509 
THE OSTEOLOGY OF HYiENODON. 
and especially the anterior pair, are very widely separated and present almost ver- 
tically. ilie neural spine is very little developed, the great overhfinging spine of 
the axis leaving hardly any space for it. The transverse process forms a thin, com- 
pressed plate considerably longer than the centrum, from which it diverges at a wide 
angle. The fourth vertebra is like the third, with all its peculiarities exaggerated; 
it is shorter, heavier, with faces more oblique to the long axis of the centrum ; it 
has a lower, broader neural arch, and more widely separated zygapophyses. The 
free margin of the transverse process is strongly concave, instead of straight, and 
hence the process is partially separated into anterior and posterior portions. The 
neural spine is slightly higher than on the third. The fifth and sixth cervicals 
dilTer only in minor details from the fourth, the principal changes being the gradu- 
ally increased height of the neural spines and the narrowing of the neural arch and 
canal. On the seventh vertebra the spine becomes relatively very high ; the cen- 
trum is short, broad, and depressed, the transverse process heavy, straight, and im- 
perforate. 
As a whole, the neck of Hymiodoti is surprisingly short and light, when com- 
pared with the size of the head, the skull considerably exceeding the neck in length. 
The small size of the processes on the cervical vertebrae is evidence that the neck 
could not have been so heavy and muscular as in most of the recent Carnivora. 
I'he thoracic vertebrce number fourteen and, like the cervicals, are proportion- 
ately small and weak. In the anterior region the centra are short, gradually in- 
creasing in length as we pass backward. The first thoracic vertebra has very 
prominent transverse processes, which bear very large, concave facets for the tuber- 
cles of the first pair of ribs. The second thoracic has similar, but somewhat smaller 
processes, and on the other vertebne they become of the ordinary size, though con- 
spicuous on all, except the last two. The size of the spines vanes m the differen 
species ; in H. horridus they are relatively very heavy, while in the 
they are light and delicate. In height and in backward niclinatmn^ 
nosteriorlv the 11th being the anticlinal vertebra, while the 12th, 13th and 1 
have lowViiines of the lumbar type, inclining forward. The change in the charac- 
iKiv e low spines oi l ..grtebra; those of the posterior thora- 
entire column. Ihe onl} comp c c sei lumbars. There is no reason 
mined species, and in this hi H. horridus the lumbars 
to assume a diflerent numbei oi , gg^^ed slio-htly opisthocoelous and pro- 
have very large centra, which are broad, dep-- ^ ..g but not 
vided, except the last one ,g,,i,ate in a point. The spines 
