PROFESSOR HUXLEY OX THE OSTEOLOGY OF THE GENUS GLYPTODON. 61 
The posterior face of the bone exhibits, below, a large round aperture (fig. 7, a), 
leading into a passage which traverses the posterior canal just described, and debouches 
into the middle one. 
Immediately beneath this foramen is a small concave articular surface, apparently a 
fragment of a much larger one. 
Superiorly and internally the posterior face of the bone presents a deep fossa (fig. 7, a), 
bounded above and internally by a concave articular facet, the long axis of which is 
directed almost at right angles to the long axis of the bone. 
The facet in question I take to correspond with the posterior oblique process or 
“ post-zygapophysis ” of the fourth cervical vertebra. The foramen on the posterior 
face is the aperture of the canal for the vertebral artery. The facet below it is part of 
an articular surface upon the inferior or “ capitular ” division of the transverse process, 
which is characteristic of the cervical vertebrae in Armadillos; and the middle and poste- 
rior canals are the intervertebral foramina for the third and fourth cervical nerves. 
The upper and inner foramina and canals represent the remains of the primitive inter- 
spaces between the several arches. The anchylosed spinous processes, and the bodies of 
the three coalesced vertebrae, are completely broken away, so that nothing can be said 
regarding their characters. 
The fifth and sixth Cervical Vertebrae. — No remains of the fifth and sixth cervical ver- 
tebrae have been discovered among the bones sent by Sehor Terrero. 
The “ Trivertebral bone” or anchylosed seventh Cervical and first and second Dorsal Ver- 
tebrae (Plate VII. figs. 3, 4, 5, 6). — The three vertebrae which enter into the composition 
of this singular bone are very much depressed from above downwards, so that the neural 
canal is more than twice as wide as it is high ; while the greatest depth of the whole 
bone, leaving the spinous process out of consideration, is hardly a fourth of its width. 
The inferior face of the bone is deeply concave from side to side ; and as the floor of the 
neural canal is also concave, the part which corresponds with the centra of the anchylosed 
vertebrae has the form of a broad thin arched plate, thinnest in the middle. The supe- 
rior arches of the vertebrae, which constitute the roof of the trivertebral bone, follow, in 
a general way, the contour of its floor ; but they are much thicker ; and, posteriorly, the 
roof of the trivertebral bone is produced, upwards and backwards, into a very thick 
short process, which probably represents the spinous processes of the two anterior dorsal 
vertebrae. The lateral parts of the trivertebral bone, which represent the anchylosed 
transverse processes of the vertebrae, are very thick and stout, especially in front. 
Viewed from above, or laterally, they are seen to be marked out by excavations into 
three portions, one for each primitive vertebral constituent of the bone. With the 
lateral excavations the heads of the two anterior ribs articulate. 
So much for the general characters of this bone. A front view (Plate VII. fig. 5) 
exhibits the following features, worthy of more particular description. The lateral 
mass, which represents the transverse process of the first of the three vertebrae, presents 
an elongated oval articular facet (a), convex from above downwards and looking almost 
