Larnacilla_-shell (as an inner medullary +shell) is enveloped by an irregular, latticed, or spongy cortical shell. +They can be regarded as abnormalities or irregular deformities of Larnacida +or Pylonida. + +The central capsule of the #Larcoidea# is originally lentelliptical and +preserves this form, the "triaxial ellipsoid," in the greater number of +genera. In some groups it follows the prevalent growth of the shell in the +direction of one of the three dimensive axes, and becomes prolonged in this +way. In many chambered forms (particularly Tholonida and Zonarida) the +growing central capsule gets constricted, corresponding to the +constrictions of the shell. In the Soreumida and Phorticida its form often +becomes irregular. But in general for the greater number of #Larcoidea# the +lentelliptical form of their central capsule is quite characteristic. + +_Synopsis of the Families of_ #Larcoidea#. + + ------------------------------------------------------------------------- + #Larcoidea# with a regular or symmetrical shell, the growth of which is + determined by the three dimensive axes. (Both poles of each axis are + equal.) + ------------------------------------------------------------------------- + {Medullary shell absent or + Cortical shell completely { simple (spherical or + latticed, without external { lentelliptical), 1. LARCARIDA. + gates (or interzonal { + fissures), without annular {Medullary shell trizonal or + constrictions and domes. { _Larnacilla_-shaped + { (composed of three + { dimensive girdles), 2. LARNACIDA. + + Cortical shell incompletely latticed, with two to four or + more symmetrically disposed gates or fissures remaining + between latticed dimensive girdles, 3. PYLONIDA. + + Cortical shell completely }Constrictions of the + latticed, without external } cortical shell in + gates (or interzonal } diagonal planes; domes + fissures), with two or } in dimensive axes, 4. THOLONIDA. + more annular constrictions,} + which separate three to }Constrictions of the + six or more dome-shaped } cortical shell in + protuberances. } dimensive planes; domes + } in diagonal axes, 5. ZONARIDA. + ------------------------------------------------------------------------- + #Larcoidea# with a symmetrical or irregular shell, either with + spiral growth or with quite irregular growth. (Both poles of one axis + are different.) + ------------------------------------------------------------------------- + {Spiral cortical shell bilateral + { (with plane spiral), 6. LITHELIDA. + Cortical shell with { + spiral growth. {Spiral cortical shell + { asymmetrical (with ascending + { spiral), 7. STREBLEMIDA. + + {Cortical shell simple, with + { one single chamber, 8. PHORTICIDA. + Cortical shell with quite { + irregular growth. {Cortical shell composed of + { a number of heaped up + { or aggregated chambers, 9. SOREUMIDA. + + + +{605}Family XXIV. #LARCARIDA#, Haeckel, 1883 (Pl. 50, figs. 1, 2). + +_Definition._--#Larcoidea# with a regular, completely latticed, +lentelliptical cortical shell, without open gates and annular +constrictions; medullary shell absent or simple (not trizonal), connected +with the cortical shell by radial beams. + +The family #Larcarida# opens the long series of #Larcoidea# as the most +simple group of this suborder. It commences with _Cenolarcus_, a quite +simple lentelliptical latticed shell, which is characterised by three +unequal isopolar dimensive axes, perpendicular one to another. The major of +these three axes is the longitudinal or principal, the middle is the +lateral or transverse, and the minor is the equatorial or sagittal axis (as +in the human body). Among the three dimensive planes, which are determined +by pairs of these axes, the lateral plane is the largest (halved by the +crossed principal and lateral axes). The intermediate is the sagittal plane +or median plane (halved by the crossed principal and sagittal axes). The +smallest is the equatorial plane or transverse plane (halved by the crossed +lateral and sagittal axes). Therefore the shell has all the characters of +the true _Lentellipsis_ or of the "triaxial ellipsoid," and its axes agree +with the three axes of the "rhombic crystalline system." + +In the three subfamilies of Larcarida this lentelliptical shell assumes a +different shape: in the Cenolarcida it remains simple, in the Spongolarcida +it becomes spongy (sometimes quite filled out with a spongy framework), in +the Coccolarcida it is composed of two or more concentric lentelliptical +shells (at least an inner medullary and one outer cortical shell). These +shells are simply connected by radial beams, and not, as in the Larnacida, +by latticed wings (or half girdles). + +The network of the Larcarida shell is sometimes regular, commonly irregular +(as in the greater number of #Larcoidea#). The surface of the shell is +sometimes smooth or thorny, at other times covered with radial spines. +These are often symmetrically disposed, either on the poles of the +dimensive axes or in crossed diagonal planes. + +The central capsule is a true "lentellipsis" in a geometrical sense; it is +halved by three elliptical dimensive planes of different sizes, +perpendicular one to another. In the Cenolarcida the central capsule lies +freely inside the simple (cortical) shell, only separated from it by the +jelly-mantle. In the Coccolarcida it contains the medullary shell, and is +enclosed by the simple or double cortical shell, perforated by the radial +beams connecting the two shells. The spongy shell of the Spongolarcida +exhibits a different relation to the central capsule: in _Spongolarcus_ the +latter lies freely in the internal cavity of the spongy shell; in +_Stypolarcus_, where this cavity is quite filled with a spongy network, the +central capsule also contains a part of it. + +The morphological and phylogenetic relations of the Larcarida to the other +families of SPUMELLARIA admit of a different explanation. As this family +contains the {606}most simple forms of all #Larcoidea#, we can regard the +_Cenolarcus_ as the common ancestral form of this group, having originated +from _Actilarcus_ (or the lentelliptical _Actissa_) by the building of a +simple lentelliptical lattice-shell. But it is also possible that a part of +the Larcarida (or all?) descend from Larnacida by reduction or loss of the +original _Larnacilla_-shell (compare _Cenolarcus triaxonius_, p. 607). + +_Synopsis of the Genera of the Larcarida._ + + ------------------------------------------------------------------------- + I. Subfamily Cenolarcida. + Shell simple, latticed (lentelliptical cortical shell). + ------------------------------------------------------------------------- + Without radial spines, 266. _Cenolarcus_. + + With radial spines, 267. _Larcarium_. + ------------------------------------------------------------------------- + II. Subfamily Coccolarcida. + Shell composed of two or more concentric latticed shells (inner + medullary and outer cortical). + ------------------------------------------------------------------------- + Without radial spines, 268. _Coccolarcus_. + + With radial spines, 269. _Larcidium_. + ------------------------------------------------------------------------- + III. Subfamily Spongolarcida. + Shell spongy, partly or whole composed of a spongy framework. + ------------------------------------------------------------------------- + With an internal cavity, 270. _Spongolarcus_. + + Without an internal cavity, 271. _Stypolarcus_. + + + +Subfamily 1. CENOLARCIDA, Haeckel. + +_Definition._--#Larcarida# with a simple, lentelliptical latticed shell +(cortical shell without a medullary shell). + + + +Genus 266. _Cenolarcus_,[305] n. gen. + +_Definition._--#Larcarida# with a simple, lentelliptical latticed shell, +without a medullary shell, without radial spines. + +The genus _Cenolarcus_ begins the group of #Larcoidea# as the most simple +form of this suborder. It corresponds to _Cenosphaera_ among the +#Sphaeroidea#, to _Cenodiscus_ among the #Discoidea#, to _Cenellipsis_ +among the #Prunoidea#. The simple latticed shell is distinguished from that +of the three other genera by its typical lentelliptical form, a triaxial +ellipsoid with three dimensive axes of unequal length. Probably +_Cenolarcus_ is the original ancestral form of the #Larcoidea#, derived +from _Actilarcus_ (the lentelliptical _Actissa_) by the formation of a +simple fenestrated shell around the lentelliptical central capsule. But +possibly also some species of _Cenolarcus_ may be derived from +_Coccolarcus_ or _Larnacilla_ by reduction and loss of the medullary shell +(compare _Cenolarcus triaxonius_, n. sp.). + + +{607}1. _Cenolarcus primordialis_, n. sp. (Pl. 50, figs. 7, 7_a_, 7_b_). + +Network of the shell regular, with circular, hexagonally framed pores, +twice as broad as the elevated bars; about ten pores on the half meridian, +eight on the half equator. Surface a little rough. Proportion of the three +dimensive axes = 2 : 2.5 : 3. + +_Dimensions._--Principal axis (or length) 0.12, transverse axis (or +breadth) 0.1, sagittal axis (or thickness) 0.08; pores 0.01, bars 0.005. + +_Habitat._--Pacific, central area, Station 271, depth 2425 fathoms. + + +2. _Cenolarcus dimensivus_, n. sp. + +Network of the shell regular, with circular pores (without hexagonal +frames), three times as broad as the thin bars; about twelve pores on the +half meridian, nine on the half equator. Surface thorny. Proportion of the +three dimensive axes = 3 : 4 : 5. + +_Dimensions._--Principal axis 0.15, transverse axis 0.12, sagittal axis +0.09; pores 0.012, bars 0.004. + +_Habitat._--North Pacific, Station 244, surface. + + +3. _Cenolarcus triaxonius_, n. sp. + +Network of the shell regular, with circular, hexagonally framed pores, four +times as broad as the thin bars; about twelve pores on the half meridian, +nine on the equator. Surface smooth. From the inner surface of the shell +arise six very thin radial beams, opposite in pairs in the three dimensive +axes; all six beams end freely in a little knob, at an equal distance from +the centre; therefore this remarkable species seems to have lost a +medullary shell (descending from _Coccolarcus_ or _Larnacilla_?). +Proportion of the three dimensive axes = 2 : 2.5 : 3. + +_Dimensions._--Principal axis 0.13, transverse axis 0.11, sagittal axis +0.09; pores 0.012, bars 0.03. + +_Habitat._--Tropical Atlantic, Station 338, depth 1990 fathoms. + + +4. _Cenolarcus lentellipticus_, n. sp. + +Network of the shell regular, with circular pores of the same breadth as +the thick bars; about eighteen pores on the half meridian, fourteen on the +half equator. Surface smooth. Proportion of the three dimensive axes = +2 : 3 : 4. + +_Dimensions._--Principal axis 0.16, transverse axis 0.12, sagittal axis +0.08; pores and bars 0.004. + +_Habitat._--Western Tropical Pacific, Station 224, surface. + + +5. _Cenolarcus minimus_, n. sp. + +Network of the shell subregular, with very small circular pores of the same +breadth as the bars; only four pores on the half meridian, three on the +half equator. Surface smooth. Proportion of the three dimensive axes = +3 : 4 : 5. + +{608}_Dimensions._--Principal axis 0.05, transverse 0.04, sagittal axis +0.03; pores and bars 0.006. + +_Habitat._--Pacific, central area, Station 266, depth 2750 fathoms. + + + +Genus 267. _Larcarium_,[306] n. gen. + +_Definition._--#Larcarida# with a simple, lentelliptical latticed shell, +without a medullary shell; surface covered with radial spines. + +The genus _Larcarium_ differs from _Cenolarcus_ only in the possession of +radial spines on the surface of the simple fenestrated lentelliptical +shell. These spines are commonly disposed symmetrically, opposite in pairs, +either on the poles of the three dimensive axes, or on the poles of certain +diagonal axes. Larcarium differs from the similar genera _Larcidium_, +_Larnacidium_, and _Larnacantha_ by the absence of any medullary shell. + + +1. _Larcarium amphistylum_, n. sp. + +Shell thorny, with two large conical spines, opposite on both poles of the +principal axis, somewhat longer than it. Network of the shell regular, with +circular, hexagonally framed pores, twice as broad as the bars; about +twelve pores on the half meridian, ten on the half equator. Proportion of +the three dimensive axes = 3 : 4 : 5. + +_Dimensions._--Principal axis (or length) 0.15, transverse axis (or +breadth) 0.12, sagittal axis (or thickness) 0.09; pores 0.01, bars 0.005. + +_Habitat._--Pacific, central area, Station 274, depth 2750 fathoms. + + +2. _Larcarium staurostylum_, n. sp. + +Shell smooth, with four short three-sided pyramidal spines of equal length, +opposite in pairs on the poles of the principal and lateral axes. Network +of the shell regular, with circular pores of the same breadth as the bars; +about eight pores on the half meridian, six on the half equator. Proportion +of the three dimensive axes = 2 : 2.5 : 3. + +_Dimensions._--Length of the shell 0.12, breadth 0.1, thickness 0.08; pores +and bars 0.006. + +_Habitat._--South Pacific, Station 300, depth 1375 fathoms. + + +3. _Larcarium hexastylum_, n. sp. + +Shell smooth, with six short conical spines of equal length (= the shortest +axis of the shell), opposite in pairs on the poles of the three dimensive +axes. Network of the shell subregular, with {609}circular pores three times +as broad as the bars; about eleven pores on the half meridian, nine on the +half equator. Proportion of the three dimensive axes = 3 : 4 : 5. + +_Dimensions._--Length of the shell 0.1, breadth 0.08, thickness 0.06, pores +0.006; bars 0.002. + +_Habitat._--North Pacific, Station 244, surface. + + +4. _Larcarium axostylum_, n. sp. + +Shell thorny, with six strong conical radial spines, opposite in pairs on +the poles of the three dimensive axes. All three pairs are of different +sizes, the length of each spine corresponding nearly to the size of the +shell-axis, of which it is the prolongation. Network of the shell +subregular, with circular pores twice as broad as the bars; ten on the half +meridian, eight on the half equator. Proportion of the three dimensive axes += 2 : 3 : 4. + +_Dimensions._--Length of the shell 0.12, breadth 0.09, thickness 0.06; +pores 0.01, bars 0.005. + +_Habitat._--Western Tropical Pacific, Station 225, depth 4475 fathoms. + + +5. _Larcarium octostylum_, n. sp. + +Shell thorny, with eight thin cylindrical radial spines, opposite in pairs +in two crossed diagonal planes. Network of the shell irregular, with +roundish pores, twice to four times as broad as the bars; nine to eleven on +the half meridian, five to seven on the half equator. Proportion of the +three dimensive axes = 3 : 4 : 5. + +_Dimensions._--Length of the shell 0.11, breadth 0.09, thickness 0.07; +pores 0.006 to 0.012, bars 0.003. + +_Habitat._--Pacific, central area, Station 267, surface. + + +6. _Larcarium polystylum_, n. sp. + +Shell thorny, with numerous (twenty to thirty) stronger conical radial +spines, about as long as the shortest axis of the shell. Network of the +shell irregular, with roundish pores, twice to four times as broad as the +bars; seven to eight on the half meridian, five to six on the half equator. +Proportion of the three dimensive axes = 1 : 2 : 3. + +_Dimensions._--Length of the shell 0.09, breadth 0.06, thickness 0.03; +pores 0.006 to 0.012, bars 0.003. + +_Habitat._--South Atlantic, Station 323, surface. + + +7. _Larcarium chaetostylum_, n. sp. + +Shell bristly, with very numerous (sixty to eighty or more) very thin, +bristle-like, radial spines, somewhat longer than the longest axis of the +shell. Network irregular, with very small roundish pores, about the same +size as the bars; sixteen to eighteen on the half meridian, thirteen to +fifteen on the half equator. Proportion of the three dimensive axes = +1 : 1.5 : 2. + +{610}_Dimensions._--Length of the shell (without spines) 0.13, breadth 0.1, +thickness 0.07; pores and bars 0.004 to 0.006. + +_Habitat._--Pacific, central area, Station 273, surface. + + + +Subfamily 2. COCCOLARCIDA, Haeckel. + +_Definition._--#Larcarida# with encased lentelliptical shell, composed of +two or more concentric lentelliptical latticed shells, which are united by +radial beams (at least one inner medullary shell and one outer cortical +shell). + + + +Genus 268. _Coccolarcus_,[307] n. gen. + +_Definition._--#Larcarida# with two concentric latticed shells, an outer +lentelliptical cortical shell, and an inner (spherical or lentelliptical) +medullary shell, both connected by radial beams. Surface without radial +spines. + +The genus _Coccolarcus_ differs from _Cenolarcus_ by the possession of an +internal medullary shell. This is quite simple, either spherical or +lentelliptical, and connected with the outer cortical shell by a number of +radial beams. In the similar _Larnacilla_ this connection is effected by +four internal latticed lamellae (the half lateral wings of the transverse +girdle); therefore we find here four internal gates (on the poles of the +principal axis), absent in _Coccolarcus_. + + +1. _Coccolarcus lentellipsis_, n. sp. + +Cortical shell with smooth surface and regular network; pores circular, +twice as broad as the bars; about thirteen on the half meridian, eleven on +the half equator. Proportion of the three dimensive axes = 3 : 4 : 5. +Medullary shell spherical, half as broad as the transverse radius. + +_Dimensions._--Principal axis (or length) of the cortical shell 0.15, +transverse axis (or breadth) 0.12, sagittal axis (or thickness) 0.09; pores +0.01, bars 0.005; diameter of the medullary shell 0.03. + +_Habitat._--Pacific, central area, Station 272, depth 2600 fathoms. + + +2. _Coccolarcus platellipsis_, n. sp. + +Cortical shell with thorny surface and irregular network; pores roundish, +twice to three times as broad as the bars; sixteen to eighteen on the half +meridian, ten to twelve on the half equator. Proportion of the three +dimensive axes = 1 : 2 : 3. Medullary shell lentelliptical, one-third as +large as the cortical shell. + +{611}_Dimensions._--Length of the cortical shell 0.17, breadth 0.11, +thickness 0.06; pores 0.008 to 0.012, bars 0.004; medullary shell 0.03 to +0.06. + +_Habitat._--Pacific, central area, Station 274, depth 2750 fathoms. + + + +Genus 269. _Larcidium_,[308] n. gen. + +_Definition._--#Larcarida# with two concentric latticed shells, an outer +lentelliptical cortical shell, and an inner (spherical or lentelliptical) +medullary shell, both connected by radial beams. Surface covered with +radial spines. + +The genus _Larcidium_ differs from the foregoing _Coccolarcus_ only in the +possession of radial spines, and bears to it the same relation that +_Larcarium_ does to _Cenolarcus_. The spines are commonly symmetrically +disposed, opposite in pairs in the dimensive axes, sometimes also in +diagonal axes. + + +1. _Larcidium dissacanthum_, n. sp. + +Cortical shell with thorny surface and regular network; pores circular, +hexagonally framed, three times as broad as the bars; about thirteen on the +half meridian, eleven on the half equator. Proportion of the three +dimensive axes = 2 : 3 : 5. Medullary shell spherical, one-fourth as broad +as the cortical, connected with it by two thin beams, lying in the +principal axis, and prolonged on its poles into two strong conical spines, +somewhat longer than the greatest axis. + +_Dimensions._--Length of the cortical shell (or principal axis) 0.15, +breadth 0.09, thickness 0.07; pores 0.015, bars 0.005; medullary shell +0.025. + +_Habitat._--North Pacific, Station 253, depth 3125 fathoms. + + +2. _Larcidium hexacanthum_, n. sp. + +Cortical shell with smooth surface and regular network; pores circular, +twice as broad as the bars; about eleven on the half meridian, nine on the +half equator. Proportion of the three axes = 2 : 2.5 : 3. Medullary shell +spherical, one-third as broad as the cortical. On the surface six strong, +three-sided pyramidal spines, all about as long as the breadth of the +cortical shell. + +_Dimensions._--Length of the cortical shell 0.12, breadth 0.1, thickness +0.08; pores 0.01, bars 0.005; medullary shell 0.035. + +_Habitat._--Pacific, central area. Station 266, surface. + + +3. _Larcidium axacanthum_, n. sp. + +Cortical shell with rough surface and irregular network; pores roundish, +twice to four times as broad as the bars; about fifteen to nineteen on the +half meridian, twelve to fourteen on the half {612}equator. Proportion of +the three axes = 2 : 3 : 4. Medullary shell lentelliptical, of the same +form and structure as the cortical, but only one-third as large, connected +with it by six thin radial beams, lying in pairs in the three dimensive +axes; on the outside they are prolonged into six strong conical radial +spines, which are in pairs of different size (as in _Larcarium axostylum_); +the length of each spine nearly equals the axis of the cortical shell, of +which it is the prolongation. + +_Dimensions._--Length of the cortical shell (and the principal spines) +0.18, breadth of it (and length of the lateral spines) 0.135, thickness of +it (and length of the sagittal spines) 0.09; pores 0.005 to 0.013, bars +0.003. + +_Habitat._--Pacific, central area, Station 271, surface. + + +4. _Larcidium octacanthum_, n. sp. + +Cortical shell thorny, with irregular network; pores roundish, once to four +times as broad as the bars; about thirteen to fifteen on the half meridian, +eleven to thirteen on the half equator. Proportion of the three axes = +1 : 2.5 : 4. Medullary shell lentelliptical, one-fifth as large as the +cortical, connected with it by eight radial beams, which are situated in +two crossed diagonal planes (opposite in pairs), and are prolonged on the +surface into eight long and thin cylindrical radial spines similar to +_Tetrapyle octacantha_. + +_Dimensions._--Length of the cortical shell 0.16, breadth 0.11, thickness +0.045; pores 0.003 to 0.012, bars 0.003; medullary shell 0.02 to 0.03. + +_Habitat._--Pacific, central area, Station 263, depth 2650 fathoms. + + +5. _Larcidium dodecanthum_, n. sp. (Pl. 50, figs. 8, 8_a_). + +Cortical shell rough, with irregular network; pores roundish, twice to four +times as broad as the bars; about twelve to fourteen on the half meridian, +eight to ten on the half equator. Proportion of the three axes = 2 : 3 : 4. +Medullary shell lentelliptical, one-third as large as the cortical, +connected with it by twelve thin radial beams, which are prolonged outside +into twelve strong conical radial spines, about half as long as the breadth +of the shell. + +_Dimensions._--Length of the cortical shell 0.14, breadth 0.1, thickness +0.07; pores 0.008 to 0.015, bars 0.004; medullary shell 0.04 to 0.05. + +_Habitat._--South Pacific, Station 288, surface. + + +6. _Larcidium polyacanthum_, n. sp. + +Cortical shell spiny, with irregular network; pores roundish, once to twice +as broad as the bars; about ten to twelve on the half meridian, six to +eight on the half equator. Proportion of the three axes = 1 : 2 : 3. +Medullary shell lentelliptical, half as large as the cortical shell, +connected with it by numerous (twenty to twenty-five) radial beams, which +are prolonged outside into three-sided pyramidal spines, about as long as +the breadth of the shell. + +_Dimensions._--Length of the cortical shell 0.18, breadth 0.12, thickness +0.06; pores 0.01 to 0.015, bars 0.008; medullary shell 0.03 to 0.09. + +_Habitat._--North Pacific, Station 244, depth 2900 fathoms. + + + +{613}Subfamily 3. SPONGOLARCIDA, Haeckel. + +_Definition._--#Larcarida# with spongy lentelliptical shell (with or +without enclosed medullary shell). + + + +Genus 270. _Spongolarcus_,[309] n. gen. + +_Definition._--#Larcarida# with lentelliptical spongy shell, containing a +central cavity of the same form, without medullary shell (without radial +spines). + +The genus _Spongolarcus_ differs from _Cenolarcus_ (its probable ancestral +form) only in the development of spongy framework forming the wall of the +hollow lentelliptical shell. It corresponds, therefore, to _Plegmosphaera_ +among the #Sphaeroidea#, and to _Spongellipsis_ among the #Prunoidea#. From +these two similar spongy #Sphaerellaria# it differs in its characteristic +lentelliptical form, with three dimensive axes of unequal length. + + +1. _Spongolarcus lentellipsis_, n. sp. + +Spongy network of the shell very loose, its meshes fifteen to twenty times +as broad as the bars. Surface of the shell nearly smooth; diameter of its +internal cavity twice as large as the thickness of its wall. Proportion of +the three dimensive axes = 2 : 3 : 4. + +_Dimensions._--Length 0.16, breadth 0.12, height 0.08; thickness of the +spongy wall 0.05. + +_Habitat._--Pacific, central area, Station 274, surface. + + +2. _Spongolarcus triaxonius_, n. sp. + +Spongy network of the shell rather loose, its meshes twelve to sixteen +times as broad as the bars. Surface of the shell rough; diameter of its +internal cavity about eight times as large as the thickness of its wall. +Proportion of the three dimensive axes = 2 : 2.5 : 3. + +_Dimensions._--Length 0.25, breadth 0.2, height 0.16; thickness of the +spongy wall 0.025. + +_Habitat._--North Pacific, Station 253, surface. + + +3. _Spongolarcus dimensivus_, n. sp. + +Spongy network of the shell dense, its meshes four to eight times as broad +as the bars. Surface of the shell thorny; diameter of its internal cavity +about fifteen times as large as the thickness of its wall. Proportion of +the three dimensive axes = 3 : 4 : 5. + +_Dimensions._--Length 0.2, breadth 0.16, height 0.12; thickness of the +spongy wall 0.01. + +_Habitat._--Western Tropical Pacific, Station 225, depth 4475 fathoms. + + +{614}4. _Spongolarcus amphicentria_, Haeckel. + + ? _Amphicentria salpa_, Ehrenberg, 1861, Monatsber. d. k. preuss. Akad. + d. Wiss. Berlin, p. 296; Abhandl. d. k. Akad. d. Wiss. Berlin, 1872, Taf. + ii. fig. 18. + + ? _Spongurus salpa_, Haeckel, 1862, Monogr. d. Radiol., p. 466. + +Spongy network of the shell compact, its meshes about the same breadth as +the bars. Surface of the shell spiny, with some larger spines around the +poles of the axis; diameter of the internal cavity about six times as large +as the thickness of its wall. Proportion of the three dimensive axes = +1 : 2 : 3. (Perhaps this _Spongolarcus_ is identical with _Amphicentria +salpa_, very imperfectly described and figured by Ehrenberg, _loc. cit._?) + +_Dimensions._--Length 0.14, breadth 0.09, height 0.05; thickness of the +spongy wall 0.015. + +_Habitat._--North Atlantic; off Greenland, 1000 fathoms, Ehrenberg; Station +64, depth (2700) fathoms. + + + +Genus 271. _Stypolarcus_,[310] n. gen. + +_Definition._--#Larcarida# with lentelliptical spongy shell, composed of +compact spongy framework, without central cavity and medullary shell +(without radial spines). + +The genus _Stypolarcus_ differs from _Spongolarcus_ in the absence of any +central cavity. This is quite filled up by spongy framework, which forms +the whole mass of the lentelliptical body. _Stypolarcus_ bears therefore +the same relation to _Spongolarcus_ that _Styptosphaera_ does to +_Plegmosphaera_. + + +1. _Stypolarcus spongiosus_, n. sp. + +Lentelliptical shell composed in the whole mass of loose, spongy framework +of similar texture, with irregular meshes, about ten to twenty times as +broad as the thin bars. Surface rough, without radial spines. Proportion of +the three axes = 3 : 4 : 5. + +_Dimensions._--Length 0.2, breadth 0.16, height 0.12. + +_Habitat._--Antarctic Ocean, Station 157, depth 1950 fathoms. + + + +Family XXV. #LARNACIDA#, Haeckel, 1883 (Pl. 50, figs. 3-8). + +_Definition._--#Larcoidea# with a regular, completely latticed, +lentelliptical cortical shell, without open gates and annular +constrictions; either this cortical shell or the enclosed medullary shell +is trizonal, composed of three elliptical, latticed, dimensive girdles of +different sizes, perpendicular one to another. + +{615}The family #Larnacida# immediately follows the Larcarida as the next +simple group of all #Larcoidea#; some genera of both groups (such as +_Larnacalpis_ and _Coccolarcus_, or _Larnacantha_ and _Larcidium_) may +easily be confounded from their being so much alike. In both the +lentelliptical shell is composed of two concentric shells, an inner +(medullary) and an outer (cortical) shell. But the connection between these +shells and the construction of the inner shell is quite different in the +two groups. Whilst in the Larcarida the medullary shell is connected with +the cortical shell simply by radial beams, here in the Larnacida this +connection is effected by two latticed lamellae, which are the lateral +wings of a transverse girdle. Therefore we encounter here for the first +time that peculiar mode of growth which characterises the greater part of +the #Larcoidea#, but particularly the Pylonida. But whilst in the Pylonida +between the three crossed lattice-girdles, remain four open gates, here in +the Larnacida the gates become closed by lattice-work; the lentelliptical +cortical shell becomes perfect. + +The most simple genus of Larnacida, and no doubt the common ancestral form +of this whole family, is _Larnacilla_ (Pl. 50, figs. 1, 1_a_, 1_b_). The +most important shell of this typical genus is composed of a simple +lentelliptical medullary shell and of three elliptical latticed girdles +surrounding it, perpendicular one to another. These three "dimensive +girdles" lie in the perimeter of the three dimensive planes, the minor (and +first) in the equatorial plane, the second (and major) in the lateral +plane, the third (and intermediate) in the sagittal plane. Therefore we +have before us the same "trizonal shell" as in the important genus +_Trizonium_ among the Pylonida. But whilst in _Trizonium_, as in all +Pylonida, the four gates between the girdles remain open, here in +_Larnacilla_ they become perfectly closed by lattice-work. + +The formation of the typical "_Larnacilla_-shell" begins with a simple, +spherical or lentelliptical lattice-shell, from both sides of which arise +two latticed "lateral wings" opposite on the poles of the transverse axis. +These two wings are comparable to the lateral chambers of _Tholartus_ +(among the Tholonida), but differ by two large openings. Each wing is a +short cylindrical tube with latticed wall, open at both ends; the axis of +the tube (going through the centre of the open ends) is parallel to the +principal axis of the whole shell (and of the central chamber). Therefore +both wings form together a transverse ring, the middle of which encloses +the central chamber. The distal parts of both wings grow towards the poles +of the principal axis; if they became united here, the second (lateral) +girdle would be complete. Between it and the first girdle four open gates +remain ("_Tetrapyle_"); but these become overgrown by the third or sagittal +girdle, and at last the gates between this and the two other girdles become +closed by lattice-work. This perfect fenestration of the trizonal cortical +shell, and the complete closing of the gates between the girdles by +network, is the only difference between _Trizonium_ and _Larnacilla_. + +In _Larnacilla_ and in the nearly allied _Larnacidium_ (only differing by +radial spines {616}on the surface) the "trizonal shell" is an external or +"cortical shell," enclosing the central capsule, the interior of which only +contains the simple central chamber and the jointed proximal parts of both +lateral wings. In the other genera of Larnacida (by proceeding growth) this +trizonal _Larnacilla_-shell becomes enclosed by the growing central capsule +and is now only a "medullary shell," whilst on the outside of the central +capsule in the same manner is developed an outer cortical shell +(_Larnacalpis_, _Larnacantha_); and perhaps the same process may be +repeated. But sometimes also this cortical shell becomes doubled by a +simple envelop of network (_Larnacoma_). In the Larnacospongida the +cortical shell is composed of a spongy framework (corresponding to the +Spongolarcida in the foregoing family). + +The lattice-work of the Larnacida is commonly irregular (as in most other +#Larcoidea#), and its pores have little signification for the different +species. On the outer surface often arise radial spines, symmetrically +disposed either in dimensive planes or in diagonal planes. + +The central capsule is constantly a true lentellipsis or a "triaxial +ellipsoid," characterised by three halving, elliptical dimensive planes, +perpendicular one to another. It bears a different relation to the skeleton +in the two subfamilies of Larnacida. In the first subfamily, the +Larnacillida (_Larnacilla_, _Larnacidium_), the central capsule encloses +only the simple spherical or lentelliptical central chamber ("simple +medullary shell"), and is enveloped by the trizonal cortical shell. In the +other subfamily, the Larnacalpida (_Larnacalpis_, _Larnacospongus_, &c.), +this trizonal "_Larnacilla_-shell" becomes enclosed by the overgrowing +central capsule, which now becomes enveloped by an external, latticed or +spongy, lentelliptical "cortical shell." + +_Synopsis of the Genera of Larnacida._ + + ------------------------------------------------------------------------- + I. Subfamily Larnacillida. + Medullary shell simple, spherical or subspherical. Cortical shell + lentelliptical, trizonal; between them four gates. + ------------------------------------------------------------------------- + Shell without radial spines, 272. _Larnacilla_. + + Shell with radial spines, 273. _Larnacidium_. + ------------------------------------------------------------------------- + II. Subfamily Larnacalpida. + Medullary shell _Larnacilla_-shaped, double; the inner spherical or + subspherical, the outer lentelliptical and trizonal. + ------------------------------------------------------------------------- + { { Without radial + { Cortical { spines, 274. _Larnacalpis_. + { shell { + Cortical shell simple { simple. { With radial + or double, but not { { spines, 275. _Larnacantha_. + spongy. { + { Cortical shell double, + { without radial spines, 276. _Larnacoma_. + + { Shell without radial + Cortical shell simple { spines, 277. _Larnacospongus_. + or double, wholly or { + partly spongy. { Shell with radial spines, 278. _Larnacostupa_. + + + +{617}Subfamily 1. LARNACILLIDA, Haeckel. + +_Definition._--#Larnacida# with a simple, spherical or lentelliptical, +medullary shell, connected by the lateral wings of a latticed transverse +girdle with the simple lentelliptical trizonal cortical shell; the central +capsule encloses the former and is enveloped by the latter. + + + +Genus 272. _Larnacilla_,[311] n. gen. + + +_Definition._--#Larnacida# with a simple lentelliptical cortical shell, +connected by the lateral wings of a latticed transverse girdle with the +simple, spherical or lentelliptical, medullary shell. Surface without +radial spines. + +The genus _Larnacilla_ represents the most simple form of Larnacida, and at +the same time the most important common ancestral form, from which the +greater number of #Larcoidea# may be derived, viz., all those genera which +possess the characteristic "_Larnacilla_-shaped medullary shell." This +typical form of medullary shell may be derived from the genus _Trizonium_ +among the Pylonida by the closing of the four open gates of this genus. The +free opening of these four gates becomes overgrown and closed by +lattice-work, developed from the free edges of the three crossed girdles, +and thus finally all three girdles are united in the form of a simple +lentelliptical shell (Pl. 50, figs. 1, 1_a_, 1_b_). Seen from the sagittal +poles (or from the poles of the shortest axis, fig. 1), the shell exhibits +on both sides of the small spherical medullary shell the two lateral wings +of the transverse girdle from the face; seen from the lateral poles (or +from the poles of the transverse axis, fig. 1_a_), one of these wings +appears in the optical section as an oblong ring, which seemingly encloses +the concentric medullary shell, and on both sides is grown together with +the sagittal girdle; seen from the principal poles (or from the poles of +the longitudinal axis, fig. 1_b_), both wings exhibit their elliptical +opening (at the right and left from the central medullary shell). The two +concentric shells are only connected by the two lateral tube-like wings of +the transverse girdle; the lateral and the sagittal girdles have no +connection with the medullary shell. The latter is sometimes spherical, at +other times lentelliptical. + + +1. _Larnacilla typus_, n. sp. (Pl. 50, fig. 1, 1_a_, 1_b_). + +Cortical shell with smooth surface and with subregular network; pores twice +as broad as the bars; about twelve pores on the half meridian, ten on the +half equator. Proportion of the three dimensive axes = 2 : 3 : 4. Internal +four gates (between transverse and lateral girdles) roundish-triangular, +little broader than high. Medullary shell spherical, scarcely one-third as +broad as the lentelliptical cortical shell. + +{618}_Dimensions._--Length of the cortical shell (or principal axis) 0.13, +breadth of it (or transverse axis) 0.1, height of it (or sagittal axis) +0.07; pores 0.006, bars 0.003; medullary shell (diameter) 0.03. + +_Habitat._--Pacific, central area, Station 271, depth 2425 fathoms. + + +2. _Larnacilla prometor_, n. sp. + +Cortical shell with rough surface and regular network; pores three times as +broad as the bars; about ten on the half meridian, eight on the half +equator. Proportion of the three axes = 1 : 2 : 3. Internal four gates +(between transverse and lateral girdles) kidney-shaped, twice as broad as +high. Medullary shell lentelliptical, of the same form as the external +cortical shell, but only one third as large. + +_Dimensions._--Length of the cortical shell 0.15, breadth 0.1, height 0.05, +pores 0.015, bars 0.005; medullary shell 0.02 to 0.05. + +_Habitat._--Indian Ocean, Zanzibar, Pullen, depth 2200 fathoms. + + +3. _Larnacilla subglobosa_, n. sp. + +Cortical shell nearly spherical, with thorny surface and irregular network; +pores roundish, twice to four times as broad as the bars; twelve to sixteen +in the half circumference. Proportion of the three axes very little +different = 1.3 : 1.4 : 1.5. Internal four gates elliptical, one and a half +times as broad as high. Medullary shell spherical, one-fourth as broad as +the cortical shell. + +_Dimensions._--Length of the cortical shell 0.15, breadth 0.14, height +0.13; pores 0.006 to 0.012, bars 0.003; medullary shell 0.035. + +_Habitat._--Pacific, central area. Station 266, depth 2750 fathoms. + + +4. _Larnacilla medullaris_, n. sp. + +Cortical shell lentelliptical, with smooth surface and irregular network; +pores roundish, very small, scarcely as broad as the bars; about eight to +nine on the half meridian, six to seven on the half equator. Proportion of +the three axes = 3 : 4 : 6. Internal four gates elliptical. Medullary shell +spherical, scarcely one-third as broad as the cortical shell. (This small +species may be only the medullary shell of some other Larcoid, the cortical +shell of which is not yet formed.) + +_Dimensions._--Length of the cortical shell 0.06, breadth 0.04, height +0.03; pores and bars about 0.004; medullary shell 0.013. + +_Habitat._--Pacific, central area, Station 265, depth 2900 fathoms. + + + +Genus 273. _Larnacidium_,[312] n. gen. + +_Definition._--#Larnacida# with a simple lentelliptical cortical shell, +connected by the lateral wings of a latticed transverse girdle with the +simple, spherical or lentelliptical, medullary shell. Surface armed with +radial spines. + +{619}The genus _Larnacidium_ has the same shell-formation as the foregoing +_Larnacilla_, and differs from it only in the possession of radial spines +on the surface, which in all known species exhibit a symmetrical +disposition. From the nearly allied genus _Larcidium_ it differs in the +characteristic mode of connection between the two shells, owing to the +different kind of growth. In _Larcidium_ this connection is effected only +by radial beams, whereas in _Larnacidium_ (as in all Larnacida) by two +lateral latticed tubes, the wings of the primary transverse girdle. + + +1. _Larnacidium staurobelonium_, n. sp. + +Cortical shell smooth, with four strong conical, radial spines in the +lateral plane, opposite in pairs, two on the poles of the principal and two +on the poles of the transverse axis. Pores subregular, circular, twice as +broad as the bars; about twelve on the half meridian. Proportion of the +three axes = 2 : 3 : 4. Medullary shell spherical, one-third as broad as +the cortical shell. + +_Dimensions._--Length of the cortical shell 0.12, breadth 0.09, height +0.06; pores 0.008, bars 0.04; medullary shell 0.03. + +_Habitat._--North Pacific Station 244, depth 2900 fathoms. + + +2. _Larnacidium hexabelonium_, n. sp. + +Cortical shell thorny, with six strong, three-sided pyramidal, radial +spines, lying opposite in pairs on the poles of the three dimensive axes. +Pores subregular, circular, three times as broad as the bars; about +fourteen on the half meridian. Proportion of the three axes = 2 : 2.5 : 3. +Medullary shell spherical, one-third as broad as the cortical shell. + +_Dimensions._--Length of the cortical shell 0.14, breadth 0.11, height +0.08; pores 0.01, bars 0.003; medullary shell 0.04. + +_Habitat._--South Pacific, Station 295, depth 1500 fathoms. + + +3. _Larnacidium polybelonium_, n. sp. + +Cortical shell very spiny, with numerous (twenty to thirty or more) larger +thin radial spines, about as long as the shell. Pores irregular, twice to +five times as broad as the bars; about sixteen on the half meridian. +Proportion of the three axes = 2 : 2.5 : 3. Medullary shell +lentelliptical, half as large as the cortical shell. + +_Dimensions._--Length of the cortical shell 0.11, breadth 0.09, height +0.07; pores 0.004 to 0.01, bars 0.002; length of the medullary shell 0.06, +breadth 0.05, height 0.04. + +_Habitat._--Western Tropical Pacific, Station 225. depth 4475 fathoms. + + + +Subfamily 2. LARNACALPIDA, Haeckel. + +_Definition._--#Larnacida# with a double, trizonal, _Larnacilla_-shaped +medullary shell, enclosed in the central capsule, and enveloped by a simple +or double, latticed or spongy, lentelliptical, cortical shell. + + + +{620}Genus 274. _Larnacalpis_,[313] n. gen. + +_Definition._--#Larnacida# with a simple lentelliptical cortical shell, +without radial spines. Medullary shell double, _Larnacilla_-shaped. + +The genus _Larnacalpis_ represents the most simple form of the sub-family +Larnacalpida, and is very important as the common original form of all +those #Larcoidea# in which a double _Larnacilla_-shaped medullary shell is +surrounded by a simple, perfectly closed, latticed, lentelliptical cortical +shell. Therefore the same typical, trizonal, lentelliptical shell, which in +_Larnacilla_ represents the external envelop (or cortical shell) of the +central capsule, here in _Larnacalpis_ becomes enclosed as an internal +nucleus (or medullary shell) in the interior of the central capsule, and +this latter becomes overgrown by a new lentelliptical cortical shell. The +connection between the two shells of _Larnacalpis_ is either effected by a +number of radial beams (e.g., in _Larnacalpis triaxonia_ by six beams +situated in the three dimensive axes), or by two lateral, latticed, +tube-like wings, which are repetitions of the smaller lateral wings +connecting its external shell with the internal medullary shell (as in +_Larnacalpis lentellipsis_). The latter species may be regarded as a +_Pylonium_ with a completely latticed shell. + + +1. _Larnacalpis lentellipsis_, n. sp. (Pl. 50, figs. 2, 2_a_, 2_b_). + +Cortical shell with thorny surface and irregular network; pores roundish, +twice to four times as broad as the bars; about sixteen on the half +meridian, twelve on the half equator. Proportion of the three dimensive +axes = 2 : 3 : 4. Medullary shell one-third as large as the cortical, with +four elliptical internal gates, connected with it by two opposite beams in +the principal axis and by two latticed wings in the transverse axis; +therefore between the two shells are four large kidney-shaped gates, halved +by the polar beams (as in _Octopyle_). + +_Dimensions._--Length of the cortical shell (or principal axis) 0.14, +breadth (or transverse axis) 0.11, height (or sagittal axis) 0.07; pores +0.01 to 0.02, bars 0.005; length of the medullary shell 0.05, breadth 0.04, +height 0.03. + +_Habitat._--Pacific, central area, Station 273, depth 2600 fathoms. + + +2. _Larnacalpis phacodiscus_, n. sp. + +Cortical shell with thorny surface and regular network; pores circular, +twice as broad as the bars; about ten on the half meridian, eight on the +half equator. Proportion of the three axes = 2 : 2.5 : 3. Medullary shell +half as large as the cortical, with four kidney-shaped internal gates. + +_Dimensions._--Length of the cortical shell 0.13, breadth 0.11, height +0.09; pores 0.012, bars 0.006; length of the medullary shell 0.06, breadth +0.045, height 0.03. + +_Habitat._--North Pacific, Station 253, depth 3125 fathoms. + + +{621}3. _Larnacalpis macrococcus_, n. sp. + +Cortical shell with spiny surface and regular network; pores circular, +small, of the same breadth as the bars; about twenty-two on the half +meridian, nineteen on the half equator. Proportion of the three axes = +2 : 3 : 4. Medullary shell two-thirds as large as the cortical, with four +wide internal semicircular gates. + +_Dimensions._--Length of the cortical shell 0.1, breadth 0.075, height +0.05; pores and bars 0.003; length of the medullary shell 0.066, breadth +0.05, height 0.032. + +_Habitat._--Western Tropical Pacific, Station 224, depth 1850 fathoms. + + +4. _Larnacalpis subsphaerica_, n. sp. + +Cortical shell with rough surface and irregular network; roundish pores +twice to five times as broad as the bars; about twenty-four on the half +meridian, twenty-one on the half equator. Proportion of the three axes = +1.2 : 1.3 : 1.4. Medullary shell half as large as the cortical, with four +elliptical internal gates. + +_Dimensions._--Length of the cortical shell 0.14, breadth 0.13, height +0.12; pores 0.004 to 0.01, bars 0.002; length of the medullary shell 0.08, +breadth 0.07, height 0.06. + +_Habitat._--Pacific, central area, Station 266, depth 2750 fathoms. + + +5. _Larnacalpis triaxonia_, n. sp. (Pl. 50, fig. 3). + +Cortical shell with smooth surface and peculiar network, composed of four +meridian rows of larger pores (five large elliptical pores on each half +meridian, the largest in the equator) and numerous small irregular pores +between them. Proportion of the three axes = 2 : 3 : 4. Medullary shell +with four semicircular internal gates, about one-fourth as large as the +cortical, connected with it by six thin radial beams, opposite in pairs in +the three dimensive axes. + +_Dimensions._--Length of the cortical shell 0.14, breadth 0.1, height 0.07; +large pores 0.03, small pores 0.002 to 0.01, bars 0.002 to 0.01; length of +the medullary shell 0.04, breadth 0.03, height 0.02. + +_Habitat._--Pacific, central area, Station 263, depth 2650 fathoms. + + + +Genus 275. _Larnacantha_,[314] n. gen. + +_Definition._--#Larnacida# with a simple lentelliptical cortical shell, +armed with symmetrically disposed radial spines. Medullary shell double, +_Larnacilla_-shaped. + +The genus _Larnacantha_ has the same characteristic shell-formation as the +foregoing _Larnacalpis_, and differs from it only in the possession of +radial spines, which are symmetrically distributed on the surface in a +definite order. Commonly these spines are external prolongations of the +internal radial beams, which connect the double _Larnacilla_-shaped +medullary shell with the simple lentelliptical cortical shell. + + +{622}1. _Larnacantha dissacantha_, n. sp. + +Cortical shell smooth, with two large cylindrical spines, opposite on the +poles of the principal axis, and somewhat longer than it. Pores regular, +circular, three times as broad as the bars; about eleven on the half +meridian. Proportion of the three axes = 2 : 3 : 4. Medullary shell +one-third as large as the cortical shell. + +_Dimensions._--Length of the cortical shell (principal axis) 0.13, breadth +(transverse axis) 0.1, height (sagittal axis) 0.07; pores 0.009, bars +0.003; length of the _Larnacilla_-shaped medullary shell 0.045. + +_Habitat._--North Pacific, Station 256, depth 2950 fathoms. + + +2. _Larnacantha stauracantha_, n. sp. + +Cortical shell smooth, with four large conical spines in the lateral plane, +two larger opposite on the poles of the principal, two smaller on those of +the transverse axis. Pores regular, circular, twice as broad as the bars; +about seventeen on the half meridian. Proportion of the three axes = +3 : 3.5 : 4. Medullary shell one-third as large as the cortical shell. + +_Dimensions._--Length of the cortical shell 0.15, breadth 0.13, height +0.11; pores 0.008, bars 0.004; length of the medullary shell 0.05. + +_Habitat._--Pacific, central area, Station 274, surface. + + +3. _Larnacantha quadricornis_, n. sp. + +Cortical shell spiny, with four strong, horn-like curved spines in the +lateral plane, opposite in pairs on the poles of the crossed diagonal axes. +Pores irregular, roundish, twice to four times as broad as the bars; about +fourteen on the half meridian. Proportion of the three axes = 2 : 3 : 4. +Medullary shell one-third as large as the cortical shell. + +_Dimensions._--Length of the cortical shell 0.14, breadth 0.11, height +0.07; pores 0.006 to 0.012, bars 0.003; length of the medullary shell 0.05. + +_Habitat._--Pacific, central area, Station 270, surface. + + +4. _Larnacantha hexacantha_, n. sp. (Pl. 50, fig. 4). + +Cortical shell thorny, with six strong conical radial spines in the lateral +plane, two opposite on the poles of the principal axis, four others +opposite in pairs on the poles of the two crossed diagonal axes. Pores with +peculiar distribution; twelve large elliptical pores (nearly of the size of +the medullary shell) symmetrically disposed in four crossed meridians +(between the sagittal and the lateral meridians), separated by bands of +smaller irregular pores. Proportion of the three axes = 3 : 4 : 5. +Medullary shell hexagonal, one-third as large as the cortical shell. + +_Dimensions._--Length of the cortical shell 0.14, breadth 0.11, height +0.08; large pores 0.04, small pores 0.003 to 0.01, bars 0.004; length of +the medullary shell 0.05. + +_Habitat._--Pacific, central area, Station 263, depth 2650 fathoms. + + +{623}5. _Larnacantha bicruciata_, n. sp. (Pl. 50, fig. 5). + +Cortical shell thorny, in the lateral plane with eight strong conical +radial spines, alternating with eight smaller spines; four of the eight +stronger spines opposite on the poles of the principal and transverse axes +(in the figure 5, by mistake, not represented large enough), four others +between those, opposite on the poles of the two crossed diagonal axes. +Pores with a peculiar disposition; on both flat sides of the lentellipsis +an elliptical ring of eight large elliptical pores (alternating with the +eight stronger radial spines), separated by bands of smaller irregular +pores. Proportion of the three axes = 2 : 3 : 4. Medullary shell nearly +half as long as the cortical shell. + +_Dimensions._--Length of the cortical shell 0.16, breadth 0.13, height +0.08; large pores 0.03, small pores 0.003 to 0.01, bars 0.006; length of +the medullary shell 0.07. + +_Habitat._--Indian Ocean, surface, Madagascar (Rabbe). + + +6. _Larnacantha octacantha_, n. sp. + +Cortical shell thorny, with eight long and thin, cylindrical, radial +spines, lying opposite in pairs in two crossed diagonal planes. Pores +irregular, roundish, twice to five times as broad as the bars; about +sixteen on the half meridian. Proportion of the three axes = 1 : 1-1/3 : 2. +Medullary shell scarcely one-fourth as long as the cortical shell. (This +species resembles closely the common _Tetrapyle octacantha_, from which it +seems to be developed by a complete over-growing of the four gates, which +become closed by a network connecting the free edges of the transverse and +lateral girdles.) + +_Dimensions._--Length of the cortical shell 0.18, breadth 0.13, height 0.1; +pores 0.005 to 0.015, bars 0.003; length of the medullary shell 0.04. + +_Habitat._--Cosmopolitan; Mediterranean, Atlantic, Pacific, surface. + + +7. _Larnacantha cladacantha_, n. sp. + +Cortical shell very spiny, with eight longer ramified spines, lying +opposite in pairs in two crossed diagonal planes; each spine with two to +six irregular, lateral branches. Pores irregular, roundish, twice to three +times as broad as the bars; about twelve on the half meridian. Proportion +of the three axes = 5 : 6 : 7. Medullary shell nearly half as long as the +cortical shell. (Differs from the foregoing by the branching spines end the +larger medullary shell.) + +_Dimensions._--Length of the cortical shell 0.15, breadth 0.13, height +0.11; pores 0.01 to 0.015, bars 0.005; length of the medullary shell 0.07. + +_Habitat._--Indian Ocean, surface, Cocos Islands (Rabbe). + + +8. _Larnacantha prismatica_, n. sp. (Pl. 50, fig. 6). + +Cortical shell smooth, four-sided prismatic, with eight short, parallel, +three-sided pyramidal spines; these lie opposite in pairs in four parallel +longitudinal lines, as prolongations of the four {624}lateral edges of the +prism, and arise from its eight corners. Pores regular, circular, three +times as broad as the bars; about fourteen on the half meridian. Proportion +of the three axes = 2 : 3 : 4. Medullary shell half as long as the cortical +shell. + +_Dimensions._--Length of the cortical shell 0.11, breadth 0.07, height +0.05; pores 0.006, bars 0.002; length of the medullary shell 0.06. + +_Habitat._--Pacific, central area, Station 263, depth 2650 fathoms. + + +9. _Larnacantha decacantha_, n. sp. + +Cortical shell thorny, with ten short and stout, conical, radial spines, +two opposite on the poles of the principal axis (as prolongations of inner +axial beams), eight others opposite in pairs in two crossed diagonal +planes. Pores irregular, roundish, twice to four times as broad as the +bars; about sixteen on the half meridian. Proportion of the three axes = +3 : 3.75 : 4. Medullary shell about one-third as long as the cortical +shell. + +_Dimensions._--Length of the cortical shell 0.16, breadth 0.15, height +0.12; pores 0.008 to 0.016, bars 0.004; length of the medullary shell 0.06. + +_Habitat._--North Atlantic, Station 354, surface. + + +10. _Larnacantha dodecantha_, n. sp. + +Cortical shell nearly smooth, but with twelve strong conical radial spines; +four in the lateral plane opposite in pairs (two on the poles of the +principal, and two on the poles of the transverse axis); eight others +opposite in pairs in two crossed diagonal planes. Pores with a peculiar +disposition: twelve large elliptical pores in two crossed meridian planes +(alternating with the twelve spines), separated by bands of irregular small +pores. Proportion of the three axes = 1 : 1.5 : 2. Medullary shell +hexagonal, one-third as long as the cortical shell. + +_Dimensions._--Length of the cortical shell 0.15, breadth 0.11, height +0.08; large pores 0.03, small pores 0.005 to 0.01, bars 0.003; length of +the medullary shell 0.05. + +_Habitat._--Pacific, central area, Station 265, depth 2900 fathoms. + + +11. _Larnacantha drymacantha_, n. sp. + +Cortical shell very spiny, on the whole surface covered with a forest of +numerous (thirty to fifty or more) large branched spines, about the length +of the shell; each spine with three to nine lateral branches, simple or +forked (very similar to _Cromyodrymus abietinus_, Pl. 30, fig. 6). Pores +very irregular, roundish. Proportion of the three axes = 2 : 2.5 : 3. +Medullary shell half as long as the cortical shell. + +_Dimensions._--Length of the cortical shell 0.16, breadth 0.13, height 0.1; +pores 0.005 to 0.015, bars 0.03; length of the medullary shell 0.08. + +_Habitat._--Pacific, central area, Station 271, depth 2425 fathoms. + + + +{625}Genus 276. _Larnacoma_,[315] n. gen. + +_Definition._--#Larnacida# with double lentelliptical cortical shell, +without radial spines. Medullary shell double, _Larnacilla_-shaped. + +The genus _Larnacoma_ has originated from the nearly allied _Larnacalpis_ +by duplication of the cortical shell. Whilst in both genera the connection +between the _Larnacilla_-shaped medullary shell and the primary cortical +shell is the same, many short radial beams arise from the surface of the +latter in _Larnacoma_, which at constant equal distances from it unite by a +network forming the secondary or outer cortical shell. It differs from the +similar Druppulida (_Cromyodruppa_) by the sagittal flattening of the +lentelliptical shell and the _Larnacilla_-form of the double medullary +shell. + + +1. _Larnacoma lentellipticum_, n. sp. + +Shell with smooth surface and elliptical perimeter, one and a third times +as long as broad. All four shells lentelliptical. Distance between the two +cortical shells about twice as great as the distance of the inner cortical +and outer medullary shell. Network of both outer shells irregular, with +large roundish pores, twice to six times as broad as the bars. + +_Dimensions._--Length (or principal axis) of the first (innermost) shell +0.03, second 0.08, third 0.16, fourth (outermost) 0.27, breadth (or +transverse axis) corresponding--(A) 0.02, (B) 0.05, (C) 0.11, (D) 0.2. + +_Habitat._--South Atlantic, Station 323, depth 1900 fathoms. + + +2. _Larnacoma quadruplex_, n. sp. + +Shell with thorny surface and elliptical perimeter, one and a fifth times +as long as broad. All four shells lentelliptical. Distance between the two +cortical shells somewhat smaller than the distance between the inner +cortical and outer medullary shell. Network of both outer shells irregular, +with large roundish pores, twice to ten times as broad as the bars. + +_Dimensions._--Length of the first shell 0.02, second 0.06, third 0.15, +fourth 0.24; breadth corresponding--(A) 0.016, (B) 0.04, (C) 0.11, (D) 0.2. + +_Habitat._--South Atlantic, Station 335, depth 1425 fathoms. + + +3. _Larnacoma hexagonium_, n. sp. + +Shell with thorny surface and hexagonal perimeter, as long as broad. All +four shells hexagonal, connected by six piercing radial beams (two in the +principal axis, four others in two crossed diagonals). Distance between the +two cortical shells somewhat greater than the distance between the inner +cortical and outer medullary shell. Network of both outer shells +subregular, with small circular pores, twice as broad as the bars. + +{626}_Dimensions._--Length of the first shell 0.02, second 0.05, third +0.09, fourth 0.16; breadth corresponding--(A) 0.015, (B) 0.035, (C) 0.065, +(D) 0.12. + +_Habitat._--South Atlantic, west of Tristan da Cunha, Station 332, depth +2200 fathoms. + + + +Genus 277. _Larnacospongus_,[316] n. gen. + +_Definition._--#Larnacida# with spongy lentelliptical cortical shell, +without radial spines. Medullary shell double, _Larnacilla_-shaped. + +The genus _Larnacospongus_ differs from the nearly allied genera +_Larnacalpis_ and _Larnacoma_ by the spongy texture of the lentelliptical +cortical shell whilst the enclosed medullary shell in both genera is the +same trizonal _Larnacilla_-shell. Therefore _Larnacospongus_ (and the +following nearly related _Larnacostupa_) can be derived directly by +development of a spongy envelop either from _Larnacilla_ and _Larnacalpis_, +or from _Trizonium_ and _Amphipyle_. But some species of these spongy +genera appear to be derived rather from _Tetrapyle_ or _Pylonium_, perhaps +also from _Cubotholus_. Their phylogenetic origin may be explained in +different ways. + + +1. _Larnacospongus larnacillifer_, n. sp. + +Cortical shell lentelliptical, one and a half times as long as broad, with +rough surface and rather loose spongy framework, directly enclosing a +trizonal _Larnacilla_-shell of the same form, but of only one-third its +size. + +_Dimensions._--Length of the whole shell 0.17, breadth 0.12; length of the +medullary shell 0.06, breadth 0.04. + +_Habitat._--South Atlantic, east coast of Patagonia, Station 319, surface. + + +2. _Larnacospongus tetrapylifer_, n. sp. + +Cortical shell lentelliptical, one and a third times as long as broad, with +thorny surface; composed of an outer envelop of loose spongy framework and +an inner lattice-shell with four kidney-shaped gates, like _Tetrapyle;_ the +latter encloses a trizonal medullary shell of one-fourth its size. + +_Dimensions._--Length of the whole shell 0.22, breadth 0.16; length of the +medullary shell 0.045, breadth 0.035. + +_Habitat._--South Atlantic, west of Tristan da Cunha, Station 332, surface. + + + +{627}Genus 278. _Larnacostupa_,[317] n. gen. + +_Definition._--#Larnacida# with spongy lentelliptical cortical shell, with +radial spines on the surface. Medullary shell double, _Larnacilla_-shaped. + +The genus _Larnacostupa_ differs from the preceding Larnacospongus only in +the possession of radial spines, covering either the whole surface +irregularly or disposed in a certain symmetrical order. + + +1. _Larnacostupa octacantha_, n. sp. + +Cortical shell lentelliptical, with thorny surface, and rather dense, +irregular, spongy framework, which arises from an inner latticed cortical +shell, like that of _Tetrapyle_ or _Pylonium_. This latter is twice as +large as the enclosed _Larnacilla_-shell. Eight long and thin, cylindrical, +radial spines, opposite in pairs in two diagonal planes. (Seems to be the +common _Tetrapyle octacantha_, enveloped by an outer spongy framework +mantle.) + +_Dimensions._--Length of the whole shell (without spines) 0.22, breadth +0.16; length of the medullary shell 0.06, breadth 0.04. + +_Habitat._--Indian Ocean, Madagascar, Rabbe, surface. + + +2. _Larnacostupa spinosa_, n. sp. + +Cortical shell lentelliptical, about one and a half times as long as broad, +with very lax and irregular spongy framework, arising from a nearly +quadrangular lattice-shell like that of _Tetrapyle_; this latter encloses a +_Larnacilla_-shell of half its size. Whole surface covered with thin +bristle-like radial spines, of about the length of the shell. + +_Dimensions._--Length of the whole shell (without spines) 0.18, breadth +0.12; length of the medullary shell 0.05, breadth 0.035. + +_Habitat._--Antarctic Ocean, off Kerguelen, Station 150, surface. + + +3. _Larnacostupa dendrophora_, n. sp. + +Cortical shell nearly spherical, scarcely longer than broad, with lax, +irregular spongy framework, arising from a lentelliptical trizonal +medullary shell (like _Larnacilla_). Whole surface covered with thin +arborescent radial spines, about half as long as the shell, each spine with +three to six irregular branches. + +_Dimensions._--Length of the whole shell (without spines) 0.15, breadth +0.13; length of the medullary shell 0.07, breadth 0.04. + +_Habitat._--Antarctic Ocean, Station 154, surface. + + + +{628}Family XXVI. #PYLONIDA#, Haeckel, 1881 (Pl. 9). + +_Pylonida_, Haeckel, 1881, Prodromus, p. 463. + +_Definition._--#Larcoidea# with regular, incompletely latticed cortical +shell, distinguished by two to four or more symmetrically disposed gates or +large fissures remaining between one to three latticed dimensive girdles +(perpendicular one to another). One, two, or three concentric systems of +such girdles (each system with three girdles) may be developed. + +The family #Pylonida# is the most important and interesting among all the +#Larcoidea#, not only because it is much richer in different and peculiar +forms than the other families of this section, but also because it has +direct and very complex relations to all the other families of #Larcoidea#. +It is even possible that the Pylonida represent the original ancestral +group of the whole section, and that the apparently simpler group of the +Larcarida must be derived from the former by retrogressive metamorphosis. + +Till the year 1881 the family Pylonida, which here now exhibits ten genera +with eighty-six species, was only represented by one single species, +accurately described and extensively illustrated by Johannes Mueller in +1858, the well known and widely distributed cosmopolitan _Tetrapyle +octacantha_ (Abhandl. d. k. Akad. d. Wiss. Berlin, p. 33, Taf. iii.). A +slight modification of it was afterwards described by Ehrenberg as +_Schizomma quadrilobum_ (Abhandl. d. k. Akad. d. Wiss. Berlin, 1872, Taf. +ii. fig. 12). A more accurate description of it, with a good explanation of +its characteristic growth, was given in 1879 by Richard Hertwig in his +Organismus der Radiolarien (pp. 52-54, Taf. iv. figs. 7, 8; Taf. vi. figs. +2, 5). In my Prodromus (1881, p. 463) I constituted for a large number of +allied species, detected in the Challenger collection, the special family +Pylonida, and distinguished among it twelve different genera. However, I +think it now better to restrict the definition of the family as given in +the above definition, and to remove from it a number of genera formerly +with it united, as the genera _Triopyle_ and _Hexapyle_, appertaining to +the #Discoidea#. + +The characteristic type of all true Pylonida is clearly demonstrated by +their peculiar mode of growth, the consequence of which is the imperfect +lattice-work of the fenestrated larcoid shell. This remarkable growth is +effected by the development of elliptical latticed girdles (or rings), +which enclose a quite simple, spherical, subspherical, or lentelliptical +primordial shell. The girdles lie in three different planes, perpendicular +to one another, and are of different sizes; each girdle being somewhat +larger than the foregoing and somewhat smaller than the following girdle. +Between these latticed girdles remain on the surface of the shell large +openings or "gates," which are not closed by network, and it is just the +symmetrical disposition and form of these open "gates," separated and +enclosed by the fenestrated girdles, which give to the Pylonida their +characteristic appearance. + +{629}To understand clearly this peculiar constitution of the Pylonida-shell +by a system of alternating girdles, developing one after the other it is +indispensable to pay careful attention to the three different elliptical +dimensive planes, which characterise all #Larcoidea#, and to the three +different dimensive axes, which bisect those planes. The girdle which first +develops around simple primordial shell or central chamber is the +transverse girdle, lying in the equatorial plane; then comes, secondly, the +lateral girdle, lying in the lateral plane; and thirdly follows the +sagittal girdle, lying in the sagittal or median plane. The three simplest +genera of the Pylonida--_Monozonium_, _Dizonium_, _Trizonium_--represent +these three different stages, with one, two, or three girdles. These three +genera constitute the first subfamily, Haplozonaria (with one single system +of girdles); all three girdles lie in the surface of a simple +lentelliptical cortical shell. + +From this first subfamily the other two subfamilies of Pylonida must be +derived, by repetition of the same characteristic process of growth. In the +Diplozonaria a second system of girdles has been developed, constituting a +second (outer) cortical shell of lentelliptical form, concentric with the +first. Also in this second system the transverse girdle is first developed, +secondly the lateral girdle, thirdly the sagittal girdle. The three genera +_Amphipyle_, _Tetrapyle_ (with _Octopyle_), and _Pylonium_ represent these +three different stages of growth. + +Commonly the growth of the Pylonida stops with the completion of the second +system but sometimes the same process is once repeated and a third system +of girdles is formed, constituting a third lentelliptical shell; in this +case also the succession of the three latticed girdles is the same; firstly +the (third) transverse girdle is formed, secondly the (third) lateral +girdle, and thirdly the (third) sagittal girdle. Each of these three +girdles of the third system encloses concentrically the corresponding +girdles of the second and first system. The three corresponding genera of +this third subfamily (Triplozonaria) are _Amphipylonium_, _Tetrapylonium_, +and _Pylozonium_. But in general this highest number of girdles (nine) is +very seldom reached; commonly the growth of the Pylonida stops with five +girdles (_Tetrapyle_ and _Octopyle_). More than nine girdles I have never +observed, though there remains the possibility of the apposition of a +fourth system owing to the peculiar imperfect character of the growth +itself. + +The central or primordial chamber of the shell, with which in all Pylonida +the shell-building commences, is a quite simple, very small fenestrated +shell. Commonly one sees on the surface only five to ten small pores (three +to four on the diameter). Its form seems to be sometimes spherical, +sometimes elongated, ellipsoidal or probably lentelliptical. It may be +originally a small _Cenolarcus_. This simple central chamber, the true +"medullary shell" of the small Haplozonaria, is quite different from the +medullary shell of the larger Diplozonaria, and particularly of the +well-known _Tetrapyle_. The former observers, J. Mueller as well as R. +Hertwig, have described in these forms also the medullary shell as a simple +spherical or oblong body. But a careful {630}comparison of many hundred +specimens of them and of their dimensions, has convinced me that this was +an error, and that the small spherical or elliptical medullary shell of +_Tetrapyle_ and the other Diplozonaria possesses already the same complex +structure, composed of a system of three girdles, as _Trizonium_ and +_Larnacilla_. Whilst in the Haplozonaria probably the simple central +chamber only represents the medullary shell (enclosed in the central +capsule), and the first system of girdles (complete in _Trizonium_) the +external cortical shell, with the progressive growth this latter becomes +enclosed in the central capsule and so constitutes the "trizonal medullary +shell" of the Diplozonaria and Triplozonaria. + +A very difficult matter is the mode of connection between the cortical and +medullary shell. In most of the Pylonida it seems that the first or +transverse girdle (in each system) is produced by the formation of two +lateral wings or chambers (one on each side of the medullary shell), so +that each wing (or half girdle) represents a short and wide, nearly +cylindrical tube, the axis of which (with free openings on both poles) is +parallel to the principal axis of the medullary shell. In this case +(probably the ordinary one) both principal faces of the medullary shell +itself (dorsal and ventral face) constitute the middle part of the first +girdle whilst its lateral parts are formed by the wings (comparable to the +lateral chambers of _Amphitholus_). + +In the second case (probably a much rarer one) there is a free ring-shaped +space between the medullary shell and the first (transverse) girdle, and +both are connected by a small number of very short and small radial beams +(R. Hertwig, _loc. cit._, p. 52, line 19 to 21 from above). This mode of +connection would be the same as is common between the concentric shells of +the #Sphaeroidea# and #Prunoidea#. The distinction between these two +different modes of connection is often very difficult. + +The second or lateral girdle is commonly not in direct connection with the +medullary shell, or only by some scattered radial beams (mainly in the +principal axis). This lateral guide arises by prolongation of both wings of +the transverse girdle in the lateral plane, so that from both sides (right +and left) they become united on the poles of the principal axis. The minor +axis of the elliptical lateral ring (thus formed) is therefore the major +axis of the foregoing (transverse) elliptical ring; the major axes of both +are perpendicular one to another. The major axis of the lateral ring is the +principal (or longitudinal) axis of the whole body. + +The third or sagittal girdle becomes developed from the second almost in +the same manner as the second from the first. On both poles of the +principal axis two latticed wings arise from the lateral girdle, growing +further in the direction of an elliptical ring, which represents the +perimeter of the sagittal plane or median plane. These wings are already +mentioned by J. Mueller as "prominent roofs, protecting the gates of the +_Tetrapyle_-shell." If these roofs grow towards the equatorial plane of the +shell and become united in pairs on the poles of the sagittal axis, the +third girdle becomes {631}complete. R. Hertwig supposes that the minor axis +of this sagittal girdle is constantly at the same time the major axis of +the lateral girdle, but this is not always the case. Very often the size of +both these girdles is nearly the same, or one is not much larger than the +other. In this case the principal axis of the body is the major axis of the +second as well as of the third girdle. + +The characteristic "gates" of the Pylonida, or the large wide openings in +their cortical shell, remaining between the crossed latticed girdles, are +in general roundish, sometimes nearly circular, commonly more elliptical, +kidney-shaped or semilunar, their special form varying much according to +the different form of the girdles. The narrowest part of each girdle, or +its "isthmus," in the case of the halves of the transverse girdle is +commonly at their origin from the medullary shell, in the case of the +halves of the lateral girdle at the poles of the principal axis, and in the +case of the halves of the sagittal girdle at the poles of the sagittal +axis. The number of the gates is quite constant in the different genera. If +only one girdle (the transverse) be developed, we find only two large +gates, between the two wings on the poles of the principal axis (in +_Monozonium_, _Amphipyle_, _Amphipylonium_). In all other cases there are +four gates (determining the original name "_Tetrapyle_"), as well if only +two or if all three girdles be completed. If two girdles be complete (in +_Dizonium_, _Tetrapyle_, _Tetrapylonium_) the four gates lie opposite in +pairs on the sagittal faces (two anterior and two posterior gates), and are +limited by the transverse and lateral girdles. If all three girdles be +complete (in _Trizonium_, _Pylonium_, _Pylozonium_) the four gates lie +opposite in pairs on the lateral faces (two dorsal and two ventral gates), +and are limited by the sagittal and the transverse girdles. If we turn the +shell through an angle of 90d, we have the same aspect as in the former +group. A sagittal septum sometimes becomes developed, beginning with two +polar beams, rising from the poles of the principal axis. If these polar +beams become branched and connected with the middle part of the lateral +girdle, we get a latticed vertical septum, which divides the four gates of +_Tetrapyle_ into eight gates, _Octopyle_. + +The lattice-work of the Pylonida is commonly very variable and irregular, +with roundish meshes of very unequal size, therefore without value in the +determination of the species. Commonly the outside of the shell is thorny, +and often distinguished by larger radial spines, symmetrically disposed. We +can separate these into two groups; "dimensive" spines, lying in one of the +three dimensive axes (principal, transverse, or sagittal), and "diagonal" +spines, lying crossed in pairs in diagonal axes. Among these latter eight +diagonal wing-spines, which arise from the lateral edges of the four gates, +are particularly remarkable; they are not only characteristic of _Tetrapyle +octacantha_, but also of a large number of other Pylonida, and form the +starting-point for many specific forms. + +The shell of the Pylonida is characterised by extraordinary variability and +great {632}inclination to individual abnormalities, formation of varieties +and transitions into other families, hence derived, as Larnacida, +Tholonida, Lithelida, &c. + +The central capsule in all Pylonida, in which I could observe it, was a +true lentellipsis (or a "triaxial ellipsoid" in the geometrical sense, with +the three unequal isopolar axes of the "rhombic octahedron"). In the living +Pylonida it is commonly coloured pink or scarlet. During growth its +dimensions are probably more or less changed, and perhaps the axes +alternate. Regarding the relation of the central capsule to the skeleton, +we can distinguish two different groups, quite as in the nearly allied +Larnacida. In the Haplozonaria (as also in the Larnacillida) the central +capsule encloses only the central chamber and is enveloped by the first +system of girdles, whereas in the Diplozonaria and Triplozonaria (as in the +Larnacalpida) that "trizonal shell" becomes enclosed (as the "medullary +shell") in the central capsule, which is now enveloped by the second system +of girdles as the "cortical shell." + +_Synopsis of the Genera of Pylonida._ + + ------------------------------------------------------------------------- + I. Subfamily Haplozonaria. + One system of girdles. Medullary shell simple, spherical or + lentelliptical; cortical shell simple, with one, two, or three + girdles. + ------------------------------------------------------------------------- + Cortical shell only with one latticed (transverse) + girdle, 279. _Monozonium_. + + Cortical shell with two perfect girdles (transverse + and lateral), 280. _Dizonium_. + + Cortical shell with three perfect girdles + (transverse, lateral, and sagittal), 281. _Trizonium_. + ------------------------------------------------------------------------- + II. Subfamily Diplozonaria. + Two systems of concentric girdles. Medullary shell trizonal, with + three perfect girdles; cortical shell simple, with one, two or three + girdles. + ------------------------------------------------------------------------- + Cortical shell only with one perfect (transverse) + girdle, 282. _Amphipyle_. + + Cortical shell with two { Four gates simple, 283. _Tetrapyle_. + perfect girdles (the { + transverse and lateral).{ Four gates bisected by + { a sagittal septum, 284. _Octopyle_. + + Cortical shell with three perfect girdles + (transverse, lateral, and sagittal), 285. _Pylonium_. + ------------------------------------------------------------------------- + III. Subfamily Triplozonaria. + Three systems of concentric girdles. Medullary shell trizonal, with + three perfect girdles, quite as the inner cortical shell; outer + cortical shell with one, two, or three girdles. + ------------------------------------------------------------------------- + Outer cortical shell (third system) only with one + perfect (transverse) girdle, 286. _Amphipylonium_. + + Outer cortical shell with two perfect girdles + (transverse and lateral), 287. _Tetrapylonium_. + + Outer cortical shell with three perfect girdles + (transverse, lateral, and sagittal), 288. _Pylozonium_. + + + +Subfamily 1. HAPLOZONARIA, Haeckel. + +_Definition._--#Pylonida# with one single system of fenestrated girdles +(with one, two, or three girdles, lying in one lentelliptical face). + + + +{633}Genus 279. _Monozonium_,[318] n. gen. + +_Definition._--#Pylonida# with simple, spherical or subspherical, central +chamber, surrounded by one single (transverse) latticed girdle. + +The genus _Monozonium_ is the most simple and primitive of all Pylonida, +and may be regarded as their common ancestral form; it may probably be +derived phylogenetically either directly from _Cenosphaera_ or from +_Lentellipsis_, either by apposition of two imperfect lateral chambers, or +by surrounding it with an equatorial latticed girdle. This transverse +girdle is composed of three parts, the central chamber and two lateral +wings, which represent two short hollow latticed tubes, the axes of which +are parallel to the principal axis. On both principal sides (on the +anterior and posterior faces) there are two large open gates as in +_Amphipyle_. If we imagine the openings of the tube-shaped lateral wings +closed by lattice-work, _Monozonium_ becomes transformed into _Tholartus_, +the most simple form of Tholonida. Probably in all Pylonida the ontogeny of +the shell begins with the formation of a _Monozonium_. + + + +Subgenus 1. _Monozonaris_, Haeckel. + +_Definition._--Shell smooth or rough, without radial spines or thorns. + + +1. _Monozonium primordiale_, n. sp. + +Central chamber of the shell spherical, smooth, with three to four pores on +the half equator. Both wings of the girdle of the same breadth, but of +twice the length of the central chamber, with three to four longitudinal +rows of pores. No radial spines. + +_Dimensions._--Diameter of the central chamber 0.02; breadth of the wings +0.02, length 0.04; pores and bars 0.003. + +_Habitat._--Pacific, central area, Station 271, surface. + + +2. _Monozonium alatum_, n. sp. (Pl. 9, fig. 1). + +Central chamber of the shell lentelliptical, smooth, one and a half times +as long as broad, with three to four pores on the half equator. Both wings +of the girdle twice as broad, and somewhat longer than the central chamber, +with five to six longitudinal rows of pores. No radial spines. + +_Dimensions._--Length of the central chamber 0.03, breadth 0.02; breadth of +the wings 0.04, length 0.05; pores and bars 0.004. + +_Habitat._--North Pacific, Station 241, surface. + +_Monozonium hartingii_ = _Haliomma amphiaspis_, Harting, 1863 (L. N. 18, p. +15, pl. 2, fig. 43). + + + +{634}Subgenus 2. _Monozonitis_, Haeckel. + +_Definition._--Shell with radial spines or thorns, symmetrically disposed. + + +3. _Monozonium pleurostylum_, n. sp. + +Central chamber spherical, smooth, with four to five pores on the half +equator. Both wings of the girdle of the same breadth, but somewhat longer +than the central chamber, with four to five longitudinal rows of pores. On +the poles of the lateral axis two opposite strong conical spines (one in +the middle of each wing). + +_Dimensions._--Diameter of the central chamber 0.025; breadth of the wings +0.025, length 0.03; pores and bars 0.005. + +_Habitat._--Pacific, central area, Station 265, surface. + + +4. _Monozonium amphistylum_, n. sp. + +Central chamber lentelliptical, one and a half times as long as broad, with +three to four pores on the half equator. Breadth and length of each wing +somewhat greater than that of the central chamber. On the latter two strong +conical spines, opposite on the poles of the principal or longitudinal +axis. + +_Dimensions._--Length of the central chamber 0.03, breadth 0.02; breadth of +the wings 0.025, length 0.04; pores and bars 0.004. + +_Habitat._--South Atlantic, Station 332, surface. + + +5. _Monozonium staurostylum_, n. sp. + +Central chamber lentelliptical, one and a third times as long as broad, +with four to five pores on the half equator. Both wings of the girdle have +the same breadth, but one and a half times the length of the central +chamber. Four conical radial spines, two opposite on the poles of the +lateral, two on the poles of the principal axis. + +_Dimensions._--Length of the central chamber 0.028, breadth 0.021; breadth +of the wings 0.02, length 0.04. + +_Habitat._--South Pacific, Station 295, surface. + + + +Genus 280. _Dizonium_,[319] n. gen. + +_Definition._--#Pylonida# with simple, spherical or subspherical, central +chamber, surrounded by two crossed latticed girdles, one smaller (primary) +transverse and one larger (secondary) lateral girdle. + +The genus _Dizonium_ differs from the preceding _Monozonium_ in the +possession of two crossed elliptical lattice-girdles. The smaller girdle, +immediately surrounding the {635}central chamber, is the transverse girdle +(the single girdle of _Monozonium_). On the poles of its major axis (the +transverse axis) it is connected with the larger girdle, the elliptical +perimeter of which circumscribes the lateral plane. The minor axis of this +latter is the major axis of the former. Between the two crossed girdles +remain four larger openings or gates, quite as in _Tetrapyle_. But whilst +in _Tetrapyle_ the enclosed medullary shell is a trizonal +_Larnacilla_-shell, here in _Dizonium_ it is a simple spherical or +lentelliptical chamber. + + + +Subgenus 1. _Dizonaris_, Haeckel. + +_Definition._--Shell smooth or rough, without radial spines or thorns. + + +1. _Dizonium circulare_, n. sp. + +Central chamber of the shell spherical, smooth, with four to five pores on +the half equator. Lateral girdle circular, three times as broad as the +former. Four gates semilunar, twice as broad as high. No radial spines. + +_Dimensions._--Diameter of the central chamber 0.02, of the lateral girdle +0.06; height of the gates 0.02, breadth 0.04. + +_Habitat._--Pacific, central area, Station 274, surface. + + +2. _Dizonium ellipticum_, n. sp. + +Central chamber of the shell elliptical, smooth, with three to four pores +on the half equator. Lateral girdle elliptical, three times as long and +broad as the central chamber. Four gates kidney-shaped, twice as broad as +high. No radial spines. + +_Dimensions._--Length of the central chamber 0.03, breadth 0.02; length of +the lateral girdle 0.09, breadth 0.06; height of the gates 0.02, breadth +0.038. + +_Habitat._--South Pacific, Station 288, surface. + + +3. _Dizonium transversum_, n. sp. + +Central chamber of the shell spherical, rough, with five to six pores on +the half equator. Lateral girdle transverse-elliptical, so that its longer +axis corresponds to the lateral axis of the transverse girdle, and equals +four times the diameter of the central chamber. Four gates kidney-shaped, +four times as broad as high. No radial spines. + +_Dimensions._--Diameter of the central chamber 0.02; length of the lateral +girdle 0.05, breadth 0.08; height of the gates 0.01, breadth 0.04. + +_Habitat._--Pacific, central area, Station 274, depth 2750 fathoms. + + + +{636}Subgenus 2. _Dizonitis_, Haeckel. + +_Definition._--Shell with radial spines or thorns, symmetrically disposed. + + +4. _Dizonium pleuracanthum_, n. sp. (Pl. 9, fig. 2). + +Central chamber of the shell nearly spherical, smooth. Lateral girdle +elliptical, one and a third times as long as broad, three times as long as +the central chamber. Four gates transverse-elliptical, one and a half times +as broad as high. Two conical spines, opposite on the poles of the lateral +axis. + +_Dimensions._--Diameter of the central chamber 0.03; length of the lateral +girdle 0.1, breadth 0.075; height of the gates 0.026, breadth 0.04. + +_Habitat._--Western Tropical Pacific, Station 224, depth 1850 fathoms. + + +5. _Dizonium amphacanthum_, n. sp. + +Central chamber elliptical. Lateral girdle elliptical, twice as long as +broad. Four gates heart-shaped, about as high as broad. Two conical +spines, opposite on the poles of the principal axis. + +_Dimensions._--Length of the central chamber 0.03, breadth 0.02; length of +the lateral girdle 0.1, breadth 0.05; height and breadth of the gates 0.03. + +_Habitat._--Pacific, central area, Station 270, depth 2925 fathoms. + + +6. _Dizonium stauracanthum_, n. sp. (Pl. 9, fig. 3). + +Central chamber spherical. Lateral girdle elliptical, one and a third times +as long as broad. Four gates elliptical, one and a half times as broad as +high, halved by an axial beam (as in _Octopyle_). Four conical radial +spines opposite in pairs, two on the poles of the principal, two on the +poles of the transverse axis. + +_Dimensions._--Diameter of the central chamber 0.025; length of the lateral +girdle 0.09, breadth 0.06; height of the gates 0.024, breadth 0.036. + +_Habitat._--South Atlantic, Station 332, depth 2200 fathoms. + + +7. _Dizonium octacanthum_, n. sp. + +Central chamber spherical. Lateral girdle elliptical, one and a half times +as long as broad. Four gates kidney-shaped, twice as broad as high. Eight +radial spines, opposite in pairs in two crossed diagonal planes. + +_Dimensions._--Diameter of the central chamber 0.02; length of the lateral +girdle 0.075, breadth 0.05; height of the gates 0.02, breadth 0.04. + +_Habitat._--Pacific, central area, Station 272, surface. + + + +{637}Genus 281. _Trizonium_,[320] n. gen. + +_Definition._--#Pylonida# with simple, spherical or subspherical, central +chamber, surrounded by three latticed girdles, one smaller (primary) +transverse, one larger (secondary) lateral, and one (tertiary) sagittal +girdle. + +The genus _Trizonium_ represents the most highly developed form of the +Haplozonaria, with three complete elliptical latticed girdles, crossed at +right angles and lying in the perimeter of the three dimensive planes. +Commonly the first (transverse) girdle is the smallest, immediately +connected with the spherical or lentelliptical central chamber. The minor +axis of the second (lateral) girdle is identical with the major axis of the +first girdle. The third (sagittal) girdle is either larger than both +others, or intermediate between them. If the four gates between the girdles +become afterwards closed by lattice-work, the "trizonal shell" of +_Trizonium_ passes over into the typical _Larnacilla_, the ancestral form +of a great many #Larcoidea#. + + + +Subgenus 1. _Trizonaris_, Haeckel. + +_Definition._--Shell smooth or rough, without radial spines or thorns. + + +1. _Trizonium tricinctum_, n. sp. (Pl. 9, fig. 4). + +Central chamber of the shell elliptical. Lateral girdle elliptical, one and +a half times as long as broad. Four gates kidney-shaped, one and a half +times as broad as high. Ten to eleven pores on the half equator, fourteen +to sixteen on the half meridian of the lentelliptical shell. No radial +spines on the surface. + +_Dimensions._--Length of the central chamber 0.024, breadth 0.016; length +of the lateral girdle 0.075, breadth 0.05; height of the four gates 0.026, +breadth 0.04. + +_Habitat._--Pacific, central area, Station 272, depth 2600 fathoms. + + +2. _Trizonium constrictum_, n. sp. + +Central chamber elliptical. Lateral girdle violin-shaped, on both sides in +the middle constricted, twice as long as broad. Four gates +transverse-elliptical, twice as broad as high. Eight to nine pores on the +half equator, twelve to thirteen on the half meridian. No radial spines. + +_Dimensions._--Length of the central chamber 0.03, breadth 0.02; length of +the lateral girdle 0.09, breadth (in the middle) 0.045; height of the gates +0.022, breadth 0.044. + +_Habitat._--Pacific, central area, Station 263, surface. + + +{638}3. _Trizonium hexagonium_, n. sp. + +Central chamber spherical. Lateral girdle hexagonal, with parallel sides, +twice as long as broad. Four gates triangular, twice as broad as high. +Eleven to twelve pores on the half equator, sixteen to eighteen on the half +meridian. No radial spines. + +_Dimensions._--Diameter of the central chamber 0.025; length of the lateral +girdle 0.08, breadth 0.04; height of the gates 0.018, breadth 0.036. + +_Habitat._--Pacific, central area, Station 266, depth 2750 fathoms. + + +4. _Trizonium octogonium_, n. sp. + +Central chamber spherical. Lateral girdle octagonal; two lateral sides of +the octagon twice as long as the two polar sides and the four diagonal +sides. Four gates hexagonal, one and a half times as broad as high. Nine to +ten pores on the half equator, twelve to fourteen on the half meridian. No +radial spines. + +_Dimensions._--Diameter of the central chamber 0.02; length of the lateral +girdle 0.01, breadth 0.07; height of the gates 0.04, breadth 0.06. + +_Habitat._--Indian Ocean, surface; Ceylon, Haeckel. + + + +Subgenus 2. _Trizonitis_, Haeckel. + +_Definition._--Shell with radial spines or thorns, symmetrically disposed. + + +5. _Trizonium pleurobelonium_, n. sp. + +Central chamber spherical. Lateral girdle elliptical, one and a third times +as long as broad. Four gates nearly circular. Ten to eleven pores on the +half equator, fifteen to sixteen on the half meridian. Two opposite conical +spines on the poles of the lateral axis. + +_Dimensions._--Diameter of the central chamber 0.02; length of the lateral +girdle 0.08, breadth 0.06; height and breadth of the gates 0.025. + +_Habitat._--South Atlantic, off Buenos Ayres, Station 323, depth 1900 +fathoms. + + +6. _Trizonium amphibelonium_, n. sp. + + ? _Echinosphaera datura_, R. Hertwig (partim), 1879, Organismus d. + Radiol., p. 54, Taf. iv. figs. 8, 8_a_. + +Central chamber lentelliptical. Lateral girdle lanceolate, nearly one and a +half times as long as broad. Four gates subtriangular. Eight to nine pores +on the half equator, ten to twelve on the half meridian. Two opposite thin +and long spines on the poles of the principal axis, numerous shorter radial +spines on the whole surface. Possibly this species is identical with one of +the three different #Larcoidea# which R. Hertwig has described as +_Echinosphaera datura_. His fig. 8, Taf. iv., would be the aspect from the +sagittal girdle. + +{639}_Dimensions._--Length of the central chamber 0.04, breadth 0.025; +length of the lateral girdle 0.11, breadth 0.08; height of the gates 0.03, +breadth 0.04. + +_Habitat._--Mediterranean (Genoa), Haeckel, (Messina), R. Hertwig, surface; +Tropical Atlantic, Station 348, surface. + + +7. _Trizonium staurobelonium_, n. sp. + +Central chamber spherical, with two opposite polar beams. Lateral girdle +elliptical, one and a half times as long as broad. Four gates +transverse-elliptical, half as high as broad. Ten to eleven pores on the +half equator, fourteen to fifteen on the half meridian. Four conical radial +spines, two on the poles of the lateral, two on the poles of the principal +axis. + +_Dimensions._--Diameter of the central chamber 0.02; length of the lateral +girdle 0.075, breadth 0.05; height of the gates 0.014, breadth 0.028. + +_Habitat._--North Pacific, Station 241, depth 2300 fathoms. + + +8. _Trizonium hexabelonium_, n. sp. + +Central chamber elliptical. Lateral girdle hexagonal, one and a half times +as long as broad. Four gates rhombic, two-thirds as high as broad. Eight to +nine pores on the half equator, twelve to thirteen on the half meridian. +Six radial spines in the lateral plane, opposite in pairs on the six +corners of the lateral girdle (two principal and four diagonal). + +_Dimensions._--Length of the central chamber 0.024, breadth 0.018; length +of the lateral girdle 0.06, breadth 0.04; height of the gates 0.02, breadth +0.03. + +_Habitat._--Pacific, central area, Station 263, depth 2650 fathoms. + + +9. _Trizonium octobelonium_, n. sp. + +Central chamber elliptical. Lateral girdle hexagonal, one and one-third +times as long as broad. Four gates kidney-shaped or nearly rhombic, twice +as broad as high. Eleven to twelve pores on the half equator, sixteen to +seventeen on the half meridian. Eight radial spines, opposite in pairs in +two crossed diagonal planes. (An intermediate stage between _Dizonium +octacanthum_ and _Amphipyle octostyle_.) + +_Dimensions._--Length of the central chamber 0.03, breadth 0.024; length of +the lateral girdle 0.09, breadth 0.07; height of the gates 0.025, breadth +0.05. + +_Habitat._--Indian Ocean, Madagascar, Rabbe, surface. + + +10. _Trizonium decabelonium_, n. sp. + +Central chamber elliptical. Lateral girdle hexagonal, one and a half times +as long as broad. Four gates rhombic, twice as broad as high. Twelve to +thirteen pores on the half equator, seventeen to eighteen on the half +meridian. Ten radial spines, two opposite on the two poles of the principal +axis, eight others opposite in pairs in two crossed diagonal planes. + +{640}_Dimensions._--Length of the central chamber 0.04, breadth 0.03; +length of the lateral girdle 0.12, breadth 0.08; height of the gates 0.03, +breadth 0.06. + +_Habitat._--North Atlantic, Station 353, surface. + + +11. _Trizonium dodecabelos_, n. sp. + +Central chamber spherical. Lateral girdle octagonal, nearly twice an long +as broad. Four gates hexagonal, one and a half times as broad as high. Nine +to ten pores on the half equator, fifteen to sixteen on the half meridian. +Twelve radial spines, four in the lateral plane, in pairs on both sides of +the poles of the principal axis, eight others opposite in pairs in two +crossed diagonal axes. + +_Dimensions._--Diameter of the central chamber 0.025; length of the lateral +girdle 0.1, breadth 0.06; height of the gates 0.033, breadth 0.05. + +_Habitat._--Pacific, central area, Station 272, surface. + + + +Subfamily 2. DIPLOZONARIA, Haeckel. + +_Definition._--#Pylonida# with two concentric systems of fenestrated +girdles, lying in two concentric lentelliptical faces (every one system +with one to three girdles, lying in one lentelliptical face). + + + +Genus 282. _Amphipyle_,[321] Haeckel, 1881, Prodromus, p. 463. + +_Definition._--#Pylonida# with trizonal lentelliptical medullary shell, +surrounded by one single (transverse) latticed cortical girdle. + +The genus _Amphipyle_ opens the