52 PKOCEEDINGS OF THE GEOLOGICAL SOCIETY. 



and laterad extension of the scapula corresponding to the blade of 

 the scapula of other vertebrates, which he considers to be absent in 

 Plesiosaurus. 



Kecapitulated in the order in which they were enunciated, the 

 generic characters of Pliosaurus are those furnished, 1, by the pro- 

 podials (femora or humeri) ; 2, by the cervical vertebras ; 3, by the 

 teeth ; 4, by the cnemial or antibrachial (epipodial, 0. C. Marsh) seg- 

 ment of the limbs ; and, 5, by the " sterno-coraco-scapular frame." 



In estimating the generic value of these several characters, it 

 should be borne in mind that no evidence is adduced that any of 

 the remains on which they were based were found so associated as 

 to warrant the belief that they formed parts of the same skeleton ; 

 indeed circumstances show that such was not the case. This is 

 certainly true of the two type femora of Pliosaurus grandis and P. 

 trochanter ius, of the paddle of P. jportlandicus, of the sterno-coraco- 

 scapular frame, and, I think, also of the vertebras and teeth. It 

 should also be mentioned that the two fine skulls presented to the 

 British Museum by J. C. Mansel-Pleydell, Esq., and referred by Prof. 

 Owen to Pliosaurus grandis and P. trochanterius, are dissociated 

 fossils. 



It is evident that a series of generic characters drawn from such 

 dissociated remains can have only a hypothetical value. 



Fig. 7. — Hind limb of Plesiosaurus Manseli. 



T, the tibia; i, the intermedium ; F, the fibula. 



