Fig. 76Fig. 76.—Trigonocarpum Nöggerathii.
Fig. 76.—Trigonocarpum Nöggerathii.
Among the genera enumerated by Colonel Von Gutbier are some fruits calledCardiocarpon, andAsterophyllitesandAnnularia, so characteristic of the Carboniferous age. The Lepidodendron is also common to the Permian rocks of Saxony, Russia, and Thuringia; also theNöggerathia, a family of large trees, intermediate between Cycads (Fig. 72) and the Conifers. The fruit of one of these is represented inFig 76.
Permian Rocks.—We now give a sketch of the physiognomy of the earth in Permian times. Of what do the beds consist? What is the extent, and what is the mineralogical constitution of the rocks deposited in the seas of the period? The Permian formation consists of three members, which are in descending order—
1. Upper Permian sandstone, or Grès des Vosges; 2. Magnesian Limestone, or Zechstein; 3. Lower Red Sandstone, Marl-slate or Kupferschiefer, and Rothliegende.
Thegrès des Vosges, usually of a red colour, and from 300 to 450 feet thick, composes all the southern part of the Vosges Mountains, where it forms frequent level summits, which are evidences of an ancient plain that has been acted on by running water. It only contains a few vegetable remains.
TheMagnesian Limestone, Pierre de mine, or Zechstein, so called in consequence of the numerous metalliferous deposits met with in its diverse beds, presents in France only a few insignificant fragments; but in Germany and England it attains the thickness of 450 feet.It is composed of a diversified mass of Magnesian Limestone, generally of a yellow colour, but sometimes red and brown, and bituminous clay, the last black and fetid. The subordinate rocks consist of marl, gypsum, and inflammable bituminous schists. The beds of marl slate are remarkable for the numbers of peculiar fossil fishes which they contain; and from the occurrence of small proportions of argentiferous grey copper-ore, met with in the bituminous shales which are worked in the district of Mansfeld, in Thuringia—the latter are calledKupferschieferin Germany.
TheLower Red Sandstone, which attains a thickness of from 300 to 600 feet, is found over great part of Germany, in the Vosges, and in England. Its fossil remains are few and rare; they include silicified trunks of Conifers, some impressions of Ferns, and Calamites.
In England the Permian strata, to a great extent, consist of red sandstones and marls; and the Magnesian Limestone of the northern counties is also, though to a less degree, associated with red marls.
In Lancashire thin beds of Magnesian Limestone are interstratified with red marls in the upper Permian strata, beneath which there are soft Red Sandstones, estimated by Mr. Hull to be about 1,500 feet thick. These are supposed to represent the Rothliegende, and no shells of any kind have been found in them. The upper Permian beds, however, contain a few Magnesian Limestone species, such asGervillia antiqua,Pleurophorus costatus,Schizodus obscurus, and some others, but all small and dwarfed.
The coal-fields of North and South Staffordshire, Tamworth, Coalbrook Dale, and of the Forest of Wyre, are partly bordered by Permian rocks, which lie unconformably on the Coal-measures; as is the case, also, in the immediate neighbourhood of Manchester, where they skirt the borders of the main coal-field, and consist of the Lower Red Sandstone, resting unconformably on different parts of the Coal-measures, and overlaid by the pebble-beds of the Trias.
At Stockport the Permian strata are stated by Mr. Hull to be more than 1,500 feet thick.
In Yorkshire, Nottinghamshire, and Derbyshire, the Permian strata are stated by Mr. Aveline to be divided into two chief groups: the Roth-liegende, of no great thickness, and the Magnesian Limestone series; the latter being the largest and most important member of the Permian series in the northern counties of England. The Magnesian Limestone consists there of two great bands, separated by marls and sandstone, and quarried for building and for lime. In Derbyshire and Yorkshire the magnesian limestone, under the name of Dolomite, forms an excellent building-stone, which has been used in the construction of the Houses of Parliament.
In the midland counties and on the borders of Wales, the Permian section is different from that of Nottinghamshire and the North of England. The Magnesian Limestones are absent, and the rocks consist principally of dark-red marl, brown and red sandstones, and calcareous conglomerates and breccias, which are almost entirely unfossiliferous. In Warwickshire, where they rest conformably on the Coal-measures, they occupy a very considerable tract of country, and are of very great thickness, being estimated by Mr. Howell to be 2,000 feet thick.
