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diff --git a/old/3772-h/files/ch21.html b/old/3772-h/files/ch21.html new file mode 100644 index 0000000..0b136d2 --- /dev/null +++ b/old/3772-h/files/ch21.html @@ -0,0 +1,997 @@ +<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> +<!-- saved from url=(0036)http://../Lyell/The Student's Elements of Geology --> +<html> +<head> +<meta name="generator" content="HTML Tidy, see www.w3.org"> +<title>The Student's Elements of Geology: Title</title> +<meta content="text/html; charset=iso-8859-1" http-equiv= +"Content-Type"> +<meta content="MSHTML 5.00.2919.6307" name="GENERATOR"> +<link rel="stylesheet" href="geology.css" type="text/css"> +</head> +<body> +<p><b>The Student’s Elements of Geology</b></p> + +<hr> +<p class="page"><a name="page 366">[ 366 ]</a></p> + +<p> </p> + +<center><b>Chapter XXI</b><br> +<br> +TRIAS, OR NEW RED SANDSTONE GROUP.</center> + +<p class="intro">Beds of Passage between the Lias and Trias, +Rhætic Beds. — Triassic Mammifer. — Triple +Division of the Trias. — Keuper, or Upper Trias of England. +— Reptiles of the Upper Trias. — Foot-prints in the +Bunter formation in England. — Dolomitic Conglomerate of +Bristol. — Origin of Red Sandstone and Rock-salt. — +Precipitation of Salt from inland Lakes and Lagoons. — Trias +of Germany. — Keuper. — St. Cassian and Hallstadt Beds. +— Peculiarity of their Fauna. — Muschelkalk and its +Fossils. — Trias of the United States. — Fossil +Foot-prints of Birds and Reptiles in the Valley of the Connecticut. +— Triassic Mammifer of North Carolina. — Triassic +Coal-field of Richmond, Virginia. — Low Grade of early +Mammals favourable to the Theory of Progressive Development.</p> + +<p><b>Beds of Passage between the Lias and Trias—Rhætic +Beds.</b>—We have mentioned in the last chapter (<a href= +"ch20.html#page 356">p. 356</a>) that the base of the Lower Lias is +characterised, both in England and Germany, by beds containing +distinct species of Ammonites, the lowest subdivision having been +called the zone of <i>Ammonites planorbis.</i> Below this zone, on +the boundary line between the Lias and the strata of which we are +about to treat, called “Trias,” certain cream-coloured +limestones devoid of fossils are usually found. These white beds +were called by William Smith the White Lias, and they have been +shown by Mr. Charles Moore to belong to a formation similar to one +in the Rhætian Alps of Bavaria, to which Mr. Gumbel has +applied the name of Rhætic. They have also long been known as +the Koessen beds in Germany, and may be regarded as beds of passage +between the Lias and Trias. They are named the Penarth beds by the +Government surveyors of Great Britain, from Penarth, near Cardiff, +in Glamorganshire, where they sometimes attain a thickness of fifty +feet.</p> + +<p>The principal member of this group has been called by Dr. Wright +the <i>Avicula contorta</i> bed,* as this shell is very abundant, +and has a wide range in Europe. General Portlock first described +the formation as it occurs at Portrush, in Antrim, where the <i> +Avicula contorta</i> is accompanied by <i>Pecten Valoniensis,</i> +as in Germany.</p> + +<p>The best known member of the group, a thin band or bone-breccia, +is conspicuous among the black shales in the neigh-</p> + +<p class="fnote">* Dr. Wright, on Lias and Bone Bed, Quart. Geol. +Journ., 1860, vol. xvi.</p> + +<p> </p> + +<hr> +<p class="page"><a name="page 367">[ 367 ]</a></p> + +<p>bourhood of Axmouth in Devonshire, and in the cliffs of +Westbury-on-Severn, as well as at Aust and other places on the +borders of the Bristol Channel. It abounds in the remains of +saurians and fish, and was formerly classed as the lowest bed of +the Lias; but Sir P. Egerton first pointed out, in 1841, that it +should be referred to the Upper New Red Sandstone, because it +contained an assemblage of fossil fish which are either peculiar to +this stratum, or belong to species well-known in the Muschelkalk of +Germany. These fish belong to the genera <i>Acrodus, Hybodus, +Gyrolepis,</i> and <i>Saurichthys.</i></p> + +<center><img src="../images3/fig383.jpg" width="407" height="410" alt= +"Fig. 383: Cardium rhæticum. Fig. 384: Pecten Valoniensis. Fig. 385: Avicula contorta. Fig. 386: Hybodus plica ilis. Fig. 387: Saurichthys apicalis. Fig. 388: Gyrolepsis tenuistriatus."> +</center> + +<p>Among those common to the English bone-bed and the Muschelkalk +of Germany are <i>Hybodus plicatilis</i> (Fig. 386), <i>Saurychthys +apicalis</i> (Fig. 387), <i>Gyrolepis tenuistriatus</i> (Fig. 388), +and <i>G. Albertii.</i> Remains of saurians, <i>Plesiosaurus</i> +among others, have also been found in the bone-bed, and plates of +an <i>Encrinus.</i> It may be questioned whether some of those +fossils which have the most Triassic character may</p> + +<p> </p> + +<hr> +<p class="page"><a name="page 368">[ 368 ]</a></p> + +<p>not have been derived from the destruction of older strata, +since in bone-beds, in general, many of the organic remains are +undoubtedly derivative.</p> + +<img src="../images3/fig389.jpg" width="246" height="158" alt= +"Fig. 389: Microlestes antiquus, molar tooth." align="left"> + +<p><i>Triassic Mammifer.</i>—In North-western Germany, as in +England, there occurs beneath the Lias a remarkable bone breccia. +It is filled with shells and with the remains of fishes and +reptiles, almost all the genera of which, and some even of the +species, agree with those of the subjacent Trias. This breccia has +accordingly been considered by Professor Quenstedt, and other +German geologists of high authority, as the newest or uppermost +part of the Trias. Professor Plieninger found in it, in 1847, the +molar tooth of a small Triassic mammifer, called by him <i> +Microlestes antiquus.