172 



MAEINE EEPTILES OP THE OXFOED CLAY, 



pedicles are continuous with those for the cer\'ical ribs. The neural spines are short 

 and thickened ; their summits were evidently cartilaginous. There are two pectoral 

 vertebrae, in which the articulation for the rib passes from the centrum to the arch ; 

 their centra assume a more circular outline, passing into the form of the dorsal centra 

 (text-figs. 81, 82), the vertical diameter of which is approximately equal to the transverse. 

 At the same time the articular ends are less concave and the rounded rim disappears ; 

 the nutritive foramina pass on to the sides of the centra. There are 22 dorsals, 

 the neural arches of which bear transverse processes ; these increase in length and 

 rise on the arch in the first seven or eight dorsals, while in the posterior five or six, 

 on the other hand, they descend and shorten (text-fig. 82). In the middle of the back 



Posterior dorsal vertebra of Cryptocleidus oxoniensls : A, from front ; B, from left side. 



(R. 2418, I nat. size.) 



a.z., anterior zygapopliysis ; w.e., neural canal ; «.s., neural spine ; p.xr., posterior zygapophysis ; 



»•./., facet for rib ; t.p., transverse process. 



they are moderately long and curved, the concavity being downwards. The neural 

 spines on the dorsal region are shorter and narrower than in Muroenosaurus ; in the 

 young animal they are stout, but much shorter than in the hinder part of the neck. 

 The zygapophyses in the anterior part of the neck are larger, and look more directly 

 upwards and downwards than in the posterior portion. There seem to have been four 

 sacral vertebrae (text-fig. 83), each bearing a pair of stout ribs {s.r.), which articulate 

 partly on the arch and partly on the centrum and are enlarged distaUy {s.f.) ; whether 

 or not they actually joined the ilium is uncertain, but from the presence of deep 



