Douglass — New Species of Merycochmrus in Montana. 81 



Merycochoerus f obliquidens f 



In the collection from the Madison Lake beds are two por- 

 tions of mandibles of a smaller animal than any of the preced- 

 ing. One is part of a right ramus containing only one perfect 

 tooth — the first molar. It seems to be much like the one 

 described by Cope as M. obliquidens. The ramus is small, 

 narrow and thick. JPm 1 as indicated by the large abrupt bot- 

 tom of the alveolus was robust. Pm% was placed diagonally 

 between pms 1 and 3 as in M. com-pressidens, only more trans- 

 versely as the alveoli are nearly at right angles to the long axis 

 of the jaw. Evidently pm3 was also inserted obliquely, as the 

 anterior root is near the inner margin while the posterior one 

 invades the outer. Pm ^ was in line with the long axis of the 

 jaw. In the other specimen 

 the fourth temporary premolar 

 is preserved. It has three lobes 

 of which the posterior is slightly 

 the larger. Ml has a high, 

 prismatic crown. All the pre- 

 molars were large. The men- 

 tal foramen and posterior 

 of symphyseal suture occupy 

 nearly the same place as in 

 Cope's M. obliquidens. It is 

 very doubtful whether this 

 belongs to the genus Mery- 

 cochoerus. 



Merycochoerus obliquidens ?, x %. 

 Last premolar from another speci- 



Measurements. 



From posterior of pm 1 to anterior of m 1 



Length of pm 2 at alveolar border 



Shortest distance between pm 1 and pm 3 



Length of pm 3 alveolar measurement 



Length of pm 4 



Length of ml 



Width of ml 



Height of crown of m 1 outside - - 



Depth of ramus under pm 2 about 



Depth of ramus under ml. 



M. 

 •0575 



■on 



•0055 



•016 



•0217 



•019 



•015 



•015 



•032 



•029 



As the above described species are represented by portions 

 of mandibles and the most striking differences are in the 

 depths of the horizontal rami, I give below a table which wilL 

 show the variation in this respect : 



Am. Jour. Sci. -Fourth Series, Vol XI, No. 1.— January, 1901. 

 6 



