THE CAMBRIDGE GREENSAND. 633 
The sides of the vertebra are well rounded; but at the upper third, 
behind the middle of the centrum, is another pair of longitudinal 
ridges, which become produced into very short transverse processes, 
compressed from above downwards, and imperfectly preserved; the 
third pair of ridges are those which form the bases of the neural 
arch, between which and the transverse processes the upper part of 
the side of the centrum is concave. These pedicles, from which the 
neural arch is broken away, are compressed from side to side, di- 
verge a little as they extend backwards, reach to near the anterior 
margin, and extend backwards for about 1,2, inch. The outside 
transverse measurement of these ridges in front is 58; inch, behind 
it is about 1,2, inch. 
Several vertebrae appear to be missing between the centrum de- 
scribed and the second of the series, which has unfortunately been 
fractured longitudinally and vertically, so that it is little more than 
half a centrum. ‘The fracture shows the bony tissue to be arranged 
in short, irregular, parallel longitudinal lamin, about 54, of an inch 
apart. The centrum is longer along the ventral than the neural 
surface, the superior measurement being less than 2 inches, and the 
inferior measurement about 2} inches, indicating that the tail was 
curved in an opposite direction to the back, as might be expected. 
The anterior articulation is much wider than deep, the vertical 
depth being 14 inch, and the outline reniform, since the neural canal 
impresses the centrum concavely. The posterior articulation is much 
more deeply excavated above; the antero-posterior measurement 
through the middle of the articular faces is 1,4, inch. The greatest 
vertical measurement (1,8, inch), from the hinder ridge of the neural 
arch to the facet for the chevron bone, is about equal to the greatest 
transverse measurement in the upper third of the centrum. 
The subcylindrical centrum, which enlarges towards the two ends, 
is modified hexagonally by eight longitudinal ridges, two on the 
base, faint and parallel, becoming strong posteriorly, where they ter- 
minate in the oblique facets for the chevron bone. ‘The side of the 
centrum below the neural arch is divided into three regions by two 
moderately elevated longitudinal ridges: the lower region is flat, 
and measures 58, inch from above downwards; the middle region is 
slightly concave and about half as wide; while the upper region is 
more concave, and has a depth of 5%, inch. The upper of these 
lateral ridges becomes prolonged outward behind the middle line 
into a slight vertically compressed transverse process. The neural 
canal is still large, but the arch is smaller; its pedicles are very 
slight, are on the inside of the neural ridges, and only measure 
about 5, inch in length. 
The third vertebra of the series has the centrum 2,1, inches long 
on the inferior margin, and is smaller in all measurements. The 
transverse tubercle has now disappeared, and the lateral ridges are 
obscure. The ridges which terminate in the facets for the chevron 
bone are well developed posteriorly, and terminate in two distinct 
surfaces, which look obliquely downwards and backwards. The 
neural arch is small, and extends to within half an inch of the an- 
