OOLITIC DINOSAURS. 175 



fellow for strengthening the neural spine. The two short ridges converge and 

 unite to form the anterior plate of the diapophysis ; a deep triangular pit inter- 

 venes between these two anterior converging transverse ridges. From the upper 

 part of the diapophysis a strong and broad compressed plate curves upward to 

 abut upon the side of the neural spine ; as it approaches the spine it divides, the 

 shorter and lower division terminates about 6 inches from the summit of the 

 spine, the longer and sharper division attains the outer part of the spine's summit. 

 A deep and large triangular fossa is bounded by the anterior ridge of the neural 

 spine, by the antero-transverse ridge of the diapophysis below, and by the upper 

 diapophysial ridge behind. The dejDth of this fossa is 5 inches. 



The diapophysis derives its origin also from two other plates of bone : one, «. 

 nearly vertical and inferior, commences a little above the base of the neurapo- 

 physiSj rather nearer the hind than the fore part ; it rises and is lost upon the 

 under surface of the diapophysis, which it seems to support. The outer border of 

 this plate is 5 inches in extent, the greatest breadth is 3j inches ; it constitutes 

 the hind wall of the large "anterior neurapojAysial cavity, o- The back part of the 

 diapophysis is formed by a horizontal plate, 5, beginning at the origin of the 

 postero-lateral buttress of the neural sjoine ; thence it extends, losing breadth, to 

 the hinder and under surface of the diapophysis. This diapophysial plate is 

 horizontal, and forms the floor of a deep triangular posterior fossa, ^, at the base 

 of the neural spine ; the depth is 3 inches. 



The diapophysis with this four-ridged complex origin extends, measured from 

 the bottom of the anterior interspace between the horizontal and the vertical plates 

 of origin, 10 inches in an almost directly outward course ; the triedral form 

 changes beyond the middle of this length to a subelliptic one, which swells out 

 into a large oblong terminal tuberosity, d, with . the articular surface for the rib 

 bevelled off obliquely from its upper part. 



The four-fold buttress-plates bespeak the size and weight of the rib supported 

 by this process. As there is no parapophysis it may be inferred that the present 

 vertebra has come from a part of the dorsal series behind the anterior ones which 

 have developed their lower process for a double articulation of the rib. 



The concavity at the hind part of the centrum, c, corresponds in shape and 

 depth with the ball at the fore part ; the margin of the cup is more or less broken 

 away. The outlet of the neural canal, ]fc, is more oblique than the inlet, but has 

 a similar small area. Above it is a deep triangular cavity, the side-walls of which, 

 as they ascend and converge, curve backward and unite in a point which slightly 

 overhangs the centrum. The depth of the cavity so formed is 85 inches. Above 

 the roof of this cavity are a pair of smaller fossfe, and above these the broken base 

 of the neural arch from which the post-zygapophyses had been developed. A 

 deep median pit is excavated between the bases of the post-zygapophyses, and 



