320 



University of California Publications. 



[Geology 



wide range of mammalian forms, of which a considerable per- 

 centage are new. Some of the most interesting material, par- 

 ticularly from the point of view of the student of geographic 

 range and origin of faunas, is that representing a number of 

 antelopes of the strepsicerine or twisted-horned type, known at 

 the present time only in Africa. No representatives of these 

 forms have been known heretofore from the Western Hemisphere, 

 though they were present in Eurasia in middle to late Cenozoic 

 time. 



Twelve specimens of horn cores were obtained in the beds at 

 Thousand Creek, including a number of cpiite different types. 

 The range of form may be due in part to variation in age or 

 possibly in sex, but cannot be attributed entirely to these factors. 

 There appear to be at least two species represented which 'evi- 

 dently belong to two quite distinct genera. 



ILINGOCEBOS 2 ALEXANDKAE, n. gen. and sp. 



Type specimen no. 11880, Univ. Calif. Col. Vert. Palae., from 

 late Tertiary beds near Thousand Creek in northern Humboldt 

 County, Nevada. The species is named in honor of Miss Annie 

 M. Alexander, through whose efforts the collections of Tertiary 

 mammals from northwestern Nevada have been obtained and 

 made available for scientific investigation. 



Frontals not cavernous at the base of the horn core. Horn 

 cores, situated upon the upper posterior region of the orbits, 

 sloping backward, slightly outward, and tilted upward at an 

 angle of approximately twenty-five degrees from the plane of 

 the frontals above the orbits. Horn cores tending to be circular 

 in cross-section excepting for the presence of two or more well- 

 developed spiral ridges. Principal spiral ridge arising above the 

 postero-superior region of the orbit and swinging backward 

 around the axis at the rate of about one turn in three and one- 

 half inches. Posterior to a strong groove behind the principal 

 ridge a second spiral elevation may be present, and a third may 

 be present in some specimens referred to this genus. Supraorbital 

 foramina present at the anterior side of the base of the horn 

 cores. 



'iXiyyos, a whirlwind; xepas, horn. 



