Vol. 5 1 )j ( rriam. — Strepsicerine Antelopes from Nevada. 



325 



A very small specimen, no. 11893 (fig. 6), shows a cross- 

 section of the horn core faintly suggesting that of the type of 

 Sphenophalos nevadamis described below. In cross-section at the 

 top the long diameter is a little more than twice the short 

 diameter. On this specimen two sharply marked ridges arise at 

 the base of the horn core, and come into positions diametrically 

 opposite each other a short distance above the base. They twist 

 about the core at a rate of about one complete turn in four 

 inches, or at nearly the same rate as in I. alexandrae. As yet 

 we have no definite evidence of a spiral twist of the ridges on 

 the horn core of the type of 8. nevadanus, though a slight turn 

 outward and backward from the upper region of the orbit is 

 suggested. This specimen differs from no. 11894 in that the ridge 

 a, which seems to rise just outside the superior openings of the 

 supraorbital foramina as in ridge a in the type of Ilingoceros, 

 appears to be continuous with the posterior angle of the post- 

 orbital process instead of just above it, and may correspond to 

 ridge b in no. 11892, form B. There is farther no suggestion in 

 no. 11894 of a second strong crest opposite ridge a as is shown 

 here. From specimen 11892, designated as group B of Ilin- 

 goceros, this form differs in that the two main crests are near 

 together with a narrow groove between them in group B, while 

 here the main ridges assume positions diametrically opposite 

 each other and the cross-section is narrow. 



Specimen 11893 may be referred to Ilingoceros tentatively, 

 and designated as form 0. 



SPHENOPHALOS- NEVADANUS, n. gen. and sp. 



Type specimen no. 11887, Univ. Gal. Col. Vert. Palae., from 

 late Tertiary beds near Thousand Creek in northern Humboldt 

 County, Nevada. 



Prontals not cavernous at the base of the horns. Horns 

 situated on the upper posterior region of the orbits, sloping back- 

 ward, slightly outward, and tilted upward at an angle between 

 twenty-five and thirty degrees from the plane of the frontals 

 above the orbits. Horn cores flattened in a plane extending 



1 (r4>rjv, wedge; </>aAos, horn on a Homeric helmet. 