</i> He inferred its true nature from its +double fangs, and from the form and number of the protuberances or +cusps on the flat crown; and considering it as predaceous, probably +insectivorous, he called it <i>Microlestes</i> from micros, little, +and lestes, a beast of prey. Soon afterwards he found a second +tooth, also at the same locality, Diegerloch, about two miles to +the south-east of Stuttgart.</p> + +<p>No anatomist had been able to give any feasible conjecture as to +the affinities of this minute quadruped until Dr. Falconer, in +1857, recognised an unmistakable resemblance between its teeth and +the two back molars of his new genus <i>Plagiaulax</i> (<a href= +"../images2/fig306.jpg">Fig. 306</a>), from the Purbeck strata. This +would lead us to the conclusion that Microlestes was marsupial and +plant-eating.</p> + +<p>In Würtemberg there are two bone-beds, namely, that +containing the Microlestes, which has just been described, which +constitutes, as we have seen, the uppermost member of the Trias, +and another of still greater extent, and still more rich in the +remains of fish and reptiles, which is of older date, intervening +between the Keuper and Muschelkalk.</p> + +<p>The genera <i>Saurichthys, Hybodus,</i> and <i>Gyrolepis</i> are +found in both these breccias, and one of the species, <i> +Saurichthys Mongeoti,</i> is common to both bone-beds, as is also a +remarkable reptile called <i>Nothosaurus mirabilis.</i> The saurian +called <i>Belodon</i> by H. von Meyer, of the Thecodont family, is +another Triassic form, associated at Diegerloch with +Microlestes.</p> + +<p> </p> + +<hr> +<p class="page"><a name="page 369">[ 369 ]</a></p> + +<center><small>TRIAS OF ENGLAND.</small></center> + +<p>Between the Lias and the Coal (or Carboniferous group) there is +interposed, in the midland and western counties of England, a great +series of red loams, shales, and sandstones, to which the name of +the “New Red Sandstone formation” was first given, to +distinguish it from other shales and sandstones called the +“Old Red,” often identical in mineral character, which +lie immediately beneath the coal. The name of “Red +Marl” has been incorrectly applied to the red clays of this +formation, as before explained (<a href="ch2.html#page 38">p. +38</a>), for they are remarkably free from calcareous matter. The +absence, indeed, of carbonate of lime, as well as the scarcity of +organic remains, together with the bright red colour of most of the +rocks of this group, causes a strong contrast between it and the +Jurassic formations before described.</p> + +<p>The group in question is more fully developed in Germany than in +England or France. It has been called the Trias by German writers, +or the Triple Group, because it is separable into three distinct +formations, called the “Keuper,” the +“Muschelkalk,” and the “Bunter-sandstein.” +Of these the middle division, or the Muschelkalk, is wholly wanting +in England, and the uppermost (Keuper) and lowest (Bunter) members +of the series are not rich in fossils.</p> + +<p><b>Upper Trias or Keuper.</b>—In certain grey indurated +marls below the bone-bed Mr. Boyd Dawkins has found at Watchet, on +the coast of Somersetshire, a molar tooth of Microlestes, enabling +him to refer to the Trias strata formerly supposed to be Liassic. +Mr. Charles Moore had previously discovered many teeth of mammalia +of the same family near Frome, in Somersetshire, in the contents of +a vertical fissure traversing a mass of carboniferous limestone. +The top of this fissure must have communicated with the bed of the +Triassic sea, and probably at a point not far from the ancient +shore on which the small marsupials of that era abounded.</p> + +<p>This upper division of the Trias called the Keuper is of great +thickness in the central counties of England, attaining, according +to Mr. Hull’s estimate, no less than 3450 feet in Cheshire, +and it covers a large extent of country between Lancashire and +Devonshire.</p> + +<p>In Worcestershire and Warwickshire in sandstone belonging to the +uppermost part of the Keuper the bivalve crustacean <i>Estheria +minuta</i> occurs. The member of the English “New Red” +containing this shell, in those parts of England, is, according to +Sir Roderick Murchison and Mr. Strickland, 600 feet thick, and +consists chiefly of red marl or slate, with</p> + +<p> </p> + +<hr> +<p class="page"><a name="page 370">[ 370 ]</a></p> + +<img src="../images3/fig390.jpg" width="95" height="105" alt= +"Fig. 390: Estheria minuta." align="right"> + +<p>a band of sandstone. Ichthyodorulites, or spines of <i> +Hybodus,</i> teeth of fishes, and footprints of reptiles were +observed by the same geologists in these strata.</p> + +<img src="../images3/fig391.jpg" width="276" height="260" alt= +"Fig. 391: Hyperodapedon Gordoni. Left Plate, Maxillary." align= +"left"> + +<p>In the Upper Trias or Keuper the remains of two saurians of the +order Lacertilia have been found. The one called <i> +Rhynchosaurus</i> occurred at Grinsell near Shrewsbury, and is +characterised by having a small bird-like skull and jaws without +teeth. The other <i>Hyperodapedon</i> (Fig. 391) was first noticed +in 1858, near Elgin, in strata now recognised as Upper Triassic, +and afterwards in beds of about the same age in the neighbourhood +of Warwick. Remains of the same genus have been found both in +Central India and Southern Africa in rocks believed to be of +Triassic age. The Hyperodapedon has been shown by Professor Huxley +to be a terrestrial reptile having numerous palatal teeth, and +closely allied to the living Sphenodon of New Zealand.