74 Douglass — New Species of Merycochozrus in Montana. 



and another faint depression on the posterior outer surface. 

 On the posterior margin the descending ridge divides, forming 

 a little delta. In the third premolar these points are all more 

 prominent and the posterior internal concavity has become 

 quite a deep fossa bounded anteriorly by a prominent ridge. 

 In pm 4< the ridge has become a prominent element of the 

 tooth, being separated from the other part by a large posterior 

 fossa and the extension backward to meet it of the anterior 

 interior fossa. In this tooth the posterior concavity above 

 mentioned has become quite a deep trough and is more nearly 

 central. The unworn and nearly perfect condition of the pre- 

 molars gives an excellent opportunity for the study of their 

 development and their conditions before wear. If worn to the 

 same extent they would not differ so greatly from those of M. 

 latieeps. 



Merycochoerus altiramus, x ^. 



Measurements. 



M. 



Inferior dental series, length _ *1 63 



Molar-premolar series, length *1 58 



Molar series, length *098 



Premolar series, length ._. *060 



First lower premolar, length, greatest - *01 8 



First premolar, width, greatest 'Oil 



Second lower premolar, length *017 



Second lower premolar, width _ '008 



Second lower premolar, height ...-_. *013 



Third premolar, length '019 



Third premolar, height _. *0 1 5 



Fourth premolar, length '019 



