$50 DESCRIPTION OF A NEW SPECIMEN OF GLYP?TODON 
primitive distinction of the sixth and seventh is lost. The other 
vertebra are separated by sutures which become coarser and less close 
posteriorly. In all but the first, second, third, eleventh, and _thir- 
teenth vertebra, the parts representing the vertebral centra are broken 
away; but where they persist, they are so similar that they were 
doubtless of similar form throughout. Each centrum is, in fact, a 
comparatively thin bony plate, so curved as to form a segment of a 
hollow cylinder of much larger diameter in the front than in the 
hinder vertebra, the sides of which pass superiorly into the arches of 
the vertebra. 
The foremost vertebra of the thirteen is as broad as the posterior 
part of the ‘trivertebral bone, and presents a couple of convex arti- 
cular facets which articulate with the lateral articular concavities 
described above in that bone. The vertebre rapidly narrow, how- 
ever, until the fourth is not more than three-fifths as wide as the 
first, while it is proportionately deeper ; and this increase of depth 
relatively to width goes on until in the thirteenth vertebra the spinal 
canal is deeper than it is wide. 
The spinous processes of these vertebrz are all broken short off ; 
but sufficient remains of their bases to make the following points 
clear. 
The spinous process of the first is almost obsolete, being a mere 
ridge sloping back towards the second, with which it is continuous. 
This appears to have been necessary to afford the requisite play for 
the knob of the trivertebral bone in its movements of flexion and 
extension on the rest of the spinal column. 
The spinous process of the second vertebra was long and thick, 
and probably somewhat high. It appears to have been completely 
distinct from the third, which was thinner, and was anchylosed with 
its successors (as far as that of the twelfth vertebra inclusive) into a 
long continuous crest. The apices of the spinous processes may, 
however, have been distinct. So much as is left of the base of this 
crest shows that it was thickest at the sixth and seventh vertebra (of 
the thirteen), and that it became thinner both anteriorly and _pos- 
teriorly. 
The spinous process of the twelfth vertebra, forming the termina- 
tion of the crest, appears to have ended in a free, thin, but rounded 
edge. What remains of the spinous process of the thirteenth ver- 
tebra, on the other hand, thins off anteriorly to a natural edge, which 
is inclined upwards and backwards. Posteriorly the spinous process 
becomes very thick and stout, and appears to have had a considerable 
height. It ends in a fractured hinder margin. 
