1919] Merriam: Tertiary Mammalian Faunas of Mohave Desert 503 



little more than 121°. In the smaller, more slender specimens there 

 appears a tendency toward a sharper angle than in the larger indi- 

 viduals. There are, however, small specimens in which the angle is 

 121°. It is probable that the smaller, more slender specimens of 

 metacarpal III with the more acute magnum-unciform angle represent 

 Merychippus summit. The larger, heavier specimens with the tendency 

 toward a wider angle presumably belong to M. intermontamis. In 

 metatarsal III the cuboid facet may be nearly transverse to the long 

 axis of shaft. It is commonly separated from the ectocuneiform facet 

 by a sharp ridge, but the larger part of the cuboid facet may be in- 

 clined away from the ectocuneiform facet only a few degrees. In 

 most specimens there appears to be no facet for the mesocuneiform. 

 In others, as in no. 21206, a distinct mesocuneiform articulation lies 

 almost in the plane of the ectocuneiform surface. 



The astragalus in all of the Merychippus specimens shows a deep, 

 narrow trochlear groove. The cuboid facet is well developed. The 

 astragali vary much in size as shown in figures 77 to 79, and may well 

 represent two or more specific types ranging from M. intermontamis 

 to M. suniani. 



The calcaneum, as shown in many specimens, seems not to differ 

 particularly from that in other Merychippus forms. 



Metacarpals II and IV are shown in a number of specimens 

 (figs. 66, 68, and 72). They are quite small in comparison with 

 metacarpal III. Compared with a cast of the foot of Protohippus 

 sejunctus kindly furnished by the American Museum they are not 

 relatively larger, and the fourth metacarpal seems somewhat smaller. 

 Very small lateral facets are present on both metacarpal II and IV. 

 Judging by the size of these lateral facets, the rudiments of meta- 

 carpals I and V must have been smaller than the small nodules seen 

 in P. sejunctus. 



The lateral metapodials of the hind foot (figs. 67 and 71) are, so 

 far as known, not larger and possibly smaller than in Protohippus 

 sejunctus. The complete form is not known but in at least one case, 

 as shown in figure 67, the distal region of the lateral metatarsal is 

 much reduced. 



All of the specimens representing distal ends of the lateral meta- 

 podials found in the Barstow are small and slender (fig. 74). The 

 lateral phalanges known are also small (figs. 76« and 765). All of the 

 evidence available shows that the lateral toes were small. 



