552 DESCRIPTION OF A NEW SPECIMEN OF GLYPTODON 
ordinary mammal, its terminal face being a very broad oval, slightly 
concave disk. The centrum of the penultimate coccygeal is much 
flatter and narrower ; and this flattening and narrowing predominates 
still more in the antepenultimate and that vertebra which lies before 
it, or the fourth from the end. From this point to the two anterior 
sacrals the floor of the vertebral canal is completely broken away, but 
there can be no doubt that the centra were represented by a thin 
bony plate. 
The line of the centra of the coccygeal vertebre forms a very 
marked arch behind the two sacral vertebrae, whose centra form a 
nearly horizontal floor; while the dorso-lumbar vertebre (including 
the trivertebral bone) form a second arch, flatter than the first. 
The spinous processes of all these lumbo-sacro-coccygeal vertebra, 
up to the fourth from the end inclusively, are anchylosed together 
in a long and strong osseous crest, broad and extremely rugose above, 
eight inches high in front, but slowly diminishing as it follows the 
curve of the centra posteriorly to five inches. 
The spinous process of the penultimate coccygeal vertebra is very 
thick, but is broken short off. It was probably not less than 4 inches 
high, and afforded a middle point of support for the carapace between 
the ischial protuberances. The sides of the median crest, and of the 
two vertebrae which appear to constitute the true sacrum, are anchy- 
losed firmly with nearly the whole of the inner edge of the vast 
ilium. Behind these the vertebrae seem to have been devoid of 
transverse processes, as far as the fourth from the end. But the 
antepenultimate had a long and slender transverse process on each 
side ; the penultimate has an equally long but much stouter process, 
while the last coccygeal vertebra has transverse processes of no less 
length, and extremely stout. 
The expanded distal ends of these processes unite with one another 
and with the inner surfaces of the greatly expanded ischia. 
The ilia are immense quadrate bones, slightly concave anteriorly 
and posteriorly, with their planes so directed as to form rather less 
than a right angle forwards with the vertebral column. The crest 
of each iliac bone is thick, expanded, and rugose, and so arched as 
evidently to have afforded attachment and support to the carapace ; 
which therefore rested directly, partly on the three transversely 
disposed pillars afforded by the coccygeal vertebre and the two 
ischia, partly on the longitudinally arched crests of the sacrum and 
of the thirteen dorsal or dorso-lumbar vertebra, and partly on the 
second great transverse support yielded by the arched crests of the 
ilia. Apart from their anchylosis, the whole of the parts named 