large series of Diplozonaria, comprising +all Pylonida, the shell of which is composed of two concentric systems of +latticed girdles; the first system constituting the characteristic +"trizonal medullary shell" or "_Larnacilla_-shell;" the second system +composed of one to three girdles of the second order. The first system lies +inside, the second outside the central capsule. In _Amphipyle_ only the +first (transverse) girdle of the second system becomes developed, and +therefore on both poles of the principal axis are two large open gates. +_Amphipyle_ repeats the two-winged form of _Monozonium_; but whilst the +medullary shell in this latter is a simple central chamber, it is here a +trizonal _Larnacilla_-shell. + + + +Subgenus 1. _Amphipylissa_, Haeckel. + +_Definition._--Cortical shell smooth or thorny, but without large, +symmetrically disposed spines. + + +{641}1. _Amphipyle aceros_, n. sp. + +Cortical shell quite smooth, without any spines or thorns. Both lateral +wings (or opposite half girdles) semilunar, with convex lateral crest, +three times as long as broad; twice as broad as the trizonal lentelliptical +medullary shell. + +_Dimensions._--Length of the medullary shell 0.05, breadth 0.03; length of +each lateral wing (or principal dimension of the latticed girdle) 0.18, +breadth of it (or transverse dimension of each girdle-tube) 0.06. + +_Habitat._--Pacific, central area, Station 271, depth 2425 fathoms. + + +2. _Amphipyle stenoptera_, n. sp. + +Cortical shell smooth, without spines. Both lateral wings of the same +breadth as the lentelliptical medullary shell, but five times as long as +broad, prolonged on both ends into cylindrical latticed tubes, with +rectilinear lateral crest. + +_Dimensions._--Length of the medullary shell 0.06, breadth 0.04; length of +each cylindrical lateral wing 0.2, breadth 0.04. + +_Habitat._--South Atlantic, off Ascension Island, Station 343, surface. + + +3. _Amphipyle platyptera_, n. sp. + +Cortical shell thorny, but without larger spines. Both lateral wings nearly +triangular, very broad and short, four times as broad as the medullary +shell between them, and only twice as long as broad, with rectilinear +lateral crest. + +_Dimensions._--Length of the medullary shell 0.05, breadth 0.25; length of +each lateral wing 0.18, breadth 0.09. + +_Habitat._--Indian Ocean, Ceylon, Haeckel, surface. + + + +Subgenus 2. _Amphipylura_, Haeckel. + +_Definition._--Cortical shell armed with large, symmetrically disposed +spines. + + +4. _Amphipyle amphiceros_, n. sp. + +Cortical shell with two conical spines on the poles of the longitudinal +axis (of the lentelliptical medullary shell), without other large spines, +but with small thorns on the surface; two to three longitudinal rows of +irregular, roundish pores on each half wing of the cortical girdle. + +_Dimensions._--Length of the medullary shell (or principal axis) 0.06, +breadth (or transverse axis) 0.04; length of each lateral wing 0.2, breadth +of it 0.05. + +_Habitat._--Western Tropical Pacific, Station 222, surface. + + +{642}5. _Amphipyle tetraceros_, n. sp. (Pl. 9, fig. 5). + +Cortical shell with smooth surface, and with four strong conical spines in +the lateral plane, opposite in pairs on the ends of the concave lateral +crests (one pair on the end-points of the lateral line of each wing); four +to five longitudinal rows of irregular, roundish pores on each half wing of +the cortical girdle. Surface of the medullary shell spiny. + +_Dimensions._--Length of the medullary shell 0.08, breadth of the same +0.05; length of each lateral wing 0.16, breadth 0.04. + +_Habitat._--Pacific, central area, Station 271, surface. + + +6. _Amphipyle stauroceros_, n. sp. + +Cortical shell with four strong conical spines, two on the poles of the +longitudinal axis, two opposite on the poles of the transverse axis +(perpendicular to the former). Three to four longitudinal rows of +irregular, roundish pores on each half wing of the cortical girdle, about +six pores in the longest row. Lateral crest convex. + +_Dimensions._--Length of the medullary shell 0.05, breadth 0.03; length of +each lateral wing 0.15, breadth 0.08. + +_Habitat._--Pacific, central area, Station 268, depth 2900 fathoms. + + +7. _Amphipyle amphiptera_, n. sp. (Pl. 9, fig. 7). + +Cortical shell with six strong conical spines, lying in the lateral plane +in three parallel longitudinal lines; two on the poles of the longitudinal +axis, two others on the poles of the wing axes, which are parallel to the +former. Two to three longitudinal rows of irregular, roundish pores on each +half wing of the cortical girdle, about eight pores in the longest row. +Lateral crest convex, thorny. + +_Dimensions._--Length of the medullary shell 0.06, breadth 0.045; length of +each lateral wing 0.09, breadth 0.035. + +_Habitat._--Western Tropical Pacific, Station 224, surface. + + +8. _Amphipyle hexaceros_, n. sp. + +Cortical shell thorny, with six strong conical spines lying in the lateral +plane; two on the poles of the lateral axis (in the central point of each +wing), two on the end-points of the triangular crest of each wing (on both +poles of the longitudinal wing-axis). + +_Dimensions._--Length of the medullary shell 0.06, breadth 0.04; length of +each lateral wing 0.13, breadth 0.07. + +_Habitat._--South Pacific, Station 291, surface. + + +{643}9. _Amphipyle octoceros_, n. sp. + +Cortical shell thorny, with eight long radial spines, lying in two crossed +diagonal planes, opposite in pairs. These eight horns are the +prolongations of the anterior and posterior edges of each wing, on both +sides of its lateral plane; they are of great importance, as appearing (by +heredity) in many other Pylonida (_e.g._, in _Tetrapyle octacantha_). +Lateral crest of each wing without spines, slightly convex. + +_Dimensions._--Length of the medullary shell 0.07, breadth 0.05; length of +each lateral wing 0.15, breadth 0.06. + +_Habitat._--Pacific, central area, Stations 270 to 274, surface. + + +10. _Amphipyle cladoceros_, n. sp. + +Cortical shell spiny, with eight strong ramified radial spines, lying in +the same two crossed diagonal planes as in the preceding species. It +differs from this in the ramification of the eight horns, which bear six to +nine irregular lateral branches, partly simple, partly bifurcate. Lateral +crest of each wing spiny, convex. + +_Dimensions._--Length of the medullary shell 0.06, breadth 0.045; length of +each lateral wing (without spines) 0.2, breadth 0.09. + +_Habitat._--Indian Ocean, surface, Madagascar, Rabbe. + + +11. _Amphipyle decaceros_, n. sp. + +Cortical shell spiny, with ten strong conical spines; eight lying in two +crossed diagonal planes, in the same disposition (opposite in pairs) as in +both preceding species; two others opposite on the poles of the principal +axis, arising from both poles of the medullary shell (columella-beams). +Spiny crest of the wings convex, semilunar. + +_Dimensions._--Length of the medullary shell 0.04, breadth 0.03; length of +each lateral wing 0.12, breadth 0.04. + +_Habitat._--North Atlantic, Station 354, surface. + + +12. _Amphipyle dodecaceros_, n. sp. + +Cortical shell thorny, with twelve large cylindrical spines; eight lying in +two crossed diagonal planes, in the same disposition (opposite in pairs) as +in the three preceding species; four others crossed at right angles in the +lateral plane, two opposite on the poles of the principal, two on the poles +of the lateral axis (the latter shorter). Both lateral wings nearly +rhombic. + +_Dimensions._--Length of the medullary shell 0.06, breadth 0.04; length of +the lateral wings 0.15, breadth 0.05. + +_Habitat._--South Atlantic, coast of Brazil, Rabbe, surface. + + +{644}13. _Amphipyle callizona_, n. sp. (Pl. 9, fig. 6). + +Cortical shell smooth, with sixteen strong and short conical spines, lying +opposite in pairs in two crossed diagonal planes; each lateral wing +four-sided prismatic, its lateral face concave, both ends truncated, and +each end provided with four divergent spines. Length of the wings somewhat +greater, but breadth smaller, than that of the medullary shell. + +_Dimensions._--Length of the medullary shell 0.07, breadth 0.05; length of +the lateral wings 0.09, breadth 0.03. + +_Habitat._--Western Tropical Pacific, Station 225, depth 4475 fathoms. + + + +Genus 283. _Tetrapyle_,[322] J. Mueller, 1858, Monatsber. d. k. preuss. +Akad. d. Wiss. Berlin, p. 154. + +_Definition._--#Pylonida# with trizonal lentelliptical medullary shell, +surrounded by two crossed latticed cortical girdles, one smaller (primary) +transverse, and one larger (secondary) lateral girdle. Four gates between +the two cortical girdles simple, without a sagittal septum. + +The genus _Tetrapyle_, till 1881 the only known genus of the whole family, +was founded by Johannes Mueller in 1858, and clearly illustrated by the +Mediterranean (and common cosmopolitan) _Tetrapyle octacantha_, hitherto +the best known type of this family. Afterwards (1860, Monatsber. d. k. +preuss. Akad. d. Wiss. Berlin, p. 832) Ehrenberg founded the genus +_Schizomma_ for a nearly allied form, which exhibits only slight specific +differences (compare my Monograph, 1862, p. 434). Some good remarks on the +structure of this typical genus and its relations to other Pylonida are to +be found in Richard Hertwig's Organismus, &c., 1879, p. 52, but the true +trizonal structure of the medullary shell in this genus was not recognised +by him, so that his description agrees more with _Dizonium_. We confine +here the genus _Tetrapyle_ to those Pylonida for which _Tetrapyle +octacantha_ of J. Mueller remains the determining type; the cortical shell +is composed only of two perfect lattice-girdles (the transverse and +lateral), between which four wide gates remain open. This structure is +similar to that of _Dizonium_; but whilst here the medullary shell is a +simple central chamber, in _Tetrapyle_ it is a complete trizonal or +_Larnacilla_-shell. + + + +Subgenus 1. _Tetrapylissa_, Haeckel. + +_Definition._--Cortical shell smooth or thorny, but without large, +symmetrically disposed spines. + + +{645}1. _Tetrapyle circularis_, n. sp. (Pl. 9, fig. 8). + +Cortical shell rough, without radial spines. Lateral girdle circular, +therefore the longitudinal axis is equal to the transverse. Four gates +kidney-shaped, twice as broad as high. In each half wing of the transverse +girdle six to seven longitudinal rows of irregular, roundish pores. + +_Dimensions._--Medullary shell 0.05 long, 0.04 broad; cortical shell 0.15 +long and broad; gates 0.04 high, 0.08 broad. + +_Habitat._--Pacific, central area, Station 263, surface. + + +2. _Tetrapyle circopyle_, n. sp. + +Cortical shell smooth, without radial spines. Lateral girdle elliptical, +one and a half times as long as broad. Four gates nearly circular. On each +half wing of the transverse girdle four to five rows of subregular, +circular pores. (Similar to _Tetrapyle pleuracantha_, Pl. 9, fig. 9, but +without lateral spines.) + +_Dimensions._--Medullary shell 0.04 long, 0.03 broad; cortical shell 0.16 +long, 0.11 broad; gates 0.05 high and broad. + +_Habitat._--Pacific, central area, Station 268, depth 2900 fathoms. + + +3. _Tetrapyle quadriloba_, Haeckel. + + _Tetrapyle quadriloba_, Haeckel, 1862, Monogr. d. Radiol., p. 436. + + _Schizomma quadrilobum_, Ehrenberg, 1860, Monatsber. d. k. preuss. Akad. + d. Wiss. Berlin, p. 815; Abhandl. d. k. Akad. d. Wiss. Berlin, 1872, Taf. + x. figs. 12-14. + +Cortical shell thorny, without regular, radial spines. Lateral girdle +elliptical, one and a half times as long as broad. Four gates nearly +circular. On each half wing of the transverse girdle three to four rows of +irregular, roundish pores. + +_Dimensions._--Medullary shell 0.06 long, 0.04 broad; cortical shell 0.16 +long, 0.1 broad; diameter of the gates 0.05. + +_Habitat._--Cosmopolitan; Mediterranean, Atlantic, Indian Ocean, Pacific, +surface. + + +4. _Tetrapyle nephropyle_, n. sp. + +Cortical shell thorny, without radial spines. Lateral girdle elliptical, +one and a third times as long as broad. Four gates kidney-shaped, nearly +twice as broad as high, with two prominent polar spines on the poles of the +longitudinal axis of the medullary shell. On each half wing of the +transverse girdle three to four longitudinal rows of large roundish pores. + +_Dimensions._--Medullary shell 0.06 long, 0.04 broad; cortical shell 0.24 +long, 0.18 broad; gates 0.05 high, 0.08 broad. + +_Habitat._--Pacific, central area, Station 271, depth 2425 fathoms. + + +{646}5. _Tetrapyle cardiopyle_, n. sp. + +Cortical shell rough, without radial spines. Lateral girdle with hexagonal +contour, nearly cylindrical in the middle part, conical at both ends, twice +as long as broad. Four gates heart-shaped, about as high as broad. On each +half wing of the transverse girdle three to four longitudinal rows of +subregular, polygonal pores. + +_Dimensions._--Medullary shell 0.04 long, 0.02 broad; cortical shell 0.14 +long, 0.07 broad; gates 0.05 high and broad. + +_Habitat._--Eastern Tropical Atlantic, Station 348, depth (2450) fathoms. + + + +Subgenus 2. _Tetrapylura_, Haeckel. + +_Definition._--Cortical shell armed with large, symmetrically disposed +spines. + + +6. _Tetrapyle fusiformis_, n. sp. + +Cortical shell rough, with two strong conical spines on the poles of the +longitudinal axis. Lateral girdle spindle-shaped, one and a half times as +long as broad. Four gates kidney-shaped, twice as broad as high. On each +half wing of the transverse girdle four to five longitudinal rows of +irregular, roundish pores. + +_Dimensions._--Medullary shell 0.07 long, 0.05 broad; cortical shell 0.18 +long, 0.12 broad; gates 0.04 high, 0.08 broad. + +_Habitat._--Western Tropical Atlantic, Mexican Gulf Stream, depth 1500 +fathoms, Schaffner. + + +7. _Tetrapyle pleuracantha_, n. sp. (Pl. 9, fig. 9). + +Cortical shell rough, with two strong conical spines on the poles of the +transverse axis. Lateral girdle elliptical, one and half times as long as +broad. Four gates subcircular or nearly hexagonal, about as high as broad. +On each half wing of the transverse girdle three to four longitudinal rows +of very irregular pores. + +_Dimensions._--Medullary shell 0.045 long, 0.035 broad; cortical shell 0.16 +long, 0.11 broad; gates 0.045 high and broad. + +_Habitat._--Western Tropical Pacific, off New Guinea, Stations 222 to 224, +depths 1850 to 2450 fathoms. + + +8. _Tetrapyle transversa_, n. sp. + +Cortical shell thorny, with two strong conical lateral spines on the poles +of the transverse axis. Lateral girdle elliptical, only four-fifths as long +as broad. Four gates elliptical, twice as broad as high, with two prominent +spines on the poles of the longitudinal axis of the medullary shell. On +each half wing of the transverse girdle five to six longitudinal rows of +subregular, roundish pores. (Similar to _Octopyle transversa_, but without +sagittal septum and with stronger lateral spines.) + +{647}_Dimensions._--Medullary shell 0.05 long, 0.035 broad; cortical shell +0.12 long, 0.15 broad; gates 0.03 high, 0.06 broad. + +_Habitat._--Southern Pacific, Station 290, surface. + + +9. _Tetrapyle cruciata_, n. sp. + +Cortical shell smooth, with four strong radial spines, two on the poles of +the longitudinal axis, two on the poles of the transverse axis. Lateral +girdle nearly circular, quite as long as broad. Four gates kidney-shaped, +twice as broad as high. On each half wing of the transverse girdle five to +six rows of subregular, circular pores. + +_Dimensions._--Medullary shell 0.06 long, 0.05 broad; cortical shell 0.16 +long and broad; gates 0.05 high, 0.09 broad. + +_Habitat._--South Atlantic, Station 330, surface. + + +10. _Tetrapyle staurophora_, n. sp. + +Cortical shell thorny, with four strong radial spines, two on the poles of +the longitudinal axis, two on the poles of the transverse axis. Lateral +girdle elliptical, one and a half times as long as broad. Four gates nearly +hexagonal, quite as high as broad. On each half wing of the transverse +girdle three to four longitudinal rows of irregular, roundish pores. + +_Dimensions._--Medullary shell 0.06 long, 0.04 broad; cortical shell 0.18 +long, 0.12 broad; gates 0.08 high and broad. + +_Habitat._--Western Tropical Atlantic, coast of Brazil, Rabbe, surface. + + +11. _Tetrapyle quadricornis_, n. sp. + +Cortical shell thorny, with four strong horn-like curved spines, lying in +the lateral plane and converging in pairs towards the poles of the +transverse axis. Lateral girdle elliptical, one and a third times as long +as broad. Four gates kidney-shaped, twice as broad as high. On each half +wing of the transverse girdle four to five rows of irregular, roundish +pores. (May be only the young form of _Pylonium quadricorne_, Pl. 9, fig. +14.) + +_Dimensions._--Medullary shell 0.05 long, 0.04 broad; cortical shell 0.16 +long, 0.12 broad; gates 0.03 high, 0.07 broad. + +_Habitat._--Pacific, central area, Stations 270 to 274, surface. + + +12. _Tetrapyle tetracantha_, n. sp. + +Cortical shell thorny, with four strong radial spines lying in the lateral +plane and in pairs in its two crossed diagonal axes. Lateral girdle +elliptical, constricted in the middle, nearly twice as long as broad. Four +gates kidney-shaped, one and a half times as broad as high. On each half +wing of the transverse girdle three to four longitudinal rows of large, +irregular, roundish pores. {648}(Similar to _Tetrapylonium quadrangulare_, +Pl. 49, fig. 15, but without a sagittal girdle and with stronger lateral +spines.) + +_Dimensions._--Medullary shell 0.06 long, 0.04 broad; cortical shell 0.18 +long, 0.1 broad; gates 0.007 high, 0.01 broad. + +_Habitat._--North Atlantic, Canary Islands, Station 353, surface. + + +13. _Tetrapyle quadrigata_, n. sp. + +Cortical shell thorny, with four brush-like groups of radial spines on the +four diagonal corners of the lateral plane, opposite in pairs in diagonal +axes. Lateral girdle nearly square, somewhat broader than long. Four gates +kidney-shaped, twice as broad as high. On each half wing of the transverse +girdle five to six longitudinal rows of irregular, roundish pores. + +_Dimensions._--Medullary shell 0.06 long, 0.04 broad; cortical shell 0.14 +long, 0.15 broad; gates 0.03 high, 0.07 broad. + +_Habitat._--Pacific, central area, Station 270, surface. + + +14. _Tetrapyle octacantha_, J. Mueller. + + _Tetrapyle octacantha_, J. Mueller, 1858, Abhandl. d. k. Akad. d. Wiss. + Berlin, p. 33, Taf. ii. figs. 1-6. + + _Tetrapyle octacantha_, Haeckel, 1862, Monogr. d. Radiol., p. 435. + + _Tetrapyle octacantha_, R. Hertwig, 1879, Organismus d. Radiol., p. 52, + Taf. iv. fig. 7, Taf. vi. figs. 2, 5, 5_a._ + +Cortical shell thorny, with eight long and thin, cylindrical radial spines, +lying in two crossed diagonal planes, opposite in pairs. These eight +characteristic diagonal spines (or "angular spines") are the same as in +_Amphipyle octoceros_ and many other Pylonida, and arise as prolongations +of the proximal edges of the four gates (or of the lateral wings on the +eight points, where they are intersected by the edges of the lateral ring). +This cosmopolitan, widely distributed and very variable species was a long +time the only known species of all the Pylonida, and very accurately first +described (1858) by Johannes Mueller, afterwards (1879) by R. Hertwig. But +in the descriptions of these authors also some different species (such as +the following) may be confounded with the true typical _Tetrapyle +octacantha_. The four gates of this species are transverse-elliptical or +almost triangular, nearly twice as broad as high. + +_Dimensions._--Length of the medullary shell 0.04, breadth 0.03; length of +the cortical shell 0.18, breadth 0.13; height of the gates 0.05, breadth +0.08. + +_Habitat._--Cosmopolitan; very common in all warmer seas, Mediterranean, +Atlantic, Indian, Pacific, surface. + + +15. _Tetrapyle cladacantha_, n. sp. + +Cortical shell thorny, with eight strong ramified radial spines, lying +opposite in pairs in two crossed diagonal planes, as in the preceding +species. It differs from this by the peculiar ramification of the eight +spines, which bear two to eight simple or furcate lateral branches arising +under {649}right angles (already commencing in a transitional variety of +_Tetrapyle octacantha_, J. Mueller, _loc. cit._, Taf. ii. figs. 5, 6). Four +gates transverse-elliptical, one and a half times as broad as high. + +_Dimensions._--Medullary shell 0.05 long, 0.04 broad; cortical shell 0.16 +long, 0.13 broad; gates 0.05 high, 0.08 broad. + +_Habitat._--Mediterranean (Corfu), Haeckel, surface. + + +16. _Tetrapyle pluteus_, Haeckel. + + _Tetrapyle octacantha_, var., J. Mueller, 1858, Abhandl. d. k. Akad. d. + Wiss. Berlin, Taf. iii. figs. 7-12. + +Cortical shell thorny, with eight strong radial spines, lying opposite in +pairs, as in the two foregoing species. On the distal edge each of the four +triangular gates is protected by a prominent roof of lattice-work (or +"pluteus"), which arises from the distal part of the lateral girdle and +connects the two angular diagonal spines of each gate. Therefore the shell +assumes the characteristic form very well represented by J. Mueller in his +fig. 11 (seen from the lateral side) and fig. 7 (seen from the pole of the +principal axis). + +_Dimensions._--Medullary shell 0.04 long, 0.03 broad; cortical shell 0.15 +long, 0.11 broad; gates 0.045 high, 0.07 broad. + +_Habitat._--Mediterranean, Atlantic, Stations 348 to 353, &c., surface. + + +17. _Tetrapyle turrita_, n. sp. (Pl. 9, fig. 10). + +Cortical shell smooth, but with ten strong conical spines, two on the poles +of the principal axis, eight others symmetrically distributed on both sides +of the distal edge of the four roundish gates, and directed towards the +transverse axis. Lateral girdle lanceolate, twice as long as broad. + +_Dimensions._--Medullary shell 0.05 long, 0.04 broad; cortical shell 0.2 +long, 0.1 broad; gates 0.05 high, 0.07 broad. + +_Habitat._--Pacific, central area, Station 274, depth 2750 fathoms. + + +18. _Tetrapyle dodecaceros_, n. sp. + +Cortical shell thorny, with twelve stronger conical spines, eight diagonal +spines in two crossed planes (as in _Tetrapyle octacantha_), and four +others in the lateral plane, in pairs on both sides of a deep sagittal +constriction of the quadrangular lateral girdle. Four gates kidney-shaped, +twice as broad as high. On each half wing of the transverse girdle five to +six longitudinal rows of irregular, roundish pores. + +_Dimensions._--Medullary shell 0.06 long, 0.04 broad; cortical shell 0.18 +long, 0.14 broad; gates 0.04 high, 0.08 broad. + +_Habitat._--Pacific, central area, Station 271, depth 2425 fathoms. + + + +{650}Genus 284. _Octopyle_,[323] Haeckel, 1881, Prodromus, p. 464. + +_Definition._--#Pylonida# with trizonal lentelliptical medullary shell, +surrounded by two crossed, latticed, cortical girdles; one smaller +(primary) transverse, and one larger (secondary) lateral girdle. Four gates +between the two cortical girdles divided by a sagittal septum into eight +gates. + +The genus _Octopyle_ comprises those Pylonida which are distinguished from +the nearly allied _Tetrapyle_ by the development of a sagittal septum, +dividing the four gates of the latter into eight separate gates. The septum +begins with the formation of two axial rods or columellae, which afterwards +become branched; the branches communicating one with another and with the +middle parts of the lateral girdle (on the poles of the principal axis), +there is formed a latticed septum in the sagittal plane, which separates +more or less incompletely the right and left halves of the shell. The four +gates of _Tetrapyle_ become halved by this septum, and their number +doubled. + + + +Subgenus 1. _Octopylissa_, Haeckel. + +_Definition._--Cortical shell smooth or thorny, but without larger +symmetrically disposed spines. + + +1. _Octopyle ovulina_, n. sp. + +Cortical shell lentelliptical, smooth, without thorns. Lateral girdle +elliptical, one and a third times as long as broad. Transverse girdle +narrow, with two pores on the isthmus (or on the narrowest part of each +quadrant). Sagittal septum as long as the elliptical medullary shell. Eight +gates egg-shaped. + +_Dimensions._--Length of the medullary shell 0.05, breadth 0.035; length of +the cortical shell 0.16, breadth 0.12. + +_Habitat._--Pacific, central area, Station 274, surface. + + +2. _Octopyle quadrata_, n. sp. + +Cortical shell thorny, nearly square, of equal length and breadth. Lateral +girdle quadrangular, with rounded edges, of equal length and breadth. +Transverse girdle narrow, with three pores on the isthmus. Sagittal septum +of the same length as the subspherical medullary shell. Eight gates nearly +circular. + +_Dimensions._--Diameter of the medullary shell 0.04, of the cortical shell +0.14. + +_Habitat._--Northern Pacific, Station 244, depth 2900 fathoms. + + +{651}3. _Octopyle subglobosa_, n. sp. + +Cortical shell nearly spherical, thorny, of equal length and breadth. +Lateral girdle broad, nearly circular. Transverse girdle broad, with four +pores on the isthmus. Sagittal septum shorter than the subspherical +medullary shell. Eight gates egg-shaped. + +_Dimensions._--Diameter of the medullary shell 0.05, of the cortical shell +0.13. + +_Habitat._--Southern Pacific, Station 300, depth 1375 fathoms. + + +4. _Octopyle transversaria_, n. sp. + +Cortical shell thorny, transverse-elliptical. Lateral girdle very broad, +one and a third times as broad as long. Transverse girdle also very broad, +with five pores on the isthmus. Sagittal septum shorter than the elliptical +medullary shell. Eight gates small, roundish. + +_Dimensions._--Length of the medullary shell 0.05, breadth 0.04; length of +the cortical shell 0.11, breadth 0.15. + +_Habitat._--Western Tropical Pacific, Station 224, depth 1850 fathoms. + + + +Subgenus 2. _Octopylura_, Haeckel. + +_Definition._--Cortical shell armed with large, symmetrically disposed +spines. + + +5. _Octopyle amphistyle_, n. sp. + +Cortical shell smooth, nearly spindle-shaped, about twice as long as broad. +Transverse girdle broad, with four large pores on the isthmus. Lateral +girdle lanceolate. Sagittal septa about as long as the medullary shell, +prolonged at both poles of the principal axis into two opposite, strong, +angular spines. Eight gates obliquely quadrangular. + +_Dimensions._--Length of the medullary shell 0.07, breadth 0.05; length of +the cortical shell 0.2, breadth 0.12. + +_Habitat._--Pacific, central area, Station 272, depth 2600 fathoms. + + +6. _Octopyle staurostyle_, n. sp. + +Cortical shell nearly rhombic, smooth, one and a half times as long as +broad, with four strong, conical, radial spines, two on the poles of the +principal axis (as prolongations of the sagittal septa), two others on the +poles of the transverse axis. Transverse girdle narrow, with two pores on +the isthmus. Sagittal septa longer than the medullary shell. Eight gates +triangular. + +_Dimensions._--Length of the medullary shell 0.04, breadth 0.03; length of +the cortical shell 0.18, breadth 0.12. + +_Habitat._--Tropical Atlantic, Station 347, depth 2250 fathoms. + + +{652}7. _Octopyle tetrastyle_, n. sp. + +Cortical shell lentelliptical, with rough surface and four angular radial +spines in the lateral plane, opposite in pairs in two crossed diagonals. +Lateral girdle nearly rectangular (each angle with one spine), one and a +third times as long as broad. Sagittal septum longer than the hexagonal +medullary shell. Eight gates egg-shaped. + +_Dimensions._--Length of the medullary shell 0.05, breadth 0.03; length of +the cortical shell 0.16, breadth 0.12. + +_Habitat._--North Atlantic, Station 354, surface. + + +8. _Octopyle tetraptera_, n. sp. + +Cortical shell quadrangular, with thorny surface and four latticed +wing-like prolongations on the corners of the quadrangle, opposite in pairs +in two crossed diagonals, each wing supported by a strong radial spine. +Lateral girdle quadrangular, one and a half times as long as broad. On the +isthmus of the transverse girdle four pores. Sagittal septum longer than +the hexagonal medullary shell. Eight gates triangular. + +_Dimensions._--Length of the medullary shell 0.07, breadth 0.04; length of +the cortical shell 0.24, breadth 0.16. + +_Habitat._--Pacific, central area, Station 271, surface. + + +9. _Octopyle stenozona_, n. sp. (Pl. 9, fig. 11). + +Cortical shell quadrangular, with thorny surface, and four conical spines +in the lateral plane, on the points, where both cortical girdles are +crossed. Lateral girdle very narrow, nearly square, with rounded corners, +of equal length and breadth. On the isthmus of the narrow transverse girdle +only one pore. Sagittal septum of the same length as the subspherical +medullary shell. Eight gates irregular roundish or nearly circular. + +_Dimensions._--Diameter of the medullary shell 0.04, of the cortical shell +0.14. + +_Habitat._--Tropical Atlantic, Station 338, depth 1990 fathoms. + + +10. _Octopyle euryzona_, n. sp. + +Cortical shell nearly quadrangular, very thorny, with four bunches of +stronger radial spines on the four corners. Lateral girdle broad, with +rounded edges of the quadrangle, little longer than broad. On the isthmus +of the broad transverse girdle four pores. Sagittal septum of the same +length as the elliptical medullary shell, with many radial beams. Eight +gates nearly square. + +_Dimensions._--Length of the medullary shell 0.05, breadth 0.035; length of +the cortical shell 0.16, breadth 0.14. + +_Habitat._--Southern Atlantic, Station 332, depth 2200 fathoms. + + +{653}11. _Octopyle hexastyle_, n. sp. + +Cortical shell nearly rectangular, thorny, with six strong radial spines in +the lateral plane, two opposite on the poles of the principal axis +(prolongations of the principal beam at the sagittal septum), four others +on the truncate corners of the quadrangular lateral girdle, which is one +and a half times as long as broad. On the isthmus of the broad transverse +girdle three pores. Sagittal septum longer than the hexagonal medullary +shell. Eight egg-shaped gates. + +_Dimensions._--Length of the medullary shell 0.05, breadth 0.04; length of +the cortical shell 0.18, breadth 0.12. + +_Habitat._--Northern Atlantic, surface; Canary Islands, Station 9, depth +3150 fathoms. + + +12. _Octopyle sexangulata_, n. sp. (Pl. 9, fig. 12). + +Cortical shell thorny, hexagonal, with six strong conical radial spines on +the six corners of the lateral girdle, lying in the lateral plane, two +opposite on the poles of the transverse axis, four others in pairs on both +sides of the annular sagittal constriction, which is only twice as long as +the elliptical medullary shell. Transverse girdle broad, with five pores on +the isthmus. Eight gates roundish, smaller than the medullary shell. + +_Dimensions._--Length of the medullary shell 0.045, breadth 0.035; length +of the cortical shell 0.11, breadth 0.13. + +_Habitat._--Pacific, central area, Station 270, surface. + + +13. _Octopyle octostyle_, n. sp. + +Cortical shell elliptical, thorny, with eight long cylindrical radial +spines, lying in two crossed diagonal planes, opposite in pairs, quite as +in the nearly related _Tetrapyle octacantha_. It differs from this species +by the perfect, latticed, vertical sagittal septum, which divides every +gate into two triangular halves. Lateral girdle elliptical, one and a third +times as long as broad. Transverse girdle on the isthmus with three pores. +Septum longer than the elliptical medullary shell. + +_Dimensions._--Length of the medullary shell 0.06, breadth 0.045; length of +the cortical shell 0.16, breadth 0.12. + +_Habitat._--South Pacific, Station 288, surface. + + +14. _Octopyle obtecta_, n. sp. + +Cortical shell quadrangular, thorny, with eight strong diagonal spines, +lying in two crossed planes, and arising from the proximal edges of the +gates in the same way as in the foregoing species. It differs from this by +four prominent latticed roofs, which arise from the distal edge of the +gates and connect the diagonal spines of one gate. _Octopyle obtecta_ bears +therefore the same relation to _Octopyle octostyle_ that _Tetrapyle +pluteus_ does to _Tetrapyle octacantha_. + +_Dimensions._--Length of the medullary shell 0.055, breadth 0.04; length of +the cortical shell 0.16, breadth 0.12. + +_Habitat._--Indian Ocean, surface, Madagascar, Rabbe. + + +{654}15. _Octopyle decastyle_, n. sp. (Pl. 9, fig. 13). + +Cortical shell thorny, nearly quadrangular, with ten stronger radial +spines, two opposite on the poles of the principal axis (as prolongations +of the axial beams), eight others opposite in pairs in two diagonal planes +(as in the foregoing species). Lateral girdle nearly square, with slightly +convex lateral faces, slightly concave principal faces. Transverse girdle +broad, with four pores on the isthmus. Sagittal septum of the same length +as the hexagonal medullary shell. Eight gates elliptical or irregular +roundish. + +_Dimensions._--Length of the medullary shell 0.05, breadth 0.032; diameter +of the cortical shell 0.15. + +_Habitat._--Western Tropical Pacific, Station 224, depth 1850 fathoms. + + + +Genus 285. _Pylonium_,[324] Haeckel, 1881, Prodromus, p. 464. + +_Definition._--#Pylonida# with trizonal lentelliptical medullary shell +surrounded by three crossed latticed cortical girdles, one smaller +(primary) transverse, one larger (secondary) lateral, and one (tertiary) +sagittal girdle. + +The genus _Pylonium_ is the most highly developed among the Diplozonaria, +with six complete latticed girdles, three on the medullary shell, three on +the cortical shell, the latter corresponding to the former. In each of the +two systems the transverse girdle is smaller than the lateral; the sagittal +girdle may be smaller or larger than the lateral girdle. _Pylonium_ repeats +the typical form of _Trizonium_; but whilst in this latter the medullary +centre of the shell is a simple spherical chamber, here in _Pylonium_ it is +a true trizonal or _Larnacilla_-shaped medullary shell. + + + +Subgenus 1. _Pylonissa_, Haeckel. + +_Definition._--Cortical shell smooth or thorny, but without large, +symmetrically disposed spines. + + +1. _Pylonium circozonium_, n. sp. + +Cortical shell thorny, without radial spines; all its three girdles nearly +of the same size, subcircular, very narrow, only with one to two rows of +pores. Four gates subcircular. + +_Dimensions._--Principal axis 0.12, transverse axis 0.11; diameter of the +subspherical medullary shell 0.05. + +_Habitat._--North Pacific, Station 244, depth 2900 fathoms. + + +{655}2. _Pylonium hexazonium_, n. sp. + +Cortical shell smooth, without symmetrical radial spines. Transverse girdle +elliptical, one and a half times as long as broad. Lateral and sagittal +girdles nearly circular. Four gates egg-shaped. + +_Dimensions._--Principal axis 0.16, transverse axis 0.15; diameter of the +subspherical medullary shell 0.04. + +_Habitat._--South Pacific, Station 295, depth 1500 fathoms. + + +3. _Pylonium nephropylium_, n. sp. + +Cortical shell thorny, without radial spines. All its three girdles +elliptical, one and a third times as long as broad. Four gates +kidney-shaped, nearly twice as broad as high. + +_Dimensions._--Principal axis 0.17, transverse axis 0.13; length of the +lentelliptical medullary shell 0.04, breadth 0.03. + +_Habitat._--Pacific, central area, Station 273, depth 2350 fathoms. + + + +Subgenus 2. _Pylonura_, Haeckel. + +_Definition._--Cortical shell armed with large, symmetrically disposed +spines. + + +4. _Pylonium quadricorne_, n. sp. (Pl. 9, fig. 14). + +Cortical shell thorny, with four strong horn-like curved spines in the +lateral plane. All its three girdles elliptical, one and a third times as +long as broad. Four gates kidney-shaped, twice as broad as high. (This +species is a further developmental stage of _Tetrapyle quadricornis_, with +perfect sagittal girdle.) + +_Dimensions._--Principal axis 0.16, transverse axis 0.12; length of the +medullary shell 0.05, breadth 0.04. + +_Habitat._--Pacific, central area, Stations 270 to 274, surface; Indian +Ocean, Madagascar, Rabbe, surface. + + +5. _Pylonium octacanthum_, n. sp. + +Cortical shell thorny, with eight long and thin cylindrical radial spines, +lying in two crossed diagonal planes, opposite in pairs, and arising from +the eight points where the transverse girdle is crossed by the lateral +girdle. All three girdles elliptical, one and a half times as long as +broad; four gates triangular. (This species is a further developmental +stage of _Tetrapyle octacantha_, with perfect sagittal girdle.) + +_Dimensions._--Principal axis 0.18, transverse axis 0.13; length of the +medullary shell 0.03 to 0.04. + +_Habitat._--Cosmopolitan; Mediterranean, Atlantic, Pacific, surface. + + +{656}6. _Pylonium stenozonium_, n. sp. + +Cortical shell thorny, with eight short conical radial spines, lying in two +crossed diagonal planes (as in the foregoing species). All three girdles +nearly of the same size, subcircular, very narrow, only with one to two +rows of pores. Four gates kidney-shaped. + +_Dimensions._--Principal axis 0.15, transverse axis 0.14; diameter of the +quadrangular medullary shell 0.04. + +_Habitat._--Equatorial Atlantic, Station 347, surface. + + + +Subfamily 3. TRIPLOZONARIA, Haeckel. + +_Definition._--#Pylonida# with three concentric systems of fenestrated +girdles, lying in three concentric lentelliptical faces (every system with +one to three girdles lying in one lentelliptical face). + + + +Genus 286. _Amphipylonium_,[325] Haeckel, 1881, Prodromus, p. 463. + +_Definition._--#Pylonida# with trizonal lentelliptical medullary shell, +surrounded by a double latticed cortical shell; inner cortical shell +_Pylonium_-shaped, with three perfect crossed girdles; outer cortical shell +only represented by a single (transverse) girdle. + +The genus _Amphipylonium_ opens the series of Triplozonaria, or of those +Pylonida in which the shell is composed of three concentric systems of +latticed girdles. The first (and innermost) system represents the complete +trizonal medullary shell, which is probably a lentelliptical +_Larnacilla_-shell. The first and intermediate system is formed of a +complete trizonal cortical shell of the same form, but much larger (like +_Pylonium_). The third (and outermost) system is represented by one to +three latticed girdles, corresponding to the former and forming an outer or +second cortical shell. In _Amphipylonium_ (as the most simple form of the +Triplozonaria) there is only developed the first (transverse) girdle of the +third system. It repeats therefore the form of _Amphipyle_, the cortical +shell of which is here double (Prodromus, 1881, p. 463). + + +1. _Amphipylonium semilunare_, n. sp. + +Inner cortical shell lentelliptical, one and a half times as long as broad, +with smooth surface and four semilunar gates. Transverse girdle of the +outer cortical shell with two smooth semilunar wings, with convex, smooth +lateral crests; each wing as broad as the transverse girdle of the inner +cortical shell and twice as long as its lateral girdle. + +_Dimensions._--Length of the lentelliptical medullary shell 0.04, breadth +0.03; length of the inner cortical shell 0.15, breadth 0.1; length of each +lateral wing of the outer cortical shell 0.3, breadth 0.1. + +_Habitat._--Pacific, central area, Station 271, depth 2425 fathoms. + + +{657}2. _Amphipylonium spinosissimum_, n. sp. + +Inner cortical shell lentelliptical, one and a third times as long as +broad, with thorny surface and four kidney-shaped gates. Transverse girdle +of the outer cortical shell very spiny, with two semilunar wings, with +convex thorny lateral crests; each wing one and a half times as broad as +the transverse girdle of the inner cortical shell, and one and a half times +as long as its lateral girdle. + +_Dimensions._--Length of the lentelliptical medullary shell 0.05, breadth +0.03; length of the inner cortical shell 0.16, breadth 0.12; length of each +lateral wing of the outer cortical shell 0.24, breadth 0.18. + +_Habitat._--Western Tropical Pacific, Station 225, depth 4475 fathoms. + + +3. _Amphipylonium tetraceros_, n. sp. + +Inner cortical shell hexagonal, one and a half times as long as broad, with +smooth surface and four transverse elliptical gates. Transverse girdle of +the outer cortical shell smooth, with rectilinear smooth lateral crests, +which are prolonged at both ends into strong conical spines (therefore four +spines in the lateral plane); each wing of the same breadth as the +transverse girdle of the inner cortical shell, and twice as long as its +lateral girdle. + +_Dimensions._--Length of the hexagonal medullary shell 0.03, breadth 0.02; +length of the inner cortical shell 0.12, breadth 0.08; length of each +lateral wing of the outer cortical shell 0.24, breadth 0.08. + +_Habitat._--Northern Pacific, Station 253, depth 3125 fathoms. + + +4. _Amphipylonium octoceros_, n. sp. + +Inner cortical shell quadrangular, one and a third times as long as broad, +with thorny surface and four kidney-shaped gates. Transverse girdle of the +outer cortical shell thorny, constricted at the equator, with concave +thorny lateral crests, and with eight strong radial spines, opposite in +pairs and lying in two crossed diagonal planes; each wing narrower than the +transverse girdle of the inner cortical shell and twice as long as its +lateral girdle. + +_Dimensions._--Length of the subspherical medullary shell 0.04, breadth +0.035; length of the inner cortical shell 0.14, breadth 0.11; length of +each lateral wing of the outer cortical shell 0.26, breadth 0.09. + +_Habitat._--Southern Pacific, Station 295, depth 1500 fathoms. + + + +Genus 267. _Tetrapylonium_,[326] Haeckel, 1881, Prodromus, p. 464. + +_Definition._--#Pylonida# with trizonal lentelliptical medullary shell, +surrounded by a double latticed cortical shell; inner cortical shell +_Pylonium_-shaped, with three perfect crossed girdles; outer cortical shell +represented by two crossed girdles, one (smaller) transverse and one +(larger) lateral girdle. + +{658}The genus _Tetrapylonium_ represents a further developmental stage of +the foregoing _Amphipylonium_; whilst in this latter the outer cortical +shell (or the third system of girdles) is formed only by a transverse +girdle, here this is crossed by a lateral girdle. _Tetrapylonium_ repeats +therefore the typical form of _Tetrapyle_, but with doubled cortical shell +(Prodromus, 1881, p. 464). + + +1. _Tetrapylonium pantellipticum_, n. sp. + +Outer cortical shell elliptical, one and a third times as long as broad, +with smooth surface and four elliptical gates. Inner cortical shell +elliptical, with smooth surface and four elliptical gates which repeat the +form of the four outer gates, but are of half the size. Transverse girdle +broad, with five pores on the isthmus. + +_Dimensions._--Length (or principal axis) of the first shell (medullary +shell) 0.04, breadth (or transverse axis) 0.03; length of the second (or +inner cortical) shell 0.12, breadth 0.09; length of the third (or outer +cortical) shell 0.18, breadth 0.14. + +_Habitat._--Pacific, central area, Station 274, depth 2750 fathoms. + + +2. _Tetrapylonium reniforme_, n. sp. + +Outer cortical shell elliptical, one and a half times as long as broad, +with thorny surface and four large kidney-shaped gates. Inner cortical +shell of the same form, but one-third smaller, also with four kidney-shaped +gates. Transverse girdle small, but with two pores on the isthmus. + +_Dimensions._--Length of the first (innermost) shell 0.03, breadth 0.02; +length of the second (middle) shell 0.14, breadth 0.08; length of the third +(outermost) shell 0.2, breadth 0.11. + +_Habitat._--Indian Ocean, Zanzibar, Pullen, depth 2200 fathoms. + + +3. _Tetrapylonium quadrangulare_, n. sp. (Pl. 9, fig. 15). + +Outer cortical shell nearly quadrangular, one and a third times as long as +broad, with four rounded corners, from which arise in the lateral plane +four three-sided pyramidal radial spines, opposite in pairs in two crossed +diagonal axes. Surface thorny; four gates elliptical or nearly +quadrangular. Inner cortical shell more elliptical, by one half smaller, +with broader transverse girdle and four kidney-shaped gates. Medullary +shell nearly spherical, of half the size. + +_Dimensions._--Length of the first shell 0.045, breadth 0.035; length of +the second shell 0.1, breadth 0.07; length of the third shell 0.16, breadth +0.11. + +_Habitat._--South Atlantic, off Tristan da Cunha, Station 332, depth 2200 +fathoms. + + +4. _Tetrapylonium octacanthum_, n. sp. + +Outer cortical shell elliptical, one and a third times as long as broad, +with thorny surface, and eight long and thin radial spines arising from the +corners of the four triangular gates, and lying {659}opposite in pairs in +two crossed diagonal planes. Inner cortical shell of the same shape, but +two-thirds smaller, also thorny. Transverse girdle broad, with four pores +on the isthmus. (This species appears to be the common _Tetrapyle +octacantha_, with doubled cortical shell.) + +_Dimensions._--Length of the first shell 0.04, breadth 0.03; length of the +second shell 0.16, breadth 0.12; length of the third shell 0.24, breadth +0.18. + +_Habitat._--Pacific, central area, Station 271, depth 2425 fathoms. + + +5. _Tetrapylonium armatum_, n. sp. + +Outer cortical shell nearly quadrangular, one and a fourth times as long as +broad, with very spiny surface. Between numerous smaller (simple or +branched) thorns arise twelve larger radial spines, symmetrically +distributed, eight wing-spines crossed in two diagonal planes (as in +_Tetrapylonium octacanthum_) and four corner spines on the four rounded +corners of the lateral plane (as in _Tetrapylonium quadrangulare_). +Therefore this species combines the armature of both foregoing species. +Four gates kidney-shaped. Inner cortical shell elliptical, smooth, +three-fourths smaller. + +_Dimensions._--Length of the first shell 0.045, breadth 0.035; length of +the second shell 0.18, breadth 0.15; length of the third shell 0.25, +breadth 0.2. + +_Habitat._--Pacific, central area, Station 266, depth 2750 fathoms. + + + +Genus 288. _Pylozonium_,[327] n. gen. + +_Definition._--#Pylonida# with trizonal lentelliptical medullary shell, +surrounded by double latticed cortical shell; inner cortical shell as well +as the outer _Pylonium_-shaped, each with three perfect crossed girdles +(transverse, lateral, and sagittal). + +The genus _Pylozonium_ is the most highly developed form of the Pylonida, +as all three systems of concentric girdles here become fully developed, +each system with three perfect girdles. In this genus only among all the +Pylonida we find nine complete latticed girdles, and in each of the three +dimensive planes three concentric elliptical girdles. The first system +forms the medullary shell, the second system the inner cortical shell, and +the third system the outer cortical shell. + + +1. _Pylozonium novemcinctum_, n. sp. + +Outer cortical shell lentelliptical, thorny, one and a third times as long +as broad, without radial spines, with four kidney-shaped gates. Inner +cortical shell of the same shape, but one-third smaller, four times as +large as the lentelliptical medullary shell. + +_Dimensions._--Length of the medullary shell 0.04, breadth 0.03; length of +the inner cortical shell 0.16, breadth 0.12; length of the outer cortical +shell 0.24, breadth 0.18. + +_Habitat._--North Pacific, Station 253, depth 3125 fathoms. + + +{660}2. _Pylozonium octacanthum_, n. sp. (Pl. 9, fig. 16). + +Outer cortical shell lentelliptical, one and a third times as long as +broad, with thorny surface and eight long and thin radial spines arising +from the corners of the four elliptical gates, and lying opposite in pairs +in two crossed diagonal planes. Inner cortical shell of the same shape but +one-fourth smaller, about twice as large as the lentelliptical medullary +shell. + +_Dimensions._--Length of the medullary shell 0.065, breadth 0.045; length +of the inner cortical shell 0.18, breadth 0.12; length of the outer +cortical shell 0.24, breadth 0.18. + +_Habitat._--North Pacific, Station 244, depth 2900 fathoms. + + + +Family XXVII. #THOLONIDA#, n. fam. (Pl. 10). + +_Definition._--#Larcoidea# with regular, completely latticed cortical +shell, which is composed of two to six or more hemispherical or cap-shaped +domes (vaulted chambers or cupolas). The domes lie opposite in pairs on the +poles of the three dimensive axes, are separated by annular constrictions, +and surround a simple or _Larnacilla_-shaped central chamber. + +The family #Tholonida# represents a peculiar and very remarkable group of +the #Larcoidea#, distinguished from the other groups of this suborder by +the characteristic form of the shell, composed of a variable number of +hemispherical domes or cupolas. The middle and original part of the shell +is constantly formed of an elliptical or subspherical central chamber, +which often, but not constantly, contains a small medullary shell. An even +number (two, four, six, or more) of domes is attached to the poles of the +three dimensive axes of the central chamber; according as only one, or two, +or all three axes develop cupolas, we distinguish in this family three +different subfamilies (the Amphitholida, Staurotholida, and Cubotholida). +The Amphitholida (or Tholonida monaxonia) form cupolas only on the two +poles of one single axis, and this axis corresponds to the minor (or +transverse) axis of the central chamber, we find here therefore constantly +at least two lateral cupolas (Pl. 10, figs. 1-7). The Staurotholida (or +Tholonida diaxonia) form cupolas on the poles of two axes perpendicular one +to another; these two axes are the major (principal) and the minor +(transverse) axis of the central chamber, we find here therefore constantly +at least four cupolas crossed in pairs (Pl. 10, figs. 8-11). The +Cubotholida (or Tholonida triaxonia) form cupolas on the poles of all three +dimensive axes (perpendicular one to another); corresponding to the +principal, transverse, and sagittal axes of the lentelliptical central +chamber; therefore we find here constantly at least six cupolas, attached +in pairs on the six sides of the central chamber (Pl. 10, figs. 12-17). + +The number of genera and species in the family #Tholonida# is rather large, +but the number of individuals is much smaller than in most of the other +SPUMELLARIA, and {661}particularly than in the nearly allied Pylonida; the +greater number of the species are very rare. Besides this they seem to be +very variable and inclined to produce numerous abnormalities. Very often +intermediate forms of transition are to be found between the Tholonida and +other #Larcoidea#, particularly the Pylonida and Lithelida. In many species +the thick-walled shell is very opaque, and offers great difficulties to the +clear study; in the greater number the structure of the shell cannot be +understood completely without rolling the shell to the different sides; and +the distinction between the Staurotholida and Cubotholida is often very +difficult. + +The primordial chamber of the Tholonida, or the central chamber in which +its growth begins, is either a simple lentelliptical shell (without +enclosed medullary shell), like _Cenolarcus_, or it is a trizonal shell, +like _Larnacilla_, and contains a small concentric medullary shell. But +this important inner shell of the central chamber offers peculiar +difficulties for study. In many cases (probably in the greater number) +there is no doubt the same characteristic trizonal medullary shell, which +we found in the Larnacida and Pylonida, and this is our principal argument, +if we regard the Tholonida as #Larcoidea#, which are most nearly allied to +both these families, and in which the fenestrated open cortical girdles of +the Pylonida are replaced by fenestrated closed cupolas or domes; the +characteristic "gates" or large fissures in the cortical shell of the +former are therefore here perfectly closed by network. The Tholonida agree +in this point with the Larnacida, but are distinguished from them by the +prominent vaultings of the hemispherical cupolas or domes, which give them +a peculiar appearance. Each pair of domes (opposite on both poles of one +dimensive axis) corresponds to one single girdle of the Pylonida. + +Regarding the absence or presence of a medullary shell in the central +chamber, we may divide the Tholonida into two groups, Cenotholida (without +medullary shell) and Coccotholida (with medullary shell). The absence of +the medullary shell in many Tholonida may be either primary (original) or +secondary (by reduction and loss of it). Probably in the larger proportion +(if not always?) its absence is the consequence of reduction and loss, and +in this case the Cenotholida must be derived phylogenetically from the +Coccotholida, but possibly often (or always?) the contrary may also be the +case. At present we cannot find certain arguments for one opinion or the +other. + +The connection between the medullary (internal) and the cortical (external) +shell of the central chamber in the Coccotholida is effected by two lateral +wings of a latticed transverse girdle; on both sides of the latter remain +the four internal open "gates" of the Pylonida and Larnacida. Very often +the limiting edges of these four gates are prolonged into eight external +radial spines which lie opposite in pairs in two crossed diagonal planes, +and correspond to the eight portal-spines of _Tetrapyle octacantha_. +Besides these, we often find four other beams opposite in pairs in the two +crossed axes (principal and lateral). Very often also these radial beams +(between medullary and {662}cortical shells) are prolonged on the outside +into prominent free radial spines. But other spines may also arise from the +surface. Very remarkable is the presence of twenty symmetrically disposed +radial spines in some forms of Amphitholida (_Amphitholus acanthometra_ and +_Amphitholonium acanthonium_, &c.). It recalls the twenty radial spines of +the #Acanthonida#, though the laws of distribution in the two similar cases +are quite different. + +The cortical shell of the Tholonida remains either simple, or it becomes +doubled by formation of an outer veil or envelope. This outer cortical +shell or "veil" may either repeat completely the typical form of the inner +with its cupolas, or it may form an ellipsoidal envelope without +dome-shaped partitions. Its network is either like that of the inner, or it +is very delicate and irregular, spider-web like. The connection between the +two cortical shells is effected by a variable number of radial beams, often +prolonged on the outside into radial spines. + +The growth of the Tholonida by apposition of new chambers is very +characteristic, constantly pairs of chambers originating at both opposite +poles of the three dimensive axes, firstly on the transverse axis, secondly +on the principal axis, thirdly on the sagittal axis. It is possible that by +repeated apposition of new chambers the Tholonida are transformed into +#Discoidea#, but commonly the number of domes is restricted, two in the +Amphitholida, four in the Staurotholida, six in the Coccotholida. If new +chambers in an irregular manner or in a spiral order be opposed to those +first formed pairs of chambers, the Tholonida may be transformed into +Soreumida, Streblemida, or Lithelida. The phylogenetic connection between +these families is probably very complex and very worthy of further +research. + +The network of the shell in the Tholonida is sometimes regular, with +circular (often hexagonally framed) pores of equal size, sometimes +irregular, with roundish pores of unequal size. Commonly the shell is thick +and compact; in those genera in which the cortical shell is doubled, the +inner is commonly compact, the outer a very delicate veil. + +The central capsule of the Tholonida is originally always enclosed by the +central chamber, and like this of lentelliptical form, a triaxial +ellipsoid. With the apposition of cupolas the growing central capsule may +form dome-shaped protuberances which enter into the former. So we may find +in the Amphitholida a central capsule with three joints (separated by two +annular parallel constrictions), in the Staurotholida a cross-shaped +capsule (with four caps around the central lentellipsis), in the +Cubotholida a clustered capsule with six caps, surrounding six sides of the +cubical central mass. In the Coccotholida (with medullary shell in the +central chamber) the latter encloses in the centre the nucleus of the cell. +The calymma, or the jelly-veil between the central capsule and the +enveloping shell, probably always exhibits annular constrictions, +corresponding to those which separate the cupolas of the shell. All these +anatomical peculiarities in the Tholonida require a further accurate study. + +{663}_Synopsis of the Genera of Tholonida._ + + + ------------------------------------------------------------------------- + I. Subfamily Amphitholida. + Cupolas developed only in the direction of one single axis (commonly + two cupolas). + (Tholonida unidimensiva.) + ------------------------------------------------------------------------- + {Two simple cupolas + { (without veil), 289. _Tholartus_. + Central chamber simple, { + without medullary shell. {Two double cupolas + { (with veil), 290. _Tholodes_. + + {Two simple cupolas + Central chamber { (without veil), 291. _Amphitholus_. + _Larnacilla_-shaped, with { + enclosed medullary shell. {Two double cupolas + { (with veil), 292. _Amphitholonium_. + ------------------------------------------------------------------------- + II. Subfamily Staurotholida. + Cupolas developed in the direction of two axes perpendicular one to + another (commonly four cupolas). + (Tholonida bidimensiva.) + ------------------------------------------------------------------------- + {Four simple cupolas + { (without veil), 293. _Tholostaurus_. + Central chamber simple, { + without medullary shell. {Four double cupolas + { (with veil), 294. _Tholoma_. + + {Four simple cupolas + Central chamber { (without veil), 295. _Staurotholus_. + _Larnacilla_-shaped, with { + enclosed medullary shell. {Four double cupolas + { (with veil), 296. _Staurotholonium_. + ------------------------------------------------------------------------- + III. Subfamily Cubotholida. + Cupolas developed in the direction of three axes perpendicular one + to another (commonly six cupolas). + (Tholonida tridimensiva.) + ------------------------------------------------------------------------- + {Six simple cupolas + { (without veil), 297. _Tholocubus_. + Central chamber simple, { + without medullary shell. {Six double cupolas + { (with veil), 298. _Tholonium_. + + {Six simple cupolas + Central chamber { (without veil), 299. _Cubotholus_. + _Larnacilla_-shaped, with { + enclosed medullary shell. {Six double cupolas + { (with veil), 300. _Cubotholonium_. + + + +Subfamily 1. AMPHITHOLIDA, Haeckel. + +_Definition._--#Tholonida# with monaxial growth; cupolas opposite on the +poles of one axis. (Shell commonly three-chambered, with two domes on both +sides of the central chamber.) + + + +Genus 289. _Tholartus_,[328] n. gen. + +_Definition._--#Tholonida# with simple cortical shell (without external +veil); with two hemispherical cupolas, opposite on the poles of one axis; +central chamber between them simple (without medullary shell). + +{664}The genus _Tholartus_ (Pl. 10, fig. 1) represents the most simple form +of all Tholonida, a three-jointed simple cortical shell without medullary +shell; two hemispherical cupolas or domes are attached on both lateral +sides of a simple triaxial ellipsoidal central chamber, corresponding to +the poles of its lateral or transverse axis. _Tholartus_ may be regarded as +the common ancestral form of all Tholonida, and may be derived either from +the Pylonida _Monozonium_ (by complete lattice-locking of the lateral +wings) or from the Ellipsida _Cenellipsis_ (by development of two lateral +protuberances on the poles of the transverse axis). But it is also possible +that the absence of the medullary shell is produced by reduction, and in +this case _Tholartus_ may be descended from _Amphitholus_. + + + +Subgenus 1. _Tholartella_, Haeckel. + +_Definition._--Surface of the shell smooth or rough, without radial spines. + + +1. _Tholartus tricolus_, n. sp. (Pl. 10, fig. 1). + +Central chamber one and a half times as high and as broad as both cupolas. +Surface of the shell rough. Pores regular, circular, without hexagonal +frames, three times as broad as the bars; about sixteen on the half +meridian of the central chamber (or its vertical diameter). + +_Dimensions._--Length of the shell (major axis of the central chamber, +vertical) 0.1, breadth of the shell (major axis of the whole +three-chambered shell, horizontal) 0.13; pores 0.01, bars 0.003. + +_Habitat._--Pacific, central area, Station 270, depth 2925 fathoms. + + +2. _Tholartus paniscus_, n. sp. + +Central chamber of the same breadth, but of the double height of both +cupolas. Surface of the shell rough. Pores regular, circular, with +hexagonal frames, of the same breadth as the bars; eight to ten on the half +meridian of the central chamber. + +_Dimensions._--Length of the shell (major axis of the central chamber, +vertical) 0.12, breadth of the shell (major axis of the whole +three-chambered shell, horizontal) 0.15; pores and bars 0.008. + +_Habitat._--Pacific, central area, Station 271, depth 2425 fathoms. + + +3. _Tholartus isocolus_, n. sp. + +Central chamber of the same breadth and height as both cupolas. Surface of +the shell smooth. Pores irregular, roundish, once to three times as broad +as the bars; ten to fifteen on the half meridian of the central chamber. + +_Dimensions._--Length of the shell 0.11, breadth 0.14; pores 0.004 to 0.01, +bars 0.003. + +_Habitat._--Pacific, central area, Station 270, depth 2925 fathoms. + + + +{665}Subgenus 2. _Tholartissa_, Haeckel. + +_Definition._--Surface of the shell with radial spines. + + +4. _Tholartus tripanis_, n. sp. + +Central chamber of the same size as both cupolas. Surface of the shell +thorny, everywhere covered with short conical radial spines, about as long +as the cupolas. Pores regular or subregular, circular, twice as broad as +the bars; eight to ten on the half meridian. + +_Dimensions._--Length of the shell 0.1, breadth 0.12; pores 0.01, bars +0.005. + +_Habitat._--South Pacific, Station 295, surface. + + +5. _Tholartus sagitta_, n. sp. + +Central chamber twice as large as both cupolas. Surface of the shell spiny, +with eight to twelve regularly (?) distributed radial spines, radiating +from the two constrictions between the three chambers. Spines +needle-shaped, very thin and long. Pores subregular or irregular, roundish +or circular, about three times as broad as the bars; twelve to sixteen on +the half meridian. + +_Dimensions._--Length of the shell 0.11, breadth 0.15; pores 0.01, bars +0.003. + +_Habitat._--North Pacific, Station 244, surface. + + + +Genus 290. _Tholodes_,[329] n. gen. + +_Definition._--#Tholonida# with double cortical shell (with external veil), +with two hemispherical cupolas, opposite on the poles of one axis; central +chamber between them simple (without medullary shell). + +The genus _Tholodes_ (Pl. 10, fig. 2) differs from _Tholartus_, its +probable ancestral form, only in the duplication of the shell; the outer +shell has exactly the same three-jointed form as the inner; both are +connected by eight radial beams, lying in two diagonal planes and +corresponding to the eight frontal spines of _Tetrapyle octacantha_. +Possibly _Tholodes_ may also be descended from _Amphitholonium_ by loss of +the medullary shell. I have observed only one single specimen of this +genus. + + +1. _Tholodes cupula_, n. sp. (Pl. 10, fig. 2). + +Outer shell of the same form and structure as the inner shell. Central +chamber larger than both cupolas. Surface a little rough, without radial +spines. Distance of both shells equals the height of the outer cupolas. +Pores of both shells regular, circular, three times as broad as the +{666}bars; six to seven in the semicircle of one inner cupola, ten to +twelve in the semicircle of one outer cupola. Both shells are connected by +eight radial beams, crossed in two diagonal planes. + +_Dimensions._--Major axis of the outer shell 0.1, minor 0.065; major axis +of the inner shell 0.05, minor 0.04; pores 0.006, bars 0.002. + +_Habitat._--Western Tropical Pacific, Station 225, depth 4475 fathoms. + + + +Genus 291. _Amphitholus_,[330] n. gen. + +_Definition._--#Tholonida# with simple cortical shell (without external +veil), with two hemispherical cupolas, opposite on the poles of one axis; +central chamber (between them) _Larnacilla_-shaped, with medullary shell. + +The genus _Amphitholus_ is the most simple form of all Coccotholida (or all +Tholonida provided with medullary shell). Its simple cortical shell +exhibits, like _Tholartus_, two lateral hemispheric cupolas, attached on +both sides of a lentelliptical central chamber (on the poles of its +transverse axis). The central chamber has the form of a triaxial ellipsoid, +and contains, like _Larnacilla_, a small medullary shell, connected with it +by the wings of a latticed transverse girdle. _Amphitholus_ may be derived +either from _Tholartus_ by secondary production of a cortical shell, or +(more probably) from _Larnacilla_ by apposition of two lateral dome-shaped +protuberances. In the latter case it may be regarded as an _Amphipyle_, the +lateral open wings of which are closed by lattice-work. + + + +Subgenus 1. _Amphitholissa_, Haeckel. + +_Definition._--Surface of the shell smooth or rough, without radial spines. + + +1. _Amphitholus artiscus_, n. sp. (Pl. 10, fig. 3). + +Central chamber of the same height as both cupolas. Surface of the cortical +shell rough. Pores regular, circular, with prominent hexagonal frames, +twice as broad as the bars; eight to ten in the basal semicircle of one +cupola. + +_Dimensions._--Major axis of the shell 0.16, minor axis 0.1; pores 0.008, +bars 0.004. + +_Habitat._--Pacific, central area, Station 272, depth 2600 fathoms. + + +2. _Amphitholus artidium_, n. sp. + +Central chamber one-fourth higher than both cupolas. Surface of the +cortical shell smooth. Pores irregular, roundish, once to three times as +broad as the bars. (Very similar to _Tholartus_ tricolus, Pl. 10, fig. 1, +but different by the medullary shell.) + +_Dimensions._--Major axis of the shell 0.15, minor axis 0.12; pores 0.004 +to 0.01, bars 0.003. + +_Habitat._--North Pacific, Station 241, depth 2300 fathoms. + + + +{667}Subgenus 2. _Amphitholura_, Haeckel. + +_Definition._--Surface of the shell with radial spines or thorns. + + +3. _Amphitholus octacanthus_, n. sp. + +Central chamber about twice as high and broad as both cupolas. From the +surface arise, symmetrically distributed, eight stout conical radial +spines, lying in two diagonal planes, as prolongations of the eight +wing-beams, which connect the _Tetrapyle_-shaped medullary shell with the +two ring-like constrictions of the cortical shell. Pores of the latter +regular, circular, twice as broad as the bars; ten to twelve in the basal +semicircle of one cupola. + +_Dimensions._--Major axis of the shell 0.15, minor 0.12; pores 0.01, bars +0.005. + +_Habitat._--South Atlantic, Station 332, depth 2200 fathoms. + + +4. _Amphitholus dodecanthus_, n. sp. + +Central chamber a little larger than both cupolas. From the surface arise +twelve strong conical radial spines, four on the poles of the major and the +minor axis of the shell, lying in the lateral plane; eight others lying in +two diagonal planes, as prolongations of the eight wing-beams, which +connect the _Tetrapyle_-shaped medullary shell with the two ring-like +constrictions of the cortical shell. Pores of the latter irregular, +roundish, twice to four times as broad as the bars; sixteen to eighteen in +the basal semicircle of one cupola. + +_Dimensions._--Major axis of the shell 0.15, minor 0.11; pores 0.004 to +0.008, bars 0.002. + +_Habitat._--North Pacific, Station 256, surface. + + +5. _Amphitholus acanthometra_, n. sp. (Pl. 10, figs. 5, 6). + +Central chamber about twice as broad and as high as both cupolas. On the +surface quite symmetrically distributed twenty long and strong cylindrical +radial spines; eight in the sagittal plane or in the meridian plane of the +central chamber (four opposite in pairs in the principal and the sagittal +axes, four others in the middle between the principal and the sagittal +spines); four in the horizontal transverse plane, on both sides of the +poles of the major or lateral axis; and eight in diagonal planes +(corresponding to the eight wing-spines of _Tetrapyle octacantha_). In the +centre of the central chamber is a distinct trizonal medullary shell like +that of _Tetrapyle_, with two vertical columella beams. Pores of the +cortical shell subregular, circular, with elevated hexagonal frames, about +four times as broad as the bars; five to seven in the semicircle of one +cupola. (This remarkable species differs from _Tholartus vicenus_ in the +possession of a medullary shell, from _Amphitholonium acanthometra_ by the +simple cortical shell. Compare these species). + +_Dimensions._--Major axis of the shell 0.14 to 0.16, minor axis 0.10 to +0.12; pores 0.015, bars 0.004; major axis of the medullary shell 0.04 to +0.05, minor (horizontal) axis 0.02 to 0.03; length of the twenty radial +spines 0.18 to 0.24, basal breadth 0.01. + +_Habitat._--South Pacific, Station 300, depth 1375 fathoms. + + +{668}6. _Amphitholus armatus_, n. sp. + +Central chamber twice as broad, but of the same height, as the flat vaulted +cupolas. Surface armed with thirty to forty very large three-sided +prismatic spines, longer than the major axis of the shell. Pores irregular, +roundish, twice to five times as broad as the bars; eight to nine on the +basal semicircle of one cupola. + +_Dimensions._--Major axis of the shell 0.15, minor axis 0.1; pores 0.006 to +0.015, bars 0.003; length of the spines 0.2 to 0.25, breadth 0.01. + +_Habitat._--North Atlantic, Station 353, surface. + + +7. _Amphitholus polyacanthus_, n. sp. + +Central chamber of the same breadth and height as both cupolas. Surface +armed with very numerous (sixty to eighty) strong conical spines, about as +long as the minor axis of the shell. Pores subregular, circular, twice as +broad as the bars; sixteen to eighteen in the basal semicircle of one +cupola. + +_Dimensions._--Major axis of the shell 0.13, minor 0.08; pores 0.006, bars +0.003; length of the radial spines 0.09, breadth 0.006. + +_Habitat._--South Atlantic, Station 332, depth 2200 fathoms. + + +8. _Amphitholus panicium_, n. sp. (Pl. 10, fig. 4). + +Central chamber ellipsoidal, nearly twice as broad, but of the same height, +as both cupolas. Whole surface thorny; the largest radial thorns about as +long as the medullary shell. Pores irregular, roundish, twice to four times +as broad as the bars. On the base of each cupola a circle of ten to twelve +larger square pores, separated by radial beams, which are prolonged into +stouter free spines. This remarkable formation of the cupolas, very rare in +this family, recalls the characteristic formation of the distal chambers of +the Panartida and Zygartida (_e.g._, Pl. 40, figs. 4, 8, &c.), where it is +very common. + +_Dimensions._--Major axis of the shell 0.15, minor 0.1; pores 0.005 to +0.012, bars 0.003; large square pores 0.02; axes of the medullary shell +0.03 and 0.02. + +_Habitat._--Indian Ocean, Madagascar, Rabbe, surface. + + + +Genus 292. _Amphitholonium_,[331] n. gen. + +_Definition._--#Tholonida# with double cortical shell (with external veil), +with two hemispherical cupolas, opposite on the poles of one axis; central +chamber (between them) _Larnacilla_-shaped, with medullary shell. + +The genus _Amphitholonium_ differs from the nearly allied _Amphitholus_ +(probably its ancestral form) only in the duplication of the cortical +shell; the outer has the {669}same three-jointed form as the inner, and is +connected with it by a variable number of radial beams. From the similar +_Tholodes_ it differs in the possession of a medullary shell. + + +1. _Amphitholonium tricolonium_, n. sp. (Pl. 10, fig. 7). + +Outer cortical shell smooth, of the same three-jointed form as the inner, +at an equal distance from it throughout the whole circumference; central +chamber higher-vaulted than both cupolas. Network of the outer shell +delicate, with subregular, circular pores. Pores of the thick-walled inner +shell subregular, circular, with hexagonal frames, three times as broad as +the bars; eight to ten in the basal semicircle of one cupola. + +_Dimensions._--Major axis of the outer cortical shell 0.2, minor axis 0.15; +major axis of the inner cortical shell 0.16, minor axis 0.11; pores 0.01, +bars 0.0035. + +_Habitat._--South Pacific, Station 302, depth 1450 fathoms. + + +2. _Amphitholonium octostylium_, n. sp. + +Outer cortical shell lentelliptical, smooth, not articulated, at a varying +distance from the three-jointed inner shell; central chamber of the latter +twice as high as both hemispherical cupolas. Network of the outer shell +very thin, cob-web like. Pores of the inner shell subregular, roundish, +twice as broad as the bars; six to seven in the semicircle of one cupola. +Eight thin and long, bristle-shaped, radial spines, opposite in pairs in +two crossed diagonal planes. + +_Dimensions._--Major axis of the outer cortical shell 0.16, minor 0.12; +major axis of the inner cortical shell 0.12, minor 0.09; pores 0.01, bars +0.005. + +_Habitat._--Pacific, central area, Station 273, depth 2350 fathoms. + + +3. _Amphitholonium acanthonium_, n. sp. + +Outer cortical shell of the same three-jointed form as the inner, at a +uniform distance from it; central chamber higher vaulted than both cupolas. +Network of the outer shell irregular, delicate, of the inner regular, +strong, with circular, hexagonally framed pores, three times as broad as +the bars; eight to nine in the semicircle of one cupola. On the surface, +quite symmetrically disposed, twenty long and strong, cylindrical, radial +spines; eight in the sagittal plane, four in the transverse plane; eight in +two diagonal planes between the former and the latter. The remarkable +geometric disposition of the twenty spines is in this species quite the +same as in _Amphitholus acanthometra_. It differs from this nearly allied +species in the double cortical shell. + +_Dimensions._--Major axis of the outer cortical shell 0.18, minor 0.14; +major axis of the inner cortical shell 0.14, minor 0.1; pores 0.012, bars +0.004. + +_Habitat._--South Pacific, Station 295, surface. + + + +{670}Subfamily 2. STAUROTHOLIDA, Haeckel. + +_Definition._--#Tholonida# with diaxial growth; cupolas crossed in pairs, +opposite on the poles of two axes, perpendicular one to another. (Shell +commonly five-chambered, with four domes, cross-wise surrounding the +central chamber.) + + + +Genus 293. _Tholostaurus_,[332] n. gen. + +_Definition._--#Tholonida# with simple cortical shell (without external +veil), composed of four hemispherical cupolas in cross-form, opposite in +pairs on the poles of two axes perpendicular one to another; central +chamber simple (without medullary shell). + +The genus _Tholostaurus_ is the most simple form of the Staurotholida, or +the Tholonida with four crossed hemispherical cupolas, lying on the poles +of two axes perpendicular one to another. The central chamber communicates +by four wide openings with the four domes, and contains no medullary shell. +_Tholostaurus_ may originate either from _Tholartus_ by apposition of two +opposite cupolas between the first pair, or from _Staurotholus_ by loss of +the medullary shell. + + + +Subgenus 1. _Tholostaurantha_, Haeckel. + +_Definition._--Surface of the shell smooth or rough, without radial spines. + + +1. _Tholostaurus quadrigatus_, n. sp. + +All four cupolas nearly of the same size and form, subregular. Surface +smooth, without radial spines. Pores subregular, circular, four times as +broad as the bars; eight to ten pores in the basal semicircle of one +cupola. + +_Dimensions._--Diameter of the shell 0.12; pores 0.008, bars 0.002. + +_Habitat._--Pacific, central area, Station 272, surface. + + +2. _Tholostaurus cruciformis_, n. sp. + +Two opposite cupolas larger than the two others. Surface rough, without +radial spines. Pores regular, circular, hexagonally framed, twice as broad +as the bars; twelve to fourteen in the basal semicircle of one cupola. + +_Dimensions._--Major axis of the shell 0.16, minor axis 0.12; pores 0.006, +bars 0.003. + +_Habitat._--Pacific, central area, Station 265, depth 2900 fathoms. + + + +{671}Subgenus 2. _Tholostauroma_, Haeckel. + +_Definition._--Surface of the shell with radial spines or thorns. + + +3. _Tholostaurus tetrabelonis_, n. sp. + +All four cupolas nearly of the same size and form, subregular. Pores +regular, circular, hexagonally framed, twice as broad as the bars; twelve +to fourteen in the semicircle of one cupola. Four long and stout conical +radial spines, two vertical on the poles of the principal axis, two +horizontal on the poles of the transverse axis. + +_Dimensions._--Major axis of the shell 0.15, minor 0.13; pores 0.006, bars +0.003. + +_Habitat._--South Pacific, Station 288, surface. + + +4. _Tholostaurus octobelonis_, n. sp. + +Two opposite cupolas larger than the two others. Pores subregular, +circular, three times as broad as the bars; ten to twelve in the semicircle +of one cupola. Eight long and thin, needle-shaped, radial spines, in pairs +crossed in two diagonal planes. + +_Dimensions._--Major axis of the shell 0.16, minor 0.12; pores 0.01, bars +0.003. + +_Habitat._--South Pacific, Station 291, surface. + + +5. _Tholostaurus dodecabelos_, n. sp. + +Two opposite cupolas larger than the two others. Pores irregular, roundish, +twice to three times as broad as the bars; six to eight in the semicircle +of one cupola. Twelve thin and long radial spines, four on the poles of the +two crossed axes (principal and lateral), eight crossed in two diagonal +planes. + +_Dimensions._--Major axis of the shell 0.14, minor 0.11; pores 0.006 to +0.01, bars 0.003. + +_Habitat._--North Pacific, Station 244, depth 2900 fathoms. + + +6. _Tholostaurus polybelonis_, n. sp. + +Two opposite cupolas larger than the two others. Pores circular, +hexagonally framed, of the same breadth as the bars; ten to twelve in the +semicircle of one cupola. Numerous (twenty to thirty or more) thin, +bristle-like, radial spines, about as long as the radius of the shell. + +_Dimensions._--Major axis of the shell 0.15, minor axis 0.12; pores and +bars 0.007. + +_Habitat._--Indian Ocean, Zanzibar, Pullen, depth 2200 fathoms. + + + +Genus 294. _Tholoma_,[333] n. gen. + +_Definition._--#Tholonida# with double cortical shell (with external veil), +composed of four hemispherical cupolas in cross-form, opposite in pairs on +the poles of two axes perpendicular one to another; central chamber simple +(without medullary shell). + +{672}The genus _Tholoma_ (Pl. 10, figs. 10, 13) differs from the preceding +_Tholostaurus_ (its probable ancestral form) only in the duplication of the +shell. The outer (secondary) shell has the same cross-form as the inner +(primary) shell. In the two observed species the growth seems to be +different, in the first species all four cupolas of each cross being of the +same size, form, and age; in the second two opposite cupolas, larger and +apparently older than the other two. _Tholoma_ is possibly the offspring of +_Staurotholonium_, from which it may have been produced by loss of the +medullary shell. + + + +Subgenus 1. _Tholomantha_, Haeckel. + +_Definition._--Surface of the shell smooth, without radial spines. + + +1. _Tholoma quadrigeminum_, n. sp. (Pl. 10, fig. 10). + +All four chambers in each cortical shell nearly equal, subregular. Surface +smooth, without radial spines. Structure of the network in both shells +similar. Pores regular, circular, twice as broad as the bars; six to eight +in the basal semicircle of one inner, ten to twelve in the semicircle of +one outer cupola. + +_Dimensions._--Diameter of the outer shell 0.14, of the inner 0.09; pores +0.006, bars 0.003. + +_Habitat._--South Pacific, Station 302, surface. + + + +Subgenus 2. _Tholomura_, Haeckel. + +_Definition._--Surface of the shell with radial spines. + + +2. _Tholoma metallasson_,[334] n. sp. (Pl. 10, fig. 13). + +Two opposite chambers in each cortical shell larger than the two others; +the larger chambers of the inner shell corresponding to the smaller +chambers of the outer shell. Network in both shells of the same structure, +regular, with circular, hexagonally framed pores of the same breadth as the +bars; eight to ten in the semicircle of an inner, fourteen to sixteen in +the semicircle of an outer cupola. Numerous (twenty to thirty or more) +thin, cylindrical, bristle-shaped, long radial spines, symmetrically +disposed. + +_Dimensions._--Major axis of the outer shell 0.26, minor axis 0.2; major +axis of the inner shell 0.16, minor axis 0.13; pores and bars 0.006. + +_Habitat._--Pacific, central area, Station 265, depth 2900 fathoms. + + + +Genus 295. _Staurotholus_,[335] n. gen. + +_Definition._--#Tholonida# with simple cortical shell (without external +veil), composed of four hemispherical cupolas in cross-form, opposite in +pairs on the poles of {673}two axes perpendicular one to another; central +chamber _Larnacilla_-shaped (with enclosed medullary shell). + +The genus _Staurotholus_ differs from _Tholostaurus_ in the possession of a +medullary shell in the central chamber, and may be derived from this genus +by its production. But it may also be derived from _Amphitholus_ by +apposition of two secondary opposite cupolas between the two primary +cupolas. The symmetrical position of an increasing number of radial spines +in the different species is remarkable (resembling _Tholostaurus_ as well +as _Amphitholus_). + + + +Subgenus 1. _Staurotholissa_, Haeckel. + +_Definition._--Surface of the shell smooth or rough, without radial spines. + + +1. _Staurotholus quadratus_, n. sp. + +Surface of the cortical shell smooth. All four cupolas nearly of the same +size and form; therefore principal and lateral axes equal. Pores regular, +circular, with hexagonal frames, twice as broad as the bars; eight to ten +on the basal semicircle of one cupola. Medullary shell square. + +_Dimensions._--Diameter of the cortical shell 0.15; pores 0.01, bars 0.005. + +_Habitat._--South Atlantic, Station 323, depth 1900 fathoms. + + +2. _Staurotholus cruciatus_, n. sp. + +Surface of the cortical shell rough. The two principal cupolas somewhat +larger than the two lateral cupolas; therefore the longitudinal axis longer +than the transverse. Pores irregular, roundish, twice to three times as +broad as the bars; twelve to sixteen in the semicircle of one cupola. + +_Dimensions._--Major axis of the shell 0.16, minor 0.13; pores 0.005 to +0.009, bars 0.003. + +_Habitat._--Pacific, central area, Station 266, depth 2750 fathoms. + + + +Subgenus 2. _Staurotholura_, Haeckel. + +_Definition._--Surface of the shell with radial spines. + + +3. _Staurotholus tetrastylus_, n. sp. (Pl. 10, fig. 8). + +The two principal cupolas smaller than the two lateral cupolas. Pores +subregular, circular, three times as broad as the bars; six to eight in the +semicircle of one cupola. Medullary shell elliptical. On the surface four +long cylindrical radial spines; two in the principal and two in the lateral +axis. + +_Dimensions._--Major axis of the cortical shell 0.15, minor 0.12; pores +0.012, bars 0.004. + +_Habitat._--South Pacific, Station 166, surface. + + +{674}4. _Staurotholus octostylus_, n. sp. + +The two lateral cupolas larger than the two principal cupolas. Pores +subregular, circular, twice as broad as the bars; ten to twelve in the +semicircle of one cupola. Medullary shell hexagonal, connected with each +ring-like constriction by eight strong cylindrical radial spines (longer +than the whole shell), lying in two crossed meridian planes, and +corresponding to the eight diagonal wing-spines of _Tetrapyle octacantha_. + +_Dimensions._--Major axis of the cortical shell 0.12, minor 0.1; pores +0.008, bars 0.004. + +_Habitat._--Pacific, central area, Station 274, depth 2750 fathoms. + + +5. _Staurotholus decastylus_, n. sp. + +The two principal cupolas twice as broad and high as the two lateral +cupolas. Pores subregular, circular, four times as broad as the bars; six +to eight in the semicircle of one cupola. Ten long and thin radial spines +with thickened conical bases, about as long as the major axis of the shell, +by inner prolongations connected with the lentelliptical medullary shell; +two polar spines in the principal axis, eight wing-spines in two crossed +diagonal planes. + +_Dimensions._--Major axis 0.12, minor 0.1; pores 0.012, bars 0.003. + +_Habitat._--Western Tropical Pacific; Station 224, depth 1850 fathoms. + + +6. _Staurotholus dodecastylus_, n. sp. (Pl. 10, fig. 9). + +The two lateral cupolas larger than the two principal cupolas. Pores +subregular, circular, three times as broad as the bars; five to seven in +the semicircle of one cupola. Twelve strong cylindrical radial spines, four +on the poles of the two larger axes (two principal and two lateral), eight +wing-spines in two crossed diagonal planes. Medullary shell hexagonal. + +_Dimensions._--Major (lateral) axis 0.11, minor (principal) 0.09; pores +0.009, bars 0.003. + +_Habitat._--Tropical Atlantic, Station 348, surface. + + +7. _Staurotholus polystylus_, n. sp. + +The two principal cupolas larger than the two lateral cupolas. Pores +irregular, roundish, twice to three times as broad as the bars; ten to +twelve in the semicircle of one cupola. On the surface numerous thin +bristle-shaped spines (twenty to thirty or more). + +_Dimensions._--Major axis 0.14, minor 0.11; pores 0.006 to 0.01, bars +0.003. + +_Habitat._--North Pacific, Station 231, surface. + + + +Genus 296. _Staurotholonium_,[336] n. gen. + +_Definition._--#Tholonida# with double cortical shell (with external veil), +composed of four hemispherical cupolas in cross-form, opposite in pairs on +the poles of two axes perpendicular one to another; central chamber +_Larnacilla_-shaped (with medullary shell). + +{675}The genus _Staurotholonium_ differs from the nearly allied +_Staurotholus_ (its probable ancestral form) only in the duplication of the +cortical shell. The outer shell commonly repeats the cross-form of the +inner, with four corresponding cupolas; but sometimes the four cupolas of +the outer shell alternate in size and form with those of the inner, or the +outer shell forms a simple lenticular envelope around the inner. From the +similar _Tholoma_, _Staurotholonium_ differs in the possession of a +medullary shell in the central chamber. + + + +Subgenus 1. _Staurotholodes_, Haeckel. + +_Definition._--Surface of the outer cortical shell smooth or rough, without +radial spines. + + +1. _Staurotholonium biquadratum_, n. sp. + +Outer cortical shell smooth, of the same regular crucial form as the inner, +equidistant from it everywhere. Form and structure of both cortical shells +nearly the same, but the outer about twice as large as the inner; both +connected only by eight diagonal beams. All four cupolas of each cortical +shell regular, of the same size. Pores regular, circular, twice as broad +as the bars; six to eight in the basal semicircle of each cupola. Medullary +shell square. (Similar to _Staurotholus quadratus_, but differs by the +double cortical shell.) + +_Dimensions._--Diameter of the outer cortical shell 0.16, of the inner +0.08, of the medullary shell 0.04; pores of the inner cortical shell 0.006, +bars 0.003. + +_Habitat._--South Pacific, Station 295, depth 1500 fathoms. + + +2. _Staurotholonium bicruciatum_, n. sp. + +Outer cortical shell rough, twice as large as the inner, of the same form +and structure, at an equal distance from it. In both shells the principal +cupolas are larger than the lateral. Pores irregular, roundish, in the +outer shell four times, in the inner twice as large as the bars; eight to +ten in the basal semicircle of one cupola. (Similar to _Staurotholus +cruciatus_, but differs mainly in the double cortical shell.) Medullary +shell lentelliptical. + +_Dimensions._--Major (longitudinal) axis of the outer cortical shell 0.016, +of the inner 0.08; minor (transverse) axis of the former 0.14, of the +latter 0.07; medullary shell 0.03 to 0.04. + +_Habitat._--Pacific, central area, Station 267, depth 2700 fathoms. + + +3. _Staurotholonium alternatum_, n. sp. + +Outer cortical shell smooth, very different from the inner; in the outer +the two principal cupolas are larger than the two lateral; in the inner +inversely smaller. Pores subregular, circular, in the outer shell four +times, in the inner shell twice as broad as the bars; ten to twelve pores +in the basal semicircle of one cupola. + +{676}_Dimensions._--Major axis (length) of the outer cortical shell 0.15, +minor (breadth) 0.13; pores 0.012, bars 0.003; major axis (length) of the +inner cortical shell 0.11, minor axis (breadth) 0.09; pores 0.006, bars +0.003. + +_Habitat._--Indian Ocean, surface, Madagascar, Rabbe. + + +4. _Staurotholonium lenticulare_, n. sp. + +Outer cortical shell smooth, lenticular, with circular circumference, with +very delicate irregular network and small roundish pores. Its distance from +the inner much greater in the four diagonal points than in the four polar +points. Inner cortical shell regular, cross-like, with four cupolas of +similar size and form. Pores subregular, circular, twice as broad as the +bars; eight to ten in the basal semicircle of one cupola. Medullary shell +lenticular. + +_Dimensions._--Diameter of the outer cortical shell 0.16, of the inner +0.12; pores of the inner 0.008, bars 0.004. + +_Habitat._--North Atlantic, Station 353, surface. + + + +Subgenus 2. _Staurotholoma_, Haeckel. + +_Definition._--Surface of the outer cortical shell with radial spines or +thorns. + + +5. _Staurotholonium octodoratium_, n. sp. + +Outer cortical shell of the same form and structure as the inner, but twice +as large, both principal domes somewhat larger than both lateral. Pores +subregular, circular, of the same breadth as the bars; five to six in the +semicircle of one inner, eight to ten of one outer cupola. Eight thin and +long bristle-like spines, opposite in pairs in two crossed diagonal planes. + +_Dimensions._--Major axis of the outer cortical shell 0.15, minor 0.12; +major axis of the inner cortical shell 0.07, minor 0.06; pores and bars +0.005. + +_Habitat._--North Pacific, Station 231, surface. + + +6. _Staurotholonium octodoronium_, n. sp. (Pl. 10, fig. 11). + +Outer cortical shell of the same form as the inner, both little distant; +network of the outer irregular and delicate. Pores of the inner regular, +circular, twice as broad as the bars; seven to nine in the basal semicircle +of one cupola. Both lateral domes larger than the principal. Eight long and +thin, cylindrical radial spines opposite in pairs in two crossed diagonal +planes. + +_Dimensions._--Major axis of the outer cortical shell 0.2, minor 0.18; +major axis of the inner cortical shell 0.16, minor 0.14; pores 0.008, bars +0.004. + +_Habitat._--South Pacific, Station 288, surface. + + + +{677}Subfamily 3. CUBOTHOLIDA, Haeckel. + +_Definition._--#Tholonida# with triaxial growth; cupolas lying in pairs on +the six sides of a cubical central chamber, opposite at the poles of three +axes perpendicular one to another. (Shell commonly seven-chambered, with +six domes surrounding the central chamber.) + + + +Genus 297. _Tholocubus_,[337] n. gen. + +_Definition._--#Tholonida# with simple cortical shell (without external +veil), composed of six hemispherical cupolas, opposite in pairs on the +poles of three axes perpendicular one to another, covering six sides of the +simple cuboidal central chamber (without medullary shell). + +The genus _Tholocubus_ is the most simple form of the Cubotholida, or of +the Tholonida with domes situated in three axes perpendicular one to +another; six hemispherical cupolas lying on the six sides of a cuboidal +central chamber; this latter contains no medullary shell. _Tholocubus_ may +be derived phylogenetically either from _Tholostaurus_ by apposition of two +opposite domes on the flat sides of the cross-shell, or from _Cubotholus_ +by loss of the medullary shell. + + + +Subgenus 1. _Tholocubulus_, Haeckel. + +_Definition._--Surface of the shell smooth or rough, without radial spines. + + +1. _Tholocubus tessellatus_, n. sp. (Pl. 10, fig. 12). + +Surface of the shell smooth, without radial spines. Pores regular, +circular, hexagonally framed, twice as broad as the bars; eight to twelve +pores on the semicircle of one cupola. Principal cupolas smaller than the +lateral, larger than the sagittal cupolas. + +_Dimensions._--Diameter of the shell 0.15; pores 0.01, bars 0.005. + +_Habitat._--South Atlantic, Station 332, depth 2200 fathoms. + + +2. _Tholocubus tesserarius_, n. sp. + +Surface of the shell rough, without radial spines. Pores irregular, +roundish, once to three times as broad as the bars; twelve to sixteen pores +in the semicircle of one cupola. All six cupolas nearly of the same size. + +_Dimensions._--Diameter of the shell 0.16; pores 0.004 to 0.008, bars +0.003. + +_Habitat._--North Atlantic, Station 353, depth 2965 fathoms. + + + +{678}Subgenus 2. _Tholocubitus_, Haeckel. + +_Definition._--Surface of the shell with radial spines or thorns. + + +3. _Tholocubus tesseralis_, n. sp. (Pl. 10, fig. 16). + +Surface of the shell with numerous (eight to sixteen) thin and long, +bristle-shaped radial spines (the greater part broken off in the figured +specimen); pores subregular, circular, three to four times as broad as the +bars; ten to twelve in the semicircle of one cupola. + +_Dimensions._--Major axis of the shell 0.16, minor axis 0.14; pores 0.01, +bars 0.0027. + +_Habitat._--Pacific, central area, Station 271, depth 2425 fathoms. + + + +Genus 298. _Tholonium_,[338] n. gen. + +_Definition._--#Tholonida# with double cortical shell (with external veil), +composed of six hemispherical cupolas, opposite in pairs on the poles of +three axes perpendicular one to another, covering six sides of the simple +cuboidal central chamber (without medullary shell). + +The genus _Tholonium_ (Pl. 10, fig. 17) differs from the preceding +_Tholocubus_ only in the duplication of the cortical shell. The outer +(secondary) shell forms either a simple (spheroidal or ellipsoidal) thin +veil around the inner (primary) shell, or both shells are of the same form, +with six corresponding cupolas. Possibly _Tholonium_ is the offspring of +_Cubotholonium_, having originated by loss of the medullary shell. + + + +Subgenus 1. _Tholonetta_, Haeckel. + +_Definition._--Surface of the shell smooth or rough, without radial spines +or thorns. + + +1. _Tholonium bicubicum_, n. sp. + +Outer shell with six hemispherical dome-shaped protuberances, corresponding +in those of the inner shell. Both shells connected by numerous radial +beams. Surface of the outer shell smooth; its network nearly of the same +shape as that of the inner, with subregular, circular pores, twice as broad +as the bars; ten to fifteen pores on the semicircle of one cupola. + +_Dimensions._--Diameter of the outer shell 0.14, of the inner 0.12; pores +of the latter 0.006, bars 0.003. + +_Habitat._--South Atlantic, Station 325, depth 2650 fathoms. + + +{679}2. _Tholonium ellipticum_, n. sp. + +Outer shell ellipsoidal, without dome-shaped protuberances, with smooth +surface, without radial spines; network delicate, with subregular, circular +pores. Inner shell with regular, circular, hexagonally framed pores, twice +as broad as the bars; ten to twelve pores on the semicircle of one cupola. + +_Dimensions._--Major axis of the outer shell 0.16, minor axis 0.14; major +axis of the inner shell 0.14, minor axis 0.12; pores 0.008, bars 0.004. + +_Habitat._--Pacific central area, Station 267, depth 2700 fathoms. + + +3. _Tholonium sphaericum_, n. sp. + +Outer shell spherical, without dome-shaped protuberances, with smooth +surface, without radial spines; network very delicate, with very small +subregular, circular pores. Inner shell with regular, circular pores of the +same breadth as the bars; fourteen to sixteen on the basal semicircle of +one cupola. + +_Dimensions._--Diameter of the spherical outer shell 0.15, inner shell +0.12; pores and bars of the inner shell 0.005. + +_Habitat._--Indian Ocean, Zanzibar, Pullen, depth 2200 fathoms. + + + +Subgenus 