diff options
Diffstat (limited to '41695-h')
| -rw-r--r-- | 41695-h/41695-h.htm | 1574 |
1 files changed, 579 insertions, 995 deletions
diff --git a/41695-h/41695-h.htm b/41695-h/41695-h.htm index aab3ea3..3906927 100644 --- a/41695-h/41695-h.htm +++ b/41695-h/41695-h.htm @@ -2,7 +2,7 @@ "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"> <head> - <meta http-equiv="Content-Type" content="text/html;charset=iso-8859-1" /> + <meta http-equiv="Content-Type" content="text/html;charset=UTF-8" /> <meta http-equiv="Content-Style-Type" content="text/css" /> <title> The Project Gutenberg eBook of The Appendages, Anatomy, and Relationships @@ -94,47 +94,7 @@ a:active {text-decoration:none;} </style> </head> <body> - - -<pre> - -The Project Gutenberg EBook of The Appendages, Anatomy, and Relationships -of Trilobites, by Percy Edward Raymond - -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: The Appendages, Anatomy, and Relationships of Trilobites - -Author: Percy Edward Raymond - -Release Date: December 24, 2012 [EBook #41695] - -Language: English - -Character set encoding: ISO-8859-1 - -*** START OF THIS PROJECT GUTENBERG EBOOK TRILOBITES *** - - - - -Produced by Thomas Cosmas. Produced from files made -available on The Internet Archive. - - - - - - -</pre> - - - - +<div>*** START OF THE PROJECT GUTENBERG EBOOK 41695 ***</div> <div class="fig_center" style="width: 429px;"> <a name="cover" id="cover"></a> @@ -144,7 +104,7 @@ available on The Internet Archive. <div class="trans_notes"> <p class="caption2">Transcriber's Note</p> -<p>Many figure captions contain size references (i.e., × 6) these should be taken as +<p>Many figure captions contain size references (i.e., × 6) these should be taken as an approximate guideline as the displayed images most likely will not match the size of the originally printed versions due to a number of factors (monitor resolution, chosen display size in browser, etc.).</p> @@ -232,8 +192,8 @@ OF TRILOBITES;</p> <p>Trilobites are among the most interesting of invertebrate fossils and have long attracted the attention of amateur collectors and men of science. These "three-lobed minerals" have been mentioned or described in books at least since 1698 and now several thousand species -are known to palæontologists. To this group of students they are the most characteristic -animals of the seas of Palæozoic time, and even though they are usually preserved as dismembered +are known to palæontologists. To this group of students they are the most characteristic +animals of the seas of Palæozoic time, and even though they are usually preserved as dismembered parts, thousands upon thousands of "whole ones" are stored in the museums of the world. By "whole ones" perfect individuals are not meant, for before they became fossils the wear and tear of their time and the process of decomposition had taken away all @@ -254,7 +214,7 @@ in a chance find in 1884, and for eight years he sought off and on for the strat this specimen came. His long search was finally rewarded by the discovery of the bed, and lo! here were to be had, in golden color, prostrate specimens with the breathing and crawling legs and the long and beautifully curved feeling organs all replaced by iron -pyrites. Fool's gold in this case helped to make a palæontologic paradise. The bed contained +pyrites. Fool's gold in this case helped to make a palæontologic paradise. The bed contained not only such specimens of <i>Triarthrus becki</i>, but also, though more rarely, of <i>Cryptolithus tessellatus</i> and exceptionally of <i>Acidaspis trentonensis</i>. This important discovery, which has figured so largely in unraveling the evolution of the Crustacea and even has a @@ -266,7 +226,7 @@ revealed themselves with all of their information exposed for study. No surgeon needed, but a worker knowing the great scientific value of what was hidden, and with endless patience and marked skill in preparation of fossils. Much could be revealed with the hammer, because specimens were fairly abundant. A chance fracture at times showed considerable -portions, often both antennæ entire, and more rarely the limbs protruding beyond +portions, often both antennæ entire, and more rarely the limbs protruding beyond the test, but the entire detail of any one limb or the variation between the limbs of the head, thorax, and tail was the problem to be solved. No man ever loved a knotty problem more than Charles E. Beecher. Any new puzzle tempted him, and this one of <i>Triarthrus @@ -280,7 +240,7 @@ anatomical significance.</p> pyrites, as has been said, and are buried in a gray-black carbonaceous shale. A little rubbing of the specimens soon makes of them bronze images of the former trilobite and while under preparation they are therefore easily seen. However, as the average individual is -under an inch in length and as all the limbs other than the antennæ are double or biramous, +under an inch in length and as all the limbs other than the antennæ are double or biramous, one lying over the other, and the outer one fringed with a filamentous beard, the parts to be revealed by the preparator are so small and delicate that the final touch often obliterates them. These inherent difficulties in the material were finally overcome by endless trials on @@ -326,7 +286,7 @@ death came to him suddenly, leaving the trilobite problem but partially solved.< <p><span class="pagenum"><a name="Page_7" id="Page_7">[7]</a></span></p> <p>When the writer, in the autumn of 1904, succeeded Professor Beecher in the chair of -Palæontology at Yale, he expected to find considerable manuscript relating to the ventral +Palæontology at Yale, he expected to find considerable manuscript relating to the ventral anatomy of the trilobites, but there was only one page. It was Beecher's method first to prepare and thoroughly study the material in hand, then to make the necessary illustrations, and between times to read what others had written. There was no written output until @@ -427,7 +387,7 @@ of <i>Triarthrus</i> and <i>Cryptolithus</i>. Professor Beecher, while an observ details, believed in publishing only the broader, more general results of his investigations. This method made his papers brief, readable, and striking, but it also resulted in leaving in some minds a certain amount of doubt about the correctness of the observations. In a matter -so important as this, it has seemed that palæontologists are entitled to the fullest possible +so important as this, it has seemed that palæontologists are entitled to the fullest possible knowledge of the specimens on which the conclusions are based. The last part is, therefore, a record of the data for the restorations of <i>Triarthrus</i> and <i>Cryptolithus</i>.</p> @@ -593,7 +553,7 @@ Harvard University, Cambridge, Mass.<br /> <td class="tdr">45</td> </tr> <tr> - <td class="lvl3"><a href="#Ptychoparia_cordillerae_Rominger"><i>Ptychoparia cordilleræ</i> (Rominger</a>)</td> + <td class="lvl3"><a href="#Ptychoparia_cordillerae_Rominger"><i>Ptychoparia cordilleræ</i> (Rominger</a>)</td> <td class="tdr">45</td> </tr> <tr> @@ -628,7 +588,7 @@ Harvard University, Cambridge, Mass.<br /> <td class="tdr">47</td> </tr> <tr> - <td class="lvl3"><a href="#Spiral_Branchiae">Spiral branchiæ</a></td> + <td class="lvl3"><a href="#Spiral_Branchiae">Spiral branchiæ</a></td> <td class="tdr">48</td> </tr> <tr> @@ -831,7 +791,7 @@ Harvard University, Cambridge, Mass.<br /> <td class="tdr">85</td> </tr> <tr> - <td class="lvl4"><a href="#Illaenus"><i>Illænus</i></a></td> + <td class="lvl4"><a href="#Illaenus"><i>Illænus</i></a></td> <td class="tdr">85</td> </tr> <tr> @@ -1033,7 +993,7 @@ Harvard University, Cambridge, Mass.<br /> <td class="tdr">120</td> </tr> <tr> - <td class="lvl3"><a href="#ARANEAE">Araneæ</a></td> + <td class="lvl3"><a href="#ARANEAE">Araneæ</a></td> <td class="tdr">121</td> </tr> <tr> @@ -1310,12 +1270,12 @@ Harvard University, Cambridge, Mass.<br /> </tr> <tr> <td class="tdr"><a href="#fig_25">25</a></td> - <td><i>Cryptolithus tessellatus</i> Green. Cheek showing the genal cæca</td> + <td><i>Cryptolithus tessellatus</i> Green. Cheek showing the genal cæca</td> <td class="tdr">84</td> </tr> <tr> <td class="tdr"><a href="#fig_26">26</a></td> - <td><i>Illænus.</i> Volborth's figure of the heart</td> + <td><i>Illænus.</i> Volborth's figure of the heart</td> <td class="tdr">85</td> </tr> <tr> @@ -1381,7 +1341,7 @@ Harvard University, Cambridge, Mass.<br /> </tr> <tr> <td class="tdr"><a href="#fig_39">39</a></td> - <td><i>Pædeumias robsonensis</i> Burling</td> + <td><i>Pædeumias robsonensis</i> Burling</td> <td class="tdr">145</td> </tr> <tr> @@ -1470,7 +1430,7 @@ escape the suspicion that some of the accepted hypotheses of today, founded on s <p>The history of the study of appendages of trilobites may be divided into two periods. The first, in which there was a general belief that the appendages were soft organs, but -during which numerous "finds" of limbs were reported, extended from the time of Linné +during which numerous "finds" of limbs were reported, extended from the time of Linné to the year (1876) in which Walcott demonstrated the fact that the animals possessed jointed ambulatory and breathing organs.</p> @@ -1484,23 +1444,23 @@ of Eichwald (1825) and Billings (1870), but since neither of these men convinced of the value of his finds, the work of neither can be considered as having marked an especial epoch in the history.</p> -<p>As all the authentic finds will be treated in detail on later pages, only a brief résumé +<p>As all the authentic finds will be treated in detail on later pages, only a brief résumé of the first period will be given here. This has already been done by Burmeister (1843, 1846) and Barrande (1852, 1872), whose works have been my primary sources of information, but I have looked up the original papers, copies of nearly all of which are to be seen in the libraries in Cambridge and Boston. Brig.-Gen. A. W. Vogdes, U. S. A. (retired), has very kindly placed at my disposal a number of references and notes.</p> -<p>Linné (1759) was the first to report the discovery of appendages of trilobites. Törnquist +<p>Linné (1759) was the first to report the discovery of appendages of trilobites. Törnquist (1896) has pressed for a recognition of the contribution of the great Swedish naturalist -to this problem, but Beecher (1896 B) doubted the validity of the find. Linné figured +to this problem, but Beecher (1896 B) doubted the validity of the find. Linné figured a specimen of <i>Parabolina spinulosa</i> (Wahlenberg), with what he interpreted as a pair of -antennæ attached. He states (translation quoted from Törnquist): "Most remarkable in -this specimen are the antennæ in the front, which I never saw in any other sample, and +antennæ attached. He states (translation quoted from Törnquist): "Most remarkable in +this specimen are the antennæ in the front, which I never saw in any other sample, and which clearly prove this fossil to belong to the insects." Beecher has shown as conclusively -as can be shown without access to the original specimen that the supposed antennæ were +as can be shown without access to the original specimen that the supposed antennæ were really only portions of the thickened anterior border, the appearance being due to imperfect -preservation. Brünnich as early as 1781 called attention to the imperfection of this specimen, +preservation. Brünnich as early as 1781 called attention to the imperfection of this specimen, <span class="pagenum"><a name="Page_18" id="Page_18">[18]</a></span> and it is also referred to by Wahlenberg (1821, p. 39), Brongniart (1822, p. 42), Dalman (1828, p. 73), and Angelin (1854, p. 46).</p> @@ -1518,12 +1478,12 @@ was also the first to describe an hypostoma of a trilobite (p. 37, pl. 1, fig. 6 did not understand the nature of his specimen, which he described as a distinct species.</p> <p>Brongniart (1822, p. 40) devoted five pages of his monograph to a discussion of the -affinities of trilobites, concluding that it was very probable that the animals lacked antennæ +affinities of trilobites, concluding that it was very probable that the animals lacked antennæ and feet, unless it might be that they had short soft feet which would allow them to creep about and fix themselves to other bodies.</p> <p>Schlotheim (1823) thought that the spines on <i>Agnostus pisiformis</i> were segmented -and compared them with the antennæ of <i>Acarus</i>.</p> +and compared them with the antennæ of <i>Acarus</i>.</p> <p>Stokes (1823) was the first who, with understanding, published an illustration of the ventral side of a trilobite, having figured the hypostoma of an <i>Isotelus</i>. He was followed @@ -1594,8 +1554,8 @@ projecting shell lobe, bearing a bladder-shaped gill on the inner side (1846, p. <p>McCoy (1846) observed in several trilobites a pair of pores situated in the dorsal furrows near the anterior end of the glabella. He showed that the pits occupy precisely the -position of the antennæ of insects and suggested that they indicated the former presence -of antennæ in these trilobites (chiefly <i>Anipyx</i> and "<i>Trinucleus</i>"). The evidence from <i>Cryptolithus</i>, +position of the antennæ of insects and suggested that they indicated the former presence +of antennæ in these trilobites (chiefly <i>Anipyx</i> and "<i>Trinucleus</i>"). The evidence from <i>Cryptolithus</i>, set forth on a later page, indicates the correctness of McCoy's view.</p> <p>Richter (1848, p. 20, pl. 2, fig. 32) described and figured what he took to be a phyllopod-like @@ -1603,8 +1563,8 @@ appendage found in a section through a <i>Phacops</i>. Without the specimen it i impossible to say just what the structure really was. The outline figure is so obviously modeled on an appendage of <i>Apus</i> that one is inclined to think it somewhat diagrammatic. In calling attention to this neglected "find," Clarke (1888, p. 254, fig.) interprets the -appendage as similar to the spiral branchiæ of <i>Calymene senaria</i>, and adds that he himself -has seen evidence of spiral branchiæ in the American Phacops rana.</p> +appendage as similar to the spiral branchiæ of <i>Calymene senaria</i>, and adds that he himself +has seen evidence of spiral branchiæ in the American Phacops rana.</p> <p>Beyrich (1846) described a cast of the intestine of "<i>Trinucleus</i>," and Barrande (1852) further elaborated on this discovery.</p> @@ -1616,7 +1576,7 @@ further elaborated on this discovery.</p> to describe the appendages of trilobites, concluding that none showed any evidence of other than soft appendages, until Billings' discovery of 1870.</p> -<p>Volborth (1863) described a long chambered tubular organ in <i>Illænus</i> which he believed +<p>Volborth (1863) described a long chambered tubular organ in <i>Illænus</i> which he believed to represent a cast of the heart of a trilobite, but which has since been likened by writers to the intestinal tract in "<i>Trinucleus</i>."</p> @@ -1678,7 +1638,7 @@ articulations between them, <i>joints</i>. Such a procedure is unusual, but prom <p>The first mention of <i>Neolenus</i> with appendages preserved was in Doctor Walcott's paper of 1911, in which two figures were given to show the form of the exopodites in comparison -with the branchiæ of the eurypterid-like <i>Sidneyia</i>. In 1912, two more figures were +with the branchiæ of the eurypterid-like <i>Sidneyia</i>. In 1912, two more figures were presented, showing the antennules, exopodites, and cerci. The specimens were found in the Burgess shale (Middle Cambrian) near Field, in British Columbia. This shale is exceedingly fine-grained, and has yielded a very large fauna of beautifully preserved fossils, either @@ -1753,7 +1713,7 @@ those of any other trilobite whose appendages were previously known. As shown in photographs (pl. 20, fig. 2; pl. 22), each exopodite consists of a single long, broad, leaf-like blade, not with many segments as in <i>Triarthrus</i>, but consisting of a large basal and small terminal lobe. It bears on its outer margin numerous relatively short, slender, flat -setæ. The long axes of the exopodites point forward, and the setæ are directed forward +setæ. The long axes of the exopodites point forward, and the setæ are directed forward and outward. They stand more nearly at right angles to the shaft on the cephalic exopodites than on those of the thorax. This same type of broad-bladed exopodite is also found on the thorax and pygidium.</p> @@ -1789,10 +1749,10 @@ sides must have almost met on the median line. The segments of the endopodites a but little, if any, longer than broad, and at the distal end each shows two or more spines. The propodite and dactylopodite are notably more slender than the others. The exopodites of the thorax are broad and flat, and each shaft has two distinct parts with different kinds -of setæ. The posterior edge of the proximal lobe is fringed with a slender, flat, overlapping +of setæ. The posterior edge of the proximal lobe is fringed with a slender, flat, overlapping hairs which are a little longer than the width of the lobe, and stand at an angle of about 60 degrees with the direction of the axis of the appendage. The outer lobe is at an angle -with the main one, and has short, very fine setæ oh the margin. One or two specimens show +with the main one, and has short, very fine setæ oh the margin. One or two specimens show some evidence of a joint between the inner and outer lobes, but in the great majority of cases they seem to be continuous; if originally in two segments, they have become firmly united. The exopodites of the thorax, like those of the cephalon, are directed diagonally @@ -1837,7 +1797,7 @@ with his, I have thought it fairer to the reader to present here rather full not explaining the position I have taken. I understand that since I communicated my interpretation of the epipodites and exites to him, Doctor Walcott has submitted the specimens to <span class="pagenum"><a name="Page_24" id="Page_24">[24]</a></span> -several palæontologists, who consider that epipodites are really present. Since I am not able +several palæontologists, who consider that epipodites are really present. Since I am not able to convince myself that their conclusion is based upon sound evidence, I give here my own interpretation. There is of course, no a priori reason why trilobites should not have had epipodites.</p> @@ -1863,7 +1823,7 @@ ridges and grooves of the thorax.</p> <img src="images/fig_2.png" width="347" height="159" alt="" title="" /> <p class="fig_caption"><span class="smcap">Fig. 2.</span> <i>Neolenus serratus</i> (Rominger). A sketch of the coxopodites and endopodites of two thoracic segments. Note notch for the reception -of the lower end of the appendifer. × 3.</p> +of the lower end of the appendifer. × 3.</p> </div> <p>The coxopodite of the appendage of the last thoracic segment is best preserved. It is @@ -1911,7 +1871,7 @@ side have extremely fine, faintly visible spines on the anterior side. The speci fragments of a few exopodites, but nothing worth describing. In the middle of the right pleural lobe there is a small organ which Walcott has interpreted as a small epipodite. It is oval in form, broken at the end toward the axial lobe, and has exceedingly minute short -setæ on the posterior margin. From analogy with other specimens, it appears to me to be +setæ on the posterior margin. From analogy with other specimens, it appears to me to be the outer end of an exopodite.</p> <p><i>Measurements:</i> The entire specimen is about 64 mm. long and 52 mm. wide at the @@ -2012,7 +1972,7 @@ which follows a smooth curve, while in the curve on the posterior side, which is backward, there is a re-entrant, setting off a small outer lobe whose length is about one third the length of the whole. This lobe seems to be a continuation of the shaft, and the test of the whole is wrinkled and evidently very thin. The main and distal lobes of the -shaft both bear numerous delicate setæ, but those of the outer lobe are much shorter and +shaft both bear numerous delicate setæ, but those of the outer lobe are much shorter and finer than those on the main portion. The latter are flattened and blade-like.</p> <table summary="Figs. 3-4"> @@ -2024,16 +1984,16 @@ finer than those on the main portion. The latter are flattened and blade-like.</ </tr> <tr> <td class="vtop" style="padding:0 12px; width:150px;"><p class="fig_caption"><span class="smcap">Fig. 3.</span> Exopodite of <i>Neolenus serratus</i> (Rominger), to show - form of the lobes of the shaft, and the setæ. × 4.</p> + form of the lobes of the shaft, and the setæ. × 4.</p> </td> <td class="vtop" style="padding:0 12px; width: 250px;"><p class="fig_caption"><span class="smcap">Fig. 4.</span> <i>Neolenus serratus</i> (Rominger). One of the so-called epipodites of specimen 65515, showing that it has the same outline as an exopodite - (compare <a href="#fig_3">figure 3</a>) and fragments of setæ on the margin. × 3.</p> + (compare <a href="#fig_3">figure 3</a>) and fragments of setæ on the margin. × 3.</p> </td> </tr> </table> -<p>The anterior edge of the shaft shows a narrow stiffening ridge and the setæ are but little +<p>The anterior edge of the shaft shows a narrow stiffening ridge and the setæ are but little longer than its greatest width. The second segment of the pygidium has another exopodite like this one, but shows faintly the line between the two lobes, as though there were two segments.</p> @@ -2051,14 +2011,14 @@ wide at the front. The exopodites show faintly beneath the pygidial shield, but ends are too indistinct to allow accurate measurement. Apparently they were just about long enough to reach to the margin of the shield. The best preserved one, that of the second segment in the pygidium, is about 11 mm. long, 2.5 mm. wide at the widest; -the distal lobe is 2.5 mm. long, and the longest setæ of the main lobe 3.5 mm. long. The +the distal lobe is 2.5 mm. long, and the longest setæ of the main lobe 3.5 mm. long. The pleural lobe of the pygidium is just 11 mm. wide at this point.</p> <p>The endopodites project from 8 to 12 mm. beyond the pygidium, showing about four segments.</p> <p>The thoracic exopodite described above is 11 mm. long and 2.75 mm. wide at the widest -part. The distal lobe is 3.5 mm. long and 2.25 mm. wide, and the longest setæ on the main +part. The distal lobe is 3.5 mm. long and 2.25 mm. wide, and the longest setæ on the main lobe 3 mm. long.</p> @@ -2070,15 +2030,15 @@ Coll., vol. 67, 1918, pl. 21, fig. 6.</p></div> <p>This specimen is somewhat difficult to study but is very valuable as showing the natural position of the exopodites of the anterior part of the thorax. Walcott's figures are excellent and show the broad leaf-like shafts, the distal lobes with the re-entrant angles in the posterior -margin, and the long fine setæ of the main lobes. None of the distal lobes retains its -setæ. All extend back to the dorsal furrows, but the proximal ends are not actually shown.</p> +margin, and the long fine setæ of the main lobes. None of the distal lobes retains its +setæ. All extend back to the dorsal furrows, but the proximal ends are not actually shown.</p> <p>The specimen is especially important because it shows the same distal lobes as specimen No. 65514, and demonstrates that they are a part of the exopodite and not of any other structure.</p> <p><i>Measurements:</i> The exopodite belonging to the fourth thoracic segment is 23 mm. -long and 4 mm. wide at the widest part. The longest setæ are 7 mm. in length.</p> +long and 4 mm. wide at the widest part. The longest setæ are 7 mm. in length.</p> <p class="section">Specimen No. 65520.</p> @@ -2112,7 +2072,7 @@ left of the glabella there are two large exopodites, the anterior of which lies conceals the other. These show by their position that they belong to the fourth and fifth cephalic appendages. In front of these lie two appendages which may be either endopodites or exopodites, but which I am inclined to refer to the latter. Both are narrow and -shaped like endopodites, but bear on their outer edges close-set fine setæ. They also show +shaped like endopodites, but bear on their outer edges close-set fine setæ. They also show what might be considered as faint traces of segmentation. If the first of these ran under the end of the exopodite behind it, as shown in Walcott's figure (pl. 22), then it would be necessary to interpret it as an endopodite, but it really continues down between the exopodite @@ -2129,7 +2089,7 @@ appendages have been moved to the right of their original position. The anterior is very poorly shown, but seems to be articulated in front of the eye. The posterior exopodites are very similar to those on the thorax. The distal lobe is shown only by the second from the last. It has the same form as the distal lobes on the thoracic exopodites, -and like them has much finer setæ than the main lobe, but it does not stand at so great an +and like them has much finer setæ than the main lobe, but it does not stand at so great an angle with the axis of the main lobe, nor yet is it so straight as shown in Walcott's figure.</p> @@ -2148,8 +2108,8 @@ the cephalon was apparently about 15 mm. long when complete.</p> on the left side as viewed from above. On the posterior half there are three large appendages which have the exact form of the exopodites of other specimens. There is a broad, oval, proximal lobe and a distal one at an angle with it. The proximal part of the -shaft has fine setæ or the bases of them, and the distal lobe faint traces of much finer ones. -The form, and the setæ so far as they are preserved, are exactly like those of the exopodites +shaft has fine setæ or the bases of them, and the distal lobe faint traces of much finer ones. +The form, and the setæ so far as they are preserved, are exactly like those of the exopodites on the specimens previously described. (See <a href="#fig_4">fig. 4, page 26</a>.) Beneath them there are slender, poorly preserved endopodites.</p> @@ -2180,10 +2140,10 @@ belong together, can easily be explained.</p> </tr> <tr> <td class="vtop" style="padding:0 12px; width: 175px;"><p class="fig_caption"><span class="smcap">Fig. 5.</span>—A sketch of the so-called exites of <i>Neolenus serratus</i> - (Rominger), to show the form and the character of the spines. × 2.</p> + (Rominger), to show the form and the character of the spines. × 2.</p> </td> <td class="vtop" style="padding:0 12px; width: 175px;"><p class="fig_caption"><span class="smcap">Fig. 6.</span>—Endopodite of a cephalic appendage of <i>Neolenus serratus</i> - (Rominger), showing the very broad coxopodite. × 2.</p> + (Rominger), showing the very broad coxopodite. × 2.</p> </td> </tr> </table> @@ -2191,7 +2151,7 @@ belong together, can easily be explained.</p> <p>Before calling these structures new organs not previously seen on trilobites, it is of course necessary to inquire if they can be interpreted as representing any known structures. That they can not be exopodites is obvious, since they are bordered by short stout spines -instead of setæ. The same stout spines that negate the above possible explanation at once +instead of setæ. The same stout spines that negate the above possible explanation at once suggest that they are coxopodites (compare <a href="#fig_6">fig 6</a>). At first sight, the so-called exites seem too wide and too rounded to be so interpreted, but if reference be had to the specimens rather than the figures, it will be noted that the only well preserved structure (No. 2) is @@ -2296,7 +2256,7 @@ outer portion of the large posterior appendage (maxilla) of the head.</p> <p>Thorax. Traces of several slender-jointed thoracic legs project from beneath the anterior segments and back of these on the right side more or less of six legs have been pushed out from beneath the dorsal shield; these are composed of three or four long slender joints; fragments of the three proximal joints indicate that -they are shorter and larger and that they have a fringe of fine setæ. Indications of a branchial lobe (gill) are +they are shorter and larger and that they have a fringe of fine setæ. Indications of a branchial lobe (gill) are seen in two specimens where the legs are not preserved. This is often the case both among the Merostomata (pl. 29, fig. 3, <i>Molaria</i>) and Trilobita (pl. 24, fig. 2, <i>Ptychoparia</i>).</p> @@ -2330,7 +2290,7 @@ in the appendages, but thought each showed at least four or five.</p> fig, 1) reviewed the collection from the American Trenton in the British Museum and found a specimen in the "Black Trenton limestone," from Ottawa, Ontario, in which, alongside the hypostoma, was a jointed appendage, which he described as the "jointed palpus of -one of the maxillæ." This has always been considered an authentic "find," but I am informed +one of the maxillæ." This has always been considered an authentic "find," but I am informed by Doctor Bather that the specimen does not show any real appendage. For further discussion, see under <i>Isotelus gigas</i>.</p> @@ -2411,7 +2371,7 @@ segments of the appendages of <i>Isotelus</i> is due to post-mortem changes.</p> <p class="center">(<a href="#Plate_10">pl. 10, fig. 1.</a>)</p> <div class="blockquot"><p>Illustrated: <i>Asaphus platycephalus</i> Billings, Quart. Jour. Geol. Soc., London, vol. 26, 1870, pl. 31, figs. 1-3; -pl. 32, figs. 1, 2.—Woodward, Geol. Mag., vol. 8, 1871, pl. 8, figs. 1, 1a.—Gerstäcker, in Bronn's "Klassen u. +pl. 32, figs. 1, 2.—Woodward, Geol. Mag., vol. 8, 1871, pl. 8, figs. 1, 1a.—Gerstäcker, in Bronn's "Klassen u. Ordnungen d. Thier-Reichs," 1879, pl. 49, fig. 1.—von Koenen, N. Jahrb. f. Min., etc., vol. 1, 1880, pl. 8, fig. 8.—Milne-Edwards, Ann. Sci. Nat., Zoologie, ser. 6, vol. 12, 1881, pl. 12, fig. 45.</p> @@ -2489,7 +2449,7 @@ longest exopodite which can be traced, about 20 mm.</p> <div class="blockquot"><p>Illustrated: Mickleborough, Jour. Cincinnati Soc. Nat. Hist., vol. 6, 1883, p. 200, figs. 1-3 (endopodites and coxopodites). Walcott, Science, vol. 3, 1884, p. 279, fig. 1 (endopodites, coxopodites, and traces of exopodites). Woodward, Geol. Mag., dec. 3, vol. 1, 1884, p. 162, figs. 1-3 (copies of Mickleborough's -figures). Bernard, The Apodidæ, 1892, text fig. 49. Beecher, Amer. Jour. Sci., vol. 13, 1902, p. 169, pl. 5. +figures). Bernard, The Apodidæ, 1892, text fig. 49. Beecher, Amer. Jour. Sci., vol. 13, 1902, p. 169, pl. 5. figs. 5, 6 (outline from one of Mickleborough's figures and an original figure). Walcott, Smithson. Misc. Coll., vol. 67, 1918, p. 133, pl. 24, figs. 3, 3a; pl. 25, fig. 1.</p></div> @@ -2555,7 +2515,7 @@ in a graceful curve.</p> <p>Walcott's figure in Science shows hair-like markings on the under side of the right half of the thorax. These were interpreted by both Walcott and Beecher as fringes of the -exopodites, but since the setæ of those organs on all other trilobites are always above the +exopodites, but since the setæ of those organs on all other trilobites are always above the endopodites, while these are represented as below them, it would seem doubtful if this interpretation can be sustained. Furthermore, I find no trace of them on either cast or mould, and the actual specimen does not now show them.</p> @@ -2635,7 +2595,7 @@ which has been much eroded on its upper surface, leaving the hypostoma and what belonging to the first, second, and third somites, exposed to view, united along the median line by a longitudinal ridge. The pseudo-appendages, however, have no evidence of any articulations. But what appears to me to be of the highest importance, as a piece of additional information afforded by the Museum specimen, is -the discovery of what I believe to be the <i>jointed palpus</i> of one of the maxillæ, which has left its impression +the discovery of what I believe to be the <i>jointed palpus</i> of one of the maxillæ, which has left its impression upon the side of the hypostoma—just, in fact, in that position which it must have occupied in life, judging by other Crustaceans which are furnished with an hypostoma, as <i>Apus</i>, <i>Serolis</i>, etc.</p> @@ -2667,7 +2627,7 @@ Bather some years ago when selecting fossils to be placed on exhibition:</p> <p>This specimen is in the Brit. Mus. Geol. Dept. I 14431. The supposed hypostome is exceedingly doubtful; it lies dorsad of the crushed glabellar skeleton. The "appendage" is merely the edge of a part in the -head-shield; the maxilla is some calcite filling, between two such laminæ.</p> +head-shield; the maxilla is some calcite filling, between two such laminæ.</p> <div style="width:100%"> <span class="ind3em">13 Sept. 1911.</span> @@ -2734,8 +2694,8 @@ in Evolution, 1901, reprint of all previous figs.;—Amer. Jour. Sci., vol. pl. 4, fig. 1; pl. 5, figs. 2-4;—Geol. Mag., dec. 10, vol. 9, 1902, pls. 9-11, text figs. 1-3.—Walcott, Proc. Biol. Soc. Washington, vol. 9, 1894, pl. 1 figs. 1-6;—Geol. Mag., dec. 4, vol. 1, 1894, pl. 8;—Smithson. Misc. Coll., vol. 67, 1918, pl. 29, figs. 1-11; pl. 30, figs. 17-20; pl. 32; pl. 34, figs. 4-7; pl. 35, fig. 5.—Bernard, Quart. -Jour. Geol. Soc., London, vol. 50, 1894, text figs. 11, 12.—Œhlert, Bull. Soc. Géol. France, ser. 3, vol. 24, 1896, -text figs. 1-17, 34.—Jaekel, Zeits. d. d. geol. Gesell., vol. 53, 1901, text fig. 24. Moberg, Geol. Fören. Förhandl., +Jour. Geol. Soc., London, vol. 50, 1894, text figs. 11, 12.—Œhlert, Bull. Soc. Géol. France, ser. 3, vol. 24, 1896, +text figs. 1-17, 34.—Jaekel, Zeits. d. d. geol. Gesell., vol. 53, 1901, text fig. 24. Moberg, Geol. Fören. Förhandl., vol. 29, pl. 5, 1907, pl. 4, fig. 2; pl. 5, fig. 1.—Handlirsch, Foss. Insekten, 1908, text fig. 6.—Tothill, Amer. Jour. Sci., vol. 42, 1916, p. 380, text fig. 5.—Crampton, Jour. N. Y. Entomol. Soc., vol. 24, 1917, pl. 2, fig. 20.</p></div> @@ -2802,7 +2762,7 @@ from Professor Beecher's, to incorporate the results of his later work. The inner ends of the endobases are probably too far apart, as it was not discovered until after the drawing had been made that the appendifers projected within the dorsal furrows. Drawn by -Doctor Elvira Wood. × about 3.8.</p> +Doctor Elvira Wood. × about 3.8.</p> </div> <p>After 1896, Professor Beecher turned his attention largely to the problem of the classification @@ -2943,7 +2903,7 @@ Both of these specimens are in the Yale University Museum.</p> <a name="fig_11" id="fig_11"></a> <img src="images/fig_11.png" width="180" height="120" alt="" title="" /> <p class="fig_caption"><span class="smcap">Fig. 11.</span>—<i>Triarthrus becki</i> Green. Anal plate of specimen 65525 in the U. -S. National Museum. Drawn by Doctor Wood. × 20.</p> +S. National Museum. Drawn by Doctor Wood. × 20.</p> </div> <p>The anal plate is especially well shown by specimen 65525 in the United States National @@ -2983,7 +2943,7 @@ by the specimen.</p> <p class="section"><a id="Ptychoparia_cordillerae_Rominger"></a> -<b>Ptychoparia cordilleræ</b> (Rominger).</p> +<b>Ptychoparia cordilleræ</b> (Rominger).</p> <div class="blockquot"><p>Illustrated: Walcott, Smithson. Misc. Coll., vol. 57, 1912, p. 192, pl. 24, fig. 2;—Ibid., vol. 67, 1918, pl. 21, figs. 3-5 (corrected figure).</p></div> @@ -2999,7 +2959,7 @@ only imperfect traces of the latter….</p> from the line of the union of the mesosternites and the pleurosternites. At the proximal end they appear to be as wide as the axial lobe of each segment, and to increase in width and slightly overlap each other nearly out to the distal extremity…. They are finely crenulated along both the anterior and dorsal margins, -which indicates the presence of fine setæ.