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a continent or an island, or a succession of islands, and such like queries, are not at present capable of being answered. Neither do we learn much more definitely the general character of the animals and vegetables that were indigenous. A few fragments of fossil wood found in England are evidence of the fact that the land was partly clothed with large pine-like trees; and a few casts of shells show that its shores were peopled with some species of mollusca. Elsewhere, when the conditions have been more favourable for the deposition and preservation of organic remains, as in some districts on the Continent, we find still a comparative poverty. Plants, indeed, abound, and exhibit characters unlike those of the coal period; a bed of limestone (the Muschelkalk) contains numerous shells, and the remains of fishes and reptiles; but, on the whole, the general features remain obscure. It would almost seem that at this time, and in most districts which we can examine, there had been a destruction of the previous species, and that a sufficient time had not yet elapsed for the newly introduced groups to spread over the earth and seas. However this may be, we cannot doubt the fact that there had been great and sudden changes, whether these were or were not connected with an interruption of the order of succession, and with the termination of one geological period, and the commencement of a second. The new red sandstone affords material for a distinct chapter in the earth's history, and though it is certainly a chapter containing less detail and fewer points for minute description than many others, it does not fail to suggest important generalisations.
THE MARINE REPTILES, AND OTHER ANIMALS CHARACTERISTIC OF THE LIAS.
THE deposit of sand and marly beds, which must have been steadily continued for a long time over extensive tracts at the commencement of the secondary period, seems to have gradually changed to a finer, more calcareous, and less sandy mud thrown down from suspension in water, perhaps after it had been carried for some distance by marine currents. This deposit of mud was local, since, so far as we can tell by examining the tracts now above water, it was almost confined to a part of England and a narrow tract in the middle of Europe, though it has been thought traceable in the middle of Asia, and is possibly represented in a small part of South America. The bed is sometimes more or less sandy or calcareous; but we know of few contemporaneous deposits; and where the muddy beds do not appear, there is often nothing intermediate between the new red sandstone and the newest beds of the middle epoch.
The most distinct beds of passage between the new red sandstone and this next superior stratum, (which is called lias,) are certain deposits at Aust Cliff, at the mouth of the Severn, where there is a thin bed absolutely made up of organic remains. There are also others on the continent of Europe, in
the south of Belgium, near Luxemburg. In these cases the first and most important indications of change are seen in the increased proportion of argillaceous matter, accompanied often by carbonate of lime. The character of a calcareous clay, sometimes passing into a muddy limestone, may be traced in most of the varieties of this formation.
The lias is everywhere singularly rich in the remains of organic existence; these remains extending through almost all the tribes of marine animals, and including, though rarely, fragments of wood and other vegetable bodies. No conclusion, indeed, can be drawn as to the nearness or distance of the land whence these fragments floated, for they are often covered with marine animals; but since, as will be seen, it is not unlikely that many of the monsters of the deep at this time repaired to the shallows, or even to the shore, to deposit their eggs, we may, perhaps, be allowed to conjecture that the land was not far distant from the spots now occupied by these strata.
The muddy liassic beds deposited after the sandstones described in the previous chapter, although they contained a considerable proportion of carbonate of lime, were not in a condition favourable for the development of coralline existence, and the remains of such animals are accordingly rare. This is not the case, however, with the closely allied group of Zoophytes known as the Crinoidea; for they, on the other hand, were singularly abundant, and were manifestly an important group, perhaps assisting to clear the
* So named probably from the appearance of the bed in riband-like layers of different colours observed in some parts of England.
seas of an undue proportion of the minuter particles of decaying animal matter. The most singular of all these is the Pentacrinite, an animal so complicated that the number of separate pieces of stone of which its singular skeleton is made up has been calculated to amount to not less than one hundred and fifty thousand. Like the other encrinites (see fig. 44, p. 118), it was provided with a long and powerful but moveable column, made up of a vast multitude of lozenge-shaped pieces (see fig. 51), each marked with a curious set of indentations, and each pierced with a cen tral aperture (52,) by means of which a communication was kept up during life, enabling the animal probably to attach itself to some marine substance, or a floating log of wood. In the Pentacrinite the stem (51, 52) was five-sided, and the body was partly defended by a small cup formed of regular plates rising from the column, and partly inclosed by a multitude of very minute and angular plates fixed on a tough membranous pouch terminating with an extensile proboscis. The body was surrounded also by an incredible multitude of branching arms, forming a complicated stony net-work, intended to intercept and convey to the stomach the particles of food fit for the animal, which were floating in the water within reach. Many specimens of this fossil are often found together, attached, it would seem, to
(Detached Piece and Section of the Stem.)
what was once the under surface of decayed wood drifting through the water.
Several varieties of star-fishes, and some curious forms not unlike certain recent crustaceans, were among the common tenants of the lias; and they were accompanied by a large number of animals inhabiting shells of various kinds, most of them very different from those known at present. Among these are both bivalves and univalves, the former including a good number of the Brachiopoda already referred to, and belonging to groups, such as Terebratula, still represented. The univalves, besides a considerable number having near relations with those of existing seas, include also a very large and important group, highly characteristic of the secondary period, and now absolutely extinct. I allude to the so-called Ammonites, the nearest analogue of which is the Nautilus, an animal most of whose peculiarities of structure are now known, although much has still to be learnt with regard to its habits. This animal (the nautilus) is almost our only guide in working out the various interesting points connected with the extinct but nearly allied group of which the ammonite is in some respects the most perfect type.
Reference has already been made, in speaking of the extinct forms of an earlier period, to the peculiar groups of cephalopodous animals whose remains are met with in the older rocks. Of these animals there are two well-marked groups represented at the present day, the one by the nautilus, and the other by the cuttle-fish. Of these, the former (see fig. 53) inhabits a univalve shell, divided into compartments by