82. 0. C. Marsh—Principal Characters of Coryphodontide. 
The skull of Coryphodon, in all its more important characters, 
is of the perissodactyl type. It is elongated, and the facial 
portion is most produced. A line drawn from the lower mar- 
gin of the foramen magnum along the palate is nearly straight. 
The zygomatic arches are expanded, but the malar is compara- 
tively slender, and unites with the maxillary in front of the 
orbit. The general form of the skull is shown in the accom- 
panying plate, figure 1. The maxillaries are massive, and 
usually deeply indented on the sides behind the canines. The 
lachrymal forms the anterior border of the orbit, and its fora- 
men is inside the orbital margin. The nasals are slender in 
front, and broad posteriorly. The premaxillaries are expand 
transversely, and the narial aperture is wide. The occipital 
condyles are well separated, and there are condylar foramina. 
Between the basisphenoid and the periotic, there is a large 
opening. ere is a paroccipital, and a,post-glenoid process. 
The dental formula of Coryphodon is as follows : 
Incisors 3 canines <3 premolars = ; molars a x2 
The teeth in American specimens do not differ essentially 
from those described by Owen and Hébert, which are well repre- 
sented in the memoir of the latter author, cited above. 
The brain cavity in Coryphodon is perhaps the most remark- 
able feature in the genus, and indicates that the brain itself 
was of a very inferior type. It was quite small, as in 
Eocene mammals, but its most striking features were the small 
size of the hemispheres, and the expanded cerebellum. The 
form and relative size of these are shown in the accompanying 
plate, figure 1. 
he olfactory lobes were large, and entirely in advance of 
the hemispheres. They were bounded in front by a well ossified 
cribriform plate, and partially separated by a vertical bony sep- 
tu e cerebral lobes were ovate in form, and very small, a 
transverse section exceeding but little that of the medullar 
opening. In shape and relative size, the hemispheres and olfac- 
tory lobes of this genus are somewhat similar to those of Dino- 
ceras. The cerebellum was proportionally large, and widely 
expanded transversely. Its peculiar form is shown in figure 1, 
which is drawn from a cast of the brain-cavity of C. hamatus. 
This portion of the brain nearly or quite equaled the hemi- 
spheres in size, thus differing widely from any known mammal. 
There is a well marked pituitary fossa, but no clinoid process. 
The foramina for the exit of the optic nerves are small, but for 
the others very large. The brain as a whole was very low in 
grade, and precisely such as might be expected in a mammal 
from the odes Tertiary deposits. 