</p></div> +which indicates the presence of fine setæ.</p></div> <p>The specimen is quite imperfectly preserved, but seems to indicate that the exopodite of Ptychoparia had a long, rather narrow unsegmented shaft.</p> @@ -3042,7 +3002,7 @@ the curvature, the same antennule is about 11 mm. long.</p> <p>One specimen figured by Doctor Walcott shows the distal ends of some of the exopodites and endopodites of the right side. He compares the exopodites with those of Neolenus, stating that the shaft consists of two segments, the proximal section being long and -flat, fringed with long setæ, while the distal segment has short fine setæ. The endopodite +flat, fringed with long setæ, while the distal segment has short fine setæ. The endopodite best shown is very slender, and the segments are of uniform width and only slightly longer than wide.</p> @@ -3117,7 +3077,7 @@ in the ventral arch somewhat as the legs of some of the Isopods articulate with membrane. The arches of the ventral membrane in the trilobite … afford a correspondingly firm basis for the attachment of the legs.</p> -<p>Branchial appendages.—The branchiæ have required more time and labor to determine their true structure +<p>Branchial appendages.—The branchiæ have required more time and labor to determine their true structure than any of the appendages yet discovered. They were first regarded as small tubes arranged side by side, like the teeth in a rake; then as setiferous appendages, and finally as elongate ribbon-like spirals and bands attached to the side of the thoracic cavity, the epipodite being a so-called branchial arm. All of these parts @@ -3126,22 +3086,22 @@ various curious forms assumed by the parts when broken up and distorted, it was relations were determined.</p> <p>The respiratory system is formed of two series of appendages, as found beneath the thorax. The first -is a series of branchiæ attached to the basal joints of the legs, and the second, the branchial arms, or epipodites.</p> +is a series of branchiæ attached to the basal joints of the legs, and the second, the branchial arms, or epipodites.</p> -<p>The branchiæ, as found in <i>Calymene</i>, <i>Ceraurus</i>, and <i>Acidaspis</i>, have three forms. In the first they +<p>The branchiæ, as found in <i>Calymene</i>, <i>Ceraurus</i>, and <i>Acidaspis</i>, have three forms. In the first they bifurcate a short distance from the attachment to the basal joint of the leg, and extend outward and downward as two simple, slender tubes, or ribbon-like filaments. In the second form they bifurcate in the same mariner, but the two branches are spirals. These two forms occur in the same individual but, as a rule, the more simple ribbon-like branchia is found in the smaller or younger specimens, and the spiral form in the adult…. The -spiral branchiæ of Ceraurus are usually larger and coarser than those of <i>Calymene</i>.</p> +spiral branchiæ of Ceraurus are usually larger and coarser than those of <i>Calymene</i>.</p> -<p>The third type of the branchiæ [consists of rather long straight ribbons arranged in a digitate manner +<p>The third type of the branchiæ [consists of rather long straight ribbons arranged in a digitate manner on a broad basal joint]. As far as yet known, this is confined to the anterior segments of the thorax.</p> <p>The epipodite or branchial arm was attached to the basal joints of the thoracic legs and formed of two or more joints. This has been called a branchial arm, not that it carried a branchia, but on account of its relation to the respiratory system. It is regarded as an arm or paddle, that, kept in constant motion, produced -a current of water circulating among the branchiæ gathered close beneath the dorsal shell. . . .</p> +a current of water circulating among the branchiæ gathered close beneath the dorsal shell. . . .</p> <p>Of the modification the respiratory apparatus underwent beneath the pygidium, we have no evidence.</p> @@ -3161,7 +3121,7 @@ in other trilobites but otherwise the essential features of the appendages of al <p><span class="pagenum"><a name="Page_48" id="Page_48">[48]</a></span></p> -<p class="center"><a id="Spiral_Branchiae"></a>Spiral Branchiæ.</p> +<p class="center"><a id="Spiral_Branchiae"></a>Spiral Branchiæ.</p> <p>It is now necessary to inquire if the thin sections can not be interpreted on the basis of trilobites with the same organs as <i>Triarthrus</i>. The interpretation of the structures seen @@ -3173,7 +3133,7 @@ dogmatically about what one sees in them.</p> <p>Walcott has summarized his results in his restoration of the appendages of <i>Calymene</i> (1918, pl. 33). The coxopodite supports a slender six-jointed endopodite as in <i>Triarthrus</i>, dorsal to which is a short setiferous epipodite which differs from the exopodite of <i>Triarthrus</i>, -in being less long, unsegmented, and in having shorter setæ. Arising from the same +in being less long, unsegmented, and in having shorter setæ. Arising from the same part of the coxopodite with this epipodite is the bifurcate spiral branchia which has not been seen in this form in other trilobites. The evidence on which the existence of this organ is postulated consists of a series of sections across the thorax, the best of them figured by Walcott @@ -3185,7 +3145,7 @@ be cut, either by chance or design, in such a direction as to show any considera any one appendage. This expectation has proved true in regard to the endopodites, the sections rarely showing more than two or three consecutive segments. Sections like those shown in figures 1 and 2 in plate 2 (1881) seem to be unique. On the other hand, there are -numerous slices showing the so-called spiral branchiæ. They show for the most part as +numerous slices showing the so-called spiral branchiæ. They show for the most part as a succession of rectangular to kidney-shaped spots of clear calcite.<a name="FNanchor_1_4" id="FNanchor_1_4"></a><a href="#Footnote_1_4" class="fnanchor">[1]</a> Usually these clear spots are isolated, not confluent, but in a small number of specimens, perhaps three or four, the spots are connected in such a way as to show a zig-zag band which suggests a spiral. Such @@ -3217,20 +3177,20 @@ repeatedly is highly improbable. Moreover, there is a limit to the diameter of t which may be made from these slender spirals. Most of the spots have one diameter about one half greater than the other, but others are from three to six times as long as wide. These last could obviously be cut only from a very large spiral, and they are therefore -interpreted by Walcott as setæ of epipodites. Yet all gradations are found among the sections, -from the long setæ to the short dots. (See pl. 27, 1918.) In referring to one slice, +interpreted by Walcott as setæ of epipodites. Yet all gradations are found among the sections, +from the long setæ to the short dots. (See pl. 27, 1918.) In referring to one slice, Walcott says (1918, p. 152):</p> -<p>In the latter figure and in figure 13, plate 27, the setæ of several epipodites appear to have been cut across -so as to give the effect of long rows of setæ. The same condition occurs in specimens of <i>Marrella</i> when -the setæ of several exopodites are matted against each other.</p> +<p>In the latter figure and in figure 13, plate 27, the setæ of several epipodites appear to have been cut across +so as to give the effect of long rows of setæ. The same condition occurs in specimens of <i>Marrella</i> when +the setæ of several exopodites are matted against each other.</p> <div class="fig_left" style="width: 166px;"> <a name="fig_12" id="fig_12"></a> <img src="images/fig_12.png" width="166" height="160" alt="" title="" /> <p class="fig_caption"><span class="smcap">Fig. 12.</span>—A slice of <i>Ceraurus pleurexanthemus</i> in which the exopodite happened to be cut in such a way as to show a part of the shaft and some -of the setæ in longitudinal section. Specimen 80. × 4.</p> +of the setæ in longitudinal section. Specimen 80. × 4.</p> </div> <p>This is certainly an apt comparison, and equally true if <i>Neolenus</i>, <i>Triarthrus</i>, or <i>Cryptolithus</i> @@ -3244,16 +3204,16 @@ the same way, that is, more or less parallel to the under surface of the head, o on a plane parallel to a plane which would be tangent to the axial portion of the coiled shell. The sections which show the spirals best are those which are cut by a plane perpendicular to the long axis of the body. If one were to attempt to cut an enrolled <i>Triarthrus</i> in such a -way as to get a section showing the length of the setæ, one would not cut a section perpendicular +way as to get a section showing the length of the setæ, one would not cut a section perpendicular to the axis of the animal, nor, in fact, would he cut one parallel to the ventral plane, but it is obvious that in this latter type of section he would stand a better chance of finding a part of the plane of the exopodite coincident with the plane of his section than in the former. And that seems to be what has happened in these sections of <i>Calymene</i> and <i>Ceraurus</i>. If the exopodites were preserved, transverse sections were bound to cut across -many sets of fringes, and the resultant slice would show transverse sections of the setæ as a +many sets of fringes, and the resultant slice would show transverse sections of the setæ as a series of overlapping spots. A few fortunately located sections in a more nearly horizontal <span class="pagenum"><a name="Page_50" id="Page_50">[50]</a></span> -plane might cut the setæ and occasionally the shaft of one or more exopodites in +plane might cut the setæ and occasionally the shaft of one or more exopodites in the longitudinal plane, and the resulting effect would produce the so-called "epipodites." A careful study has shown that no one of these epipodites is complete, and they do not have the palmate form shown in Walcott's figures.</p> @@ -3264,21 +3224,21 @@ found in other trilobites. These are discussed later in the detailed description slices.</p> <p>If these series of spots are interpreted on the basis of the known structure of <i>Triarthrus</i>, -they are of course a series of sections through the setæ of the exopodites. It will be shown -in Part IV that these setæ are not circular in section, but flattened, in <i>Cryptolithus</i> even +they are of course a series of sections through the setæ of the exopodites. It will be shown +in Part IV that these setæ are not circular in section, but flattened, in <i>Cryptolithus</i> even blade-like, and that they overlap one another. A section across them would give the same general appearance as, for instance, that shown in figures 4, 6, 9, and 10 of Walcott's plate 3 (1881).</p> -<p>When both endopodites and the "spiral branchiæ" are present in the same section -(pl. 1, fig. 4; pl. 2, figs. 1, 2), the "spiral branchiæ" are dorsal to the endopodites, as the -setæ of the exopodites would be expected to be. The specimens which show the clear +<p>When both endopodites and the "spiral branchiæ" are present in the same section +(pl. 1, fig. 4; pl. 2, figs. 1, 2), the "spiral branchiæ" are dorsal to the endopodites, as the +setæ of the exopodites would be expected to be. The specimens which show the clear spots connected, and which suggest a spiral (pl. 3, fig. 5), may seem at first sight to bear evidence against this interpretation, but one has only to think of the effect of cutting a section -along the edge where the setæ are attached to the shaft of the exopodite of <i>Triarthrus</i> +along the edge where the setæ are attached to the shaft of the exopodite of <i>Triarthrus</i> to see that such a zig-zag effect is entirely possible. One would expect to cut just this position only rarely, and, in fact, the zig-zags are seen in only three or four sections. -The bifurcation of the basal segment of the "spiral branchiæ" (pl. 3, fig. 10, 1881) is +The bifurcation of the basal segment of the "spiral branchiæ" (pl. 3, fig. 10, 1881) is probably more apparent than real, if indeed these basal segments have anything to do with the succeeding one.</p> @@ -3348,7 +3308,7 @@ what part is body cavity, and what part is appendifer.</p> <p>Nearly forty years ago Von Koenen (1880, p. 431, pl. 8, figs. 9, 10) described and figured the appendifers of Phacops latifrons. He found them to be calcareous projections on the hinder margin of each segment, converging inward, and about 1.5 mm. long. -He correctly considered them as supports (Stützpunkte) for the feet.</p> +He correctly considered them as supports (Stützpunkte) for the feet.</p> <p>Appendifers are well developed also in Pliomerops, and in well preserved specimens of <i>Calymene senaria</i> from Trenton Falls they are present, but instead of being rod-like @@ -3374,8 +3334,8 @@ Misc. Coll., vol. 67, 1918, pl. 26, figs. 1-7, 9-13; pl. 27, figs. 4, 5 (not 5a) 13, 14, 15 (not <i>Ceraurus</i>); pl. 28, figs. 7, 8; pl. 33, fig. 1 (restoration); pl. 34, fig. 2; pl. 35, fig. 6.—Dames, N. Jahrb. f. Min., etc., vol. 1, 1880, pl. 8, figs. 1-5.—Milne-Edwards, Ann. Sci. Nat., Zoologie, ser. 6, vol. 12, 1881, pl. 11, figs. 19-32; pl. 12, figs. 33-41.—Packard, Amer. Nat., vol. 16, 1882, p. 796, fig. 12.—Bernard, The -Apodidæ, 1892, text figs. 50, 52, 54;—Quart. Jour. Geol. Soc., London, vol. 50, 1894, text figs. 13, 15, 17.—Œhlert, -Bull. Soc. Géol. France, ser. 3, vol. 24, 1896, fig. 12.—Beecher, Amer. Jour. Sci., vol. 13, 1902, pl. +Apodidæ, 1892, text figs. 50, 52, 54;—Quart. Jour. Geol. Soc., London, vol. 50, 1894, text figs. 13, 15, 17.—Œhlert, +Bull. Soc. Géol. France, ser. 3, vol. 24, 1896, fig. 12.—Beecher, Amer. Jour. Sci., vol. 13, 1902, pl. 5, fig. 7.</p> <p>In both of Walcott's accounts (1881, 1918) of the appendages of <i>Calymene</i> and @@ -3441,19 +3401,19 @@ thorax.</p> <tr> <td class="vtop" style="padding:0 10px;"><p class="fig_caption"><span class="smcap">Fig. 13.</span>—Slice through <i>Calymene senaria</i> in the plane of the hypostoma, showing the very slender coxopodites beside that organ, the - spines on the inner end of one of the maxillulæ, and the anterior + spines on the inner end of one of the maxillulæ, and the anterior position of the attachment of all these appendages. From a - photographic enlargement. Specimen 50. × 4.</p> + photographic enlargement. Specimen 50. × 4.</p> </td> <td class="vtop" style="padding:0 10px;"><p class="fig_caption"><span class="smcap">Fig. 14.</span>—Slice through the hypostoma and thorax of <i>Calymene senaria</i> Conrad, showing the small size of the coxopodites nearest the hypostoma. Shell in black, appendages and filling of abdominal cavity - dotted. From a photographic enlargement. Specimen 40. × 3.8.</p> + dotted. From a photographic enlargement. Specimen 40. × 3.8.</p> </td> <td class="vtop" style="padding:0 10px;"><p class="fig_caption"><span class="smcap">Fig. 15.</span>—Transverse section of <i>Calymene</i>, showing method of articulation with the appendifer. The shell is in solid black, the filling of the appendage and appendifer stippled. Traced from a - photographic enlargement of the slice. Specimen 63. × 7.</p> + photographic enlargement of the slice. Specimen 63. × 7.</p> </td> </tr> </table> @@ -3497,26 +3457,26 @@ segment.</p> <p>The exopodites of course furnish the chief difficulty in interpretation. Doctor Walcott finds two sets of structures attached to the coxopodite, a long, slender, spiral exopodite, -and a short, broad epipodite with a fringe of long setæ. Since he has given the same +and a short, broad epipodite with a fringe of long setæ. Since he has given the same interpretation for <i>Calymene</i>, <i>Ceraurus</i>, and <i>Acidaspis</i>, I have considered the question of all three together on a preceding page (p. 48), and given my reasons for regarding both structures as due to sections in different directions across setiferous exopodites.</p> <p>Sections like those shown in figures 11, 13, and 14 of plate 27 (1918) happen to be cut -in or near the plane of the setæ of an exopodite, and so show hairs of considerable length. +in or near the plane of the setæ of an exopodite, and so show hairs of considerable length. Such sections are, as would be expected, very few in number, while sections like those shown -on figures 4, 5, 7, and 9 of plate 27, which cut the setæ more nearly at right angles, are +on figures 4, 5, 7, and 9 of plate 27, which cut the setæ more nearly at right angles, are very common. Slices which give any definite idea of the form of the shaft of the exopodite are exceedingly rare. Perhaps the most satisfactory one is No. 23 (pl. 3, fig. 3, 1881), which shows the proximal part of a long, slender, unsegmented shaft, with the bases of a -number of slender setæ. The organ is not complete, as would be inferred from the published +number of slender setæ. The organ is not complete, as would be inferred from the published figure, but the section cuts diagonally across it, and the total length is unknown. It is directed forward, like the exopodites of Neolenus, but whether or not this is a natural position is yet to be learned.</p> <p>The proximal, non-setiferous portion of the exopodite is evidently at an angle with the setiferous part. Another similar exopodite is apparently shown by specimen 29 (pl. 3, -fig. 9, 1881), which has a similar angulated shaft and just a trace of the bases of the setæ.</p> +fig. 9, 1881), which has a similar angulated shaft and just a trace of the bases of the setæ.</p> <p class="section"><a id="Pygidial_Appendages_54"></a><i>Pygidial Appendages.</i></p> @@ -3577,7 +3537,7 @@ ones and more like those on the thorax.</p> tapered inward. The endopodites were slender, tapering gradually outward, and probably did not extend beyond the dorsal test. Small spines were present on the distal end of each segment. Each exopodite had a long, slender, unsegmented shaft, to which were attached -numerous long, overlapping, flattened setæ. The shaft may have been angulated +numerous long, overlapping, flattened setæ. The shaft may have been angulated near the proximal end, and may have been directed somewhat forward and outward as in Neolenus, but the evidence on this point is unsatisfactory. The number of pairs of appendages is that determined by Walcott from longitudinal sections, namely, four pairs on @@ -3666,7 +3626,7 @@ State Mus. Nat. Hist, 1879, pl. 1, fig. 3;—Bull. Mus. Comp. Zool., Harvard <span class="pagenum"><a name="Page_58" id="Page_58">[58]</a></span> 1918, pl. 26, figs. 8, 14, 15; pl. 27, figs. 1-3, 5a, 6-9, 12 (not <i>Calymene</i>), (not 15, <i>Calymene</i>); pl. 28, figs. 1-5; pl. 34, fig. 1; pl. 35, fig. 7.—Milne-Edwards, Ann. Sci. Nat., Zoologie, ser. 6, vol. 12, 1881, pl. 10, figs. 1-18.—Bernard, -The Apodidæ, 1892, text figs. 46, 51.</p></div> +The Apodidæ, 1892, text figs. 46, 51.</p></div> <p class="section"><a id="Cephalic_Appendages_58"></a><i>Cephalic Appendages.</i></p> @@ -3690,7 +3650,7 @@ pair was stronger than the second, and the fourth probably like the third.</p> <img src="images/fig_17.png" width="216" height="106" alt="" title="" /> <p class="fig_caption"><span class="smcap">Fig. 17.</span> Transverse section of <i>Ceraurus pleurexanthemus</i>, showing the relation of the coxopodite to the appendifer. Traced from a photographic -enlargement of the slice. Specimen 128. × 4/5.</p> +enlargement of the slice. Specimen 128. × 4/5.</p> </div> <div class="fig_right" style="width: 180px;"> @@ -3698,15 +3658,15 @@ enlargement of the slice. Specimen 128. × 4/5.</p> <img src="images/fig_18.png" width="180" height="126" alt="" title="" /> <p class="fig_caption"><span class="smcap">Fig. 18.</span> Slice of <i>Ceraurus pleurexanthemus</i>, showing a nearly continuous section of an endopodite and an exopodite above it. The latter is so cut -as to show only the edge of the shaft and the bases of a few setæ. -Traced from a photographic enlargement. Specimen in. × 4.</p> +as to show only the edge of the shaft and the bases of a few setæ. +Traced from a photographic enlargement. Specimen in. × 4.</p> </div> <p>Specimen 92 shows traces of the slender endopodites belonging to the cephalon, but no details. Specimen 22 shows on one side exopodites (epipodites of Walcott) belonging to the third and fourth cephalic appendages. That belonging to the third shows some long -setæ and a trace of the shaft, while the one on the fourth appendage (third coxopodite) has -a portion of a broad shaft and a number of long setæ. It should again be remembered +setæ and a trace of the shaft, while the one on the fourth appendage (third coxopodite) has +a portion of a broad shaft and a number of long setæ. It should again be remembered that the slice does not cut through the plane of the exopodite, but across it at a low angle, so that a part but not all of the shaft is shown. On the other side of this slice there is a fairly good section of one of the thoracic exopodites. It is, however, turned around in @@ -3745,11 +3705,11 @@ probably a terminal spine present, though it is neither so long nor so plainly v Walcott's photograph.</p> <p>The exopodite on this same specimen was evidently cut diagonally across near the setiferous -edge, showing a section through the shaft and the bases of seven setæ (<a href="#fig_18">fig. 18</a>). This +edge, showing a section through the shaft and the bases of seven setæ (<a href="#fig_18">fig. 18</a>). This section is so exactly what would be obtained by cutting similarly an exopodite of either Neolenus or <i>Triarthrus</i> that it should in itself dispose of the "spiral-exopodite" theory.</p> -<p>Several sections have already been illustrated showing sections across the setæ of the +<p>Several sections have already been illustrated showing sections across the setæ of the exopodites (pl. 3, figs. 4-6, 1881; pl. 27, figs. 3, 4, 9, 1918), and similar sections are not uncommon. Only a very few, however, show sections in the plane of the exopodite. If only No. 111, described above, were known, it would be inferred that the exopodite had a @@ -3822,9 +3782,9 @@ apparently somewhat shorter. Each endopodite consisted of six short, fairly stou each with at least two spines on the somewhat expanded distal ends. The exact <span class="pagenum"><a name="Page_61" id="Page_61">[61]</a></span> form of the exopodites could not be made out. The shaft was apparently rather short, unsegmented, -and fairly broad. The setæ appear from the sections to have been more or less +and fairly broad. The setæ appear from the sections to have been more or less blade-shaped and to have overlapped, as do those of the exopodites of <i>Cryptolithus</i>. Judging -from their position in the sections, the setæ not only bordered the posterior side of the +from their position in the sections, the setæ not only bordered the posterior side of the shaft, but radiated out from the end as well.</p> <p>The pygidium shows three pairs of functional appendifers, hence three pairs of appendages @@ -3855,7 +3815,7 @@ are no traces of antennules nor, unfortunately, of exopodites.</p> <p><i>Measurements:</i> Length 8 mm.</p> <p>Walcott (1881, p. 206) stated that his sections had shown the presence in this species -of legs "both cephalic and thoracic" and also the "spiral branchiæ." His specimens were +of legs "both cephalic and thoracic" and also the "spiral branchiæ." His specimens were from the Trenton at Trenton Falls, New York.</p> @@ -3879,7 +3839,7 @@ he cleaned several more, so that there are now thirteen specimens of <i>Trinucle available for study, though some of these do not show much detail. In his last and unpublished study, Beecher devoted the major part of his attention to this genus, and summarized his findings in the drawings which he himself made of the best individuals (text -figs. <a href="#fig_45">45</a>, <a href="#fig_46">46</a>). Valiant (1901) stated that he had found a <i>Trinucleus</i> with antennæ in the +figs. <a href="#fig_45">45</a>, <a href="#fig_46">46</a>). Valiant (1901) stated that he had found a <i>Trinucleus</i> with antennæ in the Frankfort shale south of Rome, New York. The specimen has not been figured.</p> <p><span class="pagenum"><a name="Page_62" id="Page_62">[62]</a></span></p> @@ -3894,7 +3854,7 @@ the margin of the test; the endopodites are not stretched out at right angles to the first three segments have a forward and outward direction as in <i>Triarthrus</i>, while the last four turn back abruptly so that they are parallel to the axis; the limbs at the anterior end of the thorax are much more powerful than the others; the dactylopodites of the endopodites -show a fringe of setæ instead of three spines as in <i>Triarthrus</i> and <i>Neolenus</i>. All +show a fringe of setæ instead of three spines as in <i>Triarthrus</i> and <i>Neolenus</i>. All these would, as Beecher has already suggested, seem to be adaptations to a burrowing habit of life, the antennules being turned backward and the other appendages kept within the shelter of the dorsal test in order to protect them, and the anterior endopodites enlarged and @@ -3952,7 +3912,7 @@ mouth-parts would be quite in order.</p> <img src="images/fig_20.png" width="487" height="487" alt="" title="" /> <p class="fig_caption">Fig. 20. <i>Cryptolithus tessellatus</i> Green. A restoration of the appendages drawn by Doctor Elvira Wood from the original specimens and from the photographs made by Professor -Beecher. × 9.</p> +Beecher. × 9.</p> </div> <p>The appendages of the thorax and pygidium can fortunately be taken quite directly @@ -4104,21 +4064,21 @@ the exopodites are shorter than the endopodites.</p> <p>The exopodites in <i>Triarthrus</i> consist of a proximal shaft, succeeded by numerous short segments, and ending distally in a long, grooved, somewhat spatula-shaped segment. Along the anterior margin of the shaft there are many small spines. Along the posterior margin -there are numerous flattened setæ, which all lie in one plane and which seem to be more or -less united to one another like the barbs of a feather. The setæ are short, not much longer +there are numerous flattened setæ, which all lie in one plane and which seem to be more or +less united to one another like the barbs of a feather. The setæ are short, not much longer than the width of one of the thoracic segments, and point backward and outward. In <i>Cryptolithus</i> the shaft does not seem to be made up of small segments, and is narrow, with a -decided backward curve. The setæ are considerably longer and much more flattened than +decided backward curve. The setæ are considerably longer and much more flattened than in Triarthrus. In <i>Calymene</i> the state of preservation does not allow a very full knowledge of the exopodites, but they appear to have a slender, unjointed shaft and short and delicate -setæ. The coiled branches of the exopodites as described by Walcott seem to me to be +setæ. The coiled branches of the exopodites as described by Walcott seem to me to be only ordinary Triarthrus-like organs, and this, as I understand from Schuchert, was also the view of Beecher. In <i>Ceraurus</i> the exopodite seems to have been somewhat paddle-shaped, -expanded at the distal end, and to have had rather thick, blade-like setæ.</p> +expanded at the distal end, and to have had rather thick, blade-like setæ.</p> <p>The exopodite of <i>Neolenus</i> is decidedly leaf-like, and reminds one somewhat of the exites <span class="pagenum"><a name="Page_67" id="Page_67">[67]</a></span> -of some of the phyllopods. The shaft is a broad unsegmented blade. The setæ are slender, +of some of the phyllopods. The shaft is a broad unsegmented blade. The setæ are slender, delicate, flattened, and a little longer than the width of the shaft. The exopodites of this genus point forward all along the body. In <i>Kootenia</i> the exopodites are like those of <i>Neolenus</i>, but with a narrower shaft. The exopodites of <i>Ptychoparia</i> appear to be very @@ -4202,7 +4162,7 @@ be expected. Two well developed cirri and two rudimentary ones are present in <i they are also to be found in other phyllopods and some isopods. It is, however, characteristic of the Crustacea as a whole to lack appendages on the anal segment. Caudal cirri (cerci) are much more freely developed in the hexapods than in the Crustacea, particularly -in the more primitive orders, Palæodictyoptera, Apterygota, Archiptera, and Neuroptera. +in the more primitive orders, Palæodictyoptera, Apterygota, Archiptera, and Neuroptera. They are supposed, in this case, to be modified limbs, and therefore not homologous with the bristles on the anal segment of an annelid. Doctor W. M. Wheeler of the Bussey Institution has kindly allowed me to quote the following excerpt from a letter to me, as @@ -4215,7 +4175,7 @@ concerning their being originally ambulatory in function. They are certainly not insects. Embryologically they arise precisely like the legs, and each cercus contains a diverticulum of the mesoblastic somite precisely as is the case with the ambulatory legs and mouth parts.</p></div> -<p>The "pygidial antennæ" seem to be as fully developed in <i>Neolenus</i> as in any of the +<p>The "pygidial antennæ" seem to be as fully developed in <i>Neolenus</i> as in any of the other arthropods, and may suggest a common ancestry of the phyllopods, isopods, and hexapods, in the trilobites. They were doubtless tactile organs, and while the evidence is chiefly negative, it would seem that they proved useless, and were lost early in the phylogeny @@ -4228,17 +4188,17 @@ to them.</p> HOMOLOGY OF THE CEPHALIC APPENDAGES WITH THOSE OF OTHER CRUSTACEA.</p> <p>The head of the typical crustacean bears five pairs of appendages, namely, the antennules, -antennas, mandibles, and first and second maxillæ, or, as they are more properly called, the -maxillulæ and maxillæ.</p> +antennas, mandibles, and first and second maxillæ, or, as they are more properly called, the +maxillulæ and maxillæ.</p> -<p>As Beecher has pointed out, the "antennæ" of the trilobites, on account of their pre-oral +<p>As Beecher has pointed out, the "antennæ" of the trilobites, on account of their pre-oral position and invariably uniramous character, are quite certainly to be correlated with the antennules.</p> <p>The second pair of appendages, the first pair of biramous ones, Beecher homologized -with the antennæ of other crustaceans, and that homology has been generally accepted, +with the antennæ of other crustaceans, and that homology has been generally accepted, though Kingsley (1897) suggested that it was possible that no representatives of the true -antennæ were present.</p> +antennæ were present.</p> <p>In preparing the restorations in the present study, the greatest difficulty has been to adjust the organs about the mouth. In <i>Triarthrus</i>, numerous specimens show that without @@ -4262,10 +4222,10 @@ on the lower surface is the loss of glabellar furrows on the upper surface. The furrows mark lines of infolding of the test to form the appendifers and other rugosities for the attachment of tendons and muscles. It is conceivable that this migration backward of the mouth began very early in the history of the race, and that even before Cambrian times, -the antennæ, probably originally biramous appendages like those on the remainder of the +the antennæ, probably originally biramous appendages like those on the remainder of the body, had dwindled away and become lost. If this is the case, then the first pair of biramous -appendages of <i>Triarthrus</i> would be mandibles, the second pair maxillulæ, and the third -pair maxillæ.</p> +appendages of <i>Triarthrus</i> would be mandibles, the second pair maxillulæ, and the third +pair maxillæ.</p> <p>There remain the last pair of cephalic appendages, and they bring up the whole head problem of the trilobites. Beecher has stated (1897 A, p. 96) his conviction that the head @@ -4279,25 +4239,25 @@ hypostoma and the second by the epistoma and free cheeks.</p> five segments in the glabella of certain trilobites. In his table (p. 165) he has listed the segments with their appendages as follows: 1. Acron, with hypostoma; 2, rostrum (epistoma), with free cheeks; 3, first frontal lobe, with (?) antennules; 4, second frontal lobe, -with antennæ; 5, mandibles; 6, first, or pre-maxillæ; 7, second maxillæ; 8, occipital segment +with antennæ; 5, mandibles; 6, first, or pre-maxillæ; 7, second maxillæ; 8, occipital segment with maxillipeds.</p> -<p>Jaekel refused to believe that the antennæ of trilobites were really entirely simple, and -so homologized them with the antennæ and not the antennules of other Crustacea. In this +<p>Jaekel refused to believe that the antennæ of trilobites were really entirely simple, and +so homologized them with the antennæ and not the antennules of other Crustacea. In this he was obviously incorrect, but it accounts for his homology of the remainder of the cephalic appendages.</p> <p>It is, at present, impossible to demonstrate the actual number of somites in the cephalon of the trilobite, but I believe that Beecher was correct in holding that the glabella was -composed of four segments. There are, it is true, a number of trilobites (Mesonacidæ, Paradoxidæ -Cheiruridæ, etc.) which show distinctly four pairs of glabellar furrows, indicating +composed of four segments. There are, it is true, a number of trilobites (Mesonacidæ, Paradoxidæ +Cheiruridæ, etc.) which show distinctly four pairs of glabellar furrows, indicating five segments in the glabella. This is, however, probably due to a secondary division of the first lobe.</p> <p>The correspondence of the five segments on the dorsal side with the five pairs of appendages makes it unlikely that any pair of limbs has been lost. The condition in <i>Marrella</i>, where a trilobite-like cephalon bears five pairs of appendages, the second pair of which are -tactile antennæ, is favorable to the above interpretation. In spite of the apparent degeneration +tactile antennæ, is favorable to the above interpretation. In spite of the apparent degeneration of the first two pairs of appendages in <i>Calymene</i>, no limbs are actually missing, and if some are dropped out in the later trilobites it would not affect the homology of those now known. I therefore agree with Beecher in homologizing the appendages, pair for pair, @@ -4331,7 +4291,7 @@ them around to the front when they could be used to advantage in that direction. <p>It has been the opinion of most observers that the exopodites of trilobites were swimming organs, while others have thought that they functioned also in aerating the blood. To the present writer it seems probable that the chief function was that of acting as gills, -for which the numerous thin, flattened or blade-like setæ are particularly adapted. That +for which the numerous thin, flattened or blade-like setæ are particularly adapted. That <span class="pagenum"><a name="Page_71" id="Page_71">[71]</a></span> they were also used in swimming is of course possible, but that was not their chief function. It should be remembered that the exopodites are always found dorsal to or above the endopodites, @@ -4343,7 +4303,7 @@ part at least of the exopodites were ventral to the endopodites. Specimens in th have not yet been seen among the fossils. To avoid having the exopodites and endopodites intermingled in this way, the animal would have to bring all the endopodites together along the axial line in a plane approximately perpendicular to the dorsal test, in which case -the exopodites would be free to act as swimming organs. The fact that the setæ of an +the exopodites would be free to act as swimming organs. The fact that the setæ of an exopodite stay together like the barbs on a feather would of course tend to strengthen the idea that the exopodites could be used in swimming, but that is not the only possible explanation of this condition. The union of the basipodite and exopodite shows that the two @@ -4354,10 +4314,10 @@ of oxygen.