The crocodiles continue to make their appearance in these schists, and always of the long-muzzled or rostrated kind. M. de Sœmmering has described one (the _Crocodilus priscus_), the entire skeleton of a small individual of which was found nearly in as good a state of preservation, as it could have been in our cabinets.[256] It is one of those which most resemble the present gavial of the Ganges; the anterior or united part of its lower jaw, however, is less elongated; its lower teeth are alternately and regularly longer and shorter. It has ten vertebræ in the tail. But the most remarkable animals which these limestone slates contain, are the flying lizards, which I have named _Pterodactyli_. They are reptiles whose principal characters are, a very short tail, a very long neck, the muzzle much elongated, and armed with sharp teeth; the legs also long, and one of the toes of the anterior extremity excessively elongated, having probably served for the attachment of a membrane adapted for supporting them in the air, accompanied with four other toes of ordinary size, terminated by hooked claws. One of these strange animals, whose appearance would be frightful did they occur alive at the present day, may have been of the size of a thrush[257], the other of that of a common bat[258]; but it would appear from some fragments that larger species had existed[259]. A little above the limestone slates is found the nearly homogeneous limestone of the Jura ridges. It also contains bones, but always of reptiles, crocodiles, and fresh-water tortoises, of which a vast quantity is found in particular in the neighbourhood of Soleure. They have been very carefully searched for by M. Hugi; and, from the fragments which he has already collected, it is easy to recognise a considerable number of Fresh-water Tortoises, or Emydes, which further discoveries can alone determine, but of which several are already distinguished by their size and peculiar forms, from all the species hitherto known[260]. It is among these innumerable oviparous quadrupeds, of all sizes and forms; in the midst of these crocodiles, tortoises, flying reptiles, huge megalosauri, and monstrous plesiosauri, that some small Mammifera are said to make their appearance for the first time; and the assertion is so far authenticated by the occurrence of jaws, and some other bones discovered in England, which undoubtedly belong to this class of animals, and particularly to the family of Didelphides, or to that of the Insectivora. It may, however, be supposed, that the stoney matters which encrust these bones, owe their origin to some local recomposition, posterior to the original formation of the strata. However this may be, it is still found for a long time that the class of Reptiles predominates.