DESCRIPTION OF A NEW SPECIMEN OF GLYPTODON 549 
Of the vertebral column, the greater part of the sacral and dorsal 
region, and some fragments of the cervical region, are preserved. The 
atter show that the atlas was distinct, but that the axis was anchy- 
losed with one or two succeeding vertebra, as in the Armadillos 
The fifth and sixth cervical vertebrae were probably free, but no traces 
of them have been found. The anterior part of what remains of 
the rest of the vertebral column consists of a very broad flat bone, 
composed of three vertebre firmly anchylosed together, and having 
their spinous processes represented by a short but very stout osseous 
knob, which projects upwards and backwards. Anteriorly, these 
anchylosed vertebre exhibit on each side of the neural canal an arti- 
cular facet with a convex surface, resembling a segment of a horizontal 
cylinder ; posteriorly, articular surfaces of a similar character, but 
concave, are situated in corresponding positions. 
Each side of this ‘trivertebral bone’ presents two large and deep 
articular cavities for the heads of ribs, fragments of which are still 
preserved. The anterior rib, remarkable for its stout and massive 
proportions, was undoubtedly the first ; and this circumstance I believe 
gives a clue to the precise character of the vertebrae which are anchy- 
losed together to form the trivertebral bone ; for in the Armadillos 
the head of the first rib is fitted into a deep fossa, formed partly by 
the last cervical, and partly by the first dorsal vertebra. Furthermore, 
the body and transverse processes of the last cervical vertebra in the 
Armadillos present articular facets of an essentially similar character 
to those observable on the anterior face of the bone under description! ; 
and, finally, the last cervical vertebra is practically immoveable upon 
the first dorsal in many armadillos, while the two vertebre are com- 
pletely anchylosed together in the priodont Armadillo. I conceive, 
then, that this remarkable bone of the Glyptodon is formed by the 
anchylosis of the last cervical and first and second dorsal vertebre. 
Of the remainder of the spinal column thirteen consecutive ver- 
tebre are preserved; and all of these were immoveably united into 
one long continuous tunnel or arched tubular bridge of bone, a struc- 
ture which is without a parallel among the Mammalian Vertebrata. 
Of these thirteen vertebrz, the four anterior are so completely an- 
chylosed together, that the original lines of demarcation between 
them are hardly discernible. Persistent sutures separate the fourth 
from the fifth, and the latter from the sixth; but all trace of the 
1 I may remark in passing, that all the cervical vertebrae of the Armadillos, from the 
third backwards, are articulated together by joints similar in principle of construction to 
those which connected together the trivertebral bone of Glyg/odon with the vertebrz in front 
of and behind it. 