</p> <p>Although <i>Neolenus</i> is usually accounted a less primitive form than <i>Ptychoparia</i> or <i>Triarthrus</i>, it has much the most primitive type of exopodite yet known. It would appear -that the exopodites were originally broad, thin, simple lamellæ, which became broken up, -on the posterior side, into fine cylindrical setæ. As development progressed, more and more +that the exopodites were originally broad, thin, simple lamellæ, which became broken up, +on the posterior side, into fine cylindrical setæ. As development progressed, more and more of the original lamella was broken up until there remained only the anterior margin, which -became thickened and strengthened to support the delicate filaments. The setæ in turn became +became thickened and strengthened to support the delicate filaments. The setæ in turn became modified from their original simple cylindrical shape to form the wide, thin, blade-like filaments of <i>Cryptolithus</i> and <i>Ceraurus</i>.</p> @@ -4414,12 +4374,12 @@ as its merits seem to deserve. Two principal uses for a large pygidium of course one: either it might form a sort of operculum to complete the protection when the trilobite was enrolled, or it might serve as a swimming organ. That the former was one of its important functions is shown by the nicety with which the cephalon and pygidium are -adapted to one another in such families as the Agnostidæ, Asaphidæ, Phacopidæ, and others. +adapted to one another in such families as the Agnostidæ, Asaphidæ, Phacopidæ, and others. That a large pygidium is not essential to perfect protection on enrollment is shown by an equally perfect adjustment of the two shields in some families with small pygidia, notably -the Harpedidæ and Cheiruridæ That the large pygidial shields are not for protective purposes +the Harpedidæ and Cheiruridæ That the large pygidial shields are not for protective purposes only is also shown by those forms with large pygidia which are not adjusted to the -conformation of the cephalon, as in the Goldiidæ and Lichadidæ. It is evident that a large +conformation of the cephalon, as in the Goldiidæ and Lichadidæ. It is evident that a large pygidium, while useful to complete protection on enrollment, is not essential.</p> <p>It would probably be impossible to demonstrate that the trilobites used the pygidium @@ -4455,24 +4415,24 @@ the increased muscles necessary to properly operate the pygidium. It may be note in all these genera the axial lobe of the pygidium is either short or narrow.</p> <p>4. The geological history of the rise of caudalization favors this view. With the exception -of the Agnostidæ and Eodiscidæ, all Lower Cambrian trilobites had small pygidia, +of the Agnostidæ and Eodiscidæ, all Lower Cambrian trilobites had small pygidia, and the same is true of those of the Middle Cambrian of the Atlantic realm (except for the <i>Dorypyge</i> of Bornholm). In Pacific seas, however, large-tailed trilobites of the families -Oryctocephalidæ, Bathyuridæ, and Asaphidæ then began to be fairly common, though making +Oryctocephalidæ, Bathyuridæ, and Asaphidæ then began to be fairly common, though making up but a small part of the total fauna of trilobites. In the Upper Cambrian of the -Atlantic province the Agnostidæ were the sole representatives of the isopygous trilobites, -while in the Pacific still another family, the Dikelocephalidæ, was added to those previously +Atlantic province the Agnostidæ were the sole representatives of the isopygous trilobites, +while in the Pacific still another family, the Dikelocephalidæ, was added to those previously existing.</p> <p>With the Ordovician, caudalization reached its climax and the fashion swept all over the world. It is shown not so much in the proportion of families with large pygidia, as in -the very great development of the particular trilobites so equipped. Asaphidæ and Illænidæ -were then dominant, and the Proëtidæ, Cyclopygidæ Goldiidæ, and Lichadidæ had begun +the very great development of the particular trilobites so equipped. Asaphidæ and Illænidæ +were then dominant, and the Proëtidæ, Cyclopygidæ Goldiidæ, and Lichadidæ had begun their existence. A similar story is told by the Silurian record, except that the burden of -the Asaphidæ has been transferred to the Lichadidæ and Goldiidæ. All the really old (Cambrian) +the Asaphidæ has been transferred to the Lichadidæ and Goldiidæ. All the really old (Cambrian) families of trilobites with small pygidia had now disappeared. In the general dwindling -of the subclass through the Devonian and later Palæozoic, the few surviving species -with small pygidia were the first to go, and the proëtids with large abdominal shields the +of the subclass through the Devonian and later Palæozoic, the few surviving species +with small pygidia were the first to go, and the proëtids with large abdominal shields the last.</p> <p>The explanation of this history is probably to be found in the rise of the predatory @@ -4611,8 +4571,8 @@ of water toward the mouth, as every back stroke would reverse the motion.</p> genera now known. I have set forth on a previous page my reasons for thinking that they took little part in swimming, and I look upon them as being, in effect, leaf-gills. It seems probable that in all genera the exopodites were held rather close to the test, the shaft more -or less rigid, the filamentous setæ gracefully pendent, but pendent as a sheet and not individually, -there having been some method by which adjoining setæ were connected laterally. +or less rigid, the filamentous setæ gracefully pendent, but pendent as a sheet and not individually, +there having been some method by which adjoining setæ were connected laterally. Free contact with the water was thus obtained without the mingling of endopodites and exopodites which would have been so disastrous to progression.</p> @@ -4630,16 +4590,16 @@ to attribute to it such internal organs as seem, from a study of comparative ana to be primitive.</p> <p>The alimentary canal would be expected to be straight and simple, curving downward -to the mouth, and should be composed of three portions, stomodæum, mesenteron, and proctodæum, +to the mouth, and should be composed of three portions, stomodæum, mesenteron, and proctodæum, the first and last with chitinous lining. In modern Crustacea, muscle-bands run from the gut to part of the adjacent body wall, so that scars of attachment of these muscles -may be sought. At the anterior end of the stomodæum, they are usually especially strong. +may be sought. At the anterior end of the stomodæum, they are usually especially strong. From the mesenteron there might be pouch-like or tubular outgrowths.</p> <p>The heart would probably be long and tubular, with a pair of ostia for each somite.</p> <p>In modern Crustacea, the chief organs of renal excretion are two pairs of glands in the -head, one lying at the base of the antennæ and one at the base of the maxillæ. Only one +head, one lying at the base of the antennæ and one at the base of the maxillæ. Only one pair is functional at a time, but these are supposed to be survivors of a series of segmentally arranged organs, so that there might be a pair to each somite of a trilobite.</p> @@ -4741,7 +4701,7 @@ following ones more or less pressed aside. This process is easily followed phylo are clearly marked and the six segments of the head bounded by them are all of about the same size. In a head shield about 13 mm. long, the foremost segment is very much increased in size, the jaw lobes pressed still further apart; in adult forms both anterior segments are combined into the frontal swellings of the -glabella. In other groups this process proceeds phylogenetically still further, so that among the Phacopidæ +glabella. In other groups this process proceeds phylogenetically still further, so that among the Phacopidæ and in <i>Trinucleus</i>, behind the frontal swelling of the glabella only the last cephalic segment retains a certain independence. The frontal lobe is thus no definite part, although it is as a rule composed of the mesotergites of the first two cranidial segments.</p> @@ -4774,17 +4734,17 @@ preservation.</p> <tr> <td class="vtop" style="padding:0 10px;"><p class="fig_caption"><span class="smcap">Fig. 21.</span>—Transverse slice through <i>Ceraurus pleurexanthemus</i>, to show the dorsal sheath above the abdominal cavity. Specimen 118. Traced from a - photographic enlargement. × 4.</p> + photographic enlargement. × 4.</p> </td> <td class="vtop" style="padding:0 10px;"><p class="fig_caption"><span class="smcap">Fig. 22.</span>—Transverse section through the cephalon of <i>Ceraurus pleurexanthemus</i>, showing the abdominal sheath and the large mud-filled alimentary canal (clear white). Traced from a photographic enlargement. - Specimen 97. × 3.3.</p> + Specimen 97. × 3.3.</p> </td> <td class="vtop" style="padding:0 10px;"><p class="fig_caption"><span class="smcap">Fig. 23.</span>—Transverse section of the thorax of <i>Calymene senaria</i>, showing the large size of the mud-filled alimentary canal (clear white). Traced from a photographic enlargement One appendifer (also clear white) is - shown. Specimen 153. × 3.3.</p> + shown. Specimen 153. × 3.3.</p> </td> </tr> </table> @@ -4831,7 +4791,7 @@ canal was large, filling the part of the glabella below the heart; that the body provided with a chitinous dorsal sheath extending back into the thorax; and that the posterior portion of the mesenteron was likewise large and oval in section. Since the alimentary canal must be connected with the mouth and anus, some such restoration as that of -Jaekel is indicated. No chitinous lining of the stomodæum or proctodæum was found, but +Jaekel is indicated. No chitinous lining of the stomodæum or proctodæum was found, but it is not certain that any of the sections cut either of those regions.</p> <p class="section"><a name="Calymene_senaria" id="Calymene_senaria"></a> @@ -4856,7 +4816,7 @@ posteriorly.</p> <p class="section"><a name="Cryptolithus_goldfussi_Barrande" id="Cryptolithus_goldfussi_Barrande"></a> <i>Cryptolithus goldfussi</i> (Barrande).</p> -<p class="blockquot">Illustrated: Beyrich, Untersuch. über Trilobiten, Berlin, 1846, pl. 4, fig. 1c.—Barrande, Syst. Sil. Bohême, +<p class="blockquot">Illustrated: Beyrich, Untersuch. über Trilobiten, Berlin, 1846, pl. 4, fig. 1c.—Barrande, Syst. Sil. Bohême, vol. 1 1852, pl. 30, figs. 38, 39.</p> <p>Both Beyrich and Barrande have shown that from the posterior end of the axial lobe @@ -4875,7 +4835,7 @@ glabella, the anterior end of the thorax, and the posterior end of the pygidium, still packed full of a material somewhat darker in appearance than the matrix, while the remainder of it is open. A well defined constriction is present under the middle of the next to the last thoracic segment, but whether this is accidental or whether it indicates the point -where the mesenteron discharges into the proctodæum can not be determined. The inside +where the mesenteron discharges into the proctodæum can not be determined. The inside of the canal has somewhat of a lustre and there are three conical projections into it on the median ventral line, a very small one in front of the neck furrow, a larger one under the anterior part of the second segment, and a third between the fourth and fifth segments.</p> @@ -4888,9 +4848,9 @@ of the canal there was an enlarged organ which occupied the greater part of the the glabella. It appears that it extended into the thorax, and that above it and the heart was a chitinous dorsal sheath. Behind the enlarged portion, the mesenteron appears to have been of practically uniform diameter in <i>Cryptolithus</i>, but to have tapered posteriorly in -Ceraurus and <i>Calymene</i>. The proctodæum can not yet be differentiated from the mesenteron, +Ceraurus and <i>Calymene</i>. The proctodæum can not yet be differentiated from the mesenteron, and only in <i>Cryptolithus</i> has the posterior portion of the alimentary canal been seen. -It is, there, merely a continuation of the mesenteron. The stomodæum likewise has not been +It is, there, merely a continuation of the mesenteron. The stomodæum likewise has not been identified, but was probably a short gullet leading up from the mouth into the enlarged digestive cavity.</p> @@ -4903,9 +4863,9 @@ it. A restoration based on the slices described above.</p> </div> <p>The principle of the enlargement of the latter and its influence on the dorsal shell once -established, the significance of different types of glabellæ becomes apparent. It will be remembered +established, the significance of different types of glabellæ becomes apparent. It will be remembered that the glabella of the protaspis of most trilobites is narrow, and that the same -is true of the glabellæ of most ancient and all primitive trilobites. The free-swimming larvæ +is true of the glabellæ of most ancient and all primitive trilobites. The free-swimming larvæ and the free-swimming ancestors of the trilobites were probably strictly carnivorous, lived on concentrated food, and needed but a small digestive tract. As the animals "discovered the ocean bottom" and began to be omnivorous or herbivorous, larger stomachs were required, @@ -4923,9 +4883,9 @@ is at least worthy of consideration. Moberg, however (1902, p. 299), suggested t markings probably had something to do with the eyes rather than the stomach. He says in part (translation):</p> -<div class="blockquot"><p>In general we can now say that such features are common to all the eyeless Conocoryphidæ. With the +<div class="blockquot"><p>In general we can now say that such features are common to all the eyeless Conocoryphidæ. With the conocoryphs I include <i>Elyx</i> and consider Harpides as at least closely related. Similar impressions are also -found in forms with eyes, as, for instance, in the Olenidæ, but here such radiate partly from the border +found in forms with eyes, as, for instance, in the Olenidæ, but here such radiate partly from the border of the eye, partly from the front end of the glabella, partly from the [visual surface of the] eye, and sometimes from the angle between the occipital ring and the glabella. They therefore go out from such different points that they can not possibly be branches of the liver. It would also be very remarkable if such an @@ -4945,7 +4905,7 @@ represented the optic nerves, and since the eye-lines are usually the main trunk dendritic markings, it is fair to assume that he considered the whole as due to branches of nerves.</p> -<p>Reed has recently (1916, pp. 122, 173) discussed these lines as developed in the Trinucleidæ, +<p>Reed has recently (1916, pp. 122, 173) discussed these lines as developed in the Trinucleidæ, and seems to accept Beecher's explanation.</p> <p>Three explanations of the "nervures" are thus current, and the authors of all of them @@ -4958,10 +4918,10 @@ in position, is quite unlike what is seen in the trilobites.</p> <p>The term nervures, as applied to these markings, is not only misleading, but an incorrect use of one of Barrande's words, for by nervures he meant delicate surface markings. Until the real function of the organs which made these markings is definitely established, it -may be well to call them genal cæca, for they obviously were open tunnels ending blindly, +may be well to call them genal cæca, for they obviously were open tunnels ending blindly, whatever they contained.</p> -<p>The question of the function of the genal cæca can not, in any case, be settled by an +<p>The question of the function of the genal cæca can not, in any case, be settled by an appeal to <i>Limulus</i>, and it is doubtful if it can be settled at all at the present time. Certain things tend to show that Jacket's explanation is the most plausible, and these may be briefly set forth.</p> @@ -4979,26 +4939,26 @@ In the trilobites they debouch much further forward.</p> <p>The principal argument in favor of the interpretation of these markings as nerves lies in their connection with the eyes. There is considerable evidence to indicate that the eye-lines -and the genal cæca are two distinct structures, but because both originate from the +and the genal cæca are two distinct structures, but because both originate from the sides of the anterior lobe of the glabella, and both extend outward at nearly right angles -to the axis, or obliquely backward, they are, when both present, coincident. Genal cæca +to the axis, or obliquely backward, they are, when both present, coincident. Genal cæca occur on blind trilobites, on trilobites with simple eyes, and on trilobites with compound eyes. -Eye-lines occur on trilobites with both simple and compound eyes, and genal cæca may or +Eye-lines occur on trilobites with both simple and compound eyes, and genal cæca may or may not be present in both cases. The morphology of the ridge forming the eye-line in trilobites with compound eyes is well known. It is abundantly proved by ontogeny that it is the continuation of the palpebral lobe, and a development of the pleura of the first dorsal segment of the cephalon. Lake, Swinnerton, and Reed have tried to show that the eye-lines -of the Harpedidæ and Trinucleidæ are homologous with the eye-lines of the trilobites +of the Harpedidæ and Trinucleidæ are homologous with the eye-lines of the trilobites with compound eyes, and that the ocelli on the cheeks are therefore degenerate compound eyes.</p> -<p>The simplest form of the genal cæcum is seen in the blind <i>Elyx</i> (Lindstroem 1901, pl. +<p>The simplest form of the genal cæcum is seen in the blind <i>Elyx</i> (Lindstroem 1901, pl. 6, fig. 43). The main trunk is at nearly right angles to the axis, the increase in its width is gradual in approaching the glabella, and an equal number of branches diverge from both sides.</p> <p><i>Ptychoparia striata</i> (Barrande 1852, pl. 14, figs. 1, 3) is an excellent example of a trilobite -with compound eyes and genal cæca. It will be noted that the main trunk and the eye-line +with compound eyes and genal cæca. It will be noted that the main trunk and the eye-line are coincident, and that both on the free and fixed cheeks the branches are all on the anterior side of the eye-line. Compare this with the condition in <i>Conocoryphe</i> (Barrande, pl. 14, fig. 8; Lindstroem, pl. 6, fig. 44), and one sees there a main branch @@ -5008,16 +4968,16 @@ to the eyes, since <i>Conocoryphe</i> is blind, and the main trunk leads practic But although Conocoryphe is blind, it has free cheeks, and the main trunk does not lead to the point on those free cheeks where eyes are to be expected, but back into the genal angles. And this direction holds in such diverse genera (as to eyes and free cheeks) as <i>Harpes</i>, <i>Cryptolithus</i>, -<i>Dionide</i>, and <i>Endymionia</i>. In all these the genal cæca fade out in the genal angles, and +<i>Dionide</i>, and <i>Endymionia</i>. In all these the genal cæca fade out in the genal angles, and in none of them would compound eyes be expected in that region. The coincidence of the -eye-lines with the trunks of the genal cæca in <i>Ptychoparia</i> seems to be merely a coincidence. +eye-lines with the trunks of the genal cæca in <i>Ptychoparia</i> seems to be merely a coincidence. That the markings which radiate from the eyes of <i>Ptychoparia</i> and <i>Solenopleura</i> are not impressions made by nerves is obvious. That they are of the same nature as the similar markings in the eyeless trilobites is equally obvious. Ergo, they can not be nerves in either case, and that they have anything to do with the eyes is highly improbable. The eye was merely superimposed upon these structures.</p> -<p>The relation of the genal cæca to the ocelli on the cheeks is best shown in the Trinucleidæ. +<p>The relation of the genal cæca to the ocelli on the cheeks is best shown in the Trinucleidæ. In all species of <i>Tretaspis</i> simple eyes are present, and in most of them there are very narrow eye-lines. The latter are occasionally continued beyond the ocular tubercle back to the genal angle. A similar course is seen in <i>Harpes</i>. If the simple eye is the homologue @@ -5033,7 +4993,7 @@ show them, and one cheek is here figured (<a href="#fig_25">fig. 25</a>). As app main trunk is very short and gives rise to two principal branches, the first of which in its turn sends off lines from the anterior side. It was a specimen showing these lines which Ruedemann (1916, p. 147) figured as showing facial sutures. The interest lies in the fact -that while the ocelli and eye-lines were lost in development, the genal cæca are present +that while the ocelli and eye-lines were lost in development, the genal cæca are present in the adult, showing that they are different structures.</p> <div class="fig_right" style="width: 168px;"> @@ -5041,27 +5001,27 @@ in the adult, showing that they are different structures.</p> <img src="images/fig_25.png" width="168" height="133" alt="" title="" /> <p class="fig_caption"><span class="smcap">Fig. 25.</span>—<i>Cryptolithus tessellatus</i> Green. Side view of the cheek of a specimen from the top of the Trenton opposite Cincinnati, Ohio, to -show the branching genal cæca. These are the "facial sutures" of +show the branching genal cæca. These are the "facial sutures" of Ruedemann.</p> </div> -<p><i>Harpides</i> is another genus in which genal cæca are strikingly shown, and in this case +<p><i>Harpides</i> is another genus in which genal cæca are strikingly shown, and in this case they completely cover the huge cheeks, radiating from two main trunks to the front and sides. I have seen no good specimens, but it would appear from Angelin's figure (1854, pl. 41, fig. 7) that the rather large, simple eyes are not situated exactly on the vascular trunks. In the <i>Harpides</i> from Bohemia, the main trunks extend out with many branches beyond the -simple eyes. It should be stated that the courses of the genal cæca are not correctly figured +simple eyes. It should be stated that the courses of the genal cæca are not correctly figured by Barrande (Supplement, 1872, pl. 1, fig. 11), as shown by casts of the original specimen in the Museum of Comparative Zoology. From Barrande's figure, one would suppose that the eye-lines and their continuation beyond the "ocelli" were superimposed upon the genal -cæca without having any definite connection with them, but as a matter of fact the radial +cæca without having any definite connection with them, but as a matter of fact the radial markings really diverge from the main trunks as in <i>Elyx</i> and similar forms.</p> <p class="section"><a name="Summary84" id="Summary84"></a><i>Summary.</i></p> <p>As Reed has said, these lines are not mere ornamentation, but rather represent traces of structures of some functional importance. They probably can not be explained as traces -of nerves and more likely represent either traces of the gastric cæca or of the circulatory +of nerves and more likely represent either traces of the gastric cæca or of the circulatory <span class="pagenum"><a name="Page_85" id="Page_85">[85]</a></span> system. While they are known chiefly in Cambrian and Lower Ordovician trilobites, there is no evidence that the organs represented were not present in later forms, even if the shell @@ -5072,16 +5032,16 @@ which secreted the principal digestive fluids.</p> <p class="caption3"><a name="HEART" id="HEART"></a>HEART.</p> -<p class="section"><a id="Illaenus"></a><i>Illænus.</i></p> +<p class="section"><a id="Illaenus"></a><i>Illænus.</i></p> <p>Volborth (1863, pl. 1, fig. 12 = our <a href="#fig_26">fig. 26</a>) has described the only organ in a trilobite -which suggests a heart. A Russian specimen of <i>Illænus</i> with the shell removed shows a +which suggests a heart. A Russian specimen of <i>Illænus</i> with the shell removed shows a somewhat flattened, tubular, chambered organ extending from under the posterior end of the cephalon to the anterior end of the pygidium. The posterior nine chambers were each 1.5 mm. long and 1.5 mm. wide, while the two anterior chambers were respectively 2.5 mm. and 3 mm. wide. These were all under the thorax, and at least two more chambers are -shown under the cephalon, but rather obscurely. The species of the <i>Illænus</i> is not stated, -but since no <i>Illænus</i> has more than ten segments in the thorax, and this tube has at least +shown under the cephalon, but rather obscurely. The species of the <i>Illænus</i> is not stated, +but since no <i>Illænus</i> has more than ten segments in the thorax, and this tube has at least thirteen chambers, it is evident that its constrictions are inherent in it, and are not due to the segmentation of the thorax. Beecher has made a passing allusion to this organ as an alimentary canal. This was the original opinion of Volborth. Pander, however, suggested @@ -5089,7 +5049,7 @@ to him that it might be a heart. The alimentary canal of <i>Cryptolithus</i> doe constrictions, while the heart of <i>Apus</i> (see <a href="#fig_27">fig. 27</a>) and other branchiopods does show them. It should be noted, further, that while this heart enlarges toward the front, it is everywhere very small as compared with the width of the axial lobe, and much narrower than sections -of <i>Ceraurus</i> and <i>Calymene</i> would lead one to expect the alimentary canal of <i>Illænus</i> to be. +of <i>Ceraurus</i> and <i>Calymene</i> would lead one to expect the alimentary canal of <i>Illænus</i> to be. Where the heart is 1.5 mm. to 3 mm. wide, the axial lobe is 11 mm. wide.</p> <table summary="Figs. 26-27"> @@ -5101,9 +5061,9 @@ Where the heart is 1.5 mm. to 3 mm. wide, the axial lobe is 11 mm. wide.</p> </tr> <tr> <td class="vtop" style="padding:0 10px;"><p class="fig_caption"><span class="smcap">Fig. 26.</span> Copy of - Volborth's figure of the heart of <i>Illænus</i>.</p></td> + Volborth's figure of the heart of <i>Illænus</i>.</p></td> <td class="vtop" style="padding:0 10px;"><p class="fig_caption"><span class="smcap">Fig. 27.</span> Heart of - <i>Apus</i>. Copied from Gerstäcker.</p></td> + <i>Apus</i>. Copied from Gerstäcker.</p></td> </tr> </table> @@ -5127,9 +5087,9 @@ presence in the fossils.</p> <p>Many trilobites, otherwise smooth, bear on the glabella a median pustule which is usually referred to as a simple eye or median ocellus, but whose function can not be said to have been certainly demonstrated. Ruedemann (1916, p. 127), who has recently made a careful -study of this problem, lists about thirty genera, members of ten families, Agnostidæ, Eodiscidæ -Trinucleidæ, Harpedidæ, Remopleuridæ, Asaphidæ Illænidæ, Goldiidæ, Cheiruridæ, -and Phacopidæ, in which this tubercle is present, and had he wished he might have cited +study of this problem, lists about thirty genera, members of ten families, Agnostidæ, Eodiscidæ +Trinucleidæ, Harpedidæ, Remopleuridæ, Asaphidæ Illænidæ, Goldiidæ, Cheiruridæ, +and Phacopidæ, in which this tubercle is present, and had he wished he might have cited more, for it is of almost universal occurrence in Ordovician trilobites.</p> <p>I have not especially searched the literature for references to this median tubercle. It @@ -5158,7 +5118,7 @@ the original form of the sac. His summary follows:</p> proof of this assertion the following facts are stated:]</p> <p>1. A great number of species, belonging to more than thirty genera, possess a distinct tubercle on the -glabella. This tubercle occurs alone in many genera, otherwise smooth, as in the Asaphidæ, and is hence of +glabella. This tubercle occurs alone in many genera, otherwise smooth, as in the Asaphidæ, and is hence of functional importance.</p> <p>2. In certain cases, as in <i>Cryptolithus tessellatus</i>, distinct lenticular bodies [not lenses] were recognized; @@ -5223,7 +5183,7 @@ it is in the neck furrow. In species with compound eyes it is frequently between eyes, but more often back of them. If its history be traced in a single family, it is generally found farthest forward in the more ancient species and moves backward in the more recent ones. The eyes do this same thing, but the median tubercle goes back further than -the eyes. This can be seen, for example, in the American Asaphidæ, where the pustule is +the eyes. This can be seen, for example, in the American Asaphidæ, where the pustule is up between the eyes of <i>Hemigyraspis</i> and <i>Symphysurus</i> of the Beekmantown and back of the eyes of the <i>Isotelus</i> of the Trenton. Turning now to the under side of the head, it appears that the tubercle bears a rather definite relation to the hypostoma. If the hypostoma is short, @@ -5234,32 +5194,32 @@ mouth, while in others it is not as far back as the tip of the hypostoma.</p> <p>The median tubercle is in many cases developed into a long spine. This is usually in an ancient member of a tubercle-bearing family, and suggests that in most cases the tubercle is a vestigial organ. An example of this occurs in <i>Trinucleoides</i>, the most ancient -of the Trinucleidæ. <i>Trinucleoides reussi</i> (Barrande) (Supplement, 1872, pl. 5, figs. 17, 18) +of the Trinucleidæ. <i>Trinucleoides reussi</i> (Barrande) (Supplement, 1872, pl. 5, figs. 17, 18) has a very long slender spine in this position. It could be explained as an elevated median -eye, but it also very strongly suggests the zoæal spine of modern brachyuran Crustacea. +eye, but it also very strongly suggests the zoæal spine of modern brachyuran Crustacea. <span class="pagenum"><a name="Page_88" id="Page_88">[88]</a></span> Gurney (Quart. Jour. Mic. Sci., vol. 46, 1902, p. 462) supports Weldon in the conclusion -that the long spines of the zoæa are directive, and states that the animal swims in the direction +that the long spines of the zoæa are directive, and states that the animal swims in the direction of the long axis of the spine. He also suggests that, since the period of their presence corresponds to the period before the development of the "auditory" organs, the spines may perform the functions of balancing and orientation. It is generally admitted that the spine -of the zoæa is also protective, and the obvious function, first pointed out by Spence Bate +of the zoæa is also protective, and the obvious function, first pointed out by Spence Bate in 1859, is that it contains a ligament which helps suspend the heart, which lies beneath the spine. This latter function may have been that of the median tubercle in the trilobite. Such an explanation would account for the backward migration mentioned above, for as the stomach enlarged and the mouth moved backward on the ventral side, the heart may have been pushed backward on the upper side.</p> -<p>There is also a curious parallelism between the ontogenetic history of the zoæal spine -and the phylogenetic history of the Trinucleidæ or Cheiruridæ (Nieszkowskia is the ancient +<p>There is also a curious parallelism between the ontogenetic history of the zoæal spine +and the phylogenetic history of the Trinucleidæ or Cheiruridæ (Nieszkowskia is the ancient member of this family in which the spine replaces the tubercle). When first hatched, the larval crab shows no trace of the spine, but very quickly it evaginates, lying dorsally on the median line, pointing forward (Faxon, Bull. Mus. Comp. Zool., vol. 6, 1880, pl. 2). With the splitting of the original envelope, the spine becomes erect, but persists only a short time, -and is reduced to a vestigial tubercle toward the end of the zoæal stages, its disappearance being, +and is reduced to a vestigial tubercle toward the end of the zoæal stages, its disappearance being, as pointed out by Gurney, coincident with the development of the balancing organs. This manner of suspension of the heart by a long tendon certainly does suggest that Gurney is -right in his interpretation of the function. Briefly, the zoæal spine served for a short time +right in his interpretation of the function. Briefly, the zoæal spine served for a short time a function later taken over by other organs. It was not present in the youngest stages, it became prominent at a very early stage, was soon vestigial, and then lost.</p> @@ -5268,14 +5228,14 @@ any form, and in many primitive trilobites it is absent. It appears first as a l certain families, and later becomes vestigial and disappears. Very few trilobites of Silurian and later times show it at all.</p> -<p>In the particular case of the Trinucleidæ, which were burrowers, the spine is present +<p>In the particular case of the Trinucleidæ, which were burrowers, the spine is present on only the oldest and most primitive of the group, a form which has only a most rudimentary fringe. It is obvious from the large size of the pygidium in the larval trinucleid that this family is derived from a group of free swimmers. <i>Trinucleoides reussi</i> was perhaps in the transitional stage, just leaving the swimming mode of life, and belonged to a group which had not developed any other "statocyst" than the median spine. Among the later -Trinucleidæ the spine became a vestigial tubercle, and in some cases entirely disappeared. A -similar history can be traced in the Cheiruridæ, starting from some such forms as the American +Trinucleidæ the spine became a vestigial tubercle, and in some cases entirely disappeared. A +similar history can be traced in the Cheiruridæ, starting from some such forms as the American Lower Ordovician <i>Nieszkowskia</i> (<i>N. perforator</i> p. ex.).</p> <p>Another example of a median spine instead of a tubercle is in Goldius rhinoceros (Barrande). @@ -5290,7 +5250,7 @@ interpretation.</p> <p>3. This tubercle is essentially similar to other tubercles on the median line of cephalon, thorax, and even pygidium. This has been discussed sufficiently under section 1 above, but <span class="pagenum"><a name="Page_89" id="Page_89">[89]</a></span> -it may perhaps be justifiable to point out that in some of the Agnostidæ there is a median +it may perhaps be justifiable to point out that in some of the Agnostidæ there is a median tubercle on both shields, and since it has not yet been demonstrated beyond question which shield is the cephalon, to say which one is a parietal eye and which one is a tubercle is impossible. In other words, the parietal eye can not be differentiated from any other tubercle @@ -5312,7 +5272,7 @@ is known.</p> <p class="caption3"><a name="NERVOUS_SYSTEM" id="NERVOUS_SYSTEM"></a>NERVOUS SYSTEM.</p> <p>There has been a rather general impression among students of trilobites that the eye-lines, -which should be differentiated from the genal cæca, denote the course of the optic +which should be differentiated from the genal cæca, denote the course of the optic nerves, but no other evidence of the nervous system has been found, save the so called nervures which have been discussed above. In <i>Apus</i> the nerves leading to the eyes come off from the anterior ganglion or "brain" and run directly to the eyes. If conditions were @@ -5326,7 +5286,7 @@ and "nervures" are present. Beecher (1895 C, p. 171, pl. 8, figs. 5-7) has shown <i>Ptychoparia kingi</i> the eye-lines of a specimen in the metaprotaspis stage run forward at a low angle with the glabella, while in the adult their course is nearly at right angles to it. They have therefore swung through an arc of at least 60 and in so doing have had ample opportunity -to become coincident with the primary trunks of the genal cæca. Once that was accomplished, +to become coincident with the primary trunks of the genal cæca. Once that was accomplished, it is quite likely that the one fold in the shell would continue to house both structures. In other trilobites, there is a similar backward progression of the eye-lines.