422 Dr. C. W. Andrews on some new Plesiosauria 



upwards of thirty-nine vertebrae, the centra of which are 

 shorter than in Murcenosaurus (especially in the anterior 

 region) and longer than in Cryptocleidus. Ends of centra 

 considerably wider than high and almost flat. The single- 

 headed cervical ribs on the anterior part of the neck have a 

 distinct anterior process. Neural spines on anterior part of 

 neck very low, but they increase in height backwards till at 

 the hinder end of the neck they are both wide and high. 

 The shoulder-girdle (fig. 3) is of Elasmosaurian type ; the 



Shoulder-cu'dle of Picrocleidus beloclis, Seeley, sp., from above. (Type 

 specimen R. 1965.) } nat. size, cor., coracoid ; i.cl., interclavicle ; 

 sc, scapula; r.sc, ventral plate of scapula. 



clavicular arch consists of a small interclavicle shaped some- 

 what like an arrow-head ; the clavicles, if present at all, are 

 mere films of bone. The humerus is only slightly expanded 

 distally where it articulates with two bones only, the radius 

 and uhia, which are somewhat elongated. 



The only species at present known is P. heloclis, the 

 shoulder-girdle and the radius and ulna of which were 



