THECODONTIA 249 



are conical, rather slender, compressed and acutely pointed, 

 with an anterior and posterior finely-serrated edge, the serra- 

 tures being directed towards the apex of the tooth ; the outer 

 surface is more convex than the inner one; the apex is slightly 

 recurved ; the base of the crown contracts a little to form the 

 fang, which is subcylindrieal. 



Genus Pal^eosaurus, Eiley and Stutchbury. In the same 

 formation as contained the jaw and teeth of the Thccodontosau- 

 rus two other teeth were separately discovered, differing from 

 the preceding and from each other ; the crown of one of these 

 teeth measuring nine lines in length and five lines in breadth. 

 It is compressed, pointed with opposite trenchant and serrated 

 margins, but its breadth as compared with its length is so 

 much greater than in the Thccodontosaurus, that upon it has 

 been founded the genus Palcwsaurus, and it is distinguished 

 by the specific name of 'platyodon, from the second tooth, which 

 is referred to the same genus under the name of Palccosaurus 

 cylindrodon. The portion of the tooth of the Palccosaurus 

 cylindrodon which has been preserved, shows that the crown is 

 subcompressed and traversed by two opposite finely-serrated 

 ridges, as in the Thccodontosaurus ; its length is five lines, its 

 breadth at the base two lines. 



The vertebra? associated with the two kinds of teeth above 

 described are sub-biconcave, with the middle of the body more 

 constricted, and terminal articular cavities rather deeper than 

 in Telcosaurus ; but they are chiefly remarkable for the depth 

 of the spinal canal at the middle of each vertebra, where it sinks 

 into the substance of the centrum ; thus the canal is wider, 

 vertically, at the middle than at the two ends of the vertebra : 

 an analogous structure, but less marked, obtains in the dorsal 

 vertebra? of the Rhynchosaurus from the new red sandstone of 

 Shropshire. 



Besides deviating from existing lizards in the thecodont 

 dentition ami biconcave vertebra, the Saurians of the dolomitii 