</p> @@ -5353,8 +5313,8 @@ open at the top, were poisonous also, and had glands at the base. These are, how purely matters of speculation so far.</p> <p><a id="Renal_excretory_organs"></a><i>Renal excretory organs.</i>—Nothing has been seen of any such organs, unless the genal -cæca may possibly be of that nature. The main trunks of these always lead to the sides -of the anterior glabellar lobe, which is not the point of attachment of either antennæ or +cæca may possibly be of that nature. The main trunks of these always lead to the sides +of the anterior glabellar lobe, which is not the point of attachment of either antennæ or biramous limbs, so that there seems little chance that they will bear this interpretation.</p> <p><a id="Reproductive_organs"></a><i>Reproductive organs.</i>—Nothing is yet positively known about the reproductive organs @@ -5375,10 +5335,10 @@ appendages. Billings (1870) described and figured the "Panderian organs" of "<i> platycephalus</i>" and stated that he had seen them in <i>Asaphus</i> [<i>Ogygites</i>] <i>canadensis</i> and <i>A. megistos</i> [<i>Isotelus maximus</i>] as well. He thought some sort of organ was attached to them, but could not suggest its function. Woodward (1870) thought that the openings were -"only the fulcral points on which the pleuræ move." Their position outside the fulcra shows +"only the fulcral points on which the pleuræ move." Their position outside the fulcra shows that this explanation is impossible.</p> -<p>So far as I am aware, the Panderian organs have been seen only in the Asaphidæ. +<p>So far as I am aware, the Panderian organs have been seen only in the Asaphidæ. Barrande figured them in "<i>Ogygia</i>" [<i>Hemigyraspis</i>] <i>desiderata</i> (1872) and Schmidt in two species of <i>Pseudasaphus</i>. They seem to occupy the same position in Bohemian, Russian, and American specimens. There is always one pair of openings on each thoracic segment, @@ -5389,7 +5349,7 @@ There seem to be no markings on the interior of the shell which are connected wi <p>While thinking over the trilobites in connection with the origin of insects, it occurred to me that these hitherto unexplained Panderian organs might possibly be openings to internal -gills and that the Asaphidæ might have been tending toward an amphibious existence. On +gills and that the Asaphidæ might have been tending toward an amphibious existence. On mentioning this to Doctor R. V. Chamberlin of the Museum of Comparative Zoology, he called my attention to the possibility that they might be openings similar to those of the repugnatorial glands of Diplopoda. While no definite decision as to the function can be @@ -5414,7 +5374,7 @@ been found with them. Moreover, Walcott sliced specimens of <i>Isotelus</i> from and found only endopodites. It may also be recalled that the finding of the specimen of <i>Isotelus arenicola</i> at Britannia and the tracks which I attributed to it, suggested to me that it was a shore-loving animal (1910). It offers a field for further inquiry, whether the -Asaphidæ may not have had internal gills, and whether some primitive member of the family +Asaphidæ may not have had internal gills, and whether some primitive member of the family may not have given rise to tracheate arthropods.</p> <div class="fig_center" style="width:233px"> @@ -5495,7 +5455,7 @@ have been attached chiefly on the under side of the anterior ring of the axial l strands probably continued further back. This is above and slightly in front of the fulcral points on the pleura, and meets the mechanical requirements. <i>Ceraurus</i> (Walcott, 1875, and 1881, p. 222, pl. 4, fig. 5) shows a pair of very distinct scars on the under side of the first -ring of the pygidium, and in many other trilobites (<i>Illænus</i>, <i>Goldius</i>, etc.) distinct traces of +ring of the pygidium, and in many other trilobites (<i>Illænus</i>, <i>Goldius</i>, etc.) distinct traces of muscular attachment can be seen in this region, even from the exterior. The anterior ends were probably attached by numerous small strands to the top of the glabella, and, principally, to the neck-ring.</p> @@ -5542,17 +5502,17 @@ all four are probably somewhat out of place.</p> absent, but in no trilobite has it ever been seen ankylosed to the dorsal test, and its rather frail connection therewith is evidenced by the relative rarity of specimens found with it in position. That the hypostoma was movable seems very probable, and that it was held in -place by muscles, certain. The maculæ were always believed to be muscle scars until Lindstroem +place by muscles, certain. The maculæ were always believed to be muscle scars until Lindstroem (1901, p. 8) announced the discovery by Liljevall of small granules on those of <i>Goldius polyactin</i> (Angelin). These were interpreted as lenses of eyes by Lindstroem, who -tried to show that the maculæ of all trilobites were functional or degenerate eyes. Most palæontologists +tried to show that the maculæ of all trilobites were functional or degenerate eyes. Most palæontologists have not accepted this explanation, and since the so called eyes cover only a -part of the surface of the maculæ, it is still possible to consider the latter as chiefly muscle-scars.</p> +part of the surface of the maculæ, it is still possible to consider the latter as chiefly muscle-scars.</p> <p>In Lindstroem's summary (1901, pp. 71, 72) it is admitted that the globular lenses are found only in <i>Bronteus</i> (<i>Goldius</i>) (three Swedish species only) and <i>Cheirurus spinulosus</i> Nieszkowski, while the prismatic structure supposed to represent degenerate eyes was -found in eleven genera (Asaphidæ, Illænidæ, Lichadidæ). All of these are forms with well +found in eleven genera (Asaphidæ, Illænidæ, Lichadidæ). All of these are forms with well developed eyes, and Lindstroem himself points out that the appearance of actual lenses in the hypostoma was a late development, long after the necessity for them would appear to have passed.</p> @@ -5561,7 +5521,7 @@ have passed.</p> from his remarks are quoted:</p> <p class="blockquot">The earliest crustacean-annelids possessed large labra or prostomia projecting backward, still retained -in the Apodidæ and trilobites. This labrum almost necessitated a very deliberate manner of browsing. The +in the Apodidæ and trilobites. This labrum almost necessitated a very deliberate manner of browsing. The animal would creep along, and would have to run some way over its food before it could get it into its mouth, the whole process, it seems to us, necessitating a number of small movements backwards and forwards. Small living prey would very often escape, owing to the fact that the animal's mouth and jaws were not @@ -5584,7 +5544,7 @@ until the point or prongs rested on or in the substratum, and sending food forwa to the mouth by means of the appendages, a trilobite could make of itself a most excellent trap, and if the animal could dart backward as well as forward, the hypostoma would be still more useful. There is no reason to suppose that they could not move backward, and the -"pygidial antennæ" of <i>Neolenus</i> indicate that animals of that genus at least did so. This +"pygidial antennæ" of <i>Neolenus</i> indicate that animals of that genus at least did so. This habit of dropping down the hypostoma would also permit the use of those anterior gnathobases which seem too far ahead of the mouth in the trilobites with a long hypostoma.</p> @@ -5609,7 +5569,7 @@ the sides.</p> pleurexanthemus</i>, to show position of the mouth and folds of the ventral membrane between the glabella and the hypostoma. The test is in solid black and the part within the ventral membrane dotted. From a - photographic enlargement. Specimen 169. × 3.9.</p> + photographic enlargement. Specimen 169. × 3.9.</p> </td> <td class="center vtop" style="padding:0 10px; width: 266px;"><p class="fig_caption"><span class="smcap">Fig. 31.</span>—A copy of Doctor Moberg's figure of <i>Nileus armadillo</i>, showing the position of the muscle scars.</p> @@ -5622,7 +5582,7 @@ efficient than those of the labrum of <i>Apus</i>, and it is probable that they test. Just where they were attached is an unsolved problem. Barrande (1852, pl. 1, fig. 1) has indicated an anterior pair of scars and a single median one on the frontal lobe of <i>Dalmanites</i> that may be considered in this connection, and also three pairs of scars on the -last two lobes of the glabella of <i>Proëtus</i> (1852, pl. 1, fig. 7). Moberg (1902, p. 295, pl. 3, +last two lobes of the glabella of <i>Proëtus</i> (1852, pl. 1, fig. 7). Moberg (1902, p. 295, pl. 3, figs. 2, 3, text fig. 1) has described in some detail the muscle-scars of a rather remarkable specimen of <i>Nileus armadillo</i> Dalman. While, as I shall point out, I do not agree wholly with Professor Moberg's interpretation, I give here a translation (made for Professor @@ -5649,18 +5609,18 @@ appendages. Against this it may be urged that impression d is too far forward to first pair of feet. Again, the impression h may in reality represent two confluent muscular insertions, from the first of which, in that case, arose the muscles of the fourth pair of cephalic feet. Were this the case, the muscles of the first pair of cheek feet should be attached at e. And d in turn may be explained as the -attachment of the muscles of the antennæ, k those of the hypostoma, and from i possibly those of the epistoma. -That k is here named as the starting point of the hypostomial muscles and not those of the antennæ, depends +attachment of the muscles of the antennæ, k those of the hypostoma, and from i possibly those of the epistoma. +That k is here named as the starting point of the hypostomial muscles and not those of the antennæ, depends partly on the analogous position of i and partly on the fact that the hypostoma of <i>Nileus armadillo</i> (text figure, in which the outline of the hypostoma is dotted), by reason of it? wing-like border, could not have -permitted the antennæ to reach forward, but rather only outward or backward.</p> +permitted the antennæ to reach forward, but rather only outward or backward.</p> </div> <p>My own explanation would be that impressions e, f, and g correspond to the glabellar furrows, h the neck furrow, and all four show the places of attachment of the appendifers. -Those at d may possibly be connected with the antennæ, although I should expect those +Those at d may possibly be connected with the antennæ, although I should expect those organs to be attached under the dorsal furrows at the sides of the hypostoma. It will -be noted that either b, k, or i correspond well with the maculæ of the hypostoma and some +be noted that either b, k, or i correspond well with the maculæ of the hypostoma and some or all of them may be the points of attachment of hypostomial muscles. They correspond also with the anterior scars of <i>Dalmanites</i>.</p> @@ -5672,10 +5632,10 @@ sketch of the anatomy would be incomplete without some reference to the little w been done on the structure of these organs.</p> <p>Quenstedt (1837, p. 339) appears to have been the first to compare the eyes of trilobites -with those of other Crustacea. Johannes Müller had pointed out in 1829 (Meckel's +with those of other Crustacea. Johannes Müller had pointed out in 1829 (Meckel's Archiv) that two kinds of eyes were found in the latter group, compound eyes with a smooth cornea, and compound eyes with a facetted coat. Quenstedt cited <i>Trilobites esmarkii</i> Schlotheim -(=<i>Illænus crassicauda</i> Dalman) as an example of the first group, and <i>Calymene macrophthalma</i> +(=<i>Illænus crassicauda</i> Dalman) as an example of the first group, and <i>Calymene macrophthalma</i> Brongniart (=<i>Phacops latifrons</i> Bronn) for the second. Misreading the somewhat careless style of Quenstedt, Barrande (1852, p. 133) reverses these, one of the few slips to be found in the voluminous writings of that remarkable savant.</p> @@ -5719,14 +5679,14 @@ trilobites with stemmata and ocelli. His views may be briefly summarized.</p> <p>"A pellucid, smooth and glossy integument, a direct continuation of the common test of the body, covers the corneal lenses, quite as is the case in so many of the recent Crustacea. The lenses are closely packed, minute, usually hexagonal in outline, flat on the outer and convex on the inner surface. Such eyes are best -developed in <i>Asaphus</i>, <i>Illænus</i>, <i>Nileus</i>, <i>Bumastus</i>, <i>Proëtus</i>, etc."</p> +developed in <i>Asaphus</i>, <i>Illænus</i>, <i>Nileus</i>, <i>Bumastus</i>, <i>Proëtus</i>, etc."</p> <p>2. Eyes with biconvex lenses.</p> <p>The surface of the eye is a mass of contiguous lenses, covered by a thin membrane which is frequently absent from the specimens, due to poor preservation. The lenses are biconvex, and being in contact with one another, are usually hexagonal, although in some cases they nearly retain their globular shape. Such eyes -are found in Bury care, <i>Peltura</i>, <i>Sphæropthalmus</i>, <i>Ctenopyge</i>, <i>Goldius</i>, <i>Cheirurus</i>, and probably others.</p> +are found in Bury care, <i>Peltura</i>, <i>Sphæropthalmus</i>, <i>Ctenopyge</i>, <i>Goldius</i>, <i>Cheirurus</i>, and probably others.</p> <p>II. Aggregate eyes.</p> @@ -5735,7 +5695,7 @@ There is, however, a thin membrane, which covers all those in any one aggregate, the general integument of the body. This membrane is continued as a thickened infolding which forms the sockets of the lenses.</p> -<p>Such eyes are known in the Phacopidæ only.</p> +<p>Such eyes are known in the Phacopidæ only.</p> <p>III. Stemmata and ocelli.</p> @@ -5744,7 +5704,7 @@ ocelli lying near one another. Each, viewed from above, is nearly circular in ou glossy and shining. In section they prove to be convex above and flat or slightly concave beneath. The test covers and separates them, as in the case of the aggregate eyes.</p> -<p>The ocelli of the Trinucleidæ and <i>Eoharpes</i> are smaller, and the detailed structure not yet investigated.</p> +<p>The ocelli of the Trinucleidæ and <i>Eoharpes</i> are smaller, and the detailed structure not yet investigated.</p> <p>Lindstroem concludes that so far as its facets or lenses are concerned, the eye of the trilobite shows the greatest analogy with the Isopoda, and the least with <i>Limulus</i>.</p> @@ -5772,7 +5732,7 @@ eyes than those with the other type.</p> <p>If, as some investigators claim, the parietal eye of Crustacea originates by the fusion of two lateral ocelli, trilobites show a primitive condition in lacking this eye, which may have -originated through the migration toward the median line of ocelli like those of the Trinucleidæ.</p> +originated through the migration toward the median line of ocelli like those of the Trinucleidæ.</p> <p class="caption3"><a name="SEX" id="SEX"></a>SEX.</p> @@ -5781,7 +5741,7 @@ originated through the migration toward the median line of ocelli like those of study of the appendages has as yet revealed nothing in the way of sexual differences. One of the most important points still to be determined is the location of the genital openings.</p> -<p>In many modern Crustacea, the antennæ or antennules are modified as claspers, and it +<p>In many modern Crustacea, the antennæ or antennules are modified as claspers, and it is barely possible that the curious double curvature of the antennules of Triarthrus indicates a function of this sort. The antennules of many specimens have the rather formal double curvature, turning inward at the outer ends, and retain this position of the frontal @@ -5853,7 +5813,7 @@ of this large fin, a backward darting motion could be obtained, which would be i as a means of escape from enemies. Staff and Reck seem to think that in this movement the two shields were clapped together, and that the animal was projected along with the hinge-like thorax forward. This might be a very plausible explanation in the case of the bivalve-like -Agnostidæ, and it is one I had suggested tentatively for that family before I read Staff +Agnostidæ, and it is one I had suggested tentatively for that family before I read Staff and Reck's paper. In the case of the large trilobites with more segments, however, it would be more natural to think of a mode of progression in which there was an undulatory movement of the body and the pygidium, up-and-down strokes being produced by alternately @@ -5867,10 +5827,10 @@ and antennules as rudders.</p> <p>The chief objection to the theory of swimming by clapping the valves together is that where the thorax consists of several segments it no longer acts like the hinge of a bivalve, and a sudden downward flap of the pygidium would impart a rotary motion to the animal. -Take, for example, such nearly spherical animals as the Illænidæ, and it will readily be seen +Take, for example, such nearly spherical animals as the Illænidæ, and it will readily be seen that there is nothing to give direction to the motion if the pygidium be brought suddenly against the lower surface of the cephalon. A lobster, it is true, progresses very well by -this method, but it depends upon its great claws and long antennæ to direct its motions. +this method, but it depends upon its great claws and long antennæ to direct its motions. The whole shape of the trilobite is of course awkward for a rapidly swimming animal. It could keep afloat with the minimum of effort and paddle itself about with ease, but it was not built on the correct lines for speed.</p> @@ -5925,7 +5885,7 @@ species to the terminal spine of <i>Olenellus</i> proper, suggests that in the l purely membranous character may have existed devoid of hard parts.</p></div> <p>This prophecy was fulfilled by the discovery of the specimens which Walcott described -as <i>Pædeumias transitans</i>, a species which is said by its author to be a "form otherwise +as <i>Pædeumias transitans</i>, a species which is said by its author to be a "form otherwise identical with <i>O. thompsoni</i>, [but] has rudimentary thoracic segments and a <i>Holmia</i>-like pygidium posterior to the fifteenth spine-bearing segment of the thorax." A good specimen of this form was found at Georgia, Vermont, associated with the ordinary specimens @@ -5936,14 +5896,14 @@ shown by Walcott (Smithson. Misc. Coll., vol. 64, 1916, p. 406, pl. 45, fig. 3) <i>Mesonacis</i> and to have seven or eight thoracic segments and a small plate-like pygidium back of the spine-bearing fifteenth segment. All indications are that the spine was not in any sense a pygidium. Walcott states that <i>Olenellus</i> resulted from the resorption of the -rudimentary segments of forms such as <i>Mesonacis</i> and <i>Pædeumias</i>, leaving the spine to +rudimentary segments of forms such as <i>Mesonacis</i> and <i>Pædeumias</i>, leaving the spine to function as a pygidium. This would mean the cutting off of the anus and the posterior part of the alimentary canal, and developing a new anal opening on the spine of one of the thoracic segments!</p> <p>If the spine of the fifteenth segment is not a pygidium, could it be used, as Dollo postulates, as a pushing organ? Presumably not, for though in entire specimens of <i>Olenellus</i> -(<i>Pædeumias</i>) it extends back beyond the pygidium, it probably was borne erect, like the +(<i>Pædeumias</i>) it extends back beyond the pygidium, it probably was borne erect, like the similar spines in <i>Elliptocephala</i>, and not in the horizontal plane in which it is found in crushed specimens.</p> @@ -5955,8 +5915,8 @@ burrowing.</p> <p>Staff and Reck have pointed out that <i>Dalmanites limulurus</i> was not entirely a crawler, but, as shown by the large pygidium, a swimmer as well. This kind of trilobite probably -represents the normal development of the group in Ordovician and later times. The Phacopidæ, -Proëtidæ, Calymenidæ, and other trilobites of their structure could probably crawl +represents the normal development of the group in Ordovician and later times. The Phacopidæ, +Proëtidæ, Calymenidæ, and other trilobites of their structure could probably crawl or swim equally well, and could escape enemies by darting away or by "digging themselves in."</p> @@ -5966,14 +5926,14 @@ he appealed to Beecher's interpretation of the appendages, and pointed out that adult is blind, the young have simple eyes and probably passed part of their life in the lighted zone. It needs only a glance at the very young to convince one that the embryos had swimming habits, so that in this form one sees the adaptation of the individual during -its history to all modes of life open to a trilobite. The habits of the Harpedidæ may have -been similar to those of the Trinucleidæ, but the members of this family are supplied with +its history to all modes of life open to a trilobite. The habits of the Harpedidæ may have +been similar to those of the Trinucleidæ, but the members of this family are supplied with broad flat genal spines. It has been suggested that these served like pontoons, runners, or snow-shoes, to enable the animal to progress over soft mud without sinking into it. Some such explanation might also be applied to the similar development in the wholly unrelated -Bathyuridæ. The absence of compound eyes and the poor development of ocelli in the Harpedidæ -suggest that they were burrowers, and from these two families, Trinucleidæ and -Harpedidæ, it becomes evident that a pygidial point or spine is not a necessary part of the +Bathyuridæ. The absence of compound eyes and the poor development of ocelli in the Harpedidæ +suggest that they were burrowers, and from these two families, Trinucleidæ and +Harpedidæ, it becomes evident that a pygidial point or spine is not a necessary part of the equipment of a burrowing trilobite. In fact, from the habits of <i>Limulus</i> it is known that the appendages are relied upon for digging, and that the telson is a useful but not indispensable pushing organ.</p> @@ -5990,13 +5950,13 @@ a swimming pygidium, and that the great development of spines suggests a floatin than a swimming mode of life. They therefore argue for a planktonic habitat. A similar explanation is suggested for <i>Acidaspis</i> and other highly spinose species.</p> -<p>The Aeglinidæ, or Cyclopygidæ as they are more properly called, present the most remarkable +<p>The Aeglinidæ, or Cyclopygidæ as they are more properly called, present the most remarkable development of eyes among the trilobites. In this, Dollo saw, as indeed earlier writers have, an adaptation to a region of scanty light. The cephalon is not at all adapted to burrowing, but the pygidium is a good swimming organ, and one is apt to agree that this animal was normally an inhabitant of the ill lighted dysphotic region, but also a nocturnal prowler, making trips to the surface at night. Similar habits and habitat are certainly indicated -for <i>Telephus</i> and the Remopleuridæ, but whether <i>Nileus</i> and the large-eyed <i>Bumastus</i> +for <i>Telephus</i> and the Remopleuridæ, but whether <i>Nileus</i> and the large-eyed <i>Bumastus</i> are capable of the same explanation is doubtful.</p> <p>Finch (1904, p. 181) makes the suggestion that "<i>Nileus</i>" (<i>Vogdesia</i>) <i>vigilans</i>, an @@ -6017,18 +5977,18 @@ of complete enrolled specimens of all ages now found there. The soft mud was app fatal to the species before the end of the Maquoketa, for specimens are seen but very rarely in the higher beds.</p> -<p><i>Vogdesia vigilans</i> is shaped much like <i>Bumastus</i>, <i>Illænus</i>, <i>Asaphus</i>, <i>Onchometopus</i>, and +<p><i>Vogdesia vigilans</i> is shaped much like <i>Bumastus</i>, <i>Illænus</i>, <i>Asaphus</i>, <i>Onchometopus</i>, and <i>Brachyaspis</i>, and it may be that these trilobites with incurved pygidia had all adopted the habit of digging in backward. As noted above, their pygidia are not very well adapted for swimming, and most of them have large or tall eyes.</p> -<p>Dollo's comparison of the Cyclopygidæ to the huge-eyed modern amphipod <i>Cystosoma</i> +<p>Dollo's comparison of the Cyclopygidæ to the huge-eyed modern amphipod <i>Cystosoma</i> is instructive. This latter crustacean, which has the greater part of the dorsal surface of the carapace transformed into eyes, is said to live in the dysphotic zone, at depths of from 40 to 100 fathoms, and to come to the surface at night. It swims ventral side down.</p> <p>The kinds of sediments in which trilobites are entombed have so far afforded little evidence -as to their habitat. Frech (Lethæa palæozoica, 1897-1902, p. 67 <i>et seq.</i>) who has +as to their habitat. Frech (Lethæa palæozoica, 1897-1902, p. 67 <i>et seq.</i>) who has collected such evidence as is available on this subject, places as deeper water Ordovician deposits the "Trinucleus-Schiefer" of the upper Ordovician of northern Europe and Bohemia, the "Triarthrus-Schiefer" of America, the "Asaphus-Schiefer" of Scandinavia, Bohemia, @@ -6038,10 +5998,10 @@ Portugal, and France, and the Dalmania quartzite of Bohemia. .</p> <span class="pagenum"><a name="Page_103" id="Page_103">[103]</a></span> chiefly in very fine-grained shales, in company with graptolites. These latter are distributed by currents over great distances within short periods. It is somewhat curious that the nearly -blind burrowing Trinucleidæ, the dysphotic, large-eyed Remopleuridæ and Telephus, the blind -nektonic Agnostidæ and Dionide, and the planktonic graptolites should go together and make +blind burrowing Trinucleidæ, the dysphotic, large-eyed Remopleuridæ and Telephus, the blind +nektonic Agnostidæ and Dionide, and the planktonic graptolites should go together and make up almost the entire fauna of certain formations. Yet, when the life history of each type -is studied, a logical explanation is readily at hand, for all have free-swimming larvæ.</p> +is studied, a logical explanation is readily at hand, for all have free-swimming larvæ.</p> <p>A list of the methods of life noted above is given by way of summary, with examples.</p> @@ -6070,12 +6030,12 @@ is studied, a logical explanation is readily at hand, for all have free-swimming (only partially nektonic)</td> </tr> <tr> - <td>Cyclopygidæ</td> + <td>Cyclopygidæ</td> <td rowspan="2"><img src="images/brace_2r.png" width="15" height="38" alt="}" /></td> <td rowspan="2" style="vertical-align:middle"> (nektonic dysphotic)</td> </tr> <tr> - <td>Remopleuridæ</td> + <td>Remopleuridæ</td> </tr> <tr> <td rowspan="3">Benthonic</td> @@ -6092,7 +6052,7 @@ is studied, a logical explanation is readily at hand, for all have free-swimming <tr> <td>Crawlers and slow swimmers</td> <td colspan="2"></td> - <td colspan="4">Trilnuceidæ, Harpedidæ, some Mesonacidæ, etc.</td> + <td colspan="4">Trilnuceidæ, Harpedidæ, some Mesonacidæ, etc.</td> </tr> </table> @@ -6108,10 +6068,10 @@ substances as they were liable to encounter. It having been ascertained that the glabella and axial lobe furnishes an indication of the degree of development of the alimentary canal it is possible to infer something of the kind of food used by various trilobites.</p> -<p>The narrow glabellæ and axial lobes of the oldest trilobites would seem to indicate a -carnivorous habit, while the swollen glabellæ and wider lobes of later ones probably denote an +<p>The narrow glabellæ and axial lobes of the oldest trilobites would seem to indicate a +carnivorous habit, while the swollen glabellæ and wider lobes of later ones probably denote an adaptation to a mixed or even a vegetable diet. This can not be relied upon too strictly, -of course, for the swollen glabellæ of such genera as Deiphon or Sphærexochus may be due +of course, for the swollen glabellæ of such genera as Deiphon or Sphærexochus may be due merely to the shortening up of the cephalon.</p> <p>Walcott (1918, p. 125) suggests that the trilobites lived largely upon worms and conceives @@ -6125,7 +6085,7 @@ handicaps of the trilobite as a procurer of live animal food, and coupled with t slow means of locomotion, almost compel the conclusion that errant animals of any size were fairly safe from it. This restricts the range of animal food to small inactive creatures and the remains of such larger forms as died from natural causes. The modern -Crustacea are effective scavengers, and it is probable that their early Palæozoic ancestors +Crustacea are effective scavengers, and it is probable that their early Palæozoic ancestors were equally so. It is a common saying that in the present stressful stage of the world's history, very few wild animals die a natural death. In Cambrian times, competition for <span class="pagenum"><a name="Page_104" id="Page_104">[104]</a></span> @@ -6229,10 +6189,10 @@ group in that class. The chief interest at present lies in their relation to the allied groups, and to the crustacean ancestor.</p> <p>Trilobites have been most often compared with Branchiopoda, Isopoda, and Merostomata, -the present concensus of opinion inclining toward the notostracan branchiopods (Apodidæ +the present concensus of opinion inclining toward the notostracan branchiopods (Apodidæ in particular) as the most closely allied forms. It seems hardly worth while to burden these pages with a history of opinion on this subject, since it was not until the appendages -were fully made out, from 1881 to 1895, that zoologists and palæontologists were in a +were fully made out, from 1881 to 1895, that zoologists and palæontologists were in a position to give an intelligent judgment. The present status is due chiefly to Bernard (1894), Beecher (1897, 1900, et seq.), and Walcott (1912, et seq.).</p> @@ -6272,7 +6232,7 @@ differences are obvious.</p> BRANCHIOPODA.</p> <p>The early idea that the trilobites were closely related to the Branchiopoda was rejuvenated -by the work of Bernard on the Apodidæ (1892) and has since received the support +by the work of Bernard on the Apodidæ (1892) and has since received the support <span class="pagenum"><a name="Page_107" id="Page_107">[107]</a></span> of most writers on the subject. Fundamentally, a great deal of the argument seems to be that <i>Apus</i> lies the nearest of any modern representative of the class to the theoretical crustacean @@ -6285,7 +6245,7 @@ to be close to the parent stem.</p> and the trilobites, and it is only in the Notostraca, with their sessile eyes and depressed form, that any comparison can be made. The chief way in which modern Branchiopoda and Trilobita agree is that both have a variable number of segments in the body, -that number becoming very large in <i>Apus</i> on the one hand and <i>Mesonacis</i> and <i>Pædeumias</i> +that number becoming very large in <i>Apus</i> on the one hand and <i>Mesonacis</i> and <i>Pædeumias</i> on the other. In neither are the appendages, except those about the mouth, grouped in tagmata. Other likenesses are: the Branchiopoda are the only Crustacea, other than Trilobita, in which gnathobases are found on limbs far removed from the mouth; the trunk limbs @@ -6298,14 +6258,14 @@ than the likenesses.</p> <p>In the Branchiopoda, the antennules are either not segmented or only obscurely so. In trilobites they are richly segmented.</p> -<p>In Branchiopoda, the antennæ are variable. In the Notostraca they are vestigial, while +<p>In Branchiopoda, the antennæ are variable. In the Notostraca they are vestigial, while in the males of the Anostraca they are powerful and often complexly developed claspers. Either condition might develop from the generalized biramous antennas of Trilobita, but the present evidence indicates a tendency toward obsolescence. Claus' observations indicate -that the antennæ of the Anostraca are developments of the exopodites, rather than of the +that the antennæ of the Anostraca are developments of the exopodites, rather than of the endopodites.</p> -<p>The mandibles and maxillæ of the Branchiopoda are greatly reduced, and grouped +<p>The mandibles and maxillæ of the Branchiopoda are greatly reduced, and grouped closely about the mouth. Only the coxopodites of the Trilobita are modified as oral appendages.</p> <p>The trunk limbs of <i>Apus</i> are supposed to be the most primitive among the Branchiopoda, @@ -6346,9 +6306,9 @@ Walcott from the Middle Cambrian, and invites comparison with <i>Apus</i>. The c long, loosely attached to the body, and extends over the greater part of the thorax. The eyes are small, sessile, and close to the anterior margin.</p> -<p>The appendages of the head consist of two pairs of antennæ, and three pairs of slender, -jointed legs. Both pairs of antennæ are slender and many-jointed, the antennules somewhat -smaller than the antennæ. The exact structure of the limbs about the mouth has not +<p>The appendages of the head consist of two pairs of antennæ, and three pairs of slender, +jointed legs. Both pairs of antennæ are slender and many-jointed, the antennules somewhat +smaller than the antennæ. The exact structure of the limbs about the mouth has not yet been made out, but they are slender, tapering, endopodite-like legs, with at least three or four segments in each, and probably more.</p> @@ -6362,7 +6322,7 @@ represent the gills." They are not figured, but taken in connection with the end appearance of the segmented limbs, one would expect them to be vestigial exopodites.</p> <p>A small hypostoma is present on the ventral side, and several of the specimens show -wonderfully well the form of the alimentary canal and the hepatic cæca. The main branches +wonderfully well the form of the alimentary canal and the hepatic cæca. The main branches of the latter enter the mesenteron just behind the fifth pair of cephalic appendages.</p> <p>Behind the thorax the abdomen is long, limbless, and tapers to a point. It is said to @@ -6476,26 +6436,26 @@ Middle Cambrian.</p> <p>The non-parasitic Eucopepoda are in many ways much nearer to the trilobites than any other Crustacea. These little animals lack the carapace, and the body is short, with typically -ten free segments and a telson bearing caudal furcæ. The head is composed of five +ten free segments and a telson bearing caudal furcæ. The head is composed of five segments (if the first thoracic segment is really the fused first and second), is often flattened, and lacks compound eyes. Pleural lobes are well developed, but instead of being flattened as in the trilobite, they are turned down at the sides or even incurved. A labrum is present.</p> -<p>The antennules, antennæ, and mandibles are quite like those of trilobites. The antennules -are very long and made up of numerous segments. The antennæ are biramous, the +<p>The antennules, antennæ, and mandibles are quite like those of trilobites. The antennules +are very long and made up of numerous segments. The antennæ are biramous, the junction between the coxopodite and basipodite is well marked, and the endopodite consists of only two segments.</p> <p>The mandibles are said to "retain more completely than in any other Crustacea the form of biramous swimming limbs which they possess in the nauplius." The coxopodites -form jaws, while both the reduced endopodite and exopodite are furnished with long setæ. -The maxillulæ are also biramous, but very different in form from those of the trilobite, -and the maxillæ are phyllopodan.