In the east of England the Magnesian Limestone contains a numerous marine fauna, but much restricted when compared with that of the Carboniferous period. The shells of the former are all small and dwarfed in size when compared with their congeners of Carboniferous times, when such there are, and in this respect, and the small number of genera, they resemble the living mollusca of the still less numerous fauna of the Caspian Sea.
Besides the poverty and small size of the mollusca, the later strata of the true Magnesian Limestone seem to afford strong indications that they may have been deposited in a great inland salt-lake subject to evaporation.
The absence of fossils in much of the formation may be partly accounted for by its deposition in great measure from solution, and the uncongenial nature of the waters of a salt-lake may account for the poverty-stricken character of the whole molluscan fauna.
The red colouring-matter of the Permian sandstones and marls is considered, by Professor Ramsay, to be due to carbonate of iron introduced into the waters, and afterwards precipitated as peroxide through the oxidising action of the air and the escape of the carbonic acid which held it in solution. This circumstance of the red colour of the Permian beds affords an indication that the red Permian strata were deposited in inland waters unconnected with the main ocean, which waters may have been salt or fresh as the case may be.
“The Magnesian Limestone series of the east of England may, possibly, have been connected directly with an open sea at the commencement of the deposition of these strata, whatever its subsequent history may have been; for the fish of the marl strata have generically strong affinities with those of Carboniferous age, some of which were truly marine, while others certainly penetrated shallow lagoons bordered by peaty flats.”[53]
There is indisputable evidence that the Permian ocean covered an immense area of the globe. In the Permian period this ocean extended from Ireland to the Ural mountains, and probably to Spitzbergen, with its northern boundary defined by the Carboniferous, Devonian, Silurian, and Igneous regions of Scotland, Scandinavia, and Northern Russia; and its southern boundaries apparently stretching far into the south of Europe (King). The chain of the Vosges, stretching across Rhenish Bavaria, the Grand Duchy of Baden, as far as Saxony and Silesia, would be under water. They would communicate with the ocean, which covered all the midland and western counties of England and part of Russia. In other parts of Europe the continent has varied very little since the preceding Devonian and Carboniferous ages. In France the central plateaux would form a great island, which extended towards the south, probably as far as the foot of the Pyrenees; another island would consist of the mass of Brittany. In Russia the continent would have extended itself considerably towards the east; finally, it is probable that, at the end of the Carboniferous period, the Belgian continent would stretch from the Departments of the Pas-de-Calais and Du Nord, in France, and would extend up to and beyond the Rhine.
In England, the Silurian archipelago, now filled up and occupied by deposits of the Devonian and Carboniferous systems, would be covered with carboniferous vegetation; dry land would now extend, almost without interruption, from Cape Wrath to the Land’s End; but, on its eastern shore, the great mass of the region now lying less than three degrees west of Greenwich would, in a general sense, be under water, or form islands rising out of the sea. Alphonse Esquiros thus eloquently closes the chapter of his work in which he treats of this formation in England: “We have seen seas, vast watery deserts, become populated; we have seen the birth of the first land and its increase; ages succeeding each other, and Nature in its progress advancing among ruins; the ancient inhabitants of the sea, or at least their spoils, have been raised to the summit of lofty mountains. In the midst of these vast cemeteries of the primitive world we have met with the remains of millions of beings; entire species sacrificed to the development of life. Here terminates the first mass of facts constituting the infancy of the British Islands. But great changes are still to produce themselves on this portion of the earth’s surface.”
Having thus described thePrimary Epoch, it may be useful, before entering on what is termed by geologists theSecondary Epoch, to glance backwards at the facts which we have had under consideration.
In this Primary period plants and animals appear for the firsttime upon the surface of the cooling globe. We have said that the seas of the epoch were then dominated by the fishes known asGanoids(from γανος,glitter), from the brilliant polish of the enamelled scales which covered their bodies, sometimes in a very complicated and fantastic manner; theTrilobitesare curious Crustaceans, which appear and altogether disappear in the Primary epoch; an immense quantity of Mollusca, Cephalopoda, and Brachiopoda; theEncrinites, animals of curious organisation, which form some of the most graceful ornaments of our Palæontological collections.
