OF THE WHITE RIVER BEDS OF MONTANA. 207 



M. 



Length of bulloe, antero-posterior 021 



Width of bullffi 0l6 



Length of last three temporary premolars 033 



Length of molar series 047 



Agriochoerus maximus, sp. nov. (Plate IX, Fig. 4.) 

 Type No. 58. 



Of this animal there is a right molar-premolar series and the last two premolars and 

 the first two molars of the left side, with some small skull fragments. They were found 

 on the Little I 'ipestone, southwestward from Whitehall. These teeth do not look like those 

 of Agriochoerus, principally on account of their lowness and plain, flat appearance ; yet 

 when they are compared one by one with those of Agriochoerus, one does not feel warranted 

 in establishing a new genus on these alone ; though if a skull and skeleton were found, I 

 have little doubt that the animal might prove to be a different thing. 



Distinguishing characters : Size large; teeth plain ; the ci heeh teeth low, except P 1 , 

 made up of crescents which are approximately low three-sided pyramids with broad bases. 



P 1 subconical, longer than wide, with an anterior angle and a posterior depression ; 

 two-rooted. P 2 simple!, pyramidal; the outer side convex; the antero-inner nearly fiat; 

 postero-inner side concave, with a weak cingulum. P ;! three-rooted, with a small deu- 

 terocone. The two inner sides equal. There is an incipient tendency toward the division 

 of the outer crescent, as seen in the slight inner groove just behind the inner angle and 

 the apex of. the protocone. P 4 has the same length as P 2 and P 3 but is broader. The 

 two outer crescents are not separated down as far as in the molars. The deuterocone is 

 as laro-e, though not as high, as the outer crescents. It is subconical or subtriangular in 

 section. There is a trace of a tritocone which looks like a cingulum. There is a faint 

 cingulum nearer to the root. . 



M 1 has short, broad, low crescents, with broad open valleys between. M 2 and M 3 

 are the same hut longer antero-posteriorly. The animal was not old, as M 3 had been 

 recently erupted. 



A small portion of the top of the skull shows the angle where the temporal ridges 

 unite to form the sagittal crest. In the angle is a broad concavity and the ridges are 

 broad and prominent, There is no deep groove at the angle. The anterior part of the 

 sagittal crest is a low, broad convex ridge. 



Measurements. 



M. 



Length of molar-premolar series about* 124 



Length of premolar series 052 



*The posterior half of M ;l - is injured, and it is reckoned as the same length as the anterior part. 



