1896.] ibO [Farr. 



femur, tibia and almost complete hind foot, and enables me to give some 

 further characters of the species. M. copei differs from M. hairdi in the 

 following respects : (1) The lateral metapodials curve outwardly quite 

 sharply distally and the toes were thus more spreading than in M. bairdi 

 (see Fig. 5). (2) The meso-cuneiform is proportionately less deep than 

 the ecto-cuneiform than in M. bairdi. (3) The carina or median keel of 

 the distal end of metatarsal iii, which in the smaller species is almost 

 entirely confined to the plantar surface of the bone, in M. copei extends 

 far up in the dorsal surftice of the distal end of the bone. (4) The lat- 

 eral metapodials are comparatively shorter than the median metapodial, 

 so much so that the ungual phalanges could scarcely have been func- 

 tional at all, and this form had progressed farther toward monodactylism 

 than any other known form from the White River. (5) The combined 

 depth of the navicular and ecto-cuneiform was greater than in M. bairdi, 

 and greatly exceeded that of M. interniedius. (6) The cuboid did not 

 extend below the level of the ecto-cuneiform. Metatarsal iii was borne 

 by the latter alone and did not extend over on the cuboid, so that ante- 

 riorly there is no contact of these two bones either lateral or distal as in 

 both the other species. 



The tibia is about one and one-half times as long as that of M. bairdi, 

 and is proportionately much stouter. 



The shaft is very long, even longer than that of the John Day species, 

 but is more slender, and seen from the side it presents the characteristic 

 sigmoid curve. Tlie cnemial crest is very high, curves slightlj^ outward 

 and has the usual tendinal sulcus on its outer border. It extends farther 

 down on the shaft than in M. bairdi. The proximal surface is very much 

 more rugose than in the latter. The femoral facets slope downward and 

 backward at quite an angle. The outer facet is convex antero-pos- 

 teriorly and concave transversely. The inner facet is concave antero- 

 posteriorly and convex transversely. The distal end of tibia is turned 

 slightly outward. The distal end of tibia and fibula together are pro- 

 portionately wider than those of M. bairdi. The facets for the trochlear 

 surface of astragalus are deeply incised, are oblique in position and are 

 separated by a high intertrochlear ridge. 



The proximal end of the fibula is not presei'ved, but the very large 

 distal end and a portion of the shaft persists. Rugosities on the outer 

 border of tibia indicate that it was complete and closely applied to the 

 latter. The portion of the shaft preserved is very much reduced. The 

 expanded distal end forms the external malleolus and bears the two 

 usual facets. 



The tarsus presents striking differences from that of M. bairdi, and 

 can best be described by instituting a comparison between it and the 

 latter. 



The calcaneum is stouter and more massive, but has about the same 

 relative proportions as in M. bairdi. The tuber calcis is large and rugose 

 for the insertion of the tendo Achillis. The tuberosity is quite high 