</p> + +<p>The recent discoveries of a living saurian in New Zealand so +closely allied to this supposed extinct division of the Lacertilia +seems to afford an illustration of a principle pointed out by Mr. +Darwin of the survival in insulated tracts, after many changes in +physical geography, of orders of which the congeners have become +extinct on continents where they have been exposed to the severer +competition of a larger progressive fauna.</p> + +<img src="../images3/fig392.jpg" width="85" height="138" alt= +"Fig. 392: Tooth of Labyrinthodon." align="right"> + +<p>Teeth of Labyrinthodon (Fig. 392) found in the Keuper in +Warwickshire were examined microscopically by Professor Owen, and +compared with other teeth from the German Keuper. He found after +careful investigation that neither of them could be referred to +true saurians, although they had been named <i>Mastodonsaurus</i> +and <i>Phytosaurus</i> by Jäger. It appeared that they were of +the <i>Batrachian</i> order, and of gigantic</p> + +<p> </p> + +<hr> +<p class="page"><a name="page 371">[ 371 ]</a></p> + +<p>dimensions in comparison with any representatives of that order +now living. Both the Continental and English fossil teeth exhibited +a most complicated texture, differing from that previously observed +in any reptile, whether recent or extinct, but most nearly +analogous to the <i>Ichthyosaurus.</i> A section of one of these +teeth exhibits a series of irregular folds, resembling the +labyrinthic windings of the surface of the brain; and from this +character Professor Owen has proposed the name Labyrinthodon for +the new genus. Fig. 393 of part of one is given from his +“Odontography,” plate 64, A. The entire length of this +tooth is supposed to have been about three inches and a half, and +the breadth at the base one inch and a half.</p> + +<center><img src="../images3/fig393.jpg" width="354" height="336" alt= +"Fig. 393: Transverse section of upper part of tooth of Labyrinthodon Jaegeri."> +</center> + +<p><i>Rock-salt.</i>—In Cheshire and Lancashire there are red +clays containing gypsum and salt of the age of the Trias which are +between 1000 and 1500 feet thick. In some places lenticular masses +of pure rock-salt nearly 100 feet thick are interpolated between +the argillaceous beds. At the base of the formation beneath the +rock-salt occur the Lower Sandstones and Marl, called provincially +in Cheshire “water-stones,” which are largely quarried +for building. They are often ripple-marked, and are impressed with +numerous footprints of reptiles.</p> + +<p>The basement beds of the Keuper rest with a slight</p> + +<p> </p> + +<hr> +<p class="page"><a name="page 372">[ 372 ]</a></p> + +<p>unconformability upon an eroded surface of the +“Bunter” next to be described.</p> + +<img src="../images3/fig394.jpg" width="170" height="192" alt= +"Fig. 394: Single footstep of Cheirotherium." align="left"> + +<p><b>Lower Trias or Bunter.</b>—The lower division or +English representative of the “Bunter” attains a +thickness of 1500 feet in the counties last mentioned, according to +Professor Ramsay. Besides red and green shales and red sandstones, +it comprises much soft white quartzose sandstone, in which the +trunks of silicified trees have been met with at Allesley Hill, +near Coventry. Several of them were a foot and a half in diameter, +and some yards in length, decidedly of coniferous wood, and showing +rings of annual growth.* Impressions, also, of the footsteps of +animals have been detected in Lancashire and Cheshire in this +formation. Some of the most remarkable occur a few miles from +Liverpool, in the whitish quartzose sandstone of Storton Hill, on +the west side of the Mersey. They bear a close resemblance to +tracks first observed in this member of the Upper New Red +Sandstone, at the village of Hesseberg, near Hildburghausen, in +Saxony. For many years these footprints have been referred to a +large unknown quadruped, provisionally named <i>Cheirotherium</i> +by Professor Kaup, because the marks both of the fore and hind feet +resembled impressions made by a human hand. (See Fig. 394.) The +foot-marks at Hesseberg are partly concave, and partly in relief, +the former, or the depressions, are seen upon the upper surface of +the sandstone slabs, but those in relief are only upon the lower +surfaces, being, in fact, natural casts, formed in the subjacent +footprints as in moulds. The larger impressions, which seem to be +those of the hind foot, are generally eight inches in length, and +five in width, and one was twelve inches long. Near each large +footstep, and at a regular distance (about an inch and a half) +before it, a smaller print of a fore foot, four inches long and +three inches wide, occurs. The footsteps follow each other</p> + +<center><img src="../images3/fig395.jpg" width="367" height="82" alt= +"Fig. 395: Line of footsteps on slab of sandstone."></center> + +<p class="fnote">* Buckland, Proc. Geol. Soc., vol. ii, p. 439; and +Murchison and Strickland, Geol. Trans., Second Series., vol. v, p. +347.</p> + +<p> </p> + +<hr> +<p class="page"><a name="page 373">[ 373 ]</a></p> + +<p>in pairs, each pair in the same line, at intervals of fourteen +inches from pair to pair. The large as well as the small steps show +the great toes alternately on the right and left side; each step +makes the print of five toes, the first, or great toe, being bent +inward like a thumb. Though the fore and hind foot differ so much +in size, they are nearly similar in form.