its close, we find that the fishes assumed their maximum of development, at least in the placoid and ganoid orders, for at this time the reptilian fishes and sharks were both numerous and powerful, while very soon afterwards the whole tribe of fishes was represented by animals of smaller dimensions, of different habit, and comparatively powerless. It is very interesting in this case to watch the progress of the transition. The fishes in the carboniferous rocks, include many large shark-like and reptilian groups. In the sandstone above the coal, and in the magnesian limestone, are many nearly allied fishes, although of much smaller size, but all the more advanced types seem to fail. In the same newer beds, however, appear true reptiles, not indeed of large size, but of complicated dentition, and the representatives of a high group; while, as we shall hereafter find, in the beds of the secondary period the reptiles at first exhibit high analogies and then pass off into a magnificent series, including true representatives both of the earlier sauroid fishes and the later aquatic mammals. On the other hand, the fishes there exhibit a lower form of higher groups, afterwards continued and advanced to the most complicated types, but only attaining a gigantic size in rocks of far newer date. The bearing of these points on the general question of development we shall have occasion afterwards to allude to.

THE SECOND OR MIDDLE EPOCH.

CHAPTER VII.

THE COMMENCEMENT OF THE SECOND EPOCH-THE FORMATION OF THE NEW RED SANDSTONE, OR TRIASSIC SERIES.

OVER a large part of the known world, the close of the first epoch, marked by great subsidences of land, by the swallowing up of continents and islands into the sea, and by accompanying violent dislocations of the stratified crust of the globe, was of necessity accompanied by the re-distribution of these fractured materials of strata; and, owing no doubt to the great amount of trituration, the beds thus formed contain but few remains of organic beings. These, however, indicate the commencement of the new era.

The presence of the new red sandstone, a formation consisting of sand and marl with rare local interpolations of limestone, characterises this epoch ; and, after this, until towards the close of the secondary or middle period, we find few intermediate beds over the whole of America; * and the same is the case with regard to the greater part of Asia and Australia, as far as Geologists have yet been able to determine. In England we have this chapter of the history

* There is, indeed, one magnificent exception in the Richmond oolitic coal-field of Virginia, U. S., where the beds of coal are of vast extent, and rival those of the true carboniferous period.

much more fully developed. The new red sandstone itself, it is true, consists of little more than loose sand and mud, deposited, perhaps rapidly, from the fractured rocks of the earlier period. It is, therefore, very poor in fossils, and exhibits but few of these hieroglyphics whose language we can interpret; and, although richer in this respect than England, the whole continent of Europe is marked by a similar comparative rarity of organic remains in the beds. But afterwards, it would appear that, the subsidence not having been complete, there remained in our latitudes a number of islands, forming an archipelago not unfavourable to the existence of many races of animals and vegetables, especially those capable of supporting life in spite of constant oscillations and changes of condition of the surface.

We have seen that, even up to the very close of the earlier epoch, there is no distinct and unquestionable evidence of the nature and position of the land on which grew the vast forests from which coal was elaborated. Here and there it has seemed that the trees of which we find fragments must have grown on the spot where broken trunks are now apparently attached to their roots, the roots and trunks being buried together in the very soil from which they obtained their nourishment. But these instances are rare and exceptional; and although we may be certain that the land was not far off, yet its exact position, and whether it was a continent or an island, or a group of islands, whether it extended southwards or northwards, whether it occupied what is now the Atlantic Ocean, or was shaped like Europe, and represented the two north-eastern continents, we

cannot satisfactorily determine. Perhaps the most probable opinion is, that an extensive archipelago, like that near the eastern shores of Asia, was the remnant of a sinking tract throughout a great part of the north temperate zone; that portions of that tract, now forming parts of England and central Europe, remained thus for a long time in shallow water, the recipients of many deposits; but that during this time the other tracts were too deeply submerged and too far from land to receive such additions.

Whatever the cause may have been, the result, so far as concerned the inhabitants both of sea and land, was sufficiently remarkable. Between the close of the older epoch and the commencement of this, which we call the middle, every species, both of animal and vegetable, seems to have been, almost without exception, changed. All the older forms have disappeared ; all the modifications up to that time introduced have vanished; many even of the larger groups are SO greatly altered, and have become so rare, that they also have nearly died out, either from the lapse of time or change of condition; and we have thus a new creation,―a new world, as it seems, supplying the gap produced by the mighty change, whatever it may have been, which closed one epoch of the earth's history and commenced a second.

But next in importance to the fact that this change has taken place to so great an extent, is a fact no less certain, that some species of one of the principal groups of the higher animals-the reptiles were unquestionably introduced before the change took place; and this dawn of reptilian existence, observable in the magnesian limestone, gradually opens

Fig. 44

out into the broadest and fullest development of these singular animals, without exhibiting any marks of interruption, and as if there had been little or no disturbing action. Thus we have a link connecting the chain of beings, and uniting two conditions so dissimilar that whole families of fishes and invertebrated animals were unable to endure them; and this link moreover is one of great importance, and, as it might have seemed to us, the one least likely to be selected for this purpose. It may ultimately be found to have reference to the permanent elevation above the water of some portion of the land, while the sea bottom was undergoing great change of level.

The seas of the new red sandstone period were not favourable to the development of the coral animal, but numerous radiated animals existed, of which the most interesting is that known to fossilcollectors by the name of the lily encrinite (fig. 44).

This animal was one of a singular group already described (see p. 34), inclosed within a stony habitation, and planted upon a (Encrinites moniliformis.) stony but moveable column nearly cylindrical, and attached at its

STONE LILY.

base to the solid rock. From the pouch, which is divided into five parts, as many pairs of smaller