OSTEOLOGY AND DENTITION OF HYLOMYS. 463 
base of the transverse process to the root of the odontoid process, or at least to form a 
part of that ridge at its origin from the transverse process, because in the third ver- 
tebra an undoubted pleurapophysial element becomes distinguishable in a similar 
position. In the sixth cervical this plate becomes much developed antero-posteriorly, 
and is connected to the same process of the seventh vertebra, in which it is spinous 
and capped by a small ossicle in apposition with a similar ossicle on the sixth vertebra. 
In the thirteenth and fourteenth dorsal vertebre the intervertebral foramen has a 
process above and below, the inferior being the most strongly developed; and in the 
latter vertebra they are in such close conjunction that they produce a deep groove. A 
trace of this arrangement is also observable in the twelfth dorsal. The superior 
of these processes in the fourteenth dorsal is in the same line with the transverse 
process of the first lumbar. In the lumbar vertebrae these processes are thin longitu- 
dinal plates extending the whole length of the bodies of the vertebra, with their tips 
directed outwards and very slightly forwards. In transmitted light they are seen to 
consist of two portions—a thick anterior transverse, with a fine osseous lamella con- 
tinuous with it behind. In the tail these processes can be detected as far back as the 
sixth vertebra. In the first and second they are antero-posteriorly expanded; but the 
largest does not extend along the whole of the body of its vertebra, and they rapidly 
decrease in size. The vertebrarterial canal perforates all the cervical vertebra, but is 
largest in the sixth. On the axis it opens externally immediately below the foramen 
for the inferior branch of the first spinal nerve. 
Hypapophyses.—A small bifurcate process occurs on the atlas; and a well-developed 
hypapophysial plate all the length of the centrum, and terminated posteriorly by a 
recurved hook, appears on the axis. An almost as extensive plate is seen on the third 
cervical; and the fourth vertebra is distinguished by a well-marked bifurcate process, 
while from the fifth cervical to the fifth dorsal there are distinct indications of a hypa- 
pophysial ridge. In the cervical it is a fine, low ridge, which increases in width from 
" before backwards; but in the dorsal vertebre it is hardly distinguishable as such. The 
first to the third lumbar vertebree show a hypapophysial ridge which consists almost 
of two lateral halves, whereas in the fourth to the sixth it is simple. A simple ridge 
occurs also in the first sacral vertebra. 
Chevron bones occur from the second to the seventh caudal vertebra, the united 
bones of each side resembling the figure H. 
The scapula (fig. 12) is rather narrow; but its distinguishing feature is the great 
development of the mesoscapula, which has a larger area than either the postscapula 
or the prescapula. The posterior margin of the bone is slightly concave, but nearly 
straight, whilst the prescapula forms nearly the half of a very elongated oval. The 
upper postscapular margin is slightly convex. The mesoscapula is folded backwards, 
more especially at its lower acromial half, where its inferior acromial margin projects 
backwards beyond the hinder border of the postscapula. ‘The acromion is largely deve- 
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