8 FOSSIL REPTILIA OF THE 



apophysial pits, (fig. 1) ; its vertical extent here is not quite equal to that of the 

 pleurapophysial pit. This is of an oblong oval shape, less deeply concave than the 

 neurapophysial pit, with a smooth surface, nearer the posterior than the anterior 

 surface of the vertebra, with the border slightly prominent (fig. 4, pi). The 

 venous foramina at the lower surface (fig. 4) are situated in depressions, divided 

 by a ridge-like narrow tract of the centrum. In this character, but more espe- 

 cially in the depth of the terminal articular surfaces, with their broad and thick 

 convex border, and in the position of the riblet, the present centrum is referable 

 to the Plesiosaurus Bernardi. 



The following are dimensions of this cervical centrum : 



PL Bernardi. 

 In. lines. 

 Antero-posterior diameter or length ..... 1 2 



Transverse diameter or breadth ..... 1 4 



Vertical diameter or height . . . . . 14 



The centrum, Tab. IV, figs. 5 and 6, appears to have succeeded the foregoing 

 in the same cervical series, with, perhaps, the intervention of one or two vertebrae. 

 It is similar in colour and mineral character, and from the same locality. It 

 repeats the distinctive characters of Plesiosaurus Bernardi. It indicates by a 

 slight obliquity the effects of posthumous pressure. 



This mechanical force has distorted in a greater degree a centrum (Tab. IV, 

 figs. 7 and 8), doubtless from a more posterior part of the same neck. The 

 margins of the pleurapophysial pits are here rather more produced. The middle 

 of the deep concavity of the terminal surfaces is impressed by a transverse pit or 

 linear mark (fig. 8). 



Col. Kiprianoff, of the Imperial Russian Engineer Corps, submitted to me 

 some plesiosaurian vertebrae from the Neocomian deposits, or Green-sand, of 

 Kursk, in the district of Kursk, near Moscow, which offered all the characters of 

 the Plesiosaurus Bernardi. A cervical vertebra, intermediate in size between figs. 6 

 and 7, shows a partial anchylosis to the centrum of both neur- and pleur- apophyses. 

 The riblet was confluent to a surface near the lower part of the centrum, about 

 the same distance from the neurapophysis as in the first-described vertebra (fig. ] ) 

 from the Cambridge Green-sand. The under surface was ridged or pinched up, 

 as it were, between the venous foramina, each of which was also situated in a 

 depression between the median ridge and the base of the riblet. This element 

 expanded, and its posterior angle was produced backward. The following were 

 the dimensions of the centrum of this vertebra : 



