TRANSACTIONS OF WAGNER 

 7° 



UINTA SELENODONTS 



the artiodactyls, and bears narrow, concave facets for the ulna and pyramidal. 

 The body of the bone is compressed, of moderate vertical depth, and so curved 

 that it presents a convexity towards the ulnar side, while the distal end is 

 slightly thickened. In the other Uinta genera above mentioned the pisiform 

 is much larger ; it is not transversely extended at the proximal end, and is 

 much more thickened and club-shaped at the distal end. In Protorcodoii this 

 bone is much broader than in Camelomeryx. The pisiform of Leptomeryx is, 

 unfortunately, not known, which prevents a comparison with that genus. 



The trapezium is not preserved in connection with the specimen, but no 

 reason is apparent to doubt that it was originally present, as is indicated by 

 a small facet upon the radial side of the trapezoid. As in all of the Uinta 

 selenodonts whose carpal structure is known, the trapezoid is distinct from 

 the magnum. Leptomeryx is quite exceptional as a member of the Tylopoda 

 in having these elements united; the union does not occur in Protoceras or 

 Poebrotherium, or in the existing camels and llamas, though it is usual in the 

 Pecora and Tragulina. In Camelomeryx the trapezoid is quite a small bone, 

 though relatively high in the proximo-distal diameter, exceeding in this re- 

 spect the corresponding element of Leptomeryx. The proximal end is rounded 

 and convex, fitting into the concave facet upon the distal end of the scaphoid. 

 On the radial side is a small facet which was doubtless destined for articulation 

 with the missing trapezium. Connection with the magnum is maintained by 

 two facets, proximal and distal. The distal end, so far as may be judged from 

 the specimen, appears to bear an almost plane facet for the second metacarpal. 



The magnum is still quite small proportionately, for the obvious reason 

 that the third metacarpal is not greatly enlarged nor the lateral digits much 

 reduced. The proximal end is unequally divided between the surfaces for the 

 scaphoid and lunar, which meet at a very open angle; the former is some- 

 what the larger and more completely proximal in position, while the lunar 

 facet is more oblique. A very small facet occurs at the disto- internal angle 

 for the head of the second metacarpal, which preserves its primitive connec- 

 tion with the magnum. Nearly all of the distal end is taken up by the large 

 facet for mc. iii., which is only slightly convex. It is impossible to say defi- 

 nitely whether there is any dorsal contact between the magnum and the 

 unciform ; if so, it must have been very small, owing to the distal extension 

 of the beak of the lunar. In Leptomeryx the magnum is much lower proximo- 

 distally than in the present genus, and has so shifted that dorsally it lies alto- 

 gether beneath the scaphoid, as is also the case in Protoreodon. In Protylopus 



