Douglass : Vertebrates from Montana Tertiary 



183 



greater angle than in Arctomys monax. The most peculiar character- 

 istic is the presence of two chambers opening posteriorly between the 

 posterior nares and the posterior portion of the palate. I have not 

 observed this in any other animal. 



Paliearctotnys moutaiiiis is the type of the genus. 



Pal.earctomvs montanus sp. nov. 

 No. 740. Fig. 23. 

 This species is represented by a large part of a skeleton found in 

 the same beds as P. macrorhinus. The skull is longer in the pres- 

 ent species. The upper incisors have more longitudinal ridges on the 

 anterior faces ; the transverse dmeiater is somewhat less and teeth are 



Fig. 23. Pahrarctouiys montanus (No. 740). Lower Madison Valley. Skull 

 and mandible. Natural size. 



longer, /. e., they project farther from the jaws. The skull does not 

 differ greatly from that q{ Arctoviys monax so far as shown except in 

 what, for convenience, I will call the post-palatine cavities, and in the 

 size of the muzzle. The incisors are very much larger than in that 

 species. Not all of the skull is preserved. 



The mandible resembles that of Arctomys, but is very much more 

 robust. This is especially noticeable in the anterior part, where it is 



