542 



OEEODON OF NEBRASKA. 



alveoli is convex, and resembles more that of the Anoplotherium than of any exist- 

 ing Ruminants. 



Superior view. — (Tab. x., fig. 6.) In this view of the skull it resembles in its 

 form more that of the Wolf than of any existing Ungulates. The parietal crest is 

 relatively about as high as in the Camel. It bifurcates at the coronal suture into 

 the ridges bounding the temporal fossa upon the post-orbital processes. 



The forehead is relatively narrower than in the Deer, but broader than in the 

 Wolf, and is more convex than in either. 



Upon each side of the frontal suture, and nearer the anterior than the posterior 

 extremities of the frontals, is a large supra-orbital foramen. The form of the 

 muzzle in advance of the orbits is like that of the Musk-deer, except that it is more 

 convex laterally. 



The anterior extremity of the nasal bones is broken away in all the specimens, 

 so that the form of this portion of the face cannot be ascertained. 



Posterior view. — The occipital surface is intermediate in form to that of the Musk- 

 deer and Wolf, and is smoother and relatively narrower than in the latter. Its 

 lateral margin separating it from the temporal fossas, is formed above by the con- 

 junction of the parietal and occipital bones, and below, as in recent Ruminants, 

 by the combination of the posterior temporal crest with a superficial process of the 

 petrosa, wedged in between the former and the corresponding margin of the occi- 

 pital bone. 



The occipital condyles have very much the same form and relative position to 

 each other that they have in the Deer, but are narrower and more prominent infe- 

 riorly. 



The occipital foramen is rather transversely oval, with nearly vertical sides, and 

 emarginate above. Its inferior margin between the condjdes is placed more poste- 

 riorly in its relation to the superior margin than in the Deer, so that the foramen 

 is directed more backward. 



Inferior view. — (Tab. x., fig. 4.) The basilar process is prismoid, very much 

 depressed laterally from the level of the occipital condyles, with the sides looking 

 outward, and the middle prominent. The surface of the sphenoidal bodies incline 

 very gradually upward and forward. 



The para-mastoid process forms the infero-lateral termination of the occiput, and 

 relatively to that of recent Ruminants is very long and strong. It is elongated 

 pyramidal, bent a little forward and outwards, and is longitudinally excavated 

 antero-externally. 



The mastoid process forms the posterior boundary of the meatus auditorius 

 externus, and projects downwards between the auditory process and the inferior 

 extremity of the occipital process of the os petrosa. 



The os tympanica is moderately developed, and abuts posteriorly against the base 

 of the para-mastoid process. The stylo-mastoid foramen occupies the same relative 

 position as in the Deer, and internal to it is a depression for the styloid process. 

 Internal to the auditory capsule, is a large depression, corresponding to the foramina 

 lacera anterius and posterius. 



Just posterior to the foramina lacera, and internal to the base of the para-mastoid 



