rocercal, the tail being unequally lobed as in fig. 1, which is the tail of the shark, and the vertebral column running along the upper lobe. On the other hand, in nearly all the living species,

the tail is homocercal as in fig. 2, which is the tail of a herring, the vertebral column not extending to the upper lobe.

We have remarked that the first tracks of reptiles are met with in this system of deposits. Below we represent the appearance of these footprints as observed in England and Germany.

It

will be perceived that there are two impressions which always accompany each other, and they are not unlike the human hand, hence the animal was named cheirotherium or hand beast. This animal was for a long time supposed to be allied to the kangaroo, and like it a marsupial, i. e. having a pouch in which to carry its young; but more recently Prof. Owen, from a careful examination of teeth and other bones found in the new red sandstone, has determined it to belong to the class of batrachians, or frogs, toads, salamanders, &c., and from the peculiar structure of its teeth, he has given to this genus the name labyrinthodon, or labyrinth tooth. Besides the tracks just described, are found those of turtles, of a little lizard with a bird-like beak, and the trails of molluscs, and vermes, and the ripple marks of the ancient seas. By far the most remarkable tracks occurring in the new red sandstone group, are those of gigantic birds, the foot-prints being seventeen inches long, and the stride of the bird from four to six feet. It is somewhat remarkable that nearly all the fossil foot

marks yet discovered, occur upon some member of the new red sandstone group. On the same stone are impressions of rain drops. "It is a most interesting thought," observes Prof. Hitchcock, "that while millions of men who have striven hard to transmit some trace of their existence to future generations, have sunk into utter oblivion, the simple footsteps of animals, that existed thousands, nay, tens of thousands of years ago, should remain as fresh and distinet as if yesterday impressed; even though nearly every other vestige of their existence has vanished. Nay still more strange is it, that even the pattering of a shower at that distant period, should have left marks equally distinct, and registered with infallible certainty the direction of the wind." When these foot prints were first discovered their enormous size seemed an insuperable objection to the opinion that they were bird tracks. But recently in the island of New Zealand, the bones of an immense wingless bird have been found to which the name Dinornis, or terrible bird, has been given. Below is an outline representing the size of this extraordinary animal compared with a man.

Immediately above the new red sandstone in some parts of the

world, but particularly in England, is deposited a fine sandy and marly stratum, consisting of distinct layers with occasional limestones, and exceedingly abundant in remarkable fossil remains. To this the name Lias has been given, and the reptilian remains imbedded in it are the most magnificent objects of the Creator's hand. During the deposit of these muddy beds which were unfavorable to the growth of corals, we find but few traces of these animals, but on the contrary the crinoidea, already alluded to, were developed in singular and beautiful forms, and also very peculiar forms of the cephalapodic group. Among the marine reptiles of the epoch we are now considering, two are particularly noticeable. The Plesiosaurus, or almost lizard, and the Ichthyosaurus, or fish lizard. Below we represent the plesiosarus, which possesses a head small, and lizard-like, with teeth like a croco

inches across. The jaws are long and furnished with sharp conical teeth, resembling those of the crocodile, and like them replaced continually, as they become worn, by new ones; the fins or paddles were four. Both these remarkable animals, now entirely extinct, are figured in the frontispiece of the present volume, which is designed to represent the condition of our globe during the period we are now considering.

Above the lias shales is a deposit which seems to indicate great changes in the organic world, caused by the elevation of wide tracts of country over certain portions of the globe, attended with numerous depressions in other parts, and the strata deposited during these movements seems to have formed the bed or final depository of many successive races of beings. The name Oolite given to this group of deposits signifies egg-like stone, because it is formed of small egg-like grains, like those comprising the roe of a fish, the nucleus of which, on microscopic examination, appears to be some minute organic substance, usually a fragment of coral, or a shell. To this class belong the so-called Oxford and Kimmeredge clays, and the Jura limestone, since the mass of the Jura mountains in France is of the oolite formation. During this period, an immense number of marine animals flourished, most of which are now entirely extinct, among them are peculiar corals, star-fishes, and sea-eggs or echini. Below we give a representation of a very perfect crustacean, similar to the

The fossil

lobster, from the oolite clay of Yorkshire, England. remains of insects are also common in these strata, and very peculiar and beautiful forms of ammonite, which seems to have

We have before

been most perfectly developed in the lias seas. described a cephalapod called the orthoceratite, (page 306), subsequently we find this animal displaced by one with a curved and somewhat angular shell during the carboniferous formation, still later during the deposition of the lias and oolitic beds, we find another change under the form of the ammonite; at the same time the nautilus, a well known cephalapodous animal, closely related to the ammonite, was likewise abundant. The nautilus still inhabits our tropical seas, and unfolds its fleshy sails to the gentle breezes, but long since the ammonite has been extinct. Another of the same class or group of animals, and which is now represented by the cuttle-fish, is the animal of the belemnite. The fossil called the belemnite from its resemblance to a dart or javelin, is not uncommon, and is found of various lengths and is

1

2

sometimes called by the singular names of the devil's toe-nail, thunderbolt, &c.; the general appearance of the fossil is however as represented in fig. 1, and perhaps no organic remains have ever caused more ludicrous mistakes, or given rise to more fauciful theories. It is the internal skeleton of an animal very much like the cuttle-fish, and represented in fig. 2. From the fossil remains, this animal appears to have been exceedingly large and formidable, preying upon the smaller fishes and reptiles, it was furished with eight long arms, each provided with from fifteen to twenty hooks; the eyes were large and the jaws powerful. Like the common squid, it seems to have been provided with an oval sac, containing a dark fluid, ejected by the animal when alarmed in order to discolor the water and facilitate its escape. During