</p> +form jaws, while both the reduced endopodite and exopodite are furnished with long setæ. +The maxillulæ are also biramous, but very different in form from those of the trilobite, +and the maxillæ are phyllopodan.</p> -<p>The first thoracic limb is uniramous and similar to the maxillæ, but the five following +<p>The first thoracic limb is uniramous and similar to the maxillæ, but the five following pairs are biramous swimming legs with coxopodite, basipodite, exopodite, and endopodite. -Both the exopodite and endopodite are shorter than in the trilobites, but bear setæ and spines.</p> +Both the exopodite and endopodite are shorter than in the trilobites, but bear setæ and spines.</p> <p>The last pair of thoracic limbs are usually modified in the male into copulatory organs. In some females they are enlarged to form plates for the protection of the eggs, in others @@ -6514,8 +6474,8 @@ water. Most free-living forms are minute, and all have thin tests.</p> <p><span class="pagenum"><a name="Page_111" id="Page_111">[111]</a></span></p> -<p>The eyes of copepods are of interest, in that they suggest the paired ocelli of the Harpedidæ -and Trinucleidæ. In the Copepoda there are, in the simplest and typical form of +<p>The eyes of copepods are of interest, in that they suggest the paired ocelli of the Harpedidæ +and Trinucleidæ. In the Copepoda there are, in the simplest and typical form of these organs, three ocelli, each supplied with its own nerve from the brain. Two of these are dorsal and look upward, while the third is ventral. In some forms the dorsal ocelli are doubled, so that five in all are present (cf. some species of Harpes with three ocelli on @@ -6549,8 +6509,8 @@ or stylets on the last segment.</p> must have presented great difficulty in their interpretation. A pair of antennules appear to spring from near the front of the lower surface, and the remainder of the organs are grouped about the mouth, which is on the median line back of the center. Handlirsch sees in these -somewhat obscure appendages four pairs of biramous limbs, antennæ, mandibles, maxillulæ, -and maxillæ, both branches of each consisting of short similar segments, endopodites and +somewhat obscure appendages four pairs of biramous limbs, antennæ, mandibles, maxillulæ, +and maxillæ, both branches of each consisting of short similar segments, endopodites and exopodites being alike pediform.</p> <p>Each segment of the thorax has a pair of appendages, and those on the first two are @@ -6620,7 +6580,7 @@ are present in one family.</p> <p>The antennules are short and much modified by functioning as swimming, creeping, or digging organs. They consist of eight or less segments. The antennas are also locomotor organs, and in most orders are biramous. The mandibles are biramous and usually with, -but sometimes without, a gnathobase. The maxillulæ are likewise biramous but much +but sometimes without, a gnathobase. The maxillulæ are likewise biramous but much modified.</p> <p>The homology of the third post-oral limb is in question, some considering it a maxilla @@ -6631,7 +6591,7 @@ fourth post-oral limb is a lobed plate, usually not distinctly segmented, and th pediform leg. The sixth, if present at all, is vestigial.</p> <p>Very little comparison can be made between the Ostracoda and Trilobita, other than -in the ground-plan of the limbs, but the presence of biramous antennæ is a primitive +in the ground-plan of the limbs, but the presence of biramous antennæ is a primitive characteristic.</p> @@ -6639,12 +6599,12 @@ characteristic.</p> <p>Like the ostracod, the adult cirriped bears little external resemblance to the trilobite. The form of the nauplius is somewhat peculiar, but it has the typical three pairs of appendages, -to which are added in the later metanauplius stages the maxillæ and six pairs of +to which are added in the later metanauplius stages the maxillæ and six pairs of thoracic appendages. In the adult, the antennules, which serve for attachment of the larva, usually persist in a functionless condition, while the antennas disappear. The mandibles, -maxillulæ, and maxillæ are simple and much modified to form mouth parts, and the six +maxillulæ, and maxillæ are simple and much modified to form mouth parts, and the six pairs of thoracic appendages are developed into long, multisegmented, biramous appendages -bearing numerous setæ which serve for catching prey. Paired eyes are present in later +bearing numerous setæ which serve for catching prey. Paired eyes are present in later metanauplius stages, but lost early in the development. The relationship to the trilobite evidently is not close.</p> @@ -6655,12 +6615,12 @@ is not close.</p> <i>1. Phyllocarida.</i></p> <p>The oldest malacostracans whose appendages are known are species of <i>Hymenocaris</i>. -One, described as long ago as 1866 by Salter, has what seem to be a pair of antennæ +One, described as long ago as 1866 by Salter, has what seem to be a pair of antennæ and a pair of jaw-like mouth-parts. Another more completely known species has recently been reported by Walcott (1912 A, p. 183, pl. 31, figs. 1-6). This latter form is described as having five pairs of cephalic appendages: a pair of minute antennules beside the small -pedunculated eyes, a pair of large uniramous antennæ, slender mandibles and maxillulæ, -and large maxillæ composed of short stout segments. There are eight pairs of biramous +pedunculated eyes, a pair of large uniramous antennæ, slender mandibles and maxillulæ, +and large maxillæ composed of short stout segments. There are eight pairs of biramous thoracic limbs, the exopodites setiferous, the endopodites composed of short wide segments and ending in terminal claw-like spines. These appendages are like those of trilobites.</p> @@ -6671,28 +6631,28 @@ present living. The general form of the recent and fossil representatives of the strikingly similar. The chief outward difference is that in many of the fossils the telson is accompanied by two furcal rami, while in the modern genera it is simple. It now becomes possible to make some comparison between the appendages of <i>Hymcnocaris</i> of the -Middle Cambrian and the Nebaliidæ of modern seas.</p> +Middle Cambrian and the Nebaliidæ of modern seas.</p> <p>In both there are five pairs of cephalic and eight of thoracic appendages, while those of the abdomen of Hymenocaris are not known.</p> -<p>In both, the antennules are less developed than the antennæ. In the Nebaliidæ the +<p>In both, the antennules are less developed than the antennæ. In the Nebaliidæ the antennules show evidence of having been originally double (they are obviously so in the -embryo), while they are single in <i>Hymcnocaris</i>. In both, the antennæ are simple. The +embryo), while they are single in <i>Hymcnocaris</i>. In both, the antennæ are simple. The remaining cephalic organs are too little shown by the specimen from the Middle Cambrian -to allow detailed comparison. The mandibles, maxillulæ, and maxillæ of <i>Nebalia</i> are, however, +to allow detailed comparison. The mandibles, maxillulæ, and maxillæ of <i>Nebalia</i> are, however, of types which could be derived from the trilobite.</p> <p><span class="pagenum"><a name="Page_114" id="Page_114">[114]</a></span></p> -<p>In three of the genera of the Nebaliidæ, the eight pairs of thoracic limbs are all similar +<p>In three of the genera of the Nebaliidæ, the eight pairs of thoracic limbs are all similar to one another, though those of the genera differ. All are biramous. The limbs of <i>Hymcnocaris</i> can apparently be most closely correlated with those of <i>Nebalia antarctica</i>, in which the endopodite consists of short flattened segments, and the exopodite is a long setiferous plate. Epipodites are present in both <i>Nebalia</i> and <i>Hymcnocaris</i>.</p> <p>So far as the appendages of <i>Hymenocaris</i> are known, they agree very well with those -of the Nebaliidæ, and since they are of the trilobite type, it may safely be stated that the +of the Nebaliidæ, and since they are of the trilobite type, it may safely be stated that the Trilobita and Malacostraca are closely related.</p> <p class="section"><a name="Syncarida" id="Syncarida"></a> @@ -6709,7 +6669,7 @@ and the antennules double as in most of the Malacostraca. External epipodites ar very numerous on the anterior limbs.</p> <p>This group extends back as far as the Pennsylvanian and had then probably already -become adapted to fresh-water life. It may be significant that the Palæozoic syncarids +become adapted to fresh-water life. It may be significant that the Palæozoic syncarids appear to have lacked epipodites. While differing very considerably from the Trilobita, the Syncarida could have been derived from them.</p> @@ -6744,7 +6704,7 @@ had been given up.</p> <p><span class="pagenum"><a name="Page_115" id="Page_115">[115]</a></span></p> -<p>In Isopoda the antennæ are practically uniramous sensory organs. The second cephalic +<p>In Isopoda the antennæ are practically uniramous sensory organs. The second cephalic appendages of trilobites are capable of such development through reduction of the exopodite.</p> <p>In the Isopoda the coxopodites are usually fused with the body, remaining as free, @@ -6764,7 +6724,7 @@ Irish Acad., vol. 27, sect. B, 1908, p. 63, fig. 1), found in the Upper Devonian Kilkenny, Ireland. The appendages are not known, but the test is in some ways like that of a trilobite. The thorax, abdomen, and pygidium are especially like those of certain trilobites, and there is no greater differentiation between thorax and abdomen than there is between -the regions before and behind the fifteenth segment of a <i>Pædeumias</i> or <i>Mesonacis</i>. +the regions before and behind the fifteenth segment of a <i>Pædeumias</i> or <i>Mesonacis</i>. The anal segment is directly comparable to the pygidium of a <i>Ceraurus</i>, the stiff unsegmented uropods being like the great lateral spines of that genus.</p> @@ -6793,21 +6753,21 @@ it has been aptly compared to a trilobite. The great nuchal and genal spines and marginal sessile eyes, coupled with the almost total lack of thoracic and abdominal test, give it a bizarre appearance which may obscure its real relationships.</p> -<p>The cephalon appears to bear five pairs of appendages, antennules, and antennæ, both -tactile organs with numerous short segments, mandibles, and first and second maxillæ. The +<p>The cephalon appears to bear five pairs of appendages, antennules, and antennæ, both +tactile organs with numerous short segments, mandibles, and first and second maxillæ. The last three pairs are elongate, very spinose limbs, of peculiar appearance. They seem to have seven segments, but are not well preserved. These organs are attached near the posterior end of the labrum.</p> <p>There are twenty-four pairs of biramous thoracic appendages, which lack endobases. The endopodites are long and slender, with numerous spines; the exopodites have narrow, -thin shafts, with long, forward pointed setæ. The anal segment consists of a single plate.</p> +thin shafts, with long, forward pointed setæ. The anal segment consists of a single plate.</p> <p><span class="pagenum"><a name="Page_116" id="Page_116">[116]</a></span></p> <p>Further information about this fossil will be eagerly awaited. None of the illustrations so far published shows biramous appendages on the cephalon. This, coupled with the -presence of tactile antennæ, makes its reference to the Trilobita impossible, but the +presence of tactile antennæ, makes its reference to the Trilobita impossible, but the present interpretation indicates that it was closely allied to them.</p> <div class="fig_center" style="width:469px"> @@ -6817,7 +6777,7 @@ present interpretation indicates that it was closely allied to them.</p> photographs and descriptions published by Walcott. Although all the limbs of the trunk appear to be biramous, only endopodites are placed on one side and exopodites on the other, for the sake of greater clearness in the illustration. Drawn by Doctor Elvira Wood, under -the supervision of the writer. × about 6.</p> +the supervision of the writer. × about 6.</p> </div> @@ -6846,7 +6806,7 @@ of the Merostomata are so obviously trilobite-like that it would seem that their could easily be proved. The task has not yet been satisfactorily accomplished, however, and new information seems only to add to the difficulties.</p> -<p>So far as I know, the Araneæ have not previously been compared directly with trilobites, +<p>So far as I know, the Araneæ have not previously been compared directly with trilobites, although such treatment consists merely in calling attention to their crustacean affinities, as has often been done.</p> @@ -6874,7 +6834,7 @@ near the ancestral stock of the whole crustacean class.</p></div> <p>While no one having any real knowledge of the Trilobita has adopted Lankester's scheme of the inclusion of the group as the primitive grade in the Arachnida, reference to it may -not be amiss. This theory is best set forth in the Encyclopædia Britannica, Eleventh +not be amiss. This theory is best set forth in the Encyclopædia Britannica, Eleventh Edition, under the article on Arachnida. It is there pointed out that the primitive arachnid, like the primitive crustacean, should be an animal without a fixed number of somites, and without definitely grouped tagmata. As Lankester words it, they should be anomomeristic @@ -6909,8 +6869,8 @@ has lateral pleural spines.</p> Arachnida; if two, Crustacea. This is based on the idea that in the course of evolution of the Arthropoda, the mouth has shifted backward from a terminal position, and that as a pair of appendages is passed, they lose their function as mouth-parts and eventually become -simple tactile organs. Thus arise the cheliceræ of most arachnids, and the two pairs of -tactile antennæ of most Crustacea. This theory is excellent, and the rule holds well for +simple tactile organs. Thus arise the cheliceræ of most arachnids, and the two pairs of +tactile antennæ of most Crustacea. This theory is excellent, and the rule holds well for modern forms, but as shown by the varying length of the hypostoma in different trilobites, the position of the mouth had not become fixed in that group. In some trilobites, like <i>Triarthrus</i>, the gnathobases of the second pair of appendages still function, but in all, so far as @@ -6919,7 +6879,7 @@ and in some at least, back of the points of attachment of four pairs. As pointed case of <i>Calymene</i> and <i>Ceraurus</i>, the trilobites show a tendency toward the degeneration of the first and second pairs of biramous appendages, particularly of the gnathobases. They are in just that stage of the backward movement of the mouth when the function of the -antennæ as mandibles has not yet been lost. If the presence of functional gnathobases back +antennæ as mandibles has not yet been lost. If the presence of functional gnathobases back of the mouth, rather than the points of attachment in front of the mouth, is to be the guide, then Triarthrus might be classed as an arachnid and <i>Calymene</i> and <i>Isotelus</i> as crustaceans. In other words, the rule breaks down in this primitive group.</p> @@ -7033,7 +6993,7 @@ fig. 10), and that they were present along the body is shown by figure 2, plate <p>The present state of knowledge of both these peculiar animals leaves much to be desired. The indications are that the cephalic appendages are not biramous, and that only one pair of -antennæ, the first, are developed as tactile organs. The thoracic appendages of <i>Emeraldella</i> +antennæ, the first, are developed as tactile organs. The thoracic appendages of <i>Emeraldella</i> are biramous, and also possibly those of <i>Sidneyia</i>. In the latter, the last two abdominal segments seem to have been without appendages, while in <i>Emeraldella</i> at least one branch of each appendage, and possibly both, is retained.</p> @@ -7076,13 +7036,13 @@ the presence of five pairs of appendages on the cephalon and trilobitic legs on <b>Molaria</b> and <b>Habelia.</b></p> <p>Other so called Merostomata found by Walcott in the Middle Cambrian are the genera -<i>Molaria</i> and <i>Habelia</i>, both referred to the Cambrian family Aglaspidæ. These genera seem +<i>Molaria</i> and <i>Habelia</i>, both referred to the Cambrian family Aglaspidæ. These genera seem to conform with <i>Aglaspis</i> of the Upper Cambrian in having a trilobite-like cephalon without <span class="pagenum"><a name="Page_121" id="Page_121">[121]</a></span> facial sutures, a trilobite-like thorax of a small but variable (7-12) number of segments, and a <i>Limulus</i>-like telson. Neither of them has yet been fully described or figured, but (Walcott 1912 A, p. 202) <i>Habelia</i> appears to have five pairs of cephalic appendages, the -first two pairs of which are multisegmented antennæ. The thoracic appendages are likewise +first two pairs of which are multisegmented antennæ. The thoracic appendages are likewise none too well known, but they appear to have been biramous. The endopodites are better preserved than the exopodites, but in at least one specimen of <i>Molaria</i> the exopodites are conspicuous.</p> @@ -7090,28 +7050,28 @@ conspicuous.</p> <p>If these genera are properly described and figured, their appendages are typically crustacean, and fundamentally in agreement with those of <i>Marrella</i>. The relation to the Trilobita is evidently close, the principal differences being the absence of facial sutures and the -presence of true antennæ. I am therefore transferring the Aglaspidæ from the Merostomata +presence of true antennæ. I am therefore transferring the Aglaspidæ from the Merostomata to a new subclass under the Crustacea.</p> -<p class="caption3"><a name="ARANEAE" id="ARANEAE"></a>ARANEÆ.</p> +<p class="caption3"><a name="ARANEAE" id="ARANEAE"></a>ARANEÆ.</p> <p>The spiders have the head and thorax fused, the abdomen unsegmented except in the most primitive suborder, and so appear even less trilobite-like than the insects. The appendages likewise are highly specialized. The cephalothorax bears six pairs of appendages, -the first of which are the pre-oral cheliceræ, while behind the mouth are the pedipalpi and +the first of which are the pre-oral cheliceræ, while behind the mouth are the pedipalpi and four pairs of ambulatory legs. The posterior pairs of walking legs belong to the thorax, -but the anterior ones are to be homologized with the maxillæ of Crustacea, so that the spiders +but the anterior ones are to be homologized with the maxillæ of Crustacea, so that the spiders are like the trilobites in having functional walking legs on the head.</p> <p>The chief likenesses are, however, seen in the very young. On the germ band there -appear a pair of buds in front of the rudiments of the cheliceræ which later unite to form -the rostrum of the adult. At the time these buds appear, the cheliceræ are post-oral, but -afterward move forward so that both rostrum and cheliceræ are in front of the mouth. -The rostrum is therefore the product of the union of the antennules, and the cheliceræ are -to be homologized with the antennæ. There seems to be some doubt about the homology +appear a pair of buds in front of the rudiments of the cheliceræ which later unite to form +the rostrum of the adult. At the time these buds appear, the cheliceræ are post-oral, but +afterward move forward so that both rostrum and cheliceræ are in front of the mouth. +The rostrum is therefore the product of the union of the antennules, and the cheliceræ are +to be homologized with the antennæ. There seems to be some doubt about the homology of the pedipalps with the mandibles, as at least one investigator claims to have found rudiments -of a segment between the one bearing the cheliceræ and that with the pedipalps.</p> +of a segment between the one bearing the cheliceræ and that with the pedipalps.</p> <p>Jaworowski (Zool. Anzeiger, 1891, p. 173, fig. 4) has figured the pedipalp from the germ band of <i>Trochosa singoriensis</i>, and called attention to the fact that it consists of a coxopodite @@ -7132,12 +7092,12 @@ species studied. This of course suggests connection with the anomomeristic trilo <p>The oldest true spiders are found in the Pennsylvanian, and several genera are now known. The head and thorax are fused completely, but the abdomen is distinctly segmented. <span class="pagenum"><a name="Page_122" id="Page_122">[122]</a></span> -Some of the Anthracomarti resemble the trilobites more closely than do the Araneæ, +Some of the Anthracomarti resemble the trilobites more closely than do the Araneæ, as they lack the constriction between the cephalothorax and abdomen. The spiders of the -Pennsylvanian have this constriction less perfectly developed than do modern Araneæ, and +Pennsylvanian have this constriction less perfectly developed than do modern Araneæ, and occupy an intermediate position in this respect. In the Anthracomarti, the pedipalpi are simple, pediform, and all the appendages have very much the appearance of the coxopodites -and endopodites of trilobites. Cheliceræ are not known, and pleural lobes are well developed +and endopodites of trilobites. Cheliceræ are not known, and pleural lobes are well developed in this group. Anthracomarti have not yet been found in strata older than the Pennsylvanian, but they seem to be to a certain extent intermediate between true spiders and the marine arachnid.</p> @@ -7160,23 +7120,23 @@ theory begins to seem more possible.</p> <p>Handlirsch really presented very little specific evidence in favor of his theory. In fact, one gets the impression that he has insisted on only two points. Firstly, that the most -ancient known insects, the Palæodictyoptera, were amphibious, and their larvæ, which lived -in water, were very like the adult. Secondly, that the wings of the Palæodictyoptera probably +ancient known insects, the Palæodictyoptera, were amphibious, and their larvæ, which lived +in water, were very like the adult. Secondly, that the wings of the Palæodictyoptera probably worked vertically only, and the two main wings were homologous with rudimentary wing-like outgrowths on each segment of the body. These outgrowths have the appearance of, and might have been derived from, the pleural lobes of trilobites.</p> -<p>He figured (1908, p. 1305, fig. 7) a reconstructed larva of a palæodictyopterid as +<p>He figured (1908, p. 1305, fig. 7) a reconstructed larva of a palæodictyopterid as having biramous limbs on each segment, but so far as I can find, this figure is purely schematic, for there seems to be no illustration or description of any such larva in the body of his work.</p> <p>That the insects arose directly from aquatic animals is of course possible, and Handlirsch's first argument has considerable force. It may, however, be purely a chance that the -oldest insects now known to us happen to be an amphibious tribe. The Palæodictyoptera +oldest insects now known to us happen to be an amphibious tribe. The Palæodictyoptera are not yet known to antedate the Pennsylvanian, but there can be no doubt that, insects existed long before that time, and the fact that their remains have not been found is good evidence that the pre-Pennsylvanian insects were not aquatic. Comstock, who has recently -investigated the matter, does not believe that the Palæodictyoptera were amphibious (The +investigated the matter, does not believe that the Palæodictyoptera were amphibious (The Wings of Insects, Ithaca, N. Y., 1918, p. 91).</p> <p>The second argument, that wings arose from the pleural lobes of trilobites, is exceedingly @@ -7200,7 +7160,7 @@ is an animal more easily derived from the Chilopoda than from the Trilobita. Fiv appendages are present on the head, and the trunk is made up of fourteen similar segments, each with a pair of walking limbs and a pair of spiracles.</p> -<p>Only the maxillæ and maxillulæ are represented as biramous. If the ancestor of the +<p>Only the maxillæ and maxillulæ are represented as biramous. If the ancestor of the Insecta was, as seems possible, tracheate, this fact alone would rule out the trilobites. Among tracheates, the Chilopoda are certainly more closely allied to the Insecta than are any other wingless forms. If the ancestors of the insects were not actually chilopods, they @@ -7209,7 +7169,7 @@ same stock.</p> <p>As to the ancestry of the Chilopoda, it is probable that they had the same origin as the other Arthropoda. Tothill has pointed out that in the embryo of some chilopods there -are rudiments of two pairs of antennæ and that the two pairs of maxillæ and the maxillipeds +are rudiments of two pairs of antennæ and that the two pairs of maxillæ and the maxillipeds are biramous. This would point rather to the Haplopoda than directly to the trilobites as possible ancestors, and may explain why the former vanish so suddenly from the geological record after their brief appearance in the Middle Cambrian. They may have gone on to @@ -7218,7 +7178,7 @@ the land.</p> <p>There seem to be no insuperable obstacles to prevent the derivation, indirectly, of the insects from some trilobite with numerous free segments, and small pygidium. The antennules and pleural lobes must be lost, the antennas and trunk limbs modified by loss of exopodites. -Wings and tracheæ must be acquired.</p> +Wings and tracheæ must be acquired.</p> <p>Handlirsch places the date of origin of the Insecta rather late, just at the end of the Devonian and during the "Carboniferous." By that time most families of trilobites had @@ -7233,17 +7193,17 @@ in the Cambrian.</p> <p>The adult chilopod lacks the antennules, and all of the other appendages, with the exception -of the maxillulæ, are uniramous. The walking legs are similar to the endopodites +of the maxillulæ, are uniramous. The walking legs are similar to the endopodites of trilobites, and usually have six or seven segments. The appendages are therefore such as could be derived by modification of those of trilobites by the almost complete loss of the exopodites and shortening of the endopodites of the head. The position of the post-oral appendages, the posterior ones outside those closest the mouth, is perhaps foreshadowed in the arrangement of those of Triarthrus.</p> -<p>The Chilopoda differ from the Hexapoda in developing the antennæ instead of the +<p>The Chilopoda differ from the Hexapoda in developing the antennæ instead of the antennules as tactile organs, but this can not be used with any great effect as an argument that the latter did not arise from the ancestors of the former, since it is entirely possible -that in early Palæozoic times the pre-Chilopoda possessed two pairs of antennæ. The first +that in early Palæozoic times the pre-Chilopoda possessed two pairs of antennæ. The first pair are still recognizable in the embryo of certain species.</p> <p><span class="pagenum"><a name="Page_124" id="Page_124">[124]</a></span></p> @@ -7265,8 +7225,8 @@ general appearance somewhat like that of a trilobite, but on closer examination are seen. The most striking single feature of the group, the possession by each segment of two pairs of appendages, is not in any way foreshadowed in the trilobites, none of which shows any tendency toward a fusion of pairs of adjacent segments. The antennules -are short, antennæ absent, mandibles and maxillulæ much modified, the latter possibly -biramous, and the maxillæ absent. The trunk appendages are very similar to those of chilopods, +are short, antennæ absent, mandibles and maxillulæ much modified, the latter possibly +biramous, and the maxillæ absent. The trunk appendages are very similar to those of chilopods, and could readily be derived from the endopodites of trilobites.</p> <p>The oldest diplopods are found in the Silurian (Ludlow) and Devonian (Lower Old @@ -7274,7 +7234,7 @@ Red) of Scotland, and three species belonging to two genera are known. The oldes <i>Archidesmus loganensis</i> Peach (1889, p. 123, pl. 4, fig. 4), and the Devonian species are <i>Archidesmus macnicoli</i> Peach and <i>Kampecaris forfarensis</i> Page (Peach 1882, p. 182, pl. 2, fig. 2, 2a, and p. 179, pl. 2, figs. 1-1g). All of these species show lateral expansions like -the recent Polydesmidæ, and these of course suggest the pleural lobes of trilobites. All +the recent Polydesmidæ, and these of course suggest the pleural lobes of trilobites. All three of the species are simpler than any modern diplopod, for there is only a single pair of appendages on each segment. No <i>foramina repugnatoria</i> were observed, and the eyes of <i>Kampecaris forfarensis</i> as described are singularly like those of a phacopid.</p> @@ -7294,7 +7254,7 @@ be vestiges of these structures.</p> the distal end. The distal one bears one or two minute spines. They are most readily compared with the endopodites of <i>Isotelus</i>. The resemblance is, in fact, rather close. The sternal plates are wider and the limbs of opposite sides further apart than in modern diplopods. -Except for one pair of antennæ, no cephalic appendages are preserved.</p> +Except for one pair of antennæ, no cephalic appendages are preserved.</p> <p>While these specimens do not serve to connect the Diplopoda with the Trilobita, they do show that most of the specializations of the former originated since Lower Devonian @@ -7332,21 +7292,21 @@ even unrelated groups.</p> <p>The chief objections to the derivation of the remainder of the Crustacea from the trilobites have been: first, that the trilobites had broad pleural extensions; second, that they had -a large pygidium; and lastly, that they had only one pair of tactile antennæ.</p> +a large pygidium; and lastly, that they had only one pair of tactile antennæ.</p> <p>It has now been pointed out that many modern Crustacea have pleural extensions, but that they usually bend down at the sides of the body, and also that in the trilobites and more especially in <i>Marrella</i>, there was a tendency toward the degeneration of the pleural lobes. -A glance at the Mesonacidæ or Paradoxidæ should be convincing proof that in some trilobites +A glance at the Mesonacidæ or Paradoxidæ should be convincing proof that in some trilobites the pygidium is reduced to a very small plate.</p> -<p>In regard to the second antennæ standard text-books contain statements which are actually -surprising. A compilation shows that the antennæ are entirely uniramous in but a +<p>In regard to the second antennæ standard text-books contain statements which are actually +surprising. A compilation shows that the antennæ are entirely uniramous in but a very few suborders, chiefly among the Malacostraca; that they are biramous with both exopodite and endopodite well developed in most Copepoda, Ostracoda, and Branchiopoda; and that the exopodite, although reduced in size, still has a function in some suborders of the Malacostraca. The Crustacea could not possibly be derived from an ancestor with two -pairs of uniramous antennæ.</p> +pairs of uniramous antennæ.</p> <p>Although I have defended the trilobites, perhaps with some warmth, from the imputation that they were Arachnida, my argument does not apply in the opposite direction, and @@ -7383,7 +7343,7 @@ at the junction with the coxopodite.</p> <p>In all trilobites the endopodite consists of six segments, and the coxopodite of a single segment the inner end of which is prolonged as an endobase. There does not seem to be any variation from this plan in the subclass, although individual segments are variously -modified. The exopodites are more variable, but all consist of a flattened shaft with setæ on +modified. The exopodites are more variable, but all consist of a flattened shaft with setæ on one margin. No other organs such as accessory gills, swimming plates, or brood pouches have yet been found attached to the appendages, the evidence for the existence of the various epipodites and exites described by Walcott being unsatisfactory (see p. 23).</p> @@ -7402,12 +7362,12 @@ are modifications of a limb which is fundamentally biramous. In most species, bo and endopodite suffer reduction. The exopodite springs from the basipodite and that segment is closely joined to the coxopodite, producing a protopodite. In some cases the original segments of the endopodites fuse to form a stiff rod. While highly diversified, -these appendages are very trilobite-like, and some Ostracoda even have biramous antennæ.</p> +these appendages are very trilobite-like, and some Ostracoda even have biramous antennæ.</p> <p>The non-parasitic Copepoda have limbs exceedingly like those of trilobites. Many of them are biramous, the endopodites sometimes retaining the primitive six segments. Coxopodite and basipodite are generally united, and endopodite and exopodite variously modified. -Like some of the Ostracoda, the more primitive Copepoda have biramous antennæ.</p> +Like some of the Ostracoda, the more primitive Copepoda have biramous antennæ.</p> <p>As would be expected, the appendages of the Cirripedia are much modified, although those of the nauplius are typical. The thoracic appendages of many are biramous, but both @@ -7461,16 +7421,16 @@ between them and <i>Apus</i>.</p> of the rather complex phyllopodan type is another case in which the theory of "recapitulation" has proved to hold. It had already been observed that in ontogeny the biramous limb preceded the phyllopodan, but so strong has been the belief in the primitive character -of the Apodidæ that the obvious suggestion has been ignored. Even in such highly specialized +of the Apodidæ that the obvious suggestion has been ignored. Even in such highly specialized Malacostraca as the hermit crabs the development of certain of the limbs illustrates the change from the schizopodal to the phyllopodan type, and Thompson (Proc. Boston Soc. Nat. Hist., vol. 31, 1903, pl. 5, fig. 12) has published an especially good series of drawings <span class="pagenum"><a name="Page_128" id="Page_128">[128]</a></span> -showing the first maxilliped. In the first to fourth zoeæ the limb is biramous but in the +showing the first maxilliped. In the first to fourth zoeæ the limb is biramous but in the glaucothoe a pair of broad processes grow out from the protopodite, while the exopodite and particularly the endopodite become greatly reduced. In the adult the endopodite is a mere vestige, while the flat outgrowths from the protopodite have become very large and bear -setæ.</p> +setæ.</p> <p class="section"><a id="Summary128"></a> <i>Summary.</i></p> @@ -7513,7 +7473,7 @@ number of thoracic segments, and a few examples can be cited in which there is v within a species, or at least in very closely related species.</p> <p>Carpenter (1903, p. 333) has tabulated the number of trunk segments of such trilobites -as were listed by Zittel in 1887 and finds a steady increase throughout the Palæozoic. +as were listed by Zittel in 1887 and finds a steady increase throughout the Palæozoic. His table, which follows, is, however, based upon very few genera.</p> <table summary="Palaeozoic Genera"> @@ -7557,37 +7517,37 @@ are now represented by entire specimens, and since these most ancient genera are importance, a few comments on them may be offered.