PEOFESSOE HUXLEY ON THE OSTEOLOGY OF THE GENUS GLYPTODON. 65 
Seated upon the upper face of the neural arch are two other oval articular surfaces 
(b, b'), which answer to the postzygapophysial surfaces upon the under surfaces of the 
hinder part of the neural arch of the trivertebral bone. 
The inner part of each of these articular faces is convex in all directions ; the outer 
is concave from side to side, convex from before backwards ; behind each lies a transverse 
fossa. 
The outer ends of the transverse processes are obliquely truncated, and each presents 
two articular facets, an anterior and inferior, larger, and a posterior and superior smaller, 
which articulate with corresponding facets upon the capitulum and tuberculum of the 
attached rib. A well-marked notch separates the hinder face of the transverse process of 
the first from that of the second vertebra ; and the intervertebral foramen is situated on 
the same level as this notch, on the one hand, and the anterior inferior facet, on the 
other, or about halfway between the upper and lower faces of the bone. 
The transverse process of the second vertebra ( d . 1. 4) presents two oval articular 
facets for the head of a rib, more nearly equal and more nearly on a level than those of 
the first vertebra. The transverse process of the third vertebra is broken on the left 
side ; but on the right side, traces of an elongated costal facet are visible. 
The ends of the lateral ridges representing the transverse processes of the fourth, 
fifth, sixth, and seventh vertebrae are broken away. 
In the eighth, ninth, tenth, and eleventh vertebrae (Plate VIII. fig. 7, d. 1. 10, 11, 12) 
they are preserved on the left side, broken away on the right ; on the twelfth vertebra 
the corresponding ridges are broken on both sides. 
I find no trace of articular surfaces for ribs on the lateral ridge continued along the 
eighth, ninth, tenth, and eleventh vertebrae, which, as I have stated, is entire on the left 
side ; but the upper and inner surface of the ridge is rounded and marked by longi- 
tudinal striations (fig. 7). The outer surface is rough and irregular, opposite the ante- 
rior part of each vertebra, and raised into an irregular tubercle posteriorly. 
The spinous processes of all the vertebrae are broken short off; that of the first is 
almost obsolete, being a mere ridge sloping back towards the second, into which it is 
continued. The anterior edge of the process is so much inclined backwards and 
upwards as to afford free play to the knobbed head of the spinous process of the triver- 
tebral bone (fig. 2). 
The spinous process of the second vertebra ( d . 1. 4) is 04 inch thick where it is 
broken through, and had probably a considerable height. A distinct interval separates 
it posteriorly from the thin anterior edge of the spinous process of the third vertebra, 
which is much thinner, and is anchylosed with its successors, as far as the eleventh inclu- 
sive, into a long continuous crest ; slight traces of the original separation of the several 
spinous processes, however, are visible at the base of the crest, and they may have 
been distinct at their apices. The crest gradually increases in thickness to the sixth 
vertebra (d. 1. 8) (where it attains 0*75 inch), and then gradually diminishes. The 
spinous process of the twelfth vertebra (d. 1. 14) may have been distinct down to its 
L 2 