</p> + +<p>As neither in Germany nor in England had any bones or teeth been +met with in the same identical strata as the footsteps, anatomists +indulged, for several years, in various conjectures respecting the +mysterious animals from which they might have been derived. +Professor Kaup suggested that the unknown quadruped might have been +allied to the <i>Marsupialia</i>; for in the kangaroo the first toe +of the fore foot is in a similar manner set obliquely to the +others, like a thumb, and the disproportion between the fore and +hind feet is also very great. But M. Link conceived that some of +the four species of animals of which the tracks had been found in +Saxony might have been gigantic <i>Batrachians,</i> and when it was +afterwards inferred that the Labyrinthodon was an air-breathing +reptile, it was conjectured by Professor Owen that it might be one +and the same as the Cheirotherium.</p> + +<p><b>Dolomitic Conglomerate of Bristol.</b>—Near Bristol, in +Somersetshire, and in other counties bordering the Severn, the +lowest strata belonging to the Triassic series consist of a +conglomerate or breccia resting unconformably upon the Old Red +Sandstone, and on different members of the Carboniferous rocks, +such as the Coal Measures, Millstone Grit, and Mountain Limestone. +This mode of superposition will be understood by reference to the +section below Dundry Hill (<a href="../images/fig85.jpg">Fig. 85</a>), +where No. 4 is the dolomitic conglomerate. Such breccias may have +been partly the result of the subÆrial waste of an old +land-surface which gradually sank down and suffered littoral +denudation in proportion as it became submerged. The pebbles and +fragments of older rocks which constitute the conglomerate are +cemented together by a red or yellow base of dolomite, and in some +places the encrinites and other fossils derived from the Mountain +Limestone are so detached from the parent rocks that they have the +deceptive appearance of belonging to a fauna contemporaneous with +the dolomitic beds in which they occur. The imbedded fragments are +both rounded and angular, some consisting of sandstone from the +coal-measures, being of vast size, and weighing nearly a ton. +Fractured bones and teeth of saurians which are truly of +contemporaneous origin are dispersed through some parts of the +breccia, and two of these reptiles called Thecodont saurians, named +from the</p> + +<p> </p> + +<hr> +<p class="page"><a name="page 374">[ 374 ]</a></p> + +<p>manner in which the teeth were implanted in the jawbone, +obtained great celebrity because the patches of red conglomerate in +which they were found, near Bristol, were originally supposed to be +of Permian or Palæozoic age, and therefore the only +representatives in England of vertebrate animals of so high a grade +in rocks of such antiquity. The teeth of these saurians are +conical, compressed, and with finely serrated edges (see Fig. 396); +they are referred by Professor Huxley to the Dinosaurian order.</p> + +<img src="../images3/fig396.jpg" width="133" height="204" alt= +"Fig. 396: Tooth of Thecodontosaurus." align="left"> + +<p><b>Origin of Red Sandstone and Rock-salt.</b>—In various +parts of the world, red and mottled clays and sandstones, of +several distinct geological epochs, are found associated with salt, +gypsum, and magnesian limestone, or with one or all of these +substances. There is, therefore, in all likelihood, a general cause +for such a coincidence. Nevertheless, we must not forget that there +are dense masses of red and variegated sandstones and clays, +thousands of feet in thickness, and of vast horizontal extent, +wholly devoid of saliferous or gypseous matter. There are also +deposits of gypsum and of common salt, as in the blue-clay +formation of Sicily, without any accompanying red sandstone or red +clay.</p> + +<p>These red deposits may be accounted for by the decomposition of +gneiss and mica schist, which in the eastern Grampians of Scotland +has produced a mass of detritus of precisely the same colour as the +Old Red Sandstone.</p> + +<p>It is a general fact, and one not yet accounted for, that +scarcely any fossil remains are ever preserved in stratified rocks +in which this oxide of iron abounds; and when we find fossils in +the New or Old Red Sandstone in England, it is in the grey, and +usually calcareous beds, that they occur. The saline or gypseous +interstratified beds may have been produced by submarine gaseous +emanations, or hot mineral springs, which often continue to flow in +the same spots for ages. Beds of rock-salt are, however, more +generally attributed to the evaporation of lakes or lagoons +communicating at intervals with the ocean. In Cheshire two beds of +salt occur of the extraordinary thickness of 90 or even 100 feet, +and extending over an area supposed to be 150 miles in diameter. +The adjacent beds present ripple-marked sandstones and footprints +of animals at so many levels as to imply that the whole area +underwent a slow and gradual depression during the formation of the +red sandstone.</p> + +<p>Major Harris, in his “Highlands of Ethiopia,” +describes a</p> + +<p> </p> + +<hr> +<p class="page"><a name="page 375">[ 375 ]</a></p> + +<p>salt lake, called the Bahr Assal, near the Abyssinian frontier, +which once formed the prolongation of the Gulf of Tadjara, but was +afterwards cut off from the gulf by a broad bar of lava or of land +upraised by an earthquake. “Fed by no rivers, and exposed in +a burning climate to the unmitigated rays of the sun, it has shrunk +into an elliptical basin, seven miles in its transverse axis, half +filled with smooth water of the deepest cærulean hue, and +half with a solid sheet of glittering snow-white salt, the +offspring of evaporation.” “If,” says Mr. Hugh +Miller, “we suppose, instead of a barrier of lava, that +sand-bars were raised by the surf on a flat arenaceous coast during +a slow and equable sinking of the surface, the waters of the outer +gulf might occasionally topple over the bar, and supply fresh brine +when the first stock had been exhausted by evaporation.”