92 BULLETIN OF THE 



AFHELOPS, Cope. 



The generic characters of Aphelops have been given by Cope as follows. Den- 

 tition, I. -y 1 , C. x> P. -^ 3 , M. § ; post-glenoid and post-tympanic processes 

 in contact but not co-ossitied ; digits, 3-3 ; nasals hornless. To these charac- 

 ters may be added : magnum not supporting lunar anteriorly ; absence of the 

 'crista' and invariable presence of the more or less strongly developed ' crochet ' 

 and ' anticrochet ' in the superior molars. 



The specific nomenclature of Aphelops is in confusion. The type of A. (Rhi- 

 noceros) crassus, Leidy, 1 is a last upper, molar, which is closely similar to that of 

 A. megalodus ; the characters of the milk molar associated with this type cannot 

 be used in definition. 2 The penultimate upper molar, the type of A. raeridi- 

 anus, Leidy, 1 corresponds in the development of the two ' crochets ' to the same 

 tooth in A.fossiger, Cope, but the posterior 'fossette ' is not enclosed by the strong 

 cingulum as in the latter species. A. (Aceratfierium) acutum, Marsh, is identical 

 with A. fossiger. A. malacorhinm, Cope, resembles A. meridianus in the open 

 posterior fossette and the development of the ' crochets.' It is impossible, how- 

 ever, to clear up this synonymy without bringing the original types together 

 for comparison. General characteristics of all these types are the invariable 

 development of the ' crochet,' absence of the ' crista,' usual development of the 

 'anticrochet.' The specific names proposed by Cope are here adopted because 

 they are established upon a very complete knowledge of the skull as well as 

 of the teeth. 



Aphelops fossiger, Cope. 



Dentition : I. T , C. T , P. f, M. §. First premolar simple, conical, sometimes 

 absent ; nasals not overhanging premaxillaries ; foramen lacerum medium 

 confluent with foramen ovale ; occiput broad and low ; limbs short and bulky ; 

 molars with well developed 'crochet' and 'anticrochet.' 



In the figure given by Marsh (Am. Journ. Sci., Oct., 1887, p. 3) and by Cope 

 (Am. Nat., Dec, 1879, p. 771 c), the third and fourth premolars have both the 

 ' crochet ' and ' anticrochet.' There is some ground for the supposition that the 

 skull here described belongs to a different species, since the 'anticrochet' is not 

 developed in the premolars. This reference is therefore provisional. 



This is apparently the only species which is represented in this collection. 

 All the specimens are from Kansas, and include several skulls and well pre- 

 served bones from all parts of the skeleton, enabling us to give a complete 

 description and restoration of the animal. 



1 See Ext. Marrm. Fauna, Dak , p. 228. 



2 Cope has nevertheless employed the ' cristas ' developed in this milk molar in 

 his definition of A. crassus. "On the Extinct Species of Rhinoceriidae of North 

 America," etc., Hull. U. S. Geol. Survey, Vol. V. No. 2, p. 237. 



