The group of the Crocodiles and Alligators (_Crocadilia_), distinguished by the fact that the teeth are implanted in distinct sockets and the skin more or less extensively provided with bony plates, is represented in the Triassic rocks by the _Stagonolepis_ of the Elgin Sandstones. The so-called "Thecodont" reptiles (such as _Belodon, Thecodontosaurus_, and _Paloeosaurus_, fig. 152, c, d, e) are also nearly related to the Crocodiles, though it is doubtful if they should be absolutely referred to this group. In these reptiles, the teeth are implanted in distinct sockets in the jaws, their crowns being more or less compressed and pointed, "with trenchant and finely serrate margins" (Owen). The bodies of the vertebræ are hollowed out at both ends, but the limbs appear to be adapted for progression on the land. The genus _Belodon_ (fig. 152, c) is known to occur in the Keuper of Germany and in America; and _Paloeosaurus_ (fig. 153. e) has also been found in the Trias of the same region. Teeth of the latter, however, are found, along with remains of _Thecodontosaurus_ (fig. 153, d), in a singular magnesian conglomerate near Bristol, which was originally believed to be of Permian age, but which appears to be undoubtedly Triassic. [Illustration: Fig. 152.--Triassic Reptiles. a, Skull of _Nothosaurus mirabilis_, reduced in size--Muschelkalk, Germany; b, Tooth of _Simosaurus Gaillardoti_, of the natural size--Muschelkalk, Germany; c, Tooth of _Beladon Carolinensis_--Trias, America; d, Tooth of _Thecodontosaurus antiquus_, slightly enlarged--Britain; e, Tooth of _Paloeosaurus platyodon_, of the natural size--Britain.]