ON BRITISH FOSSIL. REPTILES. 155 



the axis, giving them somewhat a twisted form, or the shape of a long/an- 

 tero-posteriorly. The trochanter is well preserved, wedge-sliaped, and of 

 considerable size, as may be seen by reference to the figures. The articular 

 head is flattened at the space between the trochanter, and the articular ex- 

 tremity is more curved than any other part of the bone : the centre is nearly 

 round, but a slight elevation or ridge exists on its posterior surface, in the 

 situation of the linea aspera of the human femur. The condyles are flat- 

 tened, the outer one being the larger ; there is a deep depression between 

 them posteriorly, and a very slight one anteriorly. 



" On an attentive comparison of these femurs with those of the Crocodile 

 and Megalosaurus, we again recognise a resemblauce. A comparison with 

 the femurs of the Monitors evidently shows that our animal cannot have be- 

 longed to that family. The femurs of the Monitor are much less curved, 

 being nearly straight, and the trochanter is much nearer the articular ex- 

 tremity ; characters sufficiently showing a wide diff"erence between them." 



The tibia, fibula, and metatarsal bones manifest, like the femur, the fitness 

 of the thecodont Saurians for progression on land. The ungual phalanges 

 are sub-compressed ; curved downwards, pointed, and impressed on each 

 side with the usual curved canal. 



The general conclusions which may be drawn from the knowledge at pi^e- 

 sent possessed of the osteology of the Thecodontosauriis and PalcEosaurus, 

 the antiquity of which the discoverers of these genera regard as being greater 

 than that of any other vertebrated animals, excepting fishes, are, that in their 

 thecodont type of dentition, biconcave vertebrae, double-jointed ribs, and pro- 

 portionate size of the bones of the extremities, they are nearly allied to the 

 Teleosaurus ; but that they combine a Lacertian form of tooth, and structure 

 of the pectoral and probably pelvic arch with these Crocodilian cliaracters, 

 having distinctive modifications, as the moniliform spinal canal, in which, 

 however, the almost contemporary Rhynchosaur participates. It would be 

 interesting to ascertain whether the caudal vertebrae are characterized, as in 

 the Thuringian Protorosaur, by double diverging spinous processes*. 



Cludyodon, nob. — In the new red sandstone (Keuper?) of Warwick and 

 Leamington, there occur detached, pointed, trenchant, recurved teeth, the 

 crowns of which are sometimes 1 inch 4 lines in length, and 5 lines across the 

 base : they have been found in the same quarries as those containing the re- 

 mains of the LabyrinthodoH. In their compressed form, anterior and posterior 

 serrated edges, sharp points, and microscopic structure, these teeth agree with 

 those of the Saurian reptiles of the Bristol conglomerate. In their breadth, as 

 compared with their length and thickness, they are intermediate between the 

 Thecodontosauriis and the Palccosaiiriis platyodon ; but they are larger, with 

 longer and more recurved crowns, and thus more nearly approach the form 

 characteristic of the teeth of the Megalosaurus\. From these teeth, however, 

 they differ in their greater degree of compression, and in a slight contraction 

 at the base of the crown ; I therefore indicate the genus, of which, as yet, only 

 the teeth are known, by the name of Cladyodon, and the species from the 

 Warwickshire sandstones by the name of Cladyodon Lloydii, in testimony 

 of the friendly aid of Dr. Lloyd of Leamington, to whose zealous co-opera- 

 tion I owe the materials for the description of the teeth of the present genus, 

 and the still more remarkable ones of the British species of Labyrinthodon, 

 with which tiie teeth of the Cludyodon are associated. 



* This structure I have ascertained in the original specimen described by Spener, now 

 preserved in the Iliiiiterian Museum. 



t One of the teeth of the Cladyodon is figured in the Memoir of Messrs. Murchison and 

 Strickland on the Warwick Sandstones, Geol. Trans., second series, vol. v. pi. xxviii. fig. 6. 



