•54 



MARINE EEPTILES OE THE OXFOED CLAY. 



of the series this compression ceases and the length increases, so that there is a 

 transition from the cervical to the dorsal type. 



The dorsal ribs are usually greatly crushed, so that, as a rule, their true form 

 cannot be made out ; but in a few specimens this is not the case. Thus, in specimen 

 no. R. 2439 it can be seen that the single articular head bears a very slightly concave 

 articular surface for union with the transverse process ; this facet is oval, the long 

 axis being vertical. External to it the surface is rugose, especially on the face. 

 Beyond these rugosities the bone is compressed and the upper border forms a sharp 



Text-fig. 21. 



Shoulder-girdle of Pelonemtes pliilarclius : A, from above ; B, left scapula from below ; C, left coracoid 



from above. (E. 3318, -^ nat. size.) 



cor., coracoid ; cor.f., facet for coracoid ; dp., dorsal ramus of scapula ; g.c, glenoid cavity ; int.cl., outline 

 of interclavicle ; satp., scapula ; scap.f., facet for scapula ; sym., surface of symphysis ; v.jp., ventral 

 ramus of scapula. 



crest, which terminates externally in a roughened prominence ; beyond this, again, the 

 shaft of the rib becomes oval in section, and probably continued so to its lower end, 

 or in some cases became round. Owing to the presence of a central cavity or of soft 

 tissue, the crushed specimens present the appearance of having been grooved on the 



