ON BRITISH FOSSIL REPTILES. 189 



they consist of foui* vertebrtE, portions of ribs, a humerus, a femur, two tibiae, 

 one end of a large flat bone, and several small osseous, dermal scutes. The 

 mass was discovered in the new red sandstone at Leamington, and was trans- 

 mitted to me by Dr. Lloyd in the summer of 1 840. 



The vertebras present biconcave articular surfaces similar to those of the 

 other species. In two of them, the surfaces slope in a parallel direction ob- 

 li((uely from tlie axis of the vertebrse, as in the dorsal vertebrije of the frog, 

 indicating an habitual inflexion of the spine, analogous to that in the humped 

 back oi' the frog. The neurapophyses are anchylosed to the vertebral body. 

 Tlie spinous process rises from the whole length of the middle line of the 

 neurapophysial arch, and its chief peculiarity is the expansion of its elongated 

 summit into a horizontally flattened plate, sculptured irregularly on the upper 

 surface. A similar flattening of the summit of the elongated spine is exhi- 

 bited in the large atlas of the toad. The body of the vertebra? agrees with 

 tliat of the L. leptognathus. The humerus is an inch long, regularly convex 

 at the proximal extremity, and expanded at both extremities, l)ut contracted 

 in the middle. A portion of a somewhat shorter and flatter bone is bent at 

 a subacute angle with the distal extremity, and resembles most nearly the 

 anchylosed radius and ulna of the Batrachia. 



The femur wants both the extremities ; its shaft is subtrihedral and slightly 

 bent, and its walls are thin and compact, including a large medullary cavity. 

 The tibias are as long, but thicker and stronger than the femur. They had 

 lost their articular extremities, but exhibited that remarkable compression of 

 their distal portion which characterizes the corresponding bone in the Ba- 

 trachia : they likewise have the longitudinal impression along the middle of 

 the flattened surface. The length of the more perfect shaft is 2 inches 1 line. 



With respect to the osseous dermal scuta, tliough they form a striking in- 

 stance of tlie Crocodilian affinities of the Leamington fossil, yet as these de- 

 tached superficial bones are the most liable to be separated from the frag- 

 mentary skeleton of the individual they once clothed, the negative fact of 

 their not having been found associated with the remains of the Labyrintho- 

 don in other localities, proves nothing in regard to a difference of dermal 

 structure between the Leamington and Warwick species. Indeed no anato- 

 mist can contemplate the extensive development and bold sculpturing of the 

 dermal surface of cranial bones in the Lahyrinthodon pachygnathus and L. 

 leptognathus without a suspicion, that the same character may have been mani- 

 fested in bony plates of the skin in other parts of the body. Admitting for 

 a moment this structure to be proved, to what extent, it will be asked, does 

 it aflect the claims of the LahyrintJiodonto be admitted into the order of Ba- 

 trachians, in which every known species is covered with a soft, lubricous and 

 naked integument, without scales or scuta ? In reply, I have observed*, that 

 the skin is the seat of variable characters in all animals ; and, if considered 

 apart from the modifications of the osseous and dental systems, is apt to mis- 

 lead the naturalist who is in (|uest of the real affinities of a species : thus we 

 have in the Trionyx an example of a soft-skinned animal among Chelonian 

 reptiles. 



The following are the names of the species of extinct Reptiles in the order 

 in which they are described in the second and concluding part of the Re- 

 port : — 



Order Enaliosauria. 



Pliosuurus hrachydeirus, Owen. 

 Pliosaurus trochanterius, Owen. 



* Geological Proceedings, January 1841. 



