98 



MAKINE EEPTILES OF THE OXEOED CLAY. 



The pedicle of the neural arch rises from a long hase which extends the whole 

 length of the centrum, and posteriorly may even form a small portion of the edge of 

 the articular surface for the succeeding vertebra. Above the neuro-central suture the 

 anterior and posterior borders are notched to allow of the passage of the spinal nerves ; 

 the posterior notching is the deeper. The transverse process (t.p.), which in this 

 region bears the articular surfaces for both the head and tubercle of the rib, is borne 

 entirely on the neural arch, and is lower down in the anterior dorsals than it is further 

 back. In the first dorsal, although the two articular processes for the rib are borne 



Text-fig. 37. 



a.z. 



Dorsal vertebra of Steneosaurus durobrivensis : A, middle dorsal from the front ; C, the same from 



the left side ; B, anterior dorsal from left side. (E. 3701, g nat. size.) 



a.z., anterior zygapophysis ; dp., diapophysial process ; n.sp., neural spine ; pp., parapophysial process ; 



p.z., posterior zygapophysis. 



on 



a common base, they are still distinctly separated from one another by a deep groove ; 

 the parapophysis (pp.) is situated in front of and below the diapophysis (dp.), which 

 is much the longer of the two and is directed a little upwards and backwards. At the 

 same time it is slightly curved, the convexity being dorsal ; the rib-facets of both the 

 para- and diapophyses are flat or somewhat convex. As it is followed back in the 



