1919] Merriam : Tertiary Mammalian Faunas of Mohave Desert 563 



mined as P. fairbanksi. These less massive teeth, in which the meta- 

 conid-metastylid column is somewhat longer anteroposteriorly and the 

 inner gutter wider than in the larger form, are referred tentatively 

 to Pliohippus tantalus. Of the two lower dentitions referred to 

 P. tantalus, no. 21789 was found between the uppermost and the 

 second basalt flows 2y 2 miles north of Ricardo Post Office ; no. 21790 



Figs. 180 to 182. Pliohippus tantalus? (Merriam). Inferior cheek-teeth, 

 natural size. Fig. 180, P 2 to M 2 , no. 21789, occlusal view; fig. 181, P 4 , no. 21789, 

 outer view; fig. 182, M, and M ; , no. 21790, outer and occlusal views. Eicardo 

 Pliocene, Mohave Desert, California. 



was found by J. P. Buwalda about 500 feet below the lowest basalt 

 flow and 400 feet above the base of the Ricardo beds, two miles above 

 the mouth of Iron Canon. 



In no. 21789 (figs. 180, 181) the moderately worn tooth crowns 

 are long and heavily cemented. Compared with no. 21346, a large 

 Pliohippus specimen from a much higher situation in the Ricardo, 

 the crowns are relatively much narrower with approximately the 