Fig. 77Fig. 77.—Lithostrotion. (Fossil Coral.)
Fig. 77.—Lithostrotion. (Fossil Coral.)
But, among all these beings, those which prevailed—those which were truly the kings of the organic world—were the Fishes, and, above all, theGanoids, which have left no animated being behind them of similar organisation. Furnished with a sort of defensive armour, they seem to have received from Nature this means of protection to ensure their existence, and permit them to triumph over all the influences which threatened them with destruction in the seas of the ancient world.
Fig. 78Fig. 78.—Rhyncholites, upper, side, and internal views. 1, Side view (Muschelkalk of Luneville); 2, Upper view (same locality); 3, Upper view (Lias of Lyme Regis); 4, Calcareous point of an under mandible, internal view, from Luneville. (Buckland.)
Fig. 78.—Rhyncholites, upper, side, and internal views. 1, Side view (Muschelkalk of Luneville); 2, Upper view (same locality); 3, Upper view (Lias of Lyme Regis); 4, Calcareous point of an under mandible, internal view, from Luneville. (Buckland.)
In the Primary epoch the living creation was in its infancy. No Mammals then roamed the forests; no bird had yet displayed its wings. Without Mammals, therefore, there was no maternal instinct; none of the soft affections which are, with animals, as it were, the precursors of intelligence. Without birds, also, there could be no songs in the air. Fishes, Mollusca, and Crustacea silently ploughed their way in the depths of the sea, and the immovable Crinoid lived there. On the land we only find a few marsh-frequenting Reptiles, ofsmall size—forerunners of those monstrous Saurians which make their appearance in the Secondary epoch.
The vegetation of the Primary epoch is chiefly of inferior organisation. With a few plants of a higher order, that is to say, Dicotyledons, Calamites, Sigillarias, it was the Cryptogamia (also several species of Ferns, the Lepidodendra, Lycopodiaceæ, and the Equisetaceæ, and some doubtfully allied forms, termed Nöggerathia), then at their maximum of development, which formed the great mass of the vegetation.
Let us also consider, in this short analysis, that during the epoch under consideration, what we callclimatemay not have existed. The same animals and the same plants then lived in the polar regions as at the equator. Since we find, in the Primary formations of the icy regions of Spitzbergen and Melville Islands, nearly the same fossils which we meet with in these same rocks in the torrid zone, we must conclude that the temperature at this epoch was uniform all over the globe, and that the heat of the earth itself was sufficiently high to render inappreciable the calorific influence of the sun.
During this same period the progressive cooling of the earth occasioned frequent ruptures and dislocations of the ground; the terrestrial crust, in opening, afforded a passage for the rocks calledigneous, such as granite, afterwards to the porphyries and syenites, which poured slowly through these immense fissures, and formed mountains of granite and porphyry, or simple clefts, which subsequently became filled with oxides and metallic sulphides, forming what are now designated metallic veins. The great mountain-range of Ben Nevis offers a striking example of the first of these phenomena; through the granite base a distinct natural section can be traced of porphyry ejected through the granite, and of syenite through the porphyry. These geological commotions (which occasioned, not over the whole extent of the earth, but only in certain places, great movements of the surface) would appear to have been more frequent at the close of the Primary epoch; during the interval which forms the passage between the Primary and Secondary epochs; that is to say, between the Permian and the Triassic periods. The phenomena of eruptions, and the character of the rocks called eruptive, are treated of in a former chapter.
Fig. 79Fig. 79.a, Pentacrinites Briareus, reduced;b, the same from the Lias of Lyme Regis; natural size.
Fig. 79.a, Pentacrinites Briareus, reduced;b, the same from the Lias of Lyme Regis; natural size.
