DAKOTA AND NEBRASKA. 79 



sometimes are nearly flat. In diiferent skulls they vary much in breadth and degree 

 of convexity. 



The maxillary bone articulates on the facial surface behind with the frontal, 

 lachrymal and malar bones. Above, it joins the nasal bone, and in front separates 

 this from the upper extremity of the premaxillary. 



The premaxillary bone is comparatively small, and projects very little beyond the 

 line of the upper canines. The alveolar portion is constructed like that in the Wolf, 

 but projects less forward. The ascending portion is hardly visible laterally except at 

 its upper expanded end, which is partly received into a notch of the maxillary, and, 

 as before indicated, is separated by an angular notch from the nasal bone. 



The palate plates of the palate bones are large, and occupy nearly all the space 

 between the position of the true molars, as in the Deer. 



Inferior maxilla. — The lower jaw of Oreodon partakes of the form of that of the 

 Anoplotherium and that of modern suilline animals. 



The body of the jaw is comparatively short; the" posterior portion, or ascending 

 ramus, is broad and deep. 



The outer side of the body is vertical and moderately convex. The symphysis 

 slopes as in the Hog, and forms an angle of about 45°. The chin is convex, and 

 not so broad as in the Peccary or Hog. The alveolar portion of the jaw ascends 

 in a moderate degree posteriorly, so as to form a curvature. Tlie base is nearly 

 straight, or feebly convex in its length, but descends in a more convex manner at the 

 angle, and is slightly protuberant below the symphysis. 



The technical angle of the jaw forms a prominent expansion of the bone with a 

 thick convex border, in the same manner as in the Peccary and Hog, but to a greater 

 degree. The expansion is less prominent posteriorly than in Anoplotherium, but is 

 higher, reacliing to within a short distance of the condyle. 



The condyle, the notch in advance, and the coronoid pi'ocess approximate those of 

 the Peccary in form and relationship. The condyle is almost identical in form and 

 relative position, but is narrower externally. The notch is deeper and wider; inter- 

 mediate in character to that of the Peccary and Hog. The coronoid process is inter- 

 mediate in form and size to that of the latter animals. 



Below the coronoid process and adjoining notch the ramus is depressed into a fossa 

 better defined and much deeper than that in the Peccary. 



The mental foramen occupies a position below the second premolar tooth, and 

 usually a second is situated a short distance behind it. 



The symphysis of the lower jaw remains open, or is unossified, even in old skulls 

 of Oreodon, as in ordinary recent ruminants. 



Dentition. — As previously intimated, the dentition of Oreodon is remarkable for 



