78 REPORT— 1S39. 



Flesiosaurus trigonus, Cuv. (?) 



This species was founded by Cuvier on a vertebra from the 

 coast of Calvador, which presented a triangular form, like some 

 of those of the Mosasaurus, i. e., it was flat and broad below, 

 and graduall}'^ decreasing above ; on the sides of the lower sur- 

 face were transverse processes. As the form of the articular 

 surfaces are not described, it may be questioned whether the 

 vertebra above alluded to really belongs to the Plesiosaurian 

 type : and in the present instance these surfaces deviate some- 

 what from the characteristic form. 



They are flat on the outer or peripheral third, and the re- 

 maining central part, instead of being convex, as in the Plesio- 

 sauri generally, are slightly concave. It is this character, in 

 addition to their smaller size, which pi'incipally distinguishes 

 the present from the last-described vertebra, with which it other- 

 wise closely agrees in its leading characters, viz. those afforded 

 by the development and position of the transverse processes. 

 These transverse processes are short and thick ; the breadth or 

 antero-posterior diameter of their base equals one half of that of 

 the entire centrum ; they are directed obliquely downwards. 



The contour of the articular surface of the body of the verte- 

 brae is nearly circular : the triangular figure is due to the posi- 

 tion and direction of the transverse processes ; the distance be- 

 tween these and the neurapophyses equals twice their vertical 

 diameter : and although this character will be lost in the more 

 posterior cervical vertebrae, it is to be remembered that it is one 

 which has never presented itself in those Plesiosauri of which 

 the entire series of cervical vertebrae have been examined. 



Inches. 

 The antero-posterior extent of the vertebra described is If 

 Transverse diameter, including the transverse processes 2\ 

 Vertical diameter of the body 2 



This vertebra is from the lias of the bone-bed of the Aust 

 Cliff, near Bristol. 



Plesiosaurus hrachyspondyluSy O. 



— recentior ( ? ), Conybeare*. 



giganteus ( ? ) Ibid.f 



transverse processes, which are as remote from the neurapophyses as in the 

 PL subtrigoiDis ; bnt the form of the articular surface of the vertebral centre is 

 more regularly rounded. This vertebra, which seems to indicate a new species 

 or subgenus of Enaliosaurs, is from the lias at Bridport, Dorsetshire. It is re- 

 commended that the Saurian fossils of this locality be carefully searched for and 

 preserved. 



* I-Ierm. Von Meyer, PalcBologka, p. 112. f Geol. Trans., 1824, p. 389. 



