s 



Vol. 5] Mcrriam. — Strepskerine Antelopes from Nevada. 327 



This form differs from the typical Ilingoceros in the flattened 

 form of the horn core, which shows only the slightest tendency to 

 twist in the specimens available. The cross-section of the horn 

 cores is wedge-shaped, the anterior edge being narrower than the 

 posterior. The antero-external angle of the core rises above the 

 orbit in a line almost parallel with the long axis of the horn, 

 while in the typical specimens of Ilingoceros the anterior ridge 

 arising above the postero-superior region of the orbit swings 

 backward sharply across the long axis of the horn and quickly 

 twists around its base. 



The posterior aspect of the base of the horn core is also quite 

 different from that of the typical Ilingoceros, as a perfectly even 

 surface reaches up from the brain case and extends over the 

 posterior side of the horn core. In Ilingoceros this region is 

 crossed by the sharply twisting spiral ridges (fig. 1). 



SYSTEMATIC POSLTION OF ILINGOCEROS AND SPHENOPHALOS. 



The forms which have been included in the genus Ilingoceros 

 as described above seem to belong near the strepsicerine or 

 tragelaphine division of the antelope group. This sub-family 

 is known at the present day only in the African region, unless, 

 as some writers have held, the peculiar Boselaphus of India be 

 grouped with the African forms. It was represented by several 

 typical twisted-horned types in Europe and Asia in later Ter- 

 tiary time. No member of this most specialized group has here- 

 tofore been known in the Western Hemisphere. 



The type specimen of Ilingoceros resembles Protragelaphus 

 from the Pliocene of Europe and Asia in some characters, but 

 differs in the position and in the general character of the spiral 

 ridges, in the more erect position of the horns, and in the greater 

 width and flatness of the region between the bases of the horn 

 cores. 



The small specimen, no. 11893, tentatively referred to 

 Ilingoceros as group C, most nearly approaches Protragelaphus, 

 though it is by no means identical with it in form of horn core. 

 A fragmentary specimen, no. 11886, which has been considered as 

 probably representing a portion of a horn core of /. alexandrae 

 farther removed from the base than the upper end of the type 



