300 University of California Publications. [Geology 



Figs. 78a and 78b. Ilingoceros alexandrae Merriam. Fragment from 

 the distal region of horn. No. 11886, X %. Thousand Creek Beds, 

 Thousand Creek, Nevada. Fig. 78«, lateral view showing spiral; fig. 78b, 

 cross-section of horn. 



Fig. 79. Ilingoceros alexandrae Merriam. Posterior view of base of ' 

 left horn-core; a, spiral ridge arising over the postero-superior region of 

 the orbit; s, cross-section of horn-core. No. 11880, type specimen, natural 

 size. Thousand Creek Beds, Thousand Creek, Nevada. 



Fig. 80. Ilingoceros, form B. Posterior to postero-median view of basal 

 portion of right horn-core; a, anterior spiral ridge probably corresponding 

 to ridge a in figure 79; b, median or lateral spiral ridge; c, posterior spiral 

 ridge; s, cross-section of horn-core. No. 11892, natural size. Thousand 

 Creek Beds, Thousand Creek, Nevada. 