2. _Tholonilla_, Haeckel. + +_Definition._--Surface of the outer shell covered with radial spines or +thorns. + + +4. _Tholonium hexonium_, n. sp. (Pl. 10, fig. 17). + +Outer shell ellipsoidal, without dome-shaped protuberances, covered with +numerous (thirty to fifty) thin and long, bristle-shaped radial spines; +network very delicate, irregular, with roundish pores. Inner shell with six +marked hemispherical domes of somewhat different sizes; pores regular, +circular, with prominent hexagonal frames, twice as broad as the bars; ten +to twelve on the basal semicircle of one cupola. + +_Dimensions._--Major axis of the outer shell 0.15, minor axis 0.14; major +axis of the inner shell 0.13, minor axis 0.12; pores 0.008, bars 0.004. + +_Habitat._--Pacific, central area, Station 271, depth 2425 fathoms. + + +5. _Tholonium sphaeronium_, n. sp. + +Outer shell very thin walled, spherical, without dome-shaped protuberances, +with smooth surface, excepting eight large radial spines, rising from the +eight corners of the inner cubical central chamber. Pores of the outer +shell very small, subcircular. Inner shell very thick walled, with six +marked hemispherical domes; pores subregular, circular, with prominent +hexagonal frames, twice as broad as the bars; six to eight on the +semicircle of one cupola. + +{680}_Dimensions._--Diameter of the spherical outer shell 0.15, inner shell +0.11; pores of the inner 0.01, bars 0.005. + +_Habitat._--Pacific, central area, Station 274, depth 2750 fathoms. + + + +Genus 299. _Cubotholus_,[339] n. gen. + +_Definition._--#Tholonida# with simple cortical shell (without external +veil), composed of six hemispherical cupolas, opposite in pairs on the +poles of three axes perpendicular one to another, covering six sides of the +cuboidal _Larnacilla_-shaped central chamber (with medullary shell). + +The genus _Cubotholus_ differs from _Tholocubus_ in the possession of a +medullary shell in the central chamber, and may be derived from this genus +by its production; but it may also be derived from _Staurotholus_ by +apposition of two opposite domes on the flat sides of the cross-shell. +Sometimes all six domes are of the same size and form, but commonly +different in pairs. + + + +Subgenus 1. _Cubotholissa_, Haeckel. + +_Definition._--Surface of the shell smooth or rough, without radial spines. + + +1. _Cubotholus regularis_, n. sp. (Pl. 10, fig. 14). + +On the six sides of the cubical central chamber six hemispherical cupolas +of the same size and form. Surface smooth. Pores regular, circular, twice +as broad as the bars; eight in the basal semicircle of each cupola. +Medullary shell apparently spherical (?), connected with the eight corners +of the central chamber by eight radial beams, regularly disposed. (This +species is remarkable for the perfect symmetry of the shell, the six sides +of which appear to be quite similar. It differs from the similar +_Tholocubus regularis_ in the possession of a medullary shell.) + +_Dimensions._--Diameter of the cortical shell (equal in all three dimensive +axes) 0.15; pores 0.01, bars 0.005; diameter of the medullary shell 0.04. + +_Habitat._--Pacific, central area, Station 273, depth 2350 fathoms. + + +2. _Cubotholus quadraticus_, n. sp. + +Surface of the shell smooth. Both principal cupolas (on the poles of the +longitudinal axis) larger than the four other cupolas, which have the same +size and lie cross-wise in the equatorial plane. (Therefore two of the +three fundamental axes equal, the third larger.) Pores subregular, +circular, three times as broad as the bars; ten to twelve in the semicircle +of each cupola-basis. + +_Dimensions._--Major axis 0.16, minor axis 0.12; pores 0.012, bars 0.004. + +_Habitat._--Indian Ocean, Zanzibar, Pullen; depth 2200 fathoms. + + +{681}3. _Cubotholus rhombicus_, n. sp. + +Surface of the shell smooth. Both principal cupolas (on the poles of the +longitudinal axis) larger than the two lateral (on the poles of the +transverse axis), and these larger than the two sagittal cupolas (on the +poles of the sagittal axis). Therefore all three fundamental axes unequal. +Pores irregular, roundish, twice to four times as broad as the bars; eight +to twelve in the basal semicircle of each cupola. Medullary shell +lentelliptical. + +_Dimensions._--Major (principal) axis 0.16, middle (lateral) axis 0.14, +minor (sagittal) axis 0.12; pores 0.006 to 0.012, bars 0.003. + +_Habitat._--South Atlantic, Station 335, depth 1425 fathoms. + + + +Subgenus 2. _Cubotholura_, Haeckel. + +_Definition._--Surface of the shell with radial spines or thorns. + + +4. _Cubotholus octoceras_, n. sp. + +All six cupolas in pairs of different sizes. Both principal domes larger +than the lateral domes, and these larger than the sagittal domes. Pores +subregular, circular, twice as broad as the bars; eight to ten in the +semicircle of each cupola. From the surface arise (at the intersecting +points of every three cupolas) eight strong conical radial spines, about as +long as the shell-axis; they lie in two diagonal planes, and are the +external free prolongations of eight inner beams (homologous with the eight +wing-spines of _Tetrapyle octacantha_), which connect the lentelliptical +medullary shell with the eight corners of the cuboidal central chamber. + +_Dimensions._--Major axis of the cortical shell 0.15, middle 0.13, minor +0.11; pores 0.008, bars 0.004; diameters of the medullary shell +corresponding to 0.05, 0.04, 0.03. + +_Habitat._--Western Tropical Pacific, Station 224, depth 1850 fathoms. + + + +Genus 300. _Cubotholonium_,[340] n. gen. + +_Definition._--#Tholonida# with double (or sometimes triple) cortical shell +(with external veil), composed of six hemispherical cupolas, opposite in +pairs on the poles of three axes perpendicular one to another, covering six +sides of the cuboidal _Larnacilla_-shaped central chamber (with medullary +shell). + +The genus _Cubotholonium_ differs from the nearly allied _Cubotholus_ (its +probable ancestral form) only in duplication of the cortical shell. I have +observed only two species of this rare form, both rather different. In the +first species the outer cortical shell forms a simple spherical thin veil +around the inner, the six cupolas of which are nearly of the same form and +size. In the second species each of the domes of the {682}inner cortical +shell is protected by an outer larger cupola, and besides this the whole +shell is enveloped by a thin ellipsoidal veil (Pl. 10, fig. 15). Therefore +this species may be the representative of a peculiar genus, the most highly +developed of all Tholonida--_Tholothauma_. + + +1. _Cubotholonium sphaeroides_, n. sp. + +Outer cortical shell (or veil) spherical, with smooth surface; network very +delicate, with very thin bars and very small irregular, roundish pores. +Inner cortical shell simple, composed of six hemispherical cupolas, +surrounding the six sides of the cubical central chamber, which encloses a +spherical medullary shell (one-third as large as itself). Network of the +inner cortical shell regular, with circular pores of the same breadth as +the bars, twelve to fourteen in the basal semicircle of one cupola. + +_Dimensions._--Diameter of the spherical outer shell 0.2, of the inner +cortical shell 0.15; pores and bars of the latter 0.006. + +_Habitat._--Indian Ocean, Zanzibar, Pullen, depth 2200 fathoms. + + +2. _Cubotholonium ellipsoides_, n. sp. (Pl. 10, fig. 15). + + _Tholothauma ellipsoides_, Haeckel, 1883, MS. + +Outer cortical shell (or veil) ellipsoidal, with very thin irregular +network and thorny surface. Inner cortical shell double, with six double, +flatly vaulted cupolas, surrounding the six sides of the +_Larnacilla_-shaped central chamber; the double domes of each shell are in +opposite pairs somewhat larger than the alternating pairs. Pores +subregular, circular, about the same breadth as the bars; eight to twelve +in the basal semicircle of one cupola. Central chamber with ellipsoidal +medullary shell. Radial spines short, very numerous. + +_Dimensions._--Major axis of the outer cortical shell 0.28, minor 0.24; +major axis of the inner cortical shell 0.16, minor axis 0.14; pores and +bars 0.006; medullary shell 0.03. + +_Habitat._--Pacific, central area, Station 271, depth 2425 fathoms. + + + +Family XXVIII. #ZONARIDA#, n. fam. (Pl. 50, figs. 9-12). + +_Definition._--#Larcoidea# with regular, completely latticed cortical +shell, distinguished by two to four or more annular constrictions, which +lie (all or partly) in the dimensive planes (sagittal, transverse, or +lateral), and by which four to eight or more vaulted cupolas or dome-like +chambers become separated. In the centre of this chambered cortical shell +lies constantly a trizonal or _Larnacilla_-shaped medullary shell. + +The family #Zonarida# comprises a small number of peculiar #Larcoidea#, +resembling the Tholonida in the composition of the polythalamous cortical +shell by a number of cupolas or dome-shaped protuberances. But the +disposition and origin of these latter {683}are quite different. Whilst in +the Tholonida the axes of the domes are dimensive axes, and these are +separated by annular constrictions lying in diagonal planes, in the +Zonarida we find the contrary; the axes of the domes are here diagonal +axes, and these are separated by annular constrictions lying in dimensive +planes. However, this definition agrees absolutely only in the +four-chambered _Zonarium_ and in the eight-chambered _Zonidium_, whilst in +the six chambered _Zoniscus_ only four domes are disposed according to this +law, two others, however, in the same manner as in the Tholonida. Therefore +this genus is intermediate between both families. + +_The Cortical Shell_ of the Zonarida is in all cases completely latticed +and of regular lentelliptical fundamental form, as in the nearly allied +Larnacida and Tholonida. The three dimensive axes are constantly of +different sizes, each with two equal poles; commonly (as in the human body) +the principal or longitudinal axis is the longest, the sagittal (or +dorso-ventral) axis the shortest; the transverse (or lateral) axis being +intermediate between them. Of the three dimensive planes the lateral plane +is the largest (determined by the principal and transverse axes); the +smallest is the equatorial plane (crossed by the transverse and sagittal +axes); the sagittal plane (determined by the sagittal and principal axes) +being intermediate between them. + +The annular constrictions of the cortical shell which produce the +dome-shaped protuberances are different in number in the three known +genera--two, three, or four. To each constriction often (but not always) +corresponds an internal latticed septum, which connects the cortical with +the medullary shell. The number of the cupolas is always double the number +of the annular constrictions by which they are separated, therefore four, +six, or eight. + +In all known Zonarida the sagittal septum is quite constant, but derived +from the original axial rod, which lies in the principal axis. By +ramification of this axial beam and reticular connection with the sagittal +girdle arises the sagittal septum, which we found first in _Octopyle_, +halving the four gates of _Tetrapyle_. Whilst this sagittal septum (between +right and left halves of the body) is common to all three known genera of +this family, the number and shape of the other annular constrictions are +different. In _Zonarium_ (Pl. 50, fig. 9) we find only one transverse +constriction (in the equatorial plane), in _Zoniscus_ (figs. 10, 11) two +parallel transverse constrictions (parallel to the equatorial plane, on +both sides of it). _Zonidium_ (fig. 12) is a combination of both foregoing +genera; it has three parallel transverse constrictions (one in the +equatorial plane, and one on each side of it). + +_The Latticed Domes_ (cupolas or chambers) of the cortical shell exhibit +correspondingly a different number and disposition in the three known +genera. In _Zonarium_ are found only four crossed chambers, separated by +the sagittal and transverse septa; the axes of the four crossed domes are +diagonal axes, whilst in the similar _Staurotholus_ they are dimensive axes +(principal and transverse axes). In _Zonidium_ we find eight domes, each +cupola of _Zonarium_ being halved by a diagonal septum. _Zoniscus_ is +intermediate {684}between the two foregoing genera, and has six cupolas, +three on each side of the sagittal septum. + +The inner communication of the cupolas or chambers is more or less free, +the lattice-work of the separating septa between them commonly remaining +more or less imperfect, or represented only by some isolated beams or +meshes. The outer network of the cupolas is commonly irregular (as in the +majority of #Larcoidea#), but sometimes distinguished by a small number of +regularly disposed larger apertures (similar to the "gates" of the +Pylonida). From the surface radial spines often arise in characteristic +number and symmetrical disposition, commonly as prolongations of the septal +axes or of the constricted edges. + +The _Medullary Shell_ in all Zonarida is a true trizonal or +_Larnacilla_-shaped lattice-shell (compare above, p. 600); its perimeter +(or the first lateral girdle) is sometimes more elliptical, at other times +more hexagonal; the hexagon is amphithect; both its lateral sides are often +concave and commonly longer than the four other sides. + +The _Central Capsule_ in all Zonarida is in a strict geometrical sense a +true lentellipsis (compare above, p. 599); its principal axis is commonly +one and a third to one and a half times as great as the transverse axis, +and twice to three times as great as the sagittal axis. The lentelliptical +central capsule encloses the trizonal medullary shell, whilst it is +externally enveloped by the chambered cortical shell. + +_Synopsis of the Genera of Zonarida._ + + Two annular constrictions and four cupolas, 301. _Zonarium_. + + Three annular constrictions and six cupolas, 302. _Zoniscus_. + + Four annular constrictions and eight cupolas, 303. _Zonidium_. + + + +Genus 301. _Zonarium_,[341] n. gen. + +_Definition._--#Zonarida# with four dome-shaped chambers of the cortical +shell, separated by two annular constrictions (one sagittal and one +transverse). + +The genus _Zonarium_ is the most simple form of the Zonarida, and differs +from the nearly allied _Larnacalpis_ by two ring-like constrictions, which +are crossed at right angles, one in the sagittal (or median) plane, and one +in the transverse (or equatorial) plane. By these two annular constrictions +four egg-shaped or kidney-shaped chambers become imperfectly separated, +which correspond to the quadrants of the lateral plane. The first cause of +the marked constrictions may be the formation of the latticed sagittal +septum, which is found first in _Octopyle_, as halving the four gates of +{685}_Tetrapyle_. Between this septum and the constricted narrow transverse +girdle the cortical shell grows out in the form of four vaulted cupolas; +every two opposite domes are congruent, two neighbouring are symmetrically +equal. + + +1. _Zonarium quadrigatum_, n. sp. + +Cortical shell quadrangular, one and a half times as long as broad, with +four rounded corners. Surface thorny, with numerous short radial spines. +Sagittal constriction twice as long as the hexagonal medullary shell. Four +cupolas kidney-shaped. + +_Dimensions._--Length of the cortical shell 0.16, breadth 0.11; length of +the medullary shell 0.06, breadth 0.04. + +_Habitat._--Pacific, central area, Station 272, depth 2600 fathoms. + + +2. _Zonarium quadrispinum_, n. sp. + +Cortical shell quadrangular, nearly rectangular, about twice as long as +broad, with four corners, from which arise four strong, three-sided +pyramidal, radial spines (crossed in two diagonals of the lateral plane). +Surface thorny, only smooth in the transverse constriction. Sagittal +constriction three times as long as the lentelliptical medullary shell. +Four cupolas elliptical or nearly quadrangular. + +_Dimensions._--Length of the cortical shell 0.22, breadth 0.1; length of +the medullary shell 0.07, breadth 0.05. + +_Habitat._--Pacific, central area, Station 274, depth 2750 fathoms. + + +3. _Zonarium octangulum_, n. sp. (Pl. 50, fig. 9). + +Cortical shell octangular, one and a fourth times as long as broad, with +eight strong conical spines on the eight corners; these are separated by +four deep constrictions on the poles of the principal and transverse axes, +and by four truncated planes on the poles of the crossed diagonal axes +between the former. Sagittal constriction twice as long as the hexagonal +medullary shell. Four cupolas kidney-shaped or nearly pentagonal. + +_Dimensions._--Length of the cortical shell 0.15, breadth 0.12; length of +the medullary shell 0.07, breadth 0.04. + +_Habitat._--Pacific, central area, Station 271, depth 2425 fathoms. + + +4. _Zonarium tetratholium_, n. sp. + +Cortical shell quadrangular, with four rounded corners. Surface thorny, +with sixteen stronger radial spines; eight of these lie in the lateral +plane, in the same symmetrical disposition as in the foregoing species; +eight others lie on both sides of the lateral plane, opposite in pairs in +two crossed diagonal planes, in the same symmetrical disposition as in +_Tetrapyle octacantha_. Sagittal {686}constriction three times as long as +the lentelliptical medullary shell. Four cupolas obliquely elliptical. + +_Dimensions._--Length of the cortical shell 0.16, breadth 0.12; length of +the medullary shell 0.04, breadth 0.03. + +_Habitat._--North Pacific, Station 241, depth 2300 fathoms. + + + +Genus 302. _Zoniscus_,[342] n. gen. + +_Definition._--#Zonarida# with six dome-shaped chambers of the cortical +shell, separated by three annular constrictions (one sagittal and two +transverse, parallel to the equatorial plane). + +The genus _Zoniscus_ differs from _Zonarium_ as well as from _Zonidium_ by +the development of the transverse girdle, which is not constricted, but on +the contrary prominently vaulted in the equatorial plane. Therefore both +wings of the transverse girdle form here two opposite lateral or +"equatorial cupolas," as in _Amphitholus_. These are separated from four +other domes (the "corner cupolas") by two transverse annular constrictions, +which correspond to the free edges of the original transverse girdle. The +corner domes of each pair are separated from each other by the sagittal +septum. + + +1. _Zoniscus rectangulus_, n. sp. + +Cortical shell nearly rectangular, with rounded corners, nearly one and a +half times as long as broad. Surface thorny, without larger radial spines. +Sagittal constriction scarcely half as long as the hexagonal medullary +shell. Both equatorial cupolas (or wings of the transverse girdle) scarcely +half as large as the four corner cupolas. + +_Dimensions._--Length of the cortical shell 0.15, breadth 0.11; length of +the medullary shell 0.07, breadth 0.045. + +_Habitat._--North Pacific, Station 253, depth 3125 fathoms. + + +2. _Zoniscus hexathalamus_, n. sp. + +Cortical shell nearly elliptical, one and a third times as long as broad. +Surface nearly smooth, without radial spines. Sagittal constriction three +times as long as the lentelliptical medullary shell. Both equatorial +cupolas about as large as the four corner cupolas. + +_Dimensions._--Length of the cortical shell 0.12, breadth 0.09; length of +the medullary shell 0.035, breadth 0.025. + +_Habitat._--North Pacific, Station 244, depth 2900 fathoms. + + +{687}3. _Zoniscus tetracanthus_, n. sp. (Pl. 50, fig. 10). + +Cortical shell nearly quadrangular, one and a half times as long as broad, +with four prominent corners, from which arise in the lateral plane four +strong, three-sided pyramidal radial spines (opposite in pairs in two +crossed diagonal axes). Surface thorny, with exception of the concave +lateral sides. Sagittal constriction two and a half times as long as the +hexagonal medullary shell. Both equatorial cupolas scarcely half as large +as the four corner cupolas. + +_Dimensions._--Length of the cortical shell 0.18, breadth 0.12; length of +the medullary shell 0.07, breadth 0.04. + +_Habitat._--Pacific, central area, Station 271, depth 2425 fathoms. + + +4. _Zoniscus octacanthus_, n. sp. + +Cortical shell nearly four-sided, prismatic, one and a third times as long +as broad, with spiny surface. Eight longer thin radial spines opposite in +pairs in two crossed diagonal planes (as in _Tetrapyle octacantha_). +Sagittal constriction two and a half times as long as the hexagonal +medullary shell. Both equatorial cupolas somewhat larger than the four +corner cupolas. + +_Dimensions._--Length of the cortical shell 0.16, breadth 0.12; length of +the medullary shell 0.055, breadth 0.04. + +_Habitat._--Pacific, central area, Station 263, depth 2650 fathoms. + + +5. _Zoniscus hexatholius_, n. sp. (Pl. 50, fig. 11). + +Cortical shell nearly rectangular, with four rounded corners and deep +sagittal constriction, one and a fourth times as long as broad with thorny +surface. Twelve longer edged radial spines; eight opposite in pairs in two +crossed diagonal planes (as in the foregoing species), four others in the +lateral plane, opposite in pairs on both sides of the sagittal +constriction, which is scarcely twice as long as the hexagonal, in the +equatorial plane constricted medullary shell. Both equatorial cupolas +nearly of the same size as the four corner cupolas. + +_Dimensions._--Length of the cortical shell 0.16, breadth 0.13; length of +the medullary shell 0.07, breadth 0.04. + +_Habitat._--South Pacific, Station 300, depth 1375 fathoms. + + + +Genus 303. _Zonidium_,[343] n. gen. + +_Definition._--#Zonarida# with eight dome-shaped chambers of the cortical +shell, separated by four annular constrictions (one sagittal, one +transverse, and two others parallel to the latter). + +The genus _Zonidium_ must be regarded as a _Zonarium_, in which the four +cupolas (in the quadrants of the lateral plane) are halved by diagonal +beams or latticed septa, {688}lying opposite in pairs in two crossed +diagonal planes. Therefore the number of the septa (four) and the domes +(eight) is here doubled. Among the eight cupolas we distinguish four median +(on both sides of the sagittal plane) and four lateral (on both sides of +the equatorial plane); both groups are of different size and form. Probably +_Zonidium_ is derived from _Zonarium_ by lattice-connection between the +eight diagonal wing-spines, which in both species of this genus are +present, the same as in _Tetrapyle octacantha_. + + +1. _Zonidium octostylium_, n. sp. + +Cortical shell nearly quadrangular, with rounded corners and thorny +surface. Eight long and thin radial spines on both sides of the lateral +plane opposite in pairs and lying in two crossed diagonal planes (as in +_Tetrapyle octacantha_). Sagittal constriction three times as long as the +lentelliptical medullary shell. Four medial cupolas (on both sides of the +sagittal plane) somewhat larger than the four lateral cupolas (on both +sides of the equatorial plane). + +_Dimensions._--Length of the cortical shell 0.15, breadth 0.12; length of +the medullary shell 0.05, breadth 0.03. + +_Habitat._--Indian Ocean, Madagascar, Rabbe, surface. + + +2. _Zonidium octotholium_, n. sp. (Pl. 50, fig. 12). + +Cortical shell nearly octangular, with spiny surface; twenty long and stout +radial spines between numerous smaller spines; eight wing-spines opposite +in pairs in two crossed diagonal planes (as in the preceding species); +twelve other strong spines in the lateral plane (four longer opposite in +pairs on the poles of the principal and transverse axes, eight others +smaller, alternating between these and the diagonal spines). Sagittal +constriction twice as long as the hexagonal medullary shell. Four median +cupolas somewhat smaller than the four lateral cupolas. + +_Dimensions._--Length of the cortical shell 0.18, breadth 0.15; length of +the medullary shell 0.07, breadth 0.05. + +_Habitat._--Indian Ocean, Zanzibar, Pullen, depth 2200 fathoms. + + + +Family XXIX. #LITHELIDA#, Haeckel (Pl. 49, figs. 1-7). + +_Lithelida_, Haeckel, 1862, Monogr. d. Radiol., p. 515. + +_Definition._--#Larcoidea# with symmetrical spiral shell, divided by the +spiral plane into two symmetrical halves; all windings of the spiral lie in +this plane. Primordial chamber either simple or _Larnacilla_-shaped. + +The family #Lithelida# comprises all those #Larcoidea# in which the growth +of the latticed shell is spirally winding in one plane, _Nautilus_-like. +They agree in the spiral growth with the following family. But in the +Streblonida the spiral is screw-shaped, {689}ascending (like _Helix_). +Therefore in these latter the geometrical fundamental form of the shell is +asymmetrical or "dysdipleural," whereas in the Lithelida +bilateral-symmetrical or "eudipleural." The lentelliptical or nearly +spherical shell may be divided by a median section into two symmetrical +halves; the right half is the mirror image of the left half. + +When in 1862 I founded the family Lithelida in my Monograph (p. 515), I +knew only one genus, _Lithelius_, with two species. The rich material of +the Challenger collection contains a great number of similar spirally +constructed #Larcoidea#, so that at the present time we may distinguish at +least six genera. These belong to two different subfamilies, which may +possibly be afterwards better separated as families. The first subfamily, +Spiremida, possess a simple, spherical or subspherical, medullary shell; +the second subfamily, Larcospirida, possess a trizonal or +_Larnacilla_-shaped medullary shell. No doubt these latter must be derived +from Pylonida, as we observe all stages of development starting from a +simple _Trizonium_; but perhaps also the Spiremida have the same origin, +their simple, spherical or subspherical, medullary shell being derived from +a trizonal or _Larnacilla_-shaped medullary shell by reduction. + +The general appearance in both subfamilies of the Lithelida is quite the +same, and it requires a careful study of the medullary shell to distinguish +certainly the Spiremida from the Larcospirida. This distinction is often +not easy, particularly in the larger forms; the shell is often very opaque +and difficult to understand. Only in one position, if the spiral axis be +parallel to the axis of the eye of the observer, and the spiral plane be +therefore fully seen in the optical plane of the microscope, the spiral +line (or the axial section of the latticed spiral lamella) is distinctly +observed; in all other positions the figure of the spiral is more or less +indistinct, and the whole microscopical image often quite intricate and +confused. The sufficient study of this family requires therefore the +contemplation of the shell from different sides, and is the more difficult, +as the variability of the Lithelida--as of the Pylonida--is extraordinarily +great. + +The description which I gave of _Lithelius_ (1862) in my Monograph is in +some points erroneous, and was afterwards (1879) corrected by R. Hertwig, +who explained particularly the near relation of it to _Tetrapyle_. Indeed +the intermediate forms between the Lithelida and the Pylonida are so +numerous and so evident in all stages of development, that the derivation +of the former (at least of the Larcospirida) from the latter is quite +clear. The analogy between the structure of the Lithelida and the +calcareous (foraminiferous) Alveolinida is not so complete as I supposed it +to be in my Monograph (1862); particularly the formation of the small +chambers between the turnings of the spiral lamella is much more complete +in the Alveolinida than in the Lithelida. + +The cortical shell of all Lithelida has the same geometrical fundamental +form as _Nautilus_ or as the nautiloid Polythalamia (_Polystomella_, +_Nummulites_, &c.); therefore the shell is dipleural, being divided by the +median plane into two symmetrical lateral halves. {690}Since the spiral +line lies in the median plane, we will call it the spiral plane; it +separates the right half from the left. The axis of the body, around which +the spiral turns (without touching it), is the spiral axis. The latticed +part of the cortical shell, which turns around them, is the spiral lamella. +Only in one genus of our family, viz., _Tholospira_, are the spiral axis, +the lateral axis, the spiral plane, and the sagittal plane quite as in +_Nautilus_. In all other genera this disposition is different or is +uncertain. This depends on the different part of the cortical shell, from +which the spiral growth begins. In this respect we can distinguish four +different modes. + +In the Larcospirida (or the Lithelida with _Larnacilla_-shaped medullary +shell) the spiral growth exhibits four quite different forms. It begins +here with _Larcospira_, in which already the first cortical girdle of the +Diplozonaria determines the spiral growth; one wing of this girdle, the +transverse girdle of _Amphipyle_, grows more swiftly than the other, +overgrows it, and thus turns around the principal axis. In _Pylospira_ the +first or transverse girdle is already perfectly formed (as in _Amphipyle_), +and the spiral growth is introduced by the second or lateral girdle of +_Tetrapyle_; one wing of it (the right or the left) grows more swiftly than +the other, overgrows it, and thus turns around the sagittal axis. In +_Tholospira_ also the second girdle is complete, and the spiral growth +begins from the third or sagittal girdle. One of its wings grows more +swiftly than the other, overgrows it, and thus turns around the transverse +axis. Consequently we see that each of the three dimensive planes of the +lentelliptical Larcoid-body may be the spiral plane: in _Larcospira_ the +transverse plane, in _Pylospira_ the lateral plane, in _Tholospira_ the +sagittal plane. Correspondingly the spiral axis in the first genus is the +principal, in the second the sagittal, in the third the transverse axis of +the central _Larnacilla_-shell. Therefore in these three genera the spiral +plane is the plane of the latticed girdle, which determines the spiral +growth, one of both its wings overgrowing the other. + +In each of the three above mentioned genera the spiral may be simple or +double; it remains simple if only one of both wings of the turning girdle +overgrow the other, and this latter remain a simple half girdle (or +tube-like wing). Whereas the spiral becomes double if the second wing of +the girdle afterwards follow the example of the first wing and now turn +around it in the same direction. As this happens in all three genera, we +can subdivide them into six subgenera. + +A quite peculiar form of spiral growth is produced in _Spironium_, in which +the direction of growth in both lateral wings of the transverse girdle is +inverse from the beginning. The left wing grows against the posterior, the +right wing against the anterior pole of the principal axis, turning around +it in crossed, eight-like spirals. The whole shell afterwards assumes a +lentelliptical form. + +Commonly between the embracing spiral turnings or convolutions a great +number of radial beams is developed, irregularly disposed and often +branching; they support the {691}thin spiral lamellae and give to the whole +shell more solidity. Often these beams form imperfect radial septa, by +which the spiral cavity of the turnings is divided into a variable number +of chambers. But these chambers never become so regular and perfect as in +the analogous nautiloid Polythalamia. + +In many Lithelida the growth of the shell reaches a certain limit, +concluding with the formation of a superficial latticed lamella of +lentelliptical or nearly spherical form. In many other forms of the family +this seems not to be the case; but these may possibly be younger forms, +afterwards reaching the same limit. + +The network of the shell in the Lithelida is commonly quite irregular, and +so variable that its special conformation has usually no value in the +determination of the species. The surface of the shell is often covered +with radial spines, which are sometimes arborescent. + +The central capsule seems always to preserve the same lentelliptical form +(or triaxial ellipsoid) as in all other #Larcoidea#. With the increase of +growth it encloses successively a larger part of the spiral cortical shell, +but on the outside is constantly protected by the last turnings of the +spiral, or by the lattice-lamella of the surface. + +_Synopsis of the Genera of Lithelida._ + + ------------------------------------------------------------------------- + I. Subfamily Spiremida. + Central medullary shell simple, spherical or lentelliptical. + ------------------------------------------------------------------------- + Surface of the cortical shell smooth or thorny, + without radial spines, 304. _Spirema_. + + Surface of the cortical shell covered with numerous + simple or branched radial spines, 305. _Lithelius_. + ------------------------------------------------------------------------- + II. Subfamily Larcospirida. + Central medullary shell double, trizonal or _Larnacilla_-shaped. + ------------------------------------------------------------------------- + The transverse girdle turns around the principal axis, 306. _Larcospira_. + + The lateral girdle turns around the sagittal axis, 307. _Pylospira_. + + The sagittal girdle turns around the transverse axis, 308. _Tholospira_. + + Both wings of the transverse girdle turn around the + principal axis in an opposite diagonal direction, 309. _Spironium_. + + + +Subfamily 1. SPIREMIDA, Haeckel, 1881, Prodromus, p. 464. + +_Definition._--#Lithelida# with simple, spherical or subspherical, +medullary shell. + + + +Genus 304. _Spirema_,[344] Haeckel, 1881, Prodromus, p. 464. + +_Definition._--#Lithelida# with simple, spherical or subspherical, +medullary shell, and lentelliptical or subspherical, spirally constructed +cortical shell; surface smooth or thorny, without radial spines. + +{692}The genus _Spirema_ begins the series of the Spiremida, or of those +Lithelida in which the medullary shell presents a simple latticed sphere or +ellipsoid, never composed of a double, trizonal or _Larnacilla_-shaped +shell. In the present state of our knowledge we cannot say whether this +simple medullary shell be a primary formation, or effected by secondary +means, by reduction of a double _Larnacilla_-shaped medullary shell, which +is constantly found in the Larcospirida. The species of this genus (as of +all Lithelida) are difficult to distinguish, are transformistic, and +incline very much to variations and abnormalities. The spiral may be simple +or double. + + + +Subgenus 1. _Spiremarium_, Haeckel. + +_Definition._--Spiral convolutions of the cortical shell simple. + + +1. _Spirema lentellipsis_, n. sp. + +Cortical shell lentelliptical, with smooth surface; proportion of its three +dimensive axes = 4 : 5 : 6. In the median plane are visible four perfect +turnings of the simple spiral, the breadth of which gradually increases +towards the third convolution, finally decreasing; the broadest (third) +turning three times as broad as the simple spherical medullary shell. + +_Dimensions._--Length of the lentelliptical cortical shell 0.18, breadth +0.15, height 0.12; diameter of the spherical medullary shell 0.02. + +_Habitat._--North Atlantic, Station 353, surface. + + +2. _Spirema melonia_, n. sp. (Pl. 49, fig. 1). + +Cortical shell nearly spherical, with smooth surface; proportion of its +three dimensive axes = 1.4 : 1.5 : 1.6. In the median plane are visible +three perfect turnings of the simple spiral, all of the same breadth as the +simple spherical medullary shell; the breadth of each convolution somewhat +greater at the poles of the principal than at the poles of the sagittal +axis. + +_Dimensions._--Length of the shell 0.16, breadth 0.15, height 0.14; +medullary shell 0.018. + +_Habitat._--Pacific, central area, Station 271, surface. + + +3. _Spirema flustrella_, Haeckel. + + _Flustrella haliomma_, Ehrenberg (1861), Abhandl. d. k. Akad. d. Wiss. + Berlin, 1872, p. 293, Taf. ii. fig. 6. + +Cortical shell egg-shaped, with thorny surface; proportion of its three +axes = 4 : 5 : 6. In the median plane are visible three perfect turnings of +the simple spiral, the first and second of about the same breadth as the +simple spherical medullary shell, the third suddenly increasing, and +finally three to four times as broad. Network of the surface irregular, +with roundish pores. + +_Dimensions._--Length of the shell 0.2, breadth 0.17, height 0.14; +medullary shell 0.013. + +_Habitat._--North Atlantic, Greenland, 1000 fathoms, Ehrenberg; Faeroee +Channel, John Murray. + + + +{693}Subgenus 2. _Spiremidium_, Haeckel. + +_Definition._--Spiral convolutions of the cortical shell double. + + +4. _Spirema diplospira_, n. sp. + +Cortical shell lentelliptical, with smooth surface; proportion of its three +dimensive axes = 6 : 7 : 8. In the median plane are visible three perfect +turnings of a double spiral, the breadth of which gradually increases; the +broadest (third) convolution three times as broad as the simple +lentelliptical medullary shell. + +_Dimensions._--Length of the shell 0.24, breadth 0.21, height 0.18; +medullary shell 0.02. + +_Habitat._--Tropical Pacific, Philippines, Station 200, depth 250 fathoms. + + +5. _Spirema subglobosum_, n. sp. + +Cortical shell nearly spherical, with thorny surface; proportion of its +three axes = 2 : 2.1 : 2.2. In the median plane are visible two perfect +turnings of a double spiral, the breadth of which in the second convolution +is four times as great as that of the first convolution and the simple +spherical medullary shell. + +_Dimensions._--Length of the shell 0.22, breadth 0.21, height 0.2; +medullary shell 0.02. + +_Habitat._--Tropical Atlantic, off Sierra Leone, Station 348, depth (2450) +fathoms. + + + +Genus 305. _Lithelius_,[345] Haeckel, 1862, Monogr. d. Radiol., p. 519. + +_Definition._--#Lithelida# with simple, spherical or subspherical, +medullary shell, and lentelliptical or subspherical, spirally constructed +cortical shell; surface covered with numerous, simple or branched, radial +spines. + +The genus _Lithelius_, founded by me in 1862, and represented by two +Mediterranean species, was at that time the only known form of this family, +which now contains six genera and twenty-seven species. It differs from the +foregoing _Spirema_ in the possession of numerous radial spines on the +surface. These may be either simple or branched. The spiral may be simple +or double, and according to this latter modification we distinguish two +different subgenera. + + + +Subgenus 1. _Lithospira_, Haeckel. + +_Definition._--Spiral convolutions of the cortical shell simple. + + +1. _Lithelius spiralis_, Haeckel. + + _Lithelius spiralis, Haeckel_, 1862, Monogr. d. Radiol., p. 519, Taf. + xxvii. figs. 6, 7. + +Cortical shell lentelliptical, one and a third times as long as broad, +covered with very numerous (one hundred to one hundred and fifty or more) +simple, bristle-shaped radial spines, about as long {694}as the shell. +Spiral turnings simple, all nearly of the same breadth and scarcely broader +than the simple spherical medullary shell. + +_Dimensions._--Length of the cortical shell (with six spiral convolutions) +0.15, breadth 0.13; diameter of the medullary shell 0.012. + +_Habitat._--Mediterranean, Messina, Haeckel, surface; Atlantic, Stations +348 to 353, surface. + + +2. _Lithelius primordialis_, R. Hertwig. + + _Lithelius primordialis_, R. Hertwig, 1879, Organism. d. Radiol., p. 54, + Taf. vi. figs. 4, 4_a_. + +Cortical shell subspherical, covered with numerous simple, bristle-shaped +radial spines, longer than the shell. Spiral turnings simple, with +gradually increasing breadth, so that the beginning of the third spiral is +twice as broad as the first and as the simple spherical medullary shell. + +_Dimensions._--Diameter of the cortical shell (with two spiral +convolutions) 0.12; diameter of the medullary shell 0.02. + +_Habitat._--Mediterranean, Messina, R. Hertwig, surface. + + +3. _Lithelius alveolina_, Haeckel, 1862. + + _Lithelius alveolina_, Haeckel, 1862, Monogr. d. Radiol., p. 520, Taf. + xxvii. figs. 8, 9. + +Cortical shell spherical, covered with simple, very numerous (two hundred +to three hundred or more), short, bristle-shaped radial spines, scarcely +half as long as the radius of the shell. Spiral turnings simple, with +gradually increasing breadth, so that the beginning of the third spiral is +three times as broad as the first and as the simple spherical medullary +shell. + +_Dimensions._--Diameter of the cortical shell (with four spiral +convolutions) 0.2; diameter of the medullary shell 0.01. + +_Habitat._--Cosmopolitan; Mediterranean, Atlantic, Pacific, on many +Stations, surface. + + +4. _Lithelius capreolus_, n. sp. + +Cortical shell lentelliptical, one and a fourth times as long as broad, +covered with numerous (eighty to one hundred and twenty or more) short, +branched radial spines, about half as long as the radius of the shell; each +spine once or twice dichotomous, with curved divergent branches. Spiral +turnings simple, with gradually increasing breadth, so that the beginning +of the third spiral is twice as broad as the first, and as the simple +spherical medullary shell. + +_Dimensions._--Length of the cortical shell (with four spiral convolutions) +0.18, breadth 0.14; diameter of the medullary shell 0.015. + +_Habitat._--Pacific, central area, Station 274, surface. + + + +Subgenus 2. _Drymospira_, Haeckel, 1881, Prodromus, p. 464. + +_Definition._--Spiral convolutions of the cortical shell double. + + +{695}5. _Lithelius solaris_, n. sp. (Pl. 49, fig. 2). + +Cortical shell spherical, covered with simple, very numerous (two hundred +to three hundred) bristle-shaped radial spines, longer than the diameter of +the shell. Spiral turnings double, both of the same breadth, gradually +increasing with the growth of the shell and several times surpassing the +diameter of the simple spherical medullary shell. (Pl. 49, fig. 2, exhibits +only the first convolutions in the centre of the shell.) + +_Dimensions._--Diameter of the cortical shell (with four spiral +convolutions) 0.18; diameter of the medullary shell 0.02. + +_Habitat._--Pacific, central area, Stations 266 to 272, surface and in +various depths. + + +6. _Lithelius arborescens_, n. sp. + +Cortical shell lentelliptical, one and a half times as long as broad, +covered with numerous (fifty to eighty or more) branched radial spines, +about as long as the greatest diameter of the shell; each spine with two to +four lateral branches, which are again branched or dichotomous. Spiral +turnings double, both of little different breadth, which increases +considerably with the growth of the shell, so that the third turn is four +times as broad as the simple spherical medullary shell. + +_Dimensions._--Length of the cortical shell (with three spiral +convolutions) 0.18, breadth 0.12; diameter of the medullary shell 0.01. + +_Habitat._--North Atlantic, Faeroee Channel, surface, John Murray. + + + +Subfamily 2. LARCOSPIRIDA, Haeckel. + +_Definition._--#Lithelida# with double, trizonal, or _Larnacilla_-shaped +medullary shell. + + + +Genus 306. _Larcospira_,[346] n. gen. + +_Definition._--#Lithelida# with double, trizonal, or _Larnacilla_-shaped +medullary shell; cortical shell subspherical or lentelliptical, constructed +of a simple or double spiral of the transverse girdle (or primary cortical +girdle); the spiral lamella revolving around the principal axis. + +The genus _Larcospira_ begins the interesting series of the Larcospirida, +or of those Lithelida in which the medullary shell is formed by a trizonal +or _Larnacilla_-shaped lattice-shell, and the cortical shell by spiral +turnings of one of the three girdles, which compose the cortical shell of +the Pylonida. In _Larcospira_, as the oldest and most simple form of +Larcospirida, the spiral is formed by the transverse girdle, or the first +girdle of the Diplozonaria, the only cortical girdle of _Amphipyle_. If in +this genus one of both wings of the transverse girdle grow stronger than +the other and overgrow the latter, turning {696}around the principal axis, +we reach the characteristic form of _Larcospirema_, the first subgenus of +_Larcospira_; but if afterwards the second wing follow the example of the +first, and overgrow it from the other side, we reach the typical form of +the second subgenus, _Larcospironium_. In this latter subgenus the spiral +becomes double, whilst in the former it remains simple. + + + +Subgenus 1. _Larcospirema_, Haeckel. + +_Definition._--Spiral convolutions or turns of the cortical shell simple; +only one single wing of the transverse girdle turning around the principal +axis. + + +1. _Larcospira lentelliptica_, n. sp. + +Cortical shell with smooth surface, four times as long as the +lentelliptical medullary shell. Perimeter of the lateral plane elliptical, +one and a half times as long as broad, without constrictions. One lateral +wing of the transverse girdle is more strongly developed and turns around +the other in two to three simple spiral turns. + +_Dimensions._--Length of the cortical shell 0.2, breadth 0.16; length of +the medullary shell 0.05, breadth 0.04. + +_Habitat._--Pacific, central area, Station 265, depth 2900 fathoms. + + +2. _Larcospira quadrangula_, n. sp. (Pl. 49, fig. 3). + +Cortical shell with thorny surface, three times as long as the +lentelliptical medullary shell. Perimeter of the lateral plane nearly +quadrangular, with four rounded corners (on the poles of two crossed +diagonal axes), one and a third times as long as broad, with one sagittal +constriction at the poles of the principal axis. One lateral wing of the +transverse girdle turns around the other in one and a half to two simple +spiral turns. + +_Dimensions._--Length of the cortical shell 0.18, breadth 0.14; length of +the medullary shell 0.06, breadth 0.04. + +_Habitat._--Pacific, central area, Station 274, depth 2750 fathoms. + + +3. _Larcospira sexangula_, n. sp. + +Cortical shell with spiny surface, four times as long as the hexagonal +medullary shell. Perimeter of the lateral plane nearly hexagonal, one and a +half times as long as broad, with six rounded corners (two on the poles of +the principal axis, four on the poles of two crossed diagonal axes), with +three slight ring-like constrictions. One lateral wing of the transverse +girdle turns around the other in two to two and a half simple spiral turns. + +_Dimensions._--Length of the cortical shell 0.24, breadth 0.16; length of +the medullary shell 0.06, breadth 0.04. + +_Habitat._--Pacific, central area, Station 271, depth 2425 fathoms. + + + +{697}Subgenus 2. _Larcospironium_, Haeckel. + +_Definition._--Spiral convolutions or turns of the cortical shell double; +both wings of the transverse girdle turning around the principal axis. + + +4. _Larcospira oliva_, n. sp. + +Cortical shell with smooth surface, six times as long as the lentelliptical +medullary shell. Perimeter of the lateral plane elliptical, one and a +fourth times as long as broad, without constrictions. Both lateral wings of +the transverse girdle turn round one another and form one and a half to two +double spiral turns. + +_Dimensions._--Length of the cortical shell 0.25, breadth 0.2; length of +the medullary shell 0.04, breadth 0.035. + +_Habitat._--Antarctic Ocean, Station 157, depth 1950 fathoms. + + + +Genus 307. _Pylospira_,[347] n. gen. + +_Definition._--#Lithelida# with double, trizonal or _Larnacilla_-shaped +medullary shell; cortical shell subspherical or lentelliptical, constructed +of a single or double spiral of the lateral girdle (or second cortical +girdle); the spiral lamella revolving round the sagittal axis. + +The genus _Pylospira_ follows after _Larcospira_ as the second genus of +Larcospirida; but in this latter the spiral of the cortical shell is formed +by the transverse girdle (or the first lattice-girdle of the Diplozonaria), +whilst in _Pylospira_ it is produced by the lateral girdle, or the second +lattice-girdle of that group. Therefore _Pylospira_ may be derived +phylogenetically from _Tetrapyle_ in the same manner as _Larcospira_ from +_Amphipyle_. Whilst in this latter the first cause of the spiral turning, +the unequal growth of both girdle-wings, proceeds from the transverse +girdle, in _Pylospira_ it proceeds from the lateral girdle. One of its +wings overgrows the other, turning around the sagittal axis. If the second +wing do not become developed, the spiral remains simple and represents the +subgenus _Pylospirema_; but if afterwards the second wing follow the +example of the first and overgrow it from the other side, we reach the +typical form of the second subgenus, _Pylospironium_, with a double spiral. + + + +Subgenus 1. _Pylospirema_, Haeckel. + +_Definition._--Spiral convolutions or turns of the cortical shell simple, +only one single wing of the lateral girdle turning around the sagittal +axis. + + +{698}1. _Pylospira tetrapyle_, n. sp. + +Cortical shell with thorny surface, five times as long as the +lentelliptical medullary shell. Perimeter of the lateral plane elliptical, +one and a half times as long as broad. Four internal gates (as in +_Tetrapyle_, between the complete lateral wings of the transverse girdle) +kidney-shaped. One principal wing of the lateral girdle turns around the +other in one and a half to two simple spiral turns. + +_Dimensions._--Length of the cortical shell 0.21, breadth 0.15; length of +the medullary shell 0.04, breadth 0.03. + +_Habitat._--Pacific, central area, Station 268, depth 2900 fathoms. + + +2. _Pylospira octopyle_, n. sp. (Pl. 49, fig. 4). + +Cortical shell with thorny surface, three times as long as the +lentelliptical medullary shell. Perimeter of the lateral plane elliptical +or nearly hexagonal, with four rounded corners (on the poles of two crossed +diagonal axes), one and a third times as long as broad. Eight internal +egg-shaped gates (as in _Octopyle_), between the complete lateral wings of +the transverse girdle, and two axial beams in the principal axis. One +single wing of the lateral girdle turns around the other in two to three +simple spiral turns. + +_Dimensions._--Length of the cortical shell 0.18, breadth 0.14; length of +the medullary shell 0.06, breadth 0.035. + +_Habitat._--North Pacific, Station 253, depth 3125 fathoms. + + + +Subgenus 2. _Pylospironium_, Haeckel. + +_Definition._--Spiral convolutions or turns of the cortical shell double; +both wings of the lateral girdle turning around the sagittal axis. + + +3. _Pylospira cymbium_, n. sp. + +Cortical shell with smooth surface, seven times as long as the +lentelliptical medullary shell. Perimeter of the lateral plane elliptical, +one and a third times as long as broad. Four internal kidney-shaped gates +between the complete lateral wings of the transverse girdle (as in +_Tetrapyle_). Both principal wings of the lateral girdle turn round one +another in two to two and a half double spiral turns. + +_Dimensions._--Length of the cortical shell 0.22, breadth 0.17; length of +the medullary shell 0.03, breadth 0.025. + +_Habitat._--Indian Ocean, Madagascar, Rabbe, surface. + + + +{699}Genus 308. _Tholospira_,[348] n. gen. + +_Definition._--#Lithelida# with double, trizonal or _Larnacilla_-shaped +medullary shell; cortical shell subspherical or lentelliptical constructed +of a simple or double spiral of the sagittal girdle (or third cortical +girdle); the spiral lamella revolving around the transverse axis. + +The genus _Tholospira_ represents the third genus of Larcospirida. Whilst +the spiral growth of the cortical shell is produced in _Larcospira_ by the +first (transverse) girdle of the Diplozonaria, in _Pylospira_ by the second +(lateral) girdle, in _Tholospira_ it is effected by the third or sagittal +girdle, which we found complete in _Pylonium_. If in this genus one wing of +the sagittal girdle overgrow the other remaining one and turn around the +transverse axis, we get _Tholospirema_, the first subgenus of our genus, +with simple spiral; but if afterwards the second wing follow the example of +the first, and overgrow it from the other side, we get _Tholospironium_, +with double spiral. + + + +Subgenus 1. _Tholospirema_, Haeckel. + +_Definition._--Spiral convolutions or turns of the cortical shell simple, +only one single wing of the sagittal girdle turning around the transverse +axis. + + +1. _Tholospira nautiloides_, n. sp. + +Cortical shell with smooth surface, five times as long as the +lentelliptical medullary shell. Perimeter of the lateral plane elliptical, +one and a half times as long as broad. Four internal kidney-shaped gates +(between the lateral wings of the transverse girdle, as in _Tetrapyle_). +One wing of the sagittal girdle turns around the other in two to two and a +half simple spiral turns. + +_Dimensions._--Length of the cortical shell 0.24, breadth 0.18; length of +the medullary shell 0.05, breadth 0.04. + +_Habitat._--Indian Ocean, between Ceylon and Socotra, Haeckel, surface. + + +2. _Tholospira spinosa_, n. sp. + +Cortical shell covered with numerous (sixty to eighty or more) simple, +bristle-like radial spines, about the length of the shell. Perimeter of the +lateral plane nearly quadrangular, with four rounded corners (on the poles +of two crossed diagonal axes), one and a half times as long as broad. Eight +internal egg-shaped gates (between the lateral wings of the transverse +girdle and two axial {700}beams in the principal axes, as in _Octopyle_). +One wing of the sagittal girdle turns around the other in two to three +simple spiral turns. + +_Dimensions._--Length of the cortical shell 0.27, breadth 0.18; length of +the medullary shell 0.04, breadth 0.03. + +_Habitat._--South Pacific, Station 288, surface. + + +3. _Tholospira dendrophora_, n. sp. (Pl. 49, fig. 6). + +Cortical shell covered with numerous (forty to fifty or more) branched +radial spines, about half as long as the shell; each spine with two to six +dichotomous branches. Perimeter of the lateral plane elliptical, one and a +third times as long as broad. Eight internal egg-shaped gates, as in the +foregoing species. One single wing of the sagittal girdle turns around the +other in three to four spiral turns. + +_Dimensions._--Length of the cortical shell 0.22, breadth 0.17; length of +the medullary shell 0.05, breadth 0.04. + +_Habitat._--Pacific, central area, Station 272, depth 2600 fathoms. + + + +Subgenus 2. _Tholospironium_, Haeckel. + +_Definition._--Spiral convolutions of the cortical shell double; both wings +of the sagittal girdle turning around the transverse axis. + + +4. _Tholospira hystrix_, n. sp. + +Cortical shell covered with numerous (sixty to eighty or more) simple +conical spines, about half as long as the shell. Perimeter of the lateral +plane hexagonal, one and a half times as long as broad. Four internal +kidney-shaped gates, as in _Tetrapyle_. Both wings of the sagittal girdle +turn round one another in two to two and a half double spiral turns. + +_Dimensions._--Length of the cortical shell 0.21, breadth 0.14; length of +the medullary shell 0.04, breadth 0.03. + +_Habitat._--North Atlantic, Station 354, surface. + + +5. _Tholospira cervicornis_, n. sp. (Pl. 49, fig. 5). + +Cortical shell covered with numerous (forty to fifty or more) branched +radial spines; each spine antler-shaped, about as long as the medullary +_Larnacilla_-shell, with eight to twelve dichotomous branches (similar to +_Cromyodrymus abietinus_, Pl. 30, fig. 6). Perimeter of the lateral plane +elliptical, one and a third times as long as broad. Four internal +kidney-shaped gates, as in _Tetrapyle_. Both wings of the sagittal girdle +turn round one another in one and a half to two double spiral turns. + +_Dimensions._--Length of the cortical shell 0.2, breadth 0.15; length of +the medullary shell 0.03, breadth 0.025. + +_Habitat._--Pacific, central area, Station 271, depth 2425 fathoms. + + + +{701}Genus 309. _Spironium_,[349] n. gen. + +_Definition._--#Lithelida# with double, trizonal or _Larnacilla_-shaped +medullary shell; cortical shell subspherical or lentelliptical, constructed +of two crossed spirals, which arise from both lateral wings of one girdle +(commonly the lateral girdle) and revolve in an opposite diagonal direction +around the principal axis. + +The genus _Spironium_ differs in a very remarkable manner from all +foregoing Lithelida, and is distinguished by a quite peculiar mode of +growth. It is most nearly allied to _Larcopyle_, and may, like this, be +derived from _Amphipyle_ (or rather from _Larnacilla_, beginning to +transform into _Amphipyle_). But whilst in _Larcopyle_ one of the two wings +of the lateral girdle overgrows the other in the direction of the +transverse axis (turning around the principal axis), here in _Spironium_ +both lateral wings begin at the same time to grow out from the lateral +sides of the _Larnacilla_-shaped medullary shell; the most remarkable thing +is, however, that the direction of growth in the wings is diverse from the +beginning: the left wing grows downwards and turns around the lower +(aboral) pole of the principal axis, the right wing grows upwards and turns +around the upper (oral) pole of the same axis. Thus both wings of the +lateral girdle are crossed in diagonal axes, and with increasing growth one +overgrows the other in the direction of these diagonals, so as to resemble +the figure 8 in shape. The open gates remaining between the turnings of the +girdle become afterwards closed on the surface by irregular lattice-work, +and so the whole cortical shell assumes finally a spherical, ellipsoidal, +or lentelliptical form. Its surface sometimes becomes covered with simple +or branched radial spines. In the interior the eight characteristic +egg-shaped gates of _Octopyle_ are commonly (or constantly?) visible, two +strong radial beams in the principal axis arising from the poles of the +lentelliptical medullary shell. + + + +Subgenus 1. _Spironetta_, Haeckel. + +_Definition._--Surface of the shell smooth or rough, but not with radial +spines. + + +1. _Spironium octonium_, n. sp. (Pl. 49, fig. 7). + +Cortical shell lentelliptical, its breadth (or transverse axis) surpassing +considerably the length (or the principal axis). Surface thorny and +somewhat hump-backed. The spiral wings of the transverse girdle have about +the same breadth as the eight internal gates between them and the axial +beams. + +_Dimensions._--Length of the cortical shell (or principal axis) 0.15, +breadth (or transverse axis) 0.2; length of the medullary shell 0.05, +breadth 0.04. + +_Habitat._--South Atlantic, west of Tristan da Cunha, Station 332, depth +2200 fathoms. + + +{702}2. _Spironium diagonale_, n. sp. + +Cortical shell nearly spherical, four times as great as the subspherical +medullary shell. Surface rough. The spiral wings of the transverse girdle +about half as broad as the eight internal gates between them and the axial +beams. + +_Dimensions._--Diameter of the cortical shell 0.16, of the medullary shell +0.04. + +_Habitat._--Indian Ocean, Zanzibar, Pullen, depth 2200 fathoms. + + + +Subgenus 2. _Spironilla_, Haeckel. + +_Definition._--Surface of the shell covered with simple or branched radial +spines. + + +3. _Spironium spinosum_, n. sp. + +Cortical shell subspherical, five times as great as the subspherical +medullary shell. Surface covered with numerous (sixty to eighty or more) +simple, bristle-like radial spines, longer than the shell. The spiral wings +of the transverse girdle of about the same breadth as the eight internal +gates between them and the axial beams. + +_Dimensions._--Diameter of the cortical shell 0.2, of the medullary shell +0.04. + +_Habitat._--Pacific, central area, Station 274, surface. + + +4. _Spironium arbustum_, n. sp. + +Cortical shell lentelliptical, its breadth surpassing its length +considerably. Surface covered with numerous (forty to sixty or more) thin +radial spines, about as long as the greatest diameter of the shell; each +spine with two to six lateral branches, which are either simple or again +branched (similar to _Cromyodrymus abietinus_, Pl. 30, fig. 6). The spiral +wings of the transverse girdle only half as broad as the eight internal +gates between them and the strong beams of the principal axis. + +_Dimensions._--Length of the cortical shell 0.12, breadth 0.15; length of +the hexagonal medullary shell 0.05, breadth 0.04. + +_Habitat._--Pacific, central area, Station 271, depth 2425 fathoms. + + + +Family XXX. #STREBLONIDA#, n. fam. (Pl. 49, figs. 8, 9). + +_Definition._--#Larcoidea# with asymmetrical, spiral, polythalamous shell, +composed of a variable number of roundish chambers, which form together an +ascending spiral; both halves of the shell unequal. Primordial chamber +either simple or _Larnacilla_-shaped. + +The family #Streblonida# comprises those #Larcoidea# in which a number of +chambers is arranged in an ascending spiral, round a simple or trizonal +primordial chamber, like winding stairs. They show the same spiral +structure as in the foregoing {703}family, but whilst in the Lithelida the +spiral line lies in one plane (as in _Nautilus_), in the Streblonida it +ascends like a screw (as in _Helix_). Therefore the former have the same +relation, regarding the spiral structure, to the nautiloid Polythalamia as +the latter to the turbinoid Foraminifera. Indeed the single forms of +Streblemida repeat in their special structure the characteristic genera of +Turbinoida, such as _Globigerina_, _Rosalina_, _Pulvinulina_, +_Hastigerina_, &c. As in these calcareous turbinoid Foraminifera, so also +in the analogous siliceous Streblonida the distinction of species is very +difficult and open to many objections. + +The number of species in this family is very small; all are rare and for +the most part very opaque and difficult to understand, so that the +following distinction of a dozen species can have only a provisional value. +To get a complete idea of their peculiar structure, the shell must be +turned and observed from different sides, and thus their full study +requires yet much time and work. There are to be found evident transitional +forms between them and the Lithelida on the one hand and the Soreumida on +the other. Besides this, most species of Streblonida seem to have more +inclination to individual varieties and abnormalities than the majority of +the other Radiolaria. + +The general form of the whole shell is in the Streblonida sometimes more +egg-shaped or even subspherical, at other times more top-like or conical, +sometimes nearly discoidal. The height of the shell (or the vertical axis +of the ascending spiral) is occasionally larger, at other times smaller +than the breadth (or the greatest horizontal diameter, perpendicular to the +height). Some very flat forms seem to approach the Lithelida. With regard +to the internal screw-formation, the shell of all Streblonida is +asymmetrical. + +The number of the aggregated incomplete chambers is commonly between ten +and twenty, but ascends sometimes to thirty, forty, or more. Sometimes the +size of all the chambers is nearly the same, sometimes they increase +gradually, occasionally also very rapidly. The primordial chamber (or the +first and oldest) seems to be commonly the smallest, and inversely, the +last and youngest chamber, the largest. But sometimes (in _Streblopyle_) +also the contrary may be the case. The form of the single chambers is very +variable, from the spherical or hemispherical through all transitions +leading to irregular roundish or longish forms. The network is commonly +irregular, with small roundish pores of different sizes, but sometimes also +regular, circular. The surface of the shell is commonly smooth or rough, +rarely covered with radial spines. In most species the reticulation and +particularly the separation of the chambers is more or less incomplete. + +As in the Lithelida, so also in the Streblonida we can distinguish two +subfamilies. In the Streblacanthida (_Streblonia_, _Streblacantha_) the +primordial chamber is a simple, spherical, subspherical, or lentelliptical +latticed shell. In the Streblopylida (_Streblopyle_) the primordial chamber +is trizonal or _Larnacilla_-shaped, as in the greater number of +#Larcoidea#, composed of three elliptical latticed girdles of unequal size, +perpendicular one to another, and surrounding a simple central chamber. As +in the Lithelida, so also {704}here we cannot certainly say whether the +former have originated from the latter by reduction of the +_Larnacilla_-shell, or whether both groups be of different origin. The +latter is perhaps more probable. This family as well as the foregoing +requires a much more careful study than I could give to it. + +_Synopsis of the Genera of Streblonida._ + + ------------------------------------------------------------------------- + I. Subfamily Streblacanthida. + Primordial chamber simple, spherical or lentelliptical. + ------------------------------------------------------------------------- + Shell without radial spines, 310. _Streblonia_. + + Shell with radial spines, 311. _Streblacantha_. + ------------------------------------------------------------------------- + II. Subfamily Streblopylida. + Primordial chamber trizonal or _Larnacilla_-shaped. + ------------------------------------------------------------------------- + Shell without radial spines, 312. _Streblopyle_. + + + +Genus 310. _Streblonia_,[350] n. gen. + +_Definition._--#Streblonida# with simple, spherical, subspherical, or +lentelliptical primordial chamber, beginning the screw-like series of +spirally ascending chambers. Surface smooth or thorny, without radial +spines. + +The genus _Streblonia_ contains those Streblonida in which a variable +number of roundish, subspherical, or longish chambers form a screw-like +aggregate, beginning with a quite simple primordial chamber. The special +order of the complex spiral offers interesting resemblances to different +genera of the calcareous Foraminifera, from which I have taken the +corresponding name of the species. The whole form of the shell is sometimes +more egg-shaped or subspherical, at other times more top-like or conical, +occasionally very flat. Its surface is smooth or rough, but not covered +with radial spines. + + +1. _Streblonia globigerina_, n. sp. + +Shell subspherical, thick walled, clustered, with eight to ten nearly +spherical chambers, of rapidly increasing size, the tenth chamber about +twelve times as broad as the first. Breadth of the shell nearly equal to +the height. Pores subregular, circular, hexagonally formed, of about the +same breadth as the bars; about sixteen on the breadth of the tenth +chamber. (Resembles very much the common _Globigerina_.) + +_Dimensions._--Breadth of the shell 0.18, height 0.16. + +_Habitat._--North Pacific, Station 253, depth 3125 fathoms. + + +2. _Streblonia uvigerina_, n. sp. + +Shell nearly egg-shaped, clustered, with eight to eleven subspherical +chambers of gradually increasing size, the tenth chamber about six times as +broad as the first. Breadth of the shell about {705}half its height. Pores +of the shell subregular, circular, about twice as broad as the bars; about +twenty on the breadth of the tenth chamber. (Resembles some species of +_Uvigerina_.) + +_Dimensions._--Breadth of the shell 0.11, height 0.23. + +_Habitat._--South Atlantic, Station 332, depth 2200 fathoms. + + +3. _Streblonia polymorphina_, n. sp. + +Shell egg-shaped, thin walled, with twelve to fourteen roundish chambers of +rapidly increasing size, the tenth chamber about seven times as broad as +the first. Breadth of the shell about two-thirds of the height. Pores +irregular roundish, twice as broad as the bars; about twenty on the tenth +chamber. (Resembles certain forms of _Polymorphina_.) + +_Dimensions._--Breadth of shell 0.22, height 0.14. + +_Habitat._--Pacific, central area, Station 266, depth 2750 fathoms. + + +4. _Streblonia bulimina_, n. sp. + +Shell nearly egg-shaped, thick walled, clustered, with fourteen to eighteen +egg-shaped chambers of rapidly increasing size, the tenth chamber about +eight times as broad as the first. Breadth of the shell about two-thirds of +the height. Pores irregular, roundish, half as broad as the bars; about +twelve on the breadth of the tenth chamber. (Resembles closely _Bulimina_.) + +_Dimensions._--Breadth of the shell 0.17, height 0.24. + +_Habitat._--Pacific, central area, Station 268, depth 2900 fathoms. + + +5. _Streblonia rosalina_, n. sp. + +Shell top-shaped or flatly conical, with twelve to sixteen chambers of +gradually increasing size, the tenth chamber about four times as broad as +the first. Breadth of the shell twice as large as the height. Pores +subregular, circular, very small, of the same breadth as the bars; about +twelve on the breadth of the tenth chamber. (Resembles some forms of +_Rosalina_.) + +_Dimensions._--Breadth of the shell 0.27, height 0.13. + +_Habitat._--Pacific, central area, Station 271, depth 2425 fathoms. + + +6. _Streblonia planorbulina_, n. sp. + +Shell very flatly conical, nearly lenticular or discoidal, with twenty to +twenty-five chambers of nearly equal size, the tenth chamber a little +broader than the first. Breadth of the shell exceeds five to six times the +height. Pores subregular, circular, very small, half as broad as the bars; +about eight on the breadth of the tenth chamber. (Resembles closely +_Planorbulina_.) + +_Dimensions._--Breadth of the shell 0.3 to 0.4, height 0.06 to 0.07. + +_Habitat._--Indian Ocean, Zanzibar, Pullen, depth 2200 fathoms. + + +{706}7. _Streblonia pulvinulina_, n. sp. + +Shell top-shaped or flatly conical, with thirty to forty chambers of slowly +increasing size, the tenth chamber about three times as broad as the first. +Breadth of the shell exceeds three times the height. Pores circular, +subregular, very small, about one-third as broad as the bars; about thirty +in the breadth of the tenth chamber. (Resembles closely _Pulvinulina_.) + +_Dimensions._--Breadth of the shell 0.25, height 0.08. + +_Habitat._--Pacific, central area, Station 263, depth 2650 fathoms. + + + +Genus 311. _Streblacantha_,[351] n. gen. + +_Definition._--#Streblonida# with simple, spherical, subspherical, or +lentelliptical primordial chamber, beginning the screw-like series of +spirally ascending chambers. Surface covered with radial spines. + +The genus _Streblacantha_ differs from the nearly allied _Streblonia_ only +in the covering of radial spines, and bears therefore the same relation to +it as _Hastigerina_ has to _Globigerina_ amongst the similar calcareous +Polythalamia. + + +1. _Streblacantha siderolina_, n. sp. (Pl. 49, figs. 8, 8_a_). + + _Streblonia siderolina_, Haeckel, 1883, MS. + +Shell flatly conical, with fourteen to sixteen nearly hemispherical +chambers of gradually increasing size, the tenth chamber about six times as +broad as the first. Breadth of the shell nearly equal to the height. Pores +subregular, circular, hexagonally framed, twice as broad as the bars; about +nine pores on the breadth of the tenth chamber. Surface covered with +numerous short conical radial spines, one-fourth to one-sixth as long as +the diameter of the shell. + +_Dimensions._--Breadth of the shell 0.15, height 0.17. + +_Habitat._--South Pacific, Station 298, depth 2225 fathoms. + + +2. _Streblacantha calcarina_, n. sp. + +Shell conical, with sixteen to eighteen roundish chambers of gradually +increasing size, the tenth chamber about three times as broad as the first. +Breadth of the shell about one and a half times the height. Pores +irregular, roundish. Surface covered with numerous strong conical radial +spines, about half as long as the diameter of the shell. + +_Dimensions._--Breadth of the shell 0.24, height 0.17. + +_Habitat._--South Pacific, Station 285, depth 2375 fathoms. + + +{707}3. _Streblacantha hastigerina_, n. sp. + +Shell nearly spherical, clustered, with nine to eleven nearly spherical +chambers of rapidly increasing size, the tenth chamber about six times as +broad as the first. Breadth of the shell nearly equal to the height. Pores +subregular, circular, of about the same breadth as the bars. Surface +bristly, covered with numerous very thin and long, needle-shaped radial +spines, longer than the diameter of the shell. (Resembles closely +_Hastigerina_.) + +_Dimensions._--Breadth of the shell 0.18, height 0.15. + +_Habitat._--Pacific, central area, Station 271, depth 2425 fathoms. + + + +Genus 312. _Streblopyle_,[352] n. gen. + +_Definition_.--#Streblonida# with trizonal lentelliptical medullary shell +(composed like _Larnacilla_ of three elliptical dimensive girdles +surrounding one simple central primordial chamber). From this begins a +screw-like series of spirally ascending chambers. Surface smooth or thorny, +without radial spines. + +The genus _Streblopyle_ presents externally the same appearance and contour +as _Streblonia_, and is composed like this of a variable number of +chambers, ascending screw-like around the axis of the spiral shell. The +first or primordial chamber, however, in which the growth begins, is in +_Streblonia_ a simple spherical shell, but in _Streblopyle_ a trizonal +shell or _Larnacilla_-shell (compare above, p. 600). The chambers are very +incompletely separated, and comparatively much larger, their number much +smaller than in _Streblonia_. The structure in the species of this genus is +difficult to understand. + + +1. _Streblopyle helicina_, n. sp. (Pl. 49, fig. 9). + +Shell helicoid, one and a third times as high as broad, with eight to +twelve incomplete semizonal chambers, ascending spirally from the lateral +half girdle of the lentelliptical medullary shell, octopyle-shaped, and +enveloping it in three to four spiral turnings. The height of the whole +cortical shell equals nearly five times the height of the trizonal +medullary shell. Pores irregular, roundish. Surface of the shell rough or +nearly smooth. (This species seems to be nearly allied to _Spironium +octonium_.) + +_Dimensions._--Breadth of the spiral cortical shell 0.18, height 0.24; +breadth of the medullary shell 0.04, height 0.05. + +_Habitat._--Pacific, central area, Station 266, depth 2750 fathoms. + + +2. _Streblopyle spirulina_, n. sp. + +Shell egg-shaped or nearly spherical, about as high as broad, with eight to +nine semizonal chambers, ascending spirally from the subspherical trizonal +medullary shell, and enveloping it in {708}four to five turnings. The sixth +chamber twice as broad as the trizonal medullary shell. Pores irregular, +roundish. Surface of the shell thorny. + +_Dimensions._--Breadth of the spiral cortical shell 0.27, height 0.25; +breadth of the medullary shell 0.05, height 0.06. + +_Habitat._--Pacific, central area, Station 265, depth 2900 fathoms. + + + +Family XXXI. #PHORTICIDA#, Haeckel (Pl. 49, figs. 10, 11). + +_Phorticida_, Haeckel, 1881, Prodromus, p. 464. + +_Definition._--#Larcoidea# with quite irregular monothalamous shell, +representing irregular modifications of an original lentelliptical latticed +shell; the irregular cortical shell encloses a regular or subregular, +lentelliptical or trizonal medullary shell. + +The family Phorticida comprises a small number of #Larcoidea# in which a +subregular, trizonal, lentelliptical medullary shell is enclosed by an +irregular simple or spongy cortical shell. The lattice-work of the latter +is sometimes simple and complete, at other times incomplete, with open +gates (as in the Pylonida), sometimes also spongy. Its form is always more +or less irregular, roundish, often dimply or tuberous; different from most +other #Larcoidea#. + +The medullary shell is constantly a regular or subregular +_Larnacilla_-shell, composed of three elliptical latticed girdles of +different sizes, perpendicular one to another. This leaves no doubt that +the Phorticida are true #Larcoidea#. The connection of it with the cortical +shell is rarely effected by radial beams, commonly by two opposite latticed +wings, which are identical with the lateral halves of the transverse girdle +in the Pylonida diplozonaria (_Amphipyle_, _Tetrapyle_). Often also between +this transverse and a second (lateral) girdle there remain large open +gates, so that the affinity between these Phorticida and the Pylonida +cannot be doubted. In other cases these gates become closed, so that they +more nearly approach the Larnacida. From both families they differ by the +irregularity of the papillate or tuberous cortical shell. The network is +more or less irregular, its surface often thorny, but never covered with +symmetrically disposed radial spines. + +The central capsule is lentelliptical, encloses the medullary shell, and is +enveloped by the cortical shell, as in the nearly allied Pylonida and +Larnacida, of which the Phorticida may be regarded as irregular aberrant +forms. + +_Synopsis of the Genera of Phorticida._ + + Cortical shell simply latticed, 313. _Phorticium_. + + Cortical shell spongy, 314. _Spongophortis_. + + + +{709}Genus 313. _Phorticium_,[353] Haeckel, 1881, Prodromus, p. 464. + +_Definition._--#Phorticida# with irregular cortical shell of simple +lattice-work, enclosing a lentelliptical _Larnacilla_-shaped medullary +shell. + +The genus _Phorticium_ comprises all Phorticida in which the irregular +cortical shell is formed by simple lattice-work, not by spongy framework. +We can divide this genus into two subgenera: in _Phortopyle_ (as in the +_Pylonida_) the lattice-work of the cortical shell exhibits large openings +or gates; in _Phortolarcus_ these gates are perfectly closed by network; +the former may be regarded as abnormal or irregular Pylonida, the latter as +modifications of Larnacida. + + + +Subgenus 1. _Phortopyle_, Haeckel. + +_Definition._--Lattice-work of the irregular cortical shell incomplete, +with large openings or gates. + + +1. _Phorticium pylonium_, n. sp. (Pl. 49, fig. 10). + +Cortical shell irregular, roundish, about three times as large as the +enclosed lentelliptical, regular, _Larnacilla_-shell, connected with it by +some radial beams and irregularly latticed girdles; between these remain +four to eight large open gates of irregular roundish form and size; and +these gates are the same as in _Tetrapyle_ and _Octopyle_. This very +variable species may be regarded as a monstrosity of those genera of +Pylonida; it is very common, but all individuals are more or less unequal; +some specimens approach to some common species of _Tetrapyle_. The surface +of the shell is more or less spiny. + +_Dimensions._--Diameter of the irregular cortical shell 0.12 to 0.18; +length of the lentelliptical medullary shell 0.05 to 0.06, breadth 0.035 to +0.045. + +_Habitat._--Cosmopolitan; Mediterranean, Atlantic, Pacific, &c., common, +surface and in various depths. + + +2. _Phorticium spironium_, n. sp. + +Cortical shell irregular, roundish, tuberous, about four times as large as +the enclosed subregular _Larnacilla_-shell, connected with it by some +irregular radial beams, and by opposite, spirally begining, irregularly +latticed girdles, comparable to those of _Spironium_; between them remain +six to twelve large open gates of irregular size and form. Surface rough. +The resemblance to some forms of _Spironium_ makes it probable that this +species is a deformity or monstrosity of that genus. + +_Dimensions._--Diameter of the irregular cortical shell 0.12 to 0.2, of the +lentelliptical medullary shell 0.03 to 0.06. + +_Habitat._--Pacific, central area, Stations 270 to 274, surface, and in +various depths. + + + +{710}Subgenus 2. _Phortolarcus_, Haeckel. + +_Definition._--Lattice-work of the irregular cortical shell complete, +without large openings or gates. + + +3. _Phorticium deforme_, n. sp. + +Cortical shell irregular, roundish or longish, three times as large as the +enclosed subregular, lentelliptical _Larnacilla_-shell, connected with it +by two opposite latticed wings (the halves of the transverse girdle of +_Tetrapyle_). Network of the cortical shell irregular, dense, perfectly +closed, without larger openings or gates. Surface thorny. (May be regarded +as a monstrous form of _Larnacalpis_.) + +_Dimensions._--Diameter of the irregular cortical shell 0.15 to 0.18, of +the medullary shell 0.04 to 0.06. + +_Habitat._--Pacific, central area, Station 272, depth 2600 fathoms. + + +4. _Phorticium abnorme_, n. sp. + +Cortical shell irregular, roundish, tuberous, with five to ten quite +irregular or nearly hemispherical protuberances, which resemble the cupolas +of Zonarida. The regular lentelliptical _Larnacilla_-shell is one-third to +one-fourth as large as the enclosing cortical shell, and is connected with +it by some irregular radial beams. Lattice-work completely closed, without +gates. Surface spiny. (May be regarded as an anomalous form of _Zonidium_; +as in the other species of this variable genus, the individuals are very +unequal.) + +_Dimensions._--Diameter of the irregular cortical shell 0.12 to 0.2, of the +medullary shell 0.03 to 0.05. + +_Habitat._--Atlantic and Pacific, tropical zone, surface, and at various +depths. + + + +Genus 314. _Spongophortis_,[354] Haeckel, 1881, Prodromus, p. 464. + +_Definition._--#Phorticida# with irregular cortical shell of spongy +framework, enclosing a lentelliptical _Larnacilla_-shaped medullary shell. + +The genus _Spongophortis_ differs from _Phorticium_ in the spongy framework +of the cortical shell. This encloses the inner _Larnacilla_-shaped +medullary shell either directly, or both shells are separated by a hollow +interval, and connected either by radial beams or by latticed lamellae. +Perhaps both these subgenera might be better separated as genera. + + + +{711}Subgenus 1. _Stypophorticium_, Haeckel. + +_Definition._--Spongy cortical shell immediately enclosing the +lentelliptical medullary shell, without hollow interval. + + +1. _Spongophortis spongiosa_, n. sp. + +Cortical shell irregular, roundish, rough or tuberous, composed of loose +spongy framework, which immediately envelops the lentelliptical central +_Larnacilla_-shell; the diameter of the former becomes about five to six +times as large as that of the latter. + +_Dimensions._--Diameter of the spongy cortical shell 0.15 to 0.25, of the +trizonal medullary shell 0.03 to 0.04. + +_Habitat._--Pacific, central area, Station 274, surface. + + + +Subgenus 2. _Spongophorticium_, Haeckel. + +_Definition._--Spongy cortical shell separated by a hollow interval from +the lentelliptical medullary shell. + + +2. _Spongophortis radiosa_, n. sp. + +Cortical shell irregular, roundish, four to five times as large as the +enclosed lentelliptical _Larnacilla_-shell, with which it is connected by +ten to twenty irregularly disposed radial beams. Spongy framework compact, +about as thick as the medullary shell. Surface covered with numerous short, +bristle-shaped, radial spines. + +_Dimensions._--Diameter of the spongy cortical shell 0.15 to 0.2, of the +trizonal medullary shell 0.035 to 0.045. + +_Habitat._--South Atlantic, Station 332, depth 2200 fathoms. + + +3. _Spongophortis larnacilla_, n. sp. (Pl. 49, figs. 11_a_-11_d_). + +Cortical shell irregular, roundish, tuberous, three to four times as large +as the enclosed lentelliptical _Larnacilla_-shell, connected with it by two +opposite latticed wings (the halves of the transverse girdle of +_Tetrapyle_). Spongy framework compact, about half as thick as the +medullary shell. Surface rough. (May be regarded as an abnormal _Tetrapyle_ +or _Larnacalpis_, with an irregular spongy cortical shell.) + +_Dimensions._--Diameter of the spongy cortical shell 0.16 to 0.2, of the +trizonal medullary shell 0.04 to 0.06. + +_Habitat._--Pacific, central area, Station 271, depth 2425 fathoms. + + + +{712}Family XXXII. #SOREUMIDA#, Haeckel (Pl. 49, figs. 12, 13). + +_Soreumida_, Haeckel, 1881, Prodromus, p. 464. + +_Definition._--#Larcoidea# with quite irregular polythalamous shell, +composed of a variable number of chambers, aggregated without any definite +order. Primordial chamber either simple or _Larnacilla_-shaped. + +The family #Soreumida# contains a small number of #Larcoidea#, different +from most other #Sphaerellaria# in the complete irregularity of the +polythalamous shell, which is composed of a variable number of roundish +chambers or subspherical latticed shells, aggregated in the form of an +irregular heap. We can distinguish in this family only two genera, with +very different structure of the central medullary shell or the first +chamber beginning the growth; and these correspond to the two subfamilies +of the nearly allied Streblonida (p. 704). In _Soreuma_ (as in +_Streblonia_) the first or primordial chamber, from which the growth +begins, is like the others, a simple spherical or irregular roundish +lattice-shell. In _Sorolarcus_, however (as in _Streblopyle_), the first or +primordial chamber is a trizonal or _Larnacilla_-shell. It is not +improbable that the former originated phylogenetically from _Streblonia_, +the latter from _Streblopyle_, by loss of the original spiral order of +growth. But it is also possible that these groups have no nearer relation. +Among the calcareous Foraminifera a very similar form is represented by +_Acervulina_ and its allies. + +The general form of the whole shell in the Soreumida is sometimes more +egg-shaped or lentelliptical, at other times even subspherical, +occasionally quite irregular, tuberous, or clustered. The number of the +aggregated chambers is very variable, in _Sorolarcus_ between ten and +thirty, in _Soreuma_ ascending to fifty to eighty, sometimes from one +hundred to one hundred and fifty and more. Their size is sometimes nearly +equal, at other times very different, their form commonly very irregular, +roundish, but sometimes also subspherical or egg-shaped. The network of the +shell is also commonly irregular, with roundish pores of different sizes. +The surface is usually smooth or rough, rarely covered with radial spines. + +The central capsule is not known, as I observed only a few skeletons of +this family. + +_Synopsis of the Genera of Soreumida._ + + Primordial chamber of the shell simple, subspherical + or roundish, 315. _Soreuma_. + + Primordial chamber of the shell trizonal or + _Larnacilla_-shaped, 316. _Sorolarcus_. + + + +Genus 315. _Soreuma_,[355] Haeckel, 1881, Prodromus, p. 464. + +_Definition._--#Soreumida# with numerous chambers, aggregated without any +regularity around one simple, spherical or subspherical, central chamber. + +{713}The genus _Soreuma_ contains those Soreumida in which no trace of any +regular structure is found, but all the chambers of the irregular shell are +without any order, aggregated around a simple spherical or subspherical +central chamber or medullary shell. _Soreuma_ may have originated either +from _Sorolarcus_ by loss of the central _Larnacilla_-shell or from +_Cenolarcus_ by irregular apposition of new chambers around the +lentelliptical central chamber or simple Larcoid-shell. Some species seem +to exhibit a transition to _Sorolarcus_. Owing to the absolute irregularity +of the polythalamous shell _Soreuma_ resembles _Acervulina_ among the +Foraminifera. + + + +Subgenus 1. _Soreumium_, Haeckel. + +_Definition._--Shell without radial spines. + + +1. _Soreuma irregulare_, n. sp. (Pl. 49, fig. 12). + +Shell irregular, clustered, or tuberous, composed of a large number (one +hundred and twenty to one hundred and fifty or more) of irregular, roundish +chambers of very different sizes, the largest four to five times as broad +as the smallest. Network very delicate, with very small roundish pores, to +five times as broad as the bars. Surface thorny. + +_Dimensions._--Diameter of the shell 0.3, of the single chambers 0.02 to +0.08. + +_Habitat._--North Pacific, Station 244, depth 2900 fathoms. + + +2. _Soreuma acinosum_, n. sp. + +Shell irregularly lentelliptical, with different growth in the three +dimensions, composed of a large number (forty to sixty or more) of +irregular, roundish chambers of very different sizes, the largest six to +eight times as broad as the smallest. Pores subregular, circular, twice as +broad as the bars. Surface smooth. + +_Dimensions._--Length of the shell 0.21, breadth 0.17, height 0.13; +diameter of the largest chambers 0.03, of the smallest 0.004. + +_Habitat._--Pacific, central area, Station 271, depth 2425 fathoms. + + +3. _Soreuma subglobosum_, n. sp. + +Shell nearly spherical, composed of a variable number (twelve to fifteen or +more) of irregularly aggregated subspherical chambers of nearly equal size. +Pores subregular, circular, twice as broad as the bars. Surface thorny. + +_Dimensions._--Diameter of the shell 0.25, of the largest chambers 0.04, of +the smallest 0.005. + +_Habitat._--Pacific, central area, Station 266, depth 2750 fathoms. + + +{714}4. _Soreuma acervulina_, n. sp. + +Shell quite irregular, cloddy, or tuberous, composed of twenty to thirty +(or more) roundish chambers of almost uniform size, the largest twice to +three times as broad as the smallest. Pores irregular, roundish. Surface +smooth. + +_Dimensions._--Diameter of the shell 0.18 to 0.24, of the largest chambers +0.06, of the smallest 0.02. + +_Habitat._--South Pacific, Station 295, depth 1500 fathoms. + + + +Subgenus 2. _Soreumidium_, Haeckel. + +_Definition._--Shell with radial spines. + + +5. _Soreuma spinosum_, n. sp. + +Shell quite irregular, cloddy, or tuberous, composed of thirty to forty +subspherical chambers of nearly the same size. Pores subregular, circular, +twice as broad as the bars; on the equator of each chamber six to eight +pores. Surface thorny, covered with irregularly scattered conical radial +spines, about as long as the diameter of the chambers. + +_Dimensions._--Diameter of the shell 0.17 to 0.25, of the chambers 0.04. + +_Habitat._--North Pacific, Station 241, depth 2300 fathoms. + + +6. _Soreuma setosum_, n. sp. + +Shell nearly spherical, composed of sixty to seventy (or more) irregular, +roundish chambers of very different sizes, the largest five to six times as +broad as the smallest. Pores irregular, roundish. Surface bristly, covered +with very numerous, long and thin, bristle-shaped radial spines, about as +long as the diameter of the shell. + +_Dimensions._--Diameter of the shell 0.28, of the chambers 0.005 to 0.03. + +_Habitat._--Pacific, central area, Station 271, depth 2425 fathoms. + + + +Genus 316. _Sorolarcus_,[356] n. gen. + +_Definition._--#Soreumida# with numerous chambers, aggregated irregularly +around a trizonal medullary shell or _Larnacilla_-shell. + +The genus _Sorolarcus_ comprises those Soreumida in which the heap of +irregularly aggregated chambers encloses a central trizonal medullary +shell, by which they demonstrate clearly their descent from Larnacida or +Pylonida. The lentelliptical medullary {715}shell exhibits quite the same +characteristic structure as that of _Larnacilla_, being composed of three +elliptical latticed girdles, perpendicular one to another. In some species +also the beginning of a second system of girdles is clearly indicated, so +that there can be no doubt as to their derivation from _Amphipyle_ or +_Tetrapyle_. + + + +Subgenus 1. _Sorolarcium_, Haeckel. + +_Definition._--Shell without radial spines. + + +1. _Sorolarcus larnacillifer_, n. sp. (Pl. 49, fig. 13). + +Shell irregular, clustered, or tuberous, composed of twenty to thirty +irregular, roundish chambers of very different size, the largest four to +eight times as broad as the smallest, aggregated without order around a +central, lentelliptical, _Larnacilla_-shaped medullary shell. Pores +irregular, roundish, twice to four times as broad as the bars. Surface +smooth or a little spiny. + +_Dimensions._--Diameter of the whole shell 0.18, of the central +_Larnacilla_-shell 0.05. + +_Habitat._--Pacific, central area, Station 266, depth 2750 fathoms. + + +2. _Sorolarcus tetrapylifer_, n. sp. + +Shell irregularly roundish, clustered, composed of ten to twelve irregular +rather long chambers of almost uniform size, the largest twice as broad as +the smallest, aggregated without order around a central shell of the +structure of _Tetrapyle_, which encloses an inner trizonal +_Larnacilla_-shell of half the size. Pores irregular, roundish, twice to +four times as broad as the bars. Surface spiny. + +_Dimensions._--Diameter of the whole shell 0.25, of the outer +(_Tetrapyle_-like) medullary shell 0.12, of the inner (_Larnacilla_-like) +shell 0.06. + +_Habitat._--Pacific, central area, Station 272, depth 2600 fathoms. + + + +Subgenus 2. _Sorolarcidium_, Haeckel. + +_Definition._--Shell with radial spines. + + +3. _Sorolarcus terminalis_, n. sp. + +Shell nearly spherical, composed of fifteen to eighteen irregularly +aggregated roundish chambers of nearly equal size; in the centre a +lentelliptical _Larnacilla_-shell. Surface covered with numerous thin, +bristle-like radial spines, somewhat longer than the shell. + +_Dimensions._--Diameter of the whole shell 0.21, of the central +_Larnacilla_-shell 0.05. + +_Habitat._--North Pacific, Station 244, depth 2900 fathoms. + + +{716}---- + + +LEGION II. #ACANTHARIA#, + +VEL ACTIPYLEA, VEL ACANTHOMETREA (PLS. 129-140). + + _Acantharia_, Haeckel, 1881. + _Actipylea_, Haeckel, 1882. + _Acanthometrea_, Hertwig, 1879. + _Panacantha_, Haeckel, 1878. + +_Definition._--Radiolaria with simple membrane bounding the central +capsule, which is everywhere perforated by innumerable fine pores (disposed +either equally or symmetrically). Extracapsulum without phaeodium. Skeleton +centrogenous (its growth proceeding from the centre), acanthinic (organic, +not siliceous). Fundamental form originally spherical. + +The legion ACANTHARIA vel ACTIPYLEA, to the extent here defined, was +constituted by me, 1878, in my Protistenreich (p. 102) under the name +"PANACANTHA." A more accurate definition of this group was given in 1879 by +Hertwig under the name ACANTHOMETREA. Both names were replaced by me, 1881, +in my Prodromus (pp. 421, 465) by the more convenient name ACANTHARIA. This +legion comprises all those Radiolaria which were first described by +Johannes Mueller, 1858, as _Acanthometrae_, and also an important part of +his _Haliomma_. In my Monograph (1862, pp. 371-424) I disposed them in +three families, Acanthometrida, Diploconida, and Dorataspida. + +Although the number of genera and species in this legion is much increased +by the rich collection of the Challenger, we can divide all ACANTHARIA into +two different orders: #Acanthometra# (without complete lattice-shell) and +#Acanthophracta# (provided with a complete lattice-shell). + +The ACANTHARIA agree with the SPUMELLARIA in the structure of the simple +capsule-membrane, which is perforated by numerous small pores (but +constantly devoid of the large main opening, which the NASSELLARIA and +PHAEODARIA possess, being hence united as "Merotrypasta"). We can therefore +unite both former legions as "Holotrypasta" (compare above, pp. 5, 6); but +in many ACANTHARIA (if not in all?) the numerous small pores of the +capsule-membrane exhibit a certain peculiar arrangement not observed in the +SPUMELLARIA; therefore the latter can be regarded as true "Peripylea" in +opposition to the former as "Actipylea." + +The peculiar main character of all ACTIPYLEA or ACANTHARIA is determined by +the chemical constitution of their skeleton, which is not silex, but a +peculiar organic substance, called by me in 1862 "acanthin" (Monogr. d. +Radiol., pp. 30, 32). In all other Radiolaria the skeleton is composed of +silex or of a silicate. But besides this {717}chemical difference, an +important morphological character of the skeleton also separates the +ACANTHARIA from all other Radiolaria: in the latter the skeleton is never +centrogenous or arising from the centre of the capsule; in strict +opposition to this general fact the skeleton of all ACANTHARIA is +centrogenous, composed of radial spines, which arise from the central point +of the capsule and pierce its membrane. These characteristic "radial spines +of acanthin," arising from the centre, are never hollow (as formerly was +supposed), but constantly solid. Their form is extremely variable, and most +important for the distinction of genera and species; but more interesting +from a general point of view is their peculiar arrangement or disposition. + +The regular disposition of twenty radial spines has general value almost +for all ACANTHARIA, with the exception only of the small group of +#Actinelida#. In this latter group the number of radial spines is either +more or less than twenty, and their disposition is either quite irregular +or follows a peculiar rule. The number of individuals of these +#Actinelida#, compared with that of the other ACANTHARIA, may be scarcely 1 +per cent., whilst the latter have more than 99 per cent.; the number of +observed species is in the former about 5 per cent., in the latter about 95 +per cent. Nevertheless the small group of #Actinelida# is very important, +being probably the ancestral group from which all other ACANTHARIA have +been phylogenetically derived. These other ACANTHARIA, with twenty +regularly disposed radial spines, represent the two large groups of +#Acanthonida# and #Acanthophracta#. For short and clear distinction of +these two groups of ACANTHARIA, we will call the #Actinelida# (with +irregular number and disposition of radial spines) Adelacantha, in +opposition to the Icosacantha (#Acanthonida# and #Acanthophracta#), which +all possess twenty regularly disposed radial spines. + +Johannes Mueller, the great zoologist, to whom we are indebted for the +first detection and accurate knowledge of the #Acanthometra#, already +recognised the regularity in the peculiar disposition of their twenty +radial spines (Abhandl. d. k. Akad. d. Wiss. Berlin, 1858, pp. 12, 37). In +honour of my great master I have called this regular disposition the +"Muellerian law of spine disposition," and have given a full explanation of +it in my Monograph (1862, pp. 40-45, 371, 372). With regard to its general +value for all Icosacantha (#Acanthonida# and #Acanthophracta#), we might +also call this promorphological Muellerian law "the Icosacanthan law." + +In 1862 I had already given the following precise definition of this +"Icosacanthan law" (_loc. cit._, p. 40):--"Between two poles of a spineless +axis are regularly disposed five parallel zones, each with four radial +spines; the four spines of each zone are equidistant one from another, and +also equidistant from each pole; and the four spines of each zone are so +alternating with those of each neighbouring zone, that all twenty spines +together lie in four meridian planes, which intersect one another at an +angle of 45d." For the clear conception of this remarkable Muellerian law, +and for the complete understanding of its high value for the complicated +{718}morphology of all Icosacantha, it is the most profitable way to retain +constantly in mind for comparison the figure of a terrestrial globe with +its axis and zones. The axis of the globe is the spineless axis of all +Icosacantha, around which all twenty spines are symmetrically disposed; it +is perpendicular to the bisecting equatorial plane, in which lies the +middle of the five parallel zones; therefore the four spines, crossed +perpendicularly in this equatorial plane, are called the equatorial spines +(_c_1 to _c_4 in the figures of Pls. 131-140); often, and mainly in the +family Quadrilonchida (Pl. 131), these four equatorial spines are much +larger or of a peculiar form, different from that of the sixteen other +spines. Each pair of the four equatorial spines lies in one equatorial +axis, and this latter is perpendicular to the crossing axis, in which lies +the other pair of opposite spines. We may regard these two equatorial +diameters, perpendicular one to another and to the spineless axis, as the +two perradial axes or primary axes. Correspondingly the two meridian +planes, which are determined by one perradial axis and the spineless axis, +may be called the two primary or perradial meridian planes. + +The globe is divided by the equatorial plane into two equal halves, the +northern and the southern hemisphere. In each hemisphere there are disposed +quite symmetrically eight radial spines, the distal ends of which fall in +two parallel circles, a larger tropical circle (nearer to the equator) and +a smaller polar circle (nearer to the pole of the spineless axis). +Therefore we call the four spines of the former the "tropical spines" and +the four spines of the latter the "polar spines." The angle between the +former and the equatorial plane is about 30d, the angle between the latter +and that plane about 60d. + +The eight polar spines (four northern and four southern) lie in the same +two meridian planes as the four equatorial spines. Therefore in each of +these two perradial planes lie six radial spines, opposite in pairs; two +equatorial and four polar spines. Commonly all eight polar spines are of +the same size and form; and often they are also equal to the eight tropical +spines; but in some cases (e.g., in some species of Quadrilonchida) they +are much smaller than the twelve other spines, and sometimes even +rudimentary. In all figures of the Pls. 131-140 (and also in my Monograph, +1862, Taf. xv.