Douglass : Rhinoceroses from North Dakota and Montana 259 



A. montanus. A. ceratorhinus. 



mm. mm. 



LengthofP 1 27 26.5 



Widthof" 20 22 



LengthofP 2 3 6 35 



Widthof " 40 43 



LengthofP 3 4* 42 



Widthof " 53 5 6 



LengthofP 4 40 46 



Widthof " 58 5 8 



LengthofM 1 53 5° 



Widthof'' 63 55 



LengthofM 2 60 52 



Widthof " 62 58.5 



LengthofM 3 44 45 



Widthof " '. 5 6 53 



Comparison with Aphelops Megalodvs. 



A. montanus agrees in having the smooth elongated nasals, which are 

 devoid of horn-rugosities, and in the comparatively brachyodont teeth, 

 but it is a more dolichocephalic type, has a lower occiput, more slender 

 zygomatic arches, and a broader roof to the brain-case. 



Our knowledge of Miocene rhinosceroses is still too incomplete to 

 allow us to arrange them all under their proper generic names ; but 

 as A. megalodus is the type of Aphelops, the present series which 

 resembles it in so many particulars, should, for the present, be assigned 

 to that genus, though the resemblance may not be due to a very close 

 relationship. 



This species, but for the fact that it has no horn-rugosities on the 

 nasals, would, with Aphelops ceratorhinus, come under Professor Os- 

 born's definition of the third phylum of Miocene rhinoceroses. This 

 phylum, according to Professor Osborn, 1 is distinguished by decidedly 

 long limbs and feet, long skull, brachyodont teeth, and flattened pointed 

 nasals with small terminal horn-rugosities. It is barely possible that 

 the type of Aphelops montanus is a female and the male possessed 

 horns, though I do not think it probable. 



1 " New Miocene Rhinosceroses," Bulletin of the American Museum of Natural 

 History, Vol. XX, 1 904, p. 324. 