The convulsions and disturbances by which the surface of the earth was agitated did not extend, let it be noted, over the whole of its circumference; the effects were partial and local. It would, then, be wrong to affirm, as is asserted by many modern geologists, that the dislocations of the crust and the agitations of the surface of the globeextended to both hemispheres, resulting in the destruction of all living creatures. The Fauna and Flora of the Permian period did not differ essentially from the Fauna and Flora of the Coal-measures, which shows that no general revolution occurred to disturb the entire globe between these two epochs. Here, then, as in all analogouscases, it is unnecessary to recur to any general cataclysm to explain the passage from one epoch to another. Have we not, almost in our our own day, seen certain species of animals die out and disappear, without the least geological revolution? Without speaking of the Beaver, which abounded two centuries ago on the banks of the Rhône, and in the Cévennes, which still lived at Paris in the little river Bièvre in the middle ages, its existence being now unknown in these latitudes, although it is still found in America and other countries, we could cite many examples of animals which have become extinct in times by no means remote from our own. Such are theDinornisand theEpyornis, colossal birds of New Zealand and Madagascar, and theDodo, which lived in the Isle of France in 1626.Ursus spelæus,Cervus Megaceros,Bos primigenius, are species of Bear, Deer, and Ox which were contemporary with man, but have now become extinct. In France we no longer know the gigantic wood-stag, figured by the Romans on their monuments, and which they had brought from England for the fine quality of its flesh. The Erymanthean boar, so widely dispersed during the ancient historical period, no longer exists among our living races, any more than the Crocodileslacunosusandlaciniatusfound by Geoffroy St.-Hilaire in the catacombs of ancient Egypt. Many races of animals figured in the mosaics of Palestrina, engraved and painted along with species now actually existing, are no longer found living in our days any more than are the Lions with curly manes, which formerly existed in Syria, and perhaps even in Thessaly and the northern parts of Greece. From what happens in our own time, we may infer what has taken place in times antecedent to the appearance of man; and the idea of successive cataclysms of the globe, must be restrained within bounds. Must we imagine a series of geological revolutions to account for the disappearance of animals which have evidently become extinct in a natural way? What has come to pass in our days, it is reasonable to conclude, may have taken place in the times anterior to the appearance of man.
Fig. 80Fig. 80.—Terebellaria ramosissima. (Recent Coral.)
Fig. 80.—Terebellaria ramosissima. (Recent Coral.)
[34]Trans. Roy. Irish Acad., vol. xxiii., p. 556.[35]“On the Red Rocks of England,” by A. C. Ramsay.Quart. Jour. Geol. Soc., vol. xxvii., p. 250.[36]Quart. Jour. Geol. Soc., vol. iii., p. 159.[37]“The Flora and Fauna of the Silurian Period,” by John T. Bigsby, M.A., F.G.S. 4to, 1868.[38]Ibid, p. vi.[39]“Siluria,” p. 148.[40]“On the Red Rocks of England,” by A. C. Ramsay.Quart. Jour. Geol. Soc., vol. xxvii., p. 243.[41]“On the Red Rocks of England,” by A. C. Ramsay.Quart. Jour. Geol. Soc., vol. xxvii., p. 247.[42]For fuller details on this subject, see J. B. Jukes’ “Manual of Geology,” 3rd ed., p. 762. Also, R. Etheridge,Quart. Journ. Geol. Soc., vol. 23, p. 251.[43]Quart. Jour. Geol. Soc., vol. xxii., p. 129.[44]“Elements of Geology,” p. 480.[45]Ibid, p. 479.[46]Ibid, p. 479.[47]Ibid, p. 483.[48]“Introduction to Geology,” by Robert Bakewell, 5th ed., p. 179. 1838.[49]For the opinions respecting theStigmaria ficoides, see a Memoir on “The Formation of the Rocks in South Wales and South-Western England,” by Sir Henry T. De la Beche, F.R.S., in the “Memoirs of the Geological Survey of Great Britain,” vol. i., p. 149.[50]See “Siluria,” p. 14.Philosophical Mag., 3rd series, vol. xix., p. 419.[51]A. C. Ramsay, “On the Red Rocks of England.”Quart. Jour. Geol. Soc., vol. xxvii., p. 246.[52]“Elements of Geology,” p. 456.[53]“On the Red Rocks of England,” by A. C. Ramsay.Quart. Jour. Geol. Soc., vol. xxvii., p. 246.
[34]Trans. Roy. Irish Acad., vol. xxiii., p. 556.
[35]“On the Red Rocks of England,” by A. C. Ramsay.Quart. Jour. Geol. Soc., vol. xxvii., p. 250.
[36]Quart. Jour. Geol. Soc., vol. iii., p. 159.
