OREODON. 33 



ruminants, the pars petrosa borders a large irregular excavation, constituting the 

 foramen lacerum posterius, and anterius, and a portion of the Eustachian tube. 



Immediately posterior to the foramen lacerum, and internal to the base of the 

 paramastoid process, the hypoglossal or anterior condyloid foramen is situated. 



The foramen ovale holds the same relative position as in recent ruminants, being a 

 little to the outside of the commencement of the pterygoid processes, and in advance 

 of the bony process of the Eustachian tube. 



The glenoid articulation, one of the most important features of the cranium in 

 reference to the habits of the animal, is broad as in existing ruminants, is slightly 

 convex anteriorly and concave posteriorly ; and in this position is bounded by a 

 mammillary post-glenoid tubercle, which is compressed antero-posteriorly, and is 

 relatively very large and robust. This tubercle is a very conspicuous object in the 

 lateral view of the head, and projects below the auditory process and bulla. Between 

 it and the auditory process is a narrow fissure, and at the bottom of this internally 

 is the glenoid foramen. 



Antero-internally, the glenoid articulation is prolonged upon a broad surface for 

 muscular origin, formed by the conjunction of the post-sphenoid and pars squamosa, 

 and terminating anteriorly in a pyramidal eminence, as in the Deer. 



The pterygo-palatine notch is long and narrow, and extends as far forward as 

 the posterior third of the last molar. Its margins are thick, strong, and rounded. 



The notch extending between the palate bone and the tuber maxillare is almost 

 as deep as that of the Deer, but is more angular. It terminates on the same line 

 nearly as the pterygo-palatine notch, as in the Sheep. 



The hard palate is slightly arched, and deepens in an angular manner towards 

 the centre. In some of the specimens it deepens very much, and in others not 

 more than in the Deer in advance of the molars. Its lateral margins, correspond- 

 ing with the alveoli, are nearly parallel throughout the course of the molar series. 



The posterior palatine foramina are pierced in the palate plates of the superior 

 maxillary bones on a line with the fourth or third premolars. 



The position of the incisive foramina, as far as can be ascertained from the imper- 

 fect specimens, appears to be on a line with the canine teeth. 



Orbits. — (PI. IV. Fig. 3; VI. 4, 6.) As before observed, the entrance of the 

 orbit is subrotund and directed outward, and a little forward and upward. Its 

 margin is less prominent than in the Deer, and at the inner canthus is elevated 

 into a vertical, slightly sigmoid, compressed mammillary, lachrymal process. The 

 inner wall of the orbit is more oblique in its course backward to the optic foramen 

 than in the Deer, and the alveoli contribute more to its floor, which is deep and 

 concave. 



The entrance to the infra-orbital canal is a broad oval orifice at the lower part of 

 the front of the orbit, formed below by the alveolar processes and above by the 

 lachrymal and palate bones. 



The lachrymal foramen is vertically oval, and contracted at its lower part, and 

 is situated just within the lower part of the lachrymal process. Near it externally 

 is a small round foramen. 



