264 



University of California Publications. 



[Geology 



Figs. 34a and 34b. Merychippus, near isonesus (Cope). Inferior cheek 

 tooth. No. 11690, natural size. Virgin Valley Beds, Virgin Valley, 

 Nevada. Fig. 34a, outer side; fig. 34b, occlusal view. 



Fig. 35. PlioMppus (?) , sp. Inferior molar. No.' 19413, outer side, 

 natural size. Thousand Creek Beds, Thousand Creek, Nevada. 



Fig. 36. Equus(l) , sp. Inferior molar. No. 19414, outer side, natural 

 size. Thousand Creek Beds, Thousand Creek, Nevada. 



which were all represented by upper teeth. Taking into con- 

 sideration the variability of hypsodont molar teeth of horses, it 

 does not seem advisable to attempt a definite characterization 

 of the species of Merychippus from the Virgin Valley region 

 until some of the several forms present in this fauna are repre- 

 sented by more complete material than is now available. 



Teeth of the forms referred to M. isonesus (Cope) (figs. 30a, 

 306, 34a, and 346) are the most common remains of Equidae in 

 the Virgin Valley Beds. 



Occurence : Virgin Valley Beds at Virgin Valley and High 

 Rock Canon, Humboldt County, Nevada. 



MERYCHIPPUS, near SEVERSUS (Cope) 



A small form of Merychippus approximating the type of M. 

 seversus (Cope) appears rarely in the beds at Virgin Valley, and 