-xxii.) the polar spines of the northern circle are marked by +the characters _a_1 to _a_4, the polar spines of the southern circle by the +characters _e_1 to _e_4. In the first perradial meridian plane lie _a_1 and +_a_3, _e_1 and _e_3, in the second _a_2 and _a_4, _e_2 and _e_4. + +The eight tropical spines lie between the eight polar and the four +equatorial spines, four in each hemisphere; their distal points fall in two +parallel circles, which correspond exactly to the two tropics of the globe. +Therefore the four northern tropical spines may be called "canceral spines" +(as their ends fall in the Tropic of Cancer) and the four southern +correspondingly "capricornal spines" (as their points lie {719}in the +Tropic of the Capricorn). In the figures of the Pls. 131-140 (as well as in +my Monograph, 1862, Taf. xv.-xxii.) the four northern or canceral spines +are marked by the characters _b_1 to _b_4, and the four southern or +capricornal spines by the characters _d_1 to _d_4. Also the eight tropical +spines lie (crossed in pairs) in two meridian planes; they do not lie, +however, in those perradial planes, in which are placed the twelve other +spines; but in two different meridian planes, crossing the former at angles +of 45d; we call these the "secondary" or "interradial" meridian planes. +Each of these planes is determined by the spineless axis and by two crossed +interradial or secondary axes; in each of the latter lie two opposite +tropical spines. In the first interradial meridian plane lie _b_1 and _b_3, +_d_1 and _d_3, in the second _b_2 and _b_4, _d_2 and _d_4. + +It is a most interesting and important fact, that in all Icosacantha +(#Acanthonida# and #Acanthophracta#) this regular disposition of the twenty +spines (in five parallel zones and four meridian planes) becomes constantly +preserved by heredity, whilst the form and size of the different spines are +extremely varied by adaptation. + +Only in a minority of the Icosacantha are all twenty spines perfectly +equal or nearly equal in size and form; and then it is often very difficult +to distinguish the different zones in their disposition. But in far the +greater part the size or the form of the twenty spines becomes different in +different zones; and then we can commonly distinguish easily the five +different zones. Firstly, in all Quadrilonchida and Dorataspida, the four +equatorial are distinguished from the sixteen other spines either by form +or by size, and often in a very remarkable degree. As soon as these four +principal spines are recognised, it is easy to determine also the sixteen +others; for the eight polar spines lie in the same two (perradial) meridian +planes as the former, whilst the eight tropical spines lie in two different +(interradial) meridian planes, intersecting the two former at angles of +45d. Commonly, therefore, this distinction is rather easy. + +In the majority of the Icosacantha all four equatorial spines are exactly +of the same form and size. But in four families the two opposite spines of +one equatorial axis are much larger, or of another form, than those of the +crossing axis. This is the case in the Amphilonchida, Belonaspida, +Hexalaspida, and Diploconida. Therefore we here call the major equatorial +axis (with larger spines) the "hydrotomical axis," and the minor axis (with +smaller spines) the "geotomical axis." Correspondingly, the meridian plane, + in which the two larger equatorial spines are placed (_c_1, _c_3) and the +appertaining four polar spines (_a_1, _a_3, _e_1, _e_3) may be called the +"hydrotomical plane"; in the remarkable family of Hexalaspida (Pl. 139) all +six spines of this hydrotomical plane are much larger than the other +fourteen. Perpendicular to this plane is the second perradial meridian +plane, which we call the "geotomical plane"; in it lie the two smaller +equatorial spines (c2, c4) and the corresponding four polar spines (_a_2, +_a_4, _e_2, _e_4). In some Hexalaspida (_Hexonaspis_ and _Hexacolpus_) the +six spines of the hydrotomical plane become so preponderant that {720}the +other fourteen spines appear rudimentary; and in some of them the two +equatorial spines of the hydrotomical plane are much larger than the four +polar spines of the same plane. This curious relation reaches its maximum +in the Diploconida (Pl. 140). + +The different development of the two equatorial axes (of the larger +hydrotomical and the smaller geotomical axis) is the first and most +important cause of the peculiar forms, which are produced in the four cited +families. We derive these terms also from the metaphor of the terrestrial +globe. The hydrotomical plane is that meridian plane of the globe which +intersects almost only the water-hemisphere (the island of Ferro in the +Atlantic, the island of Pandora in the Pacific). Perpendicular to this is +the geotomical plane, the meridian of which intersects great land-masses in +both hemispheres (Bombay in India, Athabasca in Canada). Both poles of the +smaller geotomical axis are everywhere equal (the East Indian and the +Western American). However, both poles of the larger hydrotomical axis (the +eastern Atlantic and the western Pacific) are in some genera very +different, _e.g._, in _Amphibelone_ among the Amphilonchida, and in +_Zygostaurus_ among the Quadrilonchida. In this case we call the anterior +(commonly more developed) pole of the hydrotomical axis the frontal pole, +the opposite posterior (commonly smaller) the caudal pole (Pl. 131, figs. +7, 8; Pl. 132, figs. 9, 10). On both sides of these (right and left) lie +symmetrically the two equal poles of the geotomical lateral axis. + +The promorphology of the ACANTHARIA demonstrates that the geometrical +fundamental form in those groups is different. In the majority of the +ACANTHARIA, where the two equatorial axes are equal, that form is a double +square-pyramid or a "quadrate octahedron"; the four equal equatorial spines +indicate the two diagonals of the square, which is the common base of the +united regular four-sided pyramids; their common axis is the spineless axis +of the body; the ends of the polar spines fall on the edges of the +pyramids, while the ends of the tropical spines fall on the halving lines +of their faces. However, in those ACANTHARIA in which the two equatorial +axes become different, the square double pyramid becomes changed into a +rhombic double pyramid; the common base of the united pyramids is thus a +rhombus; the hydrotomical axis is the larger, the geotomical axis the +smaller diagonal of the rhombus. + +Opposed to the Icosacantha, under the name "Adelacantha," is the small +group of Actinelida, in which the number and disposition of the radial +spines is variable, not determined by the Muellerian law. Probably this +group is the common ancestral stock, from which the Icosacantha have been +derived by gradual development of their peculiar disposition. Probably the +oldest and most primitive form of all ACANTHARIA is _Actinelius_, in which +a variable and undetermined (often very large) number of radial spines is +united in one common central point, and therefore forms a needle-sphere. +Whilst here all spines (often more than a hundred) are of equal size and +form, in the nearly allied _Astrolophus_ large and small spines are +intermingled. Both genera together form the small ancestral family of +Astrolophida. In the strange family of Litholophida the radial spines do +not {721}radiate within a spherical space (equally disposed in all +directions), but within a quadrant or even an octant, forming a conical +brush or pencil. + +One very remarkable form of #Actinelida# is _Actinastrum_, forming the +transition from these Adelacantha to the common regular Icosacantha. In the +two observed species of _Actinastrum_ we find thirty-two radial spines, +twenty of which are disposed after the Muellerian law, as in the +Icosacantha. The other twelve are four interradial equatorial spines (lying +in the two secondary meridian planes) and eight perradial tropical spines +(lying in the two primary meridian planes). Therefore here in each primary +meridian plane are placed ten spines (two equatorial, four tropical, and +four polar spines), whereas in each secondary meridian plane are placed six +spines (two equatorial and four tropical). But here also all thirty-two +spines are so regularly placed that their free distal ends fall into five +parallel zones, four in each polar zone, eight in each tropical zone, and +eight in the equatorial zone. + +_The Central Junction_ of the radial spines in the ACANTHARIA becomes +effected in four different ways:--(1) by simple apposition of the pyramidal +central ends or bases; (2) by a basal leaf-cross, or by broad wings, four +on each spine, supported one upon the other; (3) by a central concrescence +of the meeting bases of all the twenty spines, growing perfectly together; +and (4) by a concrescence in pairs of every two opposite spines. The most +common and probably the original mode of junction is the first--by +pyramidal apposition; the spines at the central base are pointed in the +form of a pyramid, and the triangular faces of the neighbouring pyramids +are simply placed upon one another. Often the small basal pyramids are +imperfectly separated from the spines by an annular constriction. Commonly +the basal pyramids of the four equatorial spines are six-sided, those of +the sixteen other spines five-sided. + +The second mode of junction, by a basal leaf-cross, is developed from the +first and appears as a strengthening or a mechanical elaboration of it. +Immediately above the basal pyramid arise from its radial edges four thin +and broad triangular leaves or wings, and the meeting edges of the +neighbouring wings are in apposition one with the other, so that between +the bases of every three or four neighbouring spines a hollow pyramidal +space remains open. The apex of such a pyramidal space is directed towards +the centre of the body, but separated from it by the small basal pyramid; +its open base is directed outwards. The twenty-two hollow pyramidal spaces +are disposed regularly in four different groups:--(A) Four equatorial +spaces, four-sided, each limited by two equatorial and two tropical spines +(one canceral and one capricornal); (B) eight perizonal spaces (four +northern and four southern), four-sided, each limited by one equatorial, +two tropical, and one polar spine; (C) eight peripolar spaces (four +northern and four southern), three-sided, each limited by one tropical and +two polar spines; (D) two polar spaces (one northern and one southern), +four-sided, each limited by four neighbouring polar spines. + +{722}The third mode of junction, by central concrescence of all twenty +spines, was formerly regarded by me as an important peculiarity, sufficient +for the separation of subfamilies and genera (Monogr. d. Radiol., 1862, pp. +399, 401; Prodromus, 1881, p. 466). But I found afterwards that in many +species where the twenty spines commonly remain separated, accidentally +they grow perfectly together and form one single piece of acanthin--a +starrulet with twenty rays. Therefore I now think it is more natural to +divide those species only into different subgenera. + +A fourth and a very different mode of junction, quite sufficient for the +distinction of different families, is the concrescence in pairs of every +two opposite spines, lying in one diameter (in _Acanthochiasma_ and +_Chiastolus_). Here we obtain a number of "diametral spines" (each composed +of two originally opposed radial spines) and all these diametral spines are +crossed loosely near the central point of the body without any solid and +permanent apposition (Chiastolida). However, in some species of this +peculiar family the central part of the diametral spines is twisted like a +screw or spirally convoluted (Pl. 129, figs. 2, 3). + +_The Form of the Radial Spines_ in the ACANTHARIA is extremely varied, and +constitutes the main characters for the distinction of nearly four hundred +species. But all these different forms may be reduced phylogenetically to +three different fundamental forms:--(_a_) the cylindrical (with circular +transverse section), (_b_) the two-edged (with elliptical or lanceolate +transverse section), and (_c_) the four-edged (with square transverse +section). No doubt the first (_a_) is the original primitive form, from +which the two others are secondarily derived. Triangular spines never occur +in the ACANTHARIA, whilst, however, they are common in the #Sphaerellaria#. +The first and original form, the cylindrical spine, is either a true +cylinder of equal thickness in its whole length, or it is more or less +conical. Rarely the spine is in the distal half spindle-shaped, and thicker +than in the basal half. The second form, the two-edged spine, is more or +less compressed from two opposite sides; its two edges are either more +blunt, rounded, or more acute, sharp; its transverse section in the former +case is elliptical, in the latter case lanceolate or rhomboidal. Sometimes +the two edges are broader and in the form of two thin opposite wings. The +two-edged spines may be occasionally shorter, triangular or lanceolate, at +other times longer sword-shaped or linear. The third form, the four-edged +spine, has constantly a square transverse section; the sides of this square +are either even or concave; in the latter case the four edges are broadened +and wing-like, but in the former case not. The quadrangular spines are +either prismatic (of equal breadth throughout their whole length) or +pyramidal (becoming gradually thinner towards the distal apex). + +_The Apex of the Radial Spines_, or their free distal end, is in the +majority of ACANTHARIA simple, conical. In the minority it is either +truncated or bifid, or four-sided pyramidal, often with two, rarely with +four prominent parallel teeth. In some forms {723}the bifid spines are so +deeply cleft that they become forked. Much more interesting and more varied +than these different forms of the distal end are those of the apophyses of +the radial spines. + +_The Apophyses of the Radial Spines_, or their "lateral transverse +processes," are of the greatest importance for the morphological +development of the whole subclass. Only in sixteen among the sixty-five +genera of ACANTHARIA are the apophyses perfectly wanting; in the other +genera they determine in the first place their general character. In the +#Acanthometra# the apophyses remain perfectly free, whilst in the +#Acanthophracta# their meeting ends or branches compose the latticed shell. +All differences in form and shape of the apophyses can be reduced to only +two primary modes; either the spine bears two opposite or four crossed +apophyses; correspondingly all Acantharia apophysaria may be divided into +two different main groups, the Zygapophysica (with two opposite lateral +processes) and the Staurapophysica (with four crossed lateral processes +opposite in pairs). Both groups have probably no direct phylogenetic +connection, but seem to be derived independently from different stocks, and +produce different families. The Zygapophysica are probably derived from +Astrolonchida with two-edged spines (_Zygacantha_), and from this group +arise the Diporaspida, the ancestral group of the majority of +#Acanthophracta#. On the other hand the Staurapophysica are probably +derived from Astrolonchida with four-edged spines (_Acanthonia_), and from +this group arise the Tessaraspida. The apophyses of the #Acanthonida# are +partly simple, partly branched or even latticed; the apophyses of the +#Acanthophracta# are never simple, constantly branched and commonly +latticed. + +_The Malacoma_ (or the whole soft body of the ACANTHARIA as opposed to the +skeleton) exhibits some peculiarities which distinguish them from the other +Radiolaria, as well in the structure of the central capsule and its nucleus +as in that of the enveloping extracapsular body and the pseudopodia. + +The _Central Capsule_ is constantly spherical in the far greater number of +the ACANTHARIA, viz., in the following six families:--Astrolophida, +Chiastolida, Astrolonchida, Dorataspida, Sphaerocapsida, and +Phractopeltida. Among these six families the Astrolonchida and Dorataspida +are far greater and far richer in different forms than all the other +families. The central capsule becomes ellipsoidal or cylindrical, prolonged +in one axis, in the three families, Amphilonchida, Belonapsida, and +Diploconida; it becomes discoidal or lenticular, by the shortening of one +axis, in two families, viz., in the Quadrilonchida and Hexalaspida. +Finally, the peculiar family Litholophida is distinguished by the conical +form of its central capsule. + +_The Membrane_ of the central capsule in all ACANTHARIA is simple, commonly +thin, sometimes very delicate; in some species it seems to be developed +late, just immediately before the formation of the spores; but in no +species is it completely missing. The membrane is constantly pierced by +innumerable fine pores, for the emission of the {724}pseudopodia; but in +many species (and probably more or less in all ACANTHARIA) there is +recognisable a certain regularity in the disposition of the numerous +pseudopodia and of the pores by which they radiate from the capsule. +Sometimes these pores are disposed in a regular network of ramified lines, +whilst the meshes of this network are devoid of pores; in other cases they +form regular tufts or bushes between the radial spines. Probably in no +ACANTHARIA are the pores of the capsule membrane so numerous and so equally +distributed throughout as in the SPUMELLARIA; we may therefore call the +former ACTIPYLEA (in opposition to the latter, as PERIPYLEA). + +_The Nucleus_ of the ACANTHARIA is constantly excentric, whilst it is +originally constantly central in the SPUMELLARIA. This excentric position +is a necessary consequence of the centrogenous development of the radial +spines. Probably connected with this peculiarity is the other, that the +nucleus assumes a peculiar, complicated structure, and that in the greater +number of ACANTHARIA it becomes cleft very early, and that this cleavage is +effected by a peculiar kind of gemmation, first detected and very +accurately described by R. Hertwig (compare his Organismus d. Radiol., +1879, pp. 10-24). However, in the young ACANTHARIA the nucleus is +constantly simple, and in a certain number of species its cleavage takes +place late (as in the greater number of SPUMELLARIA). + +_The Endoplasm_, or the intracapsular sarcode, exhibits in the greater +number of ACANTHARIA a more or less distinct radial arrangement; but this +is often concealed by the different enclosed products of the +endoplasm--oil-globules, vacuoles, red or different coloured +pigment-granules, crystals, &c. Often it encloses a variable number of +"yellow cells" (becoming green by mineral acids) to be considered as +symbiotic xanthellae. + +_The Calymma_ or the jelly-veil, including the central capsule, in the +ACANTHARIA is more or less voluminous, and commonly envelops the skeleton +perfectly. In its surface is sometimes developed a peculiar network of +"supporting fibres." A very peculiar product are the remarkable +"Myophrisca" of the #Acanthometra#, which are wanting in the +#Acanthophracta#; they were first detected by Johannes Mueller, and figured +as "Cilien-Kraenze," afterwards explained by Hertwig as "contractile +Faeden," similar to muscular fibrillae (compare below). + +_The Matrix_, placed between the calymma and central capsule, in the +majority of the ACANTHARIA is a rather thin layer of granular exoplasm. + +_The Pseudopodia_ arising from it are not so numerous as in the +SPUMELLARIA, and not so equally disposed over the whole surface. Also their +tendency to ramify, anastomose, and form networks seems to be much less +developed. Commonly they are simple or little ramified. In many cases (and +perhaps everywhere) there may be distinguished two different kinds of +pseudopodia:--(1) Axopodia, or permanent pseudopodia (with axial +filaments?), piercing the wall of the central capsule, and arising from the +central mass of endoplasm; and (2) Collopodia, or variable pseudopodia +(without axial filaments), arising outside the capsule from the matrix of +extracapsular sarcode or from the {725}exoplasm on the surface of the +calymma. These and other differentiations seem to indicate that the +pseudopodia in the ACANTHARIA are more highly developed than in the +SPUMELLARIA, and justify the denomination of the former as "Actipylea." + +_Synopsis of the Orders and Suborders of_ ACANTHARIA. + + ------------------------------------------------------------------------- + I. ACANTHOMETRA. + Skeleton composed only of acanthinic radial spines not forming a + complete lattice-shell. + ------------------------------------------------------------------------- + Radial spines in variable and indefinite number, + disposed irregularly, 1. #Actinelida#. + + Radial spines constantly twenty, disposed regularly + after the Muellerian law of Icosacantha, 2. #Acanthonida#. + ------------------------------------------------------------------------- + II. ACANTHOPHRACTA. + Skeleton composed of twenty acanthinic radial spines (disposed after + the Muellerian law) and of a spherical or variously shaped complete + lattice-shell. + ------------------------------------------------------------------------- + Radial spines all twenty of equal size; shell and + central capsule spherical, 3. #Sphaerophracta#. + + Radial spines of different sizes; shell and central + capsule ellipsoidal, discoidal, or heteromorphous, 4. #Prunophracta#. + + +---- + + +Order III. ACANTHOMETRA, Johannes Mueller, 1855. + + _Acanthometra_, J. Mueller, 1855, Monatsber. d. k. preuss. Akad. d. Wiss. + Berlin. + _Acanthometrida_, Haeckel, 1862, Monogr. d. Radiol., p. 371. + _Acanthometrea_, R. Hertwig, 1879, Organismus d. Radiol., p. 133. + _Acanthonida et Litholophida_, Haeckel, 1881, Prodromus, pp. 465, 469. + +_Definition._--ACANTHARIA without complete latticed shell. + +The order #Acanthometra#, the third order of Radiolaria, comprises all +those ACANTHARIA in which the acanthinic skeleton is only composed of +radial spines arising from one common central point, but never forms a +complete latticed shell. By the absence of such a latticed or fenestrated +shell the #Acanthometra# differ principally from the nearly allied +#Acanthophracta#, the second order of ACANTHARIA, which constantly possess +such a complete shell. + +Johannes Mueller, who first detected and described the #Acanthometra# (in +1855, _loc. cit._), defined them as follows:--"Radiolaria without shell, +with siliceous radial spines" (1858, Abhandl. d. k. Akad. d. Wiss. Berlin, +p. 46). He described and figured eighteen species of them, disposed in four +genera (_Acanthometra_ with fifteen species, and _Zygacantha_, +_Lithophyllium_, _Lithoptera_, each with a single species). Among those +eighteen species, however, were two "Acanthometrae cataphractae," +appertaining to the following order, the #Acanthophracta#. + +In my Monograph (1862, p. 371) all true #Acanthometra# were united into a +single family, Acanthometrida, with the following definition:--"Skeleton +composed of a number of radial spines, piercing the central capsule and +united in its centre, without {726}latticed shell." In the majority of them +I observed that the skeleton did not consist of silex, but of a very +peculiar organic substance, which I called "acanthin." At that time I +divided the family Acanthometrida into four subfamilies:--(1) +Acanthostaurida, (2) Astrolithida, (3) Litholophida, (4) Acanthochiasmida. +The two former now represent the suborder #Acanthonida#, the two latter the +suborder #Actinelida#. The number of genera which I distinguished in my +Monograph amounted to nine, the number of species to fifty. By the rich +collections of the Challenger this number is so much increased that we can +here describe twenty-seven genera and one hundred and sixty species. + +Richard Hertwig in his work on the Organismus der Radiolarien (1879, pp. +6-25) adopted my family Acanthometrida, and gave a very accurate +description of its anatomical structure. He confirmed my observations that +the radial spines of this family are never hollow, but solid, and that +their chemical substance is not silex, but the organic matter "acanthin." +He found that the simple nucleus of the Acanthometrida is commonly very +early cleft, and that the peculiar brushes of filaments on the calymma, +described by Johannes Mueller and by me as "Gallert-cilien," are peculiar +"contractile filaments," comparable to the "muscle-fibrillae" of some +Infusoria, or the "Myophan-filaments" (Myophrisca). + +The order #Acanthometra# is here divided into two different suborders of +very unequal extent and value, the #Actinelida# and #Acanthonida#. The +first may be regarded as the common ancestral stock, not only of the +second, but of all ACANTHARIA. In the small group of #Actinelida# the +number of radial spines is variable and commonly indefinite, often very +large (more than a hundred); they are therefore Adelacantha. The second +suborder, the #Acanthonida#, comprise by far the greatest part of the +order, and possess constantly twenty radial spines, regularly disposed +after the Muellerian law; they are therefore (like all #Acanthophracta#) +Icosacantha (compare above, p. 717). + +The #Actinelida# possess constantly simple radial spines, without any +apophyses; their form is commonly very simple and primitive. This suborder +comprises three small but very different families, the Astrolophida, +Litholophida, and Chiastolida. The first family, the Astrolophida, is the +original ancestral group. A large and variable, commonly indefinite number +of radial spines is here united in the centre of the spherical central +capsule and radiating within a spherical space. In the second family, the +Litholophida, a small and variable number of radial spines (between ten and +twenty) is united in the apex of a conical central capsule and radiating +within the quadrant or octant of a spherical space. In the third family, +the Chiastolida, a variable number of radial spines is grown together by +pairs, in such a manner that every two opposite spines (placed originally +in one axis of the spherical central capsule) forms a single "diametral +spine"; all these diametral spines are not united in the centre of the +central capsule but only crossed loosely near the centre. + +{727}The #Acanthonida#, the second suborder of #Acanthometra#, embraces by +far the greatest number in this order, viz., all those forms in which +twenty radial spines are regularly disposed after the Muellerian +law--Icosacantha (compare above, p. 717). The radial spines of this +suborder are either simple or provided with transverse processes (either +two opposite or four crossed apophyses). They are commonly united in the +middle of the central capsule by their opposed basal ends, forming small +pyramids; the meeting triangular faces of the neighbouring pyramids being +propped one upon another. Above these small basal pyramids often arises a +basal leaf-cross formed by four broad triangular leaves or wings with +straight edges; the meeting thin edges of the neighbouring spines serve for +strengthening the basal junction and form hollow pyramidal spaces or +compartments, filled with the contents of the central capsule (compare p. +721). The suborder #Acanthonida# comprises three different families, the +Astrolonchida, Quadrilonchida, and Amphilonchida. The first family, the +Astrolonchida, comprises by far the greater number of the #Acanthonida#; +those genera in which all twenty spines are perfectly equal or nearly equal +in size and form. In the second family, the Quadrilonchida, the four +equatorial spines are much larger (and often also of another form) than the +sixteen other spines (often also the eight tropical larger than the eight +polar spines). The third family, the Amphilonchida, is distinguished by the +preponderating development of only two opposite equatorial spines, which +are much larger (and often also of another form) than the eighteen other +spines. + +_Synopsis of the Suborders and Families of_ #Acanthometra#. + + ------------------------------------------------------------------------- + Suborder I. ACTINELIDA. + Number of the radial spines variable, either more or less than twenty, + commonly disposed irregularly and not according to the Muellerian law. + ------------------------------------------------------------------------- + Radial spines very numerous (thirty to a hundred + or more), radiating from a common centre + within a spherical space, 1. ASTROLOPHIDA. + + Radial spines between ten and twenty, radiating + from one common point within a sphere-quadrant, 2. LITHOLOPHIDA. + + Radial spines of variable number; every two + opposite spines grown together in the centre; + therefore numerous diametral spines are + crossed freely in the centre, 3. CHIASTOLIDA. + ------------------------------------------------------------------------- + Suborder II. ACANTHONIDA. + Number of the radial spines constantly twenty, disposed regularly + according to the Muellerian law. + ------------------------------------------------------------------------- + All twenty radial spines nearly equal, and of + the same size and form, 4. ASTROLONCHIDA. + + Four equatorial spines much larger than (and + often also of different form from) the sixteen + other spines, 5. QUADRILONCHIDA. + + Two opposite equatorial spines (or principal + spines) much larger than (and often also of + different form from) the eighteen other + spines, 6. AMPHILONCHIDA. + + +{728}---- + + +Suborder I. ACTINELIDA, Haeckel, 1882. + +_Definition._--#Acanthometra# with a variable number of radial spines, +which are commonly irregularly disposed, not according to the Icosacantha. + + + +Family XXXIII. #ASTROLOPHIDA#, Haeckel. + +_Astrolophida_, Haeckel, 1881, Prodromus, p. 469. + +_Definition._--#Acantharia# with a variable number of simple radial spines, +radiating within a spherical space from one common central point which is +the centre of the spherical central capsule. No lattice shell. + +The family #Astrolophida# comprises the simplest and the most primitive +forms among all ACANTHARIA, and may therefore be regarded as the common +ancestral stock of this whole legion or subclass of Radiolaria. The +acanthinic skeleton is composed of a variable number of quite simple radial +spines, which are united in the centre of the spherical central capsule and +radiate, piercing its walls and the surrounding jelly-veil, within a +spherical space. + +The first observed form of this family is the ancestral genus _Actinelius_, +two different species of which I detected in 1864 in the northern +Mediterranean, at Villafranca, near Nice (compare Zeitschr. f. wiss. Zool., +1865, Bd. xv. p. 364, Taf. xxvi. fig. 4). Three other species of the same +genus were afterwards found by me in the Challenger collections. Whilst in +this _Actinelius_ all radial spines are of the same size, a new nearly +allied genus, _Astrolophus_ (with two species), differs from it by the +different size of the radial spines, a small number of very large spines +being intermingled with a very large number of small spines. In these two +genera, _Actinelius_ and _Astrolophus_ (the true "Astrolophida" _sensu +strictiori_), the number of the radial spines is quite indeterminable and +their arrangement quite irregular and variable. + +A third remarkable genus, _Actinastrum_, differs from these two genera in +the definite number and regular order of thirty-two radial spines, and may +therefore perhaps better represent a peculiar family, Actinastrida. In this +genus (of which two species were observed) the thirty-two radial spines are +disposed in such a regular manner that they lie in four meridian planes, +and that their distal ends fall into five parallel zones. These five zones +and these four planes are the same as we find in all Icosacantha (compare +above, p. 717). Also the constant twenty spines of these latter are present +in _Actinastrum_; but their number is here enlarged by twelve other spines +missing in the Icosacantha; four of these are secondary or interradial +equatorial spines, lying opposite in pairs between the four primary or +perradial equatorial spines; and eight are perradial tropical spines, lying +between the eight interradial tropical spines. Therefore the {729}distal +ends of the thirty-two radial spines are disposed regularly in five +parallel zones, and while two zones (the two polar) contain only the points +of every four spines, three zones (the single equatorial and the two +tropical) contain the points of every eight spines. The four meridian +planes are in _Actinastrum_ the same as in the Icosacantha, crossed in the +spineless axis at angles of 45d. But in the Icosacantha each of the two +perradial meridian planes contains six radial spines (two equatorial and +four polar), each of the two interradial meridian planes only four tropical +spines. Whereas in _Actinastrum_ each of the two primary or perradial +meridian planes contains ten spines (two equatorial, four tropical, and +four polar), each of the two secondary or interradial meridian planes six +spines (two equatorial and four tropical). We find therefore altogether +thirty-two radial spines in three orders; eight equatorial, sixteen +tropical, and eight polar spines. + +Only one other genus of Radiolaria exhibits the same characteristic +disposition of thirty-two radial spines as _Actinastrum_, and this is +_Chiastolus_; but here the two opposite spines of each pair are grown +together and form one diametral spine; and the sixteen diametral spines are +crossed in the centre of the capsule. In _Actinastrum_, as in _Astrolophus_ +and _Actinelius_, the central ends or bases of all the spines are +pyramidal, and the triangular faces of the neighbouring spines rest one +upon another (as in the greater number of #Acanthonida#). The form of the +radial spines in all Astrolophida is quite simple, without lateral +processes or apophyses; chiefly cylindrical, more rarely compressed, +two-edged or quadrangular. + +The central capsule in all Astrolophida is spherical, and in the younger +specimens contains a single large concentric and lobed nucleus, but in the +older specimens a large number of small nuclei. The surrounding jelly-veil +or calymma seems commonly to envelop the spines perfectly. The piercing +pseudopodia radiate everywhere between the spines, and are very numerous +and thin. The circulating granules in them are sometimes red (_Actinelius +purpureus_). + +_Synopsis of the Genera of Astrolophida._ + + Radial spines of indefinite {Spines of equal size, 317. _Actinelius_. + number and of irregular { + disposition. {Spines of unequal size, 318. _Astrolophus_. + + Radial spines thirty-two, disposed regularly + in five parallel zones, 319. _Actinastrum_. + + + +Genus 317. _Actinelius_,[357] Haeckel, 1865, Zeitschr. f. wiss. Zool., Bd. +xv. p. 364. + +_Definition._--#Astrolophida# with a variable and undetermined number of +simple radial spines, all of equal size, united in the centre of the +spherical central capsule. + +{730}The genus _Actinelius_ comprises the most simple and primitive forms +among all ACANTHARIA, and may be regarded as the common ancestral stock of +this whole legion. The spherical central capsule is pierced by numerous +simple radial spines of equal size, the pyramidal bases of which are +supported one upon another with their triangular faces in the centre of the +capsule. The number and position of the spines are quite indefinite and +variable. We may derive _Actinelius_ either from _Actissa_ (#Colloidea#) by +development of acanthinic radial spines, or directly from _Actinosphaerium_ +(Heliozoa) by formation of a central capsule. + + + +Subgenus 1. _Actinelarium_, Haeckel. + +_Definition._--Radial spines cylindrical, conical, or spindle-shaped, their +transverse section circular. + + +1. _Actinelius primordialis_, n. sp. (Pl. 129, fig. 1). + +Spines sixty to eighty or more, cylindrical, at the distal end thickened, +spindle-shaped. Apex simple. Base a small slender pyramid. Central capsule +yellow. Granules of the sarcode colourless. + +_Dimensions._--Length of the spines 0.3 to 0.4, breadth in the distal part +0.02, in the basal part 0.008. + +_Habitat._--Central Pacific, Stations 265 to 274, surface. + + +2. _Actinelius purpureus_, Haeckel. + + _Actinelius purpureus_, Haeckel, 1865, Zeitschr. f. wiss. Zool., Bd. xv. + p. 364, Taf. xxvi. fig. 4. + +Spines thirty to forty or more, cylindrical, very thin, a little thinner +towards both ends. Apex simple. Base a small sulcate pyramid. Central +capsule opaque, purple. Granules of the sarcode also purple. + +_Dimensions._--Length of the spines 0.2 to 0.3, breadth 0.002. + +_Habitat._--Mediterranean (Nice), Haeckel. + + + +Subgenus 2. _Actinelidium_, Haeckel. + +_Definition._--Radial spines compressed, two-edged; their transverse +section elliptical or lanceolate. + + +3. _Actinelius protogenes_, n. sp. + +Spines fifty to sixty, compressed, two-edged, gradually broadened towards +the truncated distal end. Basal or proximal end thin, pyramidal. The spines +of this species are similar to those of {731}_Actinastrum pentazonium_ (p. +733) and of _Chiastolus amphicopium_ (Pl. 129, fig. 3), but much more +numerous, smaller, and not regularly disposed. These latter two Actinelida +must be separated on account of the regular disposition of the thirty-two +spines. + +_Dimensions._--Length of the spines 0.2, basal breadth 0.008, distal +breadth 0.02. + +_Habitat._--South Pacific, Station 165, surface. + + + +Subgenus 3. _Actinelonium_, Haeckel. + +_Definition._--Radial spines quadrangular, prismatic, or pyramidal, their +transverse section square. + + +4. _Actinelius pallidus_, Haeckel. + + _Actinelius pallidus_, Haeckel, 1865, Zeitschr. f. wiss. Zool., Bd. xv. + p. 364. + +Spines eighty to one hundred and twenty or more, quadrangular, prismatic, +of equal breadth throughout their whole length. Apex simple, truncate or +pyramidal. Base a four-sided slender pyramid. Central capsule pale +yellowish. Granules of the sarcode colourless. + +_Dimensions._--Length of the spines 0.2 to 0.3, breadth 0.005. + +_Habitat._--Cosmopolitan; Mediterranean, Atlantic, Pacific. + + +5. _Actinelius polyacanthus_, n. sp. + +Spines two hundred to three hundred or more, quadrangular, pyramidal, +gradually thinned towards the simple apex. Base a small three-sided +pyramid. Central capsule opaque. + +_Dimensions._--Length of the spines 0.12 to 0.18, basal breadth 0.012. + +_Habitat._--South Pacific, Station 291, surface. + + + +Genus 318. _Astrolophus_,[358] Haeckel, 1881, Prodromus, p. 469. + +_Definition._--#Astrolophida# with a variable and undetermined number of +simple radial spines of different sizes (large and small spines +intermingled), which are united in the centre of the spherical central +capsule. + +The genus _Astrolophus_ differs from the nearly allied ancestral genus +_Actinelius_ only in the unequal size of the numerous radial spines. In +both observed species very numerous small spines are intermingled with a +small number of large spines, and between them numerous spines of medium +size. The small spines fill up the hollow spaces between the basal parts of +the large spines. + + +{732}1. _Astrolophus stellaris_, n. sp. + +Radial spines from one hundred to two hundred, of very different sizes, but +of similar form; about sixteen to twenty very large spines, forty to fifty +of medium size, and one hundred to one hundred and twenty much smaller. All +spines cylindrical in the greater part of their length, with simple apex, +gradually thickened towards the central part, conical, without edges. The +base itself is a slender pyramid with four to eight edges. + +_Dimensions._--Length of the largest spines 0.3 to 0.4, of the majority 0.1 +to 0.2, of the smallest 0.05 to 0.1. + +_Habitat._--South Pacific, Station 288, surface. + + +2. _Astrolophus solaris_, n. sp. (Pl. 132, figs. 12_a_, 12_b_). + +Radial spines from two hundred to three hundred, of very different sizes, +but of similar form; about twenty to thirty very large spines, sixty to +eighty of medium size, and one hundred and twenty to one hundred and fifty +much smaller. All spines cylindrical in the greater part of their length, +with simple apex, gradually thickened and four-edged towards the central +base. The base itself is a slender pyramid with four to eight edges; partly +the faces, partly the edges of these basal pyramids rest one upon another, +the points of the larger spines meeting in the centre. + +_Dimensions._--Length of the largest spines 0.4 to 0.5, of the majority 0.2 +to 0.3, of the smallest 0.1 to 0.16; basal thickness of the largest spines +0.015. + +_Habitat._--South-east Pacific (off Juan Fernandez), Station 296, surface. + + + +Genus 319. _Actinastrum_,[359] n. gen. + +_Definition._--#Astrolophida# with thirty-two simple radial spines, +regularly disposed within four meridian planes in such an order that their +distal ends fall into five parallel zones. Central ends of the thirty-two +spines supported one upon another in the centre of the spherical central +capsule. + +The genus _Actinastrum_ differs from the two preceding genera in the +definite number and order of the thirty-two radial spines, which are +disposed in a very remarkable manner. Twenty radial spines are disposed +after the Muellerian law of Icosacantha (compare above, p. 717). The +remaining twelve spines are four equatorial spines lying in the two +secondary meridian planes, and eight tropical spines lying in the two +primary meridian planes. We have therefore together eight equatorial, +sixteen tropical, and eight polar spines (compare above, p. 729). + + +{733}1. _Actinastrum legitimum_, n. sp. + +All thirty-two radial spines of equal size and similar form, cylindrical, +conical at the distal end, at the central base pyramidal. Central capsule +pellucid, colourless. + +_Dimensions._--Length of the radial spines 0.3, breadth 0.004. + +_Habitat._--South Pacific, Station 288, surface. + + +2. _Actinastrum pentazonium_, n. sp. + +All thirty-two radial spines of equal size and similar form, compressed, +two-edged, gradually becoming broader and thinner from the pyramidal +central base towards the truncated distal end. Central capsule dark, +opaque. (Compare the similar _Chiastolus amphicopium_, Pl. 129, fig. 3.) + +_Dimensions._--Length of the radial spines 0.2, breadth at the base 0.005, +at the distal end 0.02. + +_Habitat._--South Pacific (west coast of Patagonia), Station 302, surface. + + + +Family XXXIV. LITHOLOPHIDA, Haeckel. + +_Litholophida_, Haeckel, 1862, Monogr. d. Radiol., p. 401. + +_Definition._--ACANTHARIA with a variable number of simple radial spines +radiating within a conical space (or within the quadrant of a sphere) from +one common central point, which is the apex of the conical central capsule. +No lattice-shell. + +The family #Litholophida#, represented only by a single genus, +_Litholophus_, differs from all other ACANTHARIA in the remarkable fact +that the common point, from which the radial spines arise, is not the +geometrical central point of the whole body, but is quite excentric in +position, the apex of the conical or pyramidal central capsule. Therefore +the spines form together a kind of brush or broom. + +When I founded the family Litholophida in my Monograph (1862, p. 401) I +knew only a single species, _Litholophus rhipidium_, observed very +frequently in Messina. Another species, _Litholophus ligurinus_, was +afterwards (1864) found by me at Nice. Six other species were detected in +the preparations of the Challenger, some of them very frequent. All these +eight species of _Litholophus_ are very nearly allied, and exhibit only +slight differences in the form and number of the radial spines; their mode +of excentric connection and the structure of the peculiar soft body is +everywhere the same. + +The radial spines in all observed Litholophida possess the form of the +genus _Acanthonia_, _i.e._, they are quite simple, four-sided prismatic or +quadrangular, with square transverse section; their four edges are +sometimes smooth, at other times elegantly denticulate, commonly more or +less prominent or wing-shaped. In the greater number of species they are +very long and of nearly equal breadth, prismatic; in some species they are +more pyramidal, thinned towards the distal end; the latter {734}is commonly +truncated or broken off, sometimes pyramidal. The central end is everywhere +thinned, more or less pyramidal, and the neighbouring spines are propped +one upon another by the triangular faces of their small basal pyramids. A +slight pressure is sufficient to destroy their connection. + +The number and disposition of the radial spines seem to be variable and +irregular, but require further researches. In four of the observed eight +species I found constantly ten spines, in two other species from ten to +twenty (commonly twelve or sixteen), and in two species twenty or more. A +certain order or disposition of the spines within the conical space in +which they radiate could nowhere be ascertained. + +When I first observed _Litholophus_, I supposed that it might only be a +mutilated or altered form of an _Acanthonia_. Afterwards, observing many +specimens with ten spines, I was led to the suggestion that they were +produced by self-division of an _Acanthonia_, and that the number of the +spines in each half of the body might be afterwards doubled. But this +suggestion seems to be refuted by the fact that in no other genus of the +numerous ACANTHARIA is self-division observed, and that many hundreds of +_Litholophus_ which I observed exhibit quite constantly only a single form +of radial spines, that of _Acanthonia_--simple quadrangular spines without +any apophyses. + + + +Genus 320. _Litholophus_,[360] Haeckel, 1862, Monogr. d. Radiol., p. 401. + +_Definition._--#Litholophida# with a variable number of quadrangular +diverging radial spines, united with pyramidal bases in the apex of the +conical central capsule. + +The genus _Litholophus_, the only one of this family, exhibits the +peculiarities just described, but might more nearly be defined as a typical +"genus" by the quadrangular form of the radial spines, identical with those +of _Acanthonia_. + +The central capsule of _Litholophus_ is constantly conical or pyramidal, +commonly opaque, of a dark brownish or reddish colour; it contains many +small nuclei. It envelops the basal half of all radial spines in such a +manner that their basal parts are united in its apex, and their distal +parts pierce the rounded base of the conical capsule (Pl. 129, fig. 2). + +The calymma or the jelly envelope of the central capsule is only developed +at its base, where the spines radiate; at the conical mantle of the capsule +it is very thin. The spines seem to be perfectly enclosed in the calymma +and connected with it by the same contractile retinacula or "myophrisca" +which we observe in the #Acanthonida#. The pseudopodia arise only from the +rounded base of the conical capsule, and radiate between the spines, +piercing the calymma, diverging within the conical space occupied by the +fascicle of spines. + + + +{735}Subgenus 1. _Litholopharium_, Haeckel. + +_Definition._--Ten radial spines. + + +1. _Litholophus decimalis_, n. sp. + +Ten radial spines, four-sided prismatic, with prominent smooth edges, of +equal breadth throughout their whole length. + +_Dimensions._--Length of the spines 0.2 to 0.3, breadth 0.006. + +_Habitat._--Cosmopolitan; Mediterranean, Atlantic, Indian, Pacific, +surface. + + +2. _Litholophus pyramidalis_, n. sp. + +Ten radial spines, four-sided pyramidal, with prominent smooth edges, +gradually thickened from the small pyramidal base towards the truncated +distal end. + +_Dimensions._--Length of the spines 0.3 to 0.4, breadth in the basal part +0.002, in the middle part 0.006, in the distal part 0.012 to 0.02. + +_Habitat._--Central Pacific, Station 266, surface. + + +3. _Litholophus decapristis_, n. sp. (Pl. 129, fig. 2). + +Ten radial spines, four-sided prismatic, with prominent, elegantly +denticulated edges, of equal breadth in their whole length. + +_Dimensions._--Length of the spines 0.2 to 0.4, breadth 0.008. + +_Habitat._--Cosmopolitan; Mediterranean, Atlantic, Pacific, surface. + + +4. _Litholophus decastylus_, n. sp. + +Ten radial spines, four-winged pyramidal, with broad and thin, elegantly +denticulated edges, gradually thickened from the small pyramidal base +towards the truncated distal end. + +_Dimensions._--Length of the spines 0.2 to 0.3, breadth in the basal part +0.002, in the middle part 0.005, in the distal part 0.015. + +_Habitat._--South Atlantic, Station 332, surface. + + + +Subgenus 2. _Litholophidium_, Haeckel. + +_Definition._--Number of the radial spines variable, between ten and +twenty, commonly twelve to sixteen. + + +{736}5. _Litholophus ligurinus_, Haeckel. + + _Litholophus ligurinus_, Haeckel, 1865, Zeitschr. f. wiss. Zool., Bd. xv. + p. 366. + +Spines of variable number, from eleven to twenty, commonly twelve to +sixteen, four-sided prismatic, with smooth thin edges, of equal breadth in +their whole length or a little thinner towards the proximal end. + +_Dimensions._--Length of the spines 0.3, breadth 0.005. + +_Habitat._--Mediterranean (Nice); Central Pacific, Station 274, surface. + + +6. _Litholophus rhipidium_, Haeckel. + + _Litholophus rhipidium_, Haeckel, 1862, Monogr. d. Radiol., p. 402, Taf. + xix. fig. 6. + +Spines of variable number, from eleven to twenty, commonly twelve to +sixteen, four-sided prismatic, with distantly denticulated edges, of equal +breadth in their whole length or a little thinner towards both ends. + +_Dimensions._--Length of the spines 0.3, breadth 0.006. + +_Habitat._--Mediterranean (Messina); North Atlantic, Station 352, surface. + + + +Subgenus 3. _Litholophonium_, Haeckel. + +_Definition._--Number of the radial spines twenty (or more?). + + +7. _Litholophus fasciculus_, n. sp. + +Spines constantly (?) twenty, four-sided prismatic, with smooth prominent +edges, nearly of equal breadth throughout their whole length. + +_Dimensions._--Length of the spines 0.3 to 0.5, breadth 0.008. + +_Habitat._--South Pacific, Station 291, surface. + + +8. _Litholophus penicillus_, n. sp. + +Spines constantly twenty (or more?), four-sided prismatic, with distantly +denticulated edges, gradually thickened from the small pyramidal base to +the middle part, of equal breadth in the distal half. + +_Dimensions._--Length of the spines 0.3 to 0.4, breadth 0.005 to 0.007. + +_Habitat._--North Pacific, Station 252, surface. + + + +Family XXXV. #CHIASTOLIDA#, Haeckel. + +_Acanthochiasmida_, Haeckel, 1862, Monogr. d. Radiol., p. 402. + +_Definition._--ACANTHARIA with a variable number of simple radial spines, +which are grown together in pairs (two opposite spines of each pair +representing together a single diametral spine). Diametral spines crossed +loosely in the centre of the spherical or irregular roundish central +capsule. No lattice-shell. + +{737}The family #Chiastolida# (or Acanthochiasmida) differs from all other +ACANTHARIA in the peculiar mode of the radial spines; these grown together +in pairs in the centre of the body, so that every two spines opposite in +one axis of the body form together one single diametral spine. All +diametral spines are loosely crossed in the middle of the central capsule, +or connected by a peculiar screw-like winding, but not united firmly. + +I established the family Acanthochiasmida in my Monograph (1862, p. 402) +upon the single genus _Acanthochiasma_ (with three species), in which only +ten diametral spines are constantly found; I derived these from the twenty +radial spines of the common #Acanthometra#, supposing that every two +opposite spines of the latter (lying in one axis) were grown together in +the centre, whilst the intimate connection of the twenty radial spines in +the common centre was dissolved. This opinion was afterwards confirmed by +Richard Hertwig, who observed _Acanthochiasma_ intact in the living state. +Although two species of this genus are cosmopolitan and very common, the +number of species is very small; I could add to those three older known +forms only a single new species. + +Another genus of this family, _Chiastolus_, was observed by me only in a +single specimen but it is extremely interesting. It has sixteen diametral +spines, disposed quite regularly after the same law of the thirty-two +spines of _Actinastrum_ which we described above (compare above, p. 729). +Therefore we cannot doubt that the former is derived from the latter in the +same way, every two opposite radial spines (of one axis) being grown +together to form a single diametral spine. As we place _Acanthometron_ +(with twenty spines) and _Actinastrum_ (with thirty-two spines) in two +different families, it would perhaps be more convenient to separate also +_Acanthochiasma_ and _Chiastolus_ as representatives of two different +families--Acanthochiasmida (with ten diametral spines) and Chiastolida +(with sixteen diametral spines). + +As we derive _Acanthochiasma_ from _Acanthometron_ by concrescence in pairs +of the twenty radial spines, the Muellerian law of Icosacantha must be +employed also to the ten diametral spines of the former, therefore two of +them are equatorial, four tropical, and four polar spines. In the same way +we may employ the new law of disposition found in the thirty-two radial +spines of _Actinastrum_ equally to the sixteen diametral spines of +_Chiastolus_, which we derive from the former, four of them are equatorial, +eight tropical, and four polar spines (compare above, p. 732). + +_The Central Capsule_ of the Chiastolida is spherical, and exhibits in +general the same shape as in the #Acanthonida#, and specially in the +Astrolonchida. Of course every diametral spine pierces the capsule twice, +at two points diametrically opposed. In some species of _Acanthochiasma_ +the central capsule is formed very late, so that it seems often to be +absent. A very accurate description of the capsule and its nucleus, as well +as of the calymma and the pseudopodia, is given by Richard Hertwig in his +Organismus der Radiolarien (1879, pp. 10-18). The pseudopodia are very +numerous, and sometimes bear reddish granules. + +{738}_Synopsis of the Genera of Chiastolida._ + + I. Subfamily Chiastolidina. Sixteen diametral + spines, derived by concrescence of thirty-two + radial spines, 321. _Chiastolus_. + + II. Subfamily Acanthochiasmida. Ten diametral + spines, derived by concrescence of twenty + radial spines, 322. _Acanthochiasma_. + + + +Genus 321. _Chiastolus_,[361] n. gen. + +_Definition._--#Chiastolida# with sixteen diametral spines, derived from +thirty-two radial spines opposite and grown together in pairs. + +The genus _Chiastolus_, hitherto known only by a single observed specimen, +comprises the Chiastolida with sixteen diametral spines, which are loosely +crossed in the centre of the body. Four of these spines are equatorial, +four polar, and eight tropical. We derive _Chiastolus_ from _Actinastrum_ +by concrescence of every two opposite spines in one axis of the body +(compare above, pp. 729, 732). + + +1. _Chiastolus amphicopium_, n. sp. (Pl. 129, figs. 3, 3_a_, 3_b_). + +Spines in the central part cylindrical, spirally convoluted in a very +peculiar manner, broadened towards both ends, strongly compressed, +two-edged; the broadest parts are the two truncated distal ends, five to +seven times as broad as the thinnest central part, which is placed between +two spindle-shaped intumescences. These cochleary central parts of the +sixteen spines seem to be resting one upon another. Each spine (composed of +two opposite equal radial spines) has nearly the form of a double oar. The +single observed specimen (preserved in glycerine) exhibited a most regular +disposition of the thirty-two spines (grown together in pairs in the +centre). The diameter of the dark non-transparent spherical central capsule +equalled one-fifth to one-fourth of the total length of the double spines. +When the soft parts of the body were destroyed by sulphuric acid, the +sixteen single spines were suddenly dispersed. + +_Dimensions._--Length of the sixteen double spines 0.5, distal breadth (of +the truncated ends) 0.05, central breadth 0.01; diameter of the central +capsule 0.12. + +_Habitat._--South-east Pacific (near Juan Fernandez), Station 297, surface. + + + +Genus 322. _Acanthochiasma_,[362] Krohn, 1860, Monatsber. d. k. preuss. +Akad. d. Wiss. Berlin, p. 810. + +_Definition._--#Chiastolida# with ten diametral spines, derived from twenty +radial spines opposite and grown together in pairs. + +{739}The genus _Acanthochiasma_ with a small number of common species, +comprises the Chiastolida with ten diametral spines, which are loosely +crossed in the centre of the body. I could distinguish only four species, +two of which are cosmopolitan and very widely distributed. In all four +species the diametral spines are quite simple, cylindrical; only in one +species distinguished by a spiral winding or torsion in the middle part, +where they are crossed one to another. We derive _Acanthochiasma_ from +_Acanthometron_ by concrescence of every two spines opposite in one axis of +the body. + + +1. _Acanthochiasma krohnii_, Haeckel. + + _Acanthochiasma krohnii_, Haeckel, 1862, Monogr. d. Radiol., p.403, Taf. + xix. fig. 7. + + _Acanthochiasma krohnii_, R. Hertwig, 1879, Organismus d. Radiol., Taf. + ii. fig. 6. + +Spines needle-shaped, cylindrical, very thin and long, of equal breadth in +their whole length, distinguished by a high degree of elasticity. Central +capsule colourless or yellowish-white, transparent. Granules of the sarcode +colourless. + +_Dimensions._--Length of the spines 0.5 to 1.0, breadth 0.001 to 0.002. + +_Habitat._--Cosmopolitan; Mediterranean, Atlantic, Indian, Pacific, very +common. + + +2. _Acanthochiasma rubescens_, Krohn. + + _Acanthochiasma rubescens_, Haeckel, 1862, Monogr. d. Radiol., p. 403. + +Spines cylindrical, of equal breadth in their whole length, not very +elastic, pointed at the two ends. Central capsule intransparent, reddish, +with violin-shaped concretions. Granules of the sarcode red coloured. + +_Dimensions._--Length of the spines 0.2 to 0.6, breadth 0.004 to 0.006. + +_Habitat._--North Atlantic, Madeira, Krohn; Lanzerote, Haeckel. + + +3. _Acanthochiasma fusiforme_, Haeckel. + + _Acanthochiasma fusiforme_, Haeckel, 1862, Monogr. d. Radiol., p. 404, + Taf. xix. fig. 8. + +Spines spindle-shaped, from the thicker central part thinned towards the +two thin conical ends, perfectly straight and smooth, rigid, inelastic. +Central capsule non-transparent, brown. + +_Dimensions._--Length of the spines 0.3 to 0.5, breadth in the central part +0.006 to 0.009. + +_Habitat._--Cosmopolitan; Mediterranean, Atlantic, Pacific. + + +4. _Acanthochiasma spirale_, n. sp. + +Spines spindle-shaped, tapering from the thicker central part towards the +two thin conical ends, rigid, inelastic; their central part is spirally +convoluted in a very peculiar cochlea-like manner, as in _Chiastolus +amphicopium_ (Pl. 129, figs. 3_a_, 3_b_). The ten spines are propped one +upon another by the central screw. Central capsule dark, opaque. + +_Dimensions._--Length of the spines 0.2 to 0.3, breadth of the central +spiral part 0.01. + +_Habitat._--Central Pacific, Station 266, surface. + + +{740}---- + + +Suborder II. ACANTHONIDA, Haeckel (Pls. 130-132). + +_Acanthonida_, Haeckel, 1881, Prodromus, p. 465. + +_Definition._--#Acanthometra# with twenty radial spines, disposed according +to the Muellerian or Icosacanthan law in five zones each of four spines. + + + +Family XXXVI. #ASTROLONCHIDA#, Haeckel (Pl. 130). + +_Astrolonchida_, Haeckel, 1881, Prodromus, p. 465. + +_Definition._--#Acanthometra# with twenty radial spines of nearly equal +size and similar form, disposed according to the law of the Icosacantha. No +lattice-shell. + +The family #Astrolonchida#, the first and oldest of the #Acanthonida#, is +no doubt the ancestral stock not only of this suborder but also all +#Acanthophracta#, _i.e._, of all Icosacantha or all ACANTHARIA in which +twenty radial spines are regularly disposed according to the Muellerian +law, forming five zones each of four alternating spines (compare above, p. +717). The Astrolonchida differ from the #Acanthophracta# in the absence of +a complete lattice-shell, from the other two families of #Acanthonida# (the +Quadrilonchida and Amphilonchida) in the equal size and similar form of all +the spines. Probably this equality is nowhere quite perfect, since in all +Icosacantha the central bases of the twenty spines exhibit originally +certain slight differences of form and junction, effected by the regular +disposition itself. But setting aside this slight difference, only +recognisable by means of a very accurate investigation of the central +junction (and in thinner spines often not at all recognisable), the twenty +spines of the Astrolonchida appear perfectly equal. Therefore the four +equatorial spines are not distinguished from the sixteen other spines, as +is constantly the case in the two following families. + +The number of genera (eleven) and of species (seventy-six) in the +Astrolonchida is far larger than in the five other families of +#Acanthometra#, and requires a distinction into three different +subfamilies. (A) In the Zygacanthida the form of the radial spines is quite +simple, without apophyses or transverse processes; (B) in the +Phractacanthida each spine bears two opposite apophyses (rarely two +longitudinal rows of these opposite apophyses); (C) in the Stauracanthida +each spine bears a cross of four apophyses, opposite in pairs (rarely four +longitudinal crossed rows of apophyses, opposite in pairs). The +Phractacanthida and Stauracanthida appear as two divergent branches of the +pedigree, derived independently from the common ancestral stock of +Zygacanthida. + +In the Zygacanthida, constantly devoid of apophyses, we can distinguish +only three genera, characterised by the different fundamental form of the +radial spines; these are:--(1) _Acanthometron_, with cylindrical or conical +spines (without edges); (2) _Zygacantha_, with compressed and two-edged +spines; (3) _Acanthonia_, with four-edged, prismatic or pyramidal spines. +The transverse section of the spines is in the first case {741}circular, in +the second elliptical or lanceolate, in the third square. All the different +forms of spines, which we find in the numerous ACANTHARIA, may be reduced +to these three forms, and among these the second and third are derived from +the first. + +The development of apophyses or of lateral transverse processes (wanting in +the Zygacanthida) is of the greatest value for the further differentiation +of the ACANTHARIA. For from the Phractacanthida (with two opposite +apophyses on each spine) we must derive the Phrastaspida, the common +ancestral stock of the Diporaspida (and therefore also the Belonaspida, +Hexalaspida, Diploconida, and Phractopeltida). On the other hand the +Stauracanthida (with four crossed apophyses on each spine) have produced +the Stauraspida, or the ancestral group of the Tessaraspida and +Sphaerocapsida. From all these #Acanthophracta#, possessing a complete +lattice-shell, the Astrolonchida differ in the absence of such a complete +shell. Also in the few cases in which the apophyses become latticed +(_Doracantha_ among the Phractacanthida, and _Phatnacantha_ among the +Stauracanthida), the lattice-plates of the neighbouring spines never meet +with their edges, as is the case in all #Acanthophracta#. But in a +phylogenetic as well as in an ontogenetic sense the former are the +ancestral stock of the latter. + +_The Central Capsule_ in the Astrolonchida is commonly spherical, sometimes +with twenty roundish elevations or conical papillae, extending radially to +the basal half of the radial spines. The calymma is voluminous, and forms +around the radial spines conical or cylindrical "jelly-sheaths," which are +connected with the spines by coronas of Myophrisca (or of the bodies +formerly called "Gallert-cilien," afterwards recognised as "contractile +Filamente"). + +_Synopsis of the Genera of Astrolonchida._ + + ------------------------------------------------------------------------- + I. Subfamily Zygacanthida. + Twenty radial spines simple, without apophyses or lateral transverse + processes. + ------------------------------------------------------------------------- + Spines cylindrical, with circular transverse + section, 323. _Acanthometron_. + + Spines compressed, two-edged or lamellar, with + elliptical or rhomboidal transverse section, 324. _Zygacantha_. + + Spines quadrangular (prismatic or pyramidal), with + four edges, with square transverse section, 325. _Acanthonia_. + + ------------------------------------------------------------------------- + II. Subfamily Phractacanthida. + Twenty radial spines provided each with two opposite apophyses (or + two longitudinal rows of apophyses). + ------------------------------------------------------------------------- + { Apophyses simple, 326. _Lithophyllium_. + { + Two apophyses opposite on { Apophyses branched, 327. _Phractacantha_. + each spine. { + { Apophyses latticed, 328. _Doracantha_. + + Two opposite longitudinal rows of apophyses (four + to eight or more apophyses on each spine, + opposite in pairs), 329. _Astrolonche_. + ------------------------------------------------------------------------- + III. Subfamily Stauracanthida. + Twenty radial spines provided each with four crossed apophyses (or + four crossed longitudinal rows of apophyses). + ------------------------------------------------------------------------- + { Apophyses simple, 330. _Xiphacantha_. + Four apophyses (in cross { + form) opposite in pairs { Apophyses branched, 331. _Stauracantha_. + on each spine. { + { Apophyses latticed, 332. _Phatnacantha_. + + Four longitudinal rows of apophyses, opposite in + pairs in cross form on each spine, 333. _Pristacantha_. + + + +{742}Subfamily 1. ZYGACANTHIDA, Haeckel. + +_Definition._--#Astrolonchida# with twenty simple radial spines, without +apophyses or lateral transverse processes. + + + +Genus 323. _Acanthometron_,[363] J. Mueller, 1855, Monatsber. d. k. preuss. +Akad. d. Wiss. Berlin, p. 229. + +_Definition._--#Astrolonchida# with simple cylindrical or needle-shaped +radial spines, without edges and without apophyses; their transverse +section is circular. + +The genus _Acanthometron_, with the restricted definition here given, is +the most simple form of all #Acanthonida#, and may be regarded as the +common ancestral form not only of this suborder but also of all +#Acanthophracta#, in general of all Icosacantha, or all ACANTHARIA in which +twenty radial spines are regularly disposed after the Muellerian law (p. +717). In the wider sense, given originally to #Acanthometra# by Johannes +Mueller, its discoverer, this genus comprised all ACANTHARIA constituting +here our order "#Acanthometra#" (Radiolaria without lattice-shell, with +radial spines united in the centre). In my Monograph (1862, p. 375) I +restricted this genus to those "Acanthometrida" in which twenty simple +spines of equal size (and without apophyses) are supported one upon another +in the centre, and I separated as _Astrolithium_ those forms in which they +are grown together in the centre. But this difference now appears not so +important, and I restrict here the genus _Acanthometron_ (not +#Acanthometra#) to those most simple forms in which the simple radial +spines are cylindrical or conical, without edges. + + + +Subgenus 1. _Acanthometrella_, Haeckel. + +_Definition._--Spines at the central base without leaf-cross, united by the +opposed triangular faces of their pyramidal bases, resting one upon +another. + + +1. _Acanthometron elasticum_, Haeckel. + + _Acanthometra elastica_, Haeckel, 1862, Monogr. d. Radiol., p. 376, Taf. + xv. fig. 1, Taf. xviii. fig. 1. + + _Acanthometra elastica_, R. Hertwig, 1879, Organismus d. Radiol., Taf. i. + figs. 2, 2_a_, 2_b_. + +Spines cylindrical, very thin and long, needle-shaped, at the central base +four-sided pyramidal, without leaf-cross. Distal apex conical. The spines +are very elastic, of nearly equal thickness in their whole length. Central +capsule quite pellucid, colourless, with a variable number of yellow +pigment-bodies (xanthellae?). + +_Dimensions._--Length of the spines 0.3 to 0.6, breadth 0.001 to 0.002. + +_Habitat._--Cosmopolitan, very common in all warmer seas; Mediterranean, +Atlantic, Indian, Pacific, surface. + + +{743}2. _Acanthometron cylindricum_, n. sp. (Pl. 130, fig. 2). + +Spines cylindrical, thick and long, at the central base thickened with a +pear-shaped knob, and with very small central fulcral pyramid, without +leaf-cross. Distal apex rounded or truncated. Central capsule opaque, +filled with red pigment-bodies. + +_Dimensions._--Length of the spines 0.4 to 0.8, breadth 0.01 to 0.015. + +_Habitat._--Central Pacific, Stations 266 to 274, surface. + + +3. _Acanthometron fuscum_, J. Mueller. + + _Acanthometra fusca_, J. Mueller, 1858, Abhandl. d. k. Akad. d. Wiss. + Berlin, p. 47, Taf. xi. fig. 4. + + _Acanthometra fusca_, Haeckel, 1862, Monogr. d. Radiol, p. 377. + +Spines very thin and long, in the proximal half cylindrical, in the distal +half conical, gradually thinned towards the simple conical apex. Central +base a small four-sided pyramid, without leaf-cross. Central capsule +opaque, filled with brown pigment-bodies. + +_Dimensions._--Length of the spines 0.2 to 0.4, breadth 0.002 to 0.004. + +_Habitat._--Mediterranean (Cette, Portofino, Messina). + + +4. _Acanthometron bulbosum_, Haeckel. + + _Acanthometra bulbosa_, Haeckel, 1862, Monogr. d. Radiol., p. 377, Taf. + xv. fig. 2, Taf. xviii fig. 2. + +Spines very thin and long, cylindrical, with simple needle-shaped apex; in +the basal part conical, towards the centre much thickened, with a short +four-sided fulcral pyramid, without leaf-cross. Central capsule opaque, +filled with brown pigment-bodies. + +_Dimensions._--Length of the spines 0.3 to 0.5, breadth in the middle and +outer part 0.001, in the basal part 0.008 to 0.012. + +_Habitat._--Mediterranean; Atlantic, Station 354, surface. + + +5. _Acanthometron dolichoscion_, Haeckel (Pl. 129, figs. 6-8). + + _Acanthometra dolichoscia_, Haeckel, 1862, Monogr. d. Radiol., p. 377, + Taf. xviii. figs. 3_a_, 3_b_. + +Spines very long and thin, cylindrical, in the thickened outer half about +twice as thick as in the thin inner half, at the simple apex compressed, +two-edged. Central base little thickened, with a small four-sided pyramid, +without leaf-cross. Central capsule transparent, whitish or yellowish. + +_Dimensions._--Length of the spines 0.6 to 0.8, breadth in the proximal +part 0.004, in the distal part 0.008. + +_Habitat._--Mediterranean (Messina, Portofino), surface. + + +6. _Acanthometron conicum_, n. sp. + +Spines short and thick, conical, gradually thinner from the thick conical +base towards the simple apex. Central part of the base with a large fulcral +pyramid, but without leaf-cross. Central capsule transparent, colourless +(?). + +_Dimensions._--Length of the spines 0.08 to 0.12, basal breadth 0.02. + +_Habitat._--North Pacific, Station 244, surface. + + +{744}7. _Acanthometron pellucidum_, J. Mueller. + + _Acanthometra pellucida_, J. Mueller, 1858, Abhandl. d. k. Akad. d. Wiss. + Berlin, p. 47, Taf. xi. figs. 1-3. + + _Acanthometra pellucida_, Haeckel, 1862, Monogr. d. Radiol., p. 378. + +Spines cylindrical, very thin and long, needle-shaped, nearly of equal +thickness in their whole length. Central base with a small fulcral pyramid, +without leaf-cross. Distal apex bifid or bifurcate, with two thin parallel +teeth. Central capsule pellucid, colourless, with yellow pigment-bodies. +(Differs from _Acanthometron elasticum_ mainly in the bifid apex.) + +_Dimensions._--Length of the spine 0.1 to 0.3, breadth 0.002 to 0.004. + +_Habitat._--Cosmopolitan; Mediterranean, Atlantic, Pacific, surface. + + +8. _Acanthometron wageneri_, Haeckel. + + _Acanthometra wageneri_, Haeckel, 1862, Monogr. d. Radiol., p. 378. + +Spines cylindrical, in the thickened outer half about twice as broad as in +the thin inner half. Central base a little thickened, with large fulcral +pyramid, but without leaf-cross. Distal apex bifid, with two divergent, +often denticulated teeth. Central capsule pellucid, with yellow +pigment-bodies. (Differs from _Acanthometron dolichoscion_ mainly in the +bifid apex.) + +_Dimensions._--Length of the spines 0.2 to 0.5, breadth in the inner part +0.003, in the outer 0.006. + +_Habitat._--Adriatic Sea; Triest, Wagner; Corfu, Haeckel, surface. + + + +Subgenus 2. _Phyllostaurus_, Haeckel, 1862, Monogr. d. Radiol., p. 381. + +_Definition._--Spines at the central base with a broad leaf-cross, composed +of four prominent triangular lamellae; the meeting edges of the +neighbouring lamellae are propped one upon another in such a manner that +there are formed twenty-two hollow pyramidal spaces or compartments +(compare p. 721). + + +9. _Acanthometron siculum_, Haeckel. + + _Acanthometra sicula_, Haeckel, 1862, Monogr. d. Radiol., p. 382, Taf. + xvii. figs. 1, 2; Taf. xviii. fig. 8. + +Spines elongate, conical, tapering gradually from the thick base towards +the simple distal apex. Conical circular base supported by a basal +leaf-cross of double the breadth. Central capsule yellowish-brown, opaque. + +_Dimensions._--Length of the spines 0.3 to 0.4, basal breadth 0.008 to +0.012, leaf-cross 0.024. + +_Habitat._--Cosmopolitan; Mediterranean, Atlantic, Pacific, surface. + + +{745}10. _Acanthometron catervatum_, Haeckel. + + _Acanthometra brevispina_, Haeckel, 1862, Monogr. d. Radiol., p. 382, + Taf. xv. fig. 5, Taf. xviii. fig. 9. + +Spines cylindrical, nearly of equal breadth throughout their whole length. +Apex either simple, conical, or bifid. Base with a large leaf-cross, four +to six times as broad as the spine itself. Central capsule transparent, +yellow. The Atlantic specimens have much longer spines than those figured +from the Mediterranean, but are otherwise not different. Therefore I have +changed the inconvenient name _brevispinum_ into _catervatum_. + +_Dimensions._--Length of the spines 0.1 to 0.3, breadth 0.005 to 0.008; +basal leaf-cross 0.02 to 0.032. + +_Habitat._--Mediterranean (Messina); North Atlantic, Station 354, Gulf +Stream (Faeroee Channel) in great abundance, John Murray, surface. + + + +Subgenus 3. _Astrolithium_, Haeckel, 1860, Monatsber. d. k. preuss. Akad. +d. Wiss. Berlin, p. 810. + +_Definition._--Spines in the basal part grown perfectly together, so that +the whole skeleton forms a single piece of acanthin; a star with twenty +equal rays. + + +11. _Acanthometron bulbiferum_, n. sp. (Pl. 130, fig. 1). + + _Astrolithium bulbiferum_, Haeckel, 1881, Prodromus, p. 466. + +Spines needle-shaped, cylindrical, very thin and long, with simple apex; +suddenly thickened and forming a broad regular cone at the central base; +all twenty conical bulbs have their broad bases grown together and forming +a central icosahedron of acanthin; from its twenty faces arise the circular +bases of the cones in regular disposition. + +_Dimensions._--Length of the spines 0.2 to 0.5, breadth 0.001 to 0.003; +height of the basal cones 0.06, basal breadth of them 0.02. + +_Habitat._--Central Pacific, Stations 265 to 274, surface. + + +12. _Acanthometron bifidum_, Haeckel. + + _Astrolithium bifidum_, Haeckel, 1862, Monogr. d. Radiol., p. 400, Taf. + xx. fig. 5. + +Spines needle-shaped, cylindrical, of equal breadth in their whole length. +Distal apex bifid, with two parallel straight teeth. Central bases of all +twenty spines grown perfectly together and forming a central sphere of +acanthin. Central capsule brown opaque. + +_Dimensions._--Length of the spines 0.2, breadth 0.003. + +_Habitat._--Mediterranean (Messina), Haeckel, surface. + + + +{746}Genus 324. _Zygacantha_,[364] J. Mueller, 1858, Abhandl. d. k. Akad. +d. Wiss. Berlin, p. 51. + +_Definition._--#Astrolonchida# with simple, compressed, and two-edged +radial spines, without apophyses; their transverse section is elliptical or +rhomboidal. + +The genus _Zygacantha_ comprised in the original definition of J. Mueller +only a single species, _Zygacantha furcata_, distinguished from the other +#Acanthometra# by forked spines with two long parallel teeth. It seems now +advisable to unite in this genus all those Astrolonchida in which the +simple spines are two-edged, compressed, or leaf-shaped. The term +_Zygacantha_ may be conceived as the general expression of the important +fact, that in all Icosacantha the twenty spines are opposite in pairs. + + + +Subgenus 1. _Zygacantharium_, Haeckel. + +_Definition._--Spines at the central base without leaf-cross and without +hollow pyramidal compartments, united by the opposed triangular faces of +their pyramidal bases, resting one upon another. + + +1. _Zygacantha lanceolata_, Haeckel. + + _Acanthometra lanceolata_, J. Mueller, 1858, Abhandl. d. k. Akad. d. + Wiss. Berlin, p. 48, Taf. xi. fig. 12. + + _Acanthometra lanceolata_, Haeckel, 1862, Monogr. d. Radiol., p. 380. + +Spines lanceolate, from the broader middle part equally thinned towards the +two ends. Apex simple. Base pyramidal, without leaf-cross. Each flat +lamellar spine exhibits an elevated middle rib (like a lanceolate leaf), +and is therefore compressed quadrangular. + +_Dimensions._--Length of the spines 0.1 to 0.15, greatest breadth (in the +width) 0.03 to 0.04. + +_Habitat._--Mediterranean (Saint Tropez, French shore), J. Mueller; North +Atlantic (Canary Islands), Haeckel, surface. + + +2. _Zygacantha costata_, n. sp. + +Spines compressed, two-edged, linear, of nearly equal breadth in their +whole length. Apex truncate. Base pyramidal, without leaf-cross. Each flat +lamellar spine exhibits an elevated middle rib, which in the distal half is +cleft into two divergent rods ending in the corners of the truncated apex. +(Similar to _Zygacantha dicopa_, but with broader free spines, which are +not grown together in the centre.) + +_Dimensions._--Length of the spines 0.1 to 0.15, breadth 0.02. + +_Habitat._--Central Pacific, Stations 265 to 274, surface. + + +{747}3. _Zygacantha compressa_, Haeckel. + + _Acanthometra compressa_, Haeckel, 1862, Monogr. d. Radiol., p. 378, Taf. + xviii. figs. 4_a_, 4_b_. + +Spines in the proximal half compressed, broad lanceolate, four to six times +as broad as in the thin cylindrical distal half. Apex simple or short +bifid. Base pyramidal, thickened, without leaf-cross. No middle rib. +Central capsule opaque, yellowish or reddish-brown. + +_Dimensions._--Length of the spines 0.3 to 0.5, breadth of the inner half +0.015 to 0.02, of the outer half 0.002 to 0.003. + +_Habitat._--Mediterranean (Messina); Atlantic (Canary Islands), Station +352, surface. + + +4. _Zygacantha furcata_, J. Mueller. + + _Zygacantha furcata_, J. Mueller, 1858, Abhandl. d. k. Akad. d. Wiss. + Berlin, p. 51, Taf. ix. fig. 6. + + _Acanthometra furcata_, J. Mueller, 1856, Monatsber. d. k. preuss. Akad. + d. Wiss. Berlin, p. 499. + + _Acanthometra furcata_, Haeckel, 1862, Monogr. d. Radiol., p. 380. + +Spines compressed, fork-shaped, divided by two thickened knots into three +sections of nearly equal length; middle section broader than the proximal, +but smaller than the distal section, which is cleft by a deep fissure into +two long parallel straight branches. Base pyramidal, without leaf-cross. +Central capsule purple, with yellow bodies. + +_Dimensions._--Length of the spines 0.1 to 0.15, basal breadth 0.003 to +0.005, distal breadth 0.02 to 0.03. + +_Habitat._--Mediterranean (Cette). J. Mueller, surface. + + + +Subgenus 2. _Zygacanthidium_, Haeckel. + +_Definition._--Spines at the central base with a cross of four prominent +leaves; the meeting edges of the neighbouring lamellae so rest one upon +another that twenty-two hollow pyramidal compartments are formed (compare +p. 721). + + +5. _Zygacantha dichotoma_, Haeckel. + + _Zygacantha dichotoma_, Haeckel, 1862, Monogr. d. Radiol., p. 381. + + _Acanthometra dichotoma_, J. Mueller, 1858, Abhandl. d. k. Akad. d. Wiss. + Berlin, p. 50, Taf. ix. fig. 5. + +Spines compressed, pincer-shaped, cleft nearly throughout their whole +length into two thin parallel straight rods or fork branches, which are +united only in their middle by a narrow bridge, and at their central base +by the pyramidal small central apex; above this pyramid each rod is divided +into two broad triangular leaves, forming a large basal leaf-cross. Central +capsule purple, with yellow bodies. + +_Dimensions._--Length of the spines 0.1 to 0.15, breadth 0.01 to 0.02. + +_Habitat._--Mediterranean (Nice), J. Mueller, surface. + + +{748}6. _Zygacantha complanata_, n. sp. + +Spines compressed, two-edged, linear, of equal breadth throughout their +whole length. Apex bifid. Base thickened, with a large leaf-cross. (Similar +to _Amphilonche complanata_, but different in the equal size of all twenty +spines, which are somewhat broader.) + +_Dimensions._--Length of the spines 0.12 to 0.18, breadth 0.002. + +_Habitat._--North Pacific, Station 244, surface. + + +7. _Zygacantha semicompressa_, Haeckel. + + _Acanthometra hemicompressa_, Car, 1884, Zool. Anzeiger, p. 94, with + woodcut. + +Spines in the proximal half compressed, two-edged, linear, three to four +times as broad as in the needle-shaped cylindrical distal half. Apex +simple. Base pyramidal, with a small leaf-cross. Central capsule +transparent. + +_Dimensions._--Length of the spines 0.1 to 0.2, breadth in the proximal +half 0.02, in the distal half 0.006. + +_Habitat._--Mediterranean (Genoa), Haeckel; Adriatic Sea (Trieste), Car, +surface. + + +8. _Zygacantha foliacea_, n. sp. + +Spines lanceolate, tapering from the broader middle part towards the two +ends, with two dentated or serrated edges and a prominent middle rib. Apex +simple. Base with a small leaf-cross. The spines like the leaves of _Agave +americana_. + +_Dimensions._--Length of the spines 0.15 to 0.2, middle breadth 0.02 to +0.03. + +_Habitat._--Indian Ocean, near the Island of Socotra, Haeckel. + + + +Subgenus 3. _Zygacanthonium_, Haeckel. + +_Definition._--Spines in the centre grown perfectly together and forming a +single star-shaped piece of acanthin. + + +9. _Zygacantha dicopa_, Haeckel. + + _Astrolithium dicopum_, Haeckel, 1862, Monogr. d. Radiol., p. 400, Taf. + xx. figs. 3, 4. + +Spines compressed, two-edged, linear, of nearly equal breadth throughout +their whole length, with a prominent middle rib, which in the distal third +is cleft into two divergent teeth, ending in the two corners of the broad, +obliquely truncated apex. All twenty spines with their central bases grown +together and forming one single piece of acanthin--a star with twenty rays. + +_Dimensions._--Length of the spines 0.12 to 0.2, breadth 0.01 to 0.02. + +_Habitat._--Cosmopolitan; Mediterranean, Atlantic, Pacific, many Stations, +surface. + + + +{749}Genus 325. _Acanthonia_,[365] Haeckel, 1881, Prodromus, p. 465. + +_Definition._--#Astrolonchida# with simple, four-edged, prismatic or +pyramidal radial spines, without apophyses; their transverse section is +square. + +The genus _Acanthonia_ comprises all those Astrolonchida (formerly united +with _Acanthometron_) in which the simple spines either in their whole +length or in the greatest part of it are four-edged, with square transverse +section. They are sometimes more prismatic (with equal breadth), at other +times more pyramidal (with decreasing breadth towards the distal apex). If +_Acanthometron_ be the common simple ancestral form of the Acanthonida, +then the two-edged _Zygacantha_, and the four-edged _Acanthonia_ may be +regarded as two divergent main lines arising from it; the former leading to +the Phractacanthida and Diporaspida, the latter leading to the +Stauracanthida and Tessaraspida. + + + +Subgenus 1. _Acanthonarium_, Haeckel. + +_Definition._--Spines at the central base, without leaf-cross and without +hollow pyramidal compartments, united by the triangular faces of their +pyramidal bases, resting one upon another. + + +1. _Acanthonia tetracopa_, Haeckel (Pl. 129, figs. 9-11). + + _Acanthometra tetracopa_, J. Mueller, 1858, Abhandl. d. k. Akad. d. Wiss. + Berlin, p. 47, Taf. vii. figs. 3 to 5, Taf. xi. fig. 5. + + _Acanthometra tetracopa_, Haeckel, 1862, Monogr. d. Radiol., p. 379, Taf. + xviii. fig. 5. + +Spines quadrangular prismatic, with prominent lamellar edges, of equal +breadth in their whole length. Base pyramidal, without leaf-cross. Apex +truncated, or with four short teeth (sometimes only two teeth). Central +capsule opaque, brown or yellow. + +_Dimensions._--Length of the spines 0.15 to 0.2, breadth 0.01 to 0.012. + +_Habitat._--Cosmopolitan; Mediterranean, Atlantic, Indian, Pacific, many +Stations, surface. + + +2. _Acanthonia prismatica_, n. sp. + +Spines quadrangular prismatic, without prominent edges, with four plane +lateral faces, of equal breadth throughout their whole length. Base +pyramidal, without leaf-cross. Apex truncate, with square apical face. + +_Dimensions._--Length of the spines 0.1 to 0.16, breadth 0.005 to 0.008. + +_Habitat._--Antarctic Ocean, Station 154, surface. + + +{750}3. _Acanthonia denticulata_, n. sp. + +Spines quadrangular prismatic, with prominent elegantly denticulated edges, +of equal breadth throughout their whole length. Both ends pyramidal, +without leaf-cross. (Similar to _Amphilonche denticulata_, but with the +twenty spines all equal, and with spherical central capsule.) + +_Dimensions._--Length of the spines 0.12 to 0.16, breadth 0.008. + +_Habitat._--Central Pacific, Stations 266 to 274, surface. + + +4. _Acanthonia muelleri_, Haeckel. + + _Acanthometra muelleri_, Haeckel, 1862, Monogr. d. Radiol., p. 379, Taf. + xv. fig. 3, Taf. xviii. fig. 6. + +Spines quadrangular, nearly prismatic, but tapering gradually from the +pyramidal base towards the distal bifid apex, which bears two thin, +parallel, or little divergent teeth; four edges elegantly denticulated; +base without leaf-cross. Central capsule yellowish or reddish. + +_Dimensions._--Length of the spines 0.12 to 0.18, basal breadth 0.005. + +_Habitat._--Mediterranean (Messina); Atlantic, Stations 348 to 352, +surface. + + +5. _Acanthonia fragilis_, Haeckel. + + _Acanthometra fragilis_, Haeckel, 1862, Monogr. d. Radiol., p. 380, Taf. + xv. fig. 4, Taf. xviii. fig. 7. + +Spines quadrangular, nearly prismatic, but gradually thickened from the +pyramidal base towards the distal truncated end; four edges regularly +denticulated; base without leaf-cross. Central capsule opaque. + +_Dimensions._--Length of the spines 0.5 and more, basal breadth 0.002 to +0.003, distal breadth 0.008 to 0.016 or more. + +_Habitat._--Mediterranean (Messina); North Atlantic, Station 354, surface. + + +6. _Acanthonia convexa_, n. sp. + +Spines quadrangular, with four broad lamellar, convex, prominent edges, +which from the broader middle part are thinned towards the two emarginated +ends; each end with a small quadrangular pyramid, without leaf-cross. All +the twenty spines of this species exhibit nearly the same form, which is +seen in the caudal or posterior (geotomical) spine of _Amphilonche anomala_ +(Monogr. d. Radiol., Taf. xviii. fig. 23, _b_). + +_Dimensions._--Length of the spines 0.12 to 0.16, breadth in the middle +part 0.02 to 0.025. + +_Habitat._--North Pacific, Station 244, surface. + + +7. _Acanthonia concava_, n. sp. + +Spines quadrangular, with four broad lamellar, concave, prominent edges, +which from the smaller middle part are broadened towards the two +emarginated ends; each end with a small {751}quadrangular pyramid, without +leaf-cross. All the twenty spines of this species exhibit nearly the same +form, which is seen in the frontal or anterior (hydrotomical) spine of +_Amphilonche anomala_ (Monogr. d. Radiol., Taf. xviii. fig. 23, _a_). + +_Dimensions._--Length of the spines 0.15, breadth in the middle part 0.012, +on both ends 0.025. + +_Habitat._--South Pacific, Station 288, surface. + + +8. _Acanthonia quadrangula_, n. sp. + +Spines quadrangular prismatic, with smooth prominent straight edges, but of +very different breadth in both halves; the inner or proximal half (inside +the central capsule) twice to four times as broad as the outer or distal +half (outside the central capsule); both ends suddenly separated by a +constriction, in which is inserted the membrane of the capsule. The latter +is pellucid, with a number of yellow bodies. Apex of the spines simple, +base pyramidal, without leaf-cross. + +_Dimensions._--Length of the spines 0.2 to 0.4, breadth of the basal half +0.01, of the distal half 0.002 to 0.004. + +_Habitat._--Atlantic, Canary Islands, Azores, Station 354, surface. + + + +Subgenus 2. _Acanthonidium_, Haeckel. + +_Definition._--Spines at the central base with a broad leaf-cross, composed +of four prominent triangular lamellae; the meeting edges of these crossed +lamellae between every three or four neighbouring spines so rest one upon +another that twenty-two hollow pyramidal compartments are formed (compare +p. 721). + + +9. _Acanthonia echinoides_, Haeckel. + + _Acanthometra echinoides_, Claparede et Lachmann, 1858, Etudes sur les + Infusoires et les Rhizopodes, &c., p. 459, pl. xxiii. figs. 1-5. + + _Acanthometra echinoides_, Haeckel, 1862, Monogr. d. Radiol., p. 383. + +Spines quadrangular prismatic without prominent edges, with four plane +lateral faces, of equal breadth throughout their whole length. Central +base three to four times as broad, with large leaf-cross. Apex truncated or +bifid (sometimes with four short teeth). + +_Dimensions._--Length of the spines 0.3 to 0.5, breadth 0.004 to 0.008; +leaf-cross 0.02 to 0.03. + +_Habitat._--North Atlantic, west coast of Norway (Claparede et Lachmann); +Faeroee Channel (Gulf Stream), John Murray, surface. + + +10. _Acanthonia claparedei_, Haeckel. + + _Acanthometra claparedei_, Haeckel, 1862, Monogr. d. Radiol., p. 383, + Taf. xviii. fig. 12. + +Spines quadrangular prismatic, with four prominent lamellar edges, of equal +breadth throughout their whole length. Apex bifid. Central base twice as +broad, with large leaf-cross. Central capsule opaque, reddish-brown. + +_Dimensions._--Length of the spines 0.6, breadth 0.016; leaf-cross 0.032. + +_Habitat._--Mediterranean (Messina); Atlantic, Station 347, surface. + + +{752}11. _Acanthonia cuspidata_, Haeckel. + + _Acanthometra cuspidata_, Haeckel, 1862, Monogr. d. Radiol., p. 383, Taf. + xviii. fig. 11. + +Spines quadrangular pyramidal, with four prominent lamellar edges, tapering +gradually from the broad base towards the simple distal apex. Basal +leaf-cross as broad, with a small central pyramid. + +_Dimensions._--Length of the spines 0.5, basal breadth 0.012; leaf-cross +0.025. + +_Habitat._--Cosmopolitan; Mediterranean, Atlantic, Pacific, surface. + + +12. _Acanthonia quadrifolia_, Haeckel. + + _Acanthometra quadrifolia_, Haeckel, 1862, Monogr. d. Radiol., p. 382, + Taf. xviii. fig. 10. + +Spines in the basal part quadrangular pyramidal, with four prominent +lamellar edges and a large basal leaf-cross; in the distal part three to +six times as long, cylindrical, of equal breadth. Apex simple, conical, or +bifid. Central capsule yellow or whitish. This common species differs from +the nearly allied _Acanthometron catervatum_ mainly by the strong +development of the large basal leaves or wings. + +_Dimensions._--Length of the spines 0.3 to 0.5, breadth in the distal half +0.002, in the basal part 0.02. + +_Habitat._--Mediterranean; North Atlantic, Stations 252 to 254; Faeroee +Channel, Gulf Stream, in enormous numbers, John Murray, surface and at +various depths. + + +13. _Acanthonia diplopyramis_, n. sp. + +Spines formed like a quadrangular double pyramid or an irregular +octahedron; the basal leaf-cross being extremely developed, with four very +large and thin lamellar leaves; the basal halves of the twenty double +pyramids are united by the meeting edges of those leaves, while their +distal halves are free, with simple apices. Therefore the four triangular +leaves of each spine are equally thinned from the middle towards the two +ends. + +_Dimensions._--Length of the spines 0.1 to 0.2, greatest breadth 0.04 to +0.08. + +_Habitat._--Central Pacific, Stations 266 to 274, surface. + + +14. _Acanthonia multispina_, Haeckel. + + _Acanthometra multispina_, J. Mueller, 1858, Abhandl. d. k. Akad. d. + Wiss. Berlin, p. 47, Taf. vii. figs. 6-9. + + _Acanthometra multispina_, Haeckel, 1862, Monogr. d. Radiol., p. 384. + +Spines quadrangular, with four lamellar prominent edges, in the proximal +half nearly prismatic, in the distal half pyramidal; both halves separated +by a prominent short tooth on each edge. Here in the middle part the +breadth (including the four teeth) is equal to the basal leaf-cross. +Central capsule opaque, brown. + +_Dimensions._--Length of the spines 0.2 to 0.3, greatest breadth 0.01 to +0.02. + +_Habitat._--Mediterranean (Messina); Tropical Atlantic, Station 348. + + +{753}15. _Acanthonia serrulata_, n. sp. + +Spines quadrangular pyramidal, with simple apex; the large basal leaf-cross +nearly half as long as the prolonged distal part. The four prominent +triangular edges of the latter are very thin and broad lamellae, finely +dentate or serrate. + +_Dimensions._--Length of the spines 0.2 to 0.3, greatest breadth 0.05 to +0.06. + +_Habitat._--Central Pacific, Station 272, surface. + + + +Subgenus 3. _Acantholithium_, Haeckel. + +_Definition._--Spines in the basal part grown together, so that the whole +skeleton is not composed of twenty separated pieces, but represents a +single piece of acanthin--a star with twenty equal rays. + + +16. _Acanthonia stellata_, n. sp. + +Spines quadrangular pyramidal, with simple distal apex, in the basal part +grown perfectly together, so that the whole skeleton forms a single piece +of acanthin--a starlet with twenty equal rays. The free pyramidal part of +each spine is twice to four times as long as the basal part. + +_Dimensions._--Length of the spines 0.1 to 0.15, greatest breadth (on the +surface of the central solid sphere) 0.02 to 0.04. + +_Habitat._--Central Pacific, Station 271, surface. + + + +Subfamily 2. PHRACTACANTHIDA, Haeckel. + +_Definition._--#Astrolonchida# with twenty radial spines, each of which +bears two opposite apophyses or lateral transverse processes; sometimes two +longitudinal rows of opposite apophyses. + + + +Genus 326. _Lithophyllium_,[366] J. Mueller, 1858, Abhandl. d. k. Akad. d. +Wiss. Berlin, p. 52. + +_Definition._--#Astrolonchida# with two simple, not branched, opposite +apophyses on each radial spine. + +The genus _Lithophyllium_ was founded by J. Mueller for a single species +(_Lithophyllium foliosum_), which we also here retain as the type of the +genus. It is the first observed Astrolonchid, which bears two opposite +lateral apophyses on each spine, and may therefore be regarded as the +ancestral form of the subfamily Phractacanthida. The two opposite apophyses +are here simple, whilst in the other genera of the subfamily they are +branched or multiplied. + + +{754}1. _Lithophyllium cruciatum_, Haeckel. + + _Acanthometra cruciata_, J. Mueller, 1858, Abhandl. d. k. Akad. d. Wiss. + Berlin, p. 49, Taf xi. fig. 11. + + _Xiphacantha cruciata_, Haeckel, 1862, Monogr. d. Radiol., p. 385, Taf. + xviii. fig. 13. + +Spines cylindrical, very thin, crossed perpendicularly in the distal third +by a thin transverse beam; both lateral rods of the cross have the same +length as the distal end. Apex simple. Base pyramidal, without leaf-cross. + +_Dimensions._--Length of the spines 0.05 to 0.15, breadth 0.001 to 0.002. + +_Habitat._--Mediterranean, Atlantic, Stations 352 to 354, &c., surface. + + +2. _Lithophyllium gladiatum_, n. sp. (Pl. 130, fig. 3). + +Spines compressed, sword-shaped, two-edged, crossed perpendicularly in the +middle part by a broad, somewhat curved transverse beam; both lateral rods +of the cross are triangular compressed, and have the same length as the +proximal end. Apex simple. Base pyramidal, without leaf-cross. + +_Dimensions_.