260 SATTROPTEKYGIA. 



these dimensions agreeing very closely with those of the 

 femur of the type. There is, however, the normal 

 number of phalangeals in the fifth digit, indicating that 

 the distal ones have been lost in the type. 



Purchased, 1868, 



R. 227. An anterior cervical vertebra probably belonging to this 

 species; from Lyme-Regis. In the relatively long cen- 

 trum this specimen agrees with P. dolichodirus, but the 

 outer surface is smooth. 



Presented by Br. H. Woodward, 1882. 



39851. Three associated imperfect dorsal vertebrae which may, 

 perhaps, belong to this species ; from Lyme-Eegis. The 

 centra are relatively longer than in the dorsals resembling 

 those of P. TiawTcinsi mentioned on p. 265 ; their dimensions 

 being :— length 0,032 (1-25 inches), height 0,035 (1-48 

 inches), width 0*042 (1*65 inches) ; and the external sur- 

 face is quite smooth. In a detached dorsal in the skeleton 

 No. 2022* of P. hawJcinsi, while the dimensions of the 

 terminal faces of the centrum are almost identical with 

 those of the present specimen, the length is only 0,024 

 (0-95 inch). Purchased, 1865. 



Plesiosaurus hawkinsi, Owen l . 



Syn. Plesiosaurus triotarsostinus, Hawkins 2 . 

 Including Plesiosaurus etheridgei, Huxley 3 . 



Nearly of the size of P. dolichodirus, but with a much shorter 

 neck, the length of the skull being contained about 3| times in the 

 interval between the atlas and the pectoral girdle. Cervical 

 vertebrae 30 or 31 in number, of the general contour of those of the 

 type species, but externally smooth, with relatively shorter centra 

 and neural spines, and in immature individuals with the upper costal 

 facet approximated to the neuro-central suture. Dorsals with shorter 

 and more distinctly cupped centra, and a lower and more rounded 

 neural canal, the height of the arch and spine being less than twice 

 the height of the centrum. In the pectoral girdle the anterior pro- 

 jection of the coracoid relatively long and extending far over the 

 omosternum ; and the omosternal extremity of the ventral plate of 

 the scapula wider than the glenoidal. Limb-bones smooth ; ulna 



1 Bep. Brit. Assoc, for 1839, p. 57 (1840). 



2 Memoirs on Ichthyosauri and Plesiosauri, pi, xxiv. (1834). 



3 Quart. Journ. Geol. Soc. vol. xiv. p. 281 (1858). 