</p> + +<p>The Runn of Cutch, as I have shown elsewhere,* is a low region +near the delta of the Indus, equal in extent to about a quarter of +Ireland, which is neither land nor sea, being dry during part of +every year, and covered by salt water during the monsoons. Here and +there its surface is incrusted over with a layer of salt caused by +the evaporation of sea-water. A subsiding movement has been +witnessed in this country during earthquakes, so that a great +thickness of pure salt might result from a continuation of such +sinking.</p> + +<br> + + +<center><small>TRIAS OF GERMANY.</small></center> + +<p>In Germany, as before hinted, chapter 21, the Trias first +received its name as a Triple Group, consisting of two sandstones +with an intermediate marine calcareous formation, which last is +wanting in England.</p> + +<center><small>NOMENCLATURE OF TRIAS.</small></center> + +<center> +<table border="1" cellspacing="0" cellpadding="4" width="80%" +summary="German, French and English nomenclature."> +<tr> +<td align="center">German</td> +<td align="center">French</td> +<td align="center">English</td> +</tr> + +<tr> +<td align="left" valign="top">Keuper</td> +<td align="left" valign="top">Marnes irisées</td> +<td align="left">Saliferous and gypseous<br> +shales and sandstone.</td> +</tr> + +<tr> +<td align="left" valign="top">Muschelkalk</td> +<td align="left">Muschelkalk, on calcaire coquillier</td> +<td align="left" valign="top">Wanting in England.</td> +</tr> + +<tr> +<td align="left" valign="top">Bunter-sandstein</td> +<td align="left" valign="top">Grès bigarré</td> +<td align="left">Sandtone and quartzose conglomerate.</td> +</tr> +</table> +</center> + +<p><b>Keuper.</b>—The first of these, or the Keuper, +underlying the beds before described as Rhætic, attains in +Würtemberg a thickness of about 1000 feet. It is divided by +Alberti into sandstone, gypsum, and carbonaceous +clay-slate.† Remains of reptiles called <i>Nothosaurus</i> +and <i>Phytosaurus,</i> have been found in it with Labyrinthodon; +the detached teeth, also, of</p> + +<p class="fnote">* Principles of Geology, chap. xxvii.<br> +† Monog. des Bunter-Sandsteins.</p> + +<p> </p> + +<hr> +<p class="page"><a name="page 376">[ 376 ]</a></p> + +<img src="../images3/fig397.jpg" width="179" height="207" alt= +"Fig. 397: Equisetites columnaris." align="left"> + +<p>placoid fish and of Rays, and of the genera <i>Saurichthys</i> +and <i>Gyrolepis</i> (<a href="../images3/fig383.jpg">Figs. 387, +388</a>). The plants of the Keuper are generically very analogous +to those of the oolite and lias, consisting of ferns, equisetaceous +plants, cycads, and conifers, with a few doubtful monocotyledons. A +few species such as <i>Equisetites columnaris,</i> are common to +this group and the oolite.</p> + +<p><i>St. Cassian and Hallstadt Beds</i> (see Map, Fig. +398).— The sandstones and clay of the Keuper resemble the +deposits of estuaries and a shallow sea near the land, and afford, +in the N.W. of Germany, as in France and England, but a scanty +representation of the marine life of that period. We might, +however, have anticipated, from its rich reptilian fauna, that the +contemporaneous inhabitants of the sea of the Keuper period would +be very numerous, should we ever have an opportunity of bringing +their remains to light. This, it is believed, has at length been +accomplished, by the position now assigned to certain Alpine rocks +called the “St. Cassian beds,” the true place of which +in the series was until lately a subject of much doubt and +discussion. It has been proved that the Hallstadt beds on the +northern flanks of the Austrian Alps correspond in age with the St. +Cassian beds on their southern declivity, and the Austrian +geologists, M. Suess of Vienna and others, have satisfied +themselves that the Hallstadt formation is referable to the period +of the Upper Trias.</p> + +<center><img src="../images3/fig398.jpg" width="389" height="237" alt= +"Fig. 398: Map of Tyrol and Styria showing St. Cassian and Hallstadt Beds."> +</center> + +<p> </p> + +<hr> +<p class="page"><a name="page 377">[ 377 ]</a></p> + +<img src="../images3/fig399.jpg" width="137" height="274" alt= +"Fig. 399: Scoliotoma. Fig. 400: Koninckia Leonhardi." align= +"left"> + +<p>Assuming this conclusion to be correct, we become acquainted +suddenly and unexpectedly with a rich marine fauna belonging to a +period previously believed to be very barren of organic remains, +because in England, France, and Northern Germany the upper Trias is +chiefly represented by beds of fresh or brackish water origin.</p> + +<p>About 600 species of invertebrate fossils occur in the Hallstadt +and St. Cassian beds, many of which are still undescribed; some of +the Mollusca are of new and peculiar genera, as <i>Scoliostoma,</i> +Fig. 399, and <i>Platystoma,</i> Fig. 400, among the Gasteropoda; +and <i>Koninckia,</i> Fig. 401, among the Brachiopoda.</p> + +<img src="../images3/fig401.jpg" width="246" height="238" alt= +"Fig. 401: Koninckia Leonhardi." align="right"> + +<p>The following table of genera of marine shells from the +Hallstadt and St. Cassian beds, drawn up first on the joint +authority of M. Suess and the late Dr. Woodward, and since +corrected by Messrs. Etheridge and Tate, shows how many connecting +links between the fauna of primary and secondary Palæozoic +and Mesozoic rocks are supplied by the St. Cassian and Hallstadt +beds.</p> + +<br> + + +<center><small>GENERA OF FOSSIL MOLLUSCA IN THE ST. CASSIAN AND +HALLSTADT BEDS.</small></center> + +<center> +<table border="0" cellpadding="4" cellspacing="0" width="100%" +summary= +"Column 1: Common to Older Rocks. Column 2: Characteristic Triassic Genera. Column 3: Common to Newer Rocks."