XIV. RHINOCEROSES FROM THE OLIGOCENE AND 



MIOCENE DEPOSITS OF NORTH DAKOTA 



AND MONTANA. 



By Earl Douglass. 

 (Plates LXIII-LXIV.) 



Aphelops montanus sp. nov. 

 (Plate LXIII.) 



(Type No. 1569, Carnegie Museum Catalogue of Vertebrate Fossils. ) 



The type consists of a skull with the mandible, the two femora, 

 parts of a humerus, and other fragments of the skeleton. It came 

 from the Flint Creek (Upper Miocene) beds on the west side of the 

 Flint Creek valley, near New Chicago, Granite County, Montana. 

 It was collected by Professor Fred D. Smith and Earl Douglass in 

 1899, but it was not fully cleared from the matrix and its characters 

 determined until the summer of 1906. 



The following are some of the distinguishing characters of the 

 type: 



Skull long {^dolichocephalic') ; supraorbital region not broad ; nasals 

 long and tapering, not laterally cot?ipressed and not possessing horn- 

 rugosities ; posttympanic rounded, not wing-like as in Aphelops cera- 

 torhinus ; teeth brachyodont or brachyhypsodont ; number of premolars 

 complete (4) / all the upper cheek teeth except P x having crotchets, and 

 all except M 1 and Af 2 with antecrotchets ; limbs long and slender for so 

 large a rhinoceros. 



The skull of this species appears to be similar in form to that of 

 Aphelops ceratorhinus, though the cranium of the type of the latter is 

 not complete. The posterior upper portion of the skull of the type 

 of Aphelops montanus is crushed, but the upper contour was evidently 

 straighter than that of most of the American Miocene rhinoceroses 

 which have been described. The nasals are smooth, moderately long, 

 and evenly narrowed. They show no rugosities for the attachment 

 of horns. They are convex transversely on the upper surfaces, but 

 are not turned or rolled inward on the posterior portions of the outer 

 borders as in Aphelops ceratorhinus. The frontal plane was nearly 

 flat and there was no sagittal crest. The supratemporal ridges are 



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