DAKOTA AND NEBRASKA. 137 



The face is both higher and wider than in Agriochcertis antiquus, and in these 

 respects resembles more in its proportions that of robust or male individuals of 

 Oreodon Cidhertsoni. It is, however, proportionately shorter than in the latter. 



The forehead between the post-orbital processes is about an inch wider than in A. 

 aniiqims, nor is it so abruptly depressed upon these processes as in the latter. 

 Posteriorly it is deeply depressed at the bifurcation of the sagittal crest. The front- 

 als are sejiarate, and form together posteriorly an acute angle, received between the 

 co-ossified parietals. The fore part of the forehead is destroyed. 



The orliits are open behind, but appear rather less oblique at their outlet than in 

 A. aiitiquus. 



No lachrymal fossa, so conspicuous a feature in Oreodon, exists in front of the 

 orbit. 



The palate, exposed in the specimen through an accidental fracture, is almost 

 absolutely flat. In Agriochoerus antiquus, where it is exposed between the position 

 of the j^remolars, it is comparatively narrow, and the two sides incline in an unusual 

 degree, the angle being about 30°. In a transverse section the sides appear sigmoid, 

 ascending more abruptly near the median palate suture and descending more ab- 

 rujjtly near the alveolar border. 



The lower jaw is identical in form and proportions with that of Oreodon Cidhert- 

 soni, except that the rami are more extended or produced backward of the line of the 

 condyles. The dentary portion is relatively of somewhat greater depth than in the 

 jaw fragments of A. antiquus. 



The fossil confirms the suspicion that the formula of dentition of Agrioclion-us is 

 the same as that of Oreodon. On the left side of the specimen the molar series is 

 preserved complete, with the teeth all entire, seven in the upper and six in the lower 

 jaw. (Figure 1, plate XIII.) They are altogether slightly smaller than in the first 

 described specimens of Agriochoerus antiquus, notwithstanding the face is somewhat 

 larger than in this. 



The molars hold the same relative position with one another as in Oreodon, and in 

 a lateral view present a strong resemblance to them, save in the difterence of the 

 abutment-like ridges of the upper true molars. (See figure 1, plate XIII.) 



The lower molars are separated from the canine teeth by a comparatively large 

 interval, which is nearly half an inch. In Oreodon Culbertsoni the first premolar 

 succeeds closely upon the canine. In Agriochoerus latifrons the edge of the jaw at 

 the hiatus is thin and concave, and exhibits no trace of having accommodated an 

 additional tooth. 



In the ujDper jaw the incisors and canines, with the corresponding part of the face, 

 are broken off and lost close upon the position of the molar series. 



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