THE PLESIOSAUBIA. 209 



proportion, as that of a Swan ; but in others, the head is 

 large and massive, and the neck much shorter. The hind 

 limbs are longer than the fore limbs, and there is a compa- 

 ratively short tail. The integument was certainly devoid 

 of any scutes ; and was, probably, smooth and possessed no 

 scales. 



The cervical vertebrae may exceed forty in number, though 

 they are generally fewer ; and as none of the ribs appear to 

 have been connected with the sternum, or if such connec- 

 tion existed it cannot now be traced, it becomes difficult to 

 distinguish between cervical and dorsal vertebrae, and one is 

 obliged to have recourse to some method of separating the 

 two, difi'ering from that already adopted. Now, in these 

 animals, the neurocentral suture persists for a consider- 

 able period, if not throughout life ; and the surfaces for 

 the articulation of the cei-vical ribs, which are at first alto- 

 gether below the neurocentral sutures, gradually rise, in 

 the posterior parts of the neck, until they first are cut by, 

 and then rise above, the suture. It is very convenient, and 

 harmonizes very well with some facts to be mentioned by- 

 and-by in the structure of the Crocodilia, to take the last 

 of the vei-tebrse in which the costal articular surface is 

 cut by the neurocentral suture, as the last of the cervical 

 series. 



The two anterior cei-vical vertebrae, as thus defined, con- 

 stitute the atlas and axis, and are frequently ankylosed 

 together. The centra of the other cervical vertebrse have 

 slightly concave anterior and posterior surfaces; well-de- 

 veloped neural arches ; anterior and posterior oblique pro- 

 cesses, or zygapophyses, of the ordinary character; and stout, 

 but somewhat short, spinous processes. The centi-um pre- 

 sents, upon each side, an oval rugose pit, sometimes more 

 or less divided into two facets. This is the costal articular 

 surface, which has been already adverted to. Into it fits 

 the thickened head of a costal rib, which may have corre - 

 sponding facets, but is otherwise imdi-^ided. The rib is 

 contimied backwards into a short and straight body, and 

 the angle, oi the part at which the neck and the body of 



P 