--Length of the spines 0.2 to 0.25, breadth 0.01. + +_Habitat_.--North Pacific, Station 241, surface. + + +3. _Lithophyllium condylatum_, n. sp. + +Spines compressed quadrangular, tapering from the broader middle towards +the two ends; from the middle part arise two opposite perpendicular +apophyses, which bear on the rounded end a thickened condyle. Apex simple. +Base pyramidal, with a small leaf-cross. + +_Dimensions._--Length of the spines 0.1 to 0.12, breadth in the middle part +0.02. + +_Habitat._--Central Pacific, Station 266 to 272, surface. + + +4. _Lithophyllium foliosum_, J. Mueller. + + _Lithophyllium foliosum_, J. Mueller, 1858, Abhandl. d. k. Akad. d. Wiss. + Berlin, p. 52, Taf. xi. figs. 6-10. + + _Xiphacantha foliosa_, Haeckel, 1862, Monogr. d. Radiol., p. 385. + +Spines lanceolate, tapering from the broader middle towards the two ends. +From the middle part or from the outer third arise two opposite triangular +apophyses, which are not perpendicular to the axis of the spine, but form +an acute angle with its distal part. Therefore each spine represents a +broad leaf with a middle rib and with three lobes or truncated teeth. The +distal apex is distinguished by a violet colour. Base pyramidal, without +leaf-cross. Central capsule yellow. + +_Dimensions._--Length of the spines 0.05 to 0.1, breadth 0.02 to 0.03. + +_Habitat._--Mediterranean, French shore, Saint Tropez, J. Mueller. + + + +{755}Genus 327. _Phractacantha_,[367] Haeckel, 1881, Prodromus, p. 465. + +_Definition_.--#Astrolonchida# with two branched, but not latticed, +opposite apophyses on each radial spine. + +The genus _Phractacantha_ differs from its ancestral form, the preceding +_Lithophyllium_ by the ramification of the apophyses, which are either +forked or bear lateral branches. If the prolonged fork-branches of the +neighbouring spines meet and form a lattice-shell, this genus passes over +into _Phractaspis_, the common ancestral form of the Diporaspida. + + +1. _Phractacantha_ bifurca, n. sp. + +Spines cylindrical, thin, of equal breadth throughout their whole length. +Apex simple. Base pyramidal, without leaf-cross. From the outer third arise +two opposite, thin, forked apophyses; ends of the fork branches acute. + +_Dimensions._--Length of the spines 0.1, breadth 0.006. + +_Habitat._--Central Pacific, Station 274, surface. + + +2. _Phractacantha bipennis_, n. sp. + +Spines compressed, two-edged, tapering from the broader middle towards the +two ends. Apex simple. Base pyramidal, without leaf-cross. From the middle +arise two opposite broad, forked apophyses; ends of the fork-branches broad +and obtuse. + +_Dimensions._--Length of the spines 0.15, breadth in the middle 0.012. + +_Habitat._--Central Pacific, Station 266, surface. + + + +Genus 328. _Doracantha_,[368] Haeckel, 1881, Prodromus, p. 465. + +_Definition_.--#Astrolonchida# with two latticed or fenestrated apophyses +on each radial spine. + +The genus _Doracantha_ arises from the foregoing _Phractacantha_ by union +of the fork-branches of the apophyses on each spine. By this concrescence +is formed a polygonal or roundish plate with two pores, pierced by the +radial spine between them. _Doracantha_ may be regarded as a _Dorataspis_, +in which the twenty small fenestrated plates have not become united. + + +{756}1. _Doracantha dorataspis_, n. sp. + +Spines compressed, two-edged, tapering from the broader middle towards the +two ends. Apex simple. Base pyramidal, without leaf-cross. From the middle +part of each spine arise two opposite forked apophyses; the neighbouring +fork-branches are recurved and united in the tangential plane; so that each +spine bears a plate or shield with two elliptical pores; the margin of the +roundish plate bears a variable number of short teeth. + +_Dimensions._--Length of the spines 0.2, breadth 0.02. + +_Habitat._--Central Pacific, Station 271, surface. + + + +Genus 329. _Astrolonche_,[369] Haeckel, 1881, Prodromus, p. 465. + +_Definition._--#Astrolonchida# with numerous simple apophyses (four to +eight or more on each radial spine), which are arranged in two opposite +longitudinal rows (rarely in six such rows, opposite in three parallel +planes). + +The genus _Astrolonche_ differs from the preceding Phractacanthida in the +multiplication of the simple apophyses. Commonly these are opposite in +pairs in two longitudinal rows (on the two edges of the compressed spine, +at least two on each side). But sometimes (in the subgenus +_Astrolonchidium_) there are six instead of two longitudinal rows of teeth, +and these are placed in three parallel planes. + + + +Subgenus 1. _Astroloncharium_, Haeckel. + +_Definition._--Each spine with two longitudinal rows of apophyses, opposite +in one meridian plane. + + +1. _Astrolonche bicruciata_, n. sp. + +Spines compressed, two-edged, almost of equal breadth throughout their +whole length, with simple apex and small leaf-cross at the base. From the +two edges of the middle part of each spine arise two pairs of opposite +apophyses, which are compressed and a little curved (convex on the distal, +concave on the proximal margin). All four apophyses are of the same size +and form; the radial distance of each pair much smaller than their common +distance from the centre. + +_Dimensions._--Length of the spines 0.25, breadth 0.02. + +_Habitat._--Central Pacific, Station 270, surface. + + +2. _Astrolonche mucronata_, Haeckel. + + _Acanthometra mucronata_, J. Mueller, 1858, Abhandl. d. k. Akad. d. Wiss. + Berlin, p. 49, Taf. x. fig. 9. + + _Aspidomma mucronatum_, Haeckel, 1862, Monogr. d. Radiol., p. 424. + +Spines conical, little compressed, with simple apex and small leaf-cross at +the base. From the basal half of each spine arise two pairs of opposite +apophyses, which exhibit a very different form. {757}The upper or distal +apophyses (nearly in the middle of the spine) are flat, leaf-shaped, +broadened in the periphery, often lobed, and sometimes branched or even +fenestrated. (Transition to _Phractaspis_ and _Dorataspis_, or to +_Phractopelta_?) The lower or proximal apophyses are thick, simple, all +slightly curved; they are equidistant from the former and from the centre. + +_Dimensions._--Length of the spines 0.2 to 0.3, greatest breadth 0.01. + +_Habitat._--Mediterranean (Cette on the French shore), surface, J. Mueller. + + +3. _Astrolonche pectinata_, Haeckel. + + _Acanthometra pectinata_, J. Mueller, 1858, Abhandl. d. k. Akad. d. Wiss. + Berlin, p. 48, Taf. x. figs. 1, 2. + + _Xiphacantha pectinata_, Haeckel, 1862, Monogr. d. Radiol., p. 386. + +Spines compressed quadrangular, with short, simple or bifid apex, pyramidal +on the base, without leaf-cross. From the two broader edges of the proximal +half arise two longitudinal rows of opposite apophyses; three to four +slender teeth in each row. + +_Dimensions._--Length of the spines 0.2, breadth 0.08. + +_Habitat._--Mediterranean, Cette (French shore), surface, J. Mueller. + + +4. _Astrolonche pinnata_, n. sp. + +Spines in the distal half compressed, linear, two-edged, with bifid apex; +in the proximal half three times as broad lanceolate, at the base +pyramidal, without leaf-cross. From the two broader edges of the proximal +half arise two longitudinal rows of opposite apophyses; four to six broad +triangular teeth in each row. + +_Dimensions._--Length of the spines 0.3 to 0.4, breadth in the outer half +0.012, in the inner half 0.03 to 0.04. + +_Habitat._--South Atlantic, Station 332, surface. + + + +Subgenus 2. _Astrolonchidium_, Haeckel. + +_Definition._--Each spine with three parallel double rows of opposite +apophyses. + + +5. _Astrolonche serrata_, Haeckel. + + _Xiphacantha serrata_, Haeckel, 1862, Monogr. d. Radiol., p. 386, Taf. + xvii. fig. 3, Taf. xviii. figs. 14_a_, 14_b_. + + _Xiphacantha serrata_, R. Hertwig, 1879, Organismus d. Radiol., p. 11, + Taf. ii. fig. 4. + + _Acanthometra serrata_, Haeckel, 1860, Monogr. d. Radiol., p. 807. + +Spines in the distal half thin, nearly cylindrical or a little compressed, +thinned towards the short simple or bifid apex; in the proximal half three +to six times as broad, four-winged, with six longitudinal rows of opposite +apophyses. From the edges of the two broader (lateral) wings arise three +{758}to four pairs of strong conical teeth; from the edges of the two +smaller (sagittal) wings arise also three to four pairs of teeth, but very +short and broad, triangular; each of these teeth bears on both its +(lateral) sides two opposite slender conical teeth, which are parallel to +the large conical teeth of the lateral wings. Therefore all teeth (eighteen +to twenty-four) are placed opposite in pairs in three parallel planes. Base +of the spines pyramidal, with a small leaf-cross. The central capsule of +this large and very remarkable species commonly entirely includes the +apophyses of the spines, and is opaque, whitish. + +_Dimensions._--Length of the spines 0.2 to 0.3, breadth of the distal half +0.002 to 0.004, of the proximal half 0.01 to 0.02. + +_Habitat._--Cosmopolitan; Mediterranean, Atlantic, Pacific, surface. + + + +Subfamily 3. STAURACANTHIDA, Haeckel. + +_Definition._--#Astrolonchida# with a cross of four free apophyses (or four +crossed longitudinal rows of apophyses) on each radial spine. + + + +Genus 330. _Xiphacantha_,[370] Haeckel, 1862, Monogr. d. Radiol., p. 384. + +_Definition._--#Astrolonchida# with four simple apophyses on each radial +spine, opposite in pairs in the form of a cross. + +The genus _Xiphacantha_ was founded by me in 1862 for all those +_Acanthometrida_ which bear simple or branched apophyses on their twenty +equal spines. I restrict here the genus to those Astrolonchida which bear +on each spine a cross of four simple, not branched, apophyses. These are +either conical teeth or broad wings, sometimes extremely thin leaves. +_Xiphacantha_ may be regarded as the ancestral form not only of the +subfamily Stauracanthida, but also of the Tessaraspida, derived from the +latter. + + + +Subgenus 1. _Xiphacanthonia_, Haeckel. + +_Definition._--Apophyses of the radial spines small, formed like a tooth or +a hook, not wing-shaped. Edges of the spines commonly narrow, little +prominent. + + +1. _Xiphacantha quadridentata_, Haeckel. + + _Xiphacantha quadridentata_, Haeckel, 1862, Monogr. d. Radiol., p. 387, + Taf. xviii. figs. 15_a_, 15_b_. + + _Acanthometra quadridentata_, J. Mueller, 1858, Abhandl. d. k. Akad. d. + Wiss. Berlin, p. 48, Taf. x. fig. 3. + +Spines slender, four-sided prismatic, gradually thinner towards the simple +pyramidal apex. Base with large wing-cross. Four apophyses about in the +middle of each spine, conical, straight, smooth, about as long as the basal +breadth of the spine. Central capsule opaque, reddish-brown. + +{759}_Dimensions._--Length of the spines 0.2 to 0.3, breadth in the middle +part 0.012, on the base 0.02; length of the apophyses 0.02 to 0.03. + +_Habitat._--Mediterranean, Atlantic, Stations 348, 354, surface. + + +2. _Xiphacantha crucifera_, n. sp. + +Spines slender, four-sided prismatic, thin, of nearly equal breadth +throughout the whole length. Base with small wing-cross. Four apophyses +much nearer the proximal than the distal end, thin, straight smooth, three +to six times as long as the basal breadth of the spine. Central capsule +pellucid, with yellow bodies. + +_Dimensions._--Length of the spines 0.4 to 0.5, breadth 0.002 to 0.004; +length of the apophyses 0.01 to 0.02. + +_Habitat._--Central Pacific, Station 266, surface. + + +3. _Xiphacantha spinulosa_, Haeckel. + + _Xiphacantha spinulosa_, Haeckel, 1862, Monogr. d. Radiol., p. 388, Taf. + xvii. fig. 4. + + _Acanthometra spinulosa_, Haeckel, 1860, Monatsber. d. k. preuss. Akad. + d. Wiss. Berlin, p. 807. + +Spines stout, four-sided prismatic, of nearly equal breadth throughout the +whole length, on the distal apex truncated, two-edged. Base with large +wing-cross. Four apophyses about in the middle of each spine, conical, +straight, spinulated, twice to four times as long as the basal breadth of +the spine. Central capsule opaque, yellow. + +_Dimensions._--Length of the spines 0.27, breadth 0.014; length of the +apophyses 0.05. + +_Habitat._--Mediterranean (Messina), surface. + + +4. _Xiphacantha emarginata_, n. sp. + +Spines stout, four-sided, in the proximal half prismatic, in the distal +half pyramidal, with emarginated apex. Base with very large wing-cross. +Four apophyses about in the middle of each spine, compressed, straight, +two-edged, with emarginated ends, about twice as long as the basal breadth +of the spine. Central capsule small, pellucid. + +_Dimensions._--Length of the spines 0.2 to 0.3, breadth 0.02 to 0.03; +length of the apophyses 0.04 to 0.06. + +_Habitat._--South Pacific, Station 291, surface. + + +5. _Xiphacantha falcata_, n. sp. + +Spines slender, four-sided prismatic, gradually thickened from both ends +towards the middle part, with simple apex. Base with very small wing-cross. +Four apophyses about in the middle part of each spine, falcated, +compressed, recurved, twice to three times as long as the greatest breadth +of the spine. + +{760}_Dimensions._--Length of the spines 0.3 to 0.4, greatest breadth +0.015; length of the apophyses 0.03 to 0.05. + +_Habitat._--Central Pacific, Station 270, surface. + + +6. _Xiphacantha ancorata_, n. sp. + +Spines slender, four-sided prismatic, gradually thickened from the narrow +base towards the short, simple, pyramidal apex. Base with large wing-cross. +Four apophyses on the distal end, immediately below the pyramidal apex, +falcated, strongly recurved, like an anchor with four strong teeth. + +_Dimensions._--Length of the spines 0.4 to 0.5, basal breadth 0.005, distal +breadth 0.015; length of the apophyses 0.04. + +_Habitat._--Indian Ocean, Madagascar, Rabbe. + + + +Subgenus 2. _Xiphacanthidium_, Haeckel. + +_Definition._--Apophyses of the radial spines broad, compressed, +wing-shaped, formed like a large thin plate. Edges of the spines commonly +broad, strongly prominent. + + +7. _Xiphacantha stauroptera_, n. sp. + +Spines four-winged, from the middle part little thinner towards both ends. +Apex simple pyramidal. Base with small wing-cross. Four apophyses +wing-shaped, isosceles triangular or truncated quadrangular; their base is +about half as broad as their length, and occupies in the basal half of each +spine about one-sixth to one-eighth of its length. + +_Dimensions._--Length of the spines 0.1 to 0.15; greatest breadth (diagonal +of the cross of the apophyses) 0.006 to 0.009. + +_Habitat._--South Atlantic, Station 332, surface. + + +8. _Xiphacantha trigonoptera_, n. sp. + +Spines four-winged, tapering rapidly from the broad middle part towards +both ends. Apex simple pyramidal. Base with a small wing-cross. Four +apophyses equilateral triangular; their base occupies the middle of each +spine, extending to about one-fifth of its length. + +_Dimensions._--Length of the spines 0.15 to 0.2, greatest breadth (diagonal +of the cross of the apophyses) 0.06 to 0.08. + +_Habitat._--Central Pacific, Station 272, surface. + + +9. _Xiphacantha macroptera_, n. sp. + +Spines four-winged, from the broad middle part gradually thinner towards +both ends. Apex simple pyramidal. Base with small wing-cross. Four +apophyses wing-shaped, very long and broad, {761}triangular; their base +occupies about the middle third of each spine; the proximal side of each +wing is the shortest, truncated or concave. + +_Dimensions._--Length of the spines 0.4 to 0.5, greatest breadth (diagonal +of the middle leaf-cross) 0.08 to 0.12. + +_Habitat._--North Pacific, Stations 253 to 256, surface. + + +10. _Xiphacantha platyptera_, n. sp. + +Spines four-winged, nearly prismatic in the basal and distal parts. Apex +truncated. Base with small wing-cross. Four apophyses wing-shaped, very +broad and thin, extremely delicate, of irregular quadrangular or nearly +rhomboidal form; their base occupies the middle half of the length of the +spines (second and third quarter). Very variable in form. Often the edges +of the wing-apophyses of the neighbouring spines seem to meet. + +_Dimensions._--Length of the spines 0.2 to 0.3, greatest breadth (diagonal +of the leaf-cross) 0.06 to 0.08. + +_Habitat._--Pacific, widely distributed, Stations 239, 253, 272, 288, &c., +surface. + + +11. _Xiphacantha ciliata_, n. sp. (Pl. 129, figs. 4, 5). + +Spines four-winged, prismatic in the basal and the distal third. Apex +pyramidal, short. Base with large leaf-cross. Four apophyses wing-shaped, +nearly semicircular, with dentated edges and rough spinulate or porous +faces; their base occupies the middle third of the length of each spine. + +_Dimensions._--Length of the spines 0.2 to 0.3, greatest breadth (diagonal +of the apophysial cross) 0.08 to 0.12. + +_Habitat._--Tropical Atlantic, Stations 342 to 352, surface. + + +12. _Xiphacantha alata_, Haeckel. + + _Xiphacantha alata_, Haeckel, 1862, Monogr. d. Radiol., p. 388. + + _Acanthometra alata_, J. Mueller, 1858, Abhandl. d. k. Akad. d. Wiss. + Berlin, p. 48, Taf. ix. figs. 1-3. + +Spines four-winged, prismatic in the basal quarter, more slender in the +distal half. Apex simple pyramidal. Base with small wing-cross. Four +apophyses wing-shaped, nearly semicircular, with denticulated edges (and +often also with spinulate faces); their base occupies the second quarter of +the length of each spine. + +_Dimensions._--Length of the spines 0.3 to 0.4, greatest breadth (diagonal +of the apophysial cross) 0.05 to 0.06. + +_Habitat._--Mediterranean (Nice), Mueller, (Portofino), Haeckel. + + + +Genus 331. _Stauracantha_,[371] Haeckel, 1881, Prodromus, p. 465. + +_Definition._--#Astrolonchida# with four branched (but not latticed) +apophyses on each radial spine, opposite in pairs in the form of a cross. + +{762}The genus _Stauracantha_ differs from its ancestral form, +_Xiphacantha_, in the ramification of the four crossed apophyses on each +spine. These bear either lateral branches, which are parallel to the cross +axes of the radial spine itself (subgenus _Stauracanthonium_), or they are +forked, with divergent branches not parallel to those cross axes (subgenus +_Stauracanthidium_). Both subgenera may perhaps be better separated as +genera. They form the transition to the _Stauraspida_. + + + +Subgenus 1. _Stauracanthonium_, Haeckel. + +_Definition._--Apophyses of the radial spines not forked, but crossed by +perpendicular branches, which are placed in tangential planes and parallel +to the cross axes of the quadrangular spine itself. + + +1. _Stauracantha orthostaura_, n. sp. (Pl. 130, fig. 5). + +Spines four-sided prismatic, with simple apex and small leaf-cross at the +base; with four thin slender conical apophyses in the proximal third. Each +apophysis represents a regular rectangular cross, being intersected in its +middle by one perpendicular rod of its own length. + +_Dimensions._--Length of the spines 0.3, breadth 0.02; distance of the +apophyses from the apex 0.15 to 0.2. + +_Habitat._--South Pacific, Station 169, surface. + + +2. _Stauracantha tetrastaura_, n. sp. + +Spine four-winged prismatic, with four broad prominent edges, pyramidal +apex, and large basal leaf-cross, with four broad compressed apophyses +about in the middle. Each apophysis represents a vertical lamella (placed +in a meridian) with convex distal and concave proximal edge, and is crossed +in its apical part by one perpendicular short rod. + +_Dimensions._--Length of the spines 0.5, breadth 0.03; distance of the +apophyses from the centre 0.2. + +_Habitat._--Central Pacific, Station 272, surface. + + +3. _Stauracantha diplostaura_, n. sp. + +Spines four-sided prismatic, with truncated apex and broad basal +leaf-cross; in the proximal half with four slender conical apophyses. Each +apophysis is crossed in its apical half at right angles by two short +parallel transverse rods. + +_Dimensions._--Length of the spines 0.32, breadth 0.012; distance of the +apophyses from the centre 0.11. + +_Habitat._--South Pacific, Station 291, surface. + + +{763}4. _Stauracantha scalaris_, n. sp. + +Spines four-winged prismatic, with four broad prominent edges, truncated +apex, and small basal leaf-cross; in the proximal third with four +compressed lamellar apophyses. Each apophysis is pinnate with opposite +pinnulae, or crossed at right angles by three to six parallel transverse +rods. + +_Dimensions._--Length of the spines 0.24, breadth 0.016; central distance +of the apophyses 0.12. + +_Habitat._--Indian Ocean (Madagascar), Rabbe, surface. + + +5. _Stauracantha johannis_, n. sp. (Pl. 132, fig. 11). + +Spines four-sided pyramidal, with simple apex and broad basal leaf-cross, +with four large conical apophyses about in their middle. Each apophysis +bears two irregular rows of alternating perpendicular lateral branches, the +length of which decreases from the base towards the apex of the apophysis. + +_Dimensions._--Length of the spines 0.2, middle breadth 0.02; central +distance of the apophyses 0.1. + +_Habitat._--South-east Pacific (off Juan Fernandez), Station 300, surface. + + +6. _Stauracantha murrayana_, Haeckel. + + _Xiphacantha species_, Wyville Thomson, 1877, The Atlantic, vol. i. p. + 235, fig. 53. + + _Xiphacantha murrayana_, Haeckel, 1878, Protistenreich, p. 45, fig. 33. + +Spines quadrangular prismatic, with pyramidal apex and small basal +leaf-cross, with four regular conical apophyses in the proximal part. Each +apophysis is crossed at right angles by two parallel transverse rods; the +smaller apical rod is simple; the larger basal rod is crossed again on each +side by a secondary perpendicular branch, which therefore is parallel to +the apophysis itself. + +_Dimensions._--Length of the spines 0.3, breadth 0.01, distance of the +apophyses 0.08. + +_Habitat._--South Atlantic, Station 332, surface. + + +7. _Stauracantha pinnulata_, n. sp. + +Spines four-winged pyramidal, with prominent edges, simple apex and large +basal leaf-cross, in the middle with doubly pinnate triangular apophyses. +Each apophysis is crossed at right angles by three to four transverse +parallel rods, which bear again perpendicular secondary branches; the +outline of the doubly pinnate apophysis is an isosceles triangle. + +_Dimensions._--Length of the spines 0.3, middle breadth 0.02; distance of +the apophyses 0.12. + +_Habitat._--North Pacific, Station 244, surface. + + + +{764}Subgenus 2. _Stauracanthidium_, Haeckel. + +_Definition._--Apophyses of the radial spines forked, each with two +divergent terminal branches, which are not parallel to the cross axes of +the quadrangular spine. + + +8. _Stauracantha stauraspis_, Haeckel. + + _Dorataspis polyancistra, juvenis_, Haeckel, 1862, Monogr. d. Radiol., p. + 418, Taf. xxi. fig. 7. + +Spines slender, quadrangular prismatic, with simple apex and pyramidal base +(without basal leaf-cross); with four slender apophyses, which are simply +forked in the outer third. Each apophysis with two recurved fork branches. + +_Dimensions._--Length of the spines 0.12, breadth 0.004; distance of the +apophyses 0.06. + +_Habitat._--Mediterranean (Messina), surface. + + +9. _Stauracantha bifurca_, n. sp. + +Spines stout, four-winged prismatic, with pyramidal apex and pyramidal base +(without leaf-cross); in their middle with four compressed, little curved +apophyses (convex on the outer, concave on the inner edge), which are +simply forked at the end. Each apophysis with two short straight fork +branches. + +_Dimensions._--Length of the spines 0.2, breadth 0.006; distance of the +apophyses 0.08. + +_Habitat._--Central Pacific, Station 266, surface. + + +10. _Stauracantha quadrifurca_, n. sp. (Pl. 130, fig. 4). + +Spines slender, four-sided prismatic, with simple apex and pyramidal base +(without leaf-cross); with four slender apophyses, which are doubly forked +about in their middle. Each apophysis with four short and thin terminal +branches. + +_Dimensions._--Length of the spines 0.2, breadth 0.002; distance of the +apophyses from the centre 0.08. + +_Habitat._--South Atlantic, Stations 325 to 330, surface. + + + +Genus 332. _Phatnacantha_,[372] Haeckel, 1881, Prodromus, p. 465. + +_Definition._--#Astrolonchida# with four apophyses on each radial spine, +opposite in pairs in cross form, and forming a lattice-plate by +communicating branches. + +The genus _Phatnacantha_ has been derived from the preceding _Stauracantha_ +by concrescence of the branches of the apophyses. Therefore each spine +bears a lattice-plate or a fenestrated shield. If the growing plates of the +neighbouring spines {765}meet together, then the characteristic +lattice-shell of the Tessaraspida is perfect. Either each plate bears four +crossed pores (like _Tessaraspis_), or a larger number of pores (four +aspinal and four to eight or more coronal) like _Icosaspis_. + + +1. _Phatnacantha tessaraspis_, n. sp. + +Spines quadrangular prismatic, with simple pyramidal apex and small basal +leaf-cross. Each spine bears in the basal half a square plate, which is +perforated by four square pores; margin of the plate with twelve short +straight teeth. + +_Dimensions._--Length of the spines 0.12, breadth 0.005. + +_Habitat._--Central Pacific, Station 265, surface. + + +2. _Phatnacantha icosaspis_, n. sp. (Pl. 130, fig. 6). + +Spines quadrangular with prominent edges; prismatic in the basal half, with +a broad basal leaf-cross, pyramidal in the distal half, with a simple or +truncate apex. Each spine bears in the middle part a square plate, which is +perforated by eight to sixteen or more square pores (four aspinal and four +to eight or more coronal); margin of the plate with twenty-four to +forty-eight or more short straight irregular compressed teeth. + +_Dimensions._--Length of the spines 0.18, breadth 0.008. + +_Habitat._--Central Pacific, Station 273, surface. + + + +Genus 333. _Pristacantha_,[373] n. gen. + +_Definition._--#Astrolonchida# with numerous simple apophyses (eight to +sixteen or more on each radial spine) which are arranged in four +longitudinal rows opposite in pairs in the form of a cross. + +The genus _Pristacantha_ differs from all other Stauracanthida in the +multiplication of the crossed apophyses (at least eight on each spine), and +exhibits therefore to them the same relation as _Astrolonche_ exhibits to +the other Phractacanthida. The remarkable _Astrolonchidium serratum_ +appears intermediate between both groups. + + +1. _Pristacantha octodon_, n. sp. (Pl. 130, fig. 9). + +Spines four-sided prismatic, a little broader in the middle part than at +either end, with thin prominent edges. Apex truncate or pyramidal. Base +pyramidal, with a small leaf-cross. From the four edges arise in the basal +half (between first and second third of the length) eight slender, conical, +or triangular apophyses (two on each edge). + +_Dimensions._--Length of the spines 0.4 to 0.6, breadth 0.02 to 0.04. + +_Habitat._--Central Pacific, Station 271, surface. + + +{766}2. _Pristacantha dodecodon_, n. sp. (Pl. 130, fig. 8). + +Spines four-winged, of lanceolate outline, tapering from the broader middle +towards the two ends. Apex pyramidal. Base with a large leaf-cross. From +the four wings arise in the basal part (between first and second third of +the length) twelve triangular apophyses (three from each wing). + +_Dimensions._--Length of the spines 0.3, breadth in the middle 0.03. + +_Habitat._--North Pacific, Station 244, surface. + + +3. _Pristacantha polyodon_, n. sp. (Pl. 130, fig. 7). + +Spines in the distal half four-sided prismatic, thin, with pyramidal apex; +in the basal half much broader, four-winged, with a large leaf-cross on the +base. From the four wings of the basal half arises a variable number of +slender teeth or triangular apophyses, commonly sixteen to twenty-four, +often irregular (four to six from each wing). + +_Dimensions._--Length of the spines 0.3 to 0.4, breadth in the distal part +0.007 to 0.01, in the basal part 0.02 to 0.03. + +_Habitat._--South Pacific (off New Zealand), Station 169, surface. + + + +Family XXXVII. #QUADRILONCHIDA#, Haeckel (Pl. 131). + +_Acanthostaurida_, Haeckel, 1881, Prodromus, p. 466. + +_Definition._--ACANTHARIA with twenty radial spines of very unequal size, +disposed according to the law of the Icosacantha; four equatorial spines +much larger than the sixteen others. No lattice-shell. + +The family #Quadrilonchida# differs from the foregoing ancestral family, +the Astrolonchida, in the unequal development of the twenty radial spines. +The four equatorial spines are constantly much larger, and often also of +another form and shape, than the sixteen other spines; often also among +these the eight tropical spines are larger and of another form than the +eight polar spines. Therefore the five parallel girdles or zones of every +four spines, which in the Astrolonchida are equal, are here distinctly +unequal. The whole body is flattened and compressed in the direction of the +spineless axis, so that the equatorial plane is larger than any other +plane, laid through the centre. In consequence of this flattening the +central capsule is also commonly compressed and flattened, lenticular or +discoidal, rarely spherical. In the Astrolonchida the "promorph" or the +"geometrical fundamental form" is constantly a square double pyramid, the +axes of which are of equal length. In the Quadrilonchida it becomes a +square double pyramid, the two equatorial axes of which (or the diagonals +of the square) are constantly longer than all other axes. + +In the simpler forms of Quadrilonchida are found only two different kinds +of spines, the four larger equatorial spines being of the same size and +form, and the sixteen smaller {767}spines also not differing from one +another (_Acanthostaurus_, &c.). But in the majority of this family there +are three different kinds: four larger equatorial spines, eight tropical +spines of middle size, and eight smaller polar spines (_Belonostaurus_, +&c.); the latter become sometimes rudimentary, so that only twelve spines +are developed (four larger equatorial and eight smaller tropical spines). +In this case the development of the flat discoidal body is much stronger in +the equatorial plane than in all other planes. These discoidal or +lenticular Quadrilonchida exhibit a relation to the spherical Astrolonchida +similar to that which the #Discoidea# exhibit to the #Sphaeroidea# among +the #Sphaerellaria#. + +A further morphological differentation takes place in the remarkable genera +_Lonchostaurus_ and _Zygostaurus_. In the former (Pl. 131, figs. 4-6) the +four larger equatorial spines becomes differentiated in pairs, so that the +opposite equal spines of one pair, _c_1, _c_3 (in the longitudinal or +hydrotomical axis), are larger, and often also of another form, than the +opposite equal spines of the other pair, _c_2, _c_4 (in the transverse or +geotomical axis). The most peculiar form is the rather common _Zygostaurus_ +(Pl. 131, figs. 7, 8). Here the two opposite spines of one equatorial axis +(of the longitudinal axis) become very different, so that the anterior or +frontal spine (_c_1) is very unequal to the posterior or caudal spine +(_c_3), whereas the two opposite spines, of the other equatorial axis (of +the transverse axis) remain equal (_c_2, _c_4). Therefore the fundamental +forms become here "amphithect," as in the Ctenophora. + +The numerous Quadrilonchida may be disposed in two different subfamilies: +in the Acanthostaurida all twenty radial spines are simple, without +apophyses; in the Lithopterida all twenty spines (or only one part of +them) bear two opposite apophyses (or lateral transverse processes). The +former correspond to the Zygacanthida, the latter to the Phractacanthida +among the Astrolonchida. The two opposite apophyses are simple in +_Quadrilonche_ (Pl. 133, fig. 1). In _Xiphoptera_ they are provided on +their distal side with lateral branches which are parallel to the spine +itself. In _Lithoptera_ the spines bear two to four parallel pairs of +transverse apophyses, and these are crossed by perpendicular branches, +parallel to the spine itself, so that there arise fenestrated wings or +latticed plates, comparable to the sails of a wind-mill. The lattice-work +of these plates lies in the same meridian plane with the radial spine +itself, and is therefore not comparable to the fenestrated apophyses of +_Doracantha_, of _Phatnacantha_, and of the Dorataspida; in these the +lattice-plates lie in tangential planes, perpendicular to the radial spine. + +The apophyses of the Lithopterida may be developed either on all twenty +spines equally, or only on twelve spines (four equatorial and eight +tropical, whilst the eight polar spines are simple, Pl. 131, fig. 10), or +only on the four equatorial spines (whilst the sixteen others are simple, +Pl. 131, fig. 9). + +_The Central Capsule_ of the Quadrilonchida is rarely spherical, commonly +more or {768}less compressed from both poles of the spineless axis, +lenticular or discoidal, sometimes square. It is enveloped by a voluminous +calymma constantly bearing coronals of "Myophrisca" (compare p. 724). + +_Synopsis of the Genera of Quadrilonchida._ + + ------------------------------------------------------------------------- + I. Subfamily Acanthostaurida. + All twenty spines simple, without lateral apophyses (sometimes forked, + but neither branched nor latticed). + ------------------------------------------------------------------------- + { Eight tropical and + { eight polar spines + { nearly equal, 334. _Acanthostaurus_. + Four equatorial spines of { + equal size and form. { Eight tropical and + { eight polar spines + { very different, 335. _Belonostaurus_. + + { Two principal spines + Four equatorial spines of { of equal size and + very different size or { form, 336. _Lonchostaurus_. + form (the two lateral { + constantly equal). { Two principal spines + { (frontal and caudal) + { very different, 337. _Zyostaurus_. + ------------------------------------------------------------------------- + II. Subfamily Lithopterida. + Either all twenty spines or a part of them provided with two opposite + lateral branches or apophyses. + ------------------------------------------------------------------------- + Apophyses simple, neither branched nor latticed, 338. _Quadrilonche_. + + Apophyses branched or pinnate, but not latticed, 339. _Xiphoptera_. + + Apophyses latticed, with fenestrated network, 340. _Lithoptera_. + + + +Subfamily 1. ACASTHOSTAURIDA, Haeckel, 1881, Prodromus, p. 466. + +_Definition._--#Quadrilonchida# with simple radial spines, without +apophyses. + + + +Genus 334. _Acanthostaurus_,[374] Haeckel, 1862, Monogr. d. Radiol., p. +395. + +_Definition._--#Quadrilonchida# with four equatorial spines of equal size +and form, which are much larger than the sixteen other spines. Eight +tropical and eight polar spines nearly equal. No apophyses. + +The genus _Acanthostaurus_ is the most simple and primitive form of the +Quadrilonchida, and the common ancestral genus of this family; it is at the +same time its most common and widely distributed form. Some species appear +in astonishing numbers in different seas. It has been derived from +_Acanthometron_ by stronger development of the four equatorial spines, +which are all of equal size and much larger than the sixteen others. + + + +{769}Subgenus 1. _Acostaurus_, Haeckel. + +_Definition._--All twenty spines separated, in the centre united only by +the triangular faces or the meeting leaf-shaped edges of their pyramidal +bases. + + +1. _Acanthostaurus aequatorialis_, n. sp. + +Spines cylindrical, of nearly equal breadth throughout their whole length. +Apex simple conical. Base with a large leaf-cross. Four equatorial spines +of the same form as the sixteen others, but much longer and about three +times as broad. + +_Dimensions._--Length of the four major spines 0.2 to 0.25, breadth 0.008; +length of the sixteen minor spines 0.01 to 0.15, breadth 0.003. + +_Habitat._--Equatorial Pacific, Station 271, surface. + + +2. _Acanthostaurus bipennis_, n. sp. + +Spines linear, sword-shaped, strongly compressed, two edged; of nearly +equal breadth in their whole length. Apex bifid. Base with a small +leaf-cross. Four equatorial spines of the same form as the sixteen others, +but twice as long and as broad. + +_Dimensions._--Length of the four major spines 0.4 to 0.5, of the sixteen +minor 0.2 to 0.3; breadth of the former 0.02, of the latter 0.01. + +_Habitat._--North Pacific, Station 244, surface. + + +3. _Acanthostaurus conacanthus_, n. sp. + +Spines conical, short, gradually tapering from the thick base towards the +simple apex. Base with large leaf-cross. Four equatorial spines more +cylindrical, twice to three times as long and as broad as the sixteen +others. + +_Dimensions._--Length of the four major spines 0.15 to 0.2, of the sixteen +minor 0.05 to 0.08; basal breadth of the former 0.03, of the latter 0.012. + +_Habitat._--South Atlantic, Station 332, surface. + + +4. _Acanthostaurus purpurascens_, Haeckel. + + _Acanthostaurus purpurascens_, Haeckel, 1862, Monogr. d. Radiol., p. 395, + Taf. xix. figs. 1, 2. + + _Acanthostaurus purpurascens_, R. Hertwig, 1879, Organism. d. Radiol., + Taf. i. figs. 8, 9, Taf. iii. figs. 13, 15. + + _Acanthometra purpurascens_, Haeckel, 1860, Monatsber. d. k. preuss. + Akad. d. Wiss. Berlin, p. 809. + +Spines nearly cylindrical, with four blunt (often scarcely visible) edges, +tapering slightly from the central to the distal end. Apex bifid, with two +short parallel teeth. Base with a broad leaf-cross. {770}Four equatorial +spines one and a half times to twice as long and broad as the sixteen +others. Central capsule cruciate, with four arms (enveloping the basal part +of the four large spines); filled up with yellow bodies and purple +granules. Calymma large, with a network of purple granules. The four main +spines are constantly much larger than the sixteen others, but in variable +proportion. The eight polar spines are sometimes rudimentary. + +_Dimensions._--Length of the four major spines 0.3 to 0.4, of the sixteen +minor 0.15 to 0.3; breadth of the former 0.012, of the later 0.008 or less. + +_Habitat._--Mediterranean (Messina); Atlantic, Stations 348 to 354, +surface. + + +5. _Acanthostaurus pallidus_, Haeckel. + + _Acanthostaurus pallidus_, Haeckel, 1862, Monogr. d. Radiol., p. 396. + + _Acanthometra pallida_, Claparede et Lachmann, 1858, Etudes sur les + Infusoires, &c., p. 461, Taf. xxiv. fig. 6. + +Spines four-sided prismatic, with four blunt edges, of nearly equal breadth +throughout their whole length. Apex bifid. Base with a small leaf-cross. +Four equatorial spines much larger than the sixteen others. Central capsule +spherical, transparent, containing some yellow bodies. + +_Dimensions._--Length of the four main spines 0.12 to 0.2, of the sixteen +others 0.04 to 0.08; breadth of the former 0.01, of the latter 0.004. + +_Habitat._--North Atlantic, west coast of Norway, Claparede; Faeroee +Channel, John Murray. + + +6. _Acanthostaurus forceps_, Haeckel. + + _Acanthostaurus forceps_, Haeckel, 1862, Monogr. d. Radiol., p. 396, Taf. + xix. figs. 3, 4. + + _Acanthometra forceps_, Haeckel, 1860, Monatsber. d. k. preuss. Akad. d. + Wiss. Berlin, p. 809. + +Spines pincer-shaped, linear, compressed, cleft nearly throughout their +whole length into two parallel thin, straight branches, which are united +only at the pyramidal base and by means of a small bridge in the middle +part. Four main spines twice as long and as broad as the sixteen others. +Central capsule square, filled up with red pigment, and containing yellow +bodies. The diagonals of the square are the two equatorial axes. + +_Dimensions._--Length of the four main spines 0.1, of the sixteen others +0.05; breadth of the former 0.01, of the latter 0.005. + +_Habitat._--Mediterranean (Messina); North Atlantic, Canary Islands, +Station 354, surface. + + +7. _Acanthostaurus hastatus_, Haeckel. + + _Acanthostaurus hastatus_, Haeckel, 1862, Monogr. d. Radiol., p. 397, + Taf. xix. fig. 5. + + _Acanthometra hastata_, Haeckel, 1860, Monatsber. d. k. preuss. Akad. d. + Wiss. Berlin, p. 809. + +Spines of very different size and form; four equatorial spines cylindrical +in the basal half, spear-shaped or lanceolate in the distal half, with thin +edges, little longer, but five to eight times as {771}broad as the sixteen +smaller spines, which are cylindrical, of equal breadth throughout their +whole length, with bifid apex. Base of all twenty spines pyramidal, without +leaf-cross. Central capsule yellow, spherical, or lenticular. + +_Dimensions._--Length of the four major spines 0.066, breadth in the middle +0.005, on the apex 0.008; length of the sixteen smaller spines 0.054, +breadth 0.001. + +_Habitat._--Mediterranean (Messina), surface. + + + +Subgenus 2. _Staurolithium_, Haeckel, 1862, Monogr. d. Radiol., p. 401. + +_Definition._--All twenty spines in the centre melted and grown together, +forming one single, star-like piece of acanthin. + + +8. _Acanthostaurus cruciatus_, Haeckel. + + _Staurolithium cruciatum_, Haeckel, 1862, Monogr. d. Radiol., p. 401, + Taf. xx. fig. 6. + + _Astrolithium cruciatum_, Haeckel, 1860, Monatsber. d. k. preuss. Akad. + d. Wiss. Berlin, p. 811. + +Spines cylindrical, of equal breadth throughout their whole length. Apex +simple conical. Four equatorial spines twice as long and broad as the +sixteen other spines. All twenty spines in the centre melted and grown +together, forming a single piece of acanthin. Central capsule spherical, +red-brown, opaque. + +_Dimensions._--Length of the four equatorial spines 0.12, breadth 0.006; +length of the sixteen smaller spines 0.06, breadth 0.003. + +_Habitat._--Mediterranean (Messina), surface. + + + +Genus 335. _Belonostaurus_,[375] n. gen. + +_Definition._--#Quadrilonchida# with four equatorial spines of equal size +and form, which are much larger than the sixteen other spines. Eight +tropical and eight polar spines very different. No apophyses. + +The genus _Belonostaurus_ differs from the preceding _Acanthostaurus_ in +the unequal size and form of the eight tropical and the eight polar spines; +the latter are much smaller than the former and often quite rudimentary, so +that the skeleton appears composed only of twelve spines, four larger +equatorial and eight smaller tropical spines. The central bases of the +polar spines are constantly preserved. The central capsule is a flattened +square disk. + + +1. _Belonostaurus quadratus_, n. sp. + +Four equatorial spines little compressed, almost cylindrical in the basal +half, lanceolate, broader, with simple apex in the distal half. Eight +tropical spines a little shorter, but only half as broad, +{772}sword-shaped, two-edged, of equal breadth, with simple apex. Eight +polar spines very short, conical, also with simple apex. Base without +leaf-cross, a simple pyramid. + +_Dimensions._--Length of the four equatorial spines 0.18, of the eight +tropical spines 0.14, of the eight polar spines 0.04. + +_Habitat._--Central Pacific, Station 271, surface. + + +2. _Belonostaurus bicuspis_, n. sp. + +Four equatorial spines compressed, almost lanceolate in the basal half, +bifid, with two large, bent, little divergent horns in the distal half. +Eight tropical spines nearly of the same form, but only half as large, with +much smaller horns. Eight polar spines rudimentary, very short, conical, +with simple apex. Base with a large leaf-cross. + +_Dimensions._--Length of the four equatorial spines 0.2, of the eight +tropical spines 0.1, of the eight polar spines 0.02. + +_Habitat._--Central Pacific, Station 263, surface. + + + +Genus 336. _Lonchostaurus_,[376] Haeckel, 1862, Monogr. d. Radiol., p. 397 +(_sensu emendato_). + +_Definition._--#Quadrilonchida# with four equatorial spines of unequal size +and form; the principal spines (in the longitudinal axis) larger than the +lateral spines (in the transverse axis); both opposite spines of each pair +equal. Sixteen other spines much smaller (often the eight tropical larger +than the eight rudimentary polar spines). No apophyses. + +The genus _Lonchostaurus_ differs from the two preceding genera in the +unequal size and shape of both equatorial pairs of spines, whilst the two +opposite spines of each pair are equal. Therefore the equatorial plane is +here a rhombus, not a square, as in the preceding genera. We encounter here +for the first time the differentiation of the two equatorial axes, the +longitudinal (or hydrotomical) and the transverse (or geotomical) axis. The +sixteen other spines are constantly smaller (often also the eight polar +more or less rudimentary). + + +1. _Lonchostaurus rhomboides_, n. sp. (Pl. 131, fig. 6). + +Four equatorial spines cylindrical, twice to three times as broad as the +sixteen smaller spines, conical at the distal apex; the two opposite spines +of the longitudinal axis twice as long as those of the transverse axis. +Sixteen smaller spines conical at the base, with simple bristle-shaped +apex. The surface of the rhombical calymma, including the spines, was +covered in the figured specimen with small plates like those of +_Sphaerocapsa_. + +_Dimensions._--Length of the cross (longitudinal axis) 0.24, breadth +(transverse axis) 0.12. + +_Habitat._--South Pacific, Station 302, depth 1450 fathoms. + + +{773}2. _Lonchostaurus lanceolatus_, n. sp. + +Four equatorial spines compressed, lanceolate, tapering equally from the +middle towards the two ends; the two opposite spines of the longitudinal +axis one and a half times as long as those of the transverse axis. Sixteen +smaller spines compressed, linear, two-edged, half as long and only +one-fourth as broad as the two longitudinal spines. + +_Dimensions._--Length of the equatorial cross 0.3, breadth 0.2. + +_Habitat._--Central Pacific, Station 272, surface. + + +3. _Lonchostaurus bifidus_, n. sp. + +Four equatorial spines compressed, nearly rectangular, forked, with two +long and thin, bent, little divergent horns; the two opposite spines of the +longitudinal axis about one-third longer and broader than those of the +transverse axis. Sixteen smaller spines of the same form, also forked, but +the eight tropical only half as large, and the eight polar spines scarcely +one-fourth as large as the two longitudinal spines. + +_Dimensions._--Length of the equatorial cross 0.36, breadth 0.26. + +_Habitat._--South-west Pacific, Station 166, surface. + + +4. _Lonchostaurus bifurcus_, n. sp. (Pl. 131, fig. 4). + +Four equatorial spines nearly rhomboidal, about one and a half times as +large as the eight tropical and three times as large as the eight polar +spines; the two opposite spines of the longitudinal axis only with two +large divergent straight horns; the two spines of the transverse axis +somewhat shorter, with four short horns (the two outer horns longer than +the two inner). Eight tropical spines doubly forked, each with four thin +bristle-shaped horns. Eight polar spines very short, each with two thin +bristle-shaped, much divergent horns. + +_Dimensions._--Length of the equatorial cross 0.34, breadth 0.28. + +_Habitat._--North-west Pacific, Station 236, surface. + + +5. _Lonchostaurus rhombicus_, n. sp. + +Four equatorial spines nearly rhomboidal, tapering from the broader middle +towards the two ends. Leaf-cross of their base very large. The two opposite +spines of the longitudinal axis about one-third larger than the two spines +of the transverse axis. Eight tropical spines of the same form, but only +half as large. Eight polar spines rudimentary, very short, conical. + +_Dimensions._--Length of the equatorial cross 0.4, breadth 0.3. + +_Habitat._--North Pacific, Station 253, surface. + + +6. _Lonchostaurus crystallinus_, n. sp. (Pl. 131, fig. 5). + +Four equatorial spines lanceolate or rhomboidal, with broad leaf-cross at +the base, of a peculiar crystalline structure and a lamellated surface, +both opposite spines of the longitudinal axis twice as {774}large as the +two spines of the transverse axis. Eight tropical spines of similar form, +but only half as large, and with a very large, extremely prominent, +lamellated leaf-cross. Eight polar spines quite rudimentary, scarcely +prominent. + +_Dimensions._--Length 0.36, breadth 0.2. + +_Habitat._--Central Pacific, Station 271, surface. + + + +Genus 337. _Zygostaurus_,[377] n. gen. + +_Definition._--#Quadrilonchida# with four equatorial spines of unequal size +and form; both lateral spines (in the transverse axis) equal; but both +principal spines (in the longitudinal axis) very different, the frontal +larger than the caudal. Sixteen other spines much smaller (often the eight +tropical larger than the eight rudimentary polar spines). No apophyses. + +The genus _Zygostaurus_ differs from all other Staurolonchida in the +peculiar differentiation of the four equatorial spines; the two opposite +spines of the hydrotomical or longitudinal axis being very different in +size and form (the frontal spine forked, the caudal spine simple); whilst +the two opposite spines of the geotomical or lateral axis (perpendicular to +the former) are equal, forked, but different in shape from the former. +Therefore the geometrical fundamental form of the body in this remarkable +genus becomes "amphithect" or "bilateral" in the widest signification of +this term (comp. my General Morphology, vol. i. pp. 480, 482). Of the three +different dimensive axes one (the longitudinal) exhibits unequal poles, +whilst the two other (the sagittal and lateral) axes exhibit equal poles. + + +1. _Zygostaurus amphithectus_, n. sp. (Pl. 131, fig. 7). + +Frontal spine (_c_1) little different from the two lateral spines; each +with two divergent curved horns, which are equal and of about the same +length as the simple broad basal part. Caudal spine (_c_3) simple, +spindle-shaped, about as long as the frontal spine. Tropical spines little +smaller than the three former, and of the same symmetrical forked form. +Eight polar spines much smaller, but also forked, with thin bristle-shaped +branches. + +_Dimensions._--Length of the cross (longitudinal axis) 0.5, breadth +(lateral axis) 0.4. + +_Habitat._--Central Pacific, Station 272, surface. + + +2. _Zygostaurus longicornis_, n. sp. + +Frontal spine (_c_1) little different from the two lateral spines, each +with two divergent curved horns, which are equal and of about the same +length as the simple broad basal part. Caudal {775}spine (_c_3) simple, +lanceolate, shorter than the frontal spine. Eight tropical spines in the +basal part smaller than the three former, but with much longer +fork-branches, which are prolonged into very thin and long bristles. Eight +polar spines rudimentary, very short. + +_Dimensions._--Length of the equatorial cross 0.4, breadth 0.3. + +_Habitat._--South Pacific, Station 295, surface. + + +3. _Zygostaurus cornutus_, n. sp. + +Frontal spine (_c_1) little different from the two lateral spines, each +with two divergent straight horns, which are shorter than the basal part. +Caudal spine (_c_3) simple, triangular, shorter than the three former. +Eight tropical spines of equal size and form, doubly forked, each with four +thin, bristle-shaped, little divergent teeth. Eight polar spines short, +simply forked. + +_Dimensions._--Length of the equatorial cross 0.5, breadth 0.4. + +_Habitat._--Indian Ocean (Madagascar), Rabbe, surface. + + +4. _Zygostaurus caudatus_, n. sp. + +Frontal spine (_c_1) very different from the others, pincer-shaped, with +two long, nearly parallel slightly bent horns. Lateral spines (_c_2 and +_c_4) only half as long, with two short, nearly parallel horns. Caudal +spine (_c_3) very long and stout, spindle-shaped, about twice as long as +the frontal spine. Eight tropical spines of equal size and form, +symmetrical, with two long and thin, divergent horns. Eight polar spines +short and stout, with two divergent horns. + +_Dimensions._--Length of the equatorial cross 0.8, breadth 0.3. + +_Habitat._--Central Pacific, Station 265, surface. + + +5. _Zygostaurus frontalis_, n. sp. + +Frontal spine (_c_1) very different from the others, with two very long, +divergent, stout branches. Lateral spines (_c_2 and _c_4) only half as +long, each with two stout, nearly parallel horns of equal length. Caudal +spine (_c_3) simple, sword-like, shorter than the three former. Eight +tropical spines of equal size and form, symmetrical, of the same shape as +the two lateral, but only half as large. Eight polar spines very small, +rudimentary, each with two short teeth. + +_Dimensions._--Length of the equatorial cross 0.7, breadth 0.5. + +_Habitat._--Central Pacific, Station 274, surface. + + +6. _Zygostaurus sagittalis_, n. sp. (Pl. 131, fig. 8). + +Frontal spine (_c_1) very different from the others, with two equal, +strongly divergent, bent horns. Lateral spines (_c_2 and _c_4) little +smaller, but with two very unequal horns (the anterior shorter than the +posterior). Caudal spine (_c_3) simple, sword-like or triangular, +two-edged, longer {776}than the frontal spine. Eight tropical spines +different, the four anterior (_b_1, _b_4, _d_1, _d_4) smaller, with longer +horns; the four posterior (_b_2, _b_3, _d_2, _d_3) broader, with shorter +horns; the anterior horn of each tropical spine is longer than the +posterior. Eight polar spines rudimentary, simple, very short. + +_Dimensions._--Length of the equatorial spine-cross 0.6, breadth 0.4. + +_Habitat._--Central Pacific, Station 271, surface. + + + +Subfamily 2. LITHOPTERIDA, Haeckel. + +_Definition._--#Quadrilonchida# with two opposite transverse apophyses +either on all twenty spines or only on a part of them. + + + +Genus 338. _Quadrilonche_,[378] n. gen. + +_Definition._--#Quadrilonchida# with two simple opposite apophyses either +on each radial spine or only on a part of the twenty spines. + +The genus _Quadrilonche_ is the ancestral form of the Lithopterida, or of +those Quadrilonchida which bear two opposite apophyses or transverse +processes. In _Quadrilonche_ these apophyses are simple, whilst they are +branched in _Xiphoptera_ and fenestrated in _Lithoptera_. Each of these +three genera may be divided into three subgenera; in the first only the +four equatorial spines are provided with apophyses, in the second twelve +spines (four equatorial and eight tropical), in the third subgenus all +twenty spines. + + + +Subgenus 1. _Quadriloncharium_, Haeckel. + +_Definition._--Four large equatorial spines provided with transverse +apophyses; sixteen other smaller spines simple, without apophyses. + + +1. _Quadrilonche tetrastaura_, n. sp. + +Four equatorial spines very large, compressed, two-edged, each crossed in +the distal third by two opposite simple apophyses. Sixteen other spines +also compressed, linear, somewhat shorter than the former and only half as +broad, without apophyses. + +_Dimensions._--Length of the four major spines 0.12, breadth 0.02; length +of the sixteen minor spines 0.08, breadth 0.01. + +_Habitat._--Central Pacific, Station 266, surface. + + +{777}2. _Quadrilonche platystaura_, n. sp. (Pl. 131, fig. 2). + +Four equatorial spines lanceolate, compressed, with two opposite triangular +simple apophyses in the broadest middle part. Sixteen other spines also +lanceolate, much smaller, of about half the length, but only of one-fourth +the breadth, without apophyses. + +_Dimensions._--Length of the four major spines 0.2, breadth 0.018; length +of the sixteen minor spines 0.1, breadth 0.004. + +_Habitat._--North Pacific, Station 235, surface. + + + +Subgenus 2. _Quadrilonchidium_, Haeckel. + +_Definition._--All twenty spines provided with transverse apophyses. + + +3. _Quadrilonche mesostaura_, n. sp. (Pl. 131, fig. 1). + +Four equatorial spines almost of the some form and length as the sixteen +others, but of double or triple the breadth; each spine in its middle third +with two opposite broad triangular apophyses, in the basal third +rectangular, compressed, in the distal third isosceles triangular, with +simple apex. + +_Dimensions._--Length of the four major spines 0.16, breadth 0.01 to 0.015; +length of the sixteen minor spines 0.12, breadth 0.005. + +_Habitat._--Tropical Atlantic, Station 345, surface. + + +4. _Quadrilonche telostaura_, n. sp. + +Four equatorial spines one and a half times as long and three times as +broad as the sixteen others; all twenty spines cylindrical, of equal +breadth throughout their whole length, with simple conical apex; each spine +crossed in the distal third by two opposite, simple, conical apophyses. + +_Dimensions._--Length of the four major spines 0.3, breadth 0.012; length +of the sixteen minor spines 0.2, breadth 0.004. + +_Habitat._--South Atlantic, Station 325, surface. + + + +Genus 339. _Xiphoptera_,[379] Haeckel, 1881, Prodromus, p. 466. + +_Definition._--#Quadrilonchida# with two opposite branched (but not +latticed) apophyses, either on each radial spine or only on a part of the +twenty spines. + +The genus _Xiphoptera_ differs from the preceding ancestral genus +_Quadrilonche_ in the ramification of the apophyses, which bear +perpendicular branches on their distal side. These are therefore parallel +to the spine itself. If the branches become united by transverse beams then +we get _Lithoptera_. + + +{778}1. _Xiphoptera tessaractena_, n. sp. + +Four equatorial spines in the outer third crossed by two opposite +transverse apophyses, each of which bears on its distal side two to three +branches, perpendicular to the apophysis and parallel to the spine itself. +Sixteen other spines much smaller, in the outer third crossed by two simple +opposite transverse apophyses. + +_Dimensions._--Length of the four major spines 0.18, of the sixteen minor +0.05 to 0.1. + +_Habitat._--North Pacific, Station 238, surface. + + +2. _Xiphoptera dodecactena_, n. sp. (Pl. 131, fig. 3). + +Four equatorial spines one and a half times to twice as long and broad as +the eight tropical spines. These twelve spines have the same form and are +crossed in their distal third by two large opposite transverse apophyses, +each of which bears on its distal side two to four branches, perpendicular +to the apophysis and parallel to the spine. Eight polar spines much smaller +than the twelve others, simple, without apophyses. The central capsule of +this species exhibited a conical protuberance around the base of each +individual spine. + +_Dimensions._--Length of the twelve larger spines 0.1 to 0.2, of the eight +smaller 0.02 to 0.06. + +_Habitat._--Central Pacific, Station 272, surface. + + +3. _Xiphoptera icosactena_, n. sp. + +Four equatorial spines about twice as long and four times as broad as the +sixteen other spines. All twenty spines crossed in the outer third by two +large opposite transverse apophyses, each of which bears on its distal side +two to four branches perpendicular to the apophysis and parallel to the +spine itself. + +_Dimensions._--Length of the four equatorial spines 0.26, of the sixteen +smaller 0.11 to 0.14. + +_Habitat._--South Pacific, Station 288, surface. + + + +Genus 340. _Lithoptera_,[380] J. Mueller, 1858, Monatsber. d. k. preuss. +Akad. d. Wiss. Berlin, p. 155. + +_Definition._--#Quadrilonchida# with two opposite branched and latticed +apophyses, either on each radial spine or only on a part of the twenty +spines. + +The genus _Lithoptera_, founded by Johannes Mueller in 1858 for the first +observed Mediterranean species, _Lithoptera fenestrata_, differs from all +other Quadrilonchida in the fenestrated form of the apophyses, which he +compared to the sails of a windmill. This peculiar fenestration is effected +by two to four parallel pairs of opposite apophyses, which are crossed by +perpendicular branches, parallel to the spine itself. {779}Therefore the +wings or lattice-plates have quadrangular meshes and lie in one meridian +plane of the spine, not in a tangential plane (as in the _Acanthophracta_). +Commonly the lateral ends of the four broad equatorial wings are so crossed +that one lateral corner of each wing lies on the upper, the other corner on +the under side of both its neighbours; but sometimes the meeting corners +have grown together. + + + +Subgenus 1. _Lithopteranna_, Haeckel. + +_Definition._--Four equatorial spines with transverse apophyses; sixteen +others (eight tropical and eight polar spines) simple, without apophyses. + + +1. _Lithoptera tetraptera_, n. sp. (Pl. 131, fig. 9). + +Four equatorial spines spindle-shaped, with latticed apophyses, each +crossed by two transverse beams which are connected at equal distances by +four rods parallel to the spine (therefore each wing with four square +meshes in a single row). Lateral corners of the neighbouring wings not +meeting. Sixteen smaller spines (eight tropical and eight polar) simple, +conical, without apophyses. + +_Dimensions._--Diagonal of the square body 0.24; length of the inner square +0.16. + +_Habitat._--Tropical Atlantic, Station 348, surface. + + +2. _Lithoptera muelleri_, Haeckel. + + _Lithoptera muelleri_, Haeckel, 1862, Monogr. d. Radiol., p. 398, Taf. + xx. figs. 1, 2. + +Four equatorial spines four-edged, with large latticed apophyses, each +crossed by three transverse beams, which are connected at irregular +distances by eight to twelve rods parallel to the spine (therefore each +wing with two rows of rectangular meshes). The wings are placed not +perfectly in the equatorial plane, but a little obliquely, so that each +wing lies with one lateral corner on the upper, with the other corner on +the under side of its neighbours. Sixteen smaller spines simple, thin, +cylindrical, without apophyses. + +_Dimensions._--Diagonal of the square body 0.3; length of the inner square +0.17. + +_Habitat._--Mediterranean (Messina), surface. + + +3. _Lithoptera lamarckii_, n. sp. + +Four equatorial spines four-edged, with large latticed apophyses; each +crossed by three transverse beams, which are connected at short distances +by twelve to sixteen rods parallel to the spine (therefore each wing with +two rows of hexagonal or nearly elliptical meshes). Wings placed as in +_Lithoptera muelleri_. Sixteen smaller spines simple, thin, prismatic, +without apophyses. + +_Dimensions._--Diagonal of the square body 0.35; length of the inner square +0.2. + +_Habitat._--Central Pacific, Station 271, surface. + + +{780}4. _Lithoptera tetragona_, n. sp. + +Four equatorial spines compressed, four-edged, with large latticed +apophyses, each crossed by four transverse beams, which are connected at +regular distances by eight to twelve rods parallel to the spine. (Therefore +each wing with three rows of square meshes.) Wings placed in the equatorial +plane and grown together by their meeting lateral ends, forming a square +equatorial girdle of lattice-work. Sixteen smaller spines simple, thin, +prismatic, without apophyses. + +_Dimensions._--Diameter of the square body 0.4; length of the inner square +0.22. + +_Habitat._--North Pacific, Station 244, surface. + + + +Subgenus 2. _Lithopterella_, Haeckel. + +_Definition._--Twelve spines (four equatorial and eight tropical) with +transverse apophyses; the eight polar spines simple, without apophyses. + + +5. _Lithoptera quadrata_, n. sp. (Pl. 131, fig. 10). + +Twelve spines with transverse apophyses; eight (polar) spines simple, +small, without apophyses. Four equatorial spines very large and stout, +compressed, each crossed by four transverse beams, which are connected by +eight to ten rods parallel to the spine (therefore each wing with three +rows of irregular rectangular meshes). Wings placed in the equatorial plane +and grown together by their meeting lateral ends, forming a square +equatorial girdle of lattice-work. Eight tropical spines thin, crossed by a +long and thin transverse beam, which bears on its distal side eight to ten +rods parallel to the spine. + +_Dimensions._--Diagonal of the square body 0.35; length of the inner square +0.18. + +_Habitat._--South Atlantic, Station 326, surface. + + +6. _Lithoptera dodecaptera_, n. sp. + +Twelve spines with transverse apophyses; eight (polar) spines simple, +small, without apophyses. Four equatorial spines very large, quadrangular; +each crossed by three transverse beams, which are connected by ten to +twelve rods parallel to the spine (therefore each wing with two rows of +square meshes). Wings placed as in _Lithoptera muelleri_. Eight tropical +spines much thinner, crossed each by two transverse beams, which are +connected by six to eight rods parallel to the spine (therefore each wing +with one row of rectangular meshes). + +_Dimensions._--Diagonal of the square body 0.4; length of the inner square +0.25. + +_Habitat._--Central Pacific, Station 271, surface. + + + +Subgenus 3. _Lithopteromma_, Haeckel. + +_Definition._--All twenty spines with transverse apophyses. + + +{781}7. _Lithoptera darwinii_, Haeckel. + + _Lithoptera darwinii_, Haeckel, 1879, Natuerl. Schoepfungsgesch., Aufl. + vii. p. 706, Taf. xvi. fig. 12. + +All twenty spines with transverse apophyses; these are quite simple in the +eight small cross-shaped polar spines; also simple, but bearing some +perpendicular rods, in the eight thin tropical spines. Four equatorial +spines very large and stout, each crossed by four transverse beams, which +are connected by eight to ten rods parallel to the spine (therefore each +wing with three rows of irregular rectangular meshes). Wings placed in the +equatorial plane and grown partly together by their meeting lateral ends. + +_Dimensions._--Diagonal of the square body 0.4; length of the inner square +0.2. + +_Habitat._--South-east Pacific, west coast of Patagonia, Station 302, +surface. + + +8. _Lithoptera icosaptera_, n. sp. + +All twenty spines with transverse apophyses, bearing one to three rows of +rectangular meshes; eight polar spines small, each with a single row; eight +tropical spines long and thin, each with two parallel rows. Four equatorial +spines much larger and thicker, each with three parallel transverse rows of +meshes. All twenty wings free, not grown together by their lateral ends. + +_Dimensions._--Diagonal of the square body 0.48; length of the inner square +0.24. + +_Habitat._--Indian Ocean, Belligemma, Ceylon (Haeckel), surface. + + +9. _Lithoptera fenestrata_, J. Mueller. + + _Lithoptera fenestrata_, J. Mueller, 1858, Abhandl. d. k. Akad. d. Wiss. + Berlin, p. 154, Taf. xi. fig. 13. + +All twenty spines with transverse apophyses, bearing one to three rows of +irregular, rectangular meshes; eight polar and eight tropical spines small, +each with a single row of meshes (between two parallel transverse beams). +Four equatorial spines little larger, each with two rows (between three +parallel transverse beams). Central capsule filled up with green pigment. + +_Dimensions._--Diagonal of the square body 0.3; length of the inner square +0.2. + +_Habitat._--Mediterranean (Saint Tropez, Nice). + + + +Family XXXVIII. #AMPHILONCHIDA#, Haeckel (Pl. 132). + +_Acantholonchida_ (Amphilonchida et Amphilithida), Haeckel, 1881, +Prodromus, p. 466. + +_Definition._--ACANTHARIA with twenty radial spines of very unequal size, +disposed according to the law of the Icosacantha; two opposite equatorial +spines (in the longitudinal axis) much larger than the eighteen others. No +lattice-shell. + +The family #Amphilonchida# is distinguished from all other #Acanthometra# +by the excessive development of two opposite equatorial spines, which are +much larger {782}than the eighteen other spines. In my Monograph (1862, p. +389) I had united all these Acanthonida in a single genus _Amphilonche_ +(with ten species). Some species of it are very common and widely +distributed; but in general the number of different forms in this family is +much smaller than in the two foregoing families. + +The two principal spines, which in all Amphilonchida are much larger than +the eighteen other spines, characterise the "hydrotomical axis" or the +larger equatorial axis. The two other equatorial spines or the "geotomical +spines" are much smaller, and commonly of the same size as the eight +tropical and the eight polar spines. In the genera _Amphilonche_ and +_Amphibelone_ these eighteen smaller spines are rather equally developed; +sometimes they are very small or quite rudimentary, so that the skeleton +seems to be represented only by the two very long principal spines (Pl. +132, fig. 4). The genus _Acantholonche_ is distinguished by the unequal +size of the eight tropical and the eight polar spines, the latter being +more or less rudimentary. However, the central bases of all twenty spines, +by which they are united in the centre, are constantly present. The genus +_Amphibelone_ is distinguished by the unequal size and form of the two +principal spines, one of them the "caudal spine," being larger (and often +of another form) than the opposite "frontal spine." + +The form of the radial spines is in the Amphilonchida far less varied and +complicated than in the other Acanthonida (the Astrolonchida and +Quadrilonchida). Apophyses or lateral transverse processes are never +developed. The three main forms of spines are the same as in the other +Acanthonida; they are (1) either cylindrical or conical (like +_Acanthometron_), or (2) compressed or two-edged (like _Zygacantha_), or +(3) quadrangular or four-edged (like _Acanthonia_). Often the spines are +angular in the inner or proximal, roundish in the outer or distal part. The +distal apex is commonly simple, conical or pyramidal. The central base is +commonly also pyramidal, as in the majority of the Acanthonida; and the +triangular faces of the neighbouring bases are simply propped one upon +another. More rarely a basal leaf-cross is developed above the basal +pyramid. Very rarely the central bases of the united spines grow together +in the centre, so that the whole skeleton forms a single piece of acanthin. + +_The Central Capsule_ is rarely spherical, commonly prolonged in the +direction of the hydrotomical axis; ellipsoidal or cylindrical, sometimes +also four-sided prismatic; it commonly envelops the greater part of the two +principal spines; its structure and contents are the same as in the other +Acanthonida. + +_Synopsis of the Genera of Amphilonchida._ + + { Two opposite large + { principal spines + Eighteen smaller spines { (frontal and caudal) + of nearly equal size { equal, 341. _Amphilonche_. + and similar form. { + { Caudal spine larger than + { the frontal spine, 342. _Amphibelone_. + + Eight tropical and eight polar spines of different + sizes (the latter often rudimentary), 343. _Acantholonche_. + + + +{783}Genus 341. _Amphilonche_,[381] Haeckel, 1862, Monogr. d. Radiol., p. +389. + +_Definition._--#Amphilonchida# with two equal principal spines (frontal and +caudal spines not different); the eighteen smaller spines nearly equal. + +The genus _Amphilonche_ represents the original and at the same time the +most common form of Amphilonchida; the two opposite principal spines are of +equal size and form, much larger (and often also of another form) than the +eighteen smaller spines; these latter exhibit no marked differences in size +and form. + + + +Subgenus 1. _Amphiloncharium_, Haeckel. + +_Definition._--Spines in the centre united by triangular faces of their +pyramidal bases, propped one upon another. No basal leaf-cross. + + +1. _Amphilonche belonoides_, Haeckel. + + _Amphilonche belonoides_, Haeckel, 1862, Monogr. d. Radiol., p. 392, Taf. + xvi. fig. 6, Taf. xviii. fig. 21. + + _Acanthometra belonoides_, Haeckel, 1860, Monatsber. d. k. Akad. d. Wiss. + Berlin, p. 808. + +Two principal spines cylindrical, of equal breadth throughout their whole +length, with simple conical apex; base a small pyramid, without leaf-cross. +Eighteen smaller spines conical, much shorter, with simple bristle-shaped +apex. Central capsule spindle-shaped or cylindrical, yellow. + +_Dimensions._--Length of the two major spines 0.4 to 0.8, of the eighteen +minor 0.05 to 0.2. + +_Habitat._--Cosmopolitan; Mediterranean, Atlantic, Pacific, surface. + + +2. _Amphilonche lanceolata_, n. sp. (Pl. 132, fig. 1). + +Two principal spines compressed, lanceolate, two-edged, gradually tapering +from the broader middle towards the two ends; apex simple; base a large +pyramid, with broad leaf-cross. Eighteen smaller spines about half as long, +pyramidal, with simple conical or bristle-shaped apex. Central capsule +lentelliptical, pink, opaque. + +_Dimensions._--Length of the two major spines 0.2, of the eighteen minor +0.1. + +_Habitat._--Tropical Atlantic, Station 343, surface. + + +3. _Amphilonche diodon_, n. sp. (Pl. 132, fig. 3). + +Two principal spines compressed, lanceolate, two-edged, tapering from the +broader middle towards the two ends; apex simple; base a small pyramid, +without leaf-cross. Eighteen smaller spines {784}sword-shaped, only +two-thirds or one-half as long, and one-third or one-fourth as broad, each +with two opposite teeth in the distal part. Central capsule ellipsoidal. + +_Dimensions._--Length of the two major spines 0.13, breadth 0.02; length of +the eighteen minor spines 0.1. + +_Habitat._--North Atlantic, Station 352, surface. + + +4. _Amphilonche tenuis_, Haeckel. + + _Amphilonche tenuis_, Haeckel, 1862, Monogr. d. Radiol., p. 389, Taf. + xvi. fig. 1, Taf. xviii. fig. 16. + + _Acanthometra tenuis_, Haeckel, 1860, Monatsber. d. k. Akad. d. Wiss. + Berlin, p. 807. + +Two principal spines quadrangular prismatic, with smooth edges, slightly or +not at all prominent, of equal breadth throughout their whole length; apex +simple or bifid; base a small pyramid, without leaf-cross. Eighteen smaller +spines of the same form, but only one-fourth or one-third as long. Central +capsule spherical or ellipsoidal, colourless. + +_Dimensions._--Length of the two major spines 0.2 to 0.3, of the eighteen +minor spines 0.05 to 0.1. + +_Habitat._--Mediterranean (Messina); Atlantic, Station 354, Canary Islands, +surface. + + +5. _Amphilonche denticulata_, Haeckel. + + _Amphilonche denticulata_, Haeckel, 1862, Monogr. d. Radiol., p. 390, + Taf. xvi. fig. 2, Taf. xviii. fig. 17. + +Two principal spines quadrangular prismatic, with prominent, elegantly +denticulated edges, of equal breadth throughout their whole length; apex +simple or truncated; base a small pyramid, without leaf-cross. Eighteen +smaller spines of the same form, but only one-fourth or one-third as long. +Central capsule ellipsoidal, opaque, yellowish-brown. + +_Dimensions._--Length of the two major spines 0.3 to 0.4, of the eighteen +minor 0.1; breadth of the former 0.009, of the latter 0.006. + +_Habitat._--Mediterranean (Messina), Haeckel, surface. + + +6. _Amphilonche heteracantha_, Haeckel. + + _Amphilonche heteracantha_, Haeckel, 1862, Monogr. d. Radiol., p. 293, + Taf. xvi. fig. 7. + + _Acanthometra heteracantha_, Haeckel, 1860, Monatsber. d. k. Akad. d. + Wiss. Berlin, p. 808. + +Two principal spines quadrangular prismatic, very large, with four broad, +prominent, lamellar edges, of equal breadth throughout their whole length. +Apex as well as the base a four-sided pyramid. Eighteen smaller spines very +thin, conical, with bristle-shaped apex; base a small pyramid, without +leaf-cross. Central capsule cylindrical or violin-shaped, opaque yellow. + +_Dimensions._--Length of the two major spines 0.2 to 0.3, breadth 0.015 to +0.02; length of the eighteen minor spines 0.1 to 0.15, basal breadth 0.004 +to 0.008. + +_Habitat._--Mediterranean (Messina); Central Pacific, Station 271, surface. + + +{785}7. _Amphilonche elongata_, Haeckel. + + _Amphilonche elongata_, Haeckel, 1862, Monogr. d. Radiol., p. 392, Taf. + xviii. figs. 22_a_, 22_b_. + + _Acanthometra elongata_, J. Mueller, 1858, Abhandl. d. k. Akad. d. Wiss. + Berlin, p. 48, Taf. vii. fig. 13. + +Two principal spines quadrangular prismatic in the proximal half, +cylindrical or spindle-shaped in the distal half, with simple apex; base a +small pyramid, without leaf-cross. Eighteen smaller spines very thin, +bristle-shaped, conical on the base, with small pyramid. Central capsule +spindle-shaped, transparent, yellow. + +_Dimensions._--Length of the two major spines 0.3 to 0.5, breadth 0.01 to +0.03; length of the eighteen smaller spines 0.05 to 0.3. + +_Habitat._--Cosmopolitan; Mediterranean, Atlantic, Indian, Pacific, +surface. + + + +Subgenus 2. _Amphilonchidium_, Haeckel. + +_Definition._--Spines at the central base with a broad leaf-cross, composed +of four prominent triangular lamellae; between the meeting edges of the +latter twenty-two pyramidal compartments or basal funnels. + + +8. _Amphilonche ovata_, Haeckel. + + _Amphilonche ovata_, Haeckel, 1862, Monogr. d. Radiol., p. 390. + + _Acanthometra ovata_, J. Mueller, 1858, Abhandl. d. k. Akad. d. Wiss. + Berlin, p. 47, Taf. vii. fig. 10, Taf. ix. fig. 4. + +Two principal spines cylindrical, of equal breadth throughout their whole +length, with simple conical or bifid apex; base with a large leaf-cross of +double the breadth. Eighteen smaller spines of the same form, but thinner +and only half as long. Central capsule ellipsoidal, brown, opaque. + +_Dimensions._--Length of the two major spines 0.3 to 0.4, breadth 0.008 to +0.012; length of the eighteen minor spines 0.1 to 0.2. + +_Habitat._--Cosmopolitan; Mediterranean, Atlantic, Pacific, surface. + + +9. _Amphilonche conica_, n. sp. (Pl. 132, fig. 6). + +Two principal spines conical, elongate, with simple apex; base thickened, +with large leaf-cross. Eighteen smaller spines also conical, of about the +same basal breadth, but only one-fourth to one-half as long. Central +capsule ellipsoidal, pellucid. + +_Dimensions._--Length of the two major spines 0.15 to 0.2, basal breadth +0.03 to 0.04; length of the eighteen minor spines 0.05 to 0.1. + +_Habitat._--Central Pacific, Stations 265 to 274, surface. + + +{786}10. _Amphilonche lancetta_, n. sp. + +Two principal spines compressed, lanceolate, two edged, gradually tapering +from the broader middle towards the two ends; apex simple; base of double +the breadth, with a large leaf-cross. Eighteen smaller spines of the same +form, but shorter and only half as broad. Central capsule lentelliptical, +pellucid. + +_Dimensions._--Length of the two major spines 0.2 to 0.3, breadth in the +middle part 0.02 to 0.03; length of the eighteen smaller spines 0.1 to 0.2. + +_Habitat._--South Pacific, Station 288, surface. + + +11. _Amphilonche complanata_, Haeckel. + + _Amphilonche complanata_, Haeckel, 1862, Monogr. d. Radiol., p. 390, Taf. + xvi. fig. 3, Taf. xviii. fig. 18, _a_, _b_. + + _Acanthometra complanata_, Haeckel, 1860, Monatsber. d. k. preuss. Akad. + d. Wiss. Berlin, p. 808. + +Two principal spines compressed, two-edged, linear, of equal breadth +throughout their whole length; apex emarginate or bifid; base with a large +leaf-cross of double the breadth. Eighteen smaller spines of the same form, +but only one-fourth to one-half as large. Central capsule ellipsoidal, +yellow, pellucid. + +_Dimensions._--Length of the two major spines 0.15 to 0.25, breadth 0.004 +to 0.006; length of the eighteen minor spines 0.05 to 0.1. + +_Habitat._--Mediterranean (Messina), surface. + + +12. _Amphilonche messanensis_, Haeckel. + + _Amphilonche messanensis_, Haeckel, 1862, Monogr. d. Radiol., p. 391, + Taf. xvi. fig. 4, Taf. xviii. fig. 19. + + _Acanthometra messanensis_, Haeckel, 1860, Monatsber. d. k. preuss. Akad. + d. Wiss. Berlin, p. 808. + +Two principal spines quadrangular prismatic, often a little compressed from +two sides, of nearly equal breadth throughout their whole length; apex +either truncate or emarginate, with two opposite teeth; base with a large +leaf-cross of double the breadth. Eighteen smaller spines of similar form +or more compressed, much shorter. Central capsule spherical or ellipsoidal, +yellow, transparent. + +_Dimensions._--Length of the two major spines 0.12 to 0.18, breadth 0.016; +length of the minor spines 0.05 to 0.09. + +_Habitat._--Mediterranean (Messina, Corfu), Haeckel, surface. + + +13. _Amphilonche hydrotomica_, n. sp. (Pl. 132, fig. 2). + +Two principal spines quadrangular prismatic, with four broad prominent +lamellar edges or wings, of equal breadth throughout their whole length; +apex pyramidal; base with a large leaf-cross. Eighteen smaller spines +cylindrical or bristle-shaped, only half as long and very thin. Central +capsule cylindrical or spindle-shaped, very long, opaque. + +{787}_Dimensions._--Length of the two major spines 0.1 to 0.2, breadth 0.02 +to 0.03; length of the eighteen minor spines 0.05 to 0.1. + +_Habitat._--Central Pacific, Stations 270 to 274, surface. + + +14. _Amphilonche violina_, n. sp. (Pl. 132, fig. 5). + +Two principal spines quadrangular prismatic, nearly violin-shaped, with +four very broad, prominent, lamellar wings, which are constricted in the +middle part, and broadened towards the two ends; apex truncate pyramidal; +base with a large leaf-cross. Eighteen smaller spines much shorter, of +equal breadth at the base, assuming the form of a quadrangular pyramid, +thin prismatic in the distal half. Central capsule spindle-shaped, opaque. + +_Dimensions._--Length of the two major spines 0.15 to 0.18, breadth 0.02 to +0.025; length of the eighteen minor spines 0.04 to 0.08. + +_Habitat._--Central Pacific, Station 271, surface. + + +15. _Amphilonche tetraptera_, Haeckel. + + _Amphilonche tetraptera_, Haeckel, 1862, Monogr. d. Radiol., p. 391, Taf. + xvi. fig. 5, Taf. xviii. fig. 20. + + _Acanthometra tetraptera_, Haeckel, 1860, Monatsber. d. k. preuss. Akad. + d. Wiss. Berlin, p. 808. + +Two principal spines four-sided pyramidal, with four broad lamellar +prominent edges; apex simple or bifid; base with a large leaf-cross. +Eighteen smaller spines of similar form, but only half as large. Central +capsule spherical, opaque. + +_Dimensions._--Length of the two major spines 0.2, breadth on the base +0.025; length of the eighteen minor spines 0.1. + +_Habitat._--Mediterranean (Messina); North Atlantic, Canary Islands, +Stations 352 to 354, surface. + + + +Subgenus 3. _Amphilithium_, Haeckel, 1881, Prodromus, p. 466. + +_Definition._--Spines in the basal part grown together, so that the whole +skeleton represents a single piece of acanthin; a star with two larger and +eighteen smaller rays. + + +16. _Amphilonche concreta_, n. sp. (Pl. 132, figs. 4, 4_a_). + +Two principal spines cylindrical, very long, of equal breadth throughout +their whole length, with simple conical apex. Eighteen smaller spines +short, conical or bristle-shaped, scarcely one-fourth or one-tenth as long, +often quite rudimentary. All twenty spines perfectly grown together in the +centre, forming a single piece of acanthin (derived from _Amphilonche +belonoides_ by central concrescence; often the sutures of the concreted +bases are visible, fig. 4_a_). + +_Dimensions._--Length of the two major spines 0.1 to 0.4, breadth 0.005 to +0.015; length of the eighteen minor spines 0.005 to 0.15. + +_Habitat._--Cosmopolitan; Mediterranean, Atlantic, Pacific, surface. + + +{788}17. _Amphilonche acufera_, n. sp. + +Two principal spines thick, four-sided prismatic in the basal half, +cylindrical or spindle-shaped in the distal half, with simple conical apex. +Eighteen smaller spines shorter, thin, bristle-shaped or conical on the +base. All twenty spines in the centre perfectly grown together, forming a +single piece of acanthin. (Derived from _Amphilonche elongata_ by central +concrescence.) + +_Dimensions._--Length of the two major spines 0.3 to 0.5, breadth 0.01 to +0.03; length of the eighteen minor spines 0.08 to 0.2. + +_Habitat._--Central Pacific, Stations 266 to 274, surface. + + + +Genus 342. _Amphibelone_,[382] Haeckel, 1862, Monogr. d. Radiol., p. 392. + +_Definition._--#Amphilonchida# with two unequal principal spines (the +frontal spine very different from the caudal spine); the eighteen smaller +spines nearly equal. + +The genus _Amphibelone_ exhibits among the Amphilonchida the same +remarkable differentiation of the two principal or longitudinal spines, as +_Zygostaurus_ among the Quadrilonchida; the frontal spine differs commonly +from the caudal spine not only in its size, but also in its peculiar form; +commonly one pole of the longitudinal axis is much more strongly developed +than the other. The eighteen smaller spines are nearly equal. + + + +Subgenus 1. _Amphibelonium_, Haeckel. + +_Definition._--All twenty spines separate, but in contact in the centre and +resting one against another by the triangular sides of their pyramidal +bases, without a prominent basal leaf-cross. + + +1. _Amphibelone aciculata_, n. sp. + +Two principal spines thick, without edges and wings, the frontal spine +short, spindle-shaped, the caudal three to six times as long, cylindrical, +both of equal breadth, with simple conical apex and simple pyramidal base, +without leaf-cross. Eighteen smaller spines very thin, bristle-shaped, of +the same length as the frontal spine. Central capsule cylindrical or +spindle-shaped, enveloping the two principal spines nearly throughout their +whole length. + +_Dimensions._--Length of the frontal spine 0.2 to 0.4, of the caudal spine +1.0 to 2.0; breadth of both 0.01; length of the eighteen smaller spines 0.1 +to 0.3. + +_Habitat._--South Atlantic, Station 325, surface. + + +{789}2. _Amphibelone cultellata_, n. sp. (Pl. 132, fig. 10). + +Two principal spines broad, two-edged, knife-shaped; two opposite in the +equatorial plane, thin and broad wings or lamellae are developed, and these +enclose the proximal part of both spines, whilst their distal part is free, +cylindrical, with conical apex: the two wings of the longer caudal spine +are lanceolate, twice to four times as broad as the two wings of the +shorter frontal spine; their base is a simple pyramid without leaf-cross. +Eighteen smaller spines conical, with bristle-shaped prolongation, +one-fourth to one-half as long as the frontal spine. Central capsule green, +semitransparent. + +_Dimensions._--Length of the frontal spine 0.1 to 0.2, breadth 0.02 to +0.03; length of the caudal spine 0.2 to 0.4, breadth 0.04 to 0.08; length +of the eighteen smaller spines 0.05 to 0.15. + +_Habitat._--Indian Ocean, Maldive Islands (Haeckel), surface. + + +3. _Amphibelone pyramidata_, n. sp. (Pl. 132, fig. 9). + +Two principal spines four-winged, with four crossed, very thin and broad +wings, which are somewhat broader in the convex middle part than at either +end; both ends of each spine four-sided pyramidal, with four concave edges +and a very small terminal pyramid; base without leaf-cross. The longer +caudal spine is twice as broad at the distal end as at its proximal end, +and three times as broad as the distal end of the shorter frontal spine. +Eighteen smaller spines bristle-shaped, with four-sided pyramidal bases. +Central capsule pyramidal, enveloping the two principal spines throughout +their whole length; the base of the slender quadrangular pyramid is on the +caudal, the apex on the frontal pole of the longitudinal axis. + +_Dimensions._--Length of the frontal spine 0.2 to 0.25, distal breadth +0.01; length of the caudal spine 0.3 to 0.4, distal breadth 0.03; length of +the eighteen smaller spines 0.04 to 0.08. + +_Habitat._--Cape of Good Hope, Station 143, depth 1900 fathoms. + + +4. _Amphibelone anomala_, Haeckel. + + _Amphilonche anomala_, Haeckel, 1862, Monogr. d. Radiol., p. 394, Taf. + xvi. fig. 8, Taf. xviii. figs. 23_a_, 23_b_. + + _Acanthometra anomala_, Haeckel, 1860, Monatsber. d. k. Akad. d. Wiss. + Berlin, p. 808. + +Two principal spines four-winged, nearly prismatic, with four crossed, very +broad and thick wings; both ends of each spine four-sided pyramidal, with +four concave edges and a very small terminal pyramid; base without +leaf-cross. The edges of the four wings are concave on the shorter frontal, +convex on the longer caudal spine. Eighteen smaller spines only one-fourth +to one-half as long, linear, two-edged, with two parallel teeth on the +distal end. Central capsule four-sided prismatic, olive-green, enveloping +almost completely the two principal spines. + +_Dimensions._--Length of the frontal spine 0.12, middle breadth 0.016; +length of the caudal spine 0.14, middle breadth 0.024; length of the +eighteen smaller spines 0.04 to 0.06. + +_Habitat._--Mediterranean (Messina), surface. + + + +{790}Subgenus 2. _Amphibelithium_, Haeckel. + +_Definition._--All twenty spines grown together in the centre, forming a +single star-shaped piece of acanthin. + + +5. _Amphibelone clavaria_, n. sp. + +Two principal spines roundish, without edges and wings; the smaller frontal +spine elongate conical, the larger caudal spine two to four times as long, +cylindrical, in the distal part spindle-shaped or club-shaped, with conical +apex. Central base simple pyramidal, without leaf-cross. Eighteen smaller +spines much shorter, bristle-shaped. Central capsule very long, +club-shaped. All twenty spines perfectly grown together in the centre. + +_Dimensions._--Length of the frontal spine 0.12, of the caudal spine 0.4 to +0.8; frontal breadth 0.01, caudal breadth 0.03; length of the eighteen +smaller spines 0.05. + +_Habitat._--Central Pacific, Station 272, surface. + + + +Genus 343. _Acantholonche_,[383] Haeckel, 1881, Prodromus, p. 466. + +_Definition._--#Amphilonchida# with two equal principal spines (frontal and +caudal spines not different). The eighteen smaller spines are very unequal, +ten of them (eight tropical and two transverse equatorial spines) much +larger than the rudimentary eight polar spines. + +The genus _Acantholonche_ differs from its ancestral genus _Amphilonche_ in +the different shape of the eight tropical and the eight polar spines; these +latter are much smaller than the former, which are almost equal to the two +transverse equatorial spines. The two principal spines are equal, but in +size and shape very different from the others. + + +1. _Acantholonche amphipolaris_, n. sp. (Pl. 132, fig. 7). + +Two principal spines stout, quadrangular prismatic in the basal half, +cylindrical or spindle-shaped in the distal half, with simple conical apex; +base a small pyramid without leaf-cross. Two transverse and eight tropical +spines, about half as long as the former, very thin, bristle-shaped, +conical at the basal part. Eight polar spines very small, scarcely +one-eighth or one-fourth as long as the latter, short pyramidal or conical, +often quite rudimentary. Central capsule cylindrical, enveloping the basal +half of the two principal spines. + +_Dimensions._--Length of the two principal spines 0.4 to 0.5, of the ten +smaller spines 0.2 to 0.3, of the eight rudimentary polar spines 0.01 to +0.06; breadth of the two large spines 0.02 to 0.03. + +_Habitat._--Central Pacific, Stations 266 to 274, surface. + + +{791}2. _Acantholonche peripolaris_, n. sp. (Pl. 132, fig. 8). + +Two principal spines quadrangular prismatic, with four broad prominent +lamellar wings, of increasing breadth towards the pyramidal distal apex. +Both ends of each spine four-sided pyramidal, base without leaf-cross. Two +transverse and eight tropical spines about two-thirds as long as the +former, four-sided pyramidal in the basal half, conical in the distal half, +often curved. Eight polar spines very small, about one-fourth as long as +the latter, short conical or pyramidal. Central capsule four-sided +prismatic, enveloping both principal spines. + +_Dimensions._--Length of the two principal spines 0.2, of the ten smaller +spines 0.12, of the eight rudimentary polar spines 0.04. + +_Habitat._--Central Pacific, Station 274, surface. + + +---- + + +Order IV. ACANTHOPHRACTA, Richard Hertwig, 1879. + + _Acanthometrae cataphractae_, Johannes Mueller, 1858, Abhandl. d. k. + Akad. d. Wiss. Berlin, pp. 12, 22, 49. + _Dorataspida et Diploconida_, Haeckel, 1862, Monogr. d. Radiol., + pp. 404, 412. + _Acanthophractida_, Richard Hertwig, 1879, Organismus d. Radiol., + pp. 25, 137. + _Dorataspida, Diploconida, et Sphaerocapsida_, Haeckel, 1881, + Prodromus, p. 467. + +_Definition._--ACANTHARIA with complete latticed shell. + +The order #Acanthophracta#, the fourth order of Radiolaria, comprises all +those ACANTHARIA in which the acanthinic skeleton is a complete latticed or +fenestrated shell, supported by radial spines arising from one common +central point. By the possession of such a complete shell the +#Acanthophracta# differ from their ancestral group, the nearly allied +#Acanthometra#, which represent the older and simpler, first order of +ACANTHARIA. All #Acanthophracta# are Icosacantha (like the #Acanthonida#, +their ancestral group), and possess twenty radial spines disposed according +to the Muellerian law (compare above, p. 717). + +Johannes Mueller, who first observed five representatives of this order, +called a part of them "_Acanthometrae cataphractae_," and united these with +the true #Acanthometra# (_Acanthometra costata_ and _Acanthometra +cataphracta_; Abhandl. d. k. Akad. d. Wiss. Berlin, 1858, pp. 12, 49). +Another part was united by him with the true _Haliomma_ (_Haliomma +echinoides_, _Haliomma