[37]“The Flora and Fauna of the Silurian Period,” by John T. Bigsby, M.A., F.G.S. 4to, 1868.
[38]Ibid, p. vi.
[39]“Siluria,” p. 148.
[40]“On the Red Rocks of England,” by A. C. Ramsay.Quart. Jour. Geol. Soc., vol. xxvii., p. 243.
[41]“On the Red Rocks of England,” by A. C. Ramsay.Quart. Jour. Geol. Soc., vol. xxvii., p. 247.
[42]For fuller details on this subject, see J. B. Jukes’ “Manual of Geology,” 3rd ed., p. 762. Also, R. Etheridge,Quart. Journ. Geol. Soc., vol. 23, p. 251.
[43]Quart. Jour. Geol. Soc., vol. xxii., p. 129.
[44]“Elements of Geology,” p. 480.
[45]Ibid, p. 479.
[46]Ibid, p. 479.
[47]Ibid, p. 483.
[48]“Introduction to Geology,” by Robert Bakewell, 5th ed., p. 179. 1838.
[49]For the opinions respecting theStigmaria ficoides, see a Memoir on “The Formation of the Rocks in South Wales and South-Western England,” by Sir Henry T. De la Beche, F.R.S., in the “Memoirs of the Geological Survey of Great Britain,” vol. i., p. 149.
[50]See “Siluria,” p. 14.Philosophical Mag., 3rd series, vol. xix., p. 419.
[51]A. C. Ramsay, “On the Red Rocks of England.”Quart. Jour. Geol. Soc., vol. xxvii., p. 246.
[52]“Elements of Geology,” p. 456.
[53]“On the Red Rocks of England,” by A. C. Ramsay.Quart. Jour. Geol. Soc., vol. xxvii., p. 246.
During thePrimary Epochour globe would appear to have been chiefly appropriated to beings which lived in the waters—above all, to the Crustaceans and Fishes; during theSecondary EpochReptiles seem to have been its prevailing inhabitants. Animals of this class assumed astonishing dimensions, and would seem to have multiplied in a most singular manner; they were, apparently, the kings of the earth. At the same time, however, that the animal kingdom thus developed itself, the vegetation lost much of its importance.
Geologists have agreed among themselves to divide the Secondary epoch into three periods: 1, theCretaceous; 2, theJurassic; 3, theTriassic—a division which it is convenient to adopt.
This period has received the name of Triassic because the rocks of which it is composed, which are more fully developed in Germany than either in England or France, were called the Trias (or Triple Group), by German writers, from its division into three groups, as follows, in descending order:—
The following has been shown by Mr. Ed. Hull to be the general succession of the Triassic formation in the midland and north-western counties of England, where it attains its greatest vertical development, thinning away in the direction of the mouth of the Thames:—
In this new phase of the revolutions of the globe, the animated beings on its surface differ much from those which belonged to the Primary epoch. The curious Crustaceans which we have described under the name ofTrilobiteshave disappeared; the molluscous Cephalopods and Brachiopods are here few in number, as are the Ganoid and Placoid Fishes, whose existence also seems to have terminated during this period, and vegetation has undergone analogous changes. The cryptogamic plants, which reached their maximum in the Primary epoch, become now less numerous, while the Conifers experienced a certain extension. Some kinds of terrestrial animals have disappeared, but they are replaced by genera as numerous as new. For the first time the Turtle appears in the bosom of the sea, and on the borders of lakes. The Saurian reptiles acquire a great development; they prepare the way for those enormous Saurians, which appear in the following period, whose skeletons present such vast proportions, and such a strange aspect, as to strike with astonishment all who contemplate their gigantic, and, so to speak, awe-inspiring remains.
TheVariegated Sandstone, or Bunter, contains many vegetable, but few animal, remains, although we constantly find imprints of the footsteps of the Labyrinthodon.
The lowest Bunter formation shows itself in France, in the Pyrenees, around the central plateau in the Var, and upon both flanks of the Vosges mountains. It is represented in south-western and central Germany, in Belgium, in Switzerland, in Sardinia, in Spain, in Poland, in the Tyrol, in Bohemia, in Moravia, and in Russia. M. D’Orbigny states, from his own observation, that it covers vast surfaces in the mountainous regions of Bolivia, in South America. It is recognised in the United States, in Columbia, in the Great Antilles, and in Mexico.