</p> <p>The total number of segments can be fairly accurately determined in at least nineteen -genera of trilobites from the Lower Cambrian. These include eight genera of the Mesonacidæ +genera of trilobites from the Lower Cambrian. These include eight genera of the Mesonacidæ (<i>Olenellus</i> was excluded) and <i>Eodiscus</i>, <i>Goniodiscus</i>, <i>Protypus</i>, <i>Bathynotus</i>, <i>Atops</i>, <i>Olenopsis</i>, <i>Crepicephalus</i>, <i>Vanuxemella</i>, <i>Corynexochus</i>, <i>Bathyuriscus</i>, and <i>Poliella</i>. The extremes -of range in total segments of the trunk is seen in <i>Eodiscus</i> (9) and <i>Pædeumias</i> +of range in total segments of the trunk is seen in <i>Eodiscus</i> (9) and <i>Pædeumias</i> (45+), and these same genera show the extremes in the number of thoracic segments, -there being 3 in the one and 44+ in the other. <i>Pædeumias</i> probably shows the greatest variation +there being 3 in the one and 44+ in the other. <i>Pædeumias</i> probably shows the greatest variation of any one genus of trilobites, various species showing from 19 to 44+ thoracic segments. The average for the nineteen genera is 13.9 segments in the thorax, 3.7 segments in the pygidium, or a total average of 17.6 segments in the trunk. <i>Crepicephalus</i> with 12-14 segments in the thorax and 4-6 in the pygidium, and <i>Protypus</i>, with 13 in the thorax -and 4-6 in the pygidium, are the only genera which approach the average. All of the Mesonacidæ, +and 4-6 in the pygidium, are the only genera which approach the average. All of the Mesonacidæ, except one, <i>Olenelloides</i>, have far more thoracic and fewer pygidial segments than -the average, while the reverse is true of the Eodiscidæ, <i>Vanuxemella</i>, <i>Corynexochus</i>, <i>Bathyuriscus</i>, +the average, while the reverse is true of the Eodiscidæ, <i>Vanuxemella</i>, <i>Corynexochus</i>, <i>Bathyuriscus</i>, and Poliella.</p> -<p>The eight genera of the Mesonacidæ, <i>Nevadia</i>, <i>Mesonacis</i>, <i>Elliptocephala</i>, <i>Callavia</i>, <i>Holmia</i>, -<i>Wanneria</i>, <i>Pædeumias</i>, and <i>Olenelloides</i>, have an average of 20.25 segments in the thorax +<p>The eight genera of the Mesonacidæ, <i>Nevadia</i>, <i>Mesonacis</i>, <i>Elliptocephala</i>, <i>Callavia</i>, <i>Holmia</i>, +<i>Wanneria</i>, <i>Pædeumias</i>, and <i>Olenelloides</i>, have an average of 20.25 segments in the thorax and 1.5 in the pygidium, a total of 21.75. If, however, the curious little <i>Olenelloides</i> be omitted, the average for the thorax rises to 22.14 and the total to 23.84. <i>Olenelloides</i> is, in fact, very probably the young of an <i>Olenellus</i>. Specimens are only 4.5 to 11 mm. long, and occur in the same strata with <i>Olenellus</i> (see Beecher 1897 A, p. 191).</p> <p>Thirty-three genera from the Middle Cambrian afford data as to the number of segments, -the Agnostidæ being excluded. The extreme of variation there is smaller than +the Agnostidæ being excluded. The extreme of variation there is smaller than in the Lower Cambrian. The number of thoracic segments varies from 2 in Pagetia to 25 in <i>Acrocephalites</i>, and these same genera show the greatest range in total number of trunk segments, 8 and 29 respectively.</p> <p>The average of thoracic segments for the entire thirty-three genera is 10.5, of pygidial segments 5.9, a total average of 16.4. It will be noted that the thorax shows on the average -less and the pygidium more segments than in the Lower Cambrian. If the Agnostidæ could be +less and the pygidium more segments than in the Lower Cambrian. If the Agnostidæ could be included, this result would doubtless be still more striking. Of the genera considered, <i>Asaphiscus</i> with 7-11 thoracic and 5-8 pygidial segments, <i>Blainia</i> with 9 thoracic and 6-11 pygidial, <i>Zacanthoides</i> with 9 thoracic and 5 pygidial, and <i>Anomocare</i> with 11 thoracic and @@ -7601,7 +7561,7 @@ The genera tabulated were <i>Acrocephalites</i>, <i>Alokistocare</i>, <i>Crepice <p>Enough genera of Upper Cambrian trilobites are not known from entire specimens to furnish satisfactory data. Excluding from the list the Proparia recently described by Walcott, the average total trunk segments in ten genera is 18, but as most of the genera are -Olenidæ or olenid-like, not much weight can be attached to these figures.</p> +Olenidæ or olenid-like, not much weight can be attached to these figures.</p> <p>For the Cambrian as a whole, the average for sixty-two genera is between 17 and 18 trunk segments, which is surprisingly like the result obtained by Carpenter from only twelve @@ -7635,7 +7595,7 @@ species of <i>Ampyx</i> being the only one I have happened to notice. <i>Calymen <i>Asaphus</i>, <i>Ogygites</i>, and <i>Goldius</i> come with the range of 18 to 20. <i>Goldius</i>, with 10 segments in the thorax and (apparently) 8 in the pygidium, comes nearest to the averages for these two parts of the trunk. <i>Goldius</i>, <i>Amphilichas</i>, <i>Bumastus</i>, <i>Acidaspis</i>, <i>Actinopeltis</i>, -and <i>Sphærexochus</i> are among the genera having 10 segments in the thorax, and there are +and <i>Sphærexochus</i> are among the genera having 10 segments in the thorax, and there are many genera which have only one or two segments more or less than 10.</p> <p>In most Ordovician genera, thirty-five out of the forty tabulated, the number of segments @@ -7657,7 +7617,7 @@ tendency to become fixed.</p> <i>Bathyurellus</i>, <i>Ogygiocaris</i>, <i>Asaphus</i>, <i>Ogygites</i>, <i>Isotelus</i>, <i>Goldius</i>, <i>Cyclopyge</i>, <i>Amphilichas</i>, <i>Odontopleura</i>, <i>Acidaspis</i>, <i>Glaphurus</i>, <i>Encrinurus</i>, <i>Cybele</i>, <i>Cybeloides</i>, <i>Ectenonotus</i>, <i>Calymene</i>, <i>Ceraurus</i>, <i>Pliomera</i>, <i>Pliomerops</i>, <i>Pterygometopus</i>, <i>Chasmops</i>, <i>Eccoptochile</i>, <i>Actinopeltis</i>, -<i>Sphærexochus</i>, <i>Placoparia</i>, <i>Pilekia</i>, <i>Selenopeltis</i>, and <i>Calocalymene</i>.</p> +<i>Sphærexochus</i>, <i>Placoparia</i>, <i>Pilekia</i>, <i>Selenopeltis</i>, and <i>Calocalymene</i>.</p> <p><span class="pagenum"><a name="Page_131" id="Page_131">[131]</a></span></p> @@ -7666,29 +7626,29 @@ always possible to ascertain the exact number of segments in the pygidium, altho with smooth caudal shields had nearly all disappeared. The number of segments in the thorax had become pretty well fixed by the beginning of the Devonian, <i>Cyphaspis</i> with a range of from 10 to 17 furnishing the only notable exception. The range for the sixteen genera is -from 8 to 17, the average 11, the number exhibited by the Phacopidæ which form so large +from 8 to 17, the average 11, the number exhibited by the Phacopidæ which form so large a part of the trilobites of the Devonian. The greater part of the species have large pygidia, and while the range is from 3 to 23, the average is 11.2. <i>Probolium</i>, with 11 in the thorax and 11-13 in the pygidium, and <i>Phacops</i>, with 11 in the thorax and 9-12 in the pygidium, approach very closely to the "average" trilobite, and various species of other -genera of the Phacopidæ have the same number of segments as the norm. In every genus, +genera of the Phacopidæ have the same number of segments as the norm. In every genus, however, the number of segments in the pygidium is variable, the greatest variation being in <i>Dalmanites</i>, with a range of from 9 to 23. The number of segments in the pygidium was therefore not fixed and was on the average higher than in earlier periods.</p> -<p>The genera used in the tabulation were: <i>Calymene</i>, <i>Dipleura</i>, <i>Goldius</i>, <i>Proëtus</i>, <i>Cyphaspis</i>, +<p>The genera used in the tabulation were: <i>Calymene</i>, <i>Dipleura</i>, <i>Goldius</i>, <i>Proëtus</i>, <i>Cyphaspis</i>, <i>Acidaspis</i>, <i>Phacops</i>, <i>Hausmania</i>, <i>Coronura</i>, <i>Odontochile</i>, <i>Pleuracanthus</i>, <i>Calmonia</i>, <i>Pennaia</i>, <i>Dalmanites</i>, <i>Probolium</i>, and <i>Cordania</i>.</p> -<p>The trilobites of the late Palæozoic (Mississippian to Permian) belong, with two possible -exceptions, to the Pröetidæ, and only three genera, <i>Proëtus</i>, <i>Phillipsia</i>, and <i>Griffithides</i>, +<p>The trilobites of the late Palæozoic (Mississippian to Permian) belong, with two possible +exceptions, to the Pröetidæ, and only three genera, <i>Proëtus</i>, <i>Phillipsia</i>, and <i>Griffithides</i>, appear to be known from all the parts. I am, however, assuming that both <i>Brachymetopus</i> and <i>Anisopyge</i> have 9 segments in the thorax, and so have tabulated five genera. The range in the number of segments in the pygidium is large, from 10 in some species of -<i>Proëtus</i> to 30 in <i>Anisopyge</i>, and the average, 17.3, is high, as is the average for total number +<i>Proëtus</i> to 30 in <i>Anisopyge</i>, and the average, 17.3, is high, as is the average for total number in the trunk, 26.3. <i>Anisopyge</i>, a late Permian trilobite described by Girty from Texas, is perhaps the last survivor of the group. It seems to have had 39 segments in the trunk, -making it, next to the Cambrian <i>Pædeumias</i> and <i>Menomonia</i>, the most numerously segmented +making it, next to the Cambrian <i>Pædeumias</i> and <i>Menomonia</i>, the most numerously segmented of all the trilobites.</p> <p>The above data may be summarized in the following table:</p> @@ -7737,7 +7697,7 @@ of all the trilobites.</p> <td class="center">22.2<span style="color:#fff;">0</span></td> </tr> <tr> - <td class="tdl">Late Palæozoic</td> + <td class="tdl">Late Palæozoic</td> <td class="center"><span style="color:#fff;">0</span>5</td> <td class="center"><span style="color:#fff;">0</span>9<span style="color:#fff;">.00</span></td> <td class="center">17.3<span style="color:#fff;">0</span></td> @@ -7747,7 +7707,7 @@ of all the trilobites.</p> <p>This table confirms that made up by Carpenter, and shows even more strikingly the -progressive increase in the average number of segments in the trunk throughout the Palæozoic.</p> +progressive increase in the average number of segments in the trunk throughout the Palæozoic.</p> <p>While the two trilobites with the greatest number of segments are Cambrian, yet on the average, the last of the trilobites had the more numerously segmented bodies. The multisegmented @@ -7765,7 +7725,7 @@ trilobites are:</p> </tr> <tr> <td class="tdl" style="padding-right: 7px;">Lower Cambrian</td> - <td><i>Pædeumias</i></td> + <td><i>Pædeumias</i></td> <td class="center">44+<span style="color:#fff;">....</span></td> <td class="center"><span style="color:#fff;">0</span>1</td> <td class="center">45+</td> @@ -7832,7 +7792,7 @@ trilobites are:</p> <p><i>Anisopyge</i>, the last of the trilobites, stands third on the list of those having great numbers of segments, and in each period there are a few which have considerably more than the average number. It may be of some significance that of these nine genera only -<i>Pædeumias</i> and <i>Anisopyge</i> belong to the Opisthoparia, the great central group, and that five +<i>Pædeumias</i> and <i>Anisopyge</i> belong to the Opisthoparia, the great central group, and that five are members of the Proparia, the latest and most specialized order.</p> @@ -7846,7 +7806,7 @@ of the protaspis which lacked these organs. It remains to inquire which among th other characteristics are most fundamental.</p> <p>Among the trilobites of the Lower Cambrian, no very young have been seen except -of Mesonacidæ. Of these, the ontogeny of <i>Elliptocephala asaphoides</i> Emmons is best known, +of Mesonacidæ. Of these, the ontogeny of <i>Elliptocephala asaphoides</i> Emmons is best known, thanks to Ford, Walcott, and Beecher, but, as the last-named has pointed out, the actual protaspis or earliest shield has not yet been found. The youngest specimen is the one roughly figured by Beecher (1895 C, p. 175, fig. 6). It lacks the pygidium, but if completed by @@ -7856,8 +7816,8 @@ The axial lobe was narrow, of uniform width along the cephalon, showed a neck-ri four indistinct annulations, but did not reach quite to the anterior end, there being a margin in front of the glabella about 0.1 mm. wide. The greatest width of the cephalon was 0.66 mm., and of the glabella 0.233 mm., or practically 35 per cent of the total width. -Other young <i>Elliptocephala</i> up to a length of 1 mm., and young <i>Pædeumias</i>, <i>Mesonacis</i>, and -<i>Holmia</i> (see Kiær, Videnskaps, Skrifter, 1 Mat.-Naturv. Klasse, 1917, No. 10) show about +Other young <i>Elliptocephala</i> up to a length of 1 mm., and young <i>Pædeumias</i>, <i>Mesonacis</i>, and +<i>Holmia</i> (see Kiær, Videnskaps, Skrifter, 1 Mat.-Naturv. Klasse, 1917, No. 10) show about the same characteristics, but all these have large compound eyes on the dorsal surface and specimens in still younger stages are expected. It may be pointed out, however, that in these specimens the pygidium is proportionately larger than in the adult. Walcott cites one @@ -7870,7 +7830,7 @@ per cent of the whole length.</p> <p>The development of several species of trilobites from the Middle Cambrian is known. Barrande (1852) described the protaspis of <i>Sao hirsuta</i>, <i>Peronopsis integer</i>, <i>Phalacroma bibullatum</i>, <i>P. nudum</i>, and <i>Condylopyge rex</i>. Broegger figured that of a <i>Liostracus</i> (Geol. For. -Förhandl., 1875, pl. 25, figs. 1-3) and Lindstroem (1901, p. 21) has reproduced the same. +Förhandl., 1875, pl. 25, figs. 1-3) and Lindstroem (1901, p. 21) has reproduced the same. Matthew (Trans. Roy. Soc. Canada, vol. 5, 1888, pl. 4, pls. 1, 2) has described the protaspis of a <i>Liostracus</i>, <i>Ptychoparia linnarssoni</i> Broegger, and <i>Solenopleura robbi</i> Hartt. Beecher (1895 C, pl. 8) has figured the protaspis of <i>Ptychoparia kingi</i> Meek, and the writer @@ -7908,12 +7868,12 @@ and <i>Condylopyge rex</i>, the axial lobe is outlined on each of the equal shie about 1 mm. long, but is without furrows and reaches neither anterior nor posterior margin.</p> <p>From the foregoing brief description it appears that the pygidium of the protaspis -varies in different groups from as little as 15 per cent of the total length in the Mesonacidæ -to as much as 50 per cent in the Agnostidæ; that the axial lobe varies from as little as 14 +varies in different groups from as little as 15 per cent of the total length in the Mesonacidæ +to as much as 50 per cent in the Agnostidæ; that the axial lobe varies from as little as 14 per cent of the total width in one <i>Ptychoparia</i> to as much as 50 per cent in <i>Phalacroma -nudum</i>; that the glabella reaches the anterior margin in the Olenidæ, Solenopleuridæ, and -<i>Phalacroma bibullatum</i>, while there is a brim in front of it in the Olenellidæ, Paradoxidæ, -and three of the species of the Agnostidæ. The decision as to which of these conditions +nudum</i>; that the glabella reaches the anterior margin in the Olenidæ, Solenopleuridæ, and +<i>Phalacroma bibullatum</i>, while there is a brim in front of it in the Olenellidæ, Paradoxidæ, +and three of the species of the Agnostidæ. The decision as to which of these conditions are primitive may be settled quite satisfactorily by study of the ontogeny of the various species.</p> @@ -8120,13 +8080,13 @@ expense of the pygidium.</p> <p>If this conclusion can be sustained by other trilobites, it indicates that the large pygidium is a more primitive characteristic of a protaspis than is a small one. I have already -shown that the pygidium is proportionately larger in the protaspis in the Mesonacidæ, Solenopleuridæ, -and Olenidæ, and a glance at Barrande's figures of <i>"Hydrocephalus" carens</i> and +shown that the pygidium is proportionately larger in the protaspis in the Mesonacidæ, Solenopleuridæ, +and Olenidæ, and a glance at Barrande's figures of <i>"Hydrocephalus" carens</i> and <i>"H." saturnoides</i>, both young of <i>Paradoxides</i> will show that the same process of development goes on in that genus as in <i>Sao</i>. There is first an enlargement of the pygidium to a maximum, a rise from 20 per cent to 33 per cent in the case of <i>H. carens</i> and then, with the introduction of thoracic segments, a very rapid falling off. All of these are, however, -trilobites with small pygidia, and it has been a sort of axiom among palæontologists that +trilobites with small pygidia, and it has been a sort of axiom among palæontologists that large pygidia were made up of a number of coalesced segments. While not definitely so stated, it has generally been taken to mean the joining together of segments once free. The asaphid, for instance, has been thought of as descended from some trilobite with rich segmentation, @@ -8319,10 +8279,10 @@ would be in the adult.</p> <p>This conception of the breaking down of the pygidium to form the thorax will be very helpful in explaining many things which have hitherto seemed anomalous. For instance, -it indicates that the Agnostidæ, whose subequal shields in early stages have been a puzzle, -are really primitive forms whose pygidia do not degenerate; likewise the Eodiscidæ, which, +it indicates that the Agnostidæ, whose subequal shields in early stages have been a puzzle, +are really primitive forms whose pygidia do not degenerate; likewise the Eodiscidæ, which, however, show within the family a tendency to free some of the segments. The annelidan -Mesonacidæ may not be so primitive after all, and their specialized cephala may be more +Mesonacidæ may not be so primitive after all, and their specialized cephala may be more truly indicative of their status than has previously been supposed.</p> <p>The facts of ontogeny of trilobites with both small and large pygidia do show that @@ -8373,7 +8333,7 @@ same simplicity has been noted in the young of other genera. Beecher considered due to imperfect preservation of the exceedingly small shells, which practically always occur as moulds or casts in soft shale. There is, however, a very general increase in the strength of glabellar segmentation in the early part of the ontogeny of all trilobites whose life history -is known, and in some genera, like the Agnostidæ, there is no question of the comparatively +is known, and in some genera, like the Agnostidæ, there is no question of the comparatively late acquisition of glabellar furrows. Even in <i>Paradoxides</i>, the furrows appear late in the ontogeny.</p> @@ -8381,8 +8341,8 @@ in the ontogeny.</p> <p>If absence of eyes on the dorsal surface be primitive, as Beecher has shown, and if the large pygidium, narrow axial lobe, and long unsegmented glabella be primitive, then -the known protaspis of the Mesonacidæ and Paradoxidæ is not primitive, that of the Olenidæ -is very primitive, and that of the Agnostidæ is primitive except that in one group the +the known protaspis of the Mesonacidæ and Paradoxidæ is not primitive, that of the Olenidæ +is very primitive, and that of the Agnostidæ is primitive except that in one group the axial lobe, when it appears, is rather wide, and in the other a brim is present.</p> <p>Subsequent development from the simple unsegmented protaspis would appear to show, @@ -8404,7 +8364,7 @@ life, and kept or even increased (<i>Isotelus</i>) the large pygidium.</p> <img src="images/fig_35.png" width="92" height="150" alt="" title="" /> <p class="fig_caption"><span class="smcap">Fig. 35.</span>—A specimen of <i>Weymouthia nobilis</i> (Ford), collected by Mr. Thomas H. Clark at North Weymouth, Mass. Note the broad -smooth shields of this Lower Cambrian eodiscid. × 6.</p> +smooth shields of this Lower Cambrian eodiscid. × 6.</p> </div> <p>In the discussion above I have placed great emphasis on the large size of the primitive @@ -8413,13 +8373,13 @@ have been overlooked.</p> <p>If the large pygidium is primitive, then multisegmentation in trilobites can not be primitive but is the result of adaptation to a crawling life. It is annelid-like, but is not in itself -to be relied upon as showing relationship to the Chætopoda. Simple trilobites with few segments, -like the Agnostidæ, Eodiscidæ etc., were, therefore, properly placed by Beecher at +to be relied upon as showing relationship to the Chætopoda. Simple trilobites with few segments, +like the Agnostidæ, Eodiscidæ etc., were, therefore, properly placed by Beecher at <span class="pagenum"><a name="Page_139" id="Page_139">[139]</a></span> the base of his classification, and there is now less chance than ever that they can be called degenerate animals.</p> -<p>From the phylogeny of certain groups, such as the Asaphidæ, it is learned that the geologically +<p>From the phylogeny of certain groups, such as the Asaphidæ, it is learned that the geologically older members of the family have more strongly segmented anterior and posterior shields than the later ones. That there has been a "smoothing out" is demonstrated by a study of the ontogeny of the later forms. From such examples it has come to be thought @@ -8427,15 +8387,15 @@ that all smooth trilobites are specialized and occupy a terminal position in the line. This has caused some wonder that smooth agnostids like <i>Phalacroma bibullatum</i> and <i>P. nudum</i> should be found in strata so old as the Middle Cambrian, and was a source of great perplexity to me in the case of <i>Weymouthia</i> (Ottawa Nat., vol. 27, 1913) -(<a href="#fig_35">fig. 35</a>). This is a smooth member of the Eodiscidæ, and, in fact, one of the simplest trilobites +(<a href="#fig_35">fig. 35</a>). This is a smooth member of the Eodiscidæ, and, in fact, one of the simplest trilobites known, for while it has three thoracic segments, it shows almost no trace of dorsal furrows or segmentation on cephalon or pygidium, and, of course, no eyes. Following the general rule, I took this to be a smooth-out eodiscid, and was surprised that it should come from the Lower Cambrian, where it is associated with <i>Elliptocephala</i> at Troy, New York, and with <i>Callavia</i> at North Weymouth, Massachusetts, and where it has lately been found -by Kiær associated with <i>Holmia</i> and <i>Kjerulfia</i> at Tømten, Norway. It now appears it is +by Kiær associated with <i>Holmia</i> and <i>Kjerulfia</i> at Tømten, Norway. It now appears it is really in its proper zone, and instead of being the most specialized, is the simplest of the -Eodiscidæ.</p> +Eodiscidæ.</p> <p>What appears to be a still simpler trilobite is the form described by Walcott as Naraoia.</p> @@ -8507,11 +8467,11 @@ integer</i> (Barrande, Syst. Sil., vol. 1, pl. 49).</p> originating with Hatschek (1877) and so ably championed by Bernard (1892), has now been a fundamental working hypothesis for some years, and has had a profound influence in shaping thought about trilobites. This hypothesis has, however, its weak points, the principal -one being its total inhibition of the workings of that great talisman of the palæontologist, +one being its total inhibition of the workings of that great talisman of the palæontologist, the law of recapitulation. Its acceptance has forced the zoologist to look upon the nauplius as a specially adapted larva, and has caused more than one forced explanation of the protaspis of the trilobite. When so keen a student as Calman says that the nauplius -must point in some way to the ancestor of the Crustacea (1909, p. 26), it is time to reëxamine +must point in some way to the ancestor of the Crustacea (1909, p. 26), it is time to reëxamine some of the fundamentals. This has been done in the preceding pages and evidence adduced to show that the primitive features of a trilobite indicate a swimming animal, and that the adaptations are those which enabled it to assume a crawling mode of existence. @@ -8543,7 +8503,7 @@ the swimmers among them.</p> remote ancestor of the trilobites to have had is <i>Amiskwia sagittiformis</i> Walcott (Smithson. Misc. Coll., vol. 57, 1911, p. 112, pl. 22, figs. 3, 4). This "worm" from the Middle Cambrian is similar in outline to the recent <i>Spadella</i>, and is referred by Walcott to the -Chætognatha. It has a pair of lateral expansions and a flattened caudal fin, a narrow +Chætognatha. It has a pair of lateral expansions and a flattened caudal fin, a narrow median alimentary canal, and a pair of rather long simple tentacles. With the exception of a thin septum back of the head, no traces of segmentation are shown.</p> @@ -8554,7 +8514,7 @@ contact surface, and a test on the dorsal side. The first use of the appendages been in pushing food forward to the mouth, and for the greater convenience in catching such material, a fold in front of the mouth may have elongated to form the prototype of the hypostoma. At this time the substratum may not have been the ocean bottom at all, -but the animals, still free swimmers, may have alighted at feeding time on floating algæ +but the animals, still free swimmers, may have alighted at feeding time on floating algæ from the surface of which they collected their food. While the dorsal test was originally jointed at every segment, the undulatory mode of swimming seems to have given way to the method of sculling by means of the posterior end only, or by the use of the appendages, and @@ -8604,14 +8564,14 @@ are the more primitive. The antennules of Nebalia are elongate, those of <i>Apus the mandible of <i>Nebalia</i> has a long endopodite, and Carpenter points out that from it either the malacostracan mandible with a reduced endopodite or the branchiopodan mandible with none could be derived, but that the former could not have arisen from the latter. -The maxillæ of <i>Apus</i> are also much the more specialized and reduced.</p> +The maxillæ of <i>Apus</i> are also much the more specialized and reduced.</p> <p><i>Nebalia</i> being in all else more primitive than <i>Apus</i>, it follows that the numerous abdominal segments of the latter may well have arisen by the multiplication of an originally moderate number, and the last trace of primitiveness disappears.</p> <p>It is now possible to add to the results obtained from comparative morphology the testimony -of palæontology, already outlined above, and since the two are in agreement, it must +of palæontology, already outlined above, and since the two are in agreement, it must be admitted that the modern Branchiopoda are really highly specialized.</p> <p>As has already been pointed out, <i>Hymenocaris</i>, the leptostracan of the Middle Cambrian, @@ -8629,7 +8589,7 @@ and also that the latter were derived from them. It seems very generally agreed the Malacostraca are descended from the Leptostraca, and the fossils of the Pennsylvanian supply a number of links in the chain of descent. Thus, <i>Pygocephalus cooperi</i>, with its brood pouches, is believed by Calman (1909, p. 181) to stand at the base of the Peracaridan -series of orders, and <i>Uronectes</i>, <i>Palæocaris</i>, and the like are Palæozoic representatives of the +series of orders, and <i>Uronectes</i>, <i>Palæocaris</i>, and the like are Palæozoic representatives of the Syncarida. Others of the Pennsylvanian species appear to tend in the direction of the Stomatopoda, <span class="pagenum"><a name="Page_143" id="Page_143">[143]</a></span> whose true representatives have been found in the Jurassic. The Isopoda seem @@ -8644,7 +8604,7 @@ developed, unless, as seems entirely possible, compound eyes have been developed in various groups. Most Crustacea were derived from crawling trilobites (Lower Cambrian or pre-Cambrian Opisthoparia), for they lost the large pygidium, and also the major part of the pleural lobes. In all Crustacea, too, other than the Copepoda and Ostracoda, -there is a tendency to lose the exopodites of the antennæ.</p> +there is a tendency to lose the exopodites of the antennæ.</p> <p>These modifications, which produced a considerable difference in the general appearance of the animal, are easily understood. As has been shown in previous pages, the trilobites @@ -8662,7 +8622,7 @@ to have had in that of man.</p> <p>An intermediate stage between the Trilobita and the higher Crustacea is at last exhibited to us by the wonderful, but unfortunately rather specialized <i>Marrella</i>, already described. It retains the hypostoma and the undifferentiated biramous appendages of the trilobite, but -has uniramous antennæ, there are no endobases on the coxopodites of the thoracic appendages, +has uniramous antennæ, there are no endobases on the coxopodites of the thoracic appendages, the pygidium is reduced to a single segment, and the lateral lobes of the thorax are also much reduced. <i>Marrella</i> is far from being the simplest of its group, but is the only example which survived even down to Middle Cambrian times of what was probably once @@ -8673,14 +8633,14 @@ explicable and points very definitely to the ancestor. According to Calman (1909 <div class="blockquot"><p>The typical nauplius has an oval unsegmented body and three pairs of limbs, corresponding to the antennules, antennas, and mandibles of the adult. The antennules are uniramous, the others biramous, and all -three pairs are used in swimming. The antennæ may have a spiniform or hooked masticatory process at the +three pairs are used in swimming. The antennæ may have a spiniform or hooked masticatory process at the base, and share with the mandibles which have a similar process, the function of seizing and masticating the food. The mouth is overhung by a large labrum or upper lip and the integument of the dorsal surface of the body forms a more or less definite dorsal shield. The paired eyes are as yet wanting, but the median eye is large and conspicuous.</p></div> <p>The large labrum or hypostoma, the biramous character of the appendages, especially -of the antennæ, the functional gnathobases on the second and third appendages, and the +of the antennæ, the functional gnathobases on the second and third appendages, and the oval unsegmented shield are all characteristics of the trilobites, and it is interesting to note that all nauplii have the free-swimming habit.</p> @@ -8750,19 +8710,19 @@ whole body. Such a shell need not have been segmented, and, in fact, the stiffer the more reason for development of the appendages. Activity as a swimming and crawling animal tended to break up the dorsal test into segments corresponding to those of the soft parts, and, by adaptation, a floating animal became a crawling one, with consequent change -from a form like that of <i>Naraoia</i> to one like <i>Pædeumias</i>. +from a form like that of <i>Naraoia</i> to one like <i>Pædeumias</i>. (See figs. <a href="#fig_36">36</a>-<a href="#fig_40">40</a>.) A continuation of this line of development by breaking up and loss of the dorsal test led through forms similar to <i>Marrella</i> to the Branchiopoda of the Cambrian, in which not only is there great reduction in the test, but also loss of appendages. The origin of the carapace is still obscure, but Bernard (1892, p. 214, fig. 48) has already pointed out that some trilobites, -Acidaspidæ particularly, have backward projecting spines on the posterior margin of the +Acidaspidæ particularly, have backward projecting spines on the posterior margin of the cephalon, which suggest the possibility of the production of such a shield, and in <i>Marrella</i> such spines are so extravagantly developed as almost to confirm the probability of such <span class="pagenum"><a name="Page_146" id="Page_146">[146]</a></span> -origin. In this line of development two pairs of tactile antennæ were produced, while the +origin. In this line of development two pairs of tactile antennæ were produced, while the anomomeristic character of the trilobite was retained. From similar opisthoparian ancestors -there were, however, derived primitive Malacostraca retaining biramous antennæ, but +there were, however, derived primitive Malacostraca retaining biramous antennæ, but with a carapace and reduced pleural lobes and pygidium. From this offshoot were probably derived the Ostracoda, the Cirripedia, and the various orders of the Malacostraca, with the possible exception of the Isopoda. I have suggested independent origins of the Copepoda @@ -8780,7 +8740,7 @@ interpretation.</p> Walcott. Natural size.</p> </td> <td class="vtop" style="padding:0 10px;"><p class="fig_caption"><span class="smcap">Fig. 37.</span>—<i>Pagetia clytia</i> Walcott. An eodiscid with compound eyes. After - Walcott. × 5.</p> + Walcott. × 5.</p> </td> </tr> </table> @@ -8795,10 +8755,10 @@ interpretation.</p> </tr> <tr> <td class="vtop" style="padding:0 10px;"><p class="fig_caption"><span class="smcap">Fig. 38.</span>—<i>Asaphiscus wheeleri</i> Meek. A representative trilobite of the - Middle Cambrian of the Pacific province. After Meek. × 1/2.</p> + Middle Cambrian of the Pacific province. After Meek. × 1/2.</p> </td> - <td class="vtop" style="padding:0 10px;"><p class="fig_caption"><span class="smcap">Fig. 39.</span>—<i>Pædeumias robsonensis</i> Burling. Restored from a photograph - published by Burling. × 1/4.</p> + <td class="vtop" style="padding:0 10px;"><p class="fig_caption"><span class="smcap">Fig. 39.</span>—<i>Pædeumias robsonensis</i> Burling. Restored from a photograph + published by Burling. × 1/4.</p> </td> <td class="vtop" style="padding:0 10px;"><p class="fig_caption"><span class="smcap">Fig. 40.</span>—<i>Robergia</i> sp. Restored from fragments found in the Athens shale (Lower Middle Ordovician), at Saltville, Va. Natural size.</p> @@ -8828,7 +8788,7 @@ certain characteristics in common with the trilobites on the one hand and the Eu on the other. These relationships have been emphasized by Walcott, who derives the Eurypterida through the Limulava and the Aglaspina from the Trilobita. The Limulava may be derived from the Trilobita, but indicate a line somewhat different from that of the remainder -of the Crustacea. In this line the second cephalic appendages do not become antennæ. +of the Crustacea. In this line the second cephalic appendages do not become antennæ. and the axial lobe seems to broaden out, so that the pleural lobes become an integral part of the body. As in the modern Crustacea, the pygidium is reduced to the anal plate, and this grows out into a spine-like telson.</p> @@ -8844,7 +8804,7 @@ thorax only. Further than that the route is uncertain.</p> <p>Clarke and Ruedemann, whose recent extensive studies give their opinion much weight, seem fully convinced that the Merostomata could not have been derived from the Trilobita, but are rather inclined to agree with Bernard that the arachnids and the crustaceans were -derived independently from similar chætopod annelids (1912, p. 148).</p> +derived independently from similar chætopod annelids (1912, p. 148).</p> <p>The greater part of their work was, however, finished before 1910, and although they refer to Walcott's description of the Limulava (1911), they did not have the advantage @@ -8856,20 +8816,20 @@ descent from similar ancestors. Biramous limbs of the type found in the trilobit probably not be evolved independently on two lines, even if the ancestral stocks were of the same blood.</p> -<p>The Aglaspidæ, as represented by <i>Molaria</i> and <i>Habelia</i> in the Middle Cambrian, are +<p>The Aglaspidæ, as represented by <i>Molaria</i> and <i>Habelia</i> in the Middle Cambrian, are quite obvious closely related to the trilobites easily derived from them, and retain numerous of their characteristics. That they are not trilobites is, however, shown by the presence -of two pairs of antennæ, the absence of facial sutures, and the possession of a spine-like +of two pairs of antennæ, the absence of facial sutures, and the possession of a spine-like telson.