100 



MAEINE EEPTILES OF THE OXEOED CLAY. 



zygapophyses (a.z.) are almost parallel with one another and separated anteriorly by a 

 deep notch : their articular siu'face is concave from side to side. As already mentioned, 

 in the two or three vertebrae (pectorals) behind the cervical series the rib-articulation 

 is borne partly on the centrum and partly on the arch ; in the dorsal region it passes 

 entirely on to the arch and is situated at the end of a more or less elongated transverse 

 process (t.j).)- In the anterior dorsal region these processes are comparatively short 

 and stout (PI. IV. fig. 5 ; text-fig. 53) ; they arise from the bases of the arches and are 



Text-fig. 55. 



Posterior dorsal vertebra of Murcenosaurus durobrivensis, from left side. (E. 2863, | nat. size.) 

 a.z., anterior zygapopliysis ; n.s., neural spine ; r.f., facet for rib ; s., neuro-central suture ; 



t.j)., transverse process. 



somewhat curved, the concavity being downwards ; towards their extremities they 

 enlarge and bear large convex facets (r.f.), for union with the single-headed ribs. 

 Further back the processes arise higher and higher up the arch, and at the same time 

 they become more slender at the base and curve a little backwards, so that the rib- 