The Bunter in France is reduced to the variegated sandstone, except around the Vosges, in the Var, and the Black Forest, where it is accompanied by the Muschelkalk. In Germany it furnishes building-stone of excellent quality; many great edifices, in particular the cathedrals, so much admired on the Rhine—such, for example, as those of Strasbourg and Fribourg—are constructed of this stone, the sombre tints of which singularly relieve the grandeur and majesty of the Gothic architecture. Whole cities in Germany are built of the brownish-red stones drawn from its mottled sandstone quarries. InEngland, in Scotland, and in Ireland this formation extends from north to south through the whole length of the country. “This old land,” says Professor Ramsay,[54]“consisted in great part of what we now know as Wales, and the adjacent counties of Hereford, Monmouth, and Shropshire; of part of Devon and Cornwall, Cumberland, the Pennine chain, and all the mountainous parts of Scotland. Around old Wales, and part of Cumberland, and probably all round and over great part of Devon and Cornwall, the New Red Sandstone was deposited. Part, at least, of this oldest of the Secondary rocks was formed of the material of the older Palæozoic strata, that had then risen above the surface of the water. The New Red Sandstone series consists in its lower members of beds of red sandstone and conglomerate, more than 1,000 feet thick, and above them are placed red and green marls, chiefly red, which in Germany are called the Keuper strata, and in England the New Red Marl. These formations range from the mouth of the Mersey, round the borders of Wales, to the estuary of the Severn, eastwards into Warwickshire, and thence northwards into Yorkshire and Northumberland, along the eastern border of the Magnesian Limestone. They also form the bottom of the valley of the Eden, and skirt Cumberland on the west; in the centre of England the unequal hardness of its sub-divisions sometimes giving rise to minor escarpments, overlooking plains and undulating grounds of softer strata.”
“Different members of the group rest in England, in some region or other,” says Lyell, “on almost every principal member of the Palæozoic series, on Cambrian, Silurian, Devonian, Carboniferous, and Permian rocks; and there is evidence everywhere of disturbance, contortion, partial upheaval into land, and vast denudations which the older rocks underwent before and during the deposition of the successive strata of the New Red Sandstone group.” (“Elements of Geology,” p. 439.)
TheMuschelkalkconsists of beds of compact limestone, often greyish, sometimes black, alternating with marl and clay, and commonly containing such numbers of shells that the name of shelly limestone (Muschelkalk) has been given to the formation by the Germans. The beds are sometimes magnesian, especially in the lower strata, which contain deposits of gypsum and rock-salt.
The seas of this sub-period, which is named after the innumerable masses of shells inclosed in the rocks which it represents, included, besides great numbers of Mollusca, Saurian Reptiles of twelve differentgenera, some Turtles, and six new genera of Fishes clothed with a cuirass. Let us pause at the Mollusca which peopled the Triassic seas.
Fig. 81Fig. 81.—Ceratites nodosus. (Muschelkalk.)
Fig. 81.—Ceratites nodosus. (Muschelkalk.)
Among the shells characteristic of the Muschelkalk period, we mentionNatica Gaillardoti,Rostellaria antiqua,Lima striata,Avicula socialis,Terebratula vulgaris,Turbonilla dubia,Myophoria vulgaris,Nautilus hexagonalis, andCeratites nodosus. TheCeratites, of which a species is here represented (Fig. 81), form a genus closely allied to theAmmonites, which seem to have played such an important part in the ancient seas, but which have no existence in those of our era, either in species or even in genus. This Ceratite is found in the Muschelkalk of Germany, a formation which has no equivalent in England, but which is a compact greyish limestone underlying the saliferous rocks in Germany, and including beds of dolomite with gypsum and rock-salt.
TheMytilusorMussel, which properly belonged to this age, are acephalous (or headless) Molluscs with elongated triangular shells, of which there are many species found in our existing seas.Lima,Myophoria,Posidonia, andAvicula, are acephalous Molluscs of the same period. The two generaNaticaandRostellariabelong to the Gasteropoda, and are abundant in the Muschelkalk in France, Germany, and Poland.
Fig. 82Fig. 82.—Encrinus liliiformis.