> +<tr> +<td colspan="2" align="center"><small>Common to Older +Rocks</small></td> +<td colspan="2" align="center"><small>Characteristic Triassic +Genera</small></td> +<td colspan="2" align="center"><small>Common to Newer +Rocks</small></td> +</tr> + +<tr> +<td width="20"></td> +<td align="left" valign="top">Orthoceras<br> +Bactrites<br> +Macrocheilus<br> +Loxonema<br> +Holopella<br> +Murchisonia<br> +Porcellia<br> +Athyris<br> +Retzia<br> +Cyrtina<br> +Euomphalus</td> +<td width="24"></td> +<td align="left" valign="top">Ceratites<br> +Cochloceras<br> +Choristoceras<br> +Rhabdoceras<br> +Aulacoceras<br> +Scoliostoma *<br> +Naticella<br> +Platystoma<br> +Ptychostoma<br> +Euchrysalis<br> +Halobia<br> +Hornesia<br> +Amphiclina<br> +Koninckia<br> +Cassianella †<br> +Myophoria †</td> +<td width="20"></td> +<td align="left" valign="top">Ammonites<br> +Chemnitzia<br> +Cerithium<br> +Monodonta<br> +Opis<br> +Sphoera<br> +Cardita<br> +Myoconcha<br> +Hinnites<br> +Monotis<br> +Plicatula<br> +Pachyrisma<br> +Thecidium</td> +</tr> +</table> +</center> + +<p class="fnote">* Reaches its maximum in the Trias, but passes +down to older rocks.<br> +† Reach their maximum in the Trias, but pass up to newer +rocks.</p> + +<p> </p> + +<hr> +<p class="page"><a name="page 378">[ 378 ]</a></p> + +<p>The first column marks the last appearance of several genera +which are characteristic of Palæozoic strata. The second +shows those genera which are characteristic of the Upper Trias, +either as peculiar to it, or, as in the three cases marked by +asterisks, reaching their maximum of development at this era. The +third column marks the first appearance in Triassic rocks of genera +destined to become more abundant in later ages.</p> + +<p>It is only, however, when we contemplate the number of species +by which each of the above-mentioned genera are represented that we +comprehend the peculiarities of what is commonly called the St. +Cassian fauna. Thus, for example, the Ammonite, which is not common +to older rocks, is represented by no less than seventy-three +species; whereas Loxonema, which is only known as common to older +rocks, furnishes fifteen Triassic species. Cerithium, so abundant +in tertiary strata, and which still lives, is represented by no +less than fourteen species. As the Orthoceras had never been met +with in the marine Muschelkalk, much surprise was naturally felt +that seven or eight species of the genus should appear in the +Hallstadt beds, assuming these last to belong to the Upper Trias. +Among these species are some of large dimensions, associated with +large Ammonites with foliated lobes, a form never seen before so +low in the series, while the Orthoceras had never been seen so +high.</p> + +<p>On the whole, the rich marine fauna of Hallstadt and St. +Cassian, now generally assigned to the lowest members of the Upper +Trias or Keuper, leads us to suspect that when the strata of the +Triassic age are better known, especially those belonging to the +period of the Bunter sandstone, the break between the +Palæozoic and Mesozoic Periods may be almost effaced. Indeed +some geologists are not yet satisfied that the true position of the +St. Cassian beds (containing so great an admixture of types, having +at once both Mesozoic and Palæozoic affinities) is made out, +and doubt whether they have yet been clearly proved to be newer +than the Muschelkalk.</p> + +<p><b>Muschelkalk.</b>—The next member of the Trias in +Germany, the <i>Muschelkalk,</i> which underlies the <i>Keuper</i> +before described, consists chiefly of a compact greyish limestone, +but includes beds of dolomite in many places, together with gypsum +and rock-salt. This limestone, a formation wholly unrepresented in +England, abounds in fossil shells, as the name implies. Among the +Cephalopoda there are no belemnites, and no ammonites with foliated +sutures, as in the Lias, and Oolite, and the Hallstadt beds; but we +find instead a genus allied to</p> + +<p> </p> + +<hr> +<p class="page"><a name="page 379">[ 379 ]</a></p> + +<center><img src="../images3/fig402.jpg" width="399" height="562" alt= +"Fig. 402: Ceratites nodosus. Fig. 403: Gervillia (Avicula) socialis. Fig. 404: Enerinus liliiformis. Fig. 405: Aspidura loricata."> +</center> + +<p>the Ammonite, called <i>Ceratites</i> by de Haan, in which the +descending lobes (Fig. 402) terminate in a few small denticulations +pointing inward. Among the bivalve crustacea, the <i>Estheria +minuta,</i> Bronn (see <a href="../images3/fig390.jpg">Fig. 390</a>), +is abundant, ranging through the Keuper, Muschelkalk, and +Bunter-sandstein; and <i>Gervillia socialis</i> (Fig. 403), having +a similar range, is found in great numbers in the Muschelkalk of +Germany, France, and Poland.</p> + +<p> </p> + +<hr> +<p class="page"><a name="page 380">[ 380 ]</a></p> + +<img src="../images3/fig406.jpg" width="161" height="226" alt= +"Fig. 406: Palatal teeth of Placodus gigas." align="left"> + +<p>The abundance of the heads and stems of lily encrinites, <i> +Encrinus liliiformis</i> (Fig. 404), (or <i>Encrinites +moniliformis</i>), shows the slow manner in which some beds of this +limestone have been formed in clear sea-water. The star-fish called +<i>Aspidura loricata</i> (Fig. 405) is as yet peculiar to the +Muschelkalk. In the same formation are found the skull and teeth of +a reptile of the genus <i>Placodus</i> (see Fig. 406), which was +referred originally by Munster, and afterwards by Agassiz, to the +class of fishes. But more perfect specimens enabled Professor Owen, +in 1858, to show that this fossil animal was a Saurian reptile, +which probably fed on shell-bearing mollusks, and used its short +and flat teeth, so thickly coated with enamel, for pounding and +crushing the shells.</p> + +<img src="../images3/fig407.jpg" width="180" height="211" alt= +"Fig. 407: Voltzia heterophylla." align="right"> + +<p><b>Bunter-sandstein.