Vol. 6] Merriam: Virgin Valley and Thousand Creek 



293 



circumstances one does not seem justified in arbitrarily referring 

 it to /. alexandrae, as that form distinctly differs in several 



Figs. 73a and 73b. Ilingoeeros schisoceras, n. sp. Two views of the 

 horn. No. 11893, natural size. Thousand Creek Beds, Thousand Creek, 

 Nevada. Fig. 73a, posterior side; fig. 73b, inner or medial side. 



characters. In /. alexandrae the spiral ridge which has its origin 

 on the postero-superior region of the orbit, arises anterior to 

 the postorbital process of the frontal. In this form the ridge 

 arising over the orbit is evidently continuous with the postorbital 

 process. In /. alexandrae the horn is almost circular in cross- 

 section ; in this specimen the section is much flattened. Such 

 fragments of horn-cores of I. alexandrae as are available indicate 

 that the horns were considerably elongated, and round in section 

 some distance above the base, having therefore quite a different 

 character from those of this form. 



For the present, one seems warranted in separating the type 

 represented by specimen 11893 as a species distinct from /. ale.r- 



