TRANSACTIONS OF WAGNER 

 1 06 



UINTA SELENODONTS 



and none for the ecto-cuneiform, which has become extremely short proximo- 

 distally. The distal end of the cuboid is wider and thicker than in Protoreo- 

 don, and the great hook-like projection from the plantar face is shorter, but 

 heavier; the facet for the fourth metatarsal is wider, and that for the fifth 

 larger and more in the same plane with the fourth than is the case in Protoreo- 

 don. The same is true of Agriochcerus, but here the surface for mt. iv. is 

 relatively more extended in the dorso-plantar dimension. 



The navicular is higher and thicker than in Protoreodon, though this 

 appearance of greater height is partly deceptive and due to the elevation of 

 the dorsal border of the proximal end. The bone is shaped very much as in 

 the last-named genus, and the only obvious difference is the greater size of 

 the plantar hook in Protagriochcems. In Agriochcerus the navicular has be- 

 come much lower and wider, the increase in breadth being principally due to 

 the widening of the internal portion of the facet for the astragalus, while on 

 the distal face the surface for the compound cuneiform is more extended 

 transversely, but less planto-dorsally, and the facet for the ento-cuneiform is 

 smaller and more sessile. 



When the cuboid and navicular are placed in their natural position with 

 reference to each other, it may be readily seen that the cuneiforms were much 

 higher in proportion to their breadth than is the case in Agriochcerus. Doubt- 

 less the meso- and ecto-cuneiforms were coossified, as in all the known oreo- 

 donts and agriochcerids. 



A second phalanx of one of the median pair of digits is relatively longer 

 and more slender than the corresponding bone of Agrioc/tcerus ; the proximal 

 end is less distinctly divided into two facets by the less elevated intercondylar 

 ridge, and the median dorsal beak is much less prominently developed. The 

 shaft is relatively longer, narrower, and thinner, and tapers more towards the 

 distal end. The distal trochlea is more like that of Agriochcerus, being reflected 

 far over upon the dorsal face of the phalanx and distinctly cleft along the median 

 line; it differs from that of the White River genus in being relatively narrower. 

 The second phalanx of the pes in Oreodon is very similar indeed to that of 

 Protagriochccrus, but with a few differences which may ultimately prove to be 

 significant. Thus the bone is relatively shorter and heavier than in the Uinta 

 form; the distal trochlea is not reflected quite so far over upon the dorsal side, 

 and its plantar portion is somewhat less distinctly divided by the median cleft. 

 In Protoreodon this phalanx is similar, but longer and thinner. Most unfortu- 

 nately, no unguals have been found in connection with Protagriochcems, but 