</p> -<p>The Aglaspidæ have always been placed in the Merostomata, and nearer the Limulidæ +<p>The Aglaspidæ have always been placed in the Merostomata, and nearer the Limulidæ than the Eurypterida. The discovery of appendages does not at all tend to strengthen that view, but indicates rather that they are true Crustacea which have not given rise to any group now known. The exterior form is, however, <i>Limulus</i>-like, and since it is known from ontogeny that the ancestor of that genus was an animal with free body segments, there -is still a temptation to try to see in the Aglaspidæ the progenitors of the limulids.</p> +is still a temptation to try to see in the Aglaspidæ the progenitors of the limulids.</p> -<p>The oldest known <i>Limulus</i>-like animal other than the Aglaspidæ is <i>Neolimulus falcatus</i> +<p>The oldest known <i>Limulus</i>-like animal other than the Aglaspidæ is <i>Neolimulus falcatus</i> Woodward (Geol. Mag., dec. 1, vol. 5, 1868, p. 1, pl. 1, fig. 1). The structure of the head of this animal is typically limuloid, with simple and compound eyes and even the ophthalmic ridges. Yet, curiously enough, it shows what in a trilobite would be considered the posterior @@ -8877,8 +8837,8 @@ half of the facial suture, running from the eye to the genal angle. The body is of eight free segments with the posterior end missing. <i>Belinurus</i>, from the Mississippian and Pennsylvanian, has a sort of pygidium, the posterior three segments being fused together, and <i>Prestwichia</i> of the Pennsylvanian has all the segments of the abdomen fused together. -So far as form goes, a very good series of stages can be selected, from the Aglaspidæ of -the Cambrian through <i>Neolimulus</i> to the Belinuridæ of the late Palæozoic and the Limulidæ +So far as form goes, a very good series of stages can be selected, from the Aglaspidæ of +the Cambrian through <i>Neolimulus</i> to the Belinuridæ of the late Palæozoic and the Limulidæ of the Mesozoic to recent. Without much more knowledge of the appendages than is now available, it would be quite impossible to defend such a line. It is, however, suggestive.</p> @@ -8894,7 +8854,7 @@ the Ordovician. Since absolutely nothing is yet known of the land or even of the life of those periods, nothing can now be proved.</p> <p>In discussing the relationship of the trilobites to the various tracheate animals, I have -pointed out such palæontologic evidence as I have been able to gather. Studies in the field +pointed out such palæontologic evidence as I have been able to gather. Studies in the field of comparative morphology do not fall within my province. I only hope to have made the structure of the trilobite a little more accessible to the student of phylogenies.</p> @@ -8914,7 +8874,7 @@ While the only known animal which could possibly be referred to this group, <i>N blind, it is entirely possible that other species had eyes, and that the cephala and pygidia were variously modified. For this reason and because of the lack of all thoracic segments, it seems better to erect a new order rather than merely a family for the group, and <i>Nektaspia</i> -(swimming shields) may be suggested. The only known family is Naraoidæ Walcott, +(swimming shields) may be suggested. The only known family is Naraoidæ Walcott, which must be redefined.</p> <p><i>Marrella</i> and <i>Habelia</i> are types of Crustacea which can neither be placed in the Trilobita @@ -8923,14 +8883,14 @@ group, the members of which are, so far as known, adapted to the crawling mode o life, though it may prove that there are also swimmers which can be classified with them. To this subclass the name <i>Haplopoda</i> may be applied, the feet being simple.</p> -<p>The two known families, Marrellidæ Walcott and Aglaspidæ Clarke, belong to different +<p>The two known families, Marrellidæ Walcott and Aglaspidæ Clarke, belong to different orders, the second having already the name Aglaspina Walcott. The name <i>Marrellina</i> may therefore be used for the other.</p> <p>For <i>Sidneyia</i>, Walcott proposed the new subordinal name Limulava, placing it under the Eurypterida. While <i>Sidneyia</i>, <i>Emeraldella</i>, and <i>Amiella</i> may belong to the group that gave rise to the Eurypterida, they are themselves Crustacea, and a place must be found for -them in that group. The possession of only one pair of antennæ prevents their reception +them in that group. The possession of only one pair of antennæ prevents their reception by the Haplopoda, and allies them to the Trilobita, but the modifications of the trunk and its appendages keep them out of that subclass, and a new one has to be erected for them. This may be known as the <i>Xenopoda</i>, in allusion to the strange appendages of <i>Sidneyia</i>.</p> @@ -8942,20 +8902,20 @@ This may be known as the <i>Xenopoda</i>, in allusion to the strange appendages <p class="center">Subclass Trilobita Walch.</p> -<p>Crustacea with one pair of uniramous antennæ, and possessing facial sutures.</p> +<p>Crustacea with one pair of uniramous antennæ, and possessing facial sutures.</p> <p class="center">Order Nektaspia nov.</p> <p>Trilobita without thoracic segments. Cephala and pygidia simple.</p> -<p class="center">Family Naraoidæ Walcott.</p> +<p class="center">Family Naraoidæ Walcott.</p> <p>Cephalon and pygidium large, both shields nearly smooth. Eyes absent. A single species: <i>Naraoia compacta</i> Walcott, Middle Cambrian, British Columbia.</p> <p class="center">Subclass Haplopoda nov.</p> -<p>Crustacea with trilobate form, two pairs of uniramous antennæ, no facial sutures, sessile +<p>Crustacea with trilobate form, two pairs of uniramous antennæ, no facial sutures, sessile compound eyes present or absent, pygidium and pleural lobes generally reduced, large labrum present, appendages of the trunk biramous.</p> @@ -8966,7 +8926,7 @@ a small plate.</p> <p><span class="pagenum"><a name="Page_149" id="Page_149">[149]</a></span></p> -<p class="center">Family Marrellidæ Walcott.</p> +<p class="center">Family Marrellidæ Walcott.</p> <p>Cephalon with long genal and nuchal spines. Eyes marginal. A single species: <i>Marrella splendens</i> Walcott, Middle Cambrian, British Columbia.</p> @@ -8975,7 +8935,7 @@ splendens</i> Walcott, Middle Cambrian, British Columbia.</p> <p>Body trilobite-like, with few thoracic segments, and a spine-like telson. Appendages biramous.</p> -<p class="center">Family Aglaspidæ Clarke.</p> +<p class="center">Family Aglaspidæ Clarke.</p> <p>Cephalon trilobate, with or without compound eyes, seven or eight segments in the thorax.</p> @@ -8993,7 +8953,7 @@ splendens</i> Walcott, Middle Cambrian, British Columbia.</p> <p class="center">Subclass Xenopoda nov.</p> -<p>Crustacea with more or less eurypterid-like form, one pair of uniramous antennæ, biramous +<p>Crustacea with more or less eurypterid-like form, one pair of uniramous antennæ, biramous appendages on anterior part of trunk, modified endopodites on cephalon.</p> <p class="center">Order Limulava Walcott.</p> @@ -9001,7 +8961,7 @@ appendages on anterior part of trunk, modified endopodites on cephalon.</p> <p>Cephalon with lateral or marginal eyes and large epistoma. Body with eleven free segments and a telson. Cephalic appendages grouped about the mouth.</p> -<p class="center">Family Sidneyidæ Walcott.</p> +<p class="center">Family Sidneyidæ Walcott.</p> <p>Trunk probably with exopodites only, and without appendages on the last two segments. Telson with a pair of lateral swimmerets.</p> @@ -9015,7 +8975,7 @@ Cambrian, British Columbia.</p> <p>Middle Cambrian, British Columbia.</p> -<p class="center">Family Emeraldellidæ nov.</p> +<p class="center">Family Emeraldellidæ nov.</p> <p>Trunk with biramous appendages in anterior part, and appendages on all segments except possibly the spine-like telson.</p> @@ -9139,7 +9099,7 @@ the right side. The dactylopodite of the endopodite is especially well preserved the end rounded but not enlarged or pointed, and bears three small sharp spines, all in a horizontal plane, one anterior, one central, and one posterior. The outer ends of the exopodites show about ten segments each (in 2.5 mm.) beyond the margin of the test, and -from three to five setæ attached to the posterior side of each segment. These hairs are +from three to five setæ attached to the posterior side of each segment. These hairs are attached in a groove, well shown in this specimen. On the anterior margin of the exopodite there is a minute spine at each joint.</p> @@ -9160,7 +9120,7 @@ have one or two terminal spines. The antennules are unusually well preserved and have about forty segments each in front of the cephalon, or an average of five to one millimeter.</p> -<p>Specimens 209 and 210 are on a slab about 7 × 5.5 inches, and with them are twelve +<p>Specimens 209 and 210 are on a slab about 7 × 5.5 inches, and with them are twelve other more or less well preserved individuals, all but one of which are smaller than these. Two of the fourteen are ventral side up on the slab, which means dorsal side up in the rock. Nine are oriented in one direction, two at exactly right angles to this, and three at an angle @@ -9224,9 +9184,9 @@ are three pits for the articulation of spines, and on the propodite, one.</p> <p>The exopodites belonging to the thoracic segments are of equal length with the endopodites, and while the proximal portion of each is stouter than that of the corresponding endopodite, the exopodites taper to a hair-like termination, while the endopodites remain -fairly stout to the distal segment. Most of the setæ of the exopodites have been removed, +fairly stout to the distal segment. Most of the setæ of the exopodites have been removed, so that each remains as a curving, many-segmented organ, transversely striated, with a continuous -groove along the posterior side. The setæ appear to be set in this groove, one for +groove along the posterior side. The setæ appear to be set in this groove, one for each of the transverse ridges on the shaft.</p> <p>A good deal of the test has been cut away on the left-hand side from the thorax and @@ -9254,7 +9214,7 @@ anal segment extends 0.75 mm. behind the pygidium, and is 1.6 mm. in greatest wi <p>This specimen, which is developed from the dorsal surface, shows especially well nine appendages of the left side. The first represent the last segment of the cephalon; the remainder belong to the thorax. As is usual, the exopodites of these appendages overlie and -curve behind the endopodites. All the exopodites have lost their setæ and the segments of +curve behind the endopodites. All the exopodites have lost their setæ and the segments of the endopodites are flattened by crushing. The endopodites, while retaining only one or two of the movable spines, have the cup-like bases of from two to four on each of the visible segments, namely, the meropodite, carpopodite, propodite, and, in one case, the dactylopodite. @@ -9280,7 +9240,7 @@ articulating with the two branches of the limb.</p> <a name="fig_42" id="fig_42"></a> <img src="images/fig_42.png" width="228" height="220" alt="" title="" /> <p class="fig_caption"><span class="smcap">Fig. 42.</span>—<i>Triarthrus becki</i> Green. Appendages of specimen 204. Inked in -by Miss Wood from the original tracing. × 10.</p> +by Miss Wood from the original tracing. × 10.</p> </div> <p>This individual shows, better than any other, the connection of the exopodite with the @@ -9309,7 +9269,7 @@ thorax. These ridges are very low, and on each segment of the thorax there is a outside of which is a pair which are convergent forward, making angles of 35 to 45 with the axis.</p> -<p>The metastoma is shaped much like the hypostoma of an <i>Illænus</i>. It is convex, nearly +<p>The metastoma is shaped much like the hypostoma of an <i>Illænus</i>. It is convex, nearly semicircular, with the straight side forward, and there is a continuous raised border around the curved sides and back. This border is separated from the central convex body by a deep linear depression.</p> @@ -9331,12 +9291,12 @@ and lie within the axial lobe.</p> <p>The shaft of the exopodite is made up of numerous short segments which at their anterior outer angles are produced into spines, and which also bear movable spines along the anterior border. As shown in several other specimens, the exopodite ends in a more or less -long spoon-shaped segment bearing on its lower surface a broad groove. No setæ appear +long spoon-shaped segment bearing on its lower surface a broad groove. No setæ appear to be attached to this, but both anterior and posterior margins bear numerous small, apparently movable spines. From the groove along the ventral side of the remainder of the exopodite arise numerous long slender filaments which become progressively shorter toward the tip. This specimen shows that they are not cylindrical, but are flattened along opposite -faces, at least at their distal ends. While no connection can be seen between adjacent setæ, +faces, at least at their distal ends. While no connection can be seen between adjacent setæ, they seem to stay together like the barbs on a feather.</p> <p><i>Measurements:</i> Length, 33 mm., width at back of cephalon, 16 mm.; from front of @@ -9375,7 +9335,7 @@ beyond the cephalon.</p> <img src="images/fig_43.png" width="124" height="183" alt="" title="" /> <p class="fig_caption"><span class="smcap">Fig. 43.</span>—<i>Triarthrus becki</i> Green. Drawing to represent the writer's interpretation of the appendages of specimen 218. Drawn by -Miss Wood. × 10.</p> +Miss Wood. × 10.</p> </div> <p class="section">Specimen No. 218 (<a href="#Plate_6">pl. 6, fig. 3</a>; text <a href="#fig_43">fig. 43</a>).</p> @@ -9388,7 +9348,7 @@ of the last two segments of the thorax, seen of course from the ventral side. Th shows well the broadening of the basipodite, ischiopodite, and meropodite, while the coxopodite is thick and heavy, and the inner end of the gnathobase somewhat rugose. Almost every segment of the endopodites has one or more pits for insertion of spines, these being -along the anterior or posterior margins. The exopodites lack the setæ, but show no unusual +along the anterior or posterior margins. The exopodites lack the setæ, but show no unusual features.</p> @@ -9465,9 +9425,9 @@ which are seen near the front of the glabella in many species of trinucleids.</p <a name="fig_45" id="fig_45"></a> <img src="images/fig_45.png" width="451" height="483" alt="" title="" /> <p class="fig_caption"><span class="smcap">Fig. 45.</span>—<i>Cryptolithus tessellatus</i> Green. Drawing of -specimen 233, made by Professor Beecher. × 9. Below are parts of two of +specimen 233, made by Professor Beecher. × 9. Below are parts of two of the endopodites of specimen 236, showing the interarticular membranes. -× 41.</p> +× 41.</p> </div> <p>The antennules are long, and are composed of far fewer and longer segments than @@ -9502,7 +9462,7 @@ of the fourth endopodite on the pygidium it is not possible to make out the deta appearance is of an endopodite consisting of short broad segments fringed at the back with short spines, the ones at the very posterior end appearing to be exceedingly short and rudimentary.</p> -<p>The exopodites are not so well shown as in some others but the setæ are flattened and +<p>The exopodites are not so well shown as in some others but the setæ are flattened and blade-shaped, and often bear numerous small spines.</p> <p><i>Measurements:</i> Length (lacking most of the fringe), 10.5 mm. Width of thorax, @@ -9540,9 +9500,9 @@ less fully developed than at present. On plate 9 are two figures in which specim <p>On the dorsal side, specimen 235 shows portions of three exopodites which lie in a direction roughly parallel to the outer portions of the endopodites on the lower side, that is, their direction if projected would reach the axis in an acute angle back of the end of the -pygidium. The setæ stand at right angles to the shaft, and on a portion of it 0.5 mm. long +pygidium. The setæ stand at right angles to the shaft, and on a portion of it 0.5 mm. long there are seven of them. This is a fragment of an exopodite near the front of the thorax, -and the setæ, which are flattened, are about 1.63 mm. long.</p> +and the setæ, which are flattened, are about 1.63 mm. long.</p> <p>On the ventral side this same specimen shows incomplete endopodites and exopodites of about seventeen segments, six of which would belong to the thorax and the remainder to @@ -9564,7 +9524,7 @@ endopodites they probably do belong to the outer halves of the appendages.</p> <p>The exopodites under the thorax are long, the shaft shows numerous short segments, and is in each case bent backward, though not through a right angle. They extend considerably -beyond the endopodites. The setæ do not diverge from the shaft at a right angle +beyond the endopodites. The setæ do not diverge from the shaft at a right angle as on the dorsal side of this same specimen, but at an acute angle, indicating that they were not rigid. The individual hairs are broad and blade-shaped, frequently with a linear depression along the median line, perhaps due to collapse of the internal tube.</p> @@ -9581,12 +9541,12 @@ All measurements were made on the photographs.</p> <p>The right half of the same thorax and pygidium as specimen No. 235.</p> <p>The specimen is cleaned from both upper and lower sides and, the dorsal test being removed, -reveals the long blade-like setæ of the exopodites, each blade being concave along +reveals the long blade-like setæ of the exopodites, each blade being concave along its median line. They are long on the exopodites of the thoracic segments, but become shorter, without, however, any visible change of form on the pygidium. Although the posterior end is not well preserved, one gets no suggestion from a study of this side of the specimens that the exopodites of the posterior end are in any striking way different from those of segments -further forward. The tips of some of the setæ show minute spines, one to each +further forward. The tips of some of the setæ show minute spines, one to each blade.</p> <p><span class="pagenum"><a name="Page_162" id="Page_162">[162]</a></span></p> @@ -9599,7 +9559,7 @@ Professor Beecher made a drawing of one of these which he placed under his pen d (text fig. 45).</p> <p><i>Measurements:</i> The specimen is 5 mm. long from the front of the second thoracic -segment to the end of the pygidium. The setæ on the exopodites of the anterior thoracic +segment to the end of the pygidium. The setæ on the exopodites of the anterior thoracic segments are 1.7 mm. long, as exposed from the dorsal side. Some of those on the posterior part of the pygidium, only incompletely exposed, are 0.31 mm. long.</p> @@ -9607,7 +9567,7 @@ part of the pygidium, only incompletely exposed, are 0.31 mm. long.</p> <a name="fig_46" id="fig_46"></a> <img src="images/fig_46.png" width="380" height="242" alt="" title="" /> <p class="fig_caption"><span class="smcap">Fig. 46.</span> <i>Cryptolithus tessellatus</i> Green. A part of a thorax and pygidium, -showing appendages. Drawn by Professor Beecher. Specimen 238. × 10.</p> +showing appendages. Drawn by Professor Beecher. Specimen 238. × 10.</p> </div> <p>The dactylopodite of the first endopodite showing the articular membranes is 0.23 mm. @@ -9621,11 +9581,11 @@ of this appendage are 0.15 mm. long. All measurements were made on photographs.< <p>A triangular specimen consisting of the greater part of a pygidium and parts of all the thoracic segments. Under the thorax the specimen has been so cleaned that the outer portions of the endopodites are well shown, while under the pygidium the greater part of the -endopodites seem to have been removed, disclosing the setæ of the exopodites. As in other +endopodites seem to have been removed, disclosing the setæ of the exopodites. As in other specimens, the endopodites of the thorax turn backward at the distal end of the carpopodite, which is broad and curved, and bears a tuft of spines on the posterior margin. The dactylopodites seem to preserve their natural shape, and are very nearly cylindrical in form. -Under the pygidium are several sets of overlapping fringes of setæ of exopodites, and along +Under the pygidium are several sets of overlapping fringes of setæ of exopodites, and along the edge of the dorsal furrow, a number of fragments of segments of what may be coxopodites while with them are a number of fragmentary shaft of exopodites.</p> @@ -9646,21 +9606,21 @@ Nat., vol. 7, pp. 741-742. </p> <p class="larger"><span class="smcap">Angelina N. P.</span></p> -<p class="references">1854.—Palæontologia Scandinavica, pars 1, Crustacea formationis +<p class="references">1854.—Palæontologia Scandinavica, pars 1, Crustacea formationis transitionis. </p> <p class="larger"><span class="smcap">Audouin, J. V.</span></p> <p class="references">1821.—Recherches sur les rapports naturels qui existent entre les -trilobites et les animaux articulés. Ann. Gen. Sci. Phys. Nat. +trilobites et les animaux articulés. Ann. Gen. Sci. Phys. Nat. Bruxelles, vol. 8, p. 233, pl. 26. 1822. Isis (Encycl. Zeitung), Oken., vol. 10, p. 87, pl. 1, No. 4, figs. 1-5. </p> <p class="larger"><span class="smcap">Barrande, J.</span></p> -<p class="references">1852.—Systême Silurien du centre de la Bohême, vol. 1, pp. +<p class="references">1852.—Systême Silurien du centre de la Bohême, vol. 1, pp. 226-230, and 629, pl. 30, figs. 38, 39.</p> <p>1872.—Ibid., vol. 1, Suppl., p. 180, pl. 4. </p> @@ -9694,7 +9654,7 @@ pp. 298-300, pl. 7, text fig, 1.</p> <p class="references">1896 A.—The morphology of <i>Triarthrus</i>. Amer. Jour. Sci. (4), vol. 1, pp. 251-256, pl. 8; Geol. Mag., dec. 4, vol. 3, pp. 193-197, pl. 9.</p> -<p class="references">1896 B.—On a supposed discovery of the antennas of trilobites by Linnæus in 1759. Amer. +<p class="references">1896 B.—On a supposed discovery of the antennas of trilobites by Linnæus in 1759. Amer. Geol., vol. 17, pp. 303-306, text figs. 1-3.</p> <p class="references">1897 A.—Outline of a natural classification of trilobites. Amer. Jour. Sci. (4), vol. 3, pp. @@ -9718,9 +9678,9 @@ figs. 1-8.</p> <p class="larger"><span class="smcap">Bernard, H. M.</span></p> -<p class="references">1892.—The Apodidæ.</p> +<p class="references">1892.—The Apodidæ.</p> -<p class="references">1893.—Trilobites with antennæ at last! Nature, vol. 48, p. 582.</p> +<p class="references">1893.—Trilobites with antennæ at last! Nature, vol. 48, p. 582.</p> <p class="references">1894.—The systematic position of the trilobites. Quart. Jour. Geol. Soc., London, vol. 50, pp. 411-434, text figs. 1-17.</p> @@ -9733,7 +9693,7 @@ Geol. Soc., London, vol. 51, pp. 352-360, figs. A-C.</p> <p class="larger"><span class="smcap">Beyrich, E.</span></p> -<p class="references">1846.—Untersuchungen ueber Trilobiten. 2. Stück, p. 30, pl. 4, fig. 1c.</p> +<p class="references">1846.—Untersuchungen ueber Trilobiten. 2. Stück, p. 30, pl. 4, fig. 1c.</p> <p class="larger"><span class="smcap">Billings, E.</span></p> @@ -9745,10 +9705,10 @@ London, vol. 26, pp. 479-486, pls. 31-32. Abstract in Geol. Mag., vol. 7, p <p class="larger"><span class="smcap">Brongniart, A.</span></p> -<p class="references">1822.—Histoire naturelle des crustacés fossiles. Paris.</p> +<p class="references">1822.—Histoire naturelle des crustacés fossiles. Paris.</p> -<p class="larger"><span class="smcap">Brünnich, F. E.</span></p> +<p class="larger"><span class="smcap">Brünnich, F. E.</span></p> <p class="references">1781.—Beskrivelse over trilobiten, en dyreslaegt og dens arter, med en ney arts aftegning. Nye Samlig of det Kong. Danske Vidensk. Selskabs. Skriften, Copenhagen.</p> @@ -9756,7 +9716,7 @@ Nye Samlig of det Kong. Danske Vidensk. Selskabs. Skriften, Copenhagen.</p> <p class="larger"><span class="smcap">Burling, L. D.</span></p> -<p class="references">1916.—Pædeumias and the Mesonacidæ, with description of a new species, having at least +<p class="references">1916.—Pædeumias and the Mesonacidæ, with description of a new species, having at least 44 segments, from the Lower Cambrian of British Columbia. Ottawa Nat., vol. 30, pp. 53-58, pl. 1.</p> @@ -9787,7 +9747,7 @@ vol. 24, pp. 320-360, pl. 6.</p> <p class="larger"><span class="smcap">Castelnau, F. DE.</span></p> -<p class="references">1843.—Systeme Silurien de l'Amérique Septentrionale, p. 15, pl. 2, figs. 1, 4.</p> +<p class="references">1843.—Systeme Silurien de l'Amérique Septentrionale, p. 15, pl. 2, figs. 1, 4.</p> <p class="larger"><span class="smcap">Clarke, J. M.</span></p> @@ -9809,10 +9769,10 @@ insects. Amer. Nat, vol. 53, pp. 143-179.</p> <p class="larger"><span class="smcap">Dalman, J. W.</span></p> -<p class="references">1826.—Om Palæaderna eller de så kallade Trilobiterna. Stockholm, Acad. Handl., pp. +<p class="references">1826.—Om Palæaderna eller de sÃ¥ kallade Trilobiterna. Stockholm, Acad. Handl., pp. 113-152, 226-294.</p> -<p class="references">1828.—Ueber die Palæaden, oder die sogennanten Trilobiten. Nuremberg.</p> +<p class="references">1828.—Ueber die Palæaden, oder die sogennanten Trilobiten. Nuremberg.</p> <p class="larger"><span class="smcap">Dana, J. D.</span></p> @@ -9831,21 +9791,21 @@ Zeit.), Oken, 1825 and 1832.</p> <p class="larger"><span class="smcap">Dollo, L.</span></p> -<p class="references">1910.—La paléontologie éthologique. Bull. Soc. Beige de Geol., Pal., et d'Hydrol., vol. +<p class="references">1910.—La paléontologie éthologique. Bull. Soc. Beige de Geol., Pal., et d'Hydrol., vol. 23, pp. 377-421, figs. 1-13, pls. 7-11.</p> <p class="larger"><span class="smcap">Eichwald, E. VON.</span></p> -<p class="references">1825.—Geognostico-zoologicæ per Ingriam Marisque Baltici Provincias nee non de trilobitis +<p class="references">1825.—Geognostico-zoologicæ per Ingriam Marisque Baltici Provincias nee non de trilobitis observationes. Section 45.</p> -<p class="references">1858.—Beiträge zur geographischen Verbreitung der fossilen Thiere Russlands. Bull. Soc. +<p class="references">1858.—Beiträge zur geographischen Verbreitung der fossilen Thiere Russlands. Bull. Soc. Imp. des Natural, de Moscou, vol. 30, 1855-1857, p. 204.</p> -<p class="references">1860.—Lethæa Rossica, pl. 21.</p> +<p class="references">1860.—Lethæa Rossica, pl. 21.</p> -<p class="references">1863.—Beiträge zur nähern Kenntniss der in meiner Lethæa Rossica beschriebenen Ilænen. +<p class="references">1863.—Beiträge zur nähern Kenntniss der in meiner Lethæa Rossica beschriebenen Ilænen. Bull. Soc. Imp. des Natural, de Moscou, vol. 36, p. 408.</p> @@ -9873,7 +9833,7 @@ Elgin, Iowa. Proc. Iowa Acad. Sci. for 1903, vol. 11, pp. 179-181, pl. 14.</p> <p class="larger"><span class="smcap">Goldfuss, A.</span></p> -<p class="references">1828.—Observation sur le place qu'occupent les trilobites dans le règne animal. Ann. Sci. +<p class="references">1828.—Observation sur le place qu'occupent les trilobites dans le règne animal. Ann. Sci. Nat., Zoologie, vol. 15, p. 83, pl. 2, figs. 5, 7, 9, 10.</p> @@ -9914,7 +9874,7 @@ zool.-bot. Gesell., Vienna, Jahrg. 1914, pp. 1-7, pls. 1, 2.</p> <p class="larger"><span class="smcap">Jaekel, O.</span></p> -<p class="references">1901.—Beiträge zur Beurtheilung der Trilobiten, Theil I. Zeits. d. deutsch. geol. Gesell., +<p class="references">1901.—Beiträge zur Beurtheilung der Trilobiten, Theil I. Zeits. d. deutsch. geol. Gesell., Bd. 53, pp. 133-171. Pis. 4-6, text figs. 1-30.</p> @@ -9954,16 +9914,16 @@ pp. 430-432. pl. 8.</p> new ser., vol. 34, pp. 1-86, pls. 1-6.</p> -<p class="larger"><span class="smcap">Linné, K.</span></p> +<p class="larger"><span class="smcap">Linné, K.</span></p> -<p class="references">1759.—Petrificatet entomolithus paradoxus sådant, som det finnes uti Hans Excellence Riks. -Rådets Högoälborne Herr Grefve C. G. Tessins Samling. K. svenska Vet.-Akad. +<p class="references">1759.—Petrificatet entomolithus paradoxus sÃ¥dant, som det finnes uti Hans Excellence Riks. +RÃ¥dets Högoälborne Herr Grefve C. G. Tessins Samling. K. svenska Vet.-Akad. Handl., vol. 20, pp. 21, 22, pl. 1, fig. 1.</p> <p class="larger"><span class="smcap">Matthew, W. D.</span></p> -<p class="references">1893.—On antennæ and other appendages of <i>Triarthrus becki</i>. Amer. Jour. Sci. (3), +<p class="references">1893.—On antennæ and other appendages of <i>Triarthrus becki</i>. Amer. Jour. Sci. (3), vol. 46, pp. 121-125, pl. 1; Trans. New York Acad. Sci., vol. 12, pp. 237-241, pl. a.</p> @@ -9989,26 +9949,26 @@ Soc. Nat. Hist, vol. 2, pp. 217-218, fig.</p> <p class="larger"><span class="smcap">Milne-Edwards, H.</span></p> -<p class="references">1881.—Compte rendu des nouvelles recherches de M. Walcott relatives à la structure des -trilobites, suivi de quelques considérations sur l'interprétation des faits ainsi -constatés. Ann. Sci. Nat, Zoologie, ser. 6, vol. 12, pp. 1-33, pls. 10-12. +<p class="references">1881.—Compte rendu des nouvelles recherches de M. Walcott relatives à la structure des +trilobites, suivi de quelques considérations sur l'interprétation des faits ainsi +constatés. Ann. Sci. Nat, Zoologie, ser. 6, vol. 12, pp. 1-33, pls. 10-12. Paris.</p> <p class="larger"><span class="smcap">Moberg, J. C.</span></p> -<p class="references">1902.—Bidrag till Kännedomen om trilobiternas byggnad. Geol. Fören Förhandl., Bd. +<p class="references">1902.—Bidrag till Kännedomen om trilobiternas byggnad. Geol. Fören Förhandl., Bd. 24, pp. 295-302; pl. 3, text fig. 1.</p> -<p class="references">1907.—Om ett gätfultt fossil frän sveriges olenidskiffer samt en kort ofversigt af viktigase +<p class="references">1907.—Om ett gätfultt fossil frän sveriges olenidskiffer samt en kort ofversigt af viktigase data rorande trilobiternas ventrala skelettdelar. Ibid., Bd. 29, Heft 5, pp. 265-272, pl. 4, fig. 2; pl. 5, fig. 1.</p> <p class="larger"><span class="smcap">Œhlert, D. P.</span></p> -<p class="references">1896.—Résumé des derniers travaux sur l'organisation et le developpement des trilobites. -Bull. Soc. Géol. France, ser. 3, vol. 24, pp. 97-116, text figs. 1-34.</p> +<p class="references">1896.—Résumé des derniers travaux sur l'organisation et le developpement des trilobites. +Bull. Soc. Géol. France, ser. 3, vol. 24, pp. 97-116, text figs. 1-34.</p> <p class="larger"><span class="smcap">Packard, A. H.</span></p> @@ -10023,7 +9983,7 @@ pp. 155-202, pls. 3-5.</p> <p class="larger"><span class="smcap">Pander, C.</span></p> -<p class="references">1830.—Beiträge zur Geognosie des russischen Reiches. St. Petersburg.</p> +<p class="references">1830.—Beiträge zur Geognosie des russischen Reiches. St. Petersburg.</p> <p class="larger"><span class="smcap">Peach, B. N.</span></p> @@ -10031,13 +9991,13 @@ pp. 155-202, pls. 3-5.</p> <p class="references">1882.—On some fossil myriopods from the Lower Old Red Sandstone of Forfarshire. Proc. Roy. Physical Soc., Edinburgh, vol. 7, pp. 177-187, pl. 2.</p> -<p class="references">1899.—O some new myriopods from the Palæozoic rocks of Scotland. Ibid., vol. 14, +<p class="references">1899.—O some new myriopods from the Palæozoic rocks of Scotland. Ibid., vol. 14, pp. 113-126, pl. 4.</p> <p class="larger"><span class="smcap">Quenstedt, A.</span></p> -<p class="references">1837.—Beitrag zur Kenntniss der Trilobiten, mit besonderer Rücksicht auf ihre bestimmte +<p class="references">1837.—Beitrag zur Kenntniss der Trilobiten, mit besonderer Rücksicht auf ihre bestimmte Gliederzahl. Archiv f. Naturg., Berlin, 3. Jahrg., 1 Bd., pp. 337-352.</p> @@ -10065,7 +10025,7 @@ pp. 525-543. pls. 1, 2, 3 text figs. 1-3.</p> <p class="larger"><span class="smcap">Richter, R.</span></p> -<p class="references">1848.—Bitrag zur Palæeontologie des Thüringer Waldes. Dresden and Leipzig.</p> +<p class="references">1848.—Bitrag zur Palæeontologie des Thüringer Waldes. Dresden and Leipzig.</p> <p class="larger"><span class="smcap">Ringueberg, E. N. S.</span></p> @@ -10082,12 +10042,12 @@ pp. 127-143, pls. 34-36.</p> <p class="larger"><span class="smcap">Schlotheim, E. F. von.</span></p> -<p class="references">1823.—Nachträge zur Petrefactenkunde, II. Gotha.</p> +<p class="references">1823.—Nachträge zur Petrefactenkunde, II. Gotha.</p> <p class="larger"><span class="smcap">Six, Achille.</span></p> -<p class="references">1884.—Les appendices des trilobites d'après M. Ch. D. Walcott. Ann. Soc. Geol. du +<p class="references">1884.—Les appendices des trilobites d'après M. Ch. D. Walcott. Ann. Soc. Geol. du Nord, vol. 11, pp. 228-236.</p> @@ -10104,7 +10064,7 @@ Gesell. naturforsch. Freunde, Sitzb., pp. 130-146, figs. 1-20.</p> <p class="larger"><span class="smcap">Sternberg, K. M.</span></p> -<p class="references">1830.—Ueber die Gliederung und die Füsse der Trilobiten. Isis (Encycl. Zeitung), Oken, +<p class="references">1830.—Ueber die Gliederung und die Füsse der Trilobiten. Isis (Encycl. Zeitung), Oken, p. 516, pl. 5, figs. 1-3.</p> @@ -10119,11 +10079,11 @@ p. 516, pl. 5, figs. 1-3.</p> <p class="references">1919.—The facial suture of the trilobite. Geol. Mag., dec. 6, vol. 6, pp. 103-110.</p> -<p class="larger"><span class="smcap">Törnquist, S. L.</span></p> +<p class="larger"><span class="smcap">Törnquist, S. L.</span></p> <p class="references">1896 A.—On the appendages of trilobites. Ibid., dec. 4, vol. 3, p. 142.</p> -<p class="references">1896 B.—Linnæus on the appendages of trilobites. Ibid., pp. 567-569.</p> +<p class="references">1896 B.—Linnæus on the appendages of trilobites. Ibid., pp. 567-569.</p> <p class="larger"><span class="smcap">Tothill, J. D.</span></p> @@ -10153,7 +10113,7 @@ zu St Petersburg, 1857-1858, p. 168.</p> Anhange ueber die Bewegungs-organe und ueber das Herz derselben. Mem. Acad. Imp. Sci. St. Petersburg, ser. 7, vol. 6, No. 2, pp. 44-47, pl. 1, fig. 12.</p> -<p class="references">1866.—Ueber Herrn von Eichwald's Beitrag zu näheren Kenntniss der Illænen. Bull. +<p class="references">1866.—Ueber Herrn von Eichwald's Beitrag zu näheren Kenntniss der Illænen. Bull. Soc. Imp. des Natural, de Moscou, vol. 39, p. 40.</p> @@ -10222,7 +10182,7 @@ p. 94.</p> <p class="references">1884.—Notes on the appendages of trilobites. Geol. Mag., dec. 3, vol. 1, pp. 162-165, 2 text figs.</p> -<p class="references">1895.—Some points in the life history of the Crustacea in early Palæozoic times. Quart. +<p class="references">1895.—Some points in the life history of the Crustacea in early Palæozoic times. Quart. Jour. Geol. Soc., London, vol. 51, pp. lxx-lxxxviii, 1 pl.</p> @@ -10238,23 +10198,23 @@ Jour. Geol. Soc., London, vol. 51, pp. lxx-lxxxviii, 1 pl.</p> <p>Fig. 1. Specimen 213. The dorsal test has been removed from the glabella, revealing the outline of the posterior end of the hypostoma, the proximal ends of the antennules, -the gnathites, and incomplete endopodites of some appendages, × 5.43.</p> +the gnathites, and incomplete endopodites of some appendages, × 5.43.</p> <p>Fig. 2. Specimen 214. The head of a complete large specimen. Part of the thorax is shown on <a href="#Plate_3">pl. 3, fig. 6</a>. Note especially the form of the segments of the endopodites and -of the anterior coxopodite on the right side, × 7.33.</p> +of the anterior coxopodite on the right side, × 7.33.</p> <p>Fig. 3. Specimen 217. This specimen shows better than any other the form of the -gnathites of the cephalon. Note also the setæ of the exopodites under the cheek at the right. +gnathites of the cephalon. Note also the setæ of the exopodites under the cheek at the right. The appearance of a hook on the posterior gnathite on the right may be accidental, but it -does not show broken edges, × 6.85.</p> +does not show broken edges, × 6.85.</p> <p>Fig. 4. Specimen 215. The ventral side of the cephalon of a small entire specimen. Shows well the form of some of the gnathites and a few of the endopodites. Note the -unusual position of the antennules. × 7.63.