50 



MARINE REPTILES OF THE OXEORD CLAT. 



than the height, and, owing to a slight forward projection of the antero-ventral region, 

 the length on the mid-ventral is rather greater than that on the mid-dorsal line. The 

 facets for union with the pedicles of the neural arch do not extend quite to the posterior 

 end of the centrum, as they do in the vertebras further back in the neck ; the neural 

 surface is wider behind than in front. The rib-facets (r.f.) are borne on a very short 

 prominence, the upper end of which is deeply concave and obscurely divided by a 

 groove into a smaller upper portion for the tubercle of the rib, and a larger lower 

 portion for the head ; the division between these surfaces is often indistinct, 

 especially in the posterior cervicals ; the rib-facets are a little nearer to the posterior 

 than to the anterior edge of the centrum, and the ventral face between them is concave 



Text-fig. 17. 



Anterior cervical vertebrae of Peloneustes pTiilarcTius, from left side. (R. 3318, j nat. size.) 

 a.z., anterior zygapophysis ; n.s., neural spine ; r., ribs. 



on either side of a low rounded hypapophysial ridge, which is more prominent at its 

 anterior than at its posterior end ; the nutritive foramina open into the concavities on 

 each side of the ridge, but in the anterior cervicals they are sometimes obscure and 

 perhaps altogether absent. 



Speaking generally, the neural arch iu the cervical series (text-figs. 17-19) is high, 

 and the neural spine (n.s.) narrow. The neural arch of the axis described above is 

 missing, but in another specimen (text-fig. 15, E. 2438) it is well preserved. The 

 pedicle is broad, and it unites with the whole length of the centrum ; above, the arch 