</b>—The <i>Bunter-sandstein</i> +consists of various-coloured sandstones, dolomites, and red clays, +with some beds, especially in the Hartz, of calcareous pisolite or +roe-stone, the whole sometimes attaining a thickness of more than +1000 feet. The sandstone of the Vosges is proved, by its fossils, +to belong to this lowest member of the Triassic group. At Sulzbad +(or Soultz-les-bains), near Strasburg, on the flanks of the Vosges, +many plants have been obtained from the “bunter,” +especially conifers of the extinct genus <i>Voltzia,</i> of which +the fructification has been preserved. (See Fig. 407.) Out of +thirty species of ferns, cycads, conifers, and other plants, +enumerated by M. Ad. Brongniart, in 1849, as coming from the +“Grès bigarré,” or Bunter, not one is +common to the Keuper.</p> + +<p>The footprints of Labyrinthodon observed in the clays of this +formation at Hildburghausen, in Saxony, have already been +mentioned. Some idea of the variety and importance of the +terrestrial vertebrate fauna of the three members of the Trias in +Northern Germany may be derived from the fact that in the great +monograph by the late Hermann von Meyer on the reptiles</p> + +<p> </p> + +<hr> +<p class="page"><a name="page 381">[ 381 ]</a></p> + +<p>of the Trias, the remains of no less than eighty distinct +species are described and figured.</p> + +<center><small>TRIAS OF THE UNITED STATES.</small></center> + +<p><b>New Red Sandstone of the Valley of the Connecticut +River.</b>—In a depression of the granitic or hypogene rocks +in the States of Massachusetts and Connecticut strata of red +sandstone, shale, and conglomerate are found, occupying an area +more than 150 miles in length from north to south, and about five +to ten miles in breadth, the beds dipping to the eastward at angles +varying from 5 to 50 degrees. The extreme inclination of 50 degrees +is rare, and only observed in the neighbourhood of masses of trap +which have been intruded into the red sandstone while it was +forming, or before the newer parts of the deposit had been +completed. Having examined this series of rocks in many places, I +feel satisfied that they were formed in shallow water, and for the +most part near the shore, and that some of the beds were from time +to time raised above the level of the water, and laid dry, while a +newer series, composed of similar sediment, was forming.</p> + +<img src="../images3/fig408.jpg" width="108" height="437" alt= +"Fig. 408: Foot-prints of a bird, Turner's Falls, Valley of the Connecticut." + align="right"> + +<p>According to Professor Hitchcock, the footprints of no less than +thirty-two species of bipeds, and twelve of quadrupeds, have been +already detected in these rocks. Thirty of these are believed to be +those of birds, four of lizards, two of chelonians, and six of +batrachians. The tracks have been found in more than twenty places, +scattered through an extent of nearly 80 miles from north to south, +and they are repeated through a succession of beds attaining at +some points a thickness of more than 1000 feet.*</p> + +<p>The bipedal impressions are, for the most part, trifid, and show +the same number of joints as exist in the feet of living +tridactylous birds. Now, such birds have three phalangeal bones for +the inner toe, four for the middle, and five for the outer one (see +Fig. 408); but the impression of the terminal joint is that of the +nail only. The fossil footprints exhibit regularly, where the +joints are seen, the same number; and we see in each continuous +line of tracks</p> + +<p class="fnote">* Hitchcock, Mem. of Amer. Acad., New Series, vol. +iii, p. 129, 1848.</p> + +<p> </p> + +<hr> +<p class="page"><a name="page 382">[ 382 ]</a></p> + +<p>the three-jointed and five-jointed toes placed alternately +outward, first on the one side, and then on the other. In some +specimens, besides impressions of the three toes in front, the +rudiment is seen of the fourth toe behind. It is not often that the +matrix has been fine enough to retain impressions of the integument +or skin of the foot; but in one fine specimen found at +Turner’s Falls, on the Connecticut, by Dr. Deane, these +markings are well preserved, and have been recognised by Professor +Owen as resembling the skin of the ostrich, and not that of +reptiles.</p> + +<p>The casts of the footprints show that some of the fossil bipeds +of the red sandstone of Connecticut had feet four times as large as +the living ostrich, but scarcely, perhaps, larger than the Dinornis +of New Zealand, a lost genus of feathered giants related to the +Apteryx, of which there were many species which have left their +bones and almost entire skeletons in the superficial alluvium of +that island. By referring to what was said of the Iguanodon of the +Wealden, the reader will perceive that the Dinosaur was somewhat +intermediate between reptiles and birds, and left a series of +tridactylous impressions on the sand.</p> + +<p>To determine the exact age of the red sandstone and shale +containing these ancient footprints, in the United States, is not +possible at present. No fossil shells have yet been found in the +deposit, nor plants in a determinable state. The fossil fish are +numerous and very perfect; but they are of a peculiar type, called +<i>Ischypterus,</i> by Sir Philip Egerton, from the great size and +strength of the fulcral rays of the dorsal fin, from ischus, +strength, and pteron, a fin.</p> + +<p>The age of the Connecticut beds can not be proved by direct +superposition, but may be presumed from the general structure of +the country. That structure proves them to be newer than the +movements to which the Appalachian or Allegheny chain owes its +flexures, and this chain includes the ancient or palæozoic +coal-formation among its contorted rocks.