TRANSACTIONS OF WAGNER 



UINTA SELENODONTS 



way it is clear that it is allied to the other Uinta selenodonts described in the 

 foregoing pages, and it is not at all impossible that Oromeryx may prove, when 

 better known, to be the forerunner of Hypertragitlus. Both genera are charac- 

 terized by simplicity of the premolar teeth, and both have very similar molars, 

 which in Oromeryx and less markedly in Hypertragubis are distinguished by 

 the narrowness of the posterior half of the crown and the consequent asym- 

 metry of form. In the character of the skull, limbs, and feet nothing is known 

 to forbid or render improbable the derivation here suggested. At the same 

 time it must be remembered that this is only a suggestion, and quite as good 

 reasons may be given for deriving Hypertragidus from Leptotragiibts. The 

 difficulty in deciding the question comes from our ignorance regarding much 

 of the structure of the two genera from the Uinta, and until these are better 

 known we shall not be able to determine with accuracy even the family or 

 famihes to which they should be referred, still less to indicate their successors 

 in the White River fauna. 



Family III. HOMACODONTID^. 



Bunomeryx Wortman. 



Bull. Amer. Mus. Nat. Hist. N. Y., x., p. 97. 



This exceedingly interesting form is not represented in the Princeton 

 collection, and I therefore have nothing to add to Wortman's account. One 

 of the most significant facts regarding Biinomeryx is the structure of its upper 

 molars, which strongly suggests, as Wortman has pointed out, that the postero- 

 internal crescent of the selenodont upper molar is not the hypocone, as has 

 hitherto been taken for granted, but the metaconule. This determination is of 

 the greatest interest as showing that the elements which make up the molar 

 crown may develop in different ways, and that cusps occupying similar positions 

 are not always homologous. The same fact has already been established with 

 regard to the premolars. It is confirmatory of Wortman's view that the Uinta 

 selenodonts almost all have more or less asymmetrical upper molars, due to 

 the fact that the anterior half of the crown is broader transversely than the 

 posterior half In Oromeryx, and especially in m-^ of that genus, this asym- 

 metry is most clearly shown, but it has almost entirely disappeared in the 

 White River genera. On Wortman's hypothesis the asymmetry seen in the 

 i:eeth of the earlier selenodonts is intelligible enough; it is simply due to the 

 fact that the metaconule has not yet grown to the full size of the protocone. 



