436 Douglass — New Species of Merycoclmrus in Montana. 



pressed longitudinally, is inserted diagonally by two roots, and 

 the posterior part overlaps pm 2 outwardly. Pm 2 is consid- 

 erably worn, but there is still a shallow oblique enamel lake 

 near the posterior margin. Pm 3 has a longitudinal lake with 

 two pits, near the inner border of the tooth. Pm 4- is like the 

 corresponding tooth in Merychyus elegans. The posterior 

 lobe on the last molar is not developed as in the Merycochmrus 

 proprins ; though the posterior horn of the posterior external 

 crescent is convex behind, it is narrower and extends much 

 more outward than in that species. The premolars and molars 

 are all longer than in M. proprius. This is due in part, but I 

 think not wholly, to less amount of wear. 



Inferior : There is no trace of a first incisor. The second 

 and third are laterally compressed at the roots, and are 2 mm 

 apart. They were about the size of upper incisors one and 

 two. 1 3 is set obliquely close to the canine on its anterior 

 inner side and a little more anteriorly than 1 2. The canine is 

 small, but a cross-section at the root is nearly the same in form 

 as the upper canine. Pm 1 is much larger than the lower 

 canine. It has a longitudinal groove on the outside of the 

 root. The crowns of the above teeth are not preserved. Ptn 2 

 is more oblique than in M. proprius or M. rusticus, being 

 closely crowded between pms 1 and 3. Pm 3 is porportion- 

 ally narrower posteriorly than in the former species, judging 

 by Leidy's figure. In pm 4- the posterior fossa is more 

 oblique, opening on the posterior inner angle instead of on the 

 posterior border. 



Measurements. 



Skull. 



v ... 



Length of skull from incisive border to posterior of occi 



pital condyles 



Length from incisive border to back of pterygoids 



Length from incisive border to front of otic bullae 



Width of skull at glenoid articulation 



Width at middle of last molars 



Width at third premolars 



Width at canines .. 



Width of palate between last molars 



Distance from anterior tips of nasals to incisive border, 



measured in a straight line 



From tips of nasals to crest of inion, about *150 to 



Distance from front of orbit to incisive border 



From front of orbit to back of occiput 



Diameter of orbit, antero-posterior 



Diameter of orbit, vertical 



M. 



245 

 185 

 203 

 200 

 180 

 080 

 057 

 063 



166 

 160 

 135 

 150 



038 

 045 