hystrix_, _Haliomma tabulatum_; Abhandl. d. k. Akad. +d. Wiss. Berlin, 1858, pp. 36, 37). He supposed that these latter formed +the immediate transition from the true #Acanthometra# to the true +_Haliomma_, and that their skeleton was siliceous. + +{792}In my Monograph (1862, p. 412) I founded a separate subfamily, +Dorataspida, for the "_Acanthometrae cataphractae,_" which I considered as +the first subfamily of the "Ommatida." That subfamily contained at that +time only two genera, _Dorataspis_ (with seven species) and +_Haliommatidium_ (with five species). A third genus, _Aspidomma_ (with two +species), was united by me with the Haliommatida (because of its double +shell). For a fourth genus (_Diploconus_) with a single species I founded +the peculiar family of Diploconida. Therefore the whole number of +#Acanthophracta# described in my Monograph amounted only to four genera and +fifteen species. Now the rich collections of the Challenger have added such +a great number of new forms, that we may distinguish here thirty-eight +genera and two hundred and twelve species. + +Richard Hertwig in his excellent work (Der Organismus der Radiolarien, +1879, p. 25) separated his "Acanthophractida" perfectly from the "Ommatida" +(or the siliceous #Sphaeroidea#), and united them with the "Acanthometrida" +in his order "Acanthometrea." But he separated them also from the nearly +allied Diploconida, following my former arrangement. He distinctly noted +that the skeleton in all these Acanthophractida (as well as in the +Acanthometrida) consists not of silex but of the organic substance +"acanthin." + +The astonishing number of new and interesting forms of #Acanthophracta# +which I have found in the rich collection of the Challenger enables me to +distinguish now in this suborder six different families, two of which are +perfectly new (the Sphaerocapsida and the Hexalaspida). But the four other +families also are so much enlarged that their interesting morphology +appears in quite a new and clear light. Far the largest and most important +of these six families is that of the true Dorataspida, which embraces +seventeen genera and one hundred and eight species (more than the other +five families together). From this largest and oldest ancestral family four +other families have afterwards arisen, whilst a single family, the +Sphaerocapsida, seems to possess no direct phylogenetic connection with the +five other families. + +The peculiar and quite new family of Sphaerocapsida (Pl. 133, figs. 7-11; +Pl. 135, figs. 6-10) differs from all other #Acanthophracta# in the +singular structure of the spherical acanthinic shell, composed of +innumerable small plates or aglets, each of which is pierced by a very +small porule. This peculiar pavemented shell (enclosing the central capsule +and separated from it by the jelly-like calymma) seems to be produced on +the surface of the spherical calymma, immediately by secretion of the +pseudopodia, and independently from the twenty radial spines, united in the +centre of the sphere. On the twenty points, where the spines perforate the +shell, there are originally eighty larger pores (four around each piercing +spine); but there is no certain indication that the shell is produced by +the meeting apophyses of the twenty spines, as is the case in the five +other families of #Acanthophracta#. Therefore perhaps it is {793}more +natural to unite these latter into another suborder as #Cladophracta#, and +to separate them from the Sphaerocapsida, which may be called +Capsophractae. + +The Dorataspida (Pls. 134-138), the common ancestral stock of the +#Cladophracta#, in the definition here restricted embraces all those +#Acanthophracta# in which the spherical lattice-shell is simple and +composed of the meeting branches of twenty radial spines united in its +centre. As already pointed out above, this family is probably diphyletic, +and embraces two subfamilies which have been derived originally from two +different forms of #Acanthonida#--the Diporaspida (with two opposite +apophyses on each spine) derived from the Phractacanthida, and the +Tessaraspida (with four crossed apophyses on each spine) derived from the +Stauracanthida; in the former we find originally forty apophyses, in the +latter eighty apophyses, by the meeting branches of which the spherical +lattice-shell originates. The four following families of #Acanthophracta# +have probably been derived from the Diporaspida. + +The Phractopeltida (Pl. 133, figs. 1-6) differ from all other +#Acanthophracta# in the possession of a double lattice-shell, composed of +two concentric spheres which are united by the twenty radial spines meeting +in the centre. As all Phractopeltida possess originally only two apophyses +on each radial spine, they must be derived from the Diporaspida +(_Orophaspis_), and bear to them the same relation as the Dyosphaerida do +to the Monosphaerida. As the spherical central capsule of the +Phractopeltida is enclosed between both shells, smaller than the outer, +larger than the inner shell, the latter may be called "medullary shell," +the former "cortical shell." This family represents among the +#Acanthophracta# only the "Diplophracta," whilst all others are +"Haplophracta." + +The three families here characterised may be called together +"#Sphaerophracta#," as their central capsule and the enveloping shell are +constantly spherical (or the shell sometimes an "endospherical +polyhedron"). On the contrary the following three families of +#Acanthophracta# may be united as "#Prunophracta#," as their central +capsule and shell are never spherical, but either ellipsoidal or lenticular +or of another form. The common ancestral stock of this suborder are the +Belonaspida, in which the form of the central capsule and the enclosing +lattice-shell is ellipsoidal; they are derived from the Dorataspida (and +probably all from the subfamily Diporaspida) by the prolongation of two +opposite radial spines which are larger than the eighteen others; they are +the two equatorial spines of the "hydrotomical axis" (compare above, p. +719, and Pl. 136, figs. 6-9). + +The Hexalaspida (Pl. 139) represent a new and very remarkable family, +distinguished from all other #Acanthophracta# by the preponderating +development of six stout radial spines, which are much larger than the +fourteen others. These six principal spines lie in one meridian plane of +the shell (in the "hydrotomical plane," p. 720), and are the two opposite +equatorial spines and the four appertaining polar spines of the same plane. +{794}As the fourteen smaller spines develop their apophyses at smaller +distances from the centre, the shell assumes a peculiar lenticular or +discoidal form, and the margin of this disk bears the six larger spines. +Moreover the enclosed small central capsule is lenticular. The Hexalaspida +may be derived immediately from the Belonaspida. + +The Diploconida (Pl. 140) form the last and the most modified family of all +#Acanthophracta#. The remarkable shell exhibits the strange form of a +double cone, bearing in its axis two very large opposite spines; these are +the two equatorial spines of the "hydrotomical axis" (p. 719). The +double-conical or nearly cylindrical shell is composed of three different +parts or segments; the small middle part is the true lattice-shell of the +Hexalaspida and Belonaspida, and bears the eighteen smaller (often quite +rudimentary) radial spines. The two other parts (opposite on both poles of +its hydrotomical axis) are the conical or cylindrical, solid, basal sheaths +of the two large equatorial spines, enveloping their major part. In +consequence of this peculiar metamorphosis of the shell the Diploconida +represent the last and the most aberrant group of all ACANTHARIA. + +_Synopsis of the Suborders and Families of_ #Acanthophracta#. + + ------------------------------------------------------------------------- + Suborder I. SPHAEROPHRACTA. + Twenty radial spines of equal size. Shell spherical (or an + endospherical polyhedron). + ------------------------------------------------------------------------- + Shell spherical, simple, pierced by twenty or + eighty aspinal pores and composed of a + pavement of innumerable very small plates + or aglets, each pierced by one porule, 1. SPHAEROCAPSIDA. + + Shell spherical, simple, composed of the + meeting branches of two or four apophyses + of the twenty radial spines, 2. DORATASPIDA. + + Shell spherical, double, composed of two + concentric lattice-spheres, which are connected + by the twenty radial spines and composed + of the meeting branches of their apophyses, 3. PHRACTOPELTIDA. + ------------------------------------------------------------------------- + Suborder II. PRUNOPHRACTA. + Twenty radial spines of unequal size; two or six hydrotomical spines + much larger than the eighteen or fourteen others. Shell not spherical. + ------------------------------------------------------------------------- + Shell ellipsoidal, with prolonged hydrotomical + axis, the two spines of which are larger + than the eighteen others, 4. BELONASPIDA. + + Shell lenticular or discoidal, with six larger + spines placed in the hydrotomical plane + (fourteen other spines much smaller), 5. HEXALASPIDA. + + Shell diploconical or nearly cylindrical, with + two opposite large funnels, the sheaths of + the enlarged two spines of the hydrotomical + axis (eighteen other spines much + smaller or rudimentary), 6. DIPLOCONIDA. + + +{795}---- + + +Suborder I. SPHAEROPHRACTA, Haeckel. + +_Definition._--Shell spherical, with twenty radial beams of equal size. + + + +Family XXXIX. #SPHAEROCAPSIDA#, Haeckel (Pl. 133, figs. 7-11; Pl. 135, +figs. 6-10). + +_Sphaerocapsida_, Haeckel, 1881, Prodromus, p. 469. + +_Definition._--ACANTHARIA with simple spherical porous shell, composed of +innumerable very small plates, each of which is pierced by one radial +porule. Twenty radial spines of equal size meeting in the centre of the +shell and disposed according to the Muellerian law of the Icosacantha, +sometimes short and enclosed in the shell, at other times long and piercing +it (rarely rudimentary or quite absent). Shell pierced therefore either by +twenty larger perspinal pores or by eighty smaller aspinal pores. Central +capsule spherical, enclosed in the porous shell. + +The family #Sphaerocapsida#, founded by me in 1881 for the single genus +_Sphaerocapsa_, represents a very peculiar and remarkable group of the +#Acanthophracta#, very different from the five other families of this +suborder, and probably derived, independently of them, directly from the +#Acanthonida#. Whilst the lattice-shell of the five other families is +composed of the meeting branches of lateral apophyses of the twenty spines, +and its meshes are all or partly the intervals between these apophyses, in +the Sphaerocapsida the spherical shell has quite another structure, and is +composed of innumerable small plates (each with one pore) which are +secreted on the surface of the spherical calymma, independently of the +twenty radial spines, which do not possess true apophyses. + +In all Sphaerocapsida the structure of the spherical shell is quite +peculiar and different from that of all other Radiolaria. It is composed +everywhere of innumerable very small plates or aglets, which are connected +irregularly like paving-stones, and form a single continuous layer or +pavement on the surface of the spherical calymma (Pl. 133, fig. 11, _a_; +Pl. 135, figs. 8, 10). The small plates or paving-stones, which we will +call "aglets," are connected at their meeting edges by a kind of cement, +and form together with it a continuous thick capsule of acanthin. The form +of the aglets is commonly more or less irregular, roundish or polygonal, +sometimes longish (Pl. 133, fig. 11, _a_), more rarely it becomes rather +regular, hexagonal, square, or roundish (Pl. 135, fig. 8). Usually all +aglets of one and the same individual are of nearly equal size, between +0.01 and 0.02 in diameter, rarely less or more. The outer face of the +aglets is more or less concave, so that the elevated meeting edges of the +neighbouring aglets commonly form together a prominent network of crests +(Pl. 135, figs. 8, 10); rarely the meeting edges partly cover one another +like squamules (Pl. 133, fig. 11, _a_). {796}Each small plate or aglet is +pierced in its centre by a single radial canalicule or porule. The dimpled +surface, so produced, resembles somewhat the dimpled plates of _Ceriaspis_, +&c. Different from these innumerable very small dimples of the surface are +the twenty larger "spinal dimples," or the concave larger plates, which are +originally pierced by the twenty radial spines. Before we describe these, +we must examine the spines themselves. + +The twenty radial spines of all observed Sphaerocapsida (sixteen species) +agree perfectly with those of the genus _Acanthonia_ (p. 749), and +especially with _Acanthonia tetracopa_, _Acanthonia denticulata_, &c. All +twenty spines, regularly disposed according to the Muellerian law of the +Icosacantha, are of equal size, constantly four-edged prismatic, of equal +breadth throughout their whole length. The prominent four edges are +parallel, sometimes smooth, at other times elegantly denticulated. The +central bases of the twenty spines are pyramidal, without leaf-cross, and +propped one upon another with their triangular faces, as in the majority of +the #Acanthonida#. + +The relation of the twenty radial spines to the spherical shell exhibits in +the five genera described very peculiar and important differences. In the +first described genus, in _Sphaerocapsa_, the spines are exactly as long as +the shell-radius, and therefore are not prominent over the surface of the +shell, with which they are firmly connected; the truncated distal end of +the spine lies therefore here in the surface of the shell itself, and is +connected with it by its four edges, between which four open aspinal pores +remain, as in _Tessaraspis_, &c. (Pl. 135, figs. 6-10). In the next allied +genus, _Astrocapsa_ (Pl. 133, figs. 9, 10), the spines are longer than the +shell-radius, and therefore more or less prominent over its surface; the +piercing part of each spine is also surrounded by four aspinal pores. In +the two following genera, _Porocapsa_ and _Cannocapsa_ (Pl. 133, figs. 7, +8), the radial spines are shorter than the shell-radius and therefore quite +hidden and withdrawn inside the shell, which they do not reach. But in the +ideal prolongation of each spine the shell is pierced by a single large +opening, the "perspinal pore" or "perspinal hole," composed of the four +united aspinal pores. Whilst in _Porocapsa_ the perspinal pores are simple, +they are prolonged in _Cannocapsa_ into cylindrical tubes, open at both +ends. The twenty perspinal holes of these Porocapsida are therefore derived +by confluence of the eighty original aspinal pores of the Astrocapsida and +preserve the same regular disposition, according to the Muellerian law of +the Icosacantha. Finally, the same law as is valid also in the last genus +is found in _Cenocapsa_; here the radial spines have completely +disappeared, and the whole skeleton is a simple sphere, but of the same +structure, and with the same twenty perspinal pores as in _Porocapsa_. It +is very interesting that this spineless _Cenocapsa_ among the ACANTHARIA +exhibits the same shell (a simple hollow sphere) as a last reduced form, +which _Cenosphaera_ among the #Sphaerellaria# produces as a primitive +ancestral form of numerous genera. + +{797}_The Central Capsule_ of the Sphaerocapsida is spherical, constantly +smaller than the enclosing concentric shell, and separated from it by the +calymma. Its structure seems to be the same as in the #Acanthonida#, and +specially in the Astrolonchida. The pseudopodia (not yet observed) are +probably protruded only through the twenty perspinal holes or the eighty +aspinal pores. + +_Synopsis of the Genera of Sphaerocapsida._ + + ------------------------------------------------------------------------- + I. Subfamily Astrocapsida. + Radial spines connected with the porous shell, as long or longer than + its radius. Eighty aspinal pores. + ------------------------------------------------------------------------- + Spines as long as the radius, + without external prolongation, 344. _Sphaerocapsa_. + + Spines longer than the radius, + with external prolongation, 345. _Astrocapsa_. + ------------------------------------------------------------------------- + II. Subfamily Porocapsida. + Radial spines not connected with the porous shell, shorter than its + radius. Twenty perspinal pores. + ------------------------------------------------------------------------- + Perspinal holes of the shell + simple, without external + prolongation, 346. _Porocapsa_. + + Perspinal holes of the shell + prolonged into radial + centrifugal tubuli, 347. _Cannocapsa_. + ------------------------------------------------------------------------- + III. Subfamily Cenocapsida. + Radial spines disappeared. + ------------------------------------------------------------------------- + Twenty perspinal holes of the + shell simple, without tubular + prolongation, 348. _Cenocapsa_. + + + +Subfamily 1. ASTROCAPSIDA, Haeckel. + +_Definition._--Radial spines connected with the porous shell, as long as or +longer than its radius. Therefore the shell pierced by eighty aspinal pores +(four around each spine). + + + +Genus 344. _Sphaerocapsa_,[384] Haeckel, 1881, Prodromus, p. 469. + +_Definition._--#Sphaerocapsida# with twenty radial spines as long as the +radius of the shell, without external prolongation; therefore their distal +ends inserted in the perspinal holes, each of which is composed of four +aspinal pores. + +The genus _Sphaerocapsa_ is the most common form of the Sphaerocapsida, and +comprises those species in which the radial spines are as long as the +radius of the shell, and therefore are connected with the margin of its +aspinal holes, but not prolonged beyond its surface. + + +{798}1. _Sphaerocapsa cruciata_, n. sp. (Pl. 135, figs. 6, 7). + +Aspinal holes nearly circular, with flat radially striated margin. Four +aspinal pores of each hole rounded equilateral triangular. Porules of the +shell simple, without ring and dimple. Four edges of the spines smooth. + +_Dimensions._--Diameter of the shell 0.4 to 0.5, of the central capsule 0.3 +to 0.4. + +_Habitat._--North Atlantic, Faeroee Channel (Gulf Stream), 1880, John +Murray, surface. + + +2. _Sphaerocapsa dentata_, n. sp. (Pl. 135, fig. 9). + +Aspinal holes four-lobed, with broad concave margin denticulated on the +periphery. Four aspinal pores of each hole pear-shaped, oblong, elevated in +the centre. Porules of the shell simple, without ring and dimple. Four +edges of the spines denticulate. + +_Dimensions._--Diameter of the shell 0.3 to 0.4, of the central capsule 0.2 +to 0.3. + +_Habitat._--South Atlantic, Station 332, depth 2200 fathoms. + + +3. _Sphaerocapsa quadrata_, n. sp. (Pl. 135, fig. 8). + +Aspinal holes square, with concave umbilicus in the centre, surrounded by a +convex denticulated margin. Four aspinal pores of each hole nearly square. +Shell-porules with a polygonal elevated smooth ring, in the bottom of a +shallow dimple. Four edges of the spines smooth. + +_Dimensions._--Diameter of the shell 0.22, of the central capsule 0.17. + +_Habitat._--Indian Ocean, south of Australia, Station 159, surface. + + +4. _Sphaerocapsa pavimentata_, n. sp. (Pl. 135, fig. 10). + +Aspinal holes four-lobed, with broad concave, irregularly crenated and +figured margin. Four aspinal pores of each hole violin-shaped. Porules of +the shell surrounded by an irregularly oblong ring with thick elevated, +elegantly crenated margin. Four edges of the spines smooth. + +_Dimensions._--Diameter of the shell 0.36, of the central capsule 0.3. + +_Habitat._--South-east Pacific (off Valparaiso), Station 298, surface. + + + +Genus 345. _Astrocapsa_,[385] n. gen. + +_Definition._--#Sphaerocapsida# with twenty radial spines longer than the +radius of the shell, piercing its perspinal holes, with free external +prolongation; therefore with four aspinal pores around each spine. + +The genus _Astrocapsa_ differs from the preceding _Sphaerocapsa_ in the +external prolongation of the radial spines piercing the perspinal holes; it +assumes therefore the common shape of the Dorataspida more than the other +Sphaerocapsida do. + + +{799}1. _Astrocapsa tritonis_, n. sp. + +Aspinal holes circular, with smooth convex margin and four circular aspinal +pores. Porules of the shell simple, without ring and dimple. Four edges of +the spines smooth, their outer free part about as long as the diameter of +the shell. + +_Dimensions._--Diameter of the shell 0.25; outer length of the spines 0.3. + +_Habitat._--North Atlantic, Faeroee Channel, Gulf Stream (expedition of +H.M.S "Triton," August, 1882), John Murray, surface. + + +2. _Astrocapsa stellata_, n. sp. (Pl. 133, fig. 10). + +Aspinal holes cruciform, with high crenated margin. Four aspinal pores of +each hole egg-shaped. Porules of the shell simple, without ring and dimple. +Four edges of the spines denticulate; their outer free part twice to three +times as long as the diameter of the shell. + +_Dimensions._--Diameter of the shell 0.36; outer length of the spines 0.5 +to 0.8. + +_Habitat._--Antarctic Ocean (near Kerguelen), Station 152, surface. + + +3. _Astrocapsa quadrifida_, n. sp. + +Aspinal holes four-lobed, with four prominent teeth between the four +roundish aspinal pores. Porules of the shell surrounded by a high polygonal +smooth ring. Four edges of the spines denticulate; their outer free part +about as long as the radius of the shell. + +_Dimensions._--Diameter of the shell 0.28; outer length of the spines 0.15. + +_Habitat._--North Pacific, Station 241, surface. + + +4. _Astrocapsa coronata_, n. sp. (Pl. 133, fig. 9). + +Aspinal holes circular, with a coronet of numerous thin parallel teeth. +Porules of the shell in dimples on irregular polygonal small plates, with +coronated ring. Four edges of the spines denticulate; their outer free part +about twice as long as the diameter of the shell. + +_Dimensions._--Diameter of the shell 0.4 to 0.5 ; outer length of the +spines 1.0 to 1.2. + +_Habitat._--North Atlantic, Faeroee Channel, Gulf Stream (expedition of the +"Knight Errant," 1880), John Murray, surface and at depths varying from 10 +to 200 fathoms. + + + +Subfamily 2. POROCAPSIDA, Haeckel. + +_Definition._--Radial spines not connected with the porous shell, shorter +than its radius; therefore the shell pierced by twenty perspinal pores +(each one in the ideal radial prolongation of one spine). + + + +{800}Genus 346. _Porocapsa_,[386] n. gen. + +_Definition._--#Sphaerocapsida# with twenty radial spines shorter than the +radius of the shell; therefore their distal ends not connected with the +twenty perspinal holes, which are simple, not prolonged into radial tubes. + +The genus _Porocapsa_ and the following _Cannocapsa_ form together the +small sub-family of Porocapsida, distinguished by the peculiar reduction or +retrograde development of the twenty radial spines; all these twenty are +present and disposed according to the Muellerian law of the Icosacantha, +but they are shorter than the radius of the shell and therefore do not +reach it. In the ideal prolongation of the spines the shell is pierced by +twenty simple quadrangular or circular perspinal holes. + + +1. _Porocapsa murrayana_, n. sp. (Pl. 133, fig. 7). + +Perspinal holes cruciform, with smooth thickened margin or with four short +teeth between the four lobes. Porules of the shell simple, without ring and +dimple. Four edges of the spines smooth. (Differs from _Sphaerocapsa +cruciata_, Pl. 135, figs. 6, 7, living in the same locality, mainly in the +reduction of the radial spines, which do not reach the shell.) + +_Dimensions._--Diameter of the shell 0.28; length of the spines 0.2. + +_Habitat._--North Atlantic, Faeroee Channel, Gulf Stream (expedition of +H.M.S. "Triton," August 1882), John Murray, surface and in depths from 40 +to 640 fathoms. + + +2. _Porocapsa tetrodon_, n. sp. + +Perspinal holes cruciform, with four triangular prominent teeth between the +four lobes of the cross. Porules of the shell with an elevated polygonal +ring, in the bottom of a dimple. Four edges of the spines elegantly +denticulate. + +_Dimensions._--Diameter of the shell 0.36; length of the spines 0.12. + +_Habitat._--North Pacific, Station 253, surface. + + +3. _Porocapsa octodon_, n. sp. + +Perspinal holes square, with four larger prominent teeth on the sides of +the square, and four smaller teeth on its corners. Porules of the shell +surrounded by an elevated ring with elegantly crenated irregular margin. +Four edges of the spines smooth. + +_Dimensions._--Diameter of the shell 0.48; length of the spines 0.18. + +_Habitat._--Arctic Ocean (Greenland), in the contents of the stomach of the +Peromedusa, _Periphylla hyacinthina_. + + +{801}4. _Porocapsa coronodon_, n. sp. + +Perspinal holes circular, with ciliated margin, which forms a crown of +sixteen to twenty-four thin parallel teeth. Poruli of the shell surrounded +by an elevated ring with high crenated margin. Four edges of the spines +denticulate. + +_Dimensions._--Diameter of the shell 0.55; length of the spines 0.15. + +_Habitat._--Antarctic Ocean, Station 154, surface. + + + +Genus 347. _Cannocapsa_,[387] n. gen. + +_Definition._--#Sphaerocapsida# with twenty radial spines shorter than the +radius of the shell; therefore their distal ends not connected with the +twenty perspinal holes, which are prolonged outside into radial tubes (each +one in the radial ideal prolongation of one inner spine). + +The genus _Cannocapsa_, exhibits the same peculiar reduction of the radial +spines as the foregoing _Porocapsa_; the spines are also here shorter than +the shell-radius and do not therefore reach the perspinal holes of the +shell. But whilst these latter are simple in _Porocapsa_, they are +prolonged into radial tubules in _Cannocapsa_; the outer surface bears +therefore twenty such cylindrical tubules, separated by a short distance +from the inner enclosed spines, but disposed quite regularly according to +the law of Icosacantha. + + +1. _Cannocapsa osculata_, n. sp. + +Perspinal holes prolonged into short cylindrical tubuli, the length of +which about equals their diameter. Both ends of the tubuli with smooth +thickened margin. Poruli of the shell simple, without ring and dimple. Four +edges of the spines smooth; their length equals about four-fifths of the +shell-radius. + +_Dimensions._--Diameter of the shell 0.24; length of the spines 0.09, of +the tubuli 0.01. + +_Habitat._--North Atlantic, Faeroee Channel (Gulf Stream), surface, John +Murray. + + +2. _Cannocapsa stethoscopium_, n. sp. (Pl. 133, fig. 8). + +Perspinal holes prolonged into cylindrical tubuli, half as long as the +shell radius. Both ends of the tubuli with smooth thin trumpet-shaped +margins. Poruli of the shell simple, without ring and dimple. Four edges of +the spines smooth; their length about equals three-fourths of the +shell-radius. + +_Dimensions._--Diameter of the shell 0.2; length of the spines 0.08, of the +tubuli 0.05. + +_Habitat._--South Atlantic (west of Tristan da Cunha), Station 333, +surface. + + +3. _Cannocapsa tubulosa_, n. sp. + +Perspinal holes prolonged into cylindrical tubuli, which are as long as or +longer then the shell-radius. Both ends of the tubuli with smooth thickened +margin. Poruli of the shell simple, {802}without ring and dimple. Four +edges of the spines smooth; their length scarcely equals half the +shell-radius. + +_Dimensions._--Diameter of the shell 0.15; length of the spines 0.03, of +the tubuli 0.08. + +_Habitat._--South Atlantic (east coast of Patagonia), Station 318, surface. + + + +Subfamily 3. CENOCAPSIDA, Haeckel. + +_Definition._--Radial spines completely reduced and absent; shell cavity +therefore simple; shell pierced by twenty perspinal pores (each placed in +the direction of one radial spine which has disappeared). + + + +Genus 348. _Cenocapsa_,[388] n. gen. + +_Definition._--#Sphaerocapsida# without radial spines, with simple cavity +of the spherical shell, which is pierced by twenty perspinal holes (each +one placed in the radial direction of one spine which has disappeared). + +The genus _Cenocapsa_ comprises only a single species, but is very +remarkable in that it is the most reduced form among all Sphaerocapsida. +The twenty radial spines of the Icosacantha have perfectly disappeared by +complete retrograde metamorphosis, and the only evidence of their former +existence (in the ancestral genus _Porocapsa_) are the twenty perspinal +holes remaining in the shell. _Cenocapsa_ is the only form of ACANTHARIA +which possesses no radial spines. + + +1. _Cenocapsa nirvana_, n. sp. (133, fig. 11, 11_a_, 11_c_). + +Perspinal holes four-lobed, cruciform, with four short triangular teeth +between the four lobes of the cross. Poruli of the shell in the bottom of +an elliptical dimple surrounded by an elevated ring. + +_Dimensions._--Diameter of the shell 0.2 to 0.3, of the aspinal holes 0.02. + +_Habitat._--North Pacific, Station 248, surface. + + + +Family XL. #DORATASPIDA#, Haeckel (Pls. 134-138). + +_Dorataspida_, Haeckel, 1862, Monogr. d. Radiol., p. 412. + +_Definition._--ACANTHARIA with simple spherical lattice-shell, composed of +the branched apophyses of twenty equal radial spines meeting in its centre +and disposed according to the Muellerian law of Icosacantha. Central +capsule spherical, enclosed in the fenestrated shell. + +The family #Dorataspida# is the most important family of the +#Acanthophracta#, or of those ACANTHARIA in which the radial spines are +connected by a complete extracapsular lattice-shell. The Dorataspida +represent probably the ancestral {803}stock of this whole order, with the +exception of the Sphaerocapsida. The four following families of the order +may be easily derived from the Dorataspida. The number of genera +(seventeen) and of species (one hundred and eight) is in this family +greater than in the other five families together. When I constituted that +family in my Monograph 1862, it comprised only one genus, _Dorataspis_, +with seven species. The nearly allied genus _Haliommatidium_ (_Phatnaspis_) +belongs to the Belonaspida. + +The Dorataspida differ from the other #Acanthophracta# in the simple +spherical lattice-shell, which is composed of the meeting apophyses of the +twenty radial spines. In three other families of the suborder the shell is +not spherical, but ellipsoidal (Belonaspida), discoidal (Hexalaspida), or +diploconical (Diploconida). In the Phractopeltida the spherical shell is +double, composed of two concentric lattice-spheres. In the Sphaerocapsida +the simple spherical shell is not composed of the apophyses of the spines, +but of innumerable small plates. + +The family Dorataspida may be divided into two very different subfamilies, +which are probably derived, independently of one another, from two +different subfamilies of the Astrolonchida. The first subfamily, +Diporaspida, exhibits on each radial spine two opposite apophyses, like its +ancestral group, the Phractacanthida (p. 753); whereas the second +subfamily, Tessaraspida, possesses on each radial spine four crossed +apophyses (opposite in pairs), like its ancestral group, the Stauracanthida +(p. 758). Therefore the composition of the spherical shell, produced by the +meeting branches of the tangential apophyses, is essentially different in +the two subfamilies: in the Diporaspida each radial spine is surrounded by +two opposite primary aspinal meshes, in the Tessaraspida by four crossed +primary aspinal meshes. + +Another principle of division may be established for the whole family by +the different mode of composition of the shell, and regarding this +important difference we may distinguish also two different subfamilies as +#Cladophracta# and #Peltophracta#. In the first and simpler subfamily, the +#Cladophracta#, the shell is composed totally (or sometimes partially) of +the meeting branches of the apophyses of the neighbouring spines; but in +each single spine (or in the most part of them) the branches of the +apophyses are not united, and form no lattice-plate (Pl. 137, figs. 1 to +8). Whereas in the #Peltophracta# the shell is composed constantly of +twenty perforated plates, as in each single spine the branches of its +apophyses are united and form a fenestrated shield with two or four (and +sometimes numerous) pores (Pls. 135, 136, 138). + +In the Diporaspida as well as in the Tessaraspida we find numerous +representatives of the two groups of the #Cladophracta# and of the +#Peltophracta#; therefore the whole family of Dorataspida may be divided +into four different tribes. The Diporaspida (with two opposite apophyses on +each spine) are partly #Cladophracta# (the Phractaspida, Pl. 137, figs. +1-4), partly #Peltophracta# (the Ceriaspida, Pl. 138). On the other hand +the Tessaraspida (with four crossed apophyses on each {804}spine) are also +partly #Cladophracta# (the Stauraspida, Pl. 137, figs. 5-8), partly +#Peltophracta# (the Lychnaspida, Pls. 135-136). The differences and +relations of these tribes are placed synoptically in the following table:-- + + ------------------------+------------------------+----------------------- + | A. Diporaspida. | B. Tessaraspida. + Synopsis of the four |Two opposite apophyses |Four crossed apophyses + tribes of Dorataspida.| on each radial spine. | on each radial spine. + | Two primary aspinal | Four primary spinal + | meshes. | meshes. + ------------------------+------------------------+----------------------- + a. Cladophracta |1. Tribe Phractaspida. |3. Tribe Stauraspida. + All twenty spines (or a | | + part of them) without | | + lattice-plates. | | + | | + b. Peltophracta |2. Tribe Ceriaspida. |4. Tribe Lychnaspida. + All twenty spines with | | + lattice-plates. | | + ------------------------+------------------------+----------------------- + +All Dorataspida are true Icosacantha, and the twenty spines, composing the +spherical shell, are equally developed, regularly disposed according to the +Muellerian law, and of equal size; also the distance of their plates from +the common centre is equal. Nevertheless they are never of perfectly the +same form; in consequence of their peculiar disposition in five zones (each +with four spines) certain slight differences are effected, so that with +accurate knowledge of the peculiar shell-composition it is generally not +difficult to distinguish the spines of the equatorial, the two tropical, +and the two polar zones. + +Already the central bases, by which the twenty spines are united in the +centre of the sphere, exhibit certain differences in the five zones. +Commonly these bases are small pyramids, all meeting with their apex in the +centre, and the triangular faces of the neighbouring pyramids are supported +one upon another. The four equatorial pyramids are commonly six-sided, the +other sixteen five-sided; but sometimes there are eight six-sided and +twelve five-sided basal pyramids; two opposite polar spines on each pole +having a six-sided base (like the four equatorial), the other two polar +spines on each pole having a five-sided base (like the eight tropical). +Rarely the central bases are perfectly grown together, forming a single +spherical central piece of acanthin. + +The three different fundamental forms of radial spines, which are found in +all ACANTHARIA, the cylindrical, the two-edged, and the four-edged (spines +with circular, with elliptical, and with square transverse section +respectively) occur also in the different groups of Dorataspida; but +commonly the two-edged or compressed form is prevalent in the Diporaspida, +the four-edged or quadrangular form in the Tessaraspida. In the majority of +species the spines are thickened in the shell-face, where the apophyses +arise, and thinner towards the two ends. Usually the outer or distal part +of the spine (outside the shell) is longer than the inner or proximal part +(inside {805}the shell). The distal apex is commonly simple, conical or +pyramidal, rarely bifid or truncate. The edges of the spines are commonly +smooth, rarely denticulate or serrate. + +The apophyses, or the lateral transverse processes of the radial spines, in +the Dorataspida assume the greatest variety and complexity in form, size, +mode of ramification, and in composition of the shell. An expert and +practised observer may determine easily the range of each spine, whether it +be an equatorial (_c_), or a tropical (_b_, _d_), or a polar spine (_a_, +_e_, Pls. 133-138). The two opposite apophyses of the Diporaspida, as well +as the four crossed apophyses of the Tessaraspida, lie constantly in +certain meridian planes of the spine, which have a legitimate signification +for each of the five zones. The comparative morphology of this regular +disposition of the apophyses and the regular meeting of their branches is +of the greatest interest, and necessary for the complete understanding of +the complicated structure of these wonderful shells. + +The pores or meshes of the spherical shell, offering the most varied forms, +may generally be divided into two different groups, into sutural and parmal +meshes. The sutural pores are bordered by the meeting branches of the +apophyses of two, three, or four neighbouring spines, and therefore also by +the sutures in which they meet. The parmal pores on the other hand are +bordered only by the united branches of the apophyses of a single spine and +pierce the shield or lattice-plate formed by them. Therefore the +shell-meshes of the #Cladophracta# are all sutural pores (Pl. 137, figs. +1-8; rarely and only in a part of the spines parmal pores also: _Zonaspis_, +_Dodecaspis_); whereas the shell-meshes of the #Peltophracta#, piercing the +shields or lattice-plates of all twenty spines, are always partly sutural, +partly parmal pores (Pls. 135, 136, 138). The parmal pores again may be +divided into two different groups--aspinal and coronal pores. Aspinal pores +("ad spinam") are those which lie immediately on the sides of the radial +spine and are bordered by the primary branches of its apophyses; therefore +constantly only two in the Diporaspida, four in the Tessaraspida. Coronal +pores on the contrary are those which lie in the periphery of the +lattice-plates, surrounding in a circle or crown the aspinal pores and not +touching the spine itself. In _Dorataspis_, _Ceriaspis_, _Tessaraspis_, +_Lychnaspis_, &c., all parmal meshes are only aspinal pores (Pl. 135, figs. +2-5; Pl. 136); whilst in _Coscinaspis_, _Acontaspis_, _Icosaspis_, +_Hylaspis_, &c., one part of the parmal pores is aspinal, one part coronal +(Pl. 136). The number, form, and size of the coronal pores is very variable +and often very large (sometimes more than a hundred in one plate). + +The #Cladophracta# exhibit a comparatively simple shell-formation; either +all twenty spines or at least a part of them not forming lattice-plates. +The most primitive form among these is _Phractaspis_ (Pl. 137, figs. 1, 2). +The forty apophyses of its twenty spines are simply forked, and their +eighty fork-branches united by forty sutures, enclosing twenty-two sutural +meshes: two square polar meshes (between the four polar spines on the poles +of the spineless axis, _a a a a_ and _e e e e_); eight triangular +{806}circumpolar meshes (each between two polar and one tropical spine, _a +b a_ and _e d e_); eight quadrangular tropical meshes (each between one +polar, one equatorial, and two tropical spines, _a b c b_ and _e d c d_); +and four rhomboidal equatorial meshes (between two tropical and two +equatorial spines, _c b c d_). If the fork-branches be again forked +(_Phractaspidium_, Pl. 137, fig. 3), the number of the sutures and sutural +meshes is doubled, and the same is the case in _Stauraspis_, the most +simple form of the Tessaraspida. + +A peculiar small group, and an interesting transition for the +#Cladophracta# to the #Peltophracta#, is presented by the Zonaspida among +the Tessaraspida (_Zonaspis_ and _Dodecaspis_). Here only one part of the +radial spines bears lattice-plates, the other part not. In _Zonaspis_ the +four equatorial spines bear lattice-plates, the sixteen other only free +branches of the apophyses. In _Dodecaspis_ twelve spines are provided with +lattice-plates (four equatorial and eight polar spines), whilst the eight +other (tropical) spines are devoid of them. + +The #Peltophracta# exhibit a great variety in the form and composition of +their twenty lattice-plates or fenestrated shields. In the most simple case +(a part of _Dorataspis_ and _Diporaspis_) the shell is composed of four +(equatorial) hexagonal plates, and sixteen pentagonal plates (four tropical +and four polar); in this case the four polar plates meet on each pole in +one common point. More commonly, however, the shell seems to be composed of +eight hexagonal plates (four equatorial and the four polar spines of the +hydrotomical plane) and twelve pentagonal plates (eight tropical and the +four polar spines of the geotomical plane); in this case only two +(hexagonal) polar plates meet on each pole in a suture which separates the +two other (pentagonal) polar plates (Pl. 138, fig. 4). In the majority of +the Dorataspida the composition of the shell is much more complicated and +often very difficult to understand. Often the surface of the plates is +covered with a network of elevated crests, by which concave blind dimples +are separated (_Ceriaspis_, _Hystrichaspis_, Pl. 138); and sometimes these +dimples become pierced by coronal pores (Pl. 138, fig. 11, &c.). + +Peculiar by-spines or "accessory spines" cover the outer surface of the +shell in a great part of Dorataspida, and commonly these most +characteristic by-spines are not placed radially, but parallel to the +radial spine, from the lattice-plate of which they arise (Pl. 135, figs. 1, +5; Pl. 137, figs. 4-8; Monogr. d. Radiol., 1862, Taf. xxi. figs. 8, 9). +They are commonly placed perpendicular to the sutural condyles, or the +branch-ends of the apophyses; so that close to each suture arises a pair of +divergent by-spines, belonging to the meeting apophyses of the two +neighbouring spines, which meet in the suture (Pl. 137, fig. 4). Rarely +these thin, bristle-shaped by-spines are quite simple and straight, +commonly they undulate or are zigzag and often armed with recurved hooks. +Sometimes they are also forked or arborescent (Pl. 138, fig. 7). + +_The Central Capsule_ of the Dorataspida is constantly spherical and about +one-third smaller than the enclosing shell, from which it is separated by +the spherical calymma. {807}The membrane of the central capsule is commonly +rather thin, and pierced by the twenty radial spines, meeting in the centre +of the capsule. Between these lie innumerable small pores for the radiating +pseudopodia; however, in many cases (and perhaps constantly) these pores +exhibit a certain regular disposition. In many species the central capsule +encloses Xanthellae or symbiotic yellow unicellular Algae. The nucleus +becomes cleft very early in the majority of Dorataspida. + +_Synopsis of the Genera of Dorataspida._ + + ------------------------------------------------------------------------- + I. Subfamily Diporaspida. + Each radial spine with two opposite primary apophyses; therefore the + whole shell with forty primary apophyses. + -------------------- + I. Tribe Phractaspida. + Twenty radial spines without lattice-plates; no normal pores. + ------------------------------------------------------------------------- + No by-spines, 349. _Phractaspis_. + + With by-spines, 350. _Pleuraspis_. + ------------------------------------------------------------------------- + II. Tribe Ceriaspida. + Twenty radial spines all with lattice-plates produced by union of the + branched apophyses of each plate. + ------------------------------------------------------------------------- + { { No by-spines, 351. _Dorataspis_. + { Plates not { + Forty parmal { dimpled, { With by-spines, 352. _Diporaspis_. + pores (two { without { + in each { network { No by-spines, but + plate)--no { of crests. { free apophyses, 353. _Orophaspis_. + coronal { + pores in { Plates dimpled, } No by-spines, 354. _Ceriaspis_. + the plates. { with a network } + { of crests. } With by-spines, 355. _Hystrichaspis_. + + Eighty to two hundred or more } No by-spines, 356. _Coscinaspis_. + (in each plate two aspinal } + and two to ten or more } With by-spines, 357. _Acontaspis_. + coronal pores). } + ------------------------------------------------------------------------- + II. Subfamily Tessaraspida. + Each radial spine with four crossed primary apophyses; therefore the + whole shell with eighty primary apophyses. + -------------------- + III. Tribe Stauraspida. + Twenty radial spines all or partly without lattice-plates. + ------------------------------------------------------------------------- + { No by-spines, 358. _Stauraspis_. + All twenty spines without { + lattice-plates. { With by-spines, 359. _Echinaspis_. + + Four plates with, sixteen } + without, lattice-plates. } With by-spines, 360. _Zonaspis_. + + Twelve plates with, eight } + without, lattice-plates. } With by-spines, 361. _Dodecaspis_. + ------------------------------------------------------------------------- + IV. Tribe Lychnaspida. + Twenty radial spines all with lattice-plates (produced by union of + the branched apophyses of each plate). + ------------------------------------------------------------------------- + Eighty parmal pores (four } No by-spines, 362. _Tessaraspis_. + on each plate)--no coronal } + pores in the plates. } With by-spines, 363. _Lychnaspis_. + + One hundred and sixty to three } + hundred or more parmal pores } No by-spines, 364. _Icosaspis_. + (in each plate four aspinal } + and four to twelve or more } With by-spines, 365. _Hylaspis_. + coronal pores). } + + + +{808}Subfamily 1. DIPORASPIDA, Haeckel. + +_Definition._--#Dorataspida# with twenty radial spines, each of which bears +two opposite apophyses. The spherical shell is composed either of the +meeting branches of these apophyses (Phractaspida), or of twenty perforated +plates, produced by concrescence of their branches (Ceriaspida). + + + +A. Tribe I. #Phractaspida#, Haeckel. + +_Definition._--#Dorataspida# without perforated plates; the spherical shell +is composed only of the meeting branches of the two opposite apophyses, +which arise from each radial spine. Therefore the meshes of the shell are +all sutural. + + + +Genus 349. _Phractaspis_,[389] Haeckel, 1881, Prodromus, p. 467. + +_Definition._--#Dorataspida# without perforated plates; shell composed only +of the meeting branches of the two opposite apophyses, which arise from +each radial spine. Condyles of the branch-ends without by-spines. + +The genus _Phractaspis_ is the most simple and primitive form among all +Dorataspida, and may be regarded as the common ancestral form either of +this whole family, or at least of its first subfamily, the Diporaspida. In +all members of this subfamily the spherical shell is composed of twenty +radial spines, each of which bears two opposite apophyses; but the mode of +composition is different in the two tribes of the subfamily, in the +Phractaspida and Ceriaspida. In the simpler tribe, the Phractaspida, the +shell is composed only of the meeting branches of the apophyses of +neighbouring spines; there are no peculiar perforated plates or shields. In +the Ceriaspida, however, both apophyses of each single spine form a +perforated plate or shield by union of their branches, and the shell is +formed of the meeting edges of these shields. Of course the Ceriaspida must +be derived from the simpler Phractaspida. _Phractaspis_, as the common +ancestral form of both, exhibits a very simple structure of the shell (Pl. +137, figs. 1, 2). Commonly, if the fork-branches of each apophysis be not +again branched, the shell possesses only twenty-two large meshes and forty +sutures. More rarely their number increases, the fork-branches of the +apophyses being again branched (_Phractaspidium_, Pl. 137, fig. 3). + + + +Subgenus 1. _Phractasparium_, Haeckel. + +_Definition._--Shell with twenty-two meshes, and forty sutures, each spine +with only four branches, its two apophyses being simply forked. + + +{809}1. _Phractaspis prototypus_, n. sp. (Pl. 137, fig. 2). + +Radial spines cylindrical, thin, pointed; the outer and inner halves of +nearly equal size. Each spine bears in its middle part two opposite +apophyses, which are simply forked; the four condyles of each spine (or the +thickened ends of the fork-branches) are united with the meeting condyles +of the neighbouring spines by sutures. Therefore the network of the +spherical shell is composed of twenty-two large meshes: two square polar +meshes on each pole (_a a a a_ and _e e e e_); eight triangular circumpolar +meshes (each between two polar and one tropical spine, _a b a_ and _e d +e_); eight tropical rhomboidal meshes (each between one polar, one +equatorial, and two tropical spines: _a b c b_ and _e d c d_); and four +rhomboidal equatorial meshes (each between two tropical and two equatorial +spines _c b c d_). + +_Dimensions._--Diameter of the shell 0.1, of the meshes 0.03 to 0.04; +breadth of the spines and bars 0.005. + +_Habitat._--Cosmopolitan; Mediterranean (Corfu), Atlantic (Stations 348, +354), Indian Ocean (Ceylon), Pacific (Stations 253, 265, 274), &c., +surface. + + +2. _Phractaspis complanata_, n. sp. (Pl. 137, fig. 1). + +Radial spines leaf-shaped, strongly compressed, two-edged, pointed; their +outer part longer than the inner. Each spine with two opposite apophyses +which are simply forked, therefore with four condyles. The network with +forty sutures and twenty-two large meshes, as in the foregoing species. The +broad faces of the eight polar spines lie in two meridian planes, of the +four equatorial spines in the equatorial plane, of the eight tropical +spines in two planes parallel to the latter. The planes of the leaf-shaped +fork-branches lie in the spherical face. + +_Dimensions._--Diameter of the shell 0.1, of the meshes 0.02 to 0.03; +breadth of the fork-branches 0.012. + +_Habitat._--South Atlantic, Station 343, surface. + + +3. _Phractaspis condylophora_, n. sp. + +Radial spines quadrangular, thin; their outer pyramidal part shorter than +the inner. Each spine with four branches, its two opposite apophyses being +simply forked. The eighty condyles (or sutural ends of the branches) much +thickened, twice to four times as broad as the branches themselves. Network +with forty sutures and twenty-two large meshes, as in both foregoing +species. + +_Dimensions._--Diameter of the shell 0.12, of the meshes 0.03 to 0.04; +breadth of the condyles 0.01. + +_Habitat._--South Pacific, Station 288, surface. + + +4. _Phractaspis bipennis_, Haeckel. + + _Dorataspis bipennis_, Haeckel, 1862, Monogr. d. Radiol., p. 413, Taf. + xxi. figs. 1, 2. + + _Phractasplenium bipenne_, Haeckel, 1882, Manuscript. + +Radial spines very thin, quadrangular; their outer pyramidal part shorter +than the inner. Each spine with four bent branches, its two opposite +apophyses being simply forked. Eighty {810}condyles, very thin, pointed. In +the specimens of this remarkable species, which I first observed in +Messina, two opposite equatorial spines had quite free apophyses, not +connected with the neighbouring spines; therefore the thin lattice-work of +the shell exhibited only thirty-six sutures and twenty meshes (two meshes +with six sutures, six meshes with four sutures, and twelve meshes with +three sutures). In similar specimens, which I afterwards observed in the +Canary Islands, all four equatorial spines were connected in the same +manner with the neighbouring spines; therefore they possessed forty sutures +and twenty-two meshes, like _Phractaspis prototypus_ (Pl. 137, fig. 2). +Perhaps the Mediterranean species represents a peculiar genus, +_Phractasplenium bipenne_. + +_Dimensions._--Diameter of the shell 0.1, of the meshes 0.03 to 0.05; +breadth of the spines 0.002. + +_Habitat._--Mediterranean (Messina), Canary Islands (Lanzerote), surface. + + + +Subgenus 2. _Phractaspidium_, Haeckel. + +_Definition._--Shell with forty to eighty or more meshes, and eighty to one +hundred or more sutures. Each spine with six to eight or more branches, its +two apophyses being doubly forked or more ramified. + + +5. _Phractaspis constricta_, n. sp. (Pl. 137, fig. 3). + +Radial spines strongly compressed, two-edged, pointed; their outer half +twice constricted and somewhat longer than the inner half. Each spine with +two opposite forked apophyses, the branches of which are again forked; +therefore eight condyles on each spine. The network of the spherical shell +with eighty sutures and sixty-two meshes (twenty-two large primary meshes +and forty smaller secondary meshes, the latter between the distal +fork-branches). + +_Dimensions._--Diameter of the shell 0.11, of the large meshes 0.04 to +0.05, of the small meshes 0.01; breadth of the spines 0.01. + +_Habitat._--South Atlantic, Station 348, depth 2450 fathoms. + + +6. _Phractaspis cataphracta_, Haeckel. + + _Acanthometra cataphracta_, J. Mueller, 1858, Abhandl. d. k. Akad. d. + Wiss. Berlin, p. 49, Taf. x. figs. 7, 8. + + _Dorataspis cataphracta_, Haeckel, 1862, Monogr. d. Radiol., p. 415. + +Radial spines thin, quadrangular; their outer pyramidal part shorter than +the inner. Each spine with six to eight condyles, the fork-branches of +their two opposite apophyses being (all or partly) again forked. The +network with sixty to eighty sutures and meshes: sometimes as regular as in +the preceding species, at other times more or less irregular. + +_Dimensions._--Diameter of the shell 0.1, of the meshes 0.02 to 0.04; +breadth of the bars 0.004 to 0.008. + +_Habitat._--Mediterranean (Cette), Mueller (Messina), Haeckel; North +Atlantic, Station 353, surface. + + + +{811}Genus 350. _Pleuraspis_,[390] Haeckel, 1881, Prodromus, p. 467. + +_Definition._--#Dorataspida# without perforated plates; shell composed only +of the meeting branches of the two opposite apophyses, which arise from +each radial spine. Condyles of the branch ends bearing by-spines. + +The genus _Pleuraspis_ has quite the same structure of the shell as the +foregoing _Phractaspis_, and differs from it only in the development of +external by-spines; commonly each condyle of the branch end of the +apophyses bears one zigzag by-spine, which is directed parallel to the +radial main-spine from which the apophyses arise. Therefore each suture of +the shell is armed with two divergent by-spines (Pl. 137, fig. 4). + + + +Subgenus 1. _Pleurasparium_, Haeckel. + +_Definition._--Shell regularly developed with twenty-two meshes and forty +sutures (sometimes twenty to twenty-four meshes and thirty-six to +forty-eight sutures); each spine commonly with four branches, its two +apophyses being simply forked. + + +1. _Pleuraspis horrida_, n. sp. (Pl. 137, fig. 4). + +Radial spines roundish, somewhat compressed, very thick, conical, pointed +at both ends, outer part nearly twice as long as the inner. Two apophyses +of each spine simply forked, with short and broad branches and thickened +condyles. Forty sutures, very broad. Twenty-two large meshes three to +four times as broad as the bars. By-spines much developed, as long as the +radius, zigzag, with alternating recurved hooks. + +_Dimensions._--Diameter of the shell 0.15, of the meshes 0.04 to 0.06; +breadth of the bars 0.01 to 0.015. + +_Habitat._--Tropical Pacific (east of Philippines), Station 215, surface. + + +2. _Pleuraspis amphithecta_, n. sp. + +Radial spines two-edged, leaf-shaped, strongly compressed, pointed at both +ends; outer half longer than the inner. Two apophyses of each spine simply +forked, with short and very broad branches; condyles not thickened. Forty +sutures, broad. Twenty-two large meshes twice to three times as broad as +the bars. By-spines zigzag, half as long as the radius. (Resembles +_Phractaspis complanata_, Pl. 137, fig. 1.) + +_Dimensions._--Diameter of the shell 0.12, of the meshes 0.02 to 0.03; bars +0.012. + +_Habitat._--Central Pacific, Station 274, surface. + + +{812}3. _Pleuraspis costata_, Haeckel. + + _Acanthometra costata_, J. Mueller, 1858, Abhandl. d. k. Akad. d. Wiss. + Berlin, p. 49, Taf. ii. fig. 1, Taf. x. figs. 4-6. + + _Dorataspis costata_, Haeckel, 1862, Monogr. d. Radiol., p. 414, Taf. + xxiii. fig. 1. + +Radial spines roundish, conical, pointed at both ends; outer and inner +halves of nearly equal length. Two apophyses of each spine simply forked, +with broad branches and thickened condyles. Forty sutures, broad. +Twenty-two large meshes, four to five times as broad as the bars. By-spines +straight, denticulate, half as long as the radius. (This common species is +rather variable in size and details.) + +_Dimensions._--Diameter of the shell 0.1 to 0.13, meshes 0.03 to 0.06, bars +0.005 to 0.01. + +_Habitat._--Cosmopolitan; Mediterranean, Atlantic, Pacific, surface. + + +4. _Pleuraspis pyramidalis_, n. sp. + +Radial spines quadrangular, their outer part pyramidal, very thick, about +half as long as the prismatic inner part. Two apophyses of each spine +simply forked, with very short and broad branches. Condyles much thickened. +Forty sutures, very broad. Twenty-two meshes small, the largest twice as +broad as the bars; the smaller only half as broad. By-spines short, +straight, denticulate, half as long as the radius. + +_Dimensions._--Diameter of the shell 0.14, meshes 0.005 to 0.03. + +_Habitat._--Western Tropical Pacific, Station 222, surface. + + + +Subgenus 2. _Pleuraspidium_, Haeckel. + +_Definition._--Shell with forty to eighty or more meshes and eighty to one +hundred or more sutures; each spine with six to eight or more branches, its +two apophyses being forked twice or oftener. + + +5. _Pleuraspis ramosa_, n. sp. + +Radial spines roundish, stout, somewhat compressed; their inner and outer +half nearly of equal length. Two apophyses of each spine doubly forked or +more irregularly branched; therefore commonly eight (sometimes six, seven, +nine, or ten to twelve) thickened condyles on each spine. Sutures eighty to +one hundred, broad. Irregular meshes sixty to eighty; three to five times +as broad as the bars. By-spines zigzag, ramified, half as long as the +radius. + +_Dimensions._--Diameter of the shell 0.15, of the meshes 0.007 to 0.014, +breadth of the bars 0.003. + +_Habitat._--Central Pacific, Station 272, surface. + + + +{813}B. Tribe II. #Ceriaspida#, Haeckel. + +_Definition._--#Dorataspida#, the spherical shell of which is composed of +twenty perforated plates, produced by union of the branches of the two +opposite apophyses, which arise from each radial spine. Therefore the +meshes of the shell are partly sutural, partly parmal. + + + +Genus 351. _Dorataspis_,[391] Haeckel, 1860, Monatsber. d. k. preuss. Akad. +d. Wiss. Berlin, p. 811. + +_Definition._--#Dorataspida# with twenty plates, which are perforated by +forty aspinal pores (two pores in each plate). Surface of the shell without +combs, dimples, and by-spines. + +The genus _Dorataspis_ opens the long series of the Ceriaspida, or of those +Dorataspida in which the shell is composed of twenty plates, each of which +is perforated by two primary aspinal pores. This tribe has arisen from the +simpler Phractaspida by reunion of the branches of the apophyses in each +single spine. If in _Phractaspis_, their common ancestral form (Pl. 137, +figs. 1, 2), the neighbouring fork-branches of both opposite apophyses in +each radial spine become recurved and united, they will produce a shield, +which is perforated by two pores and between them by the spine itself. +These two "primary aspinal pores" are characteristic of all Ceriaspida; +among these _Dorataspis_ itself is the most simple form. Its shell exhibits +therefore constantly forty aspinal pores, and besides these a variable +number of "sutural pores" (in the sutures between the twenty plates). If in +each suture there be only a single pore, we get on the whole fifty-two or +fifty-four pores; if in each suture there be two or three pores, that +number becomes doubled or tripled. + + + +Subgenus 1. _Doratasparium_, Haeckel. + +_Definition._--Shell with fifty-two sutures; four polar plates on each pole +of the main axis meeting in one point (in the pole itself); therefore all +eight polar plates pentagonal and of equal size. Spherical shell therefore +composed of four (equatorial) hexagonal plates and of sixteen pentagonal +(eight tropical and eight polar plates). + + +1. _Dorataspis fusigera_, n. sp. (Pl. 138, fig. 2). + +Shell with fifty-two sutures and fifty-two sutural meshes, with four +hexagonal and sixteen pentagonal plates. Both aspinal meshes of each plate +elliptical, twice to four times as broad as the {814}sutural meshes. Radial +spines in the outer half fusiform, somewhat longer than the inner +cylindrical half. + +_Dimensions._--Diameter of the shell 0.08 to 0.09, of the parmal meshes 0.1 +to 0.2, of the sutural meshes 0.004 to 0.01. + +_Habitat._--Central Pacific, Station 271, surface. + + +2. _Dorataspis macracantha_, n. sp. + +Shell with fifty-two sutures and fifty-two sutural meshes; with four +hexagonal and sixteen pentagonal plates. Both aspinal meshes of each plate +circular, small, twice as broad as the small sutural meshes. Radial spines +quadrangular, prismatic, their outer half twice to three times as long as +the inner half. + +_Dimensions._--Diameter of the shell 0.12, of the parmal pores 0.008, of +the sutural meshes 0.004. + +_Habitat._--South Pacific, Station 288, surface. + + +3. _Dorataspis macropora_, n. sp. + +Shell with fifty-two sutures and one hundred to one hundred and fifty +sutural meshes, with four hexagonal and sixteen pentagonal plates. Both +aspinal meshes nearly circular, very large, five to ten times as broad as +the small circular sutural meshes; the number of the latter is in this +species multiplied, in each suture being two to three (commonly three) +small pores. Radial spines in the outer half leaf-shaped, compressed, +nearly lanceolate, longer than in the inner cylindrical half. + +_Dimensions._--Diameter of the shell 0.16, of the parmal pores 0.03 to +0.04, of the sutural pores 0.004 to 0.006. + +_Habitat._--Indian Ocean (Madagascar), Rabbe, surface. + + + +Subgenus 2. _Dorataspidium_, Haeckel. + +_Definition._--Shell with fifty-four sutures; four polar plates on each +pole of the main axis different in pairs; two major hexagonal meeting in a +polar suture (the "hydrotomical suture"); two minor pentagonal, not meeting +together (separated by that hydrotomical suture). Spherical shell therefore +composed of eight hexagonal plates (four equatorial and four polar) and by +twelve pentagonal plates (eight tropical and four polar plates). + + +4. _Dorataspis loricata_, Haeckel. + + _Dorataspis loricata_, Haeckel, 1862, Monogr. d. Radiol., p. 415, Taf. + xxi. figs. 3-6. + +Shell with fifty-four sutures and fifty-four sutural meshes, with eight +hexagonal and twelve pentagonal plates. Both aspinal meshes of each plate +kidney-shaped or roundish, nearly of the {815}same size as the sutural +meshes. Radial spines cylindrical; their outer half on the pointed distal +end two-edged and longer than the inner half. + +_Dimensions._--Diameter of the shell 0.14, of its meshes 0.008 to 0.016. + +_Habitat._--Mediterranean (Messina), North Atlantic (Canary Islands), +Azores, surface. + + +5. _Dorataspis typica_, n. sp. (Pl. 138, figs. 4, 4_a_). + +Shell with fifty-four crest-like sutures and fifty-four circular sutural +meshes, with eight hexagonal and twelve pentagonal plates. Both aspinal +meshes of each plate elliptical, twice to three times as broad as the +sutural meshes. Aspinal meshes of the four equatorial plates twice as broad +as those of the sixteen other plates. The meshes are surrounded by elevated +and denticulated crests (incipient spine-sheaths). Radial spines +compressed, more or less two-edged; outer pointed half somewhat larger than +the inner half. (In this typical species the composition of the shell +prevailing in the majority of Ceriaspida is very clear.) + +_Dimensions._--Diameter of the shell 0.15 to 0.18, of the aspinal pores +0.02 to 0.03, of the sutural pores 0.01. + +_Habitat._--Central Pacific, Stations 270 to 274, surface and in various +depths. + + +6. _Dorataspis micropora_, n. sp. (Pl. 138, fig. 3). + +Shell with fifty-four sutures and fifty-four very small sutural meshes, +with eight hexagonal and twelve pentagonal plates. Both aspinal meshes of +each plate elliptical, four to six times as broad as the sutural meshes. +Radial spines in the outer half conical, somewhat shorter than in the inner +cylindrical half. + +_Dimensions._--Diameter of the shell 0.11, of the aspinal pores 0.01 to +0.02, of the sutural pores 0.003. + +_Habitat._--North Pacific, Station 244, depth 2900 fathoms. + + +7. _Dorataspis gladiata_, n. sp. + +Shell with fifty-four sutures and one hundred to one hundred and twenty +sutural meshes, with eight hexagonal and twelve pentagonal plates. Both +aspinal meshes elliptical, three times as broad as the small sutural +meshes; commonly two meshes in each suture. Radial spines sword-shaped, +two-edged, tapering from the shell towards the two ends. (Resembles +_Belonaspis datura_, Pl. 139, fig. 9, but differs in the spherical shell, +the equal size of the four equatorial spines, and the absence of +by-spines.) + +_Dimensions._--Diameter of the shell 0.12, of the aspinal pores 0.012, of +the sutural pores 0.004. + +_Habitat._--Indian Ocean (Madagascar), Rabbe, surface. + + +8. _Dorataspis polypora_, n. sp. + +Shell with fifty-four sutures and one hundred and sixty to two hundred +sutural meshes, with eight hexagonal and twelve pentagonal plates. Commonly +three meshes (sometimes four) on {816}each suture. Both aspinal meshes +kidney-shaped, four times as broad as the small sutural meshes. Radial +spines thick, in the inner longer part cylindrical, in the outer shorter +part conical. (Differs from all other species in the multiplication of the +sutural pores.) + +_Dimensions._--Diameter of the shell 0.2, of the aspinal pores 0.016, of +the sutural pores 0.004. + +_Habitat._--Equatorial Atlantic, Station 347, surface. + + + +Genus 352. _Diporaspis_,[392] n. gen. + +_Definition._--#Dorataspida# with twenty plates, which are perforated by +forty aspinal pores (two pores in each plate). Surface of the shell without +combs and dimples, but armed with numerous by-spines. + +The genus _Diporaspis_ has the same characteristic structure of the shell +as the typical _Dorataspis_, and differs from it only in the development of +numerous by-spines on the surface. The number of the sutures between the +twenty plates is sometimes fifty-two, at other times fifty-four, and in +each suture we find occasionally a single pore, at other times two or three +such pores. + + + +Subgenus 1. _Diporasparium_. + +_Definition._--Shell with fifty-two sutures, four polar plates on each pole +of the main axis meeting in one common point; therefore all eight polar +plates pentagonal and of equal size. Shell therefore composed of four +(equatorial) hexagonal plates, and of sixteen pentagonal (eight tropical +and eight polar) plates. + + +1. _Diporaspis nephropora_, n. sp. (Pl. 134, fig. 15). + +Shell with fifty-two sutures and fifty-two sutural pores, with four +hexagonal and sixteen pentagonal plates. Both aspinal pores of each plate +kidney-shaped, about twice as broad as the circular sutural pores. Radial +spines thin, cylindrical, longer than the radius. By-spines forked, only +one-third as long as the radius. + +_Dimensions._--Diameter of the shell 0.13, parmal pores 0.03, sutural pores +0.07. + +_Habitat._--North Pacific, Station 244, surface. + + +2. _Diporaspis circopora_, n. sp. + +Shell with fifty-two sutures and one hundred to one hundred and fifty +sutural pores, with four hexagonal and sixteen pentagonal plates. Both +aspinal pores of each plate circular, very large, six to eight times as +broad as the small circular sutural pores (in each suture two to three +pores). {817}Radial spines strongly compressed, two-edged; outer half +shorter than the inner. By-spines undulate, half as long as the radius. + +_Dimensions._--Diameter of the shell 0.12, of the parmal pores 0.02 to +0.03, of the sutural pores 0.003 to 0.004. + +_Habitat._--South Pacific, Station 287, surface. + + + +Subgenus 2. _Diporaspidium_, Haeckel. + +_Definition._--Shell with fifty-four sutures, four polar plates on each +pole of the main axis different in pairs: two major hexagonal meeting in a +polar ("geotomical") suture, two minor pentagonal, not meeting together +(separated by that suture). Shell therefore composed of eight hexagonal +plates (four equatorial and four polar) and of twelve hexagonal plates +(eight tropical and four polar). + + +3. _Diporaspis zygopora_, n. sp. + +Shell with fifty-four sutures and fifty-four circular sutural pores: with +eight hexagonal and twelve pentagonal plates. Both aspinal pores of each +plate elliptical, three times as broad as the sutural pores. Radial spines +compressed, two-edged; outer half shorter than the inner. By-spines very +numerous, simple, one-third as long as the radius, forming coronels or +elegant circles around the pores (a small coronel around each sutural pore, +a large one around each couple of aspinal pores). + +This typical species is nearly allied to _Dorataspis typica_ (Pl. 138, fig. +4), and may be derived from it by development of the coronels of by-spines. + +_Dimensions._--Diameter of the shell 0.16, aspinal pores 0.03, sutural +pores 0.01. + +_Habitat._--Central Pacific, Station 271, surface + + + +Genus 353. _Orophaspis_,[393] Haeckel, 1881, Prodromus, p. 468. + +_Definition._--#Dorataspida# with twenty plates, which are perforated by +forty aspinal pores (two pores in each plate). Surface of the shell without +combs, dimples, and by-spines. Each radial spine bears outside of the shell +two opposite free apophyses, which are either simple or branched. + +The genus _Orophaspis_ differs not only from its ancestral form, +_Dorataspis_, but from all other Dorataspida in the development of peculiar +free apophyses on the radial spines, outside the shell. These apophyses, +two being opposite on each spine, appear as a repetition of the primary +apophyses of _Phractaspis_; they are either simple or branched, and +sometimes the branches are united together, forming an outer free shield +with two or four pores. These outer plates represent the beginning of a +second outer shell and form the transition to _Phractopelta_, the ancestral +form of the Phractopeltida. + + + +{818}Subgenus 1. _Orophasparium_, Haeckel. + +_Definition._--Free apophyses of the radial spines simple, not branched. + + +1. _Orophaspis astrolonche_, n. sp. + +Parmal pores of the shell circular, twice as large as the sutural pores and +as the breadth of the bars. Radial spines very long, three to six times as +long as the diameter of the shell, compressed, two-edged; each with two +simple, opposite, triangular apophyses; their distance from the shell equal +to its diameter. + +_Dimensions._--Diameter of the shell 0.05, parmal pores 0.004, sutural +pores 0.002. + +_Habitat._--North Pacific, Station 239, surface. + + +2. _Orophaspis gladiata_, n. sp. + +Parmal pores of the shell circular, of the same size as the sutural pores +and the bars. Radial spines thick, spindle-shaped, scarcely longer than the +diameter of the shell, each with two simple opposite conical apophyses; +their distance from the shell about equal to its radius. + +_Dimensions._--Diameter of the shell 0.06, pores 0.003. + +_Habitat._--Central Pacific, Station 265, surface. + + + +Subgenus 2. _Orophaspidium_, Haeckel. + +_Definition._--Free apophyses of the radial spines branched, their branches +free (not anastomosing). + + +3. _Orophaspis furcata_, n. sp. (Pl. 133, fig. 6). + +Parmal pores of the shell roundish or elliptical, three times as broad as +the sutural pores and the bars. Radial spines very long, compressed, each +with two opposite apophyses, which are simply forked; their distance from +the shell somewhat greater than its diameter. + +_Dimensions._--Diameter of the shell 0.06 to 0.08, parmal pores 0.006, +sutural pores 0.002. + +_Habitat._--Central Pacific, Station 274, surface. + + +4. _Orophaspis ramosa_, n. sp. + +Parmal pores of the shell circular, of the same size as the sutural pores +and the bars. Radial spines compressed, very long, each with two opposite +apophyses, which are more or less irregularly branched (commonly between +eight and twelve thin branches on each spine); their distance from the +shell smaller than its diameter. + +_Dimensions._--Diameter of the shell 0.08, pores 0.006. + +_Habitat._--North-West Pacific, Station 235, surface. + + + +{819}Subgenus 3. _Stegaspis_, Haeckel, 1881, Prodromus, p. 468. + +_Definition._--Free apophyses of the radial spines branched, and by reunion +of their anastomosing branches forming perforated shields. + + +5. _Orophaspis diporaspis_, n. sp. + +Parmal pores of the shell circular, of the same size as the sutural pores +and the bars. Radial spines sword-shaped, two-edged, very broad; each spine +bears an elliptical free shield with two longish pores (opposite on the two +flat sides of the sword). Distance of the twenty free two-pored shields +from the shell about equal to its diameter. + +_Dimensions._--Diameter of the shell 0.04, of the pores 0.004. + +_Habitat._--South Pacific, Station 295, surface. + + +6. _Orophaspis tessaraspis_, n. sp. + +Parmal pores of the shell roundish, somewhat larger than the sutural pores +and the bars. Radial spines very long, compressed; each spine bears a +roundish free shield with four irregular pores disposed in a cruciform +manner, the two larger pores being opposite on the flat sides of the spine, +the two smaller being opposite but on its two edges. Distance of the twenty +free four-pored shields from the shell about equal to its radius. + +_Dimensions._--Diameter of the shell 0.05, of the pores 0.003. + +_Habitat._--North Pacific, Station 239, surface. + + + +Genus 354. _Ceriaspis_,[394] Haeckel, 1881, Prodromus, p. 468. + +_Definition._--#Dorataspida# with twenty plates, which are perforated by +forty aspinal pores (two pores in each plate). Surface of the shell with +numerous dimples, separated by a network of elevated combs. No by-spines. + +The genus _Ceriaspis_ has the same structure of the shell, as its ancestral +form _Dorataspis_, differing from it only in the development of high combs +or crests, which form on the surface of the shell a peculiar elevated +network. The dimples or funnel-shaped pits between these combs are either +all or partly perforated by the pores of the shell. Both the aspinal pores +of each plate are usually placed in one common dimple, whilst each sutural +pore is placed in its peculiar smaller dimple. + + + +Subgenus 1. _Ceriasparium_, Haeckel. + +_Definition._--Shell-surface with seventy to one hundred or more small +funnel-shaped dimples, each of which opens on the bottom by one pore or by +a couple of {820}apertures; twenty larger dimples in the centre of the +plates (each with a couple of aspinal pores) and fifty to one hundred or +more smaller dimples, each of which contains one sutural pore. No blind +dimples between the perforated dimples. + + +1. _Ceriaspis lacunosa_, n. sp. + +Shell spherical with seventy-two funnel-shaped dimples, each of which is +perforated on the bottom by one or two apertures; twenty larger dimples in +the centre of the plates, each with two elliptical aspinal pores, and +fifty-two smaller sutural dimples between them, each with one circular pore +of half the size. No blind dimples. Radial spines quadrangular, stout; +their outer part shorter than the inner. + +_Dimensions._--Diameter of the shell 0.1, of the forty parmal pores 0.01, +of the fifty-two sutural pores 0.005. + +_Habitat._--South Atlantic, Station 330, surface. + + +2. _Ceriaspis scrobiculata_, n. sp. + +Shell spherical, with seventy-four funnel-shaped dimples, each of which is +perforated on the bottom by one or two apertures; twenty larger dimples in +the centre of the plates, each with two kidney-shaped large pores, and +fifty-four smaller dimples on the sutures, each with one circular pore of +one-fourth of the size of the reniform pores. No blind dimples. Radial +spines cylindrical, the outer part longer than the inner. + +_Dimensions._--Diameter of the shell 0.12, of the forty parmal pores 0.016, +of the fifty-four sutural pores 0.004. + +_Habitat._--Central Pacific, Station 270, surface. + + + +Subgenus 2. _Ceriaspidium_, Haeckel. + +_Definition._--Shell-surface with funnel-shaped dimples (commonly one +hundred and seventy-six or one hundred and eighty-two), which on the bottom +are partly closed, partly perforated by one aperture (or by a pair of +pores). The blind dimples are placed on the corners of the twenty plates, +and are therefore either one hundred and four or one hundred and eight; if +there be no polar suture, the blind dimples are one hundred and four +(twenty-four on the four hexagonal equatorial plates, forty on the eight +pentagonal tropical plates, and forty on the eight pentagonal polar +plates); if, however, there be a polar suture on both main poles, the +number of blind dimples is one hundred and eight (twenty-four on the four +hexagonal equatorial and twenty-four on the four hexagonal polar plates, +two opposite on each pole; forty on the eight pentagonal tropical plates +and twenty on the four pentagonal polar plates, two opposite on each pole). +Between the blind dimples there are usually seventy-two to seventy-four +perforated {821}dimples, twenty larger parmal dimples (enclosing a radial +spine and a couple of aspinal pores) and fifty-two to fifty-four sutural +dimples (sometimes one hundred or more), each of which encloses one +sutural pore. + + +3. _Ceriaspis inermis_, n. sp. (Pl. 138, fig. 5). + +Shell spherical, with one hundred and seventy-six funnel-shaped dimples, +one hundred and four of which are blind and seventy-two perforated; of the +latter, each of the fifty-two smaller contains a single sutural pore, each +of the twenty larger a couple of aspinal pores. The elliptical or +kidney-shaped aspinal pores are about twice as broad as the circular +sutural pores. Radial spines thin, compressed, two-edged; their outer +prolongation very short, rudimentary, scarcely higher than the axis of the +surrounding funnel, and projecting but slightly from its aperture. + +_Dimensions._--Diameter of the shell 0.15, of the forty parmal pores 0.016, +of the fifty-two sutural pores 0.008. + +_Habitat._--South Pacific, Station 289, surface. + + +4. _Ceriaspis favosa_, n. sp. (Pl. 138, fig. 6). + +Shell polyhedral (icosahedral), with one hundred and eighty-two +funnel-shaped dimples, one hundred and eight of which are blind and +seventy-four perforated; of the latter, each of the fifty-four smaller +contains a single sutural pore, each of the twenty larger a couple of +aspinal pores. All pores roundish, nearly of the same size. Radial spines +thin, compressed, two-edged; their outer part somewhat longer than the +inner. + +_Dimensions._--Diameter of the shell 0.12 to 0.13, of the pores 0.01 to +0.015. + +_Habitat._--Central Pacific, Station 274, surface. + + +5. _Ceriaspis icosahedra_, n. sp. + +Shell polyhedral (icosahedral), with one hundred and eighty-two +funnel-shaped dimples, one hundred and eight of which are blind and +seventy-four perforated; of the latter, each of the fifty-four smaller +contains one small sutural pore, each of the twenty larger a couple of +aspinal pores. The kidney-shaped aspinal pores are very large, four to six +times as broad as the small circular sutural pores. Radial spines strong, +quadrangular, their outer part from two to three times as long as the inner +part. + +_Dimensions._--Diameter of the shell 0.16, of the parmal pores 0.015 to +0.02, of the sutural pores 0.003 to 0.004. + +_Habitat._--Tropical Atlantic, Station 349, surface. + + +6. _Ceriaspis cicatricosa_, n. sp. + +Shell spherical, with two hundred and fifty to three hundred (or more) +small funnel-shaped dimples, the majority of which are blind, the minority +perforated by pores; of the latter forty {822}are aspinal pores (two at the +base of each spine), the others sutural pores. All pores nearly of the same +size. As the shell of this species is very dark and thick-walled, it was +impossible to obtain more information with regard to the pores. Radial +spines very stout; the outer conical part shorter than the inner +cylindrical part. + +_Dimensions._--Diameter of the shell 0.2, of the pores 0.006 to 0.008. + +_Habitat._--North Pacific, Station 236, surface. + + + +Genus 355. _Hystrichaspis_,[395] n. gen. + +_Definition._--#Dorataspida# with twenty plates, which are perforated by +forty aspinal pores (two pores in each plate). Surface of the shell with +numerous dimples, separated by a network of elevated combs. Numerous +by-spines. + +The genus _Hystrichaspis_ has the same structure with regard to the shell, +as its ancestral form _Ceriaspis_, and differs from the latter only in +possessing numerous by-spines. Moreover, in the former the dimples of the +shell-surface are either all perforated by pores, or some of them are +blind. + + + +Subgenus 1. _Hystrichasparium_, Haeckel. + +_Definition._--Shell with seventy to one hundred or more funnel-shaped +dimples, each of which opens on the bottom by one aperture or by a couple +of pores; twenty larger dimples in the centre of the plates (each with a +couple of pores, sometimes also three couples) and fifty to one hundred or +more smaller dimples, each of which contains one sutural pore. No blind +dimples between the perforated dimples. + + +1. _Hystrichaspis pectinata_, n. sp. (Pl. 138, fig. 8). + +Shell with numerous (one hundred to two hundred?) funnel-shaped dimples, +each of which is pierced at the bottom by one or two pores; twenty larger +dimples in the centre of the plates (each with two aspinal pores), and +fifty to one hundred and fifty or more smaller dimples (each with one +sutural pore). No blind dimples. Crests between the dimples armed with a +continuous series of simple by-spines. Radial main spines stout, in the +inner half cylindrical, in the outer conical, more or less compressed. + +_Dimensions._--Diameter of the shell 0.13, of the pores 0.004 to 0.006. + +_Habitat._--Tropical Atlantic, Station 352, surface. + + +2. _Hystrichaspis furcata_, n. sp. (Pl. 138, fig. 9). + +Shell with numerous (one hundred to two hundred?) funnel-shaped dimples, +each of which is pierced at the bottom by one or two pores; twenty larger +dimples in the centre of the plates (each {823}with two large aspinal +pores), and fifty to one hundred and fifty or more smaller dimples (each +with one small sutural pore). No blind dimples. Crests between the +dimples armed with forked by-spines. Radial main spines stout, leaf-shaped, +tapering towards both ends. + +_Dimensions._--Diameter of the shell 0.12, parmal pores 0.01, sutural pores +0.005. + +_Habitat._--Central Pacific, Station 276, surface. + + +3. _Hystrichaspis cristata_, n. sp. (Pl. 138, fig. 11). + + _Siphonasphis cristata_, Haeckel, 1882, Manuscript. + +Shell with numerous (one hundred to two hundred?) funnel-shaped dimples, +each of which is pierced at the bottom by one or more pores. Twenty larger +dimples in the centre of the plates are pierced by the radial main-spines; +among these fourteen contain each a couple of aspinal pores; six others are +much larger, and contain each six larger pores; these six plates are two +opposite equatorial plates and four polar plates, placed in the same +meridian plane (the "hydrotomical plane"); in each of these six +"hydrotomical dimples" two pores are placed opposite to one another on the +two edges of the leaf-shaped spine, four others being opposite in pairs on +both flat sides of it. By this peculiar structure this species connects the +true _Hystrichaspis_ with _Hexalaspis_ and _Diploconus_; however the twenty +spines are of equal length, and the shell continues to be spherical. The +twenty radial main-spines are leaf-like and compressed. The crests between +the dimples are dentated by a series of small by-spines. + +_Dimensions._--Diameter of the shell 0.15, of the aspinal pores 0.01, of +the sutural pores 0.005. + +_Habitat._--North Pacific, Station 240, surface. + + + +Subgenus 2. _Hystrichaspidium_, Haeckel. + +_Definition._--Shell-surface with numerous funnel-shaped dimples (commonly +one hundred and seventy-six to one hundred and eighty-two), which on the +bottom are partly closed, partly perforated by one aperture (or by a pair +of pores). The blind dimples are situated on the corners of the twenty +plates; their number is commonly one hundred and four or one hundred and +eight, sometimes more. The perforated dimples, alternating with the former, +are usually seventy-two to seventy-four, sometimes more; twenty larger +parmal dimples (each with a couple of aspinal pores, sometimes also with +three such couples) and fifty-two to fifty-four sutural dimples, sometimes +one hundred or more (each with one sutural pore). (Compare the definition +of _Ceriaspidium_, p. 820.) + + +4. _Hystrichaspis dorsata_, n. sp. (Pl. 138, fig. 10). + +Shell with one hundred and seventy-six funnel-shaped dimples, one hundred +and four of which are blind and seventy-two perforated; of the latter, each +of the fifty-two smaller contains a single {824}sutural pore, each of the +twenty larger a couple of aspinal pores; the elliptical aspinal pores are +twice as broad as the circular sutural pores. The crests between the +dimples are armed with simple scattered short by-spines; usually in the +nodal points, where three combs meet, there exist three or two divergent +by-spines. The twenty radial main-spines are thin and long, compressed. + +_Dimensions._--Diameter of the shell 0.22, of the aspinal pores 0.02, of +the sutural pores 0.01. + +_Habitat._--Central Pacific, Station 271, surface. + + +5. _Hystrichaspis armata_, n. sp. + +Shell with one hundred and seventy-six funnel-shaped dimples, one hundred +and four of which are blind and seventy-two perforated; of the latter, each +of the fifty-two smaller contains a single sutural pore, each of the twenty +larger a couple of aspinal pores. Crests between the dimples comb-like, +armed with a series of simple by-spines. Twenty main-spines very stout, in +the inner part cylindrical, in the outer shorter part conical. + +_Dimensions._--Diameter of the shell 0.25, of the aspinal pores 0.02, of +the sutural pores 0.01. + +_Habitat._--South-East Pacific, Station 300, surface. + + +6. _Hystrichaspis sulcata_, n. sp. + +Shell with one hundred and eighty-two funnel-shaped dimples, one hundred +and eight of which are blind and seventy-four perforated; of the latter, +each of the fifty-four smaller contains a single sutural pore, each of the +twenty larger a couple of aspinal pores. All pores nearly of the same size, +very small. Crests between the dimples very high, sulcated, on the free +edge serrate with short very numerous, simple by-spines. Radial main-spines +very stout and short, conical. + +_Dimensions._--Diameter of the shell 0.2, of the pores 0.003. + +_Habitat._--South Atlantic, Station 325, surface. + + +7. _Hystrichaspis foveolata_, n. sp. + +Shell with very numerous (three hundred to four hundred?) small and deep +funnel-shaped dimples, the majority of which are blind, the minority +perforated; among the latter there are forty larger aspinal pores; the +other smaller (scarcely half as large) pores are sutural. Crests between +the dimples densely armed with simple short by-spines. Radial main-spines +stout, leaf-shaped. + +_Dimensions._--Diameter of the shell 0.12, of the aspinal pores 0.01, of +the sutural pores 0.004. + +_Habitat._--Tropical Atlantic, Station 338, surface. + + +8. _Hystrichaspis divaricata_, n. sp. + +Shell with numerous (two hundred to three hundred?) funnel-shaped dimples, +the majority of which are blind, the minority perforated; among the latter +there are forty larger aspinal pores. {825}Crests between the dimples armed +with long forked by-spines with divergent fork-branches. Radial spines +cylindrical, very long and thick, longer than the diameter of the shell. + +_Dimensions._--Diameter of the shell 0.14, aspinal pores 0.08, sutural +pores 0.03. + +_Habitat._--Central Pacific, Station 266, surface. + + +9. _Hystrichaspis fruticata_, n. sp. (Pl. 138, fig, 7). + +Shell with numerous (one hundred and fifty to two hundred?) funnel-shaped +dimples, the majority of which are blind, the minority perforated; forty +aspinal pores elliptical, of the same size as the circular sutural pores. +Crests between the dimples bearing elegant arborescent by-spines. Twenty +radial main-spines long and thin, cylindrical or a little compressed. + +_Dimensions._--Diameter of the shell 0.17, pores 0.01. + +_Habitat._--Tropical Pacific, Station 275, surface. + + +10. _Hystrichaspis serrata_, n. sp. + +Shell with numerous (two hundred to three hundred?) funnel-shaped dimples, +the majority of which are blind, the minority perforated; forty aspinal +pores of the same size as the sutural pores. Crests between the dimples +covered with denticulated by-spines. Twenty radial main-spines compressed, +two-edged, with serrated edges, about as long as the diameter of the shell. + +_Dimensions._--Diameter of the shell 0.21, pores 0.012. + +_Habitat._--North Pacific, Station 238, surface. + + + +Genus 356. _Coscinaspis_,[396] n. gen. + +_Definition._--#Doratispida# with twenty plates, which are perforated by +eighty to two hundred or more parmal pores (two aspinal and two to ten or +more coronal pores in each plate). Surface without by-spines. + +The genus _Coscinaspis_, together with the following nearly allied genus +_Acontaspis_, may be separated from the other Ceriaspida as a peculiar +tribe, _Coscinaspida_. This tribe is characterised by the larger number of +the parmal pores. Whilst in all other Ceriaspida this number is constantly +forty (only two pores in each plate), here it may be from eighty to two +hundred or more; in each shield the two primary "aspinal pores" are +surrounded by a circle of two to ten or more (commonly eight to twelve) +"coronal pores." The number of sutural pores in this group is also usually +larger. + + + +{826}Subgenus 1. _Coscinasparium_, Haeckel. + +_Definition._--Plates of the shell smooth, without crests, not dimply. + + +1. _Coscinaspis peripora_, n. sp. (Pl. 138, fig. 1). + +Shell thin walled, with smooth surface, without crests and dimples, +perforated by pores of very different sizes. Forty aspinal pores, roundish +or elliptical, of about the same size as the fifty or sixty violin-shaped +sutural pores, and three to four times as broad as the small roundish +coronal pores, which are irregularly formed and distributed, four to eight +occurring on each plate (altogether one hundred to one hundred and twenty). +Radial spines roundish, somewhat compressed; inner and outer half nearly of +the same length. + +_Dimensions._--Diameter of the shell 0.12, aspinal pores 0.01 to 0.012, +coronal pores 0.003. + +_Habitat._--North-West Pacific, Station 235, surface. + + +2. _Coscinaspis stigmopora_, n. sp. + +Shell very thin walled, with smooth surface, without crests and dimples, +perforated by pores of very different sizes. Forty aspinal pores, roundish, +of about the same size as the fifty or sixty violin-shaped sutural pores, +their diameter being about one-fifth of that of the plates. Coronal pores +very numerous (two hundred to four hundred) and very small, irregularly +scattered, ten to twenty occurring in each plate. Sutures strongly +denticulated. Radial spines very thin and short, cylindrical. + +_Dimensions._--Diameter of the shell 0.12 to 0.15, aspinal and sutural +pores 0.01, coronal pores 0.001 to 0.003. + +_Habitat._--North Pacific, Station 257, surface. + + +3. _Coscinaspis rhacopora_, n. sp. + +Shell very thin walled, with smooth surface, without crests and dimples, +perforated by very irregular pores of very different sizes and forms; +commonly more or less lobed or sinuate. Forty aspinal pores and fifty to +eighty sutural pores, larger than the numerous (one hundred to two hundred) +irregularly scattered coronal pores. Sutures very sinuate. Radial spines +cylindrical, thin and long. + +_Dimensions._--Diameter of the shell 0.15 to 0.18, aspinal and sutural +pores 0.01 to 0.02, coronal pores 0.001 to 0.005. + +_Habitat._--Central Pacific, Station 274. + + +4. _Coscinaspis coscinopora_, n. sp. + +Shell thin walled, with smooth surface, without crests and dimples, +perforated by very numerous pores of circular form, but of different sizes. +Forty aspinal pores and one hundred to two hundred {827}sutural pores much +larger than the coronal pores, which are very small and very numerous +(fifty to sixty on each plate). Sutures sinuate. Radial spines compressed, +outer and inner half nearly of equal length. + +_Dimensions._--Diameter of the shell 0.3, aspinal and sutural pores 0.01 to +0.015, coronal pores 0.001 to 0.002. + +_Habitat._--Tropical Atlantic, Station 338, surface. + + +5. _Coscinaspsis polypora_, n. sp. (Pl. 136, fig. 8). + +Shell very thin walled, with smooth surface, without crests and dimples, +the two aspinal pores of each plate narrow, lanceolate, ten to twelve times +as long as broad and half as long as the radius of each plate. Coronal +pores irregular, polygonal, very numerous (two hundred to three hundred on +each plate), commonly arranged more or less regularly in ten to twelve +series parallel to the longitudinal diameter of the aspinal spines (ten to +twenty pores in each series). Sutural pores irregular, polygonal, very +numerous. Radial spines very thin and long, cylindrical. + +_Dimensions._--Diameter of the shell 0.24; length of the aspinal pores +0.04, breadth 0.004; coronal and sutural pores 0.002 to 0.01. + +_Habitat._--Tropical Atlantic, Station 349, surface. + + +6. _Coscinaspis orthopora_, n. sp. + +Shell very thin walled, with smooth surface, without crest and dimples. All +pores of nearly equal size and form; quadrangular, mostly rectangular; one +hundred to two hundred, separated by two systems of parallel bars, +perpendicular one to another, occur in each plate. Sutural pores mostly +triangular. Radial spines very thin and long, cylindrical, somewhat +compressed. (Similar to those of _Phatnaspis lacunaria_, Pl. 136, fig. 9, +but spherical, not ellipsoidal.) + +_Dimensions._--Diameter of the shell 0.2, pores 0.008 to 0.012. + +_Habitat._--Central Pacific, Station 272, surface. + + +7. _Coscinaspis parmipora_, n. sp. (Pl. 137, fig. 9). + + _Craniaspis parmipora_, Haeckel, 1866, Manuscript. + + _Dorataspis parmipora_, Haeckel, 1881, Prodromus, Atlas. + +Shell thin walled, with smooth surface, without crests and dimples. There +are no sutural pores, since all twenty plates are connected by perfect +sinuate sutures (therefore this excellent species may perhaps better +represent a peculiar genus, called by me in 1866 _Craniaspis_). All pores +are parmal pores; each plate with two elliptical aspinal pores, which are +twice to five times broader than the numerous, roundish irregularly +scattered coronal pores (thirty to fifty occurring on each plate). The +radial spines are quite internal, that is, not prolonged on the outside of +the shell; in this respect they resemble those of _Sphaerocapsa_. + +_Dimensions._--Diameter of the shell 0.16, aspinal pores 0.01, coronal +pores 0.002 to 0.005. + +_Habitat._--North Atlantic, Canary Islands (Lanzerote), surface. + + +{828}8. _Coscinaspis isopora_, n. sp. (Pl. 134, figs. 13, 14). + +Shell thick walled, with smooth surface, without crests and dimples. All +pores of the shell nearly of the same size and of similar form, about as +broad as the bars between them, and about two hundred in number, viz., +fifty to sixty (regularly fifty-two or fifty-four) sutural pores and one +hundred and forty to one hundred and fifty parmal pores (forty aspinal +kidney-shaped pores, and one hundred to one hundred and ten coronal +circular pores: six in the angles of each equatorial plate, and five in the +angles of each tropical and polar plate; if the disposition be quite +regular, one hundred and four or one hundred and eight). Radial spines +short, rudimentary, conical. + +_Dimensions._--Diameter of the shell 0.2, of the pores and bars 0.012. + +_Habitat._--Tropical Pacific, Station 218 (off New Guinea), surface. + + + +Subgenus 2. _Coscinaspidium_, Haeckel. + +_Definition._--Surface of