OEEODON. 35 



other ruminants; but it is very much more oblique in its course than is usual in 

 these, and even more than in the Sheep. 



The internal pterygoid process shows itself as in recent ruminants, at the pos- 

 terior extremity of the orbit, between the vertical j)late of the palate bone, the 

 external pterygoid process, and the wing of the post-sphenoidal bone. 



The frontals remain separated in the adult condition, and are relatively shorter 

 than those of ordinary ruminants. They commence in an angular manner poste- 

 riorly, and expand rapidly forward and outward to the post-orbital margin, as in 

 the Camel, and then converge forward, the supra-orbital margins being nearly 

 straight, and terminate in angular processes which advance beyond the ossa lac- 

 rymalia. Anteriorly they form a deep notch, extending nearly to a line with the 

 anterior orbital margin, for the reception of the posterior extremities of the oss&, nasi. 



The forehead, as constituted by the ossa frontis, ordinarily is prominent and con- 

 vex above the orbits, and slightly depressed along the median line or course of the 

 frontal suture. The orbit presents more upward than in recent ruminants, and 

 the post-orbital process in its descent to join the malar bone is directed more out- 

 ward ; and it also is directed backward, as in the Camel, though not to the same 

 relative extent. The nasal bones, anterior to the angular processes of the ossa 

 frontis, are of nearly uniform breadth, are slightly convex, and incline more or less 

 outwardly. 



The lachrymal bone forms two sides of an irregular cuboidal figure, with the 

 facial side depressed into a deep hemispherical lachrymal sinus. The two 

 sides are sub-equal, and their angle of union constitutes the anterior orbital 

 margin. Inferiorly the orbital side forms the supero-external boundary of the 

 entrance to the infra-orbital eanal; and postero-internally it is deeply notched for 

 the reception of the upper extremity of the palate bone. 



As in recent ruminants, the lachrymal bone articulates with the os frontis, os 

 maxillare, os malse, and os palati ; and it is separated some distance from the os nasi 

 by the advance of the angular process of the os frontis. 



The palate plates of the ossa palati advance as far as the position of the first 

 true molar, and in some specimens, to the interval between the latter and the fourth 

 premolar. The vertical plates are shallow, but relatively broader than those of 

 recent ruminants. 



In the orbit, the palate bone forms the internal boundary of the entrance to the 

 infra-orbital canal, and is pierced internal to this by the posterior palatine canal, 

 and the homologue of the spheno-palatine foramen. It articulates wnth the maxil- 

 lary, the frontal wing of the anterior sphenoid, the anterior margin of the internal 

 pterygoid process, and the extremity of the external pterygoid process. 



The superior maxillary bone, compared with that of recent ruminants, is not as 

 short as might be supposed ; for the space in these which constitutes the hiatus 

 anterior to the molar series, is in Oreodon occupied by a molar additional to the 

 ordinary functional number, together with a well-developed canine ; leaving a little 

 vacancy for the accommodation of an inferior canine. Its outer side is vertically 

 convex, but is depressed in advance of the infra-orbital foramen. 



The suture between the maxillary, and malar and lachrymal bones, ascends in 



