308 THE OXFORD OOLITE PERIOD. CHAP. 



which manifests specific characters in such parts as have been 

 collected. It may be regarded as the analogue of Plesiosaurus 

 brachyspondylus, to be noticed hereafter as a fossil of Kimmeridge 

 clay. Of the head almost nothing intelligible ; indeed of the 

 whole of the anterior part of the body very little, except vertebrse 

 and a few ribs. The vertebral column is nearly complete, and of 

 the posterior part, and especially of the pelvic girdle and paddle 

 bones, the examples are in plenty. 



Of cervical vertebrae, one series of six has come to us from the 

 clay-pits of Long-Marston. These are from a very forward part 

 of the neck near the head, and shew in a striking manner the rapid 

 augmentation in size of the anterior cervicals which is observed in 

 several species of the genus found near Oxford. They are biconcave, 

 with a narrow somewhat tumid interforaminal space. 



Diagram CXlII. Six Cervical Vertebrae of Plesiosaurus Oxoniensis. 

 Scale, one-fifth of nature. 



The largest of these vertebrae measures on the articular face 

 in height, 1*3 inch; in breadth, i 6; and the length is i'i : the 

 smallest in height, 0*9 ; in breadth, 1*2; and is 0*85. long. 



Vertebrae of the dorsal series occur rather frequently, and, except 

 for fractures which would not occur if the workmen were at all 

 careful, they might be generally preserved quite perfect. 



These vertebrae are somewhat remarkable for the almost circular 

 outline of the articular faces, only broken at the upper margin by 

 the neural canal, for the sharply-defined border of these faces, 

 and a general smoothness and neatness of surface. The zygapo- 

 physes are very clearly marked; the anterior pair deeply spoon- 

 shaped; the posterior pair formed of plates inclined toward each 

 other 45, and rounded beneath to fit into the anterior grooves. 

 The articulating faces are equally concave, the depth being about 



