part 3] TEOM THE WEALD CLAY OF BERWICK (sUSSEX). 289 



32 mm.; width =43 mm. ; height = 40 mm. In none of these 

 vertebrae is the neural arch preserved. 



Of the posterior cervicals (PL XIV, fig. 5) only the last fom- 

 are complete, the five in front of these being represented bj'- their 

 arches only. The fact that these vertebrae are still articulated one 

 with the other and are still partly embedded in matrix renders 

 their description difficult ; but it can be seen that the form of the 

 articular surface is similar to that of the anterior cervicals described 

 above. On the sides of the centrum the single rib-facets form 

 well-marked prominences which occupy rather more than half the 

 length of the centrum, and are situated nearer the posterior than 

 the anterior border. Beneath them on each side of the middle line 

 there is a depression into which a vascular foramen opens ; these 

 depressions are separated by a well-marked rounded haemal ridge. 

 The borders of the centra are raised into fine rugosities running at 

 right angles to the articular faces. The length of the centra is 

 less than the length or width, and the width is greater than the 

 height. 



The form of the thoracic vertebrae seems to be much like 

 that of the centra of the posterior cervicals, but doubtless there is 

 a transition to the condition seen in the dorsals. In these the 

 ventral surface becomes rounded from side to side, the haemal ridge 

 disappearing. The ventral surface of the centrum is perforated 

 near the middle line by a pair of small vascular foramina, and 

 there is another larger pair situated about a third of the w^ay up 

 the sides. The articular surfaces are evenly concave, wanting the 

 convex border seen in the cervicals, so that there is a sharp edge 

 between the articular surface and the sides of the centrum 

 which are strongly concave from before backwards. The dimen- 

 sions of a dorsal centrum are : — length = 31 mm. : width= 55 mm, ; 

 height = 48 mm. 



In the posterior cervical and thoracic regions the neural arches 

 are large and massive. In the last two cervicals the base of the 

 pedicle is produced into a short process which extends down to the 

 costal facet, but does not seem to have reached the rib : in the next 

 four vertebrae (thoracic) this process of the arch increases in size, 

 and forms more and more of the rib-articulation until in the first 

 dorsal it wholly supports it, becoming a prominent diapophysis {d.). 

 This is compressed from before backwards, and is enlarged tow^ards 

 its outer end, which bears a somewhat convex facet considerably 

 higher than wide. Followed back in the series, the dorsal rib- 

 facets become smaller, and their vertical and horizontal diameters 

 more nearly equal. 



In the posterior cervical and thoracic regions the zygapophyses 

 are large, and their articular surfaces are flat (making an angle of 

 about 45° wdth the median plane). They project so far anteriorl}'- 

 and posteriorly that, when they were in articulation one with the 

 other, there must have been a small interval between the articular 

 surfaces of the centra. This interval is, in fact, show^n in this 

 specimen, and it can be seen that it was partly occupied by a disc 



