530 THE MAMMALIA OF THE UINTA FORMATION. 



Fore limh (Figs. 4, 4a). The distal portion of the humerus shows an extensive 

 trochlea and deep anconeal pit, but no perforation. The proximal portion of the 

 radius entirely conceals the ulna ; the shaft is arched forward, strongly convex in 

 front ; the ulna descends along the flattened posterior surface and appears at the 

 side in the lower third of the shaft. The ulna has a small pisiform and narrow unci- 

 form facet. The chai'aeteristics of the carpus are fully described elsewhere and 

 well shown in the figures. The third metacarpal does not show the increased size 

 we should have anticiiJated in this genus, but would probably be relatively much 

 larger in an adult individual. The fifth metacarpal is about three-fourths the length 

 of the second and fourth. The phalanges are rather short and stout. The ungual 

 phalanges spread distally. The raetapodial keels are very prominent on the posterior 

 face. 



Hind limh. The tibial shaft is preserved, but is not characteristic. The tarsal 

 characters (Fig. 5) agree closely with those of Hyracotlierium, and are fully described 

 elsewhere. The astragalus has a very deep groove, narrow navicular facet, narrow 

 cuboidal contact, and three distinct calcaneal facets. The ealcaneum has a distinct 

 fibula facet and rather short stout tuber; the sustentaculum is very narrow. The 

 third metatarsal is very dee]3 and much stouter than the second and fourth, which are 

 strongly rotated backwards. The second metatarsal apparently articulates laterally 

 with the ectocuneiform. 



Taken altogether E^jihippus preserves more of the primitive characteristics of 

 Ilyracotherimn than we should have anticii^ated. These are especially seen in the 

 caipus. The tarsus shows more marked reduction of the lateral members. The 

 fibula is probably still complete. 



