1919] Merriam : Tertiary Mammalian Faunas of Mohave Desert 473 



and Gidley. 30 This species seems very near II. affinis, but is possibly 

 to be referred to H. nevadensis from an adjacent area. Were it not 

 that the milk dentition of both H. affinis and H. nevadensis are known, 

 it would be difficult to find means of separating the Nevada species 

 from H. affinis. 



28 



Fig. 28. Hypohippus, near affinis Leidy. M t and M 2 , no. 21215, natural size. 

 Barstow Miocene, Mohave Desert, California. 



A fragmentary upper molar, no. 21214, shows no characters more 

 than that it is a large species of Hypohippus. 



Measurements of no. 21215 



M 1; approximate anteroposterior diameter 28.2 mm. 



M„ greatest transverse diameter 20 



M 2 , anteroposterior diameter 29.5 



M 2 , greatest transverse diameter 17.4 



M 2 , height of crown at middle of occlusal face 19.5 



A number of phalanges of digit three, the distal end of a meta- 

 podial, several astragali, and a calcaneum from the Barstow collections 

 apparently represent Hypohippus. 



The phalanges (figs. 29 and 30) are larger and relatively much 

 wider or flatter than those of members of the Merychippus group. 

 In the proximal phalanges of the third digit, the median groove for 

 the distal keel of the metapodial is limited to the posterior region of 

 the articular face. 



30 Matthew, W. D., and Gidley, J. W., Bull. Am. Mus. Nat. Hist., vol. 22, 

 p. 135, fig. 1, 1906. 



