PLESIOSATJRIDJE. 261 



and fibula relatively shorter and wider than in the type species ; 6 

 bones in carpus (fig. 79) and tarsus. The author follows Owen and 

 Huxley in regarding Xo. 2022* as the adult of the present species. 

 That skeleton differs from the type in that the skull is shorter in 

 proportion to the limb-bones and vertebral column, in the relatively 

 larger carpals and tarsals, and the longer interval between the costal 

 facets and the neuro-central suture of the cervical vertebrae. In 

 regard to the first point it is well known that in Crocodiles the 



Far. 79. 



no 





Plesiosaurus haw Tcinsi— Ventral aspect of the right pectoral limb ; from the 

 Lower Lias of Street. }. r, radius ; u, ulna ; r' t radialc ; i, inter- 

 medium ; u', ulnare. 



length of the skull becomes relatively less in the adult 1 ; the 

 second point is evidently due to immaturity ; while the value of 

 the third difference may be inferred from the case of P. macro- 

 cephalus (p. 206). The specific name triotarsostinus, although the 



1 Theobald, 'Catalogue of Keptilia of India,' p. 36, states that the length of 

 the skull and body in two individuals of OrocodUtU pakwiris are as follows: 

 —length of head 26 inches, length of body [fi foot; and^ength of head 24(> 

 inches, and of body 12 feet. In the former instance the proportion irf the bead 

 to the body being \, and in the latter J. Tins Lndicatea the slight value which 

 can be attached to the so-called " cephalic index " of Sollas (Quart. Journ. Geol, 

 Soc. vol. xxxvii. p. 408) as a means oi* distinguishing the species of Plesio- 

 sauridcB. 



