1915] Merriam: New Horses from the Miocene and Pliocene 



55 



require at least tentative recognition in the classification. It is pos- 

 sible that fuller collections may ultimately show an intergradation 

 between this form and H. mohavensc. 



Measurements of No. 21311 



P 2 , anteroposterior diameter 



29.9 mm. 



Pj, 



anteroposterior diameter .... 



28.4 mm 



P 2 , transverse diameter 



20.2 



P 2 , 



greatest transverse diameter 



12. 



P 3 , anteroposterior diameter 



27.4 



Ps, 



anteroposterior diameter .... 



27. 



P 3 , transverse diameter 



23.2 



P«, 



greatest transverse diameter 



13.7 



P 4 , anteroposterior diameter 



24.8 



P t , 



anteroposterior diameter .... 



27.4 



P 4 , transverse diameter 



21.5 



P t , 



greatest transverse diameter 



13. 



P 4 , height of mesostyle 



45.5 



P«, 



height of protoeonid 



51. 



M 1 , anteroposterior diameter 



24.5 



M„ 



anteroposterior diameter.... 



25.8 



M 1 , transverse diameter 



22.6 



M„ 



greatest transverse diameter 



11.4 



M 2 , anteroposterior diameter 



24. 



M,, 



anteroposterior diameter.... 



27.3 



M 2 , transverse diameter 



20.4 



M 2 , 



greatest transverse diameter 



10.8 



M 2 , height of mesostvle 



41. 



M 2 , 



height of protoeonid 



44.4 



M 3 , anteroposterior diameter 



21. 



M s , 



anteroposterior diameter.... 



25. 



M 3 , transverse diameter 



18. 



M 3 , 



greatest transverse diameter 



10.4 



PLIOHIPPUS FAIRBANKSI, n. sp. 



Type specimen, a large unworn upper cheek-tooth P 4 ?, no. 19789, from the 

 Ricardo Pliocene, near Rieardo Postoffice, California. 



The type specimen of P. fairbanksi represents a protohippine form differing 

 considerably from PUohippus tantalus of the Ricardo Pliocene. The crown is a 

 little more strongly curved and the styles are heavier. The fossettes are nar- 



Pigs. 8a to 8c. PUohippus fairbanksi , n. sp. P 1 ?, type specimen, no. 19789, 

 natural size. From the Ricardo Pliocene near Ricardo Postoffice, Mohave Desert, 

 California. Fig. 8«, occlusal view; fig. 8b, section at base of upper third of 

 crown; fig. 8c, posterior view. 



