186 



THE EXTINCT BATUACIIIA, REPTILIA 



teeth are well known. As it lias probably been earlier named M. mitchillii by Dekay 

 that name will remain attached to it. 



The Elli/ptonodon compreaeus, Emmons, I do not consider to be a Mosasauroid. The 

 Boaeodon reversw, Leidy, is- founded on pterygoid teeth of some species. They resemble 

 those of M. dekayi. 



MOSASAUIUTS. Conybeare. 



In this genns, the median articulation of the ramus mandibnli permitted of much less 

 motion than in Clidastes, and probably allowed of only a moderate expansion of the in- 

 terramal space;. That it permitted the deglutition of very large bodies is apparent. The 

 accompanying cut exhibits the posterior splenial articular face in two views, of a large; M. 

 dekayi from Gloucester Co., N. J. 



• Fie. 47. 



There are numerous species of this genus, which appear to belong to two groups, the 

 one characterized by the rounded, and the other by the depressed form of the lumbar ver- 

 tebrae. A species of the latter type has been referred to the genus Amphorosteus by 

 Gibbes. They however seem to graduate into each other through such species as M. 

 missuriensis, in such a way as to preclude the idea of the existence of distinction on that 

 ground. The teeth, as has been shown by Leidy, present a considerable range; of varia- 

 tion, which, lie remarks, if too great to be embraced by a single species, indicate a greater 

 number of species than has been supposed. 



Having access to a considerable; amount of material, contained in the cabinets of the 

 Academy Natural Sciences, the State ( Penological Surv(;y at New Brunswick, of the Mount 

 Holly (Burlington Co.) Lyceum, and e>f myself, I can re;ly with confidence on the exist- 

 ence of seven species of the restricted genus. These are;, M. maximus, Cope, M. dekayi, 

 Bremu, M. fulciatus, Cope, M. missuriensis, Harlan, M. oarthrus, Cope, M. depressus, 

 Cope, M. brumbyi, Gibbes. As a species probably distinct, but not we'll established, I 

 include M. minor, Gibbes. 



Cranium. The species named, as well defined, have; been compared in their quadrate 

 hones, atlases, and lumbar vertebrae, where the most marked peculiarities have been dis- 