</p> +unusual position of the antennules. × 7.63.</p> <p>Fig. 5. Specimen 226. This specimen did not photograph well, but is important as -showing the exopodites and endopodites emerging from under the cephalon. × about 6.</p> +showing the exopodites and endopodites emerging from under the cephalon. × about 6.</p> <p><span class="pagenum0"><a name="Page_171" id="Page_171">[171]</a></span></p> @@ -10278,30 +10238,30 @@ showing the exopodites and endopodites emerging from under the cephalon. × about <p>Fig. 1. Specimen 201. The entire specimen, details of which are shown in <a href="#Plate_3">pl. 3, fig. 4</a> and <a href="#Plate_4">pl. 4, figs. 1, 2</a>. The dorsal test has been removed from the anterior segments -on the right side. × 4.12.</p> +on the right side. × 4.12.</p> <p>Fig. 2. Specimen 206. A small individual with the endopodites, and the exopodites -minus their setæ; well preserved on the left side. Note the position of the antennules. The -course of the facial suture is unusually well shown. × 10.</p> +minus their setæ; well preserved on the left side. Note the position of the antennules. The +course of the facial suture is unusually well shown. × 10.</p> <p>Fig. 3. Specimen 210. The specimen which served as the main basis for Professor Beecher's first figure of the appendages of the thorax, specimen 206 (fig. 2, this plate) having supplemented it. Note the "normal" position of the antennules and the extension of the appendages from beneath the pleural lobe. Specimens with the antennules in this position -may possibly be males. × 4.</p> +may possibly be males. × 4.</p> <p>Fig. 4. Specimen 205. A small specimen with some of the appendages preserved, especially toward the posterior end, but particularly valuable for the unusually well preserved -metastoma. × 11.</p> +metastoma. × 11.</p> <p>Fig. 5. Specimen 211. A small cephalon, cleaned from the ventral side, and showing well the gnathites which approach each other unusually closely on the median line. -× 10.5.</p> +× 10.5.</p> <p>Fig. 6. Specimen 219. An entire specimen of medium size, developed from the ventral side. It shows particularly well the "normal" curvature of the antennules, the change in form of the segments of the endopodites from cephalon to pygidium, and, along the axial -lobe, the apodemes of the ventral integument. See also <a href="#Plate_4">pl. 4, fig. 4</a>. × 3.6.</p> +lobe, the apodemes of the ventral integument. See also <a href="#Plate_4">pl. 4, fig. 4</a>. × 3.6.</p> <p><span class="pagenum0"><a name="Page_175" id="Page_175">[175]</a></span></p> @@ -10325,26 +10285,26 @@ lobe, the apodemes of the ventral integument. See also <a href="#Plate_4">pl. 4, <p>Fig. 1. Specimen 204. See also text <a href="#fig_42">fig. 42</a> and <a href="#Plate_4">pl. 4, fig. 6</a>. The exopodites and endopodites of the first few segments of this specimen are better preserved than those of -any other revealing them from the dorsal side, × 9.5.</p> +any other revealing them from the dorsal side, × 9.5.</p> <p>Fig. 2. Specimen 220. A large individual exposed from the lower side. It shows well the endopodites and part of the exopodites, and, rather better than any other specimen, -the endobases of the coxopodites. × 2.4.</p> +the endobases of the coxopodites. × 2.4.</p> <p>Fig. 3. Specimen 216. A small entire specimen showing considerable of the detail of -the appendages of the cephalon, and some of those of the remainder of the body, × 7.4.</p> +the appendages of the cephalon, and some of those of the remainder of the body, × 7.4.</p> <p>Fig. 4. Specimen 201. This figure shows the details of the appendages of the left side and of the pygidium. Note the plate on the median line back of the pygidium, the sockets for spines, and the terminal spines on the anterior endopodites. See also <a href="#Plate_2">pl. 2, fig. -1</a> and <a href="#Plate_4">pl. 4, figs. 1, 2</a>. × 7.1.</p> +1</a> and <a href="#Plate_4">pl. 4, figs. 1, 2</a>. × 7.1.</p> <p>Fig. 5. Specimen 207. One half of the posterior part of the thorax and pygidium, -showing exopodites and endopodites as seen from the dorsal side, × 7.6.</p> +showing exopodites and endopodites as seen from the dorsal side, × 7.6.</p> <p>Fig. 6. Specimen 214. The exopodites have been turned back nearly parallel to the -axis of the shell. Notice particularly the long flattened setæ and the spinose spatula-shaped -terminal portion of each shaft. See also <a href="#Plate_1">pl. 1, fig. 2</a>. × 7.</p> +axis of the shell. Notice particularly the long flattened setæ and the spinose spatula-shaped +terminal portion of each shaft. See also <a href="#Plate_1">pl. 1, fig. 2</a>. × 7.</p> <p><span class="pagenum0"><a name="Page_179" id="Page_179">[179]</a></span></p> @@ -10367,27 +10327,27 @@ terminal portion of each shaft. See also <a href="#Plate_1">pl. 1, fig. 2</a>. × <p>Photographs of <i>Triarthrus becki</i>, made by C. E. Beecher.</p> <p>Fig. 1. Specimen 201. Another photograph, similar to <a href="#Plate_3">fig. 4, pl. 3</a>, but showing more -clearly some details of spines on the endopodites. × 12.66.</p> +clearly some details of spines on the endopodites. × 12.66.</p> <p>Fig. 2. Specimen 201. Three appendages on the right side of the thorax. See also -<a href="#Plate_2">pl. 2, fig. 1</a> and <a href="#Plate_3">pl. 3, fig. 4</a>. × 12.66.</p> +<a href="#Plate_2">pl. 2, fig. 1</a> and <a href="#Plate_3">pl. 3, fig. 4</a>. × 12.66.</p> <p>Fig. 3. Specimen 223. A small crushed specimen which nevertheless shows well the appendages of the right side of the thorax, developed from the ventral side. Note coxopodites, exopodites, and endopodites, and that all appendages are moved equally laterally from -their original position. × 11.4.</p> +their original position. × 11.4.</p> <p>Fig. 4. Specimen 219. Another photograph, with different lighting, of the individual shown in <a href="#Plate_2">pl. 2, fig. 6</a>. This print brings out better the coxopodites and the folds of the -ventral membrane. × 3.23.</p> +ventral membrane. × 3.23.</p> <p>Fig. 5. Specimen 222. This specimen is interesting, because it shows the endopodites in what is probably their natural position, that is, in a plane nearly vertical to the plane of the body, instead of being flattened down, as is usually the case. The appendages under -the pygidium are unusually well preserved. × 12.</p> +the pygidium are unusually well preserved. × 12.</p> <p>Fig. 6. Specimen 204. Photograph of the entire specimen of which a part is shown -in text <a href="#fig_42">fig. 42</a> and <a href="#Plate_3">pl. 3, fig. 1</a>. × 4.5.</p> +in text <a href="#fig_42">fig. 42</a> and <a href="#Plate_3">pl. 3, fig. 1</a>. × 4.5.</p> <p><span class="pagenum0"><a name="Page_183" id="Page_183">[183]</a></span></p> @@ -10411,30 +10371,30 @@ in text <a href="#fig_42">fig. 42</a> and <a href="#Plate_3">pl. 3, fig. 1</a>. <p>Fig. 1. Specimen 209. Photograph of the pygidium shown in <a href="#Plate_6">pl. 6, fig. 2</a>. This specimen shows especially well the way in which the exopodites of the pygidium decrease -in length backward, × 11.5.</p> +in length backward, × 11.5.</p> <p>Fig. 2. Specimen 229. The under side of the posterior end of a medium-sized specimen, showing the appendages, especially the endopodites. On and among the limbs are scattered numerous minute spheres of pyrite, of the kind usually known as "trilobite eggs." They do not show very well in the photograph, but can be made out much more clearly -with a hand lens, × 12.</p> +with a hand lens, × 12.</p> <p>Fig. 3. Specimen 230. A specimen showing the appendages of the posterior part of the thorax and the pygidium. The same individual is also shown in text <a href="#fig_44">fig. 44</a>. Note -particularly the form of the segments of the endopodites, and the spines on them, × 13.</p> +particularly the form of the segments of the endopodites, and the spines on them, × 13.</p> <p>Fig. 4. Specimen 227. The small doubly curved bodies shown in this figure lie under the axial portion of the cephalon and anterior part of the thorax. The specimen still has a very thin coating of matrix between it and the shell. Whether the curved bodies have -anything to do with the trilobite is not known, × about 12.</p> +anything to do with the trilobite is not known, × about 12.</p> <p>Fig. 5. Specimen 221. A small individual which shows well the exopodites of the posterior part of the thorax. Note the spatulate terminations and the spines of the shaft, -× 11.</p> +× 11.</p> <p>Fig. 6. Specimen 202. Posterior part of the thorax and pygidium, showing endopodites and exopodites projecting under the dorsal test. Note the spiniferous plate on the median -line, and the large opening in the anterior portion of it. × 9.75</p> +line, and the large opening in the anterior portion of it. × 9.75</p> <p><span class="pagenum0"><a name="Page_187" id="Page_187">[187]</a></span></p> @@ -10457,16 +10417,16 @@ line, and the large opening in the anterior portion of it. × 9.75</p> <p>All figures except 4 and 5, from photographs by C. E. Beecher.</p> <p>Fig. 1. <i>Triarthrus becki</i>. Specimen 203. A well preserved small individual, showing -the appendages of the right side of the thorax. × 11.46.</p> +the appendages of the right side of the thorax. × 11.46.</p> <p>Fig. 2. <i>Triarthrus becki</i>. Specimen 209. A well preserved individual, showing the antennules and some appendages of thorax and pygidium. For detail of the pygidium, see -<a href="#Plate_5">pl. 5, fig. 1</a>. × 4.</p> +<a href="#Plate_5">pl. 5, fig. 1</a>. × 4.</p> <p>Fig. 3. <i>Triarthrus becki</i>. Specimen 218. Ventral side of the pygidium and greater part of the thorax of an individual of medium size. Note especially the relation of exopodites to endopodites of the last two thoracic segments. A drawing of these appendages is -shown on text <a href="#fig_43">fig. 43</a>. × 4,3.</p> +shown on text <a href="#fig_43">fig. 43</a>. × 4,3.</p> <p>Figs. 4 and 5. Endopodites, probably from a species of <i>Calymene</i>. These specimens, with several others, are on a small slab of limestone from the Point Pleasant (Trenton) beds @@ -10475,11 +10435,11 @@ Bassler.</p> <p>Fig. 6. <i>Acidaspis trentonensis</i> Walcott. Both the specimen, No. 245, and the photograph are poor, but show that in this genus the endopodites are like those of Triarthrus. -× 8.5.</p> +× 8.5.</p> <p>Fig. 7. <i>Cryptolithus tessellatus</i> Green. Specimen 234. This specimen shows well the backward directed antennules and also the outer segments of some of the cephalic endopodites. -× 11.</p> +× 11.</p> <p><span class="pagenum"><a name="Page_191" id="Page_191">[191]</a></span></p> @@ -10506,23 +10466,23 @@ Beecher's drawing (text fig. 45) was made, and which served as the principal bas restoration (text fig. 20). Note the long, backward directed antennules, the abrupt backward turn of the outer portions of the endopodites, the way in which the exopodites extend beyond the endopodites, and the fact that alt are beneath the cover of the dorsal shield. -The hypostoma is turned entirely around. × 10.9.</p> +The hypostoma is turned entirely around. × 10.9.</p> <p>Fig. 2. Specimen 235. Half of the thorax and pygidium, with the appendages revealed from the ventral side. Note the abrupt manner in which the outer portions of the -endopodites are turned backward. See also <a href="#Plate_8">pl. 8, fig. 3</a>, and <a href="#Plate_9">pl. 9, fig. 1</a> (right half). × 14.45.</p> +endopodites are turned backward. See also <a href="#Plate_8">pl. 8, fig. 3</a>, and <a href="#Plate_9">pl. 9, fig. 1</a> (right half). × 14.45.</p> -<p>Fig. 3. Specimen 236. Detail from fig. 4, to show the blade-like setæ of the exopodites -and the numerous terminal spines of the endopodites. × 30.</p> +<p>Fig. 3. Specimen 236. Detail from fig. 4, to show the blade-like setæ of the exopodites +and the numerous terminal spines of the endopodites. × 30.</p> <p>Fig. 4. Specimen 236. The appendages of the thorax and pygidium, seen from the lower side. Specimen 236 is the right half of the same individual from which specimen 235 was obtained. Note the interarticular membranes between the segments of the endopodites -and the blade-like setæ of the exopodites. See also <a href="#Plate_9">pl. 9, fig. 1</a> (left side). × 19.</p> +and the blade-like setæ of the exopodites. See also <a href="#Plate_9">pl. 9, fig. 1</a> (left side). × 19.</p> <p>Fig. 5. Specimen 236. The same specimen, seen from the dorsal side, showing, when -the test is removed, the long blade-like setæ of the exopodites. See also <a href="#Plate_9">pl. 9, fig. 2</a> (right -half). × 19.</p> +the test is removed, the long blade-like setæ of the exopodites. See also <a href="#Plate_9">pl. 9, fig. 2</a> (right +half). × 19.</p> <p><span class="pagenum"><a name="Page_195" id="Page_195">[195]</a></span></p> @@ -10546,23 +10506,23 @@ half). × 19.</p> <p>Fig. 1. Specimen 231. A nearly complete individual, cleaned from the ventral side and showing obscurely the hypostoma and fragments of numerous appendages. Note the -lines of appendifers along the sides of the axial lobe. × 11.</p> +lines of appendifers along the sides of the axial lobe. × 11.</p> <p>Fig. 2. Specimen 232. Although this is not very well preserved, it shows more of the cephalic appendages than any other. Even so, only just enough is shown to indicate -that they were similar to those on the thorax. × 12.</p> +that they were similar to those on the thorax. × 12.</p> <p>Fig. 3. Specimen 235. Dorsal side of the appendages of the thorax and pygidium. See <a href="#Plate_7">pl. 7, fig. 2</a> for the ventral view. On <a href="#Plate_9">pl. 9, fig. 2</a> (left side) is a drawing taken from -the same specimen. × 11.</p> +the same specimen. × 11.</p> <p>Fig. 4. Specimen 238. Part of a thorax and pygidium, seen from the ventral side. The series of heavy segments shown in the upper part do not belong to one appendage, but are the distal ends of several endopodites. See also text <a href="#fig_46">fig. 46</a> for a drawing of this specimen. -× 18.</p> +× 18.</p> <p>Fig. 5. Specimen 237. Pygidium and part of the thorax, with some of the appendages. -× 11.</p> +× 11.</p> <p><span class="pagenum"><a name="Page_199" id="Page_199">[199]</a></span></p> @@ -10587,10 +10547,10 @@ F. E. Isham, under the direction of C. E. Beecher.</p> <p>Fig. 1. Appendages of the thorax and pygidium, seen from the ventral side. These are not restorations, but drawings from the halved individual numbered 236 (right side of -drawing) and 235. For photographs of these specimens, see <a href="#Plate_7">pl. 7, figs. 2, 4</a>. × 20.</p> +drawing) and 235. For photographs of these specimens, see <a href="#Plate_7">pl. 7, figs. 2, 4</a>. × 20.</p> <p>Fig. 2. Appendages of the thorax and pygidium, seen from the dorsal side. Same -specimen as in fig. 1. For photographs, see <a href="#Plate_7">pl. 7, fig. 5</a>, and <a href="#Plate_8">pl. 8, fig. 3</a>. × 20.</p> +specimen as in fig. 1. For photographs, see <a href="#Plate_7">pl. 7, fig. 5</a>, and <a href="#Plate_8">pl. 8, fig. 3</a>. × 20.</p> <p><span class="pagenum"><a name="Page_203" id="Page_203">[203]</a></span></p> @@ -10616,13 +10576,13 @@ specimen as in fig. 1. For photographs, see <a href="#Plate_7">pl. 7, fig. 5</a> Memorial Museum at Ottawa, Canada. Note the large, club-shaped coxopodites and the more slender endopodites. The first large coxopodite back of the hypostoma belongs to the last pair of cephalic appendages. The coxopodite of the appendage in front of it is seen -turning in beneath the tip of the hypostoma. × 2.</p> +turning in beneath the tip of the hypostoma. × 2.</p> <p>Fig. 2. <i>Isotelus maximus</i> Locke. The ventral side of the specimen described by Mickleborough and now in the U. S. National Museum. The tips of the hypostoma may be seen at the front, and the first two pairs of coxopodites behind them belong to the last two pairs of appendages of the cephalon. Note how much stronger the coxopodites are than the endopodites. -The appendages of the pygidium show but poorly, × 1.45.</p> +The appendages of the pygidium show but poorly, × 1.45.</p> <p><span class="pagenum"><a name="Page_207" id="Page_207">[207]</a></span></p> @@ -10644,7 +10604,7 @@ The appendages of the pygidium show but poorly, × 1.45.</p> <p><i>Ceraurus pleurexanthemus</i> Green. A restoration of the ventral surface and appendages, made by Doctor Elvira Wood, under the supervision of the writer, from data obtained -from the translucent slices prepared and described by Doctor Walcott. × 5.</p> +from the translucent slices prepared and described by Doctor Walcott. × 5.</p> <p><span class="pagenum"><a name="Page_211" id="Page_211">[211]</a></span></p> @@ -10661,382 +10621,6 @@ from the translucent slices prepared and described by Doctor Walcott. × 5.</p> <hr class="tb" /> - - - - - - - - -<pre> - - - - - -End of the Project Gutenberg EBook of The Appendages, Anatomy, and -Relationships of Trilobites, by Percy Edward Raymond - -*** END OF THIS PROJECT GUTENBERG EBOOK TRILOBITES *** - -***** This file should be named 41695-h.htm or 41695-h.zip ***** -This and all associated files of various formats will be found in: - http://www.gutenberg.org/4/1/6/9/41695/ - -Produced by Thomas Cosmas. Produced from files made -available on The Internet Archive. - - -Updated editions will replace the previous one--the old editions -will be renamed. - -Creating the works from public domain print editions means that no -one owns a United States copyright in these works, so the Foundation -(and you!) can copy and distribute it in the United States without -permission and without paying copyright royalties. Special rules, -set forth in the General Terms of Use part of this license, apply to -copying and distributing Project Gutenberg-tm electronic works to -protect the PROJECT GUTENBERG-tm concept and trademark. Project -Gutenberg is a registered trademark, and may not be used if you -charge for the eBooks, unless you receive specific permission. If you -do not charge anything for copies of this eBook, complying with the -rules is very easy. You may use this eBook for nearly any purpose -such as creation of derivative works, reports, performances and -research. They may be modified and printed and given away--you may do -practically ANYTHING with public domain eBooks. Redistribution is -subject to the trademark license, especially commercial -redistribution. - - - -*** START: FULL LICENSE *** - -THE FULL PROJECT GUTENBERG LICENSE -PLEASE READ THIS BEFORE YOU DISTRIBUTE OR USE THIS WORK - -To protect the Project Gutenberg-tm mission of promoting the free -distribution of electronic works, by using or distributing this work -(or any other work associated in any way with the phrase "Project -Gutenberg"), you agree to comply with all the terms of the Full Project -Gutenberg-tm License available with this file or online at - www.gutenberg.org/license. - - -Section 1. General Terms of Use and Redistributing Project Gutenberg-tm -electronic works - -1.A. By reading or using any part of this Project Gutenberg-tm -electronic work, you indicate that you have read, understand, agree to -and accept all the terms of this license and intellectual property -(trademark/copyright) agreement. If you do not agree to abide by all -the terms of this agreement, you must cease using and return or destroy -all copies of Project Gutenberg-tm electronic works in your possession. -If you paid a fee for obtaining a copy of or access to a Project -Gutenberg-tm electronic work and you do not agree to be bound by the -terms of this agreement, you may obtain a refund from the person or -entity to whom you paid the fee as set forth in paragraph 1.E.8. - -1.B. "Project Gutenberg" is a registered trademark. It may only be -used on or associated in any way with an electronic work by people who -agree to be bound by the terms of this agreement. There are a few -things that you can do with most Project Gutenberg-tm electronic works -even without complying with the full terms of this agreement. See -paragraph 1.C below. There are a lot of things you can do with Project -Gutenberg-tm electronic works if you follow the terms of this agreement -and help preserve free future access to Project Gutenberg-tm electronic -works. See paragraph 1.E below. - -1.C. The Project Gutenberg Literary Archive Foundation ("the Foundation" -or PGLAF), owns a compilation copyright in the collection of Project -Gutenberg-tm electronic works. Nearly all the individual works in the -collection are in the public domain in the United States. If an -individual work is in the public domain in the United States and you are -located in the United States, we do not claim a right to prevent you from -copying, distributing, performing, displaying or creating derivative -works based on the work as long as all references to Project Gutenberg -are removed. Of course, we hope that you will support the Project -Gutenberg-tm mission of promoting free access to electronic works by -freely sharing Project Gutenberg-tm works in compliance with the terms of -this agreement for keeping the Project Gutenberg-tm name associated with -the work. You can easily comply with the terms of this agreement by -keeping this work in the same format with its attached full Project -Gutenberg-tm License when you share it without charge with others. - -1.D. The copyright laws of the place where you are located also govern -what you can do with this work. Copyright laws in most countries are in -a constant state of change. If you are outside the United States, check -the laws of your country in addition to the terms of this agreement -before downloading, copying, displaying, performing, distributing or -creating derivative works based on this work or any other Project -Gutenberg-tm work. The Foundation makes no representations concerning -the copyright status of any work in any country outside the United -States. - -1.E. Unless you have removed all references to Project Gutenberg: - -1.E.1. The following sentence, with active links to, or other immediate -access to, the full Project Gutenberg-tm License must appear prominently -whenever any copy of a Project Gutenberg-tm work (any work on which the -phrase "Project Gutenberg" appears, or with which the phrase "Project -Gutenberg" is associated) is accessed, displayed, performed, viewed, -copied or distributed: - -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 - -1.E.2. If an individual Project Gutenberg-tm electronic work is derived -from the public domain (does not contain a notice indicating that it is -posted with permission of the copyright holder), the work can be copied -and distributed to anyone in the United States without paying any fees -or charges. If you are redistributing or providing access to a work -with the phrase "Project Gutenberg" associated with or appearing on the -work, you must comply either with the requirements of paragraphs 1.E.1 -through 1.E.7 or obtain permission for the use of the work and the -Project Gutenberg-tm trademark as set forth in paragraphs 1.E.8 or -1.E.9. - -1.E.3. If an individual Project Gutenberg-tm electronic work is posted -with the permission of the copyright holder, your use and distribution -must comply with both paragraphs 1.E.1 through 1.E.7 and any additional -terms imposed by the copyright holder. Additional terms will be linked -to the Project Gutenberg-tm License for all works posted with the -permission of the copyright holder found at the beginning of this work. - -1.E.4. Do not unlink or detach or remove the full Project Gutenberg-tm -License terms from this work, or any files containing a part of this -work or any other work associated with Project Gutenberg-tm. - -1.E.5. Do not copy, display, perform, distribute or redistribute this -electronic work, or any part of this electronic work, without -prominently displaying the sentence set forth in paragraph 1.E.1 with -active links or immediate access to the full terms of the Project -Gutenberg-tm License. - -1.E.6. You may convert to and distribute this work in any binary, -compressed, marked up, nonproprietary or proprietary form, including any -word processing or hypertext form. However, if you provide access to or -distribute copies of a Project Gutenberg-tm work in a format other than -"Plain Vanilla ASCII" or other format used in the official version -posted on the official Project Gutenberg-tm web site (www.gutenberg.org), -you must, at no additional cost, fee or expense to the user, provide a -copy, a means of exporting a copy, or a means of obtaining a copy upon -request, of the work in its original "Plain Vanilla ASCII" or other -form. Any alternate format must include the full Project Gutenberg-tm -License as specified in paragraph 1.E.1. - -1.E.7. Do not charge a fee for access to, viewing, displaying, -performing, copying or distributing any Project Gutenberg-tm works -unless you comply with paragraph 1.E.8 or 1.E.9. - -1.E.8. You may charge a reasonable fee for copies of or providing -access to or distributing Project Gutenberg-tm electronic works provided -that - -- You pay a royalty fee of 20% of the gross profits you derive from - the use of Project Gutenberg-tm works calculated using the method - you already use to calculate your applicable taxes. The fee is - owed to the owner of the Project Gutenberg-tm trademark, but he - has agreed to donate royalties under this paragraph to the - Project Gutenberg Literary Archive Foundation. Royalty payments - must be paid within 60 days following each date on which you - prepare (or are legally required to prepare) your periodic tax - returns. Royalty payments should be clearly marked as such and - sent to the Project Gutenberg Literary Archive Foundation at the - address specified in Section 4, "Information about donations to - the Project Gutenberg Literary Archive Foundation." - -- You provide a full refund of any money paid by a user who notifies - you in writing (or by e-mail) within 30 days of receipt that s/he - does not agree to the terms of the full Project Gutenberg-tm - License. You must require such a user to return or - destroy all copies of the works possessed in a physical medium - and discontinue all use of and all access to other copies of - Project Gutenberg-tm works. - -- You provide, in accordance with paragraph 1.F.3, a full refund of any - money paid for a work or a replacement copy, if a defect in the - electronic work is discovered and reported to you within 90 days - of receipt of the work. - -- You comply with all other terms of this agreement for free - distribution of Project Gutenberg-tm works. - -1.E.9. If you wish to charge a fee or distribute a Project Gutenberg-tm -electronic work or group of works on different terms than are set -forth in this agreement, you must obtain permission in writing from -both the Project Gutenberg Literary Archive Foundation and Michael -Hart, the owner of the Project Gutenberg-tm trademark. Contact the -Foundation as set forth in Section 3 below. - -1.F. - -1.F.1. Project Gutenberg volunteers and employees expend considerable -effort to identify, do copyright research on, transcribe and proofread -public domain works in creating the Project Gutenberg-tm -collection. Despite these efforts, Project Gutenberg-tm electronic -works, and the medium on which they may be stored, may contain -"Defects," such as, but not limited to, incomplete, inaccurate or -corrupt data, transcription errors, a copyright or other intellectual -property infringement, a defective or damaged disk or other medium, a -computer virus, or computer codes that damage or cannot be read by -your equipment. - -1.F.2. LIMITED WARRANTY, DISCLAIMER OF DAMAGES - Except for the "Right -of Replacement or Refund" described in paragraph 1.F.3, the Project -Gutenberg Literary Archive Foundation, the owner of the Project -Gutenberg-tm trademark, and any other party distributing a Project -Gutenberg-tm electronic work under this agreement, disclaim all -liability to you for damages, costs and expenses, including legal -fees. YOU AGREE THAT YOU HAVE NO REMEDIES FOR NEGLIGENCE, STRICT -LIABILITY, BREACH OF WARRANTY OR BREACH OF CONTRACT EXCEPT THOSE -PROVIDED IN PARAGRAPH 1.F.3. YOU AGREE THAT THE FOUNDATION, THE -TRADEMARK OWNER, AND ANY DISTRIBUTOR UNDER THIS AGREEMENT WILL NOT BE -LIABLE TO YOU FOR ACTUAL, DIRECT, INDIRECT, CONSEQUENTIAL, PUNITIVE OR -INCIDENTAL DAMAGES EVEN IF YOU GIVE NOTICE OF THE POSSIBILITY OF SUCH -DAMAGE. - -1.F.3. LIMITED RIGHT OF REPLACEMENT OR REFUND - If you discover a -defect in this electronic work within 90 days of receiving it, you can -receive a refund of the money (if any) you paid for it by sending a -written explanation to the person you received the work from. If you -received the work on a physical medium, you must return the medium with -your written explanation. The person or entity that provided you with -the defective work may elect to provide a replacement copy in lieu of a -refund. If you received the work electronically, the person or entity -providing it to you may choose to give you a second opportunity to -receive the work electronically in lieu of a refund. If the second copy -is also defective, you may demand a refund in writing without further -opportunities to fix the problem. - -1.F.4. Except for the limited right of replacement or refund set forth -in paragraph 1.F.3, this work is provided to you 'AS-IS', WITH NO OTHER -WARRANTIES OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO -WARRANTIES OF MERCHANTABILITY OR FITNESS FOR ANY PURPOSE. - -1.F.5. Some states do not allow disclaimers of certain implied -warranties or the exclusion or limitation of certain types of damages. -If any disclaimer or limitation set forth in this agreement violates the -law of the state applicable to this agreement, the agreement shall be -interpreted to make the maximum disclaimer or limitation permitted by -the applicable state law. The invalidity or unenforceability of any -provision of this agreement shall not void the remaining provisions. - -1.F.6. INDEMNITY - You agree to indemnify and hold the Foundation, the -trademark owner, any agent or employee of the Foundation, anyone -providing copies of Project Gutenberg-tm electronic works in accordance -with this agreement, and any volunteers associated with the production, -promotion and distribution of Project Gutenberg-tm electronic works, -harmless from all liability, costs and expenses, including legal fees, -that arise directly or indirectly from any of the following which you do -or cause to occur: (a) distribution of this or any Project Gutenberg-tm -work, (b) alteration, modification, or additions or deletions to any -Project Gutenberg-tm work, and (c) any Defect you cause. - - -Section 2. Information about the Mission of Project Gutenberg-tm - -Project Gutenberg-tm is synonymous with the free distribution of -electronic works in formats readable by the widest variety of computers -including obsolete, old, middle-aged and new computers. It exists -because of the efforts of hundreds of volunteers and donations from -people in all walks of life. - -Volunteers and financial support to provide volunteers with the -assistance they need are critical to reaching Project Gutenberg-tm's -goals and ensuring that the Project Gutenberg-tm collection will -remain freely available for generations to come. In 2001, the Project -Gutenberg Literary Archive Foundation was created to provide a secure -and permanent future for Project Gutenberg-tm and future generations. -To learn more about the Project Gutenberg Literary Archive Foundation -and how your efforts and donations can help, see Sections 3 and 4 -and the Foundation information page at www.gutenberg.org - - -Section 3. Information about the Project Gutenberg Literary Archive -Foundation - -The Project Gutenberg Literary Archive Foundation is a non profit -501(c)(3) educational corporation organized under the laws of the -state of Mississippi and granted tax exempt status by the Internal -Revenue Service. The Foundation's EIN or federal tax identification -number is 64-6221541. Contributions to the Project Gutenberg -Literary Archive Foundation are tax deductible to the full extent -permitted by U.S. federal laws and your state's laws. - -The Foundation's principal office is located at 4557 Melan Dr. S. -Fairbanks, AK, 99712., but its volunteers and employees are scattered -throughout numerous locations. Its business office is located at 809 -North 1500 West, Salt Lake City, UT 84116, (801) 596-1887. Email -contact links and up to date contact information can be found at the -Foundation's web site and official page at www.gutenberg.org/contact - -For additional contact information: - Dr. Gregory B. Newby - Chief Executive and Director - gbnewby@pglaf.org - -Section 4. Information about Donations to the Project Gutenberg -Literary Archive Foundation - -Project Gutenberg-tm depends upon and cannot survive without wide -spread public support and donations to carry out its mission of -increasing the number of public domain and licensed works that can be -freely distributed in machine readable form accessible by the widest -array of equipment including outdated equipment. Many small donations -($1 to $5,000) are particularly important to maintaining tax exempt -status with the IRS. - -The Foundation is committed to complying with the laws regulating -charities and charitable donations in all 50 states of the United -States. Compliance requirements are not uniform and it takes a -considerable effort, much paperwork and many fees to meet and keep up -with these requirements. We do not solicit donations in locations -where we have not received written confirmation of compliance. To -SEND DONATIONS or determine the status of compliance for any -particular state visit www.gutenberg.org/donate - -While we cannot and do not solicit contributions from states where we -have not met the solicitation requirements, we know of no prohibition -against accepting unsolicited donations from donors in such states who -approach us with offers to donate. - -International donations are gratefully accepted, but we cannot make -any statements concerning tax treatment of donations received from -outside the United States. U.S. laws alone swamp our small staff. - -Please check the Project Gutenberg Web pages for current donation -methods and addresses. Donations are accepted in a number of other -ways including checks, online payments and credit card donations. -To donate, please visit: www.gutenberg.org/donate - - -Section 5. General Information About Project Gutenberg-tm electronic -works. - -Professor Michael S. Hart was the originator of the Project Gutenberg-tm -concept of a library of electronic works that could be freely shared -with anyone. For forty years, he produced and distributed Project -Gutenberg-tm eBooks with only a loose network of volunteer support. - -Project Gutenberg-tm eBooks are often created from several printed -editions, all of which are confirmed as Public Domain in the U.S. -unless a copyright notice is included. Thus, we do not necessarily -keep eBooks in compliance with any particular paper edition. - -Most people start at our Web site which has the main PG search facility: - - www.gutenberg.org - -This Web site includes information about Project Gutenberg-tm, -including how to make donations to the Project Gutenberg Literary -Archive Foundation, how to help produce our new eBooks, and how to -subscribe to our email newsletter to hear about new eBooks. - - -</pre> - +<div>*** END OF THE PROJECT GUTENBERG EBOOK 41695 ***</div> </body> </html> |