1919] Merriam: Tertiary Mammalian Faunas of Mohave Desert 571 



In two specimens representing metacarpal III (nos. 21202, fig. 194, 

 and 21203, fig. 193«, 193b) lateral elements are shown. In the prox- 

 imal articulation the large unciform facet on metacarpal III meets 

 the magnum facet at an angle ranging from 128° to 131°. The 

 magnum-unciform angle is from ten to twenty degrees wider than 

 that in the Barstow horses and seems uniformly to separate the 

 Ricardo forms from the less progressive Barstow species. Meta- 

 carpal II stands relatively higher at the proximal end than in 

 Equus, and the facet between magnum and metacarpal II is inclined 

 about twenty degrees away from a plane normal to the distal facet 

 of the magnum. 



If a rudimentary metacarpal I was present it was exceedingly 

 minute, as there is scarcely a suggestion of a face of contact on the 

 inner side of the proximal end of metacarpal II. Metacarpal IV is 

 represented for at least two-thirds of its length in specimen no. 21203. 

 The lateral side of the proximal end shows a distinct facet for a 

 metacarpal V. 



In a metatarsal III (no. 21198, figs. 203a-203cZ) the beveled 

 postero-lateral regions with large contact faces show that lateral 

 metatarsals II and IV extend as fairly large elements down almost 

 to the distal end of this element. A portion of the large metatarsal IV 

 is coossified with the shaft of metatarsal III near the middle of this 

 specimen. The median distal keel extends over the anterior portion 

 of the distal articular face as a clearly defined ridge, reaching quite 

 to its proximal border. The distal keel is more strongly marked in 

 this form than in any of the numerous specimens from the Barstow. 



On the proximal end of a metatarsal III (no. 21198, fig. 2036), 

 the cuboid facet is large, and is only slightly inclined away from the 

 plane of the ectocuneiform facet. There is a well marked facet for 

 the mesocuneiform showing but little more inclination away from the 

 plane of articulation of the metapodial and ectocuneiform than is 

 shown in the facet between cuboid and metapodial. The lunate 

 posterior portion of the articulation between metapodial and ecto- 

 cuneiform is separated from the larger anterior surface by a deeply 

 pitted area. 



A single metatarsal III, no. 21201 (fig. 200) represents a type 

 somewhat different from that seen in no. 21198. The shaft in speci- 

 men 21201 is more slender and evidently smaller. The proximal end 

 is relatively narrower anteroposteriorly. The facet for the mesocunei- 

 form is slightly larger and more nearly parallel with the plane of 

 the ectocuneiform facet. The posterior articulation with the ecto- 



