REPTILIA. 325 



Sp. Mosasaurus Hoffmannl Conybeare. Discovered about the year 1766 iu 

 the chalk quarries at Mont St Pierre, near Maestricht. See Cuvier Rech. 

 s. I. ossemevts fuss. v. 2, pp. 310 — 338. Approaching the Monitors in the 

 form of Cranium. 



Leiodon Owen. Acrodont type of dentition. Teeth half the 

 size of tliose of Mosasaurus Hoffmanni. Outer surface nearly as 

 convex as inner, with section of crown elliptic. 



Sp. Leiodon anceps Owen. Teeth alone known. Owen Rep. Br. Assoc. 

 184T, pp. 144 — 145. Chalk of Norfolk. 



Geosaurus Cuv. Teeth with crown compressed, subrecurved, 

 anterior and posterior edges trenchant, finely serrate. Eyes with 

 broad sclerotic plates. Vertebrae biconcave. Lithographic lime- 

 stone, green sand. Cuv. Oss. foss. v. 2, pp. 338 — 343. 



Crocodilia Owen. 



Crocodilian remains have been found fi'om the Lias and Oolite to 

 the Eocene tertiary, and present difiei-ences of structure from the 

 existing sjjecies which are greater in proportion as the strata in 

 which they are found are more i-emote. In the existing species 

 the anterior sui-face of the vertebral centrum is concave, the poste- 

 rior convex, {^procoelian Owen). But in the crocodiles of the ter- 

 tiary system there are two other different types; in one the position 

 of the ball and socket is reversed, {pjnsthoccelian Owen), in the 

 other and more common both articular surfaces are flat or slightly 

 concave, {amphicoelian Owen). 



Steneosaurus Geoff. St.-Hilaire. Nostril siibterminal ; jaws nar- 

 row with slender, conical, sharp-pointed and equal teeth, like those 

 of existing Gavials. Vertebrae biconcave. 



Teleosam'us Kcenig. Nostrils terminal; teeth as in preceding 

 but thinner in proportion to their length. Vertebrae biconcave. 

 Both of these are from the Oolite series of secondary rocks. 



Streptospondylus Owen. Vertebrae with ball and socket articula- 

 tion reversed, convexo-concave. From the Oolite of Caen, the 

 Wealden. 



Suchosaurus Owen. Teeth arched, compressed, with two cut- 

 ting edges, not serrate ; the crown with longitudinal ridges termi- 

 nating before the extremity of the tooth. 



