On .imphibious dnimals.
These, comprising various genera, form a very large and important, as well as a very interesting class of fossils, and The genus Testudo is one of these, but the specimens are rarely, if ever, so well preserved as to enable us to pronounce on their specific distinctions, far less to refer them to any living species. In general their legs or fins are wanting ; and very often they are much mutilated in other ways. Tortoises have at Glaris in Swit zerland, in Malta, at Berlin, at Aix, near Brussels, Maas tricht, Liege, Paris, Verona, and in several parts of England. These are supposed to be all marine species. They have been observed in shales and limestones; and among these last, in our own chalk strata, and in the lower fresh-water formation of the basin of Paris. La Cepede considers that some of the Maestricht specimens belong to the Testudo mydas of Linnxus. Others have been thought to resemble the Testudo lyra. Curler has lately arranged them anew. Our information respecting this genus is, however, far from being satisfactory. But to be more particular. As the specimens are always very im perfect, and as the distinctions of the species depend on the forms of the feet, there are little hopes of ascertaining such species, whether lost or existing, as that part is almost always wanting in the fossil specimens. Indeed the distinc tions are even of less avail, as it is now proved that the land and marine species are not distinguishable by these organs, as Linnxus thought. The bony or scaly parts of the body are those which are almost solely found. and these are scarcely sufficient for the requisite distinctions.
If we were to rely on the investigations of Faujas de St. Fond, we should consider that the six specimens found near Brussels, at Melsbroeck, belonged to the Testudo mydas; and that the four from Aix belonged to an un known species. There are eight specimens from Maes tricht, three of which have been ascertained to belong to new and unkown species; that found at Paris is also of an unknown species. In all these cases the marine or terres
trial nature of the animal may be determined by the general nature of the deposit, or by that of the fossils by which it is accompanied ; but we ought to beware of revers ing the proposition, as M. Curler has done in the case of Glaris, and of deciding on the marine nature of the depo sits from the supposed marine habits of the animal. It is fully known that the Testudo carolina, and the clausa, both of which possess the feet of the river tortoises, wander into the country ; and that the tortoise of Japan, which has the appearance of a sea turtle, is an inhabitant of rivers. It is farther very difficult to decide these points in many cases where fresh-water and marine strata alternate, as in the basin of Paris, or where they are intermixed, as in Sheppey.
The Shcppcy tortoises have sometimes been found tolerably perfect; but they seem also to belong to unknown species. Mr. Parkinson thinks that they are all of one species, and merely differing in size. Those of Verona are imperfect, and seem to have belonged to a species with a coriaceous covering, on account of the present wrinkled state of the surface. One from Gloucestershire has been thought to resemble the Trionyx carinatus, and another the Trionyx xgyptiacus. We must remark, at the same time, that the fragments of this tribe appear to have fre quently been mistaken by different naturalists for parts of other animals ; arising from a want of sufficient acquaint ance with comparative anatomy. Thus Faujas had mista ken a scapula for the horn of a stag, as he had done the bones of thes ternum ; while others have committed similar errors in referring some of the carpal bones to a crocodile.
common toad, as others had supposed. This confirms our opinion, formerly expressed, respecting the true origin of these strata.