OREODON OF NEBRASKA. 541 



souri, crania and fragments of crania, and jaws with teeth, more or less perfect, 

 of at least twenty-six different individuals of at least two distinct species of Oreodon. 

 From this abundant material we are enabled to trace out almost all the anatomical 

 details of the head of the animal, which I shall do without the unnecessary reference 

 to particular specimens in the course of the description. 



The head in its general form (Tab. x., 4-6; xi., 2, 3), resembles more that of 

 the Camel than of any other existing Ruminants. It has an almost unbroken arch 

 of teeth in both jaws, composed of molars, canines, and incisors. The head of one of 

 the species of Oreodon is about the size of that of the Wolf of Pennsylvania ; the other 

 is about the size of that of the Badger. To the former I have given the name of 

 Oreodon Cidbertsonii, to the latter that of Oreodon gracile. The characters common 

 to both the species mentioned, I shall now proceed to give in detail as belonging to 

 the genus, and afterwards point out the specific differences in addition to the size. 



Side view of the shall. — (Tab. x., fig. 5; xi., fig. 2.) The temporal fossa is con- 

 structed like that of the Camel, and is relatively about as large as in that animal. 

 It rises to the middle line of the cranium, upon a parietal crest extending the whole 

 length of the single parietal bone. Posteriorly, it is bounded by an oblique ridge, 

 separating it from the occipital surface. Antero-superiorly, it is bounded by a 

 slight ridge running outwards upon the post-orbital process. The surface generally 

 is convex, is most prominent along the course of the squamous suture, and nearly 

 one-half of its extent is constituted by the squamous portion of the temporal bone, 

 as in the Camel and Lama. 



In some of the specimens, the parietal bone along the course of the squamous 

 suture and contiguous to it is depressed into a groove. 



The zygomatic arch is relatively much broader and stronger than in any existing 

 Ruminants. 



The malar bone is robust, and its outer surface presents upwards and forwards, 

 or is on the same plane with the orifice of the orbit. 



The post-orbital process is united, as in existing Ruminants, with the malar bone, 

 so as to form a narrow arch. 



The orbital entrance is subrotund, and is directed forward to about the same 

 extent as in the Deer, but in a trifling degree more upward. 



The face at its lower part, in comparison with that of the Deer, appears not only 

 shortened to an extent equal to the vast unoccupied space anterior to the molars in 

 the latter animal, but appears also to recede so as to bring the last molar on a 

 line perpendicular to the post-orbital arch. 



The face, from the latter on each side forwards, forms an almost equilateral triangle. 

 Its sides are more vertical than in the Deer, and form a continuous convexity from 

 the middle nasal suture downwards. 



The most remarkable feature in the lateral view of the face is the very large 

 lachrymal depression, which is nearly hemispherical, and extends slightly beyond 

 the borders of the lachrymal bone. 



The infra-orbital foramen is situated above the third premolar tooth. 



The anterior extremity of the floor of the nose constituted by the superior incisive 



