TRANSACTIONS OF WAGNER 

 40 



UINTA SELENODONTS 



along the dorsal side of the latter. In Poebrotherium the calcaneum has 

 become somewhat more elongate, and has lost all but a trace of the great 

 external depression, as well as the small sulcus which runs between the 

 tuber and the sustentaculum. 



The cuboid is quite strikingly high, narrow, and thick, much resembling 

 that of Poebrotherium, but with its proximal facets differently proportioned. 

 In the White River form the astragalar facet is nearly as broad as that for 

 the calcaneum, while in the Uinta genus it is decidedly narrower; its dorsal 

 border is raised high above the calcaneal surface, giving a deeply notched 

 appearance to the cuboid. On the tibial side the bone is invaded by a sulcus, 

 which is shallower than in Poebrotherium, and which separates the navicular 

 facet into dorsal and plantar portions. The calcaneal facet overhangs some- 

 what, projecting beyond the fibular face of the cuboid; it is strongly convex 

 in the dorso-plantar direction and is quite complexly warped. The distal 

 end is almost entirely occupied by the large surface for the fourth meta- 

 tarsal, that for the fifth being very small. The plantar hook is long and 

 massive. 



The navicular is much shorter vertically than the cuboid, but quite as 

 broad and thick ; its proximal surface for the astragalus is hour-glass shaped, 

 and the ridge, with its dorsal projection, has a more external position than 

 in Poebrotherium ; the plantar hook, which in the latter is very much reduced, 

 is of moderate size and quite conspicuous ; it projects down over the ento- 

 cuneiform, but does not touch it. On the distal end of the navicular are the 

 usual three facets, of which that for the ecto-cuneiform is very much the 

 largest and occupies the whole breadth of the bone, while that for the ento- 

 cuneiform is pushed to the postero-internal angle. 



The cnto-cuneiform is flat and scale-like, quite high vertically and thick 

 antero-posteriorly, but very narrow transversely. It articulates with the 

 navicular by means of a narrow, convex facet, and has a long, oblique surface 

 which bears against the head of the second metatarsal, while its distal end is 

 closely applied to the plantar process from the head of the third. 



As in most artiodactyls, the meso- and ecto-cuneiforms are coossified, but 

 their limits may still be made out ; the middle cuneiform is much the smaller 

 of the two elements. The ecto-cuneiform is a large bone, almost as wide as the 

 cuboid, though its breadth is exceeded by its height, while the dorso-plantar 

 diameter is relatively hardly equal to half of the same dimension of the 

 navicular. Apparently, the ecto-cuneiform articulates only with the third 