</p> + +<p><b>Coal-field of Richmond, Virginia.</b>—In the State of +Virginia, at the distance of about 13 miles eastward of Richmond, +the capital of that State, there is a coal-field occurring in a +depression of the granite rocks, and occupying a geological +position analogous to that of the New Red Sandstone, +above-mentioned, of the Connecticut valley. It extends 26 miles +from north to south, and from four to twelve from east to west.</p> + +<p>The plants consist chiefly of zamites, calamites, equiseta, and +ferns, and, upon the whole, are considered by Professor</p> + +<p> </p> + +<hr> +<p class="page"><a name="page 383">[ 383 ]</a></p> + +<p>Heer to have the nearest affinity to those of the European +Keuper.</p> + +<p>The equiseta are very commonly met with in a vertical position +more or less compressed perpendicularly. It is clear that they grew +in the places where they are now buried in strata of hardened sand +and mud. I found them maintaining their erect attitude, at points +many miles apart, in beds both above and between the seams of coal. +In order to explain this fact, we must suppose such shales and +sandstones to have been gradually accumulated during the slow and +repeated subsidence of the whole region.</p> + +<img src="../images3/fig409.jpg" width="230" height="164" alt= +"Fig. 409: Triassic coal-shale, Richmond, Virginia." align="right"> + + +<p>The fossil fish are Ganoids, some of them of the genus <i> +Catopterus,</i> others belonging to the liassic genus <i> +Tetragonolepis (Æchmodus),</i> see <a href= +"../images3/fig375.jpg">Fig. 376.</a> Two species of <i> +Entomostraca</i> called <i>Estheria</i> are in such profusion in +some shaly beds as to divide them like the plates of mica in +micaceous shales (see Fig. 409).</p> + +<p>These Virginian coal-measures are composed of grits, sandstones, +and shales, exactly resembling those of older or primary date in +America and Europe, and they rival, or even surpass, the latter in +the richness and thickness of the coal-seams. One of these, the +main seam, is in some places from 30 to 40 feet thick, composed of +pure bituminous coal. The coal is like the finest kinds shipped at +Newcastle, and when analysed yields the same proportions of carbon +and hydrogen—a fact worthy of notice, when we consider that +this fuel has been derived from an assemblage of plants very +distinct specifically, and in part generically, from those which +have contributed to the formation of the ancient or palæozoic +coal.</p> + +<p><b>Triassic Mammifer.</b>—In North Carolina, the late +Professor Emmons has described the strata of the Chatham +coal-field, which correspond in age to those near Richmond, in +Virginia. In beds underlying them he has met with three jaws of a +small insectivorous mammal which he has called <i>Dromatherium +sylvestre,</i> closely allied to <i>Spalacotherium.</i> Its nearest +living analogue, says Professor Owen, “is found in +Myrmecobius; for each ramus of the lower jaw contained ten small +molars in a continuous series, one canine, and three</p> + +<p> </p> + +<hr> +<p class="page"><a name="page 384">[ 384 ]</a></p> + +<p>conical incisors—the latter being divided by short +intervals.”</p> + +<p><b>Low Grade of Early Mammals favourable to the Theory of +Progressive Development.</b>—There is every reason to believe +that this fossil quadruped is at least as ancient as the +Microlestes of the European Trias described in <a href= +"ch21.html#page 368">p. 368</a>; and the fact is highly important, +as proving that a certain low grade of marsupials had not only a +wide range in time, from the Trias to the Purbeck, or uppermost +oolitic strata of Europe, but had also a wide range in space, +namely, from Europe to North America, in an east and west +direction, and, in regard to latitude, from Stonesfield, in 52° +N., to that of North Carolina, 35° N.</p> + +<p>If the three localities in Europe where the most ancient +mammalia have been found—Purbeck, Stonesfield, and +Stuttgart—had belonged all of them to formations of the same +age, we might well have imagined so limited an area to have been +peopled exclusively with pouched quadrupeds, just as Australia now +is, while other parts of the globe were inhabited by placentals; +for Australia now supports one hundred and sixty species of +marsupials, while the rest of the continents and islands are +tenanted by about seventeen hundred species of mammalia, of which +only forty-six are marsupial, namely, the opossums of North and +South America. But the great difference of age of the strata in +each of these three localities seems to indicate the predominance +throughout a vast lapse of time (from the era of the Upper Trias to +that of the Purbeck beds) of a low grade of quadrupeds; and this +persistency of similar generic and ordinal types in Europe while +the species were changing, and while the fish, reptiles, and +mollusca were undergoing great modifications, would naturally lead +us to suspect that there must also have been a vast extension in +space of the same marsupial forms during that portion of the +Secondary or Mesozoic epoch which has been termed “the age of +reptiles.” Such an inference as to the wide geographical +range of the ancient marsupials has been confirmed by the discovery +in the Trias of North America of the above-mentioned Dromatherium. +The predominance in earlier ages of these mammalia of a low grade, +and the absence, so far as our investigations have yet gone, of +species of higher organisation, whether aquatic or terrestrial, is +certainly in favour of the theory of progressive development.</p> + +<br> +<hr> +<small><a href="contents.html">Contents</a> / <a href="ch20.html"> +Chapter XX</a> / <a href="ch22.html">Chapter XXII</a></small> +</body> +</html> + |