the shell dimply, with a network of prominent +crests. + + +9. _Coscinaspis ceriopora_, n. sp. + +Shell thick-walled, with numerous (one hundred and sixty to two hundred?) +funnel-shaped dimples, which are separated by prominent crests; on the +bottom of each dimple there is a simple or double circular pore. If this +species be quite regularly developed, it closely resembles the preceding, +differing from it mainly in the prominent combs of the surface. It +resembles also _Ceriaspis favosa_, Pl. 138, fig. 6; but whilst in this +latter the majority of the dimples are blind, here they are all perforated. +The twenty aspinal dimples (in the centre of each plate) present at the +bottom a couple of pores, all other dimples a single pore. Among the latter +there are fifty to sixty sutural pores and one hundred to one hundred and +ten coronal pores, viz., six in each equatorial plate, and five in each of +the other plates; but the number is not quite constant. Radial spines +strong, in the inner part cylindrical, in the outer conical. + +_Dimensions._--Diameter of the shell 0.15, of the pores and bars 0.01. + +_Habitat._--Tropical Pacific, Station 215, surface. + + + +Genus 357. _Acontaspis_,[397] Haeckel, 1881, Prodromus, p. 468. + +_Definition._--#Dorataspida# with twenty plates, which are perforated by +eighty to two hundred or more parmal pores (in each plate two aspinal and +two to ten or more coronal pores). Surface covered with by-spines. + +The genus _Acontaspis_ has the same characteristic structure of the shell +as _Ceriaspis_, differing from it only in the presence of numerous +by-spines. Each plate is perforated by four to sixteen or more (commonly +ten to twelve) parmal pores, the two central of which are primary "aspinal +pores," all the others being secondary "coronal pores." + + + +{829}Subgenus 1. _Acontasparium_, Haeckel. + +_Definition._--Plates of the shell not dimply, without prominent crests. + + +1. _Acontaspis lanceolata_, n. sp. + +Shell thin walled, even, without crests and dimples between them, +perforated by about three hundred pores of different sizes: forty aspinal +pores elliptical, about as large as the irregular (fifty to sixty) sutural +pores, and two to four times as broad as the small circular coronal pores +(eight to twelve being on each plate, altogether about two hundred). +Between the pores numerous short conical by-spines. Radial main spines +lanceolate, about as long as the radius. (Similar to _Coscinaspis +peripora_, Pl. 138, fig. 1, but with broad lanceolate spines and numerous +short by-spines.) + +_Dimensions._--Diameter of the shell 0.15, aspinal and sutural pores 0.012 +to 0.015, coronal pores 0.004 to 0.008. + +_Habitat._--South Atlantic, Station 325, surface. + + + +Subgenus 2. _Acontaspidium_, Haeckel. + +_Definition._--Surface of the shell dimply, with a network of prominent +crests. + + +2. _Acontaspis hastata_, n. sp. (Pl. 134, fig. 16). + +Shell thick walled, with numerous (one hundred and seventy to one hundred +and ninety) dimples, which are separated by an elevated network of +prominent crests. In the centre of each plate a larger dimple with a couple +of aspinal pores, surrounded by a corona of ten or twelve smaller dimples, +each of which contains a single pore (a coronal and sutural alternately). +All pores circular or roundish, nearly of the same size. If the shell be +quite regularly developed, there are fifty to sixty sutural pores and one +hundred to one hundred and ten coronal pores (six in each equatorial plate, +five in each of the other plates). The knobs of the meeting crests are +conical, and bear each a simple short by-spine. Radial main spines +compressed, at the distal end spear-shaped, with a rhomboidal plate below +the apex, about as long as the radius. + +_Dimensions._--Diameter of the shell 0.18, of the pores and bars 0.01. + +_Habitat._--Western Tropical Pacific (off the Philippines), Station 215. + + +3. _Acontaspis furcata_, n. sp. + +Shell thick walled, dimply, with a network of crests, of the same +composition as in the foregoing species, with one hundred and seventy to +one hundred and ninety dimples (twenty aspinal, one hundred to one hundred +and ten coronal and fifty to sixty sutural dimples). All dimples and pores +nearly of the same size. Each node of the crested network bears a stout +by-spine, which is forked {830}on the base, with two divergent straight +branches (similar to those of _Hystrichaspis furcata_, Pl. 138, fig. 9). +Radial main spines two-edged, sword-like, nearly as long as the diameter of +the shell. + +_Dimensions._--Diameter of the shell 0.13, of the pores 0.008. + +_Habitat._--Central Pacific, Station 272, surface. + + +4. _Acontaspis capillata_, n. sp. + +Shell very dark and thick walled, non-transparent, with very numerous +(three hundred to four hundred or more?) deep funnel-shaped dimples, each +of which is perforated by a small circular pore (forty aspinal, two hundred +to three hundred coronal, and fifty to one hundred sutural pores?). The +high crests between the dimples bear very numerous simple by-spines, nearly +half as long as the radius, so that the shell appears covered with hairs. +Radial main spines very long and thin, cylindrical, longer than the +diameter of the shell. + +_Dimensions._--Diameter of the shell 0.2, of the pores 0.012. + +_Habitat._--North Pacific, Station 244, surface. + + + +Subfamily 2. TESSARASPIDA, Haeckel. + +_Definition._--#Dorataspida# with twenty radial spines, each of which bears +four crossed apophyses (opposite in pairs). The spherical shell is composed +either of the meeting branches of these apophyses (Stauraspida), or of +twenty perforated plates, produced by concrescence of their branches +(Lychnaspida). + + + +A. Tribe II. #Stauraspida#, Haeckel, 1881, Prodromus, p. 467. + +_Definition._--#Dorataspida# with spherical shell, which is composed either +of the meeting branches of the four crossed apophyses only, or exhibits +four to twelve perforated plates which are produced by the crossed +apophyses of four to twelve radial spines (but never of all twenty spines). +Each plate bears four crossed pores. + + + +Genus 358. _Stauraspis_,[398] Haeckel, 1881, Prodromus, p. 467. + +_Definition._--#Dorataspida# without perforated plates; shell composed only +of the meeting branches of the four crossed apophyses, which arise +(opposite in pairs) from each radial spine. Condyles of the branch-ends +without by-spines. + +The genus _Stauraspis_ is the most simple and primitive form among all +Tessaraspida, or that subfamily of Dorataspida, in which the shell is +composed of twenty {831}radial spines, each of which bears four crossed +apophyses. The subfamily may be divided into two different tribes, the +Stauraspida and Lychnaspida. In the Stauraspida either all twenty spines, +or a part of them, bear no perforated plates, and the shell is composed +wholly or partially of the meeting branches of their apophyses. In the +Lychnaspida, however, the four apophyses of each single spine form, by +reunion of their recurved branches, a plate or shield with four crossed +aspinal pores. The Lychnaspida represent therefore a more developed stage +in the shell-formation than the simpler Stauraspida. _Stauraspis_, as the +common ancestral form of both, may be derived phylogenetically from +_Xiphacantha_ or _Stauracantha_, which differ only by the apophyses or +branches of the apophyses not meeting. These branches (originally eight on +each spine) are either simple or again branched. + + + +Subgenus 1. _Staurasparium_, Haeckel. + +_Definition._--Apophyses of the spines simple, not branched; therefore each +spine with four sutural condyles. + + +1. _Stauraspis cruciata_, n. sp. (Pl. 134, fig. 5). + +Radial spines thin, quadrangular, prismatic; outer and inner half nearly of +equal length. Central bases pyramidal, with wing-like edges. Four apophyses +of each spine simple, not branched, with thin condyles. Large meshes of the +shell ten to twenty times as broad as the bars. This and the following +species greatly resemble the simplest forms of _Phractaspis_ (Pl. 137, +figs. 1, 2); they differ from these, however, by the equal size and +distance of the four branches of each spine, which thus form a rectangular +cross. + +_Dimensions._--Diameter of the shell 0.1; breadth of the spines and bars +0.002. + +_Habitat._--Central Pacific, Station 268, surface. + + +2. _Stauraspis xiphacantha_, n. sp. + +Radial spines stout, cylindrical in the inner half, conical in the shorter +outer half. Four apophyses of each spine simple, not branched, broad, with +thick condyles. Meshes of the shell six to eight times as broad as the +bars. + +_Dimensions._--Diameter of the shell 0.12; breadth of the spines and bars +0.008 to 0.01. + +_Habitat._--South Pacific, Station 290, surface. + + + +Subgenus 2. _Stauraspidium_, Haeckel. + +_Definition._--Apophyses of the spines branched; therefore each spine with +eight to twenty or more sutural condyles. + + +{832}3. _Stauraspis furcata_, n. sp. + +Radial spines thin, quadrangular, prismatic; outer and inner halves nearly +of equal length. The four apophyses of each spine simply forked (or partly +with bifid fork-branches); each spine with eight to twelve sutural +condyles. Meshes of the shell ten to twenty times as broad as the bars. + +_Dimensions._--Diameter of the shell 0.15; breadth of the spines and bars +0.003. + +_Habitat._--Central Pacific, Station 266, surface. + + +4. _Stauraspis stauracantha_, n. sp. (Pl. 137, figs. 5, 6). + +Radial spines thin, in the inner longer half cylindrical, in the outer half +conical with thickened base. Four apophyses of each spine doubly forked or +dichotomously (more or less irregularly) branched; each spine with sixteen +to twenty-four sutural condyles. Meshes of the shell of very different +sizes and forms; the largest ten to fifteen, the smallest two to three +times as broad as the bars. + +_Dimensions._--Diameter of the shell 0.14; breadth of of the spines 0.002 +to 0.01, of the bars 0.002. + +_Habitat._--Tropical Atlantic, Station 343, surface. + + + +Genus 359. _Echinaspis_,[399] Haeckel, 1881, Prodromus, p. 467. + +_Definition_--#Dorataspida# without perforated plates; shell composed only +of the meeting branches of the four crossed apophyses, which arise +(opposite in pairs) from each radial spine. Condyles of the branch-ends +bearing by-spines. + +The genus _Echinaspis_ exhibits the same structure of the shell as its +ancestral form _Stauraspis_, and differs from it only in the development of +by-spines on the sutural condyli. + + +1. _Echinaspis dichotoma_, n. sp. + +Radial spines cylindrical, thin, outer half longer than the inner. Four +apophyses of each spine simply forked (or partly with bifid fork-branches); +therefore each spine usually possesses eight (sometimes ten to twelve) +sutural condyles. Meshes of the shell ten to twelve times as broad as the +bars. Each condyle bears a zigzag by-spine, half as long as the radius. + +_Dimensions._--Diameter of the shell 0.12, of the spines 0.004 to 0.006. + +_Habitat._--North Pacific, Station 253, surface. + + +{833}2. _Echinaspis diadema_, n. sp. + +Radial spines thin and long, quadrangular, prismatic; outer half two to +three times as long as the inner. Four apophyses of each spine simply +forked (or partly with bifid fork-branches); each spine with eight to +twelve sutural condyles. Meshes of the shell fifteen to twenty-five times +as broad as the bars. Each condyle bears a simple bristle-shaped by-spine, +nearly as long as the radius. + +_Dimensions._--Diameter of the shell 0.11; breadth of the spines and bars +0.002. + +_Habitat._--South Atlantic, Station 333, surface. + + +3. _Echinaspis echinoides_, n. sp. (Pl. 137, figs. 7,8). + +Radial spines roundish, in the outer half conical, and two to three times +as broad as in the inner half. Four apophyses of each spine doubly forked +or dichotomously (more or less irregularly) branched; each spine with +sixteen to twenty-four sutural condyles. Meshes of the shell four to eight +times as broad as the bars. Each condyle bears a zigzag by-spine, one-third +as long as the radius. + +_Dimensions._--Diameter of the shell 0.15; breadth of the spines 0.004 to +0.01, of the bars 0.002. + +_Habitat._--Central Pacific, Station 266, surface. + + + +Genus 360. _Zonaspis_,[400] n. gen. + +_Definition._--#Dorataspida# with four plates, each of which is perforated +by four crossed aspinal pores; these four plates are formed by the united +branches of the other spines (eight polar and eight tropical) form no +lattice-plates by union. Each condyle bears a by-spine. + +The genus _Zonaspis_ differs from all other Dorataspida in the peculiar +formation of the four equatorial spines, which form by union of the +recurved branches of their apophyses four perforated plates (each with four +crossed pores), whilst the branches of the sixteen other plates do not +unite to form plates, but simply meet the branches of the neighboring +spines. + + +1. _Zonaspis fragilis_, n. sp. + +Radial spines very thin and long, cylindrical. Four meshes of each +equatorial plate pentagonal, ten to twelve times as broad as the bars. +By-spines zig-zag, nearly as long as the radius. + +_Dimensions._--Diameter of the shell 0.16, of the parmal pores 0.018. + +_Habitat._--South Atlantic, Station 332, surface. + + +{834}2. _Zonaspis cingulata_, n. sp. (Pl. 134, figs. 3, 4). + +Radial spines cylindrical in the inner half, with thickened pyramidal bases +(fig. 3), conical in the outer half; both halves of equal length. The four +meshes of each equatorial plate egg-shaped, four to six times as broad as +the bars. By-spines zigzag, half as long as the radius. + +_Dimensions._--Diameter of the shell 0.15, of the parmal meshes 0.015. + +_Habitat._--Tropical Pacific (east coast off Philippines), Station 275, +surface. + + +3. _Zonaspis aequatorialis_, n. sp. (Pl. 135, fig. 5). + +Radial spines stout, cylindrical in the shorter inner half, conical in the +longer outer half. The four meshes of each equatorial plate circular, only +twice as broad as the bars. By-spines zigzag, nearly as long as the radius. + +_Dimensions._--Diameter of the shell 0.11, of the parmal meshes 0.008. + +_Habitat._--Equatorial Atlantic, Station 347, surface. + + + +Genus 361. _Dodecaspis_,[401] n. gen. + +_Definition._--#Dorataspida# with twelve plates, each of which is +perforated by four crossed aspinal pores; these twelve plates are formed by +the united branches of the apophyses of four equatorial and eight polar +spines. The branches of the apophyses of the eight tropical spines form no +lattice-plates by union. Each condyle bears a by-spine. + +The genus _Dodecaspis_ differs from all other Dorataspida in the peculiar +composition of its shell; twelve spines (four equatorial and eight polar +spines) form by union of the branches of their apophyses twelve plates, +each of which exhibits four crossed pores, whilst the eight other +(tropical) spines form no perforated plates, but simply unite with the +neighbouring spines by meeting branches. Some irregularity is often to be +found in this genus; instead of four pores in each plate there may be two +closed, the other two which are opposite being open. Several times I +observed a peculiar "hemihedral" variety: only six spines of one meridian +plane (the two equatorial and the four polar spines of the "hydrotomical" +plane) exhibited complete shields, whilst the branches of the other +fourteen plates remained open. This "hemihedral" form may perhaps represent +a peculiar genus, _Hemiaspis_. + + +1. _Dodecaspis tricinata_, n. sp. (Pl. 134, fig. 1). + +Radial spines thin and long, cylindrical. The four meshes of each +equatorial and each polar plate of equal size, pentagonal, about eight +times as broad as the bars. By-spines zigzag, nearly as long as the radius. +In this species the hemihedral variety, _Hemiaspis_, often occurs. + +_Dimensions._--Diameter of the shell 0.15, of the parmal pores 0.016. + +_Habitat._--South-east Pacific (west coast of Patagonia), Station 302, +surface. + + +{835}2. _Dodecaspis trizonia_, n. sp. + +Radial spines thin, cylindrical in the longer inner half, conical in the +shorter outer half. The four meshes of each equatorial and each polar plate +of equal size, roundish or nearly circular, five to six times as broad as +the bars. By-spines straight, denticulated, scarcely half as long as the +radius. + +_Dimensions._--Diameter of the shell 0.12, of the parmal pores 0.012. + +_Habitat._--South-west Pacific (east coast of New Zealand), Station 169, +surface. + + + +B. Tribe II. #Lychnaspida#, Haeckel, 1881, Prodromus, p. 467. + +_Definition._--#Dorataspida# with twenty perforated plates or fenestrated +shields (each plate at least with four pores), produced by union of the +branches of the four crossed apophyses, which arise, opposite in pairs, +from each radial spine. The spherical shell is composed of the twenty +plates united by sutures (rarely by concrescence). + + + +Genus 362. _Tessaraspis_,[402] Haeckel, 1881, Prodromus, p. 468. + +_Definition._--#Dorataspida# with twenty plates, which are perforated by +eighty aspinal pores (four crossed pores in each plate). Surface smooth, +without by-spines. + +The genus _Tessaraspis_ introduces the series of Lychnaspida, which +comprise all those Dorataspida in which the shell is composed of twenty +plates, each of which is perforated by four primary aspinal pores. In +_Tessaraspis_ and _Lychnaspis_ each plate exhibits only these four primary +pores, whilst in _Icosaspis_ and _Hylaspis_ they become surrounded by a +circle of secondary or coronal pores. If in _Stauraspis_, the common +ancestral form of the Tessaraspida, the four crossed apophyses of each +single radial spine became recurved and united together, we should have the +typical plate of _Tessaraspis_, in which the piercing radial spine is +surrounded by four crossed pores of equal size. The number of sutural +pores, between the neighbouring plates, is variable; usually each plate is +surrounded by a circle of eight to twelve sutural pores. The sutures +between the meeting condyles of the apophyses usually remain open; but in +some species they become obliterated (subgenus _Tessaraspidium_). + + + +Subgenus 1. _Tessarasparium_, Haeckel. + +_Definition._--Condyles of the neighbouring plates connected by permanent +open sutures; therefore the whole shell is composed of twenty separated +pieces of acanthin. + + +{836}1. _Tessaraspis arachnoides_, n. sp. (Pl. 136, fig. 1). + +Parmal pores pentagonal, ten to twenty times as broad as the thin +thread-like bars, on an average of about the same size as the irregular +sutural meshes; the majority of the latter are either triangular or +hexagonal. Radial spines very thin and long, cylindrical, their outer part +two to four times as long as the inner. As the insertion of the spines is +on the highest point of the plates, the shell becomes polyhedral +(dodecahedral?). + +_Dimensions._--Diameter of the shell 0.15 to 0.17, of the parmal meshes +0.02 to 0.025, sutural meshes 0.01 to 0.03, bars 0.002. + +_Habitat._--Equatorial Atlantic, Station 347, surface. + + +2. _Tessaraspis pentagonalis_, n. sp. + +Parmal meshes pentagonal, three to four times as broad as the thick bars, +and on an average smaller than the irregular polygonal sutural meshes. +Radial spines stout, quadrangular; their outer pyramidal part shorter than +the inner prismatic part. + +_Dimensions._--Diameter of the shell 0.12, of the parmal pores 0.01 to +0.012, bars 0.003. + +_Habitat._--Central Pacific, Station 269, surface. + + +3. _Tessaraspis tetragonalis_, n. sp. + +Parmal meshes tetragonal, or nearly square, six to eight times as broad as +the thin bars, and on an average larger than the irregular polygonal +sutural meshes. Radial spines thin, quadrangular, prismatic, their outer +part longer than their inner. + +_Dimensions._--Diameter of the shell 0.16, of the parmal pores 0.012 to +0.016, bars 0.002. + +_Habitat._--South Pacific, Station 288, surface. + + +4. _Tessaraspis hexagonalis_, n. sp. + +Parmal meshes hexagonal, ten to twelve times as broad as the thin bars, and +on an average larger than the polygonal sutural meshes (the two proximal +sides of each hexagonal parmal mesh two to three times as long as the four +distal sides). Radial spines cylindrical, thin; their outer part longer +than the inner. + +_Dimensions._--Diameter of the shell 0.15, of the parmal pores 0.01 to +0.015, bars 0.001. + +_Habitat._--North Pacific, Station 254, surface. + + +5. _Tessaraspis trigonalis_, n. sp. + +Parmal meshes triangular, three to four times as broad as the thick bars, +and on an average smaller than the irregular sutural meshes (in each plate +all four parmal meshes of the same size, formed like an isosceles triangle, +the distal base of which is somewhat curved, and convex towards {837}the +periphery, whilst the two proximal sides are straight). Radial spines +thick, rounded; their outer conical part shorter than the inner cylindrical +part. + +_Dimensions._--Diameter of the shell 0.1, of the parmal pores 0.01, of the +sutural pores 0.01 to 0.02. + +_Habitat._--Tropical Atlantic (near Ascension), Station 345, depth 2010 +fathoms. + + +6. _Tessaraspis circularis_, n. sp. + +Parmal meshes circular, all eighty of equal size, quite regular, five to +six times as broad as the thick bars, on an average larger than the +roundish irregular sutural meshes. Radial spines quadrangular, prismatic, +the outer part longer than the inner. + +_Dimensions._--Diameter of the shell 0.18, parmal pores 0.015 to 0.018, +bars 0.003. + +_Habitat._--South-east Pacific, Station 300, surface. + + +7. _Tessaraspis micropora_, n. sp. + +Parmal meshes circular, very small, all eighty of the same size, regular, +scarcely as broad as the separating thick bars, and much smaller than the +large irregular sutural meshes. Radial spines rounded, their outer conical +part about as long as the inner cylindrical part. + +_Dimensions._--Diameter of the shell 0.08, of the parmal pores 0.003, of +the sutural pores 0.005 to 0.015, bars 0.004. + +_Habitat._--Western Tropical Pacific, Station 225, surface. + + +8. _Tessaraspis diodon_, Haeckel. + + _Dorataspis diodon_, Haeckel, 1862, Monogr. d. Radiol., p. 417, Taf. + xxii. figs. 1-5. + +Parmal meshes roundish, for the most part nearly circular, three to four +times as broad as the bars, and on an average smaller than the roundish +sutural meshes. Radial spines in the inner part cylindrical; the outer part +very short (only one-third or one-fourth of the radius), divided completely +into two parallel conical pointed teeth by a deep incision. + +_Dimensions._--Diameter of the shell 0.12, of the parmal pores 0.01 to +0.012, of the sutural pores 0.01 to 0.03, bars 0.004. + +_Habitat._--Mediterranean (Messina), surface. + + +9. _Tessaraspis quadriforis_, n. sp. + +Parmal meshes irregular, roundish, of nearly equal size, four to six times +as broad as the bars, and on an average of the same size as the roundish +sutural meshes. Radial spines quadrangular, prismatic in the inner part, +which is somewhat longer than the conical outer part. + +_Dimensions._--Diameter of the shell 0.16, of the pores 0.012 to 0.018, +bars 0.003. + +_Habitat._--North Atlantic, Canary and Cape Verde Islands, Station 353, +surface. + + +{838}10. _Tessaraspis irregularis_, n. sp. + +Parmal meshes irregular, roundish, of unequal size, three to six times as +broad as the bars, and on an average larger than the irregular sutural +meshes. Radial spines cylindrical, the outer part longer than the inner +part. + +_Dimensions._--Diameter of the shell 0.13, parmal pores 0.006 to 0.012, +sutural pores 0.005 to 0.01; bars 0.002. + +_Habitat._--Central Pacific, Station 270, surface. + + + +Subgenus 2. _Tessaraspidium_, Haeckel. + +_Definition._--Condyles of the neighbouring plates grown together and +sutures obliterated; therefore the whole shell forms a single piece of +acanthin. + + +11. _Tessaraspis quadrata_, n. sp. + + _Tessaraspidium quadratum_, Haeckel, 1882, Manuscript. + +Parmal meshes square, four times as broad as the thin bars, on an average +of the same size as the polygonal sutural meshes. Radial spines stout, +tetrapterous, prismatic, in the outer part longer than in the inner. +Sutures of the shell completely obliterated, therefore the whole shell +forms one piece. + +_Dimensions._--Diameter of the shell 0.16, of the parmal pores 0.012, +sutural pores 0.01 to 0.015. + +_Habitat._--South Atlantic, Station 332, depth 2200 fathoms. + + +12. _Tessaraspis rotunda_, n. sp. + +Parmal meshes circular, of equal size, twice as broad as the thick bars, on +an average smaller than the roundish sutural meshes. Radial spines +cylindrical in the inner part, which is somewhat longer than the outer +conical part. Sutures of the shell completely obliterated, therefore the +whole shell forms one piece. + +_Dimensions._--Diameter of the shell 0.12, parmal pores 0.008, sutural +pores 0.005 to 0.015. + +_Habitat._--North Atlantic, Station 354, surface. + + +13. _Tessaraspis concreta_, n. sp. (Pl. 136 fig. 5). + +Parmal meshes irregular, polygonal or roundish, six to eight times as broad +as the narrow and high bars, much larger than the irregular sutural meshes. + Radial spines leaf-shaped, compressed, two-edged, pointed at both ends; +inner and outer part nearly of equal size. Shell very thick walled; meshes +therefore funnel-shaped; sutures completely obliterated, therefore the +whole shell forms a single piece. + +_Dimensions._--Diameter of the shell 0.09, parmal pores 0.02, sutural pores +0.01. + +_Habitat._--Central Pacific, Station 274, depth 2750 fathoms. + + + +{839}Genus 363. _Lychnaspis_,[403] Haeckel, 1862, Prodromus, p. 468. + +_Definition._--#Dorataspida# with twenty plates, which are perforated by +eighty aspinal pores (four crossed pores in each plate). Surface covered +with numerous by-spines. + +The genus _Lychnaspis_, the largest and most common of all Dorataspida, +exhibits the same structure of the shell as its ancestral form +_Tessaraspis_, and differs from it only in the development of by-spines on +the sutural condyles. Many species of this genus are very widely +distributed, and appear in large numbers, and some of them are amongst the +most graceful and elegant of the Radiolaria. + + + +Subgenus 1. _Lychnasparium_, Haeckel. + +_Definition._--Condyles of the neighbouring plates connected by permanent +open sutures; therefore the whole shell is composed of twenty separate +pieces of acanthin. + + +1. _Lychnaspis giltschii_, n. sp. (Pl. 135, fig. 3). + +Parmal meshes pentagonal, about ten or twelve times as broad as the thin +bars, on an average of the same size as the irregular polygonal sutural +meshes. By-spines (two hundred to three hundred) very delicate, half as +long as the radius, barbed, and zigzag. Radial main-spines very thin and +long, straight, cylindrical; their outer part longer than the inner part. + +_Dimensions._--Diameter of the shell 0.2, of the parmal pores 0.02, sutural +pores 0.01 to 0.03, bars 0.002. + +_Habitat._--Tropical Atlantic, Stations 338 to 348, surface. + + +2. _Lychnaspis capillaris_, n. sp. + +Parmal meshes pentagonal, twenty to thirty times as broad as the very thin +thread-like bars, on an average of the same size as the irregular polygonal +sutural meshes. By-spines (two hundred to two hundred and fifty) very +delicate, zigzag, with very small denticles, one-third as long as the +radius. Radial main-spines very thin and long, cylindrical, more or less +undulated. + +_Dimensions._--Diameter of the shell 0.25, parmal pores 0.025, sutural +pores 0.02 to 0.04, bars 0.001. + +_Habitat._--North Pacific, Station 250, surface. + + +3. _Lychnaspis maxima_, n. sp. + +Parmal meshes pentagonal, six to eight times as broad as the thick bars, +for the most part larger than the irregular sutural meshes. By-spines +(four hundred to five hundred) nearly as {840}long as the radius, +zigzag, with short denticles. Radial spines very long and stout, +quadrangularly-prismatic, with four smooth edges. + +_Dimensions._--Diameter of the shell 0.3, parmal pores 0.03, sutural pores +0.01 to 0.025, bars 0.004. + +_Habitat._--Central Pacific, Stations 271 to 274, surface. + + +4. _Lychnaspis serrata_, n. sp. + +Parmal meshes pentagonal, three to four times as broad as the thick bars, +smaller than the irregular sutural meshes. By-spines (two hundred to three +hundred) scarcely one-third as long as the radius, zigzag, with strong +denticles. Radial spines very long, stout, quadrangularly-prismatic, with +four serrated edges. + +_Dimensions._--Diameter of the shell 0.22, parmal pores 0.015, sutural +pores 0.012 to 0.03, bars 0.004. + +_Habitat._--South Atlantic, Station 330, surface. + + +5. _Lychnaspis wagenschieberi_, n. sp. + +Parmal meshes tetragonal, nearly rhombic, three to four times as broad as +the thick bars, smaller than the large irregular sutural meshes. By-spines +(about two hundred) large, as long as the radius, with long recurved +denticles, very zigzag. Radial main-spines very long, four-sided prismatic. +This species differs by the form and size of the spines, and by the square +form of the parmal pores from the similar _Lychnaspis polyancistra_, of +which the late excellent engraver Wagenschieber, of Berlin, has given such +a beautiful figure in my monograph (Taf. xxi. fig. 8). + +_Dimensions._--Diameter of the shell 0.16, parmal pores 0.014, sutural +pores 0.015 to 0.02, bars 0.004. + +_Habitat._--Central Pacific, Station 266, surface. + + +6. _Lychnaspis polyancistra_, Haeckel. + + _Dorataspis polyancistra_, Haeckel, 1862, Monogr. d. Radiol., p. 418, + Taf. xxi. figs. 7-9. + +Parmal meshes roundish, tetragonal, or nearly square, two to three times as +broad as the thick bars, smaller than the irregular sutural meshes. +By-spines (about two hundred) thin, half as long as the radius, zigzag, +with blunt denticles. Radial main-spines stout, in the inner half +cylindrical, in the outer half (of the same length) conical, pointed. + +_Dimensions._--Diameter of the shell 0.12, parmal pores 0.012, sutural +pores 0.01 to 0.04, bars 0.004. + +_Habitat._--Mediterranean (Messina), surface. + + +{841}7. _Lychnaspis rottenburgii_, n. sp. (Pl. 135, fig. 4). + +Parmal meshes roundish, about twice as broad as the thick bars, and for the +most part smaller than the irregular sutural meshes. By-spines (about two +hundred to two hundred and fifty) thin, zigzag, half as long as the radius. +Radial main-spines very strong, cylindrical in the inner half, in the outer +half much thicker and conical, pointed. I call this species in honour of my +learned friend, the great patron of zoological studies, Mr. Paul +Rottenburg, of Glasgow. + +_Dimensions._--Diameter of the shell 0.15, parmal pores 0.012, sutural +pores 0.01 to 0.03, bars 0.006. + +_Habitat._--Central Pacific, Station 270, depth 2925 fathoms. + + +8. _Lychnaspis undulata_, n. sp. (Pl. 135, fig. 2). + +Parmal meshes circular, twice as broad as the thick bars, on an average of +the same size as the irregular sutural meshes. By-spines (one hundred and +fifty to two hundred) very thin, barbed and zigzag, as long as the radius. +Radial main-spines cylindrical; their outer pointed part longer than the +inner part. + +_Dimensions._--Diameter of the shell 0.1, parmal pores 0.01, sutural pores +0.01, bars 0.005. + +_Habitat._--Tropical Atlantic, Station 343, surface. + + +9. _Lychnaspis longissima_, n. sp. (Pl. 134, fig. 6). + +Parmal meshes circular, very small, of the same breadth as the thick bars, +much smaller than the irregular sutural meshes. By-spines (one hundred to +one hundred and ten) very long and thin, zigzag, twice as long as the +diameter of the shell. Radial main-spines very long and strong, cylindrical +(at the base quadrangular, pyramidal), four to six times as long as the +diameter of the shell, and one fourth as thick as its radius. + +_Dimensions._--Diameter of the shell 0.08, parmal pores 0.002, sutural +pores 0.01 to 0.015, bars 0.003; length of the radial spines 0.3 to 0.5. + +_Habitat._--Tropical Pacific (Philippines), Stations 200 to 215, surface. + + +10. _Lychnaspis minima_, n. sp. (Pl. 134, figs. 2, 7, 8). + +Parmal meshes circular, very small, only half as broad as the thick bars, +much smaller than the irregular sutural meshes. By-spines (one hundred to +one hundred and ten) half as long as the radius, zigzag. Radial main-spines +thick, in the inner part cylindrical, in the outer shorter part conical, of +very variable size. + +_Dimensions._--Diameter of the shell 0.05, parmal pores 0.002, sutural +pores 0.006 to 0.012, bars 0.004. + +_Habitat._--Antarctic Ocean, Station 154, surface. + + + +{842}Subgenus 2. _Lychnaspidium_, Haeckel. + +_Definition._--Condyles of the neighbouring plates grown together and +sutures obliterated, therefore the whole shell forms a single piece of +acanthin. + + +11. _Lychnaspis echinoides_, Haeckel. + + _Haliomma echinoides_, J. Mueller, 1858, Abhandl. d. k. Akad. d. Wiss. + Berlin, p.36, Taf. v. figs. 3, 4. + + _Haliommatidium echinoides_, J. Mueller, 1858, Abhandl. d. k. Akad. d. + Wiss. Berlin, p. 22. + + _Haliommatidium echinoides_, Haeckel, 1862, Monogr. d. Radiol., p. 422. + +Parmal meshes pentagonal or somewhat roundish, four times as broad as the +bars, and of about the same size as the polygonal meshes. By-spines (about +two hundred) short, zigzag. Radial spines thin; their outer conical part +shorter than the inner cylindrical part. Sutures perfectly obliterated, but +recognisable by the characteristic pair of divergent by-spines. (Some +recent observations on this species, made during 1880 in Portofino, have +convinced me that the interpretation of it given in my Monograph, 1862, +_loc. cit._, was quite correct.) + +_Haliomma ligurinum_, J. Mueller (= _Haliommatidium ligurinum_, Haeckel, L. +N. 16, p. 423) seems to be closely allied to the preceding. + +_Dimensions._--Diameter of the shell 0.12 to 0.14, parmal pores 0.015, +sutural pores 0.01 to 0.02, bars 0.004. + +_Habitat._--Mediterranean, Nice, Saint Tropez (J. Mueller); Portofino near +Genoa (Haeckel). + + +12. _Lychnaspis haliommidium_, n. sp. + + _Lychnaspidium haliommidium_, Haeckel, 1882, Manuscript. + +Parmal meshes circular, twice as broad as the bars, smaller than the +irregular sutural meshes. By-spines (about two hundred) barbed and zigzag, +as long as the radius. Radial main-spines four-sided; their outer pyramidal +part shorter than the inner prismatic part. Sutures perfectly obliterated. + +_Dimensions._--Diameter of the shell 0.1, parmal pores 0.01, sutural meshes +0.015 to 0.02. + +_Habitat._--South Atlantic, Station 335, depth 1425 fathoms. + + +13. _Lychnaspis rabbeana_, n. sp. + +Parmal meshes circular, very small, of the same breadth as the bars, and +much smaller than the irregular sutural meshes. By-spines (about one +hundred) very long and thin, zigzag, about as long as the diameter of the +shell. Radial main-spines cylindrical, thick, twice to three times as long +as the diameter of the shell. Sutures perfectly obliterated, with thickened +condyles. Named in honour of Captain Henrik Rabbe (of Bremen), to whom I am +indebted for many new Indian and Atlantic Radiolaria. + +_Dimensions._--Diameter of the shell 0.086, parmal pores 0.002, sutural +pores 0.012, bars 0.002. + +_Habitat._--Indian Ocean (Madagascar), Rabbe, surface. + + +{843}14. _Lychnaspis cataplasta_, n. sp. + +Parmal pores very small, circular, half as broad as the bars, and much +smaller than the irregular sutural pores. By-spines zigzag, as long as the +diameter of the shell. Radial main-spines very thin and long, +needle-shaped, cylindrical, five to six times as long as the diameter of +the shell. Sutures perfectly obliterated. (This stunted species is one of +the smallest of the Dorataspida.) + +_Dimensions._--Diameter of the shell 0.05, parmal pores 0.0015, sutural +pores 0.01, bars 0.002. + +_Habitat._--Antarctic Ocean (off Kerguelen Island), Station 149, surface. + + + +Genus 364. _Icosaspis_,[404] Haeckel, 1881, Prodromus, p. 468. + +_Definition._--#Dorataspida# with twenty plates, which are perforated by +one hundred and sixty to three hundred or more parmal pores (in each plate +four crossed aspinal pores, and around them four to twelve or more coronal +pores). Surface without by-spines. + +The genus _Icosaspis_ and the closely allied _Hylaspis_ differ from all +other Tessaraspida in the increased number of the parmal pores. Whilst this +number in all other genera is eighty (only four crossed pores in each +plate), here it amounts to one hundred and sixty to three hundred or more +(sometimes more than a thousand); in each shield four primary, crossed +"aspinal pores" being surrounded by a circle of four to twelve or more +"coronal pores." The number of sutural pores in these two genera is also +increased. + + + +Subgenus 1. _Icosasparium_, Haeckel. + +_Definition._--Condyles of the neighboring plates connected by permanent +open sutures; therefore the whole shell composed of twenty separated pieces +of acanthin. + + +1. _Icosaspis tabulata_, n. sp. (Pl. 136, fig. 2). + +Parmal meshes all of nearly equal size and form, square, four times as +broad as the bars, little larger than the triangular or polygonal sutural +meshes. In each plate fifty to seventy (regularly sixty-four) quadrangular +pores, viz., four primary square aspinal meshes, forming together a regular +square surrounded by two to three coronas of rectangular (not quite +regular) coronal meshes (six to eight in each transverse row). Radial +spines tetrapterous, prismatic, with four thin and broad wings, from which +arise the crossed bars between the four primary pores. Outer part of the +spines longer than the inner. Commonly the condyles of the plates are only +contiguous; sometimes they grow together, and this form approaches +_Icosaspis tetragonopa_. + +_Dimensions._--Diameter of the shell 0.25 to 0.3, of the pores 0.02, bars +0.005. + +_Habitat._--North Pacific, Station 244, depth 2900 fathoms. + + +{844}2. _Icosaspis elegans_, n. sp. (Pl. 136, fig. 4; Pl. 134, fig. 9). + + _Tessaraspis elegans_, Haeckel, 1882, Manuscript et Atlas. + +Parmal meshes of very different size and form; in the centre of each plate +a cross of four primary, pear-shaped "aspinal pores" (the largest of all); +between them four secondary, little smaller, crossed, egg-shaped "angular +pores"; around this rosette of eight larger meshes an inner complete circle +of sixteen to twenty polygonal coronal pores, and an outer incomplete +circle of thirty to forty very small marginal pores. The latter are smaller +than the irregular sutural meshes, which are constricted in the middle, +about forty to sixty around each plate. Radial spines thin, cylindrical, or +a little compressed; their outer part longer than the inner. In this +elegant and very common species the condyles usually remain separated by +sutures; but sometimes the latter become obliterated, and the whole shell +then forms a single piece, _Icosaspidium elegans_. + +_Dimensions._--Diameter of the shell 0.2 to 0.3, commonly 0.25; larger +parmal pores 0.02, smaller 0.001 to 0.003; sutural pores 0.005 to 0.015; +bars 0.003. + +_Habitat._--Tropical and Subtropical Atlantic, Canary Islands to Ascension +Island, Stations 340 to 354, surface. + + +3. _Icosaspis cruciata_, n. sp. (Pl. 134, fig. 10). + +Parmal meshes very different; in the centre of each plate a cross of four +primary, nearly oblong, rectangular "aspinal pores"; between these four +secondary, triangular, egg-shaped "angular pores" (the largest of all), and +around this rosette a single circle of twelve to twenty-four small "coronal +pores." The latter are of about the same size as the irregular sutural +meshes, of which there are twenty to thirty around each plate. Radial +spines thin, cylindrical, or a little compressed; their outer part longer +than the inner. + +_Dimensions._--Diameter of the shell 0.2 to 0.3, commonly 0.25; larger +parmal pores 0.025, smaller 0.005 to 0.01; bars 0.005. + +_Habitat._--Tropical and Subtropical Pacific, Sandwich to Marquesas +Islands, Stations 256 to 274, surface. + + +4. _Icosaspis ornata_, n. sp. + +Parmal meshes very different; in the centre of each plate a cross of four +primary octagonal aspinal pores (the largest of all); between them four +secondary, rhombic angular pores, and around this rosette a circle of +twelve to sixteen smaller, polyhedral coronal pores, which are however +larger than the irregular sutural pores (surrounding each plate to the +number of twenty to thirty). Radial spines thin, quadrangular, prismatic; +the outer part longer than the inner. + +_Dimensions._--Diameter of the shell 0.25; larger parmal pores 0.03, +smaller 0.01; sutural pores 0.004 to 0.008; bars 0.006. + +_Habitat._--South Pacific, Station 295, depth 1500 fathoms. + + +{845}5. _Icosaspis spectabilis_, n. sp. + +Parmal meshes very different; in the centre of each plate four very large, +pentagonal aspinal pores, and around these two to three circles of smaller +polygonal coronal pores, which are very numerous, and not larger than the +small sutural pores. Radial spines quadrangular, prismatic, stout, very +long; the outer part two to three times as long as the inner. + +_Dimensions._--Diameter of the shell 0.4, of the larger aspinal meshes +0.03, of the outer meshes 0.002 to 0.02, bars 0.005. + +_Habitat._--South Atlantic, Station 333, surface. + + +6. _Icosaspis multiforis_, n. sp. + +Parmal meshes very numerous, more than one hundred in each plate; in the +centre four larger pear-shaped pores, and around these four to five circles +of smaller pores, gradually smaller towards the margin of the plate; the +sutural meshes also very small and numerous (more than fifty around each +plate), so that the number of all the pores together amounts to two +thousand or even more. Radial spines thin, cylindrical, very long. + +_Dimensions._--Diameter of the shell 0.32; larger aspinal pores 0.02, +smaller 0.002 to 0.01; bars 0.003. + +_Habitat._--Indian Ocean (Madagascar), Rabbe, surface. + + + +Subgenus 2. _Icosaspidium_, Haeckel. + +_Definition._--Condyles of the neighbouring plates grown together, and +sutures obliterated; therefore the whole shell forms a single piece of +acanthin. + + +7. _Icosaspis tetragonopa_, Haeckel. + + _Haliommatidium tetragonopum_, Haeckel, 1862, Monogr. d. Radiol., p.421, + Taf. xxii. fig. 13. + +Parmal meshes all of nearly equal size and form, square, three times as +broad as the bars, little larger than the sutural meshes. In each plate +commonly sixteen equal square meshes, viz., four primary aspinal and twelve +secondary, surrounding the former as a square corona. Radial spines +tetrapterous, stout; the outer pyramidal half somewhat longer than the +inner. This species differs from the similar _Icosaspis tabulata_ (Pl. 136, +fig. 2) in the concrescence of the sutures, the smaller number of pores, +and the form of the stouter spines. The figure in my Monograph, drawn from +a broken fragment, is not quite correct. + +_Dimensions._--Diameter of the shell 0.18, pores 0.009, bars 0.003. + +_Habitat._--Mediterranean (Messina, Corfu), surface. + + +8. _Icosaspis icosahedra_, n. sp. + +Parmal meshes of different size and form; in the centre of each plate a +cross of four pentagonal, primary aspinal pores, surrounded by a complete +corona of twelve to sixteen polygonal coronal {846}pores and an incomplete +corona of thirty to forty very small marginal pores; the latter are not to +be distinguished from the pores of the obliterated sutures. Radial spines +quadrangular, the outer pyramidal part shorter than the inner prismatic +part. Condyles grown together. As the plates are quite even, the shell +becomes icosahedral. + +_Dimensions._--Diameter of the shell 0.16, pores 0.002 to 0.02, bars 0.005. + +_Habitat._--North Pacific, Station 241, surface. + + +9. _Icosaspis icosastaura_, n. sp. (Pl. 136, fig. 3). + + _Tessaraspis icosastaura_, Haeckel, 1882, Manuscript et Atlas. + +Parmal plates of different size and form; in the centre of each plate a +cross of four larger primary, pyriform aspinal pores; between these four +smaller roundish angular pores, and around this rosette a circle of ten to +twenty (commonly sixteen) coronal pores, little larger than the very small +sutural pores. Radial spines very thin and long, cylindrical or +bristle-shaped. Condyles grown together; no suture visible. + +_Dimensions._--Diameter of the shell 0.14; larger pores of the cross 0.01, +smaller pores 0.002 to 0.008; bars 0.002 to 0.004. + +_Habitat._--Central Pacific, Station 268, surface. + + + +Genus 365. _Hylaspis_,[405] n. gen. + +_Definition._--#Dorataspida# with twenty plates, which are perforated by +one hundred and sixty to three hundred or more parmal pores (in each plate +four crossed aspinal pores, and around them four to twelve or more coronal +pores). Surface covered with numerous by-spines. + +The genus _Hylaspis_ exhibits the same structure of the shell as the nearly +allied ancestral genus _Icosaspis_, and differs from it only in the +development of by-spines. Some species of these two genera exhibit the +highest degree of complication in the structure of the shell seen among the +Dorataspida. + + +1. _Hylaspis serrulata_, n. sp. (Pl. 135, fig. 1). + +Parmal meshes four hundred to five hundred; in the centre of each plate a +cross of four very large pentagonal or roundish aspinal pores, and around +this a circle of sixteen to twenty much smaller irregular, polygonal, +coronal pores; the latter of about the same size as the sutural pores. On +each condyle one thin zigzag-shaped by-spine, nearly as long as the radius. +Twenty radial spines very long, quadrangular, prismatic; on the inside +thinner and smooth, on the outside thickened, and armed with four rows of +recurved teeth, serrated. + +_Dimensions._--Diameter of the shell 0.18, aspinal spines 0.02, other pores +0.002 to 0.01, bars 0.003. + +_Habitat._--South Atlantic, Station 326, surface. + + +{847}2. _Hylaspis coronata_, n. sp. + +Parmal meshes five hundred to six hundred; in the centre of each plate a +cross of four long rectangular aspinal pores, between these four larger +egg-shaped angular pores; around this rosette a circle of sixteen to twenty +much smaller, irregular, roundish, coronal pores; the latter about of the +same size as the sutural pores. On each condyle one bearded by-spine about +one-third or one-fourth as long as the radius. Twenty radial spines, very +long, smooth, quadrangular, prismatic. + +_Dimensions._--Diameter of the shell 0.25, aspinal pores 0.02, other pores +0.005 to 0.01, bars 0.004. + +_Habitat._--Central Pacific, Station 271, surface. + + +3. _Hylaspis barbata_, n. sp. + +Parmal meshes twelve hundred to sixteen hundred; in the centre of each +plate a cross of four large, somewhat oblong, octahedral aspinal pores, +between these four rhombic smaller angular pores; around this rosette an +inner circle of twelve to sixteen larger and an outer circle of fifty to +sixty very small coronal pores; the latter smaller than the sutural pores. +On each condyle one bristle-shaped zigzag by-spine, with recurved thin +hooks, half as long as the radius. Twenty radial spines, very long, +cylindrical, smooth. + +_Dimensions._--Diameter of the shell 0.25 to 0.3, aspinal pores 0.022, +other pores 0.002 to 0.015, bars 0.002. + +_Habitat._--South Pacific, Station 295, surface. + + + +Family XLI. #PHRACTOPELTIDA#, Haeckel (Pl. 133, figs. 1-6). + +_Phractopeltida_, Haeckel, 1881, Prodromus, p. 468. + +_Definition._--ACANTHARIA with double spherical lattice-shell, composed of +the branched apophyses of twenty radial spines meeting in its centre, and +disposed according to the Muellerian law of Icosacantha. Central capsule +spherical, enclosing the inner and surrounded by the outer concentric +shell. + +The family #Phractopeltida# differs from all other ACANTHARIA in the +development of a double spherical shell, composed of two concentric +lattice-spheres, which are united by twenty radial spines meeting in the +common centre. We could therefore oppose the Phractopeltida as +_Diplophracta_ to all other #Acanthophracta# as _Haplophracta_ (with simple +shell). The former exhibit a relation to the latter, similar to that +exhibited by the Dyosphaerida to the simple Monosphaerida among the +#Sphaeroidea#. + +In my Monograph (1862, p. 423) I described only one genus appertaining to +this family, _Aspidomma_. I founded it upon the singular _Phractopelta_, +described by {848}J. Mueller as _Haliomma hystrix_. A second species of +_Aspidomma_, the _Acanthometra mucronata_ of J. Mueller, was probably an +_Astrolonche_. At that time I placed _Aspidomma_ among the Haliommatida, +led by the erroneous opinion that it might represent a transition-form +between _Dorataspis_ and _Haliomma_. But I afterwards gave up this view, as +I was convinced that there is no true phylogenetic connection between the +acanthinic Dorataspida (_Actipylea_) and the siliceous Haliommatida +(_Peripylea_). Therefore in my Prodromus (1881, p. 468) I placed +_Aspidomma_ among the Dorataspida and changed its name to _Phractopelta_, +to avoid further confusion with the unrelated Ommatida (#Sphaeroidea#). It +formed there, with three nearly related genera, the "subfamily +Phractopeltida," which we now advance to the higher rank of a separate +family. (By a typographical mistake the words are printed in the Prodromus +_Phractopelma_ and Phractopelmida, &c., instead of _Phractopelta_ and +Phractopeltida, &c.). The detection of other new species appertaining to +this family, and a closer anatomical investigation of them, has now led to +the distinction of five different genera, characterised by other +differences than were employed in 1881 in the provisional system of the +"Prodromus." + +The two concentric spherical lattice-shells of the Phractopeltida, +connected by radial beams, correspond perfectly to those of the +double-shelled Dyosphaerida (_Haliomma_, _Diplosphaera_, &c.), and in both +cases we may call the smaller inner the "medullary shell," and the larger +outer the "cortical shell." There is no doubt that the double-shelled +Phractopeltida must be derived phylogenetically from the simple-shelled +Dorataspida (just as we derive the double Dyosphaerida from the simple +Monosphaerida). But it is not yet possible to decide positively which of +the two shells is the first formed. Probably the small inner or medullary +shell of the Phractopeltida is the first formed, and corresponds to the +simple spherical lattice-shell of the Dorataspida; and the larger outer or +cortical shell of the former is a later new formation, absent in the latter +family. This opinion seems to be confirmed by the genus _Orophaspis_, the +only form among the Dorataspida, in which the radial spines outside the +shell bear free latticed apophyses. If these twenty apophyses grow further +and meet one another, the second or outer shell of _Phractopelta_ may be +formed. But some objections may be raised to this opinion from the peculiar +structure and the very small size of the inner shell; and there is some +possibility that this latter is a secondary later product inside of the +primary cortical shell. The probably phylogenetic series which reveals the +origin of the Phractopeltida is the following:--_Acanthometron_, +_Zygacantha_, _Lithophyllium_, _Phractacantha_, _Doracantha_, _Dorataspis_, +_Orophaspis_, _Phractopelta_. + +The twenty radial spines exhibit in all Phractopeltida the same +characteristic position and relation as in all other Icosacantha, and are +constantly arranged according to the Muellerian law in four meridian +planes, their distal ends falling into five parallel zones. Their +distinction in the majority of the Phractopeltida is not difficult, +{849}since the spines of the different zones bear apophyses of different +shapes. Sometimes the four equatorial spines are stouter than the sixteen +other spines, and often the eight tropical spines are somewhat different in +form from the eight polar and from the four equatorial spines. The length +of all twenty spines is commonly equal. Their form is usually more or less +compressed, two-edged (as in _Zygacantha_), more rarely cylindrical (as in +_Acanthometron_), or somewhat quadrangular (but not truly prismatic); +therefore the transverse section of the spines is commonly elliptical or +lanceolate, rarely circular or rhombic, never square; this seems to +indicate their origin from _Zygacantha_. As in all ACANTHARIA, the spines +consist of acanthin, not of silex. Their central ends are either perfectly +grown together, and form a single star of acanthin, or the triangular faces +of their small pyramidal bases are supported one upon another, without true +concrescence. + +The apophyses of the radial spines, by which the two concentric spherical +shells are formed, seem to be constantly four on each spine, two being +opposite in each shell. The proximal pair of opposite apophyses, forming +the inner or medullary shell, is constantly much smaller than the distal +pair composing the outer or cortical shell (Pl. 133, fig. 5). The proximal +pair corresponds probably to the two primary apophyses of the Diporaspida +(_Phractaspis_, _Dorataspis_, &c.), whilst the distal pair corresponds to +the free apophyses of _Orophaspis_ (Pl. 133, fig. 6). Therefore the +Phractopeltida may be derived phylogenetically from the Diporaspida (not +from the Tessaraspida). In the common ancestral genus of this family, +_Phractopelta_, the free part of the radial spines (outside the outer +shell) is quite simple, without free apophyses; in all other genera of the +family that free part of the spines (either in all twenty spines or only in +some of them) bears a third pair of lateral apophyses; these may be either +simple or branched or even latticed; but the outer apophyses (of the third +rank) remain constantly free, and a third lattice-shell is never formed by +union of their edges (Pl. 133, figs. 2-4). + +The inner lattice-shell of the Phractopeltida, or their "medullary shell," +is constantly very small (commonly 0.03 to 0.05 mm. in diameter, rarely +more). Its structure is difficult to make out; in the unbroken shell it is +concealed by the dense network of the outer shell; in the broken shell it +is commonly destroyed. Usually the pores of the inner shell are very small, +circular or subcircular, scarcely as broad as the small separating bars. In +the majority of Phractopeltida their number seems to be about forty, being +probably the forty primary aspinal pores of the Diporaspida; in some +species this number seems to be exceeded, so that perhaps some sutural +pores may exist between the aspinal pores; but commonly the twenty plates +composing the inner shell (each with two aspinal pores) seems to grow +together perfectly by their meeting edges, so that there are no sutural +pores between them. Evident sutures were not recognisable in the inner +shell of any Phractopeltida. + +{850}The outer lattice-shell of the Phractopeltida, or their "cortical +shell," is at least twice as broad, commonly about three times as broad, as +the enclosed inner shell; it is much more varied in composition than the +latter. Like the greater part of the Dorataspida we may distinguish here in +the lattice-work two kinds of pores--parmal pores and sutural pores. The +parmal pores are produced by the union of the meeting branches of the +apophyses of each single spine, and are therefore visible on each isolated +spine; whilst the sutural pores are formed by the meeting branches of the +apophyses of neighbouring spines. The distinction of the parmal and the +sutural pores, easy in most Dorataspida, is difficult in most +Phractopeltida, because the sutures between the meeting branches are +usually very early obliterated. However, the place of the obliterated +suture is often indicated by the thickened condyles of the apophyses on +both sides of the suture. Commonly also the form of the sutural pores is +much more irregular than that of the parmal pores; the former are more or +less constricted in the middle by the intumescence of the sutural condyles, +whilst the latter are more roundish, elliptical, kidney-shaped, or square. +The number of the pores in the outer shell in the typical normal form of +Phractopeltida seems to be the same as in the most species of _Dorataspis_, +_Diporaspis_, &c., between ninety and one hundred, viz., forty parmal pores +and from fifty to sixty sutural pores. However, in many species this number +is increased. Since in all Phractopeltida, each of the twenty plates is +composed only of the meeting branches of two opposite apophyses, we find +originally in each plate only two primary parmal pores or "aspinal pores." +But in some species there occur four, six, or more pores in each plate; in +this case two of them only are aspinal pores, all the others being "coronal +pores." Moreover, in those species which exhibit on the base of each spine +in the outer shell four crossed pores (Pl. 133, fig. 2), there are not four +equivalent aspinal pores (as in the Tessaraspida), but the two opposite are +primary or aspinal pores and the other two (different from them in size and +form) coronal pores. However, the number of coronal pores in the +Phractopeltida is never so large as in many Dorataspida, and the same holds +good also for the increasing number of the irregular sutural pores. In none +of the species observed does the total number of the pores in the outer +shell reach two hundred. + +The original mode of development of the apophyses composing the outer shell +seems to be imitated by the free apophyses of the third order, which are +developed from the radial spines outside the outer shell in all +Phractopeltida, with the single exception of the simple ancestral genus +_Phractopelta_. These apophyses of the third rank are also originally +constantly two, opposite to one another (after the type of _Lithophyllium_, +_Dorataspis_, &c.). Commonly they do not remain simple, but become +branched, and by communication of the neighbouring branches small +lattice-plates arise. Originally each of these free lattice-plates has only +two parmal pores, but the number of the parmal pores increases afterwards, +so that we may distinguish two (primary) {851}aspinal pores, and two, +four, or more (secondary) coronal pores. In the majority of species the two +opposite apophyses are first crossed at right angles by a transverse beam, +and the two parallel transverse beams are again crossed by perpendicular +tertiary branches (again parallel to the apophyses). In this case the +network of the free lattice-plates becomes more or less rectangular. But in +other species the ramification of the apophyses assumes more the form of +bifurcation or of irregular branching. As already said, the neighbouring +free lattice-plates of this third order never meet, and therefore a +complete third shell is never formed. + +The different genera of Phractopeltida exhibit very remarkable differences +in the development of free apophyses (or lattice-plates of the third +order). Whilst in the numerous species of the ancestral genus +_Phractopelta_ all twenty spines remain simple, without such apophyses, +only in a single observed species (representing the genus _Pantopelta_) +were all twenty spines protected by them. In the three other genera only +one part of the spines bears free apophyses, but not the other part. The +most frequent form is _Dorypelta_ (Pl. 133, fig. 2); here eight spines are +simple (four equatorial and four polar spines of the hydrotomical plane), +whilst twelve spines bear apophyses (eight tropical and four polar spines +of the geotomical plane). In _Octopelta_ the eight tropical spines only +bear apophyses, whilst the twelve other (four equatorial and eight polar) +are simple. In _Stauropelta_ finally the four equatorial spines only are +simple, whilst the sixteen other bear free apophyses (eight tropical and +eight polar spines). + +_The Central Capsule_ of the Phractopeltida is constantly spherical, and +enclosed between the two concentric spherical shells; it is therefore +larger than the inner and smaller than the outer shell. Its wall is pierced +by the twenty radial beams connecting the two shells. The shape of the +central capsule and of the enveloping calymma is the same as in the other +#Acanthophracta# and specially in the Dorataspida. + +_Synopsis of the Genera of Phractopeltida._ + + {All twenty spines without + { apophyses in the free + All twenty spines of the { external part, 366. _Phractopelta_. + same form, { + {All twenty spines with + { apophyses in the free + { part, 367. _Pantopelta_. + + {Eight tropical spines with + { apophyses, twelve others + { (eight polar and four + { equatorial) simple, 368. _Octopelta_. + { + {Twelve radial spines + Twenty radial spines, { (eight tropical and four + partly without, partly { polar) with apophyses, + with apophyses in the { eight others (four polar + free external part, { and four equatorial) + { simple, 369. _Dorypelta_. + { + {Sixteen radial spines + { (eight tropical and + { eight polar) with + { apophyses, four + { equatorial, simple, 370. _Stauropelta_. + + + +{852}Genus 366. _Phractopelta_,[406] Haeckel, 1881, Prodromus, p. 468. + +_Definition._--#Phractopeltida# with twenty simple radial spines, bearing +no free apophyses outside the outer shell. + +The genus _Phractopelta_ is the most simple form among the Phractopeltida, +and may be regarded as the common ancestral form of this family. All twenty +spines are of nearly equal form and size, and bear no free apophyses on +their free part, outside the two concentric shells. _Phractopelta_ may be +derived from _Orophaspis_ by further development of the free apophyses, +which by union of their branches form a second outer shell around the +primary shell of that Dorataspid. + + + +Subgenus 1. _Phractopeltaris_, Haeckel. + +_Definition._--Outer shell composed of twenty separated plates, the sutures +of their meeting condyles not being grown together. + + +1. _Phractopelta dorataspis_, n. sp. (Pl. 133, fig. 1). + +Outer shell composed of twenty plates, the meeting condyles of which are +separated by permanent sutures. Each plate commonly with two elliptical +aspinal pores, which are two to three times as broad as the irregular +sutural pores. Radial spines (in the outer free part) compressed, linear, +twice as long as the diameter of the shell. + +_Dimensions._--Diameter of the outer shell 0.11, of the inner 0.05. + +_Habitat._--North Pacific (off Japan), Station 239, surface. + + +2. _Phractopelta dyadopora_, n. sp. + +Outer shell composed of twenty plates, the meeting condyles of which are +separated by permanent sutures. Each plate commonly with two kidney-shaped +aspinal pores, which are three to four times as broad as the irregular +sutural pores. Radial spines conical, about as long as the radius of the +shell. + +_Dimensions._--Diameter of the outer shell 0.08, of the inner 0.04. + +_Habitat._--North Pacific, Station 256, surface. + + +3. _Phractopelta diporaspis_, n. sp. + +Outer shell composed of twenty plates, the meeting condyles of which are +separated by permanent sutures. Each plate commonly with two quadrangular +aspinal pores, which are four to five times {853}as broad as the irregular +sutural pores. Radial spines compressed, sword-shaped, about as long as the +diameter of the shell. + +_Dimensions._--Diameter of the outer shell 0.09, of the inner 0.04. + +_Habitat._--South Atlantic, Station 332, surface. + + +4. _Phractopelta tessaraspis_, n. sp. + +Outer shell composed of twenty plates, the meeting condyles of which are +separated by permanent sutures. Each plate commonly with four crossed, +quadrangular, aspinal pores, the two opposite of which are much larger than +the two others. Sutural pores small, roundish. Radial spines compressed, +linear, about twice as long as the diameter of the shell. + +_Dimensions._--Diameter of the outer shell 0.084, of the inner 0.032. + +_Habitat._--North Pacific (off Japan), Station 238, surface. + + +5. _Phractopelta tetradopora_, n. sp. + +Outer shell composed of twenty plates, the meeting condyles of which are +separated by permanent sutures. Each plate commonly with four crossed +quadrangular (or nearly circular) aspinal pores, all of nearly the same +size. Sutural pores polygonal or roundish. Radial spines cylindrical, two +to three times as long as the diameter of the shell. + +_Dimensions._--Diameter of the outer shell 0.11, of the inner 0.045. + +_Habitat._--North Pacific, Station 253, surface. + + +6. _Phractopelta hexadopora_, n. sp. + +Outer shell composed of twenty plates, the meeting condyles of which are +separated by permanent sutures. Each plate commonly with six aspinal pores, +the two opposite of which are much larger than the four others. Sutural +pores small, roundish. Radial spines compressed, two-edged, larger than the +diameter of the shell. + +_Dimensions._--Diameter of the outer shell 0.1, of the inner 0.04. + +_Habitat._--Central Pacific, Station 272, surface. + + +7. _Phractopelta octadopora_, n. sp. + +Outer shell composed of twenty plates, the meeting condyles of which are +separated by permanent sutures. Each plate commonly with eight aspinal +pores, the four crossed being larger than the four others alternating with +them. Sutural pores irregular. Radial spines conical, shorter than the +diameter of the shell. + +_Dimensions._--Diameter of the outer shell 0.12, of the inner 0.04. + +_Habitat._--Indian Ocean (Cocos Islands, surface), Rabbe. + + + +{854}Subgenus 2. _Phractopeltidium_, Haeckel. + +_Definition._--Outer shell composed of twenty united plates, the sutures of +their meeting condyles being grown together. + + +8. _Phractopelta aspidomma_, n. sp. + +Outer shell composed of twenty united plates, the meeting condyles of which +are grown together. On the base of each radial spine (where its outer free +part arises from the surface of the outer shell), two large elliptical +aspinal pores, two to four times as large as the other roundish pores. +Radial spines compressed, sword-shaped, about as long as the radius of the +shell. + +_Dimensions._--Diameter of the outer shell 0.1, of the inner 0.05. + +_Habitat._--Equatorial Atlantic, Station 347, surface. + + +9. _Phractopelta haliomma_, n. sp. + +Outer shell composed of twenty united plates, the meeting condyles of which +are grown together. On the base of each radial spine two large +kidney-shaped aspinal pores, little larger than the other irregular pores. +Radial spines compressed, linear, two-edged, much longer than the diameter +of the shell. + +_Dimensions._--Diameter of the outer shell 0.09, of the inner 0.03. + +_Habitat._--South Pacific, Station 295, surface. + + +10. _Phractopelta tessaromma_, Haeckel. + +Outer shell composed of twenty united plates, the meeting condyles of which +are grown together. On the base of each radial spine four crossed +egg-shaped aspinal pores, two opposite of which are much larger than the +two others. Sutural pores irregular. Radial spines cylindrical or little +compressed, thin, longer than the diameter of the shell. + +_Dimensions._--Diameter of the outer shell 0.1, of the inner 0.04. + +_Habitat._--Central Pacific, Station 266, surface. + + +11. _Phractopelta hystrix_, Haeckel. + + _Haliomma hystrix_, J. Mueller, 1858, Abhandl. d. k. Akad. d. Wiss. + Berlin, p. 37, Taf. v. figs. 1, 2. + + _Aspidomma hystrix_, Haeckel, 1862, Monogr. d. Radiol., p. 424. + +Outer shell composed of twenty united plates, the meeting condyles of which +are grown together. On the base of each radial spine four crossed circular +aspinal spines of equal size. Sutural pores roundish, of about the same +size. Radial spines conical, about as long as the radius of the shell. + +_Dimensions._--Diameter of the outer shell 0.07, of the inner 0.024. + +_Habitat._--Mediterranean (Nice), J. Mueller, surface. + + + +{855}Genus 367. _Pantopelta_,[407] n. gen. + +_Definition._--#Phractopeltida# with twenty radial spines, each of which is +protected by two free external apophyses. + +The genus _Pantopelta_ differs from all other Phractopeltida in the +development of free protecting apophyses on all twenty radial spines. Only +a single specimen of this rare form was seen, and in this all twenty spines +exhibited no marked differences in form and size, but were more or less +irregularly developed. + + +1. _Pantopelta icosaspis_, n. sp. (Pl. 133, fig. 4). + +Apophyses of all twenty radial spines with forked anastomosing branches, +forming a more or less irregular cup-like fenestrated shield, pierced by a +variable number of pores. Distance of the apophyses from the outer shell +equal to half its radius. Pores of the outer shell irregular, roundish, +four to six times as broad as those of the inner shell. Radial spines +compressed, sword-shaped, longer than the radius of the shell. + +_Dimensions._--Diameter of the outer shell 0.08, of the inner 0.03. + +_Habitat._--Antarctic Ocean, Station 157, depth 1950 fathoms. + + + +Genus 368. _Octopelta_,[408] n. gen. + +_Definition._--#Phractopeltida# with twelve simple spines (four equatorial +and eight polar), and with eight tropical spines protected by external free +apophyses. + +The genus _Octopelta_ differs from the other Phractopeltida in the +possession of eight shields or pairs of free apophyses outside the outer +lattice-shell; the spines bearing these apophyses are the eight tropical +spines. The twelve other spines (eight polar and four equatorial) are quite +simple, without apophyses. + + +1. _Octopelta cultella_, n. sp. + +Apophyses of the eight tropical spines simple, compressed, knife-shaped, +about as long as their distance from the outer shell. On the base of each +spine (in the network of the outer shell) two orthogonal aspinal pores, two +to three times as long as the other polygonal pores. + +_Dimensions._--Diameter of the outer shell 0.08, of the inner 0.03. + +_Habitat._--Tropical Atlantic, Station 338, surface. + + +{856}2. _Octopelta furcella_, n. sp. + +Apophyses of the eight tropical spines forked, each with two parallel +simple fork-branches, about as long as their distance from the outer shell. +On the base of each spine (in the outer shell) two kidney-shaped aspinal +pores, about twice as broad as the other irregular pores. + +_Dimensions._--Diameter of the outer shell 0.1, of the inner 0.04. + +_Habitat._--South Atlantic (off Tristan d'Acunha), Station 332, surface. + + +3. _Octopelta scutella_, n. sp. (Pl. 133, fig. 5). + +Apophyses of the eight tropical spines crossed by a transverse beam, which +is again crossed by two perpendicular branches; by union of these branches +each tropical spine forms a square shield with four crossed pores and +twelve to sixteen marginal spikes. On the base of each spine (in the +surface of the outer shell) four crossed aspinal pores which correspond to +those of the free shields; these are somewhat larger than the other pores. + +_Dimensions._--Diameter of the outer shell 0.12, of the inner 0.06. + +_Habitat._--Tropical Atlantic, Station 348, surface. + + + +Genus 369. _Dorypelta_,[409] Haeckel, Prodromus, p. 369. + +_Definition._--#Phractopeltida# with eight simple spines (four equatorial +and four hydrotomical polar spines) and with twelve spines protected by +external free apophyses (eight tropical and four geotomical polar spines). + +The genus _Dorypelta_, the most common of all Phractopeltida which are +protected by free apophyses, exhibits a very peculiar differentiation of +its twenty radial spines. There are constantly eight simple spines and +twelve spines with apophyses. The eight simple spines are the four +equatorial spines and four polar spines placed in the hydrotomical median +plane. The four other polar spines (placed in the geotomical meridian +plane) and the eight tropical spines are protected by two opposite +apophyses, which are now simple, now branched or shield-shaped. A similar +differentiation occurs in no other Acanthophractida. + + + +Subgenus 1. _Dorypeltarium_, Haeckel. + +_Definition._--Free apophyses of the radial spines simple, not branched. + + +{857}1. _Dorypelta stauroptera_, n. sp. + +Apophyses of the long compressed radial spines simple, conical, about as +long as their distance from the shell. At the base of each spine (in the +outer shell) two elliptical aspinal pores, two to three times as large as +the other pores. + +_Dimensions._--Diameter of the outer shell 0.1, of the inner 0.044. + +_Habitat._--North Pacific, Station 238, surface. + + +2. _Dorypelta gladiata_, n. sp. + +Apophyses of the long cylindrical radial spines simple, triangular, about +half as long as their distance from the shell. At the base of each spine +(in the outer shell) four crossed aspinal pores, the two opposite of which +are much larger than the other two pores. + +_Dimensions._--Diameter of the outer shell 0.09, of the inner 0.04. + +_Habitat._--Central Pacific, Station 266, surface. + + + +Subgenus 2. _Dorypeltidium_, Haeckel. + +_Definition._--Free apophyses of the radial spines branched, with free (not +anastomosing) branches. + + +3. _Dorypelta furcata_, n. sp. + +Apophyses of the long compressed spines simply forked, each with two simple +parallel fork-branches. At the base of each spine two elliptical aspinal +pores, much larger than the other roundish pores. + +_Dimensions._--Diameter of the outer shell 0.08, of the inner 0.04. + +_Habitat._--Central Pacific, Station 274, surface. + + +4. _Dorypelta tetrodon_, n. sp. + +Apophyses of the long compressed spines crossed by a transverse beam, which +bears four simple parallel fork-branches or spikes (perpendicular to the +beam), two larger medial and two smaller lateral. At the base of each spine +four crossed aspinal pores of nearly equal size, little different from the +other pores. + +_Dimensions._--Diameter of the outer shell 0.09, of the inner 0.035. + +_Habitat._--South Pacific, Station 284, surface. + + +5. _Dorypelta ramosa_, n. sp. + +Apophyses of the long cylindrical spines crossed by a transverse beam, +which bears four to six irregularly branched spikes or fork-branches, the +medial of which are larger than the lateral. At {858}the base of each spine +four crossed aspinal pores, two opposite of which are much larger than the +two other pores. + +_Dimensions._--Diameter of the outer shell 0.09, of the inner 0.04. + +_Habitat._--South Pacific, Station 302, surface. + + + +Subgenus 3. _Dorypeltonium_, Haeckel. + +_Definition._--Free apophyses of the radial spines branched, and forming +perforated shields by union of their anastomosing branches. + + +6. _Dorypelta lithoptera_, n. sp. + +Apophyses of the long compressed radial spines with anastomosing branches; +each spine bearing two free separated shields (each with two roundish +aspinal pores). At the base of each spine (in the network of the outer +shell) two elliptical aspinal pores, larger than the other pores. + +_Dimensions._--Diameter of the outer shell 0.09, of the inner 0.03. + +_Habitat._--North Pacific, Station 239, surface. + + +7. _Dorypelta tessaraspis_, n. sp. (Pl. 133, fig. 2). + +Apophyses of the long cylindrical spines with anastomosing branches; each +spine bearing a single free shield with four crossed aspinal pores of equal +size (on the margin of the shield twelve to sixteen spikes). At the base of +each spine (in the outer shell) four crossed aspinal pores, about as large +as the other roundish pores. + +_Dimensions._--Diameter of the outer shell 0.11, of the inner 0.05. + +_Habitat._--Central Pacific, Station 263, surface. + + +8. _Dorypelta dodecaspis_, n. sp. + +Apophyses of the long two-edged spines with anastomosing branches; each +spine bearing a single free shield with six to eight parmal pores (four +crossed aspinal pores alternating with four outer coronal pores), on the +margin of each shield twelve to sixteen spikes. At the base of each spine +(in the outer shell) four crossed aspinal pores, about as large as the +other irregular pores. + +_Dimensions._--Diameter of the outer shell 0.1, of the inner 0.04. + +_Habitat._--North Pacific (off Japan), Station 235, surface. + + + +Genus 370. _Stauropelta_,[410] Haeckel, 1881, Prodromus, p. 468. + +_Definition._--#Phractopeltida# with four simple equatorial spines and +sixteen spines protected by external free apophyses (eight tropical and +eight polar spines). + +{859}The genus _Stauropelta_ is distinguished from the other Phractopeltida +by the possession of sixteen pairs of free apophyses (on the eight tropical +and the eight polar spines); only the other four equatorial spines remain +simple, without apophyses, and form a simple cross in the equatorial plane. + + +1. _Stauropelta cruciata_, n. sp. (Pl. 133, fig. 3). + +Apophyses of the long polar and tropical spines crossed by a transverse +beam, which is again crossed by two perpendicular branches parallel to the +apophyses; branches with free ends, not united by concrescence. At the base +of each spine (in the outer shell) two large elliptical aspinal pores, +larger than the other irregular pores. Four equatorial spines simple, +without apophyses, of the same size as the other sixteen spines. + +_Dimensions._--Diameter of the outer shell 0.12, of the inner 0.05. + +_Habitat._--Indian Ocean (Madagascar), Rabbe, surface. + + +2. _Stauropelta stauropora_, n. sp. + +Apophyses of the long polar and tropical spines crossed by a transverse +beam, which is again crossed by two perpendicular branches parallel to the +apophyses; these branches are united by concrescence, and form a square +shield with four crossed pores, the centre of which is pierced by the +spine. At the base of each spine (in the outer shell) four crossed aspinal +pores, corresponding to those of the shield, of about the same size as the +other roundish pores. Four equatorial spines, simple, without apophyses, +somewhat larger than the other sixteen spines. + +_Dimensions._--Diameter of the outer shell 0.1, of the inner 0.04. + +_Habitat._--Indian Ocean, Sunda-Archipelago, Singapore, Trebing, surface. + + +---- + + +Suborder II. PRUNOPHRACTA. + +_Definition._--Shell ellipsoidal, lenticular or diploconical, with radial +beams of different size. + + + +Family XLII. #BELONASPIDA#, n. fam. (Pl. 136, figs. 6-9; Pl. 139, figs. 8, +9). + +_Definition._--ACANTHARIA with a simple ellipsoidal lattice-shell, composed +of the branched apophyses of twenty radial spines meeting in its centre and +disposed according to the Muellerian law of Icosacantha. Two opposite +equatorial spines larger than the two others. Central capsule ellipsoidal, +enclosed in the fenestrated shell. + +The family #Belonaspida#, formerly united by me with the Dorataspida (in +the Prodromus, 1881, p. 468), differs from it in the ellipsoidal form of +the lattice-shell and {860}the enclosed central capsule. In the spherical +Dorataspida, their ancestral family, all twenty radial spines are of equal +size, whilst here in the Belonaspida two opposite spines are larger than +the eighteen others. These two larger or principal spines are both +equatorial spines, placed in the longitudinal or major axis of the +ellipsoid, or the "hydrotomical axis" (compare above, p. 719). The two +other equatorial spines are constantly smaller, and lie in the transverse +or minor axis of the ellipsoid, or the "geotomical axis." The geometrical +proportion of these two determining axes of the ellipsoidal shell is very +variable (even in one and the same species), commonly 4 : 3 or 3 : 2, +rarely 2 : 1, often only 5 : 4 or 6 : 5. All meridian planes, passing +through the principal spines (or the longitudinal axis of the shell) are +elliptical, and of equal size. All transverse planes, perpendicular to that +axis, are circular; the largest of these circular parallel planes is the +geotomical plane, which passes through the smaller equatorial spines and +the spineless axis. + +In the spherical Dorataspida the internal length of the radial spines (or +the distance between the shell and the centre) is equal in all twenty +spines. In the ellipsoidal Belonaspida this internal length is different, +and commonly exhibits four different degrees; in the two principal spines +it is of first rank, in the eight tropical spines of second rank, in the +four (hydrotomical) polar spines of third rank, and in the six spines (four +geotomical polar spines and two transverse equatorial spines) of fourth +rank. These differences of the internal length become more important the +more the hydrotomical axis is prolonged. Regarding all other qualities (in +form, disposition, and mode of junction at the centre) the ellipsoidal +Belonaspida do not differ from their ancestral group, the spherical +Dorataspida (compare above, p. 802). In both families the pyramidal central +bases of the twenty spines are commonly supported one upon another with +their triangular neighbouring faces; but sometimes also here (particularly +in _Phatnaspis_) the central bases are perfectly grown together. In this +case also the sutures of the meeting branches of the apophyses are +obliterated, whilst usually they remain open. Such forms, with spines and +plates perfectly grown together, form a single piece of acanthin, and were +formerly separated by me as a peculiar genus _Haliommatidium_ (Monogr. d. +Radiol., 1862, p. 419). But as I now find this concrescence to be an +accidental and inconstant peculiarity of some species, it no longer seems +to me to be of generic importance. + +The apophyses of the twenty radial spines, the branches of which compose +the ellipsoidal lattice-shell, exhibit in all Belonaspida the same +appearance as in the Diporaspida (and especially the Ceriaspida) among the +spherical Dorataspida. Everywhere each radial spine gives off only two +opposite primary apophyses, the fork-branches of which unite together and +form a plate or shield with two aspinal pores (as in _Dorataspis_). +Commonly the shell exhibits only these forty parmal pores, the other meshes +between them being sutural pores. Only in one genus, _Phatnaspis_ (Pl. 136, +{861}figs. 6-9), is this number multiplied; the two opposite primary +apophyses are here crossed by numerous perpendicular lateral branches, and +these are again united by secondary perpendicular ramules which are +parallel to the apophyses themselves; therefore each plate here forms a +rhombic shield pierced by very numerous (often more than one hundred) small +quadrangular or circular pores. Only two of these numerous parmal pores are +the primary aspinal pores (sometimes, as in Pl. 136, fig. 8, distinguished +by their larger size); all others are secondary or coronal pores. Therefore +_Phatnaspis_ repeats the characteristic formation of _Coscinaspis_, from +which it differs in its ellipsoidal shell. + +Moreover, the four other genera of the ellipsoidal Belonaspida correspond +perfectly to certain genera of the spherical Dorataspida, and may be +derived from these by hypertrophy or stronger development of two opposite +equatorial spines. In _Thoracaspis_ and _Belonaspis_ (Pl. 139, figs. 8, 9) +the surface of the shell-plates is without crests and dimples (in the +former without, in the latter with accessory by-spines); they thus +correspond to _Dorataspis_ and _Diporaspis_ among the Dorataspida. In two +other genera the surface of the shell-plates bears a network of elevated +crests, separating funnel-shaped dimples, in _Dictyaspis_ without, in +_Coleaspis_ with by-spines; these correspond to _Ceriaspis_ and +_Hystrichaspis_ among the Dorataspida. The small by-spines, covering the +surface, exhibit the same forms as in the Dorataspida; but they are usually +smaller, and less developed in the Belonaspida. + +The twenty radial spines are commonly more or less compressed or two-edged, +sometimes very flat, broad, and triangular (Pl. 139, figs. 8, 9). In some +species (mainly of _Phatnaspis_) they are very long, thin, and +needle-shaped (Monogr. d. Radiol., 1862, Taf. xxii. figs. 10-12). Rarely +they are cylindrical, four-edged, or prismatic. The Belonaspida testify by +this and other peculiarities to their near relation to the Diporaspida and +Phractacanthida and their older origin from _Zygacantha_. + +_The Central Capsule_ is in the Belonaspida ellipsoidal, and more or less +prolonged in the hydrotomical or longitudinal axis of the shell. It is +constantly smaller than the enveloping ellipsoidal shell, and separated +from it by the calymma. Its structure and the shape of its nucleus are the +same as in the nearly allied Dorataspida. + +_Synopsis of the Genera of Belonaspida._ + + ------------------------------------------------------------------------- + I. Subfamily Coleaspida. + Forty parmal pores (two aspinal pores on each plate, no coronal + pores). + ------------------------------------------------------------------------- + Plates not dimpled, without { No by-spines, 371. _Thoracaspis_. + prominent crests. { + { With by-spines, 372. _Belonaspis_. + + Plates dimpled, with a { No by-spines, 373. _Dictyaspis_. + network of prominent { + crests, { With by-spines, 374. _Coleaspis_. + ------------------------------------------------------------------------- + II. Subfamily Phatnaspida. + Eighty to two thousand or more parmal pores (two aspinal pores on + each plate, surrounded by two to one hundred or more coronal pores). + ------------------------------------------------------------------------- + No by-spines (plates not dimpled), 375. _Phatnaspis_. + + + +{862}Genus 371. _Thoracaspis_,[411] Haeckel, 1862, Prodromus, p. 468. + +_Definition._--#Belonaspida# with forty parmal pores (two on each plate), +without dimples and crests, also without by-spines, therefore with smooth +surface. + +The genus _Thoracaspis_ is the simplest form among the Belonaspida, and +repeats in this family the nearly allied genus _Dorataspis_ among the +Dorataspida. It differs from this genus only in the characteristic +prolongation of one equatorial axis, which effects an ellipsoidal +transformation of the spherical central capsule and the enclosing +lattice-shell. + + +1. _Thoracaspis ellipsoides_, n. sp. + +Parmal pores large, elliptical, five or six times as large as the small +circular sutural pores. Each plate surrounded by five or six sutural pores +(a single one on each side). Spines compressed triangular, sword-like, +two-edged; inner and outer half of nearly equal length. + +_Dimensions._--Length of the ellipsoidal shell (or major axis) 0.15, +breadth (or minor axis) 0.12; length of the spines 0.07, basal breadth +0.016. + +_Habitat._--North Pacific, Station 253, surface. + + +2. _Thoracaspis nephropora_, n. sp. + +Parmal pores large, kidney-shaped, three to four times as large as the +roundish small sutural pores. Each plate surrounded by five or six sutural +pores (a single one on each side). Spines in the inner longer part +cylindrical, in the outer shorter part conical, not compressed. + +_Dimensions._--Length of the shell 0.2, breadth 0.15; length of the spines +0.06, basal breadth 0.018. + +_Habitat._--Central Pacific, Station 268, surface. + + +3. _Thoracaspis circopora_, n. sp. + +Parmal pores circular, of the same size as the circular sutural pores. Each +plate surrounded by five or six sutural pores (a single one on each side). +Spines compressed, thin, linear, two-edged; outer part one and a half times +as long as the inner. + +_Dimensions._--Length of the shell 0.17, breadth 0.13; length of the spines +0.12, basal breadth 0.003. + +_Habitat._--South Pacific, Station 288, surface. + + +4. _Thoracaspis bipennis_, n. sp. (Pl. 139, fig. 8). + +Parmal pores elliptical, about twice as large as the circular sutural +pores, which are of rather variable size. Each plate surrounded by eight to +twelve sutural pores (commonly two on each side). {863}Spines compressed, +triangular, gradually tapering towards both ends; outer half a little +longer, and much broader than the inner. + +_Dimensions._--Length of the shell 0.14, breadth 0.12; length of the spines +0.08, basal breadth 0.025. + +_Habitat._--Central Pacific, Station 274, surface. + + + +Genus 372. _Belonaspis_,[412] Haeckel, 1862, Prodromus, p. 468. + +_Definition._--#Belonaspida# with forty parmal pores (two on each plate), +without dimples and crests, but with numerous by-spines on the surface. + +The genus _Belonaspis_ differs from its ancestral genus _Thoracaspis_ only +in the possession of numerous superficial by-spines, and bears therefore to +it the same relation as _Diporaspis_ does to _Dorataspis_. The two latter +differ from the two former in the spherical form of the central capsule and +the enclosing shell, which here becomes ellipsoidal. + + +1. _Belonaspis pandanus_, n. sp. + +Parmal pores elliptical, three or four times as large as the circular +sutural pores. Each plate surrounded by five or six sutural pores (a single +one on each side). Spines compressed, triangular; outer part half as long +as the inner, and twice as long as the numerous, simple, bristle-shaped +by-spines. + +_Dimensions._--Length of the ellipsoidal shell (or major axis) 0.12, +breadth (or minor axis) 0.1; length of the spines 0.03, basal breadth 0.02. + +_Habitat._--South Pacific, Station 295, surface. + + +2. _Belonaspis furcata_, n. sp. + +Parmal pores elliptical, twice as broad as the circular sutural pores. Each +plate surrounded by five or six sutural pores (a single one on each side). +Spines compressed, linear, very thin; outer part longer than the inner. +By-spines very numerous, half as long as the radius, furcate, with +divergent fork-branches. + +_Dimensions._--Length of the shell 0.1, breadth 0.08; length of the spines +0.12, breadth 0.003. + +_Habitat._--Indian Ocean (Cocos Islands), Rabbe, surface. + + +3. _Belonaspis datura_, n. sp. (Pl. 139, fig. 9). + +Parmal pores elliptical, three or four times as large as the circular +sutural pores. Each plate surrounded by ten or twelve sutural pores (two on +each side). Spines triangular, two-edged, about {864}as long as the radius +of the shell; gradually tapering from its surface towards both ends. +By-spines very short and numerous, simple. + +_Dimensions._--Length of the shell 0.13, breadth 0.11; length of the spines +0.08, basal breadth 0.025. + +_Habitat._--Central Pacific, Station 271, surface. + + +4. _Belonaspis lanceolata_, n. sp. + +Parmal pores elliptical, six or eight times as large as the small circular +sutural pores. Each plate surrounded by ten to twelve sutural pores (two on +each side). Spines lanceolate, flat, in the distal part needle-shaped, +about as long as the diameter of the shell. By-spines very numerous, +zigzag, half as long as the shell-radius. + +_Dimensions._--Length of the shell 0.15 breadth 0.13; length of the spines +0.14, basal breadth 0.03; length of the by-spines 0.04. + +_Habitat._--North Pacific, Station 235, surface. + + +5. _Belonaspis conifera_, n. sp. + +Parmal pores kidney-shaped, three or four times as large as the small +circular pores. Each plate surrounded by ten to twelve sutural pores (two +on each side). Spines very thick, half as long in the outer conical part as +in the inner cylindrical part. By-spines very short, conical. + +_Dimensions._--Length of the shell 0.2, breadth 0.16; length of the spines +0.05, basal breadth 0.03. + +_Habitat._--Central Pacific, Station 267, surface. + + +6. _Belonaspis multiforis_, n. sp. + +Parmal pores circular, of the same size as the circular sutural pores. Each +plate surrounded by fifteen to eighteen sutural pores (three on each side). +Spines compressed, about as long as the radius. By-spines very numerous, +zigzag, half as long as the radius. + +_Dimensions._--Length of the shell 0.22, breadth 0.18; length of the spines +0.12, basal breadth 0.012; length of the by-spines 0.06. + +_Habitat._--Equatorial Atlantic, Station 347, surface. + + + +Genus 373. _Dictyaspis_,[413] n. gen. + +_Definition._--#Belonaspida# with forty parmal pores (two on each plate), +without by-spines, but with a network of prominent crests on the dimply +surface. + +The genus _Dictyaspis_ repeats among the Belonaspida the characteristic +structure of _Ceriaspis_ (among the Dorataspida), by the development of +prominent crests forming a {865}network with dimples on the outer surface +of the shields. Either all the dimples or only a part of them are pierced +by a pore. The forty aspinal pores are united in pairs in twenty larger +dimples. The shell is usually very thick-walled and non-transparent. + + +1. _Dictyaspis solidissima_, Haeckel. + + _Dorataspis solidissima_, Haeckel, 1862, Monogr. d. Radiol., p. 416, Taf. + xxii. figs. 6-9. + +Surface of the shell with seventy to eighty funnel-shaped dimples, each of +which is perforated at the base by one or two small meshes; twenty larger +dimples in the centre of the plates (each with two elliptical aspinal +pores), and fifty to sixty smaller sutural dimples between them (each with +a single circular pore). All pores of nearly the same size. No blind +dimples. Outer conical part of the thick radial spines of the same length +as the inner cylindrical part. Radius of the shell four times as large as +the thickness of its wall. + +_Dimensions._--Length of the shell 0.12, breadth 0.1; length of the spines +0.06, basal breadth 0.012. + +_Habitat._--Mediterranean (Messina), surface. + + +2. _Dictyaspis favosa_, n. sp. + +Surface of the shell with one hundred and seventy to one hundred and ninety +deep funnel-shaped dimples, seventy to eighty of which are perforated, the +others blind; among the former each of the fifty to sixty smaller contains +a single sutural pore, each of the twenty larger a couple of aspinal pores. +All pores of nearly the same size. Outer part of the compressed two-edged +spines triangular, half as long as the inner part. Radius of the shell six +times as large as the thickness of its wall. (Differs from _Ceriaspis +favosa_, Pl. 138, fig. 6, mainly in the ellipsoidal form of the shell and +the different size and form of the spines.) + +_Dimensions._--Length of the shell 0.16, breadth 0.13; length of the spines +0.04, basal breadth 0.025. + +_Habitat._--Central Pacific, Station 265, surface. + + +3. _Dictyaspis compacta_, n. sp. + +Surface of the shell with one hundred and seventy to one hundred and ninety +deep funnel-shaped dimples, seventy to eighty of which are perforated, the +others blind; among the former each of fifty to sixty each contain a single +sutural pore, twenty each a couple of aspinal pores. All dimples nearly of +the same size, very deep. Outer part of the compressed sword-like spines +somewhat longer than the inner part. Radius of the dark shell only twice as +large as the thickness of its compact wall. + +_Dimensions._--Length of the shell 0.18, breadth 0.15; length of the spines +0.12, basal breadth 0.02. + +_Habitat._--Central Pacific, Station 274, surface. + + + +{866}Genus 374. _Coleaspis_,[414] Haeckel, 1881, Prodromus, p. 468. + +_Definition._--#Belonaspida# with forty parmal pores (two on each plate), +with numerous by-spines and with a network of prominent crests on the +dimpled surface. + +The genus _Coleaspis_ differs from its ancestral genus _Dictyaspis_ in the +development of numerous by-spines, and bears therefore among the +ellipsoidal Belonaspida the same relation to it as _Hystrichaspis_ does to +_Coscinaspis_ among the spherical Dorataspida. If the four equatorial +spines in _Coleaspis_ become different in pairs, it passes over into +_Hexalaspis_. The shell is usually very dark and thick-walled. + + +1. _Coleaspis coronata_, n. sp. + +All twenty spines of nearly equal size and form, about as long as the +radius of the shell, compressed, sword-like, two-edged; both equatorial +spines of the hydrotomical axis little longer than the eighteen others. +Crests between the dimples of the shell-surface dentated, forming around +the basal half of each spine a cylindrical sheath with a dentated, +crown-like mouth, the teeth of which are prolonged into simple by-spines. +(Similar to _Hexaconus coronatus_, Pl. 139, fig. 5, but differing in the +nearly equal size of the spines and their sheaths, and in the longer +by-spines.) + +_Dimensions._--Major axis of the shell 0.2, minor 0.17; length of the +spines 0.12, basal breadth 0.02. + +_Habitat._--Central Pacific, Station 266, surface. + + +2. _Coleaspis vaginata_, n. sp. (Pl. 140, fig. 13). + +All twenty spines of nearly equal size and form, nearly as long as the +diameter of the shell, conical; both equatorial spines of the hydrotomical +axis about one-third longer than the eighteen others. Crests between the +dimples of the shell-surface serrated, forming around the basal half of +each spine a conical truncate sheath with crested surface and serrated +mouth, the teeth of which are prolonged into short by-spines. (Similar to +_Hexaconus vaginatus_, Pl. 139, fig. 7, but differing in the nearly equal +size of all the spines and in the double thickness of the shell-wall.) + +_Dimensions._--Major axis of the shell 0.12, minor 0.1, length of the +spines 0.08, basal breadth 0.01. + +_Habitat._--North Pacific, Station 253, surface. + + +3. _Coleaspis obscura_, n. sp. + +All twenty spines of nearly equal size and form, little longer than their +large cylindrical sheaths, which are nearly as long as the radius of the +shell, and armed on the truncated mouth with strong triangular by-spines, +both equatorial spines of the hydrotomical axis one and a half times as +long as the eighteen others. Shell very dark and thick walled, quite +opaque. + +{867}_Dimensions._--Major axis of the shell 0.1, minor 0.08; length of the +spines 0.06, of their sheaths 0.04. + +_Habitat._--Arctic Ocean, Greenland, Koch, surface. + + +4. _Coleaspis occulta_, n. sp. + +All twenty spines of nearly equal size and form, quite concealed in their +long cylindrical sheaths, which are somewhat longer than the radius of the +shell, and armed on the truncated mouth with acute simple teeth; each +sheath deeply sulcated, apparently resulting from the concrescence of +numerous parallel leaf-shaped by-spines. Small shell very dark and +thick-walled, quite opaque. + +_Dimensions._--Major axis of the shell 0.08, minor 0.06; length of the +spines and their sheaths 0.05 to 0.06. + +_Habitat._--Antarctic Ocean (off Kerguelen), Station 159, surface. + + + +Subgenus 2. _Coleaspidium_, Haeckel. + +_Definition._--Both equatorial spines of the hydrotomical axis much larger +and of peculiar form, different from the eighteen other spines. + + +5. _Coleaspis amphilonche_, n. sp. + +Both equatorial spines of the hydrotomical axis much longer than the +eighteen others, and of very different form; one and a half times as long +as the diameter of the shell, prismatic, with six prominent edges, +pyramidal at the distal point. The eighteen other spines triangular, +compressed, two-edged, scarcely as long as the radius of the thick-walled +shell. Pores of the shell irregular polygonal, separated by ciliated +crests, which bear simple by-spines (one-third as long as the radius). + +_Dimensions._--Major axis of the shell 0.15, minor 0.12; length of the two +larger spines 0.22, of the eighteen smaller 0.06 to 0.08; basal breadth of +the former 0.03, of the latter 0.008. + +_Habitat._--South Atlantic, Station 341, surface. + + +6. _Coleaspis hydrotomica_, n. sp. (Pl. 140, fig. 14). + +Both equatorial spines of the hydrotomical axis much larger than the +eighteen others, and of very different form; about as long as the diameter +of the shell, in the basal half four-sided pyramidal, with four thick +prominent edges, in the middle part constricted, in the distal half +lanceolate, two-edged. Both equatorial spines of the geotomical axis of +similar form, but much smaller, scarcely one-third as long. The sixteen +other spines sword-like, thin, two-edged, about as long as the radius of +the thick-walled shell. Pores of the shell irregular roundish, separated by +high dentated crests, which bears zigzag by-spines (half as long as the +radius). + +_Dimensions._--Major axis of the shell 0.12, minor axis 0.1; length of the +two larger spines 0.11, of the eighteen others 0.04 to 0.06; basal breadth +of the former 0.04, of the latter 0.01. + +_Habitat._--Cape of Good Hope, Station 143, surface. + + + +{868}Genus 375. _Phatnaspis_,[415] Haeckel, 1881, Prodromus, p. 468 + +_Definition._--#Belonaspida# with eighty to two thousand or more parmal +pores (four to one hundred or more on each plate), without by-spines on the +surface. + +The genus _Phatnaspis_ corresponds to the spherical _Coscinaspis_ among the +Dorataspida, and differs from the other Belonaspida in the great number of +the parmal pores; whilst the four other preceding genera exhibit only two +opposite aspinal pores in the centre of each plate, in this there are +constantly numerous coronal pores in addition to these, and the plates +always possess the characteristic form of a wainscotted or panelled work, +with quadrangular meshes. The number of these parmal pores amounts in each +plate to from ten to twenty, often one hundred and twenty or more; +therefore the number of parmal pores in the whole shell amounts to two +thousand or more. Sometimes the pores are circular, but in this case too +they are surrounded by quadrangular frames. The quadrangles are sometimes +quite regular squares, sometimes more or less irregular. The thin and +fragile bars between the quadrangular pores form in each plate two peculiar +systems of parallel crests, which cross at right angles. Commonly the +parallel crests of one system (parallel to the major diameter of the +compressed radial spines) are equidistant, and pierce from one edge of the +plate to the opposite, whilst the parallel crests of the other system +(parallel to the minor diameter of the spines) are interrupted and at +different distances (Pl. 136, fig. 9); but in other species both crossed +systems are quite regular. In each plate there is one primary diagonal rib +(often stronger than the parallel crests) which connects the two opposite +corners of the rhomboidal plate. We can distinguish in this genus three +different subgenera: A. in _Phatnasparium_ the primary diagonal rib arises +from both flat sides of the compressed sword-like, radial spines; B. in +_Phatnasplenium_ from both sharp edges of them; C. in _Phatnaspidium_ two +crossed diagonal ribs arise from four edges of the spines (combination of A +and B). Therefore in the first subgenus (A) two primary aspinal pores are +placed opposite on the sharp edges of the spines, but in the second (B) +inversely on their flat sides; in the third (C) there are apparently four +primary aspinal pores, which are probably derived from B or A by division +of the two pores. + + + +Subgenus 1. _Phatnasparium_, Haeckel. + +_Definition._--In the centre of each rhomboidal plate two primary aspinal +pores, opposite on both edges of the compressed spines, from both flat +sides of which the primary diagonal crest arises. + + +{869}1. _Phatnaspis lacunaria_, n. sp. (Pl. 136, fig. 9). + +Parmal pores irregular quadrangular, of unequal size and form, ten to +twelve on each side of the primary diagonal rib, which arises from both +flat sides of the two-edged spines; two primary aspinal pores opposite on +both edges of the latter. Spines much compressed, sword-like, their outer +half shorter than the inner. + +_Dimensions._--Length of the shell 0.21 to 0.23, breadth 0.18 to 0.2; basal +breadth of the spines 0.01. + +_Habitat._--Central Pacific, Station 268, surface. + + +2. _Phatnaspis ensiformis_, n. sp. + +Parmal pores irregular quadrangular, of unequal size and form, six to eight +on each side of the primary diagonal rib, which arises from both flat sides +of the two-edged spines; two primary aspinal pores opposite on the two +edges of the latter. Spines very broad, strongly compressed, sword-like, +their outer half larger than the inner. + +_Dimensions._--Length of the shell 0.16, breadth 0.11; basal breadth of the +spines 0.02. + +_Habitat._--Tropical Atlantic, Station 348, surface. + + +3. _Phatnaspis loculata_, n. sp. + +Parmal pores regular quadrangular, of nearly equal size and form, twelve to +sixteen on each side of the primary diagonal rib, which arises from both +flat sides of the two-edged spines; two primary aspinal pores on the two +edges of the latter. Spines linear, compressed, very long and thin, their +outer half three to four times as long as the inner. + +_Dimensions._--Length of the shell 0.24, breadth 0.18; breadth of the +spines 0.004. + +_Habitat._--North Atlantic, Station 354, surface. + + +4. _Phatnaspis fenestrata_, Haeckel. + + _Haliommatidium fenestratum_, Haeckel, 1862, Monogr. d. Radiol., p. 421. + +Parmal pores regular quadrangular, of nearly equal size and form, six to +eight on each side of the primary diagonal rib, which arises from both flat +sides of the two-edged spines; two primary aspinal pores on the two edges +of the latter. Spines linear, little compressed, or nearly needle-shaped, +very long and thin, their outer half five to ten times as long as the +inner. + +_Dimensions._--Length of the shell 0.11 to 0.12, breadth 0.07 to 0.08; +breadth of the spines 0.002. + +_Habitat._--Mediterranean (Messina), surface. + + +5. _Phatnaspis cristata_, n. sp. (Pl. 136, fig. 6). + +Parmal pores circular, of very different size, separated by high square +crests, ten to twelve on each side of the high, comb-like, primary diagonal +rib, which arises from both flat sides of the {870}twoedged spines; two +primary aspinal pores on the two edges of the latter. Each circular pore is +surrounded by a square frame. Spines sword-like, strongly compressed, their +outer part longer than the inner. + +_Dimensions._--Length of the shell 0.2 to 0.22, breadth 0.16 to 0.18; basal +breadth of the spines 0.01. + +_Habitat._--North Pacific, Station 254, surface. + + +6. _Phatnaspis coscinoides_, n. sp. + +Parmal pores circular, regular, all of nearly equal size, twelve to sixteen +on each side of the primary diagonal rib, which arises from both flat sides +of the two-edged spines; two primary pores on the two edges of the latter. +Spines linear, little compressed, their outer part much longer than the +inner. + +_Dimensions._--Length of the shell 0.18, breadth 0.15; breadth of the +spines 0.006. + +_Habitat._--South Atlantic, Station 325, surface. + + + +Subgenus 2. _Phatnasplenium_, Haeckel. + +_Definition._--In the centre of each rhomboidal plate two primary aspinal +pores, opposite on the two flat sides of the compressed spines, from the +two edges of which the primary diagonal crest arises. + + +7. _Phatnaspis orthopora_, n. sp. + +Parmal pores irregular quadrangular, of unequal size and form, four to six +on each side of the primary diagonal rib, which arises from both edges of +the compressed spines; two larger primary aspinal pores opposite on the two +flat sides of the latter. Spines very thin and long, linear, their outer +half three to four times as long as the inner. + +_Dimensions._--Length of the shell 0.08, breadth 0.06; breadth of the +spines 0.003. + +_Habitat._--North Atlantic, Station 353, surface. + + +8. _Phatnaspis polypora_, n. sp. + +Parmal pores irregular polygonal, of very unequal size and form, sixteen to +twenty on each side of the primary diagonal rib, which arises from both +edges of the compressed spines; two very large, lanceolate, primary aspinal +pores opposite on the two flat sides of the latter. Spines very thin, +linear, on the outside of the shell rudimentary. (This remarkable species +somewhat resembles _Coscinaspis polypora_, Pl. 136, fig. 8.) + +_Dimensions._--Length of the shell 0.32, breadth 0.24; breadth of the +spines 0.002. + +_Habitat._--South Atlantic, Station 332, surface. + + +{871}9. _Phatnaspis quadratura_, n. sp. + +Parmal pores regular, square, all of nearly equal size and form, ten to +twelve on each side of the primary diagonal rib, which arises from both +edges of the compressed spines; two primary aspinal pores opposite on the +two flat sides of the latter, not different from the other pores. Spines +sword-like, their outer part about as long as the inner. + +_Dimensions._--Length of the shell 0.2, breadth 0.16; basal breadth of the +spines 0.004. + +_Habitat._--Central Pacific, Station 274, surface. + + +10. _Phatnaspis tabulata_, Haeckel. + + _Haliomma tabulatum_, J. Mueller, 1858, Abhandl. d. k. Akad. d. Wiss. + Berlin, p. 37, Taf. v. figs. 5-8. + + _Haliomma tabulatum_, Haeckel, 1862, Monogr. d. Radiol., p. 429. + +Parmal pores regular, circular, with square frames, all of nearly equal +size, eight to ten on each side of the primary diagonal rib, which arises +from both edges of the compressed spines; two primary aspinal pores +opposite on the flat sides of the latter. Spines sword-like, short, +scarcely half as long as the radius of the shell, their central ends are +thickened and cause by their union the deceptive appearance of an enclosed +"medullary shell." + +_Dimensions._--Length of the shell 0.12 to 0.15, breadth 0.1 to 0.12; +breadth of the spines 0.006. + +_Habitat._--Mediterranean; Nice, Mueller; Portofino, near Genoa, Haeckel, +surface. + + + +Subgenus 3. _Phatnaspidium_, Haeckel. + +_Definition._--In the centre of each rhomboidal plate four primary aspinal +spines, forming a regular cross, the centre of which receives the +cylindrical or four-sided prismatic spine. + + +11. _Phatnaspis haliommidium_, n. sp. (Pl. 136, fig. 7). + +Parmal pores irregular quadrangular, of unequal size and form, eight to ten +on each side of the crossed diagonal ribs, which arise at right angles from +the four edges of the prismatic spines; four primary aspinal pores not +different from the others. Outer part of the strong spines scarcely longer +than the inner. (Resembling _Icosaspis tabulata_, Pl. 136, fig. 2, which, +however, is distinguished by the spherical shell and the larger pores.) + +_Dimensions._--Length of the shell 0.22, breadth 0.17; breadth of the +spines 0.016. + +_Habitat._--North Pacific, Station 244, surface. + + +12. _Phatnaspis muelleri_, n. sp. + + _Haliommatidium muelleri_, Haeckel, 1862, Monogr. A. Radiol, p. 419, pl. + xiii. figs. 10-12. + +Parmal pores regular, square, all of nearly equal size and form, twelve to +sixteen on each side of the crossed diagonal ribs, which arise at right +angles from the needle-shaped spines; the four {872}primary aspinal pores +not different from the others. Spines very thin and long, cylindrical; four +to six times longer in the outer than in the inner part. + +_Dimensions._--Length of the shell 0.24, breadth 0.16; breadth of the +spines 0.002. + +_Habitat._--Mediterranean (Messina), surface. + + + +Family XLIII. #HEXALASPIDA#, n. fam. (Pl. 139). + +_Definition._--ACANTHARIA with a simple discoidal or lenticular +lattice-shell, composed of the branched apophyses of twenty radial spines +meeting in the centre and disposed according to the Muellerian law of +Icosacantha. Six larger spines in the hydrotomical plane, prominent on the +margin of the circular or elliptical biconvex lens. Fourteen other spines +much smaller or rudimentary. Central capsule biconvex lenticular, enclosed +in the fenestrated shell. + +The family #Hexalaspida# represents a new small, but very interesting group +of Acanthophracta, which differs from all others in the lentelliptical or +triaxial form of the lenticular lattice-shell, the margin of which bears +six larger spines placed in the hydrotomical plane (compare above, p. 719). +They may therefore be characterised shortly as "_Acanthophracta +lentelliptica_," with three different dimensive axes and six larger +marginal spines. A closer comparison with the other ACANTHARIA leaves no +doubt that the Hexalaspida must be derived from the Belonaspida by stronger +development of six radial spines placed in the hydrotomical plane, namely, +two equatorial and four associated polar spines; whilst the six spines of +the geotomical plane (perpendicular to the former) are much smaller; the +eight tropical spines are intermediate in size between the former and the +latter. + +The geometrical fundamental form of the Hexalaspida (of the central capsule +as well as of the enclosing shell) is therefore lentelliptical, with three +different dimensive axes, and they exhibit among the ACANTHARIA a relation +to the spherical Dorataspida and the ellipsoidal Belonaspida similar to +that which the lentelliptical #Larcoidea# exhibit to the spherical +#Sphaeroidea# and the ellipsoidal #Prunoidea# among the #Sphaerellaria# +(compare above, p. 599). The largest of the three dimensive axes (which are +perpendicular to one another) is here the hydrotomical axis, the shortest, +on the contrary, the geotomical axis; the intermediate in size being the +spineless axis. The development of the whole body is strongest in the +hydrotomical meridian plane, in which the six principal spines are placed; +it is weakest in the geotomical plane, in which the six smallest spines are +placed; the eight tropical spines are intermediate in size between the +others. This peculiar development is illustrated by the figures of Pl. 139, +where the four equatorial spines are everywhere marked by _c_, the eight +tropical spines by _b_ and _d_, the eight polar spines by _a_ and _e_. + +{873}Rarely the six hydrotomical or principal spines are of equal size, and +thus the margin of the shell may be quite circular or regularly hexagonal +(Pl. 139, figs. 1-3); the two equatorial spines of the hydrotomical plane +are usually larger than its four polar spines, and thus the margin of the +shell becomes more or less elliptical (Pl. 139, figs. 4-7). Usually (almost +constantly) these six larger spines are more or less compressed, +triangular, often very broad and flat; their two edges lie in the +hydrotomical plane. Their two flat surfaces are often furrowed, with +longitudinal ribs or crests converging towards the simple apex of the +spines. + +The fourteen smaller spines are regularly disposed according to the +Muellerian law of Icosacantha on both convex sides of the lenticular shell; +they are not only smaller than the six principal spines, but often also of +different form, much thinner and shorter, sometimes needle-shaped. In the +genera _Hexonaspis_ and _Hexacolpus_ (Pl. 139, figs. 1, 2) only their inner +part (inside of the shell) is developed, whilst their outer part is quite +rudimentary and not prominent on the surface. Therefore these genera appear +to possess only six marginal spines externally. + +_The Lenticular Shell_ itself offers in the Hexalaspida great difficulties +in the way of accurate study, as its wall is constantly very thick and +dark, often quite opaque and non-transparent. However, prolonged accurate +researches have convinced me that its structure is essentially the same as +in the Belonaspida and especially in the genera _Dictyaspis_ and +_Coleaspis_. As in these latter the twenty plates of the shell bear high +crests or combs on the outer surface, and by these funnel-shaped dimples +are separated. The network of these crests is more or less regular (Pl. +139, figs. 1-7). Around the base of each radial spine the shell is usually +elevated in the form of a conical or cylindrical sheath; the crests are +prolonged into the sheaths as longitudinal ribs, parallel to the spine or +convergent towards its apex. Whilst in _Hexalaspis_ and _Hexonaspis_ these +basal sheaths are not at all or but little prominent (Pl. 139, fig. 2; Pl. +140, fig. 16), in _Hexaconus_ and _Hexacolpus_ they envelop the basal half +(or even more) of the spines, and very often the circular or elliptical +free distal edge of the sheath is elegantly denticulated or serrated (Pl. +139, figs. 1, 3-7; pl. 140, figs. 9-16). + +_The Pores_ of the shell exhibit in the Hexalaspida the same shape as in +the majority of the Belonaspida. Each spine bears only two broad opposite +apophyses, the fork-branches of which unite to form a polygonal shield with +two pores. The number of parmal pores is constantly (?) forty, as each +plate possesses only two primary aspinal pores; there are no secondary or +coronal pores. The numerous (between fifty and one hundred, rarely more) +smaller pores between the forty parmal pores are probably always sutural +pores; however, their number and position is very difficult to determine, +on account of the high protecting crests; the majority of the funnel-shaped +dimples between the latter seem to be blind, not perforated. Sometimes all +the dimples, except the twenty spinal ones, seem to be blind and the +sutural pores appear {874}to have disappeared completely, so that there +remain only twenty aspinal pores (Pl. 139, fig. 4). + +The internal cavity of the shell in all Hexalaspida is very small, on +account of the thickness of the massive wall; the latter is often greater +than the diameter of the cavity. Setting aside this disproportion, the +space of the cavity is further much reduced by the internal parts of the +thick radial spines, which are united in the centre by their pyramidal +bases (Pl. 140, fig. 15). Usually the twenty bases seem to remain free +(supported one upon another by means of their triangular faces); but +sometimes they seem to grow together perfectly and to form a single central +star of acanthin. In some species, too, the sutures of the meeting branches +of the apophyses of neighbouring spines seem to grow together, so that the +whole shell exhibits a single piece of acanthin. + +_The Central Capsule_ of the Hexalaspida is therefore very small and seems +to fill up the greatest part of the shell-cavity. Its form is constantly +more or less lenticular, sometimes lentelliptical. On account of the +opacity of the shell I could not make out its shape more closely. + +_Synopsis of the Genera of Hexalaspida._ + + All twenty spines externally } Sheaths of the spines + developed, prominent on } not prominent, 376. _Hexalaspis_. + the surface of the } + lenticular shell. } Sheaths of the spines + } prominent, 377. _Hexaconus_. + + Only six spines (the } + hydrotomical spines) } Sheaths of the spines + externally developed and } not prominent, 378. _Hexonaspis_. + prominent on the margin } + of the disk; the other } Sheaths of the spines + fourteen spines not } prominent, 379. _Hexacolpus_. + prominent. } + + + +Genus 376. _Hexalaspis_,[416] n. gen. + +_Definition._--#Hexalaspida# with twenty prominent radial spines, which are +not surrounded by prominent sheaths; the six hydrotomical spines much +larger than the fourteen others. + +The genus _Hexalaspis_ is the simplest form among the Hexalaspida, and may +be derived directly from _Dictyaspis_ among the Belonaspida, by stronger +development of the six hydrotomical spines. As in the following genus +_Hexaconus_ all twenty spines are prominent externally. + + + +Subgenus 1. _Hexalasparium_, Haeckel. + +_Definition._--Six hydrotomical spines of equal size. + + +{875}1. _Hexalaspis heliodiscus_, n. sp. (Pl. 139, fig. 2). + +All six hydrotomical spines of nearly equal size (or sometimes the two +equatorial a little larger than the four polar spines), isosceles +triangular, compressed, smooth; about as long as the radius of the shell, +and half as broad at the base. The fourteen other spines very small, also +triangular and compressed, but little prominent on the two convex sides of +the lenticular shell. + +_Dimensions._--Diameter of the shell 0.11; length of the six hydrotomical +spines 0.05, basal breadth 0.03. + +_Habitat._--Central Pacific, Station 271 to 274, surface. + + +2. _Hexalaspis stellata_, n. sp. + +All six hydrotomical spines of nearly equal size, lanceolate compressed, +with two longitudinal furrows on each flat side, about as long as the +diameter of the shell, and one-fourth as broad at the base. The fourteen +other spines very thin, also compressed, half as long and only one-fourth +as broad as the six large spines. + +_Dimensions._--Diameter of the shell 0.14; length of the six hydrotomical +spines 0.13, basal breadth 0.035. + +_Habitat._--South Pacific, Station 284, surface. + + + +Subgenus 2. _Hexalaspidium_, Haeckel. + +_Definition._--Six hydrotomical spines of unequal size, two opposite +(equatorial) much larger than the four other (polar) spines. + + +3. _Hexalaspis sexalata_, n. sp. + +Six hydrotomical spines of unequal size; the two equatorial spines about as +long as the shell-radius and twice as long as the four polar spines, which +are isosceles triangular. The fourteen other spines are only half as long +and one-fourth as broad as the latter, little prominent. (Resembles +_Hexonaspis hastata_, Pl. 140, fig. 16, which is distinguishable by the +furrows on the six spines and by the total absence of the fourteen external +rudimentary spines.) + +_Dimensions._--Diameter of the shell 0.15; length of the two equatorial +spines 0.08, of the four polar spines 0.04, of the fourteen other spines +0.02. + +_Habitat._--North Pacific, Station 240, surface. + + +4. _Hexalaspis hexalastrum_, n. sp. + +Six hydrotomical spines of unequal size; the two equatorial spines somewhat +longer than the diameter of the shell and three times as long as the four +polar spines, all six triangular, smooth, of the same basal breadth (equal +to half the radius). The fourteen other spines very thin, conical at the +base, nearly as long as the radius. + +{876}_Dimensions._--Diameter of the shell 0.21; length of the two +equatorial spines 0.24, of the eighteen others 0.08 to 0.1; basal breadth +of the six larger spines 0.05, of the fourteen others 0.01. + +_Habitat._--Western Tropical Pacific, Station 224, surface. + + +5. _Hexalaspis hexaglypha_, n. sp. + +Six hydrotomical spines of unequal size; the two equatorial very large, +six-sided prismatic, twice as long as the diameter of the shell and four +times as long as the four pyramidal polar spines; each of these six spines +with six deep furrows between the six prominent edges. The fourteen other +spines very thin, compressed, two-edged, about as long as the radius of the +shell. + +_Dimensions._--Diameter of the shell 0.11; length of the two equatorial +spines 0.2, of the eighteen others 0.04 to 0.06; basal breadth of the six +larger spines 0.03, of the fourteen others 0.01. + +_Habitat._--Tropical Atlantic, Station 352, surface. + + + +Genus 377. _Hexaconus_,[417] n. gen. + +_Definition._--#Hexalaspida# with twenty prominent radial spines, which are +surrounded at the base by prominent sheaths; the six hydrotomical spines +much larger than the fourteen others. + +The genus _Hexaconus_ differs from the preceding _Hexalaspis_ in the +development of conical or cylindrical sheaths surrounding the basal parts +of the radial spines; these sheaths are developed sometimes around all +twenty spines, sometimes only around the six larger hydrotomical spines. + + + +Subgenus 1. _Hexaconarium_, Haeckel. + +_Definition._--Six hydrotomical spines of equal size. + + +1. _Hexaconus ciliatus_, n. sp. (Pl. 139, fig. 3). + +All six hydrotomical spines of nearly equal size, pyramidal, with six +prominent edges, somewhat longer than the radius of the shell. Sheaths +sulcated, finely ciliated at the mouth, twice as broad as long and only +one-fourth as long as the spines. The fourteen smaller spines very thin, +bristle-shaped, shorter than the radius of the shell. + +_Dimensions._--Diameter of the shell 0.16; length of the six hydrotomical +spines 0.11; basal breadth 0.03. + +_Habitat._--Central Pacific, Station 270, surface. + + +{877}2. _Hexaconus coronatus_, n. sp. (Pl. 139, fig. 5). + +All six hydrotomical spines of equal size, conical, somewhat compressed, +with two prominent edges, scarcely as long as the radius of the shell. +Sheaths crested, strongly dentated on the mouth, three times as broad as +long and only one-sixth as long as the spines. Fourteen smaller spines +about half as large as the six principal spines, of the same form, but +without coronated sheaths. + +_Dimensions._--Diameter of the shell 0.2; length of the six hydrotomical +spines 0.1; basal breadth 0.02. + +_Habitat._--North Pacific, Station 253, surface. + + +3. _Hexaconus velatus_, n. sp. (Pl. 139, fig. 6). + +All six hydrotomical spines of equal size, conical, somewhat compressed, +shorter than the radius of the shell. Sheaths very large, truncated +conical, enveloping the spines almost entirely, with crested wall, only +half as broad at the constricted mouth as at the base. The fourteen smaller +spines about half as large as the six principal spines, of the same form, +but without large sheaths. + +_Dimensions._--Diameter of the shell 0.12; length of the six hydrotomical +spines 0.05; basal breadth 0.01. + +_Habitat._--North Atlantic, Station 354, surface. + + + +Subgenus 2. _Hexaconidium_, Haeckel. + +_Definition._--Six hydrotomical spines of unequal size, two opposite +(equatorial) much larger than the four other (polar) spines. + + +4. _Hexaconus serratus_, n. sp. (Pl. 139, fig. 4). + +Six hydrotomical spines of unequal size, the two equatorial being as long +as the radius of the shell and one and a half times as large as the four +polar; all of the same form, triangular, compressed, with six prominent +edges. Sheaths cylindrical, half as long as the spines, with prominent +crests, and with strong serrated teeth at the distal mouth. The fourteen +smaller spines scarcely one-fourth or one-sixth as large as the six +principal spines, without prominent sheaths. + +_Dimensions._--Diameter of the shell 0.2; length of the equatorial spines +0.1, basal breadth 0.05; length and breadth of the sheaths 0.05. + +_Habitat._--South Pacific, Station 288, surface. + + +5. _Hexaconus vaginatus_, n. sp. (Pl. 139, fig. 7). + +Six hydrotomical spines of unequal size; the two equatorial very stout, +pyramidal, six-edged, nearly as long as the diameter of the shell, and on +the base three to four times as broad as the eighteen other spines, which +are much thinner, all nearly of equal length, and two-edged. All +{878}twenty spines are provided with prominent basal sheaths, which are +truncate conical, sulcate, and dentate on the narrowed distal mouth. The +sheaths of the six hydrotomical spines are twice to three times as large as +those of the fourteen smaller spines. + +_Dimensions._--Diameter of the shell 0.15; length of the spines 0.12; basal +breadth of the equatorial spines 0.04, of the other spines 0.02; length of +the hydrotomical sheaths 0.05, of the other sheaths 0.02. + +_Habitat._--Central Pacific, Station 274, surface. + + +6. _Hexaconus echinatus_, n. sp. (Pl. 140, fig. 12). + +Six hydrotomical spines of unequal size; the two equatorial, and their +sheaths twice as large as the four polar spines. These six spines are +six-edged, pyramidal, and their basal half enveloped by very large conical +sheaths which are sulcate, and twice as broad on the dentate distal mouth +as on the narrower base. The other fourteen spines are very thin, +two-edged, half as long, with low sheaths. Approaches some forms of +_Diploconus_. + +_Dimensions._--Diameter of the shell 0.15; length of the equatorial spines +0.13, of the polar spines 0.08. + +_Habitat._--Indian Ocean, Belligemma, Ceylon, Haeckel, surface. + + + +Genus 378. _Hexonaspis_,[418] n. gen. + +_Definition._--#Hexalaspida# with six prominent radial spines (in the +hydrotomical plane) which are not surrounded by prominent sheaths; the +fourteen other spines quite rudimentary, not prominent. + +The genus _Hexonaspis_ and the following _Hexacolpus_ differ from the two +preceding genera in the rudimentary shape of the fourteen reduced and +stunted smaller spines; these are only developed inside the shell, and are +not prominent outside over its surface. + + + +Subgenus 1. _Hexonasparium_, Haeckel. + +_Definition._--Six hydrotomical spines of equal size. + + +1. _Hexonaspis heliosestrum_, n. sp. + +All six hydrotomical spines of nearly equal size, isosceles triangular, +compressed, smooth, about as long as the diameter of the shell and three +times as long as broad at the base. This species is very similar to +_Hexalaspis heliodiscus_ (Pl. 139, fig. 2), but differs in the larger size +of the six marginal spines and in the complete external absence of the +fourteen smaller spines. + +{879}_Dimensions._--Diameter of the shell 0.13; length of the six marginal +spines 0.12, basal breadth 0.04. + +_Habitat._--Tropical Atlantic, Station 348, surface. + + +2. _Hexonaspis hexapleura_, n. sp. (Pl. 140, fig. 15). + +All six hydrotomical spines of nearly equal size, triangular, compressed, +six-edged, about as long as the radius of the shell and twice as long as +broad on the base. Two strong prominent ribs on each flat side of the +spines. Shell very thick-walled, with a very small cavity. + +_Dimensions._--Diameter of the shell 0.11; length of the six marginal +spines 0.06, basal breadth 0.03. + +_Habitat._--South Atlantic, Station 332, surface. + + +3. _Hexonaspis hexagona_, n. sp. + +All six hydrotomical spines of equal size, very short, triangular, only +half as long as broad at the base. The whole shell accordingly forms a +regular hexagon, the six corners of which are formed by the distal points +of the rudimentary spines, the six sides by their straight lateral edges. +Shell very dark. + +_Dimensions._--Diameter of the shell 0.2; length of the six marginal spines +0.03, basal breadth 0.06. + +_Habitat._--South Atlantic (east of Patagonia), Station 318, surface. + + + +Subgenus 2. _Hexonaspidium_, Haeckel. + +_Definition._--Six hydrotomical spines of unequal size, two opposite +(equatorial) much larger than the four other (polar) spines. + + +4. _Hexonaspis hastata_, n. sp. (Pl. 140, fig. 16). + +Six hydrotomical spines of unequal size; two larger equatorial spines with +six prominent wings, about as long as the radius of the shell and half as +broad at the base; the four polar spines quite as broad, but only half as +long, nearly equilateral triangular, with two shallow furrows on each flat +side at the broader base. The fourteen smaller spines not visible on the +surface, quite rudimentary. Crests of the surface elegantly denticulated. + +_Dimensions._--Diameter of the shell 0.14; length of the two equatorial +spines 0.08, of the four polar spines 0.04; basal breadth 0.04. + +_Habitat._--Central Pacific, Station 271, surface. + + + +{880}Genus 379. _Hexacolpus_,[419] n. gen. + +_Definition._--#Hexalaspida# with six prominent radial spines (in the +hydrotomical plane), which are surrounded by prominent sheaths at the base; +the fourteen other spines quite rudimentary, not prominent. + +The genus _Hexacolpus_ differs from the preceding _Hexonaspis_ in the +development of conical or cylindrical sheaths around the basal parts of the +radial spines. It bears to the latter the same relation as _Hexaconus_ +exhibits to _Hexalaspis_. + + + +Subgenus 1. _Hexacolparium_, Haeckel. + +_Definition._--Six hydrotomical spines all nearly of equal size. + + +1. _Hexacolpus nivalis_, n. sp. (Pl. 139, fig. 1). + + _Hexalaspis nivalis_, Haeckel, 1882, Manuscript et Atlas. + +All six hydrotomical spines of nearly equal size and equidistant, thin, +lanceolate, compressed, somewhat shorter than the diameter of the hexagonal +shell. Sheaths nearly prismatic, conical in the distal third, each with +twelve prominent parallel crests, which are separated by twelve deep +furrows; their contracted distal opening or mouth denticulate. The sheaths +are as long as the radius of the shell, and envelop two-thirds of the +spines. (Resembles certain forms of snow-crystals.) + +_Dimensions._--Diameter of the shell 0.15, thickness of its wall 0.08; +length of the spines 0.1, of the sheath 0.007; breadth of the latter 0.04. + +_Habitat._--West Tropical Pacific, Station 225, surface. + + +2. _Hexacolpus conifer_, n. sp. + +All six hydrotomical spines of equal size and equidistant, triangular, +compressed, about as long as the radius of the circular shell. Sheaths +conical, sulcate, half as broad on the serrate distal end as on the base. +The sheaths envelop the basal half of the spines. + +_Dimensions._--Diameter of the shell 0.18; length of the spines 0.1, of the +sheaths 0.06; basal breadth of the latter 0.07, distal breadth 0.04. + +_Habitat._--North Pacific, Station 236, surface. + + + +Subgenus 2. _Hexacolpidium_, Haeckel. + +_Definition._--Six hydrotomical spines of unequal size, two opposite +(equatorial) much larger than the four other (polar) spines. + + +{881}3. _Hexacolpus trypanon_, n. sp. (Pl. 140, fig. 11). + +Six hydrotomical spines of unequal size, two equatorial about as long as +the diameter of the shell and nearly twice as large as the four polar; all +of the same form, quadrangular prismatic, with prominent edges and pointed +distal ends. Sheaths six-sided prismatic, with strong prominent edges and +thinner parallel ribs between them; their distal mouth with six strong +denticulated teeth. The sheaths envelop two-thirds of the spines, and are +as broad as the radius of the shell. + +_Dimensions._--Diameter of the shell 0.13; length of the equatorial spines +0.12, of their sheaths 0.08; breadth of the latter 0.06. + +_Habitat._--South Pacific, Station 288, surface. + + +4. _Hexacolpus dodecodus_, n. sp. + +Six hydrotomical spines of unequal size, two equatorial about as long as +the radius of the shell and twice as large as the four polar; all of the +same form, triangular, compressed, sulcated. Sheaths prismatic, with twelve +prominent, parallel edges, and twelve strong serrated triangular teeth on +the mouth. The sheaths envelop the basal half of the spines. This species +greatly resembles _Hexaconus serratus_ (Pl. 139, fig. 4), but differs in +the larger size of the equatorial spines and the complete reduction of the +fourteen smaller spines. + +_Dimensions._--Diameter of the shell 0.2; length of the equatorial spines +0.1, of their sheaths 0.06; breadth of the latter 0.08. + +_Habitat._--North Pacific, Station 248, surface. + + +5. _Hexacolpus infundibulum_, n. sp. (Pl. 140, fig. 10). + +Six hydrotomical spines of unequal size, two equatorial about twice as long +as the diameter of the shell and as the four polar spines; all six spines +of the same form, quadrangular prismatic, pointed at the distal pyramidal +end. Sheaths conical, two to three times as broad at the denticulate distal +mouth as at the narrow base, sulcate; the mantle of the cone concavely +vaulted. The large sheaths envelop two-thirds or three-fourths of the +spines. + +_Dimensions._--Diameter of the shell 0.1 to 0.13; length of the equatorial +spines 0.15 to 0.2, of their sheaths 0.1 to 0.15; basal breadth of the +latter 0.04, distal breadth 0.12. + +_Habitat._--Central Pacific, Station 272, surface. + + + +Family XLIV. #DIPLOCONIDA#, Haeckel (Pl. 140). + +_Diploconida_, Haeckel, 1862, Monogr. d. Radiol., p.404. + +_Definition._--ACANTHARIA with simple diploconical shell, composed of two +very large equatorial spines which are opposite in the hydrotomical axis, +are surrounded by conical or cylindrical, often compressed sheaths, and +arise from a small central {882}lattice-shell. Eighteen other spines +(disposed according to the Muellerian law of Icosacantha) much smaller, +often rudimentary. Central capsule ellipsoidal or diploconical. + +The family #Diploconida#, founded by me in 1862 for a single Mediterranean +species (_Diploconus fasces_), appears to be the most aberrant and strange +form among the ACANTHARIA. As I had met with only a single specimen, very +dark and intransparent in its central part, my observations on its +structure were imperfect and the explanation of it partly erroneous +(compare my Monograph, pp. 46, 404, Taf. xx. figs. 7, 8). However, I +regarded _Diploconus_ as the representative of quite a peculiar family, +derived from the Acanthometrida, and I correctly compared the large +opposite radial spines of one equatorial axis with the corresponding parts +in _Amphilonche_. + +Afterwards Richard Hertwig observed some specimens of _Diploconus fasces_ +in the same locality (Messina), and gave an accurate description of its +central capsule, including numerous small nuclei (1879, Organismus d. +Radiol., p. 28, Taf. ii. fig. 3). He found also that the peculiar +diploconical skeleton is not composed of silex, but of acanthin. In the +explanation of the shell-structure he adopted my opinion. + +In the rich collections of the Challenger I detected ten different forms of +Diploconida, all very rare, and for the most part represented only by +single specimens. A twelfth species was found by me in the collection of +Captain Rabbe from the Indian Ocean. By the study of these new forms, and +particularly by their comparison with the most nearly allied Hexalaspida +and Belonaspida, it was possible for me to correct some errors in my former +description and to give a much more correct description and natural +explanation of this very peculiar and strange family of Radiolaria (compare +Pl. 140). + +The most characteristic and the most voluminous part of the acanthinic +skeleton in all Diploconida appears as the diploconical or nearly +cylindrical solid "mantle" giving them their name and odd appearance (Pl. +140). Usually this mantle is broader on its two opposite terminal openings +than in its more or less constricted middle part. This latter is now more +spherical or ellipsoidal, now more lenticular, and usually separated from +the two cones by two slight transverse strictures. On the surface of this +middle part twelve to eighteen radial spines, which in _Diplocolpus_ are +rudimentary or absent, are visible in _Diploconus_. The longitudinal axis +of this shell is constantly occupied by a very large pair of opposite stout +prismatic or cylindrical principal spines, which are united in the centre +and usually more or less prominent with their distal apex over the two +openings of the double cone. + +In my first communication on the _Diploconus_ (1862, _loc. cit._) I +correctly compared these two large spines in the prolonged main axis of the +shell to the principal equatorial spines of _Amphilonche_ (or to the +"hydrotomical spines," _c_1, _c_3); but my explanation of the two peculiar +cones enveloping them was erroneous. I supposed at that time that they were +formed by the eight flattened and leaf-shaped curved {883}tropical spines, +so that around each principal spine the four neighbouring tropical spines +(two of the northern and two of the southern hemisphere) had grow together +by their edges and formed the peculiar conical sheath. I can now say that +this opinion (afterwards adopted also by Hertwig) was quite erroneous, the +two conical or funnel-shaped sheaths being the enlarged basal sheaths of +the two hydrotomical spines, which we have already seen in the Hexalaspida +(Pl. 139). But whilst in these latter all six principal spines of the +hydrotomical meridian plane are hypertrophied (two equatorial and four +polar spines), in the nearly allied Diploconida only the two opposite +equatorial spines are developed, whilst all other eighteen spines are more +or less atrophied or quite rudimentary. In _Diploconus_ the latter are more +or less evident, whilst in _Diplocolpus_ they disappear externally. + +The true lattice-shell of the #Acanthophracta# (constantly composed of the +meeting apophyses of twenty radial spines) is therefore represented in the +Diploconida by the small roundish middle part of the whole shell, which is +usually much smaller than the two opposite cones, and separated from them +by the two slight transverse strictures. Usually this small but most +important middle part of the shell is very dark and opaque, on account of +its very thick wall and small pores; but in some species it is clear enough +to ascertain that the structure of this lattice-shell is the same as in the +lenticular Hexalaspida, there being a network of thick crests on the outer +surface and small pores in the dimples between them. Indeed, in many (and +probably in all) Diploconida the forty aspinal pores are present which we +found in all Hexalaspida, Belonaspida, and Diporaspida, so that these four +families of #Acanthophracta# represent one continuous phylogenetical +series; _Phractaspis_ among the Diporaspida is at the beginning, and +_Diplocolpus_ among the Diploconida at the end of this remarkably +transformed morphological series. + +The twenty radial spines in all Diploconida are probably united very firmly +(or even perfectly grown together) in the centre of the small thick-walled +lattice-shell, the inner space of which is extremely reduced. Probably, +too, the sutures between the meeting apophyses of the thick radial spines +are often (or even constantly) obliterated by concrescence, so that the +whole shell forms a single piece of acanthin. But I regret that I cannot +ascertain these and other points in the structure of the shell, as the +small number of specimens observed did not permit an anatomical examination +to be made. I have no doubt, however, that the structure of the whole of +the middle main part of the shell is quite the same as in the lenticular +shell of the thick-walled Hexalaspida, and that in both families each of +the twenty radial spines bears originally only two opposite apophyses. + +The characteristic mantle of the double cone of the Diploconida, or the +basal sheath of their two large, perfectly developed principal spines is +usually much larger than the shell itself, and more or less compressed from +both poles of the shortened geotomical axis. Therefore the transverse +section of the two cones is usually elliptical, more {884}rarely circular. +Their widest part is generally the distal opening; more rarely this is a +little constricted. The thin transparent lamella of acanthin, representing +the mantle of the double cone, is commonly ribbed or furrowed by +longitudinal, parallel or divergent crests, and elegantly denticulated on +the edge of the distal opening. + +The two conical or cylindrical halves of the mantle are connected with the +two enclosed principal spines not only at the base, where they arise from +the small central lattice-shell, but also throughout a certain part of +their length, by means of two, four, or six wings or leaves, which lie +opposite and in pairs in the meridian planes of those spines. These +meridian wings are more or less triangular (with broader concave outer +bases), and connected by their axial edge with the spine and by their +peripheral edge with the mantle. They separate two, four, or six conical +spaces or pyramidal compartments in each cone. But these aspinal +compartments and the separating septa are not new productions of the +Diploconida, but are inherited from their ancestral family, the Hexalaspida +(compare above, p. 873). + +The eighteen smaller spines in _Diploconus_ are either of nearly equal size +or more or less differentiated. The eight tropical spines are often much +larger than the eight polar spines. The two geotomical spines, (or the two +opposite equatorial spines of the shortened geotomical axis) are often +quite rudimentary. In _Diplocolpus_ the external part (outside the shell) +is in all eighteen smaller spines rudimentary or atrophied. + +_The Central Capsule_, as shown by Hertwig, contains numerous small nuclei, +and is divided into three parts by the above named two transverse +strictures; the smaller central part (in the original lenticular +lattice-shell) and the two opposite larger parts, filling up the greater +part of the two conical or cylindrical sheaths, and more or less adopting +their form. Corresponding to the shell itself the enclosed capsule is often +more or less flattened, being compressed at both poles of the geotomical +axis. The pseudopodia seem to proceed only from the two large polar +apertures of the sheaths, and form therefore two opposite conical tufts or +bunches. + +_Synopsis of the Genera of Diploconida._ + + All twenty spines more or less developed (sometimes + eight of them rudimentary), 380. _Diploconus_. + + Only the two hydrotomical spines developed (all the + eighteen others rudimentary), 381. _Diplocolpus_. + + + +Genus 380. _Diploconus_,[420] Haeckel, 1862, Monogr. d. Radiol., p. 404. + +_Definition._--#Diploconida# with two very large spines (opposite in the +hydrotomical axis) and ten to eighteen other much smaller spines externally +visible. + +{885}The genus _Diploconus_ must be derived from _Hexacolpus_ (among the +_Hexalaspida_) by the stronger development of the two hydrotomical spines +and their large sheaths; all the other eighteen spines are much smaller, +and usually devoid of prominent sheaths. Sometimes the eight tropical +spines are rudimentary. + + + +Subgenus 1. _Diploconulus_, Haeckel. + +_Definition._--Mantle of the double cone not compressed; its transverse +section therefore circular. + + +1. _Diploconus amalla_, n. sp. (Pl. 140, fig. 1). + +Mantle of the double cone thick walled, not compressed, its transverse +section circular; its contour little convex; its surface nearly smooth; its +distal margin regularly denticulated. Diameter of its mouth twice as large +as the equatorial diameter of the shell and one-third as long as its total +length. The two large spines prismatic, one-fourth longer than their +conical sheath. The eighteen smaller spines very thin, about half as long +as the former, a little curved. + +_Dimensions._--Length of the shell 0.3; equatorial breadth 0.05, polar +breadth 0.1. + +_Habitat._--Central Pacific, station 271, surface. + + +2. _Diploconus cyathiscus_, n. sp. (Pl. 140, fig. 3). + +Mantle of the double cone thin walled, not compressed; its transverse +section circular; its contour strongly convex; its surface with six +stronger and many smaller ribs; its margin with numerous straight and long, +parallel denticles. Diameter of its mouth half as long as the whole shell +and one and a half times as long as its equatorial diameter. The two +principal spines one-fourth longer than their conical sheath. The eighteen +smaller spines about half as long, thin, straight. Both geotomical spines +thick and short. + +_Dimensions._--Length of the shell 0.2; equatorial breadth 0.07, polar +breadth 0.1. + +_Habitat._--West Tropical Pacific, Station 225, surface. + + +3. _Diploconus cylindrus_, n. sp. + +Mantle of the double cone thick walled, dark, cylindrical, not compressed; +its transverse section circular; its contours straight, parallel; its +surface with strong parallel straight longitudinal ribs; its margin +irregularly dentated. Diameter of its mouth one-fifth as long as the whole +shell and two-thirds as long as the diameter of the equatorial +intumescence. The two principal spines prismatic, nearly twice as long as +their cylindrical sheath. The smaller spines about half as long, thin, +conical, straight. (Resembles the medial part of _Hexacolpus trypanon_, Pl. +140, fig. 11.) + +_Dimensions._--Length of the shell 0.25; equatorial breadth 0.08, polar +breadth 0.05. + +_Habitat._--North Pacific, Station 241, surface. + + + +{886}Subgenus 2. _Diploconium_, Haeckel. + +_Definition._--Mantle of the double cone compressed from both poles of the +shortened geotomical axis; its transverse section therefore elliptical. + + +4. _Diploconus fasces_, Haeckel. + + _Diploconus fasces_, Haeckel, 1862, Monogr. d. Radiol., p. 405, Taf. xx. + figs. 7, 8. + + _Diploconus fasces_, R. Hertwig, 1879, Organismus d. Radiol., p. 28, Taf. + ii. fig. 3. + +Mantle of the double cone compressed, with elliptical transverse section; +its contour straight; its surface with numerous longitudinal furrows; its +margin finely denticulated. Diameter of its mouth two-fifths as long as the +whole shell and three times as broad as its equatorial diameter. The two +main spines one-third longer than their conical sheath, four-edged. The +eighteen smaller spines thick and short, cylindrical or a little +compressed. + +_Dimensions._--Length of the shell 0.18; equatorial breadth 0.025, polar +breadth 0.07. + +_Habitat._--Mediterranean (Messina), surface. + + +5. _Diploconus cotyliscus_, n. sp. (Pl. 140, fig. 4). + +Mantle of the double cone compressed, thin walled, with elliptical +transverse section; its contour convex; surface and margin nearly smooth. +Diameter of its mouth half as long as the whole shell and twice as long as +its equatorial diameter. The two main spines scarcely longer than their +hemispherical sheath. The smaller spines conical, straight, nearly of the +same length. + +_Dimensions._--Length of the shell 0.3; equatorial breadth 0.08, polar +breadth 0.15. + +_Habitat._--Tropical Atlantic, Station 347, surface, + + +6. _Diploconus saturnus_, Haeckel. + + _Diploconus saturnus_, Haeckel, 1879, Natuerl. Schoepfungsgesch., Aufl. + vii. p. 706, Taf. xvi. fig. 11. + +Mantle of the double cone compressed, thick walled, with elliptical +transverse section; its contour convex; its surface with numerous deep and +irregular longitudinal furrows and marginal incisions. Diameter of its +mouth one-third as long as the whole shell and twice as broad as its +equatorial diameter. The two hydrotomical spines short, scarcely longer +than their sheath. The eighteen other spines thin, cylindrical, nearly of +the same length, curved. (Resembles a sheaf.) + +_Dimensions._--Length of the shell 0.24; equatorial breadth 0.04, polar +breadth 0.07. + +_Habitat._--South Pacific, Station 300, surface. + + +7. _Diploconus hexaphyllus_, n. sp. (Pl. 140, fig. 2). + +Mantle of the double cone compressed, thick walled, with elliptical +transverse section; its contour straight; surface with six stronger and +numerous smaller straight ribs and six marginal {887}denticulate incisions. +Diameter of its mouth one-third as long as the whole shell and somewhat +smaller than the equatorial diameter. Hydrotomical spines about twice as +long as their sheath, pyramidal, with emarginate point and six wings. +Geotomical spines short and strong, pyramidal. Sixteen other spines thin, +straight, conical. + +_Dimensions._--Length of the shell 0.3; equatorial breadth 0.11, polar +breadth 0.1. + +_Habitat._--Central Pacific, Station 266, surface. + + + +Genus 381. _Diplocolpus_,[421] n. gen. + +_Definition._--#Diploconida# with only two developed, very large spines +(opposite in the hydrotomical axis); all the other eighteen spines quite +rudimentary or externally atrophied. + +The genus _Diplocolpus_ is the last and the most modified genus among the +ACANTHARIA. The eighteen smaller spines of _Diploconus_ are here quite +rudimentary or have even perfectly disappeared by atrophy, so that the +shell seems to consist only of the large hydrotomical spines and their +enveloping sheaths. + + + +Subgenus 1. _Diplocolpulus_, Haeckel. + +_Definition._--Mantle of the double cone not compressed; its transverse +section therefore circular. + + +1. _Diplocolpus costatus_, n. sp. (Pl. 140, fig. 7). + +Mantle of the double cone thin walled, not compressed; its transverse +section circular or nearly hexagonal; its contour little convex; surface +with six thick longitudinal equidistant ribs and many thinner ribs between +them; margin denticulate. Transverse diameter of the shell one-third as +long as the longitudinal. The two hydrotomical spines thick and short, +little prominent over the polar mouth. No rudiments of other spines visible +externally. + +_Dimensions._--Length of the shell 0.15; equatorial and polar breadth 0.05. + +_Habitat._--Indian Ocean (Madagascar), Rabbe, surface. + + +2. _Diplocolpus cristatus_, n. sp. (Pl. 140, fig. 6). + +Mantle of the double cone thick walled, not compressed; its transverse +section circular or hexagonal; its contour nearly straight; surface with +six thick prominent longitudinal equidistant ribs; margin irregularly +dentated. Transverse diameter of the shell half as long as the +longitudinal. {888}The two hydrotomical spines very thick and short, +pyramidal, little prominent. Short rudiments of the eighteen other spines +present, bristle-shaped. + +_Dimensions._--Length of the shell 0.1, breadth 0.05. + +_Habitat._--South Atlantic, Station 335, surface. + + + +Subgenus 2. _Diplocolpium_, Haeckel. + +_Definition._--Mantle of the double cone compressed from both poles of the +shortened geotomical axis; its transverse section therefore elliptical. + + +3. _Diplocolpus serratus_, n. sp. (Pl. 140, fig. 5). + +Mantle of the double cone thick walled, compressed, with elliptical +transverse section; its surface with numerous delicate ribs; contour little +convex; margin regularly serrate. Hydrotomical spines short, pyramidal, +with six serrate wings. Transverse diameter of the shell nearly twice as +great at the polar mouth as at the equator and half as long as the whole +shell. + +_Dimensions._--Length of the shell 0.15; breadth on the equator 0.035, on +the poles 0.07. + +_Habitat._--Central Pacific, Station 274, surface. + + +4. _Diplocolpus dentatus_, n. sp. (Pl. 140, fig. 9). + +Mantle of the double cone thin walled, compressed, with elliptical +transverse section; its contour straight; surface with six deeper and +numerous shallower furrows; margin denticulated, with six triangular +prominent larger teeth. Hydrotomical spines very large prismatic, pyramidal +at the ends. Transverse diameter of the shell a little larger at the polar +mouth than at the equator and half as long as the whole shell. + +_Dimensions._--Length of the shell 0.2; breadth on the equator 0.08, on the +poles 0.1. + +_Habitat._--North Pacific, Station 244, surface. + + +5. _Diplocolpus sulcatus_, n. sp. (Pl. 140, fig. 8). + +Mantle of the double cone thin walled, compressed, with elliptical +transverse section; its contour straight; surface with twelve to sixteen +deep longitudinal furrows, which are separated by thin, undulating, double +edged ribs; margin little dentated. Hydrotomical spines short, pyramidal, +with six dentate wings. Transverse diameter of the shell a little larger at +the polar mouth than at the equator, about one-third of the whole length of +the shell. + +_Dimensions._--Length of the shell 0.17; breadth on the equator 0.05, on +the poles 0.06. + +_Habitat._--South Pacific, Station 291, surface. + + + + +Notes. + + [1] The numbers preceded by L. N. refer to the list of names of authors + in the Bibliography on p. clxxvi. + + [2] _Sitzungsb. med.-nat. Gesellsch. Jena_, February 16, 1883. + + [3] _Loc. cit._ + + [4] _Abhandl. d. k. Akad. d. Wiss. Berlin_, 1858, p. 28. + + [5] Monogr. d. Radiol., 1862, Taf. ii. p. 253. + + [6] Histologie der Radiolarien, pp. 43-73, Taf. iii.-v. + + [7] _Sitzungsb. med.-nat. Gesellsch. Jena_, February 16, 1883. + + [8] _Actissa_ = Radiant, [Greek: aktis]. + + [9] _Thalassolampe_ = Sea-scum; [Greek: thalassa] and [Greek: lampe]. + + [10] _Thalassopila_ = Sea-ball; [Greek: thalassa], [Greek: pila]. + + [11] _Thalassicolla_ = Sea-jelly, [Greek: thalassa], [Greek: kolla]. + + [12] _Thalassophysa_ = Sea-bladder; [Greek: thalassa], [Greek: physa.] + + [13] _Collozoum_ = Jelly-animal; [Greek: kolla], [Greek: zoon]. + + [14] _Thalassosphaera_ = Sea-sphere; [Greek: thalassa], [Greek: sphaira]. + + [15] Atlantic, vol. i. p. 233, fig. 51, 1877. + + [16] _Thalassoxanthium_ = Sea-burdock; [Greek: thalassa], [Greek: + xanthion.] + + [17] _Physematium_ = Small vesicle; [Greek: Physemation]. + + [18] _Thalassoplancta_ = Floating on the sea; [Greek: thalassoplankta]. + + [19] Compare _Thalassoplancta cavispicula_, Monogr. d. Radiol., 1862, p. + 261, Taf. iii. figs. 10-13. + + [20] _Lampoxanthium_ = Scum-burdock; [Greek: lampe], [Greek: xanthion]. + + [21] _Loc. cit._, Taf. xxxii., xxxiii. + + [22] _Belonozoum_ = Needle-animal; [Greek: belone], [Greek: zoon]. + + [23] _Sphaerozoum_ = Spherical animal; [Greek: sphaira], [Greek: zoon]. + + [24] _Rhaphidozoum_ = Needle-animal; [Greek: rhaphis], [Greek: zoon]. + + [25] Ethmosphaerida = Liosphaerida simplicia = Monosphaerida anacantha. + + [26] _Cenosphaera_ = Hollow sphere; [Greek: kenos], [Greek: sphaira]. + + [27] _Stigmosphaera_ = Sphere with central point; [Greek: stigma], [Greek: + sphaira]. + + [28] _Ethmosphaera_ = Sieve-sphere; [Greek: ethmos], [Greek: sphaira]. + + [29] _Sethosphaera_ = Sieve-sphere; [Greek: sethos], [Greek: sphaira]. + + [30] _Carposphaerida_ = Liosphaerida duplicia = Dyosphaerida anacantha. + + [31] _Carposphaera_ = Fruit-shaped sphere, [Greek: karpos], [Greek: + sphaira]. + + [32] _Liosphaera_ = Smooth sphere; [Greek: leios], [Greek: sphaira]. + + [33] Thecosphaerida = Liosphaerida triplicia = Triosphaerida anacantha. + + [34] _Thecosphaera_ = Capsule-sphere; [Greek: theke], [Greek: sphaira]. + + [35] _Rhodosphaera_ = Rose-sphere; [Greek: rhodon], [Greek: sphaira]. + + [36] Cromyosphaerida = Liosphaerida tetraplicia = Tetrasphaerida + anacantha. + + [37] _Cromyosphaera_ = Onion-sphere; [Greek: chromyon], [Greek: sphaira]. + + [38] Caryosphaerida = Liosphaerida multiplicia = Polysphaerida anacantha. + + [39] _Caryosphaera_ = Nut-sphere; [Greek: karyon], [Greek: sphaira]. + + [40] Plegmosphaerida = Liosphaerida spongiosa = Spongosphaerida anacantha. + + [41] _Styptosphaera_ = Hemp-sphere; [Greek: styptos], [Greek: sphaira]. + + [42] _Plegmosphaera_ = Sphere of wicker-work; [Greek: plegma], [Greek: + sphaira]. + + [43] _Spongoplegma_ = Spongy wickerwork; [Greek: spongos], [Greek: + plegma]. + + [44] _Spongodictyon_ = Spongy network; [Greek: spongos], [Greek: diktyon]. + + [45] _Loc. cit._, pp. 17, 55, 1858. + + [46] _Abhandl. d. k. Akad. d. Wiss. Berlin_, p. 55, 1858. + + [47] _Loc. cit._, p. 530, 1862. + + [48] _Loc. cit._, pp. 30, 133, 1879. + + [49] _Loc. cit._, p. 471, 1881. + + [50] _Loc. cit._, p. 535, Taf. xxxiv. fig. 1. + + [51] _Collosphaera_ = Jelly-sphere; [Greek: kolla], [Greek: sphaira]. + + [52] _Tribonosphaera_ = Cloak-sphere; [Greek: tribon], [Greek: sphaira]. + + [53] _Pharyngosphaera_ = Throat-sphere; [Greek: pharynx], [Greek: + sphaira]. + + [54] _Buccinosphaera_ = Trumpet-sphere; [Greek: bykane], [Greek: sphaira]. + + [55] _Acrosphaera_ = Pointed-sphere; [Greek: akros], [Greek: sphaira]. + + [56] _Odontosphaera_ = Teeth-sphere; [Greek: odous], [Greek: sphaira]. + + [57] _Choenicosphaera_ = Shell with coronel trepans; [Greek: choinike], + [Greek: sphaira]. + + [58] _Siphonosphaera_ = Sphere with tubes; [Greek: siphon], [Greek: + sphaira]. + + [59] _Mazosphaera_ = Teat-sphere; [Greek: mazos], [Greek: sphaira]. + + [60] _Trypanosphaera_ = Auger-sphere; [Greek: trypanon], [Greek: sphaira]. + + [61] _Caminosphaera_ = Chimney-sphere; [Greek: kaminos], [Greek: sphaira]. + + [62] _Solenosphaera_ = Sphere with tubules; [Greek: solen], [Greek: + sphaira]. + + [63] _Otosphaera_ = Shell with ears; [Greek: otosphaira]. + + [64] _Coronosphaera_ = Coronal-sphere; [Greek: korone], [Greek: sphaira]. + + [65] _Clathrosphaera_ = Lattice-sphere. + + [66] _Xanthiosphaera_ = Burdock-sphere; [Greek: xanthion], [Greek: + sphaira]. + + [67] Stylosphaerida = Sphaeroidea dissacantha, Prodromus, p. 449. + + [68] _Xiphosphaera_ = Sword-sphere; [Greek: xiphos], [Greek: sphaira]. + + [69] _Xiphostylus_ = Sword style; [Greek: xiphos], [Greek: stylos]. + + [70] _Saturnalis_ = Similar to _Saturnus_, with a ring. + + [71] _Stylosphaera_ = Sphere with styles; [Greek: stylos], [Greek: + sphaira]. + + [72] _Sphaerostylus_ = Sphere with styles; [Greek: sphaira], [Greek: + stylos]. + + [73] _Saturnulus_ = Small _Saturnus_, with a ring. + + [74] _Amphisphaera_ = Sphere with spines on both poles; [Greek: amphi], + [Greek: sphaira]. + + [75] _Amphistylus_ = Shell with styles on both poles; [Greek: amphi], + [Greek: stylos]. + + [76] _Saturninus_ = Similar to Saturnus, with a ring. + + [77] _Stylocromyum_ = Onion with styles; [Greek: stylos], [Greek: + kromyon]. + + [78] _Cromyostylus_ = Onion with styles; [Greek: kromyon], [Greek: + stylos]. + + [79] _Spongolonchis_ = Spongy shell with spears; [Greek: spongos], [Greek: + lonchis]. + + [80] _Spongostylus_ = Spongy shell with styles; [Greek: spongos], [Greek: + stylos]. + + [81] _Spongostylidium_, diminutive of _Spongostylus_. + + [82] Staurostylida = Staurosphaerida simplicia = Monosphaerida + tetracantha. + + [83] _Staurosphaera_ = Cross-sphere; [Greek: stauros], [Greek: sphaira]. + + [84] _Staurostylus_ = Cross-style; [Greek: stauros], [Greek: stylos]. + + [85] _Stylostaurus_, Style-cross; [Greek: stylos], [Greek: stauros]. + + [86] Staurolonchida = Staurosphaerida duplicia = Dyosphaerida tetracantha. + + [87] _Staurolonche_ = Crossed spear; [Greek: stauros], [Greek: lonche]. + + [88] _Staurancistra_ = Crossed fish-hook; [Greek: stauros], [Greek: + ankistra]. + + [89] _Staurolonchidium_ = Diminutive from _Staurolonche_. + + [90] _Stauroxiphos_ = Sword with cross; [Greek: stauros], [Greek: xiphos]. + + [91] Stauracontida = Staurosphaerida triplicia = Triosphaerida + tetracantha. + + [92] _Stauracontium_ = Crossed dart; [Greek: stauros], [Greek: akontion]. + + [93] Staurocromyida = Staurosphaerida quadruplicia = Tetrasphaerida + tetracantha. + + [94] _Staurocromyum_ = Cross-onion; [Greek: stauros], [Greek: kromyon]. + + [95] _Cromyostaurus_ = Onion-cross; [Greek: kromyon], [Greek: stauros]. + + [96] Staurocaryida = Staurosphaerida multiplicia = Polysphaerida + tetracantha. + + [97] _Staurocaryum_ = Cross-nut; [Greek: stauros], [Greek: karyon]. + + [98] Staurodorida = Staurosphaerida spongiosa = Spongosphaerida + tetracantha. + + [99] _Staurodoras_ = Crossed spear; [Greek: stauros], [Greek: doras]. + +[100] Hexastylida = Cubosphaerida simplicia = Monosphaerida hexacantha. + +[101] _Hexastylus_ = Shell with six styles; [Greek: hexa], [Greek: stylos]. + +[102] _Hexastylarium_ = Shell with six styles; derivation from + _Hexastylus_. + +[103] _Hexastylidium_ = Shell with six styles; derivation from + _Hexastylus_. + +[104] Hexalonchida = Cubosphaerida duplicia = Dyosphaerida hexacantha. + +[105] _Hexalonche_ = Shell with six spears; [Greek: hexalonche]. + +[106] _Hexancistra_ = Shell with six fish-hooks; [Greek: hexankistra]. + +[107] _Hexaloncharium_ = Shell with six spears; derivation from + _Hexalonche_. + +[108] _Hexalonchidium_ = Shell with six spears; derivation from + _Hexalonche_. + +[109] Hexacontida = Cubosphaerida triplicia = Triosphaerida hexacantha. + +[110] _Hexacontion_ = Shell with six darts; [Greek: hexakontion]. + +[111] _Hexadendron_ = Shell with six trees; [Greek: hexadendron]. + +[112] _Hexacontarium_ = Shell with six darts; derivation, from + _Hexacontion_. + +[113] Hexacromyida = Cubosphaerida quadruplicia = Tetrasphaerida + hexacantha. + +[114] _Hexacromyum_ = Onion with six rays; [Greek: hexa], [Greek: kromyon]. + +[115] Hexacaryida = Cubosphaerida multiplicia = Polysphaerida hexacantha. + +[116] _Cubosphaera_ = Sphere with three axes of a cubus; [Greek: kubos], + [Greek: sphaira]. + +[117] _Hexacaryum_ = Nut with six spines; [Greek: hexa], [Greek: karyon]. + +[118] Hexadorida = Cubosphaerida spongiosa = Spongosphaerida hexacantha. + +[119] _Cubaxonium_ = Shell with three axes like those of a cube; [Greek: + kubos], [Greek: axonion]. + +[120] _Hexadoras_ = Shell with six spears; [Greek: hexadoras]. + +[121] _Hexadoridium_ = Shell with six small spears; derivation from + _Hexadoras_. + +[122] _Acanthosphaera_ = Spiny sphere; [Greek: akantha], [Greek: sphaira]. + +[123] _Heliosphaera_ = Sun sphere; [Greek: helios], [Greek: sphaira]. + +[124] _Conosphaera_ = Sphere with cones; [Greek: konos], [Greek: sphaira]. + +[125] _Coscinomma_ = Sieve eye; [Greek: koskinon], [Greek: omma]. + +[126] _Cladococcus_ = Nucleus with branches; [Greek: klados], [Greek: + kokkos]. + +[127] _Elaphococcus_ = Shell with harts' horn-shaped spines; [Greek: + elaphos], [Greek: kokkos]. + +[128] Haliommida = Astrosphaerida duplicia = Dyosphaerida polycantha. + +[129] _Haliomma_ = Sea-eye; [Greek: hals], [Greek: omma]. + +[130] _Heliosoma_ = Sun-body; [Greek: helios], [Greek: soma]. + +[131] _Elatomma_ = Pine-eye; [Greek: elate], [Greek: omma]. + +[132] _Leptosphaera_ = Delicate sphere; [Greek: leptos], [Greek: sphaira]. + +[133] _Diplosphaera_ = Double sphere; [Greek: diploos], [Greek: sphaira]. + +[134] _Drymosphaera_ = Woody sphere; [Greek: drymos], [Greek: sphaira]. + +[135] _Astrosphaera_ = Star-sphere; [Greek: astron], [Greek: sphaira]. + +[136] Actinommida = Astrosphaerida triplicia = Triosphaerida polyacantha. + +[137] _Actinomma_ = Radiant eye; [Greek: aktis], [Greek: omma]. + +[138] _Echinomma_ = Urchin-eye; [Greek: echinos], [Greek: omma]. + +[139] _Pityomma_ = Pine-eye; [Greek: pitys], [Greek: omma]. + +[140] Cromyommida = Astrosphaerida quadruplicia = Tetrasphaeria + polyacantha. + +[141] _Cromyomma_ = Onion-eye; [Greek: kromyon], [Greek: omma]. + +[142] _Cromyechinus_ = Onion-shaped Urchin; [Greek: kromyon], [Greek: + echinos]. + +[143] _Cromyodrymus_ = Onion with trees; [Greek: kromyon], [Greek: drymos]. + +[144] Caryommida = Astrosphaerida multiplica = Polysphaeria polyacantha. + +[145] _Caryomma_ = Nut-eye; [Greek: karyon], [Greek: omma]. + +[146] _Arachnopila_ = Cobweb ball; [Greek: arachne], [Greek: pilos]. + +[147] _Arachnopegma_ = Cobweb-building; [Greek: arachne], [Greek: pegma]. + +[148] _Arachnosphaera_ = Cobweb-sphere; [Greek: arachne], [Greek: sphaira]. + +[149] Spongiommida = Astrosphaerida spongiosa = Spongosphaerida + polyacantha. + +[150] _Spongiomma_ = Spongy-eye; [Greek: spongia], [Greek: omma]. + +[151] _Spongodrymus_ = Spongy wood; [Greek: spongos], [Greek: drymos]. + +[152] _Spongechinus_ = Spongy Urchin; [Greek: spongos], [Greek: echinos]. + +[153] _Spongothamnus_ = Spongy shrub; [Greek: spongos], [Greek: thamnos]. + +[154] _Spongopila_ = Spongy ball; [Greek: spongos], [Greek: pilos]. + +[155] _Rhizoplegma_ = Root-shaped wicker-work; [Greek: rhiza], [Greek: + plegma]. + +[156] _Lychnosphaera_ = Lantern-sphere; [Greek: lychnos], [Greek: sphaira]. + +[157] _Centrocubus_ = Shell with a central cube; [Greek: kentron], [Greek: + kubos]. + +[158] _Octodendron_ = Shell with eight trees; [Greek: okto], [Greek: + dendron]. + +[159] _Spongosphaera_ = Spongy sphere; [Greek: spongos], [Greek: sphaira]. + +[160] _Rhizosphaera_ = Root-sphere; [Greek: rhiza], [Greek: sphaira]. + +[161] _Cenellipsis_ = Hollow ellipsoid; [Greek: kenos], [Greek: elleipsis]. + +[162] _Axellipsis_ = Ellipsoid with an axial beam; [Greek: axis], [Greek: + elleipsis]. + +[163] _Ellipsidium_ = Small ellipsoid; [Greek: elleipsidion]. + +[164] _Ellipsoxiphus_ = Ellipsoid with swords; [Greek: elleipsis], [Greek: + xiphos]. + +[165] _Axoprunum_ = Plum with axis; [Greek: axis], [Greek: prounon]. + +[166] _Ellipsostylus_ = Ellipsoid with styles; [Greek: elleipsis], [Greek: + stylos]. + +[167] _Lithomespilus_ = Siliceous medlar; [Greek: lithos], [Greek: + mespilos]. + +[168] _Lithapium_ = Siliceous pear; [Greek: lithos], [Greek: apion]. + +[169] _Pipettella_ = Small pipette. + +[170] _Druppula_ = Small drupe or [Greek: druppa], ripe Olive. + +[171] _Druppocarpus_ = Olive-fruit; [Greek: druppa], [Greek: karpos]. + +[172] _Prunulum_ = Little-plum. + +[173] _Prunocarpus_ = Plum fruit; [Greek: prounon], [Greek: karpos]. + +[174] _Cromyodruppa_ = Onion-olive; [Greek: kromyon], [Greek: druppa]. + +[175] _Cromyocarpus_ = Onion fruit; [Greek: kromyon], [Greek: karpos]. + +[176] _Lithatractus_ = Spindle of silex; [Greek: lithos], [Greek: + atraktos]. + +[177] _Druppatractus_ = Spindle-like olive; [Greek: druppa], [Greek: + atraktos]. + +[178] _Stylatractus_ = Spindle with styles; [Greek: stylos], [Greek: + atraktos]. + +[179] _Xiphatractus_ = Sword-spindle; [Greek: xiphos], [Greek: atraktos]. + +[180] _Cromyatractus_ = Onion-spindle; [Greek: kromyon], [Greek: atraktos]. + +[181] _Pipetta_ = Small pipe. + +[182] _Pipettaria_ = _Pipetta_-like. + +[183] _Spongellipsis_ = Spongy ellipsoid; [Greek: spongos], [Greek: + elleipsis]. + +[184] _Spongurus_ = Spongy tail; [Greek: spongos], [Greek: oura]. + +[185] _Spongocore_ = Spongy puppet; [Greek: spongos], [Greek: kore]. + +[186] _Spongoprunum_ = Spongy plum; [Greek: spongos], [Greek: prounon]. + +[187] _Spongodruppa_ = Spongy olive-fruit; [Greek: spongos], [Greek: + druppa]. + +[188] _Spongatractus_ = Spongy-spindle; [Greek: spongos], [Greek: + atraktos]. + +[189] _Spongoliva_ = Spongy olive; [Greek: spongos], [Greek: eleia]. + +[190] _Spongoxiphus_ = Spongy sword; [Greek: spongos], [Greek: xiphos]. + +[191] _Artiscus_ = Small loaf; [Greek: artiskos]. + +[192] _Stylartus_ = Bread with styles; [Greek: stylos], [Greek: artos]. + +[193] _Cannartus_ = Leaf with tubes; [Greek: kanna], [Greek: artos]. + +[194] _Cyphanta_ = [Greek: Kyphanta], Mediterranean port in Laconia. + +[195] _Cyphonium_ = Roundish vessel; [Greek: kyphonion]. + +[196] _Cypassis_ = [Greek: kypassis]; A girl's girdle. + +[197] _Cyphocolpus_ = Vaulted-bosom; [Greek: kyphos], [Greek: kolpos]. + +[198] _Cyphinus_ = [Greek: kyphinos]; derivation from [Greek: kyphos] = + roundish vessel, a kind of fruit. + +[199] _Cyphinidium_ = Small Cyphinus; [Greek: kyphinidion]. + +[200] _Cannartiscus_ = Small loaf with tubes; [Greek: kanna], [Greek: + artiskos]. + +[201] _Cannartidium_ = Small loaf with tubules; [Greek: kanna], [Greek: + artidion]. + +[202] _Panartus_ = quite bread-like; [Greek: panartos]. + +[203] _Peripanartus_ = _Panartus_ with mantle; [Greek: peripanartos]. + +[204] _Panicium_ = A kind of bread. + +[205] _Peripanicium_ = _Panicium_ with mantle. + +[206] _Panarium_ = Bread-basket. + +[207] _Peripanarium_ = _Panarium_ (or bread-basket) with mantle. + +[208] _Ommatocampe_ = Caterpillar with eyes; [Greek: omma], [Greek: kampe]. + +[209] _Ommatartus_ = Loaf with eyes; [Greek: omma], [Greek: artos]. + +[210] _Desmocampe_ = Chain-like caterpillar; [Greek: desmos], [Greek: + kampe]. + +[211] _Desmartus_ = Chain-like loaf; [Greek: desmos], [Greek: artos]. + +[212] _Zygocampe_ = Caterpillar with paired joints; [Greek: zygon], [Greek: + kampe]. + +[213] _Zygartus_ = Loaf with paired joints; [Greek: zygon], [Greek: artos]. + +[214] _Cenodiscus_ = Hollow disk; [Greek: kenos], [Greek: diskos]. + +[215] _Zonodiscus_ = Disk with girdle; [Greek: zone], [Greek: diskos]. + +[216] _Stylodiscus_ = Disk with styles; [Greek: stylos], [Greek: diskos]. + +[217] _Theodiscus_ = Divine disk; [Greek: theos], [Greek: diskos]. + +[218] _Crucidiscus_ = Disk with cross. + +[219] _Trochodiscus_ = Wheel-disk; [Greek: trochos], [Greek: diskos]. + +[220] _Sethodiscus_ = Sieve-disk; [Greek: sethos], [Greek: diskos]. + +[221] _Phacodiscus_ = Lenticular disk; [Greek: phakos], [Greek: diskos]. + +[222] _Periphaena_ = Shell with transparent girdle; [Greek: periphaina]. + +[223] _Perizona_ = Shell with surrounding girdle; [Greek: peri], [Greek: + zone]. + +[224] _Sethostylus_ = Sieve with styles; [Greek: sethos], [Greek: stylos]. + +[225] _Phacostylus_ = Lens with styles; [Greek: phakos], [Greek: stylos]. + +[226] _Triactiscus_ = Shell with three rays; [Greek: triaktiskos]. + +[227] _Sethostaurus_ = Sieve-cross; [Greek: sethos], [Greek: stauros]. + +[228] _Phacostaurus_ = Lens with cross; [Greek: phakos], [Greek: stauros]. + +[229] _Distriactis_ = Shell with twice three rays; [Greek: distriaktis]. + +[230] _Heliosestrum_ = Sun-sieve; [Greek: helios], [Greek: sestron]. + +[231] _Astrosestrum_ = Stellated sieve; [Greek: astron], [Greek: sestron]. + +[232] _Heliodiscus_ = Sun-disk; [Greek: helios], [Greek: diskos]. + +[233] _Heliodrymus_ = Sun-forest; [Greek: helios], [Greek: drymos]. + +[234] _Astrophacus_ = Star-lens; [Greek: astron], [Greek: phakos]. + +[235] _Lithocyclia_ = Circular stone; [Greek: lithos], [Greek: kyklion]. + +[236] _Coccodiscus_ = Disk with nucleus; [Greek: kokkos], [Greek: diskos]. + +[237] _Stylocyclia_ = Circular shell with styles; [Greek: stylos], [Greek: + kyklion]. + +[238] _Amphicyclia_ = Circular shell with spines on both sides; [Greek: + amphi], [Greek: kyklion]. + +[239] _Trigonocyclia_ = Triangular shell with circular rings; [Greek: + trigonon], [Greek: kyklion]. + +[240] _Staurocyclia_ = Circular shell with four crossed spines; [Greek: + stauros], [Greek: kyklia]. + +[241] _Astrocyclia_ = Stellated circular shell; [Greek: astron], [Greek: + kyklion]. + +[242] _Coccocyclia_ = Circular shell with nucleus; [Greek: kokkos], [Greek: + kyklios]. + +[243] _Diplactura_ = Stellated shell with double tail; [Greek: diplous], + [Greek: aktis], [Greek: oura]. + +[244] _Amphiactura_ = Stellated shell with tail on both sides; [Greek: + amphi], [Greek: aktis], [Greek: oura]. + +[245] _Trigonactura_ = Triangular shell with three rays; [Greek: trigonon], + [Greek: aktis], [Greek: oura]. + +[246] _Hymenactura_ = Star-shaped shell with membrane between the rays; + [Greek: hymen], [Greek: aktis], [Greek: oura]. + +[247] _Astractura_ = Star-shaped shell with many rays; [Greek: astron], + [Greek: aktis], [Greek: oura]. + +[248] _Stauractura_ = Cruciform shell with four rays; [Greek: stauros], + [Greek: aktis], [Greek: oura]. + +[249] _Pentactura_ = Stellated shell with five rays; [Greek: pente], + [Greek: aktis], [Greek: oura]. + +[250] _Echinactura_ = _Echinus_-like shell with five rays; [Greek: + echinos], [Greek: aktis], [Greek: oura]. + +[251] _Archidiscus_ = Primordial disk; [Greek: archidiskos]. + +[252] _Axodiscus_ = Disk with certain axes; [Greek: axis], [Greek: diskos]. + +[253] _Porodiscus_ = Porous disk; [Greek: poros], [Greek: diskos]. + +[254] _Perichlamydium_ = Shell surrounded by a mantle; [Greek: peri], + [Greek: chlamydion]. + +[255] _Ommatodiscus_ = Disk with eyes; [Greek: omma], [Greek: diskos]. + +[256] _Stomatodiscus_ = Disk with openings; [Greek: stoma], [Greek: + diskos]. + +[257] _Xiphodictya_ = Net with swords; [Greek: xiphos], [Greek: diktyon]. + +[258] _Tripodictya_ = Net with tripod; [Greek: tripous], [Greek: diktyon]. + +[259] _Staurodictya_ = Cross-net; [Greek: stauros], [Greek: diktyon]. + +[260] _Stylodictya_ = Net with styles; [Greek: stylos], [Greek: diktyon]. + +[261] _Stylochlamydium_ = Shell with styles and mantle; [Greek: stylos], + [Greek: chlamydion]. + +[262] _Amphibrachium_ = Shell with two arms; [Greek: amphi], [Greek: + brachion]. + +[263] _Amphymenium_ = Shell with veil on both sides; [Greek: amphi], + [Greek: hymenion]. + +[264] _Amphirrhopalum_ = Shell with clubs on both sides; [Greek: amphi], + [Greek: rhopalon]. + +[265] _Amphicraspedum_ = Shell with borders on both sides; [Greek: amphi], + [Greek: kraspedon]. + +[266] _Dictyastrum_ = Reticulated star; [Greek: diktyon], [Greek: astron]. + +[267] _Rhopalastrum_ = Club-star; [Greek: rhopalon], [Greek: astron]. + +[268] _Hymeniastrum_ = Membranous star; [Greek: hymen], [Greek: astron]. + +[269] _Euchitonia_ = Nice shell; [Greek: eu], [Greek: chitonia]. + +[270] _Chitonastrum_ = Star-shell; [Greek: chitonia], [Greek: astron]. + +[271] _Trigonastrum_ = Triangular star; [Greek: trigonon], [Greek: astron]. + +[272] _Stauralastrum_ = Crossed sea-star; [Greek: stauros], [Greek: hals], + [Greek: astron]. + +[273] _Hagiastrum_ = Holy starrulet; [Greek: hagion], [Greek: astron]. + +[274] _Histiastrum_ = Star with enveloping tissue; [Greek: histion], + [Greek: astron]. + +[275] _Tessarastrum_ = Starrulet with four rays; [Greek: tessara], [Greek: + astron]. + +[276] _Stephanastrum_ = Garland-starrulet; [Greek: stephanos], [Greek: + astron]. + +[277] _Dicranastrum_ = Fork-starrulet; [Greek: dikranon], [Greek: astron]. + +[278] _Myelastrum_ = Medullary starrulet; [Greek: myelos], [Greek: astron]. + +[279] _Pentalastrum_ = Little sea-star with five rays; [Greek: pente], + [Greek: hals], [Greek: astron]. + +[280] _Pentinastrum_ = Starrulet with five rays; [Greek: pente], [Greek: + inos], [Greek: astron]. + +[281] _Pentophiastrum_ = Starrulet with five snakes; [Greek: pente], + [Greek: ophis], [Greek: astron]. + +[282] _Hexalastrum_ = Little sea-star with six rays; [Greek: hexa], [Greek: + hals], [Greek: astron]. + +[283] _Hexinastrum_ = Starrulet with six rays; [Greek: hexa], [Greek: + inos], [Greek: astron]. + +[284] _Triolena_ = Shell with three arms; [Greek: tria], [Greek: olene]. + +[285] _Triopyle_ = With three gate-openings; [Greek: tria], [Greek: pyle]. + +[286] _Triodiscus_ = Disk with three openings; [Greek: triodiskos]. + +[287] _Pylolena_ = Disk with alternating gates and arms; [Greek: pyle], + [Greek: olene]. + +[288] _Hexapyle_ = With six gate-openings; [Greek: hexa], [Greek: pyle]. + +[289] _Pylodiscus_ = Disk with gates; [Greek: pyle], [Greek: diskos]. + +[290] _Discozonium_ = Disk with girdle; [Greek: diskos], [Greek: zonion]. + +[291] _Discopyle_ = Disk with gate; [Greek: diskos], [Greek: pyle]. + +[292] _Spongodiscus_ = Spongy disk; [Greek: spongos], [Greek: diskos]. + +[293] _Spongophacus_ = Spongy lens; [Greek: spongos], [Greek: phakos]. + +[294] _Spongolonche_ = Spongy disk with spontoons; [Greek: spongos], + [Greek: lonche]. + +[295] _Spongotripus_ = Spongy disk with tripod; [Greek: spongos], [Greek: + tripous]. + +[296] _Spongostaurus_ = Spongy disk with crossed spines; [Greek: spongos], + [Greek: stauros]. + +[297] _Stylotrochus_ = Wheel with styles; [Greek: stylos], [Greek: + trochos]. + +[298] _Spongotrochus_ = Spongy wheel; [Greek: spongos], [Greek: trochos]. + +[299] _Spongolena_ = Spongy disk with two arms; [Greek: spongos], [Greek: + olene]. + +[300] _Spongobrachium_ = Spongy shell with two arms; [Greek: spongos], + [Greek: brachion]. + +[301] _Rhopalodictyum_ = Network with clubs; [Greek: rhopalon], [Greek: + diktyon]. + +[302] _Dictyocoryne_ = Net with clubs; [Greek: diktyon], [Greek: koryne]. + +[303] _Spongasteriscus_ = Spongy star; [Greek: spongos], [Greek: + asteriskos]. + +[304] _Spongaster_ = Spongy star; [Greek: spongos], [Greek: aster]. + +[305] _Cenolarcus_ = Hollow basket; [Greek: kenos], [Greek: larkos]. + +[306] _Larcarium_ = A kind of basket; [Greek: larkarion]. + +[307] _Coccolarcus_ = Basket with kernel; [Greek: kokkos], [Greek: larkos]. + +[308] _Larcidium_ = Little basket, diminutive of _Larcus_; [Greek: + larkidion]. + +[309] _Spongolarcus_ = Spongy basket; [Greek: spongos], [Greek: larkos]. + +[310] _Stypolarcus_ = Hemp basket; [Greek: stype], [Greek: larkos]. + +[311] _Larnacilla_ = Little chest, diminutive of _Larnax_; [Greek: larnax]. + +[312] _Larnacidium_ = Little chest, diminutive of Larnax; [Greek: larnax]. + +[313] _Larnacalpis_ = Tankard-shaped chest; [Greek: larnax], [Greek: + kalpis]. + +[314] _Larnacantha_ = Chest with spines; [Greek: larnax], [Greek: akantha]. + +[315] _Larnacoma_ = Shell of chest form; [Greek: larnax]. + +[316] _Larnacospongus_ = Spongy chest; [Greek: larnax], [Greek: spongos]. + +[317] _Larnacostupa_ = Chest with hemp envelop; [Greek: larnax], [Greek: + stupe]. + +[318] _Monozonium_ = With one girdle; [Greek: monozonion]. + +[319] _Dizonium_ = With two girdles; [Greek: dizonion]. + +[320] _Trizonium_ = With three girdles; [Greek: trizonion]. + +[321] _Amphipyle_ = With one gate on both sides; [Greek: amphi], [Greek: + pyle]. + +[322] _Tetrapyle_ = With four gate-openings; [Greek: tetrapyle]. + +[323] _Octopyle_ = With eight gate-openings; [Greek: okto], [Greek: pyle]. + +[324] _Pylonium_ = Building with gates; [Greek: pylonion]. + +[325] _Amphipylonium_ = With one large gate on either side; [Greek: amphi], + [Greek: pylonion]. + +[326] _Tetrapylonium_ = Building with four gates; [Greek: tetra], [Greek: + pylonion]. + +[327] _Pylozonium_ = Shell with gates and girdles; [Greek: pyle], [Greek: + zonion]. + +[328] _Tholartus_ = Cupola-bread; [Greek: tholos], [Greek: artos]. + +[329] _Tholodes_ = Cupola-shaped; [Greek: tholodes] _vel_ [Greek: + tholoeides]. + +[330] _Amphitholus_ = Shell with two opposite cupolas; [Greek: amphi], + [Greek: tholos]. + +[331] _Amphitholonium_ = Small shell with two opposite cupolas; [Greek: + amphi], [Greek: tholonion]. + +[332] _Tholostaurus_ = Cross of four cupolas; [Greek: tholos], [Greek: + stauros]. + +[333] _Tholoma_ = Dome-building; [Greek: tholoma]. + +[334] Alternating, [Greek: metallasson]. + +[335] _Staurotholus_ = Cupolas cross-wise disposed; [Greek: stauros], + [Greek: tholos]. + +[336] _Staurotholonium_ = Small shell with cupolas cross-wise disposed; + [Greek: stauros], [Greek: tholonion]. + +[337] _Tholocubus_ = Cube with six cupolas on its sides; [Greek: tholos], + [Greek: kubos]. + +[338] _Tholonium_ = Shell with cupolas; [Greek: tholonion]. + +[339] _Cubotholus_ = Shell with cupolas disposed on six cube-sides; [Greek: + kubos], [Greek: tholos]. + +[340] _Cubotholonium_ = Small shell with cupolas disposed on the six sides + of a cube; [Greek: kubos], [Greek: tholonion]. + +[341] _Zonarium_ = Small girdle; [Greek: zonarion]. + +[342] _Zoniscus_ = Elegant girdle; [Greek: zoniskos]. + +[343] _Zonidium_ = Little girdle; [Greek: zonidion]. + +[344] _Spirema_ = Convolution, turning; [Greek: speirema]. + +[345] _Lithelius_ = Stony sun; [Greek: lithos], [Greek: helios]. + +[346] _Larcospira_ = Spiral basket; [Greek: larkos], [Greek: speira]. + +[347] _Pylospira_ = Spiral shell with internal gates; [Greek: pyle], + [Greek: speira]. + +[348] _Tholospira_ = Shell with spiral domes; [Greek: tholos], [Greek: + speira]. + +[349] _Spironium_ = Shell with spiral structure; [Greek: speironion]. + +[350] _Streblonia_ = Screw-shell; [Greek: streblonion]. + +[351] _Streblacantha_ = Screw-shell with spines; [Greek: streble], [Greek: + akantha]. + +[352] _Streblopyle_ = Screw-shell with gates; [Greek: streble], [Greek: + pyle]. + +[353] _Phorticium_ = Small vessel; [Greek: phortikion]. + +[354] _Spongophortis_ = Spongy vessel; [Greek: spongos], [Greek: phortis]. + +[355] _Soreuma_ = [Greek: soreuma], heap. + +[356] _Sorolarcus_ = Basket heap; [Greek: soros], [Greek: larkos]. + +[357] _Actinelius_ = Radiant sun; [Greek: aktis], [Greek: helios]. + +[358] _Astrolophus_ = Star-like bunch; [Greek: astron], [Greek: lophos]. + +[359] _Actinastrum_ = Radiant star; [Greek: aktis], [Greek: astron]. + +[360] _Litholophus_ = Stony brush; [Greek: lithos], [Greek: lophos]. + +[361] _Chiastolus_ = With crossed arms; [Greek: chiastos], [Greek: olos]. + +[362] _Acanthochiasma_ = Spine-cross; [Greek: akantha], [Greek: chiasma]. + +[363] _Acanthometron_ = Spine proportion; [Greek: akantha], [Greek: + metron]. + +[364] _Zygacantha_ = Spines opposite in pairs; [Greek: zyga], [Greek: + akantha]. + +[365] _Acanthonia_ = Spiny article; [Greek: akantha], [Greek: onia]. + +[366] _Lithophyllium_ = With stony leaves; [Greek: lithos], [Greek: + phyllion]. + +[367] _Phractacantha_ = Spines enclosed by a hedge; [Greek: phraktos], + [Greek: akantha]. + +[368] _Doracantha_ = Spear-like spine; [Greek: dory], [Greek: akantha]. + +[369] _Astrolonche_ = Star-spear; [Greek: astron], [Greek: lonche]. + +[370] _Xiphacantha_ = Sword spine; [Greek: xiphos], [Greek: akantha]. + +[371] _Stauracantha_ = Cruciate spine; [Greek: stauros], [Greek: akantha]. + +[372] _Phatnacantha_ = Spine with fretwork; [Greek: phatne], [Greek: + akantha]. + +[373] _Pristacantha_ = Saw-spine; [Greek: pristos], [Greek: akantha]. + +[374] _Acanthostaurus_ = Spine-cross; [Greek: akantha], [Greek: stauros]. + +[375] _Belonostaurus_ = Needle cross; [Greek: belone], [Greek: stauros]. + +[376] _Lonchostaurus_ = Spear-cross; [Greek: lonche], [Greek: stauros]. + +[377] _Zygostaurus_ = Pair-cross; [Greek: zygon], [Greek: stauros]. + +[378] _Quadrilonche_ = Square-spear. + +[379] _Xiphoptera_ = Sword-wing; [Greek: xiphos], [Greek: pteron]. + +[380] _Lithoptera_ = Stone wing; [Greek: lithos], [Greek: pteron]. + +[381] _Amphilonche_ = With two opposed spears; [Greek: amphi], [Greek: + lonche]. + +[382] _Amphibelone_ = With two opposed needles; [Greek: amphi], [Greek: + belone]. + +[383] _Acantholonche_ = Spiny spear; [Greek: akantha], [Greek: lonche]. + +[384] _Sphaerocapsa_ = Spherical capsule; [Greek: sphaira], [Greek: kapsa]. + +[385] _Astrocapsa_ = Star-capsule; [Greek: astron], [Greek: kapsa]. + +[386] _Porocapsa_ = Porous capsule; [Greek: poros], [Greek: kapsa]. + +[387] _Cannocapsa_ = Tubular capsule; [Greek: kanna], [Greek: kapsa]. + +[388] _Cenocapsa_ = Hollow Capsule; [Greek: kenos], [Greek: kapsa]. + +[389] _Phractaspis_ = Hedging shield; [Greek: phraktos], [Greek: aspis]. + +[390] _Pleuraspis_ = Shield formed by ribs; [Greek: pleura], [Greek: + aspis]. + +[391] _Dorataspis_ = Spear on the shield; [Greek: dory], [Greek: aspis]. + +[392] _Diporaspis_ = Shield with two pores; [Greek: diporos], [Greek: + aspis]. + +[393] _Orophaspis_ = Roof shield; [Greek: orophos], [Greek: aspis]. + +[394] _Ceriaspis_ = Dimply shield; [Greek: kerion], [Greek: aspis]. + +[395] _Hystrichaspis_ = Porcupine-shield; [Greek: hystrix], [Greek: aspis]. + +[396] _Coscinaspis_ = Sieve-shield; [Greek: koskinon], [Greek: aspis]. + +[397] _Acontaspis_ = Shield with spears; [Greek: akontion], [Greek: aspis]. + +[398] _Stauraspis_ = Cross-shield; [Greek: stauros], [Greek: aspis]. + +[399] _Echinaspis_ = Urchin with shields; [Greek: echinos], [Greek: aspis]. + +[400] _Zonaspis_ = Shell with a girdle of shield; [Greek: zone], [Greek: + aspis]. + +[401] _Dodecaspis_ = Shell with twelve shields; [Greek: dodeka], [Greek: + aspis]. + +[402] _Tessaraspis_ = Shield with four pores; [Greek: tessara], [Greek: + aspis]. + +[403] _Lychnaspis_ = Lantern-shield; [Greek: lychnos], [Greek: aspis]. + +[404] _Icosaspis_ = Shell with twenty shields; [Greek: eikosi], [Greek: + aspis]. + +[405] _Hylaspis_ = Forest shield; [Greek: hyle], [Greek: aspis]. + +[406] _Phractopelta_ = Hedging shield; [Greek: phraktos], [Greek: pelte]. + +[407] _Pantopelta_ = Shell everywhere with shields; [Greek: pante], [Greek: + pelte]. + +[408] _Octopelta_ = Shell with eight shields; [Greek: okto], [Greek: + pelte]. + +[409] _Dorypelta_ = Spear with a light shield; [Greek: dory], [Greek: + pelte]. + +[410] _Stauropelta_ = Cross-shield; [Greek: stauros], [Greek: pelte]. + +[411] _Thoracaspis_ = Cuirass-shield; [Greek: thorax], [Greek: aspis]. + +[412] _Belonaspis_ = Arrow-shield; [Greek: belone], [Greek: aspis]. + +[413] _Dictyaspis_ = Net-shield; [Greek: diktyon], [Greek: aspis]. + +[414] _Coleaspis_ = Shield with sheaths; [Greek: koleos], [Greek: aspis]. + +[415] _Phatnaspis_ = Panel-shield or fretwork; [Greek: phatne], [Greek: + aspis]. + +[416] _Hexalaspis_ = Shield with six wings; [Greek: hexalos], [Greek: + aspis]. + +[417] _Hexaconus_ = Shell with six cones; [Greek: hexa], [Greek: konos]. + +[418] _Hexonaspis_ = Shield with six auricles; [Greek: hexonos], [Greek: + aspis]. + +[419] _Hexacolpus_ = Shell with six bosoms; [Greek: hexa], [Greek: kolpos]. + +[420] _Diploconus_ = Double cone; [Greek: diploos], [Greek: konos]. + +[421] _Diplocolpus_ = Double bosom; [Greek: diploos], [Greek: kolpos]. + + + + + * * * * * + + + + +Corrections made to printed text + +Page iii, s 7: 'Radiolaria' corrected from 'Radioloria'. + +Page xiv, s 29: 'Octodendron' corrected from 'Octodendrum'. + +Page xvii, s 36: 'allopolar' corrected from 'alloplar'. + +Page xxii, s 47: 'rhombic' corrected from 'rombic'. + +Page xxvi, s 54B: 'Capsule' corrected from 'Caspule'. + +Page xxxiii, s 63: 'Thalassosphaerida' corrected from 'Thallassosphaerida'. + +Page xxxv, s 66.5: 'Nassellaria' corrected from 'Nasellaria'. + +Page xlvii, s 77A: 'Mediterranean' corrected from 'Meditteranean'. + +Page lxxvi, s 112: 'Phaeodinida' corrected from 'Phoeodinida'; +'Cannorrhaphida' from 'Cannorhaphida'. + +Page lxxxvi, s 131: Heliosphaera referred to Pl. 28, figs. 1-3 but these +are not of this genus. + +Page xciv, s 142B: 'Sphaerozoea' corrected from 'Sphaeozoea'. + +Page xcix s 151: Reference to 's 213' corrected from 's 273'. + +Page cx, s 166: 'interrupted' corrected from 'interruped'. + +Page clxxiii, s 249: 'Cannorrhaphida' corrected from 'Cannorrhapida'. + +Page clxxix, s 252: 'Karl' (Brandt) corrected from 'Karlt'. + +Page clxxxii, s 252: 'Kenntniss' corrected from 'Kentniss'. + +Page 29, Thalassosphaerida, definition: 'Cannorrhaphida' corrected from +'Cannorhaphida'. + +Page 36, Thalassoplancta, definition: 'Cannorrhaphis' corrected from +'Cannorhaphis'. + +Page 43, Sphaerozoum armatum: 'fig. 9' corrected from 'figs. 1, 9'. + +Page 85, Cromyosphaera antarctica refers to Pl. 30, fig. 8 but that does +not show this species + +Page 87, Genus 26: 'Liosphaerida' corrected from 'Liospaerida'. + +Page 99, Buccinosphaera invaginata, crystals: '0.008' corrected from +'0.088'. + +Ib., Buccinosphaera tubaria, pores: '0.008 to 0.012' corrected from '0.008 +to 0.002' (cf. "three to four times as broad as the bars"). + +Page 130, Xiphostylus alca: 'Pl. 13' corrected from 'Pl. 14'. + +Page 132, Saturnalis annularis, major axis: '0.27 to 0.3' corrected from +'0.27 to 0.03'. + +Page 137, Stylosphaera jugata, pores: '0.005 to 0.02' corrected from '0.005 +to 0.002'. + +Page 141, Sphaerostylus ophidium, pores: '0.005 to 0.008' corrected from +'0.05 to 0.008'. + +Page 201, Hexacromyida, definition: 'concentric' corrected from +'concentic'. + +Page 203, Cubosphaera concentrica, dimensions (A) and (B): '0.02' and +'0.04' corrected from '0.2', '0.4' (cf. the given radial proportions). + +Page 222, Coscinomma: 'n. gen.' corrected from 'n. sp.'. + +Page 224, Cladococcinus: 'Subgenus' corrected from 'Sugenus'. + +Page 241, Heliosoma hastatum, outer pores: '0.006' corrected from '0.06'. + +Ib., Heliosoma indicum, outer pores: '0.004 to 0.01' corrected from '0.004 +to 0.1' (cf. "twice to five times as broad as the bars"). + +Page 253, Actinomma japonicum, middle: '0.1' corrected from '0.01'. + +Page 260, Pityomma piniferum, middle: '0.05' corrected from '0.5'; inner +'0.025' from '0.25'. + +Ib., Pityomma drymodes, middle: '0.1' corrected from '0.01'. + +Page 261, Cromyomma perplexum, diameter (B): '0.13' corrected from '0.013'. + +Page 271, Spongiomma spathillatum: 'Octodendron' corrected from +'Octodendrom'. + +Page 291, Cenellipsis ehrenbergii, shorter axis: '0.08 to 0.1' corrected +from '0.8 to 0.1'. + +Page 307, synopsis, 141: 'Cromyatractus' corrected from 'Cromyotractus'. + +Page 308, Druppula cocos, medullary shell: '0.03 and 0.035' corrected from +'0.03 and 0.35'. + +Page 309, Druppula phoenix, minor axis: '0.08' corrected from '0.8'. + +Page 310, Druppula elliptica: 'irregularly' corrected from 'irreguarlly'. + +Page 314, Prunulum triplex, minor axis: '0.065' corrected from '0.65'. + +Page 324, Druppatractus hippocampus: 'Druppatractus' corrected from +'Druppactractus'. + +Page 372, Cyphinidium apicatum, pores: '0.005 to 0.01' corrected from +'0.005 to 0.001'. + +Page 380, Panartus fusiformis, breadth: '0.08 to 0.1' corrected from '0.08 +to 0.01'. + +Ib., Panartus profundissimus, pores: '0.015' corrected from '0.15' (cf. +"six to eight times as broad as the bars"). + +Page 405, ref. to Saturnalis: 'Pl. 13, fig. 16' corrected from 'fig. 6'. + +Page 418, Trochodiscus solaris: reference to 'Heliodiscus solaster' +corrected from 'solaris' per main text entry. + +Page 468, Coccocyclia heliantha: 'Coccocyclia' corrected from 'Coccocylia'. + +Page 469, Diplactura: reference to 'Spongolena' corrected from +'Spongolene'. + +Page 485, synopsis, 236: 'Tessarastrum' corrected from 'Tesserastrum'. + +Page 508, Staurodictya ocellata: 'Stylodictya' corrected from 'Stylodicta'. + +Page 513, Stylodictya dujardinii: 'Stylodictya' corrected from +'Stylodicyta'. + +Page 538: 'Chitonastrum dicranoides' corrected from 'Chitonastrum +dicranodes' (per Index). + +Page 544, Hagiastrum christi: 'Tessarastrum' corrected from 'Tesserastrum'. + +Page 548, subgenus 2: 'Tessarastromma' corrected from 'Tessarostromma'. + +Page 557, Pentinastrum, definition: 'Histiastrum' corrected from +'Histriastrum'. + +Page 561, last paragraph: 'Archidiscus hexoniscus' corrected from +'Archidiscus hexonicus'. + +Page 564, Triolena trispinosa, diameter: '0.55' corrected from '0.55'. + +Page 577, Spongodiscus favus, outer meshes: '0.008 to 0.012' corrected from +'0.08 to 0.012'. + +Page 580, Spongolonche conostyla refers to Pl. 48, fig. 7 which does not +show this species. + +Page 593, Dictyocoryne trigona: (basal) 'breadth' corrected from 'breath'. + +Page 606, first paragraph: 'Actilarcus' corrected from 'Actolarcus'. + +Page 606, Cenolarcus: 'Actilarcus' corrected from 'Actolarcus'. + +Page 608, Larcarium amphistylum, breadth: '0.12' corrected from '0.012'. + +Page 612, Larcidium polyacanthum, medullary shell: '0.03 to 0.09' corrected +from '0.3 to 0.09'. + +Page 625, Larnacoma quadruplex, breadth (A): '0.016' corrected from '0.16'. + +Ib., Larnacoma hexagonium: 'inner cortical and outer medullary' corrected +from 'outer cortical and inner medullary'. + +Page 632, synopsis: 'Amphipylonium' corrected from 'Amhipylonium'. + +Page 654, Octopyle decastyle, breadth: '0.032' corrected from '0.32'. + +Page 657, Amphipylonium spinosissimum, length of the inner cortical shell: +'0.16' corrected from '0.016'. + +Page 657, Amphipylonium tetraceros: 'breadth' corrected from 'breath'. + +Page 660, Tholonida: (we distinguish in this) 'family' corrected from +'subfamily'. + +Page 665, Tholodes, definition: 'Tholartus' corrected from 'Thalartus'. + +Page 666, Amphitholus: 'lentelliptical' corrected from 'lentelleptical'. So +also p. 666, Amphitholonium octostylium. + +Page 677, pores: '0.004 to 0.008' corrected from '0.04 to 0.008', cf. "once +to three times as broad as the bars". + +Page 709, Phorticium pylonium, breadth: '0.045' corrected from '0.45'. + +Page 742: 'Acanthometron elasticum' corrected from 'Acathometron'. + +Page 748, Zygacantha semicompressa, habitat (author): 'Car' corrected from +'Czar'. + +Page 765, Phatnacantha: 'Tessaraspida', 'Tessaraspis' corrected from +'Tesseraspida', 'Tesseraspis'. + +Page 786, Amphilonche messanensis, length of the minor spines: '0.05 to +0.09' corrected from '0.5 to 0.09'. + +Page 826, Coscinaspis rhacopora, diameter: '0.15' corrected from '1.15'. + +Page 827, Coscinaspis orthopora: 'Phatnaspis lacunaria' corrected from +'Phatnaspis lacumaria'. + +Page 834, Dodecaspis tricinata, diameter: '0.016' corrected from '0.16'. + +Page 844, Icosaspis elegans, smaller pores: '0.001 to 0.003' corrected from +'0.01 to 0.003'. + +Page 852, Phractopelta: 'apophyses' corrected from 'aphophyses'. + +Page 867, Coleaspis occulta: 'Coleaspis' corrected from 'Coleapsis'. + + + +***END OF THE PROJECT GUTENBERG EBOOK REPORT ON THE RADIOLARIA COLLECTED +BY H.M.S. 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