Fig. 82.—Encrinus liliiformis.
Among the Echinoderms belonging to this period may be mentionedEncrinus moniliformisandE. liliiformis, orlily encrinite(Fig. 82), whose remains, constituting in some localities whole beds of rock, show the slow progress with which this zoophyte formed beds of limestone in the clear seas of the period. To these may be added, among the Mollusca,Avicula subcostataandMyophoria vulgaris.
In the Muschelkalk are found the skull and teeth ofPlacodus gigas, a reptile which was originally placed by Agassiz among the class of Fishes; but more perfect specimens have satisfied Professor Owen that it was a Saurian Reptile.
It may be added, that the presence of a few genera, peculiar to the Primary epoch, which entirely disappeared during the sub-period,and the appearance for the first time of some other animals peculiar to the Jurassic period, give to the Muschelkalk fauna the appearance of being one of passage from one period to the other.
Fig. 83Fig. 83.—Labyrinthodon restored. One-twentieth natural size.
Fig. 83.—Labyrinthodon restored. One-twentieth natural size.
The seas, then, contained a few Reptiles, probably inhabitants of the banks of rivers, asPhytosaurus,Capitosaurus, &c., and sundry Fishes, asSphœrodusandPycnodus. In this sub-period we shall say nothing of the Land-Turtles, which for the first time now appear; but, we should note, that at the Bunter period a gigantic Reptile appears, on which the opinions of geologists were for a long while at variance. In the argillaceous rocks of the Muschelkalk period imprints of the foot of some animal were discovered in the sandstones of Storeton Hill, in Cheshire, and in the New Red Sandstone of parts of Warwickshire, as well as in Thuringia, and Hesseburg in Saxony, which very much resembled the impression that might be made in soft clay by the outstretched fingers and thumb of a human hand. These traces were made by a species of Reptile furnished with four feet, the two fore-feet being much broader than the hinder two. The head, pelvis, and scapula only of this strange-looking animal have been found, but these are considered to have belonged to a gigantic air-breathing reptile closely connected with the Batrachians. It is thought that the head was not naked, but protected by a bony cushion; that its jaws were armed with conical teeth, of great strength and of a complicated structure. This curious and uncouth-looking creature, of which the woodcutFig. 83is a restoration, has been named theCheirotherium, orLabyrinthodon, from the complicated arrangement of the cementing layer of the teeth. (See alsoFig. 1, p. 12.)
Another Reptile of great dimensions—which would seem to have been intended to prepare the way for the appearance of the enormous Saurians which present themselves in the Jurassic period—was theNothosaurus, a species of marine Crocodile, of which a restoration has been attempted inPlate XIII.opposite.
Plate XIIIXIII.—Ideal Landscape of the Muschelkalk Sub-period.
XIII.—Ideal Landscape of the Muschelkalk Sub-period.
It has been supposed, from certain impressions which appear in the Keuper sandstones of the Connecticut river in North America,that Birds made their appearance in the period which now occupies us; the flags on which these occur by thousands show the tracks of an animal of great size (some 20 inches long and 41⁄2feet apart), presenting the impression of three toes, like some of the Struthionidæ or Ostriches, accompanied by raindrops. No remains of the skeletons of birds have been met with in rocks of this period, and the footprints in question are all that can be alleged in support of the hypothesis.
M. Ad. Brongniart places the commencement of dicotyledonous gymnosperm plants in this age. The characteristics of this Flora consist in numerous Ferns, constituting genera now extinct, such asAnomopterisandCrematopteris. The trueEquisetaare rare in it. The Calamites, or, rather, theCalamodendra, abound. The gymnosperms are represented by the generaConifer,Voltzia, andHaidingera,of which both species and individuals are very numerous in the formation of this period.
Among the species of plants which characterise this formation, we may mentionNeuropteris elegans,Calamites arenaceus,Voltzia heterophylla,Haidingera speciosa. TheHaidingera, belonging to the tribe ofAbietinæ, were plants with large leaves, analogous to those of ourDamara, growing close together, and nearly imbricated, as in theAraucaria. Their fruit, which are cones with rounded scales, are imbricated, and have only a single seed, thus bearing out the strong resemblance which has been traced between these fossil plants, and the Damara.
