166 SATJROPTEKYGIA. 



R. 1324. The crown of a tooth, of similar type ; from the Lower 

 Lias. The convex surface is less smooth than in the pre- 

 ceding specimen. No history. 



40094. The crown of a similar tooth in matrix ; from the Lower 

 Lias of Lyme-Regis, Dorsetshire. Purchased, 1865. 



2124*. The crown of a rather smaller tooth in matrix ; from Lyme- 

 Regis. Hawkins Collection. Purchased, 1834. 



R. 1325. Fragment of rock showing the concave surface of the 

 crown of a tooth ; from the Lower Lias. No history. 



R. 1326. The somewhat crushed crown of a similar tooth; from the 

 Lower Lias. The convex surface is nearly smooth. 



No history. 



R. 1327. The crown of a tooth of similar type in matrix ; from the 

 Lower Lias. No history. 



Thaumatosaurus megacephalus (Stutchbury x ). 

 Syn. Plesiosaurus megacephalus, Stutchbury 2 . 



Considerably smaller than T. cramptoni, the length of the type 

 skeleton being 16 feet and that of the skull 30 inches. Cervico- 

 dorsal vertebrae 58 in number, of which some 27 3 are probably 

 cervical ; total number of vertebrae 92. Apparently closely allied to 

 T. arcuatus, but with a relatively larger skull and proportionately 

 smaller pectoral limbs ; and the radius and ulna scarcely exceeding 

 the tibia and fibula in size, and apparently a shorter coracoid. 

 Three bones in each row of the carpus and tarsus. 



It appears difficult to believe that the above-mentioned differences 

 from T. arcuatus can be due to sex. 



Hob. Europe (England). 



R. 1309. Cast of the ventral aspect of the skull and of the right 

 pectoral limb. The original belongs to the type skeleton, 

 which was obtained from the Lower Lias of Somersetshire 

 and is preserved in the Bristol Museum. The entire 

 skeleton is figured by Stutchbury in the ' Quart. Journ. 

 Geol. Soc' vol. ii, pi. xviii. ; the skull being also figured 

 by Sollas in vol. xxxvii. pp. 472-478, figs. 8-14. The 

 resemblance of the mandible to that of T. arcuatus is 

 mentioned under that heading, where the difference in the 



1 Quart. Journ. Geol. Soc. vol. ii. p. 412 (1846).— Plesiosaurus. 2 Log. cit. 



2 Sollas, ' Quart. Journ. Geol. Soc' vol. xxxvii. p. 469, gives the number of 

 cervicals as o0, but this is probably too high. 



