Douglass — New Species of Merycochoerus in Montana. 73 



Art. VI. — New Species of Merycochoerus in Montana. 

 Part II. By Earl Douglass. 



Merycochoerus altiramus n. sp. 



This species, from the Madison Lake beds of the Loup Fork 

 epoch, is represented by a right mandibular ramus which only 

 lacks the posterior border and some other small fragments. 

 The jaw is nearest like that of M. laticeps, but differs from it 

 in several respects. In the present species the lower border 

 slopes more uniformly downward and backward from the chin. 

 From pm4> backward the jaw is deeper. I know of no other 

 that is as deep in proportion to the length. The greatest 

 depth, back of m 3, was very nearly -| the greatest length. The 

 symphyseal border, at least the lower portion, was not con- 

 cave and it forms a larger angle with the lower border of the 

 jaw than in M. laticeps. The concavity under pms 3 and ^ is 

 less and the masseteric fossa is much deeper, being bounded in 

 front by a high narrow ridge which dies out on the alveolar 

 border under m 3. The lower border of the fossa is about on a 

 line with this border. There is a small foramen mentale under 

 the posterior part of pm 3. 



Dentition. — A small portion of the bone in front of pm 1 is 

 lost, but the lower portions of the alveoli of the canine and 

 first and second incisors are preserved. There is no trace of a 

 first incisor and there probably was none. The inner border of 

 the alveolus of i% is only about 1J millimeters from the sym- 

 physis. Separated by a still narrower ridge of bone is the 

 alveolus of t'5. One millimeter back of this is the three-sided 

 canine alveolus with its rounded angles. The posterior side 

 was the broadest and is close to pm 1. The canine was much 

 smaller than the first premolar. The first premolar is set 

 diagonally in the jaw. In cross-section it is nearly lenticular 

 but the anterior inner side is concave, while the greater inner 

 convexity is farther back than the outer one. Its transverse to 

 its antero-posterior diameter is as 11 to 17. Its anterior and 

 posterior edges are thin and sharp, and, though the tip is 

 broken off it evidently ended in a sharp point. Pm 2 is thin, 

 compressed and trenchant and like the first is inserted diago- 

 nally but with two roots. It is almost unworn. The highest 

 point and the convexity that descends from it are in the 

 median line, but the posterior slope is steeper and longer. As 

 seen from above the crest is sigmoid. In front of the highest 

 point there is a hint of the anterior inner lobe that is quite 

 prominent in pms 3 and 1±. Back of this is a small groove. 

 On the posterior inner side of the tooth is a slight concavity, 