Fig. 84Fig. 84.—Branch and cone of Voltzia restored.
Fig. 84.—Branch and cone of Voltzia restored.
TheVoltzias(Fig. 84), which seem to have formed the greater part of the forests were a genus of Cupressinaceæ, now extinct, which are well characterised among the fossil Conifers of the period. The alternate spiral leaves, forming five to eight rows sessile, that is, sitting close to the branch and drooping, have much in them analogous to theCryptomerias. Their fruit was an oblong cone with scales, loosely imbricated, cuneiform or wedge-shaped, and, commonly, composed of from three to five obtuse lobes. InFig. 84we have a part of the stem, a branch with leaves and cone. In his “Botanic Geography,” M. Lecoq thus describes the vegetation of the ancient world in the first period of the Triassic age: “While the variegated sandstone and mottled clays were being slowly deposited in regular beds by the waters, magnificent Ferns still exhibited their light and elegantly-carved leaves. DiversProtopterisand majesticNeuropterisassociated themselves in extensive forests, where vegetated also theCrematopteris typicaof Schimper, theAnomopteris Mongeotiiof Brongniart, and the prettyTrichomanites myriophyllum(Göppert). The Conifers of this epoch attain a very considerable development, and would form graceful forests of green trees. Elegant monocotyledons, representing the forms of tropical countries, seem to show themselves for the first time, theYuccites Vogesiacusof Schimper constituted groups at once thickly serried and of great extent.
“A family, hitherto doubtful, appears under the elegant form ofNilssonia Hogardi, Schimp.;Ctenis Hogardi, Brongn. It is still seen in theZamites Vogesiacus, Schimp.; and the group of the Cycads sharing at once in the organisation of the Conifers and the elegance of the Palms, now decorate the earth, which reveals in these new forms its vast fecundity. (SeeFig. 72, p. 168.)
“Of the herbaceous plants which formed the undergrowth of the forests, or which luxuriated in its cool marshes, the most remarkable is theÆtheophyllum speciosum, Schimp. Their organisation approximatesto the Lycopodiaceæ and Thyphaceæ, theÆtheophyllum stipulare, Brongn., and the curiousSchizoneura paradoxa, Schimp. Thus we can trace the commencement of the reign of the Dicotyledons with naked seeds, which afterwards become so widely disseminated, in a few Angiosperms, composed principally of two families, the Conifers and Cycadeaceæ, still represented in the existing vegetation. The former, very abundant at first, associated themselves with the cellular Cryptogams, which still abound, although they are decreasing, then with the Cycadeaceæ, which present themselves slowly, but will soon be observed to take a large part in the brilliant harmonies of the vegetable kingdom.”
The engraving at page 191 (Plate XIII.) gives an idealised picture of the plants and animals of the period. The reader must imagine himself transported to the shores of the Muschelkalk sea at a moment when its waves are agitated by a violent but passing storm. The reflux of the tide exposes some of the aquatic animals of the period. Some fine Encrinites are seen, with their long flexible stems, and a few Mytili and Terebratulæ. The Reptile which occupies the rocks, and prepares to throw itself on its prey, is theNothosaurus. Not far from it are other reptiles, its congeners, but of a smaller species. Upon the dune on the shore is a fine group of the trees of the period, that is, ofHaidingeras, with large trunks, with drooping branches and foliage, of which the cedars of our own age give some idea. The elegantVoltziasare seen in the second plane of this curtain of verdure. The Reptiles which lived in these primitive forests, and which would give to it so strange a character, are represented by theLabyrinthodon, which descends towards the sea on the right, leaving upon the sandy shore those curious tracks which have been so wonderfully preserved to our days.
The footprints of the reptilian animals of this period prove that they walked over moist surfaces; and, if these surfaces had been simply left by a retiring tide, they would generally have been obliterated by the returning flood, in the same manner that is seen every day on our own sandy shores. It seems more likely that the surfaces, on which fossil footprints are now found, were left bare by the summer evaporation of a lake; that these surfaces were afterwards dried by the sun, and the footprints hardened, so as to ensure their preservation, before the rising waters brought by flooded muddy rivers again submerged the low flat shores and deposited new layers of salt, just as they do at the present day round the Dead Sea and the Salt Lake of Utah.