TRANSACTIONS OF WAGNER 

 74 



UINTA SELENODONTS 



The ulna and radius are long and slender and seem to be firmly coossi- 

 fied, though it is difficult to determine this point. At all events, they are very 

 closely approximated throughout their length and are anchylosed at points, 

 but, at the same time, their limits are clearly shown by deep grooves along 

 the line of junction. The radius is relatively well developed; its proximal end 

 is moderately widened, but thin and compressed antero-posteriorly, and in 

 shape resembles that of Lcpiomeryx. The humeral surface is divided into 

 two facets of unequal size, the internal one being considerably the larger; the 

 groove for the intercondylar ridge is shallow, but makes a distinct notch on 

 the dorsal border of the proximal end. The shaft is long and quite broad 

 transversely, with a well-marked curvature towards the anterior side. In 

 general proportions it is very different from the slender, cylindrical form 

 which is characteristic of the oreodonts and rather resembles that of Lepto- 

 meryx, but is of less uniform width than in the latter ; it is widest proximally, 

 gradually contracting towards the middle, whence it again expands towards 

 the distal end. The latter is moderately broad and thick, and displays a broad 

 and shallow sulcus for the extensor tendons upon its anterior face. The facets 

 for the scaphoid and lunar are of nearly equal size, though the former is 

 slightly the larger ; it is also reflected farther up upon the palmar face ; the 

 lunar face is simply concave. 



Despite its anchylosis with the radius, the ulna is quite stout and very 

 little reduced. The olecranon is so broken that its exact size and shape can- 

 not be determined, but it was evidently large and heavy. The sigmoid notch 

 is rather shallow, though the coronoid process is prominent, and the humeral 

 facet is almost confined to the inner side ; the external radial facet forms a 

 marked projection. The shaft is quite stout, especially its proximal third, 

 tapering steadily towards the distal end ; the inferior part is laterally com- 

 pressed and plate-like. The distal end is somewhat thickened, but its internal 

 side is deeply notched to receive a projection from the radius. The facet for 

 the pyramidal is small and saddle-shaped, and that for the pisiform, which is 

 quite small, is continuous with it. In Leptomeryx the ulna and radius are, in 

 general, much like those of the present genus, but they show no tendency to 

 anchylosis, though the shaft of the ulna is much more slender. 



Radius, length .... 0.067 

 " width of proximal end . .00S 

 " " of distal end . . .010 



MEASUREMENTS. 



Ulna, length ? 0.080 



" width of proximal end . . .006 



" of distal end . . .004 



