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that not only the productions of the dry land have been changed during the convulsive revolutions of the globe, but the sea itself, the principal agent of the most part of these revolutions, has not preserved the same race of inhabitants; that when it formed in our neighbourhood those immense calcareous rocks, replete with shells at present almost all unknown, the great mammifera which it nourished were not those which people it at the present day; and that in spite of a strength commensurate with their enormous size, they have not been able to resist the turmoils of their own element; in the same way as the elephants, hippopotamuses, and rhinoceroses, the most robust of quadrupeds, fell victims on the surface of the earth to corresponding violence.

The bones of crocodiles form a very interesting group of animal remains. They are by no means rare in the deeper and more ancient secondary strata; and although they differ in species, they all belong to the long muzzled sub-genus, which Cuvier calls gavials.

In the year 1758, Woller and Chapmann found on the sea-shore in the Whitby alum-slate formation, the bones of an animal like a crocodile. The drawing which they gave in the Phil. Trans. vol. L. shows a contorted spine, 9 feet long, and a head somewhat out of place, 2 feet 9 inches in length. The head narrows anteriorly, not suddenly, but by degrees, as in the crocodiles of Altorf and Honfleur, into a pointed snout, which was covered in certain places with the remains of the lower jaw. At these places there appeared in both jaws, large

sharp-pointed teeth, placed alternately, and closely crossing each other; but where the under jaw had been carried away, the teeth of the upper jaw were also removed, showing only their deep sockets placed at the same respective distances as the teeth themselves, that is to say, three quarters of an inch asunder. The enamel of the teeth was well polished.

At high water, the sea rose 5 or 6 feet above this skeleton, and had tossed up sand and pebbles which had defaced it a good deal, destroying the strata which had originally covered it. It is now in the Museum of the Royal Society. Camper pronounced this fossil to have been a whale; but a whale has no teeth, and this animal had teeth in both jaws. It may probably belong, says M. Cuvier, to the newly discovered fossil animal, Ichthyosaurus.

In December 1824, there was observed in the face of a steep cliff, near Whitby, part of the head of a large animal, standing out from the surface of the alum-shale, several yards above high water-mark. After several days' labour, attended with considerable peril, the whole of the bones were got out of the rock; forming a nearly complete skeleton of a crocodile. Most of the bones of both the hind legs, with fragments of those of the fore legs, were distinctly recognised. At the same time, the appearance of portions of the scaly crust of the animal, arranged in rectangular compartments, as in the crocodile, made it easy to determine the family to which the animal had belonged. It is figured in the Edin. Phil. Journ. vol. XIII. p. 76. The length of the animal seems to have been about 18 feet.

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The form of its head allies it to the gavial crocodile. The teeth are small and very numerous, and arranged in straight lines as in the Ichthyosaurus, but not in the bent or curved form, like those of the living crocodile. The vertebral column and bones of the pelvis resemble in structure those of the Nilotic crocodile.

The crocodiles of Franconia were not known so soon as those of England, but in genus they are not subject to the same uncertainty. The rock containing them, is described as a calcareous stone, or bad marble of a gray colour, replete with ammonites and other ancient shells. The quarries are near the small town of Altorf, now belonging to the kingdom of Bavaria. The strata are referred to the middle oolites. The heads belong to the genus crocodile, but the species is uncertain.

The gangue in which the crocodile bones of the Vicentin are imbedded does not resemble the preceding; though it also belongs to the shell-limestone formation of Jura (lias and oolites). One of the most complete and undoubted fossil crocodiles both as to genus and species, is that of Monheim, discovered by Sommering.

There are few countries more celebrated among naturalists, and collectors of petrifactions, than that which extends along the banks of the Altmuhl, one of the tributaries of the Danube, towards Pappenheim and Aichstedt. Here the numerous quarries of a whitish calcareous schistus which are worked into paving stones for the floors of apartments, perpetually furnish casts of fishes and crustaceous animals, entirely unknown to modern Germany,

and most probably to living nature. Among these are also some very curious reptiles, such as the pterodactyles, or wing-toed animals, which we shall describe afterwards.

These schists have acquired a general celebrity from their employment in lithography, a purpose which they answer better than any other stones. They belong to that prolongation of the chain of the Jura mountains, which after opening a passage to the Rhine at the fall of Schaffhausen, extends into Germany, as far as the banks of the Mein near to Cobourg.

The valley of the Altmuhl has very precipitous sides. On these it is easy to observe through a height of 200 feet, the constituent range of strata. The calcareous schists occupy the summit. They are rich in fishes, in crustacea, reptiles, and even star-fish, but destitute of other shells, except two species of tellines, and some small ammonites. These strata repose on a considerable mass of dolo mite or magnesian limestone, of which M. Von Buch gives a very interesting history in the Journal de Physique for 1822. It is not stratified, and presents hardly any where traces of petrifactions. Of this dolomite, and its covering schists, there are none very near at hand, in the whole chain of the Jura. They begin to appear only between Donawert and Nordlingen. The dolomite itself extends to the north much farther than the schists, and it is in its masses that the famous bone-caverns are hollowed out, of which we shall afterwards treat. Under it are beds of grayish-white limestone, compact, dull, with a scaly fracture, rich in ammonites,

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which furnish enormous building-stones; and last of all there is a brown-gray or gray-limestone, of a fine grain, the basis of all the hills of this canton.

The most celebrated of these slate quarries is that of Solenhoffen, in the very valley of the Altmuhl, a little below Pappenheim. The fossil crocodile which we are now to describe, was found at a little distance from this place. It was discovered at Daiting, two leagues from Monheim, enclosed between two plates of a schistose marly limestone, yellowish-gray, spotted red or yellow with oxide of iron, and mingled here and there with fragments of quartz, delicately veined, of a blackish colour, and crystallized. It was accompanied with a cast of the tail of a small fish, and remains of an insect.

The bones of the crocodile are browner than the stone itself. They still contain, by M. Gehlen's analysis, some animal matter, with a notable proportion of phosphoric acid.

The larger of these stone slabs, 3 feet long, and 15 inches broad, contains the head, the trunk, and the tail of this animal, from end to end, very little deranged, along with a hind foot almost entire, detached from the trunk and incrusted at some distance. Scaly parts are mingled with the bones.

We there see the upper face of the lower jaw armed with 25 or 26 teeth on each side, with its two branches separated at an angle of 30°. Of the upper jaw we see the palatal surface, along with the covering bone and other parts of the skull together, but a little detached, along with the snout. The series of the vertebræ 69 in all, is not deranged except towards the tail. A single glance will con