FREE INSTITUTE OF SCIENCE 



59 



UINTA SELENODONTS 



zoid and magnum, but is too much injured to show whether or not a trapezium 

 facet was originally present. The lunar is narrow, but quite high vertically 

 and rests almost equally upon the magnum and unciform, a very marked 

 difference from all known oreodonts ; the junction of the two facets is at 

 such an angle as to make a sharp distal beak. Of the pyramidal only a 

 shapeless fragment remains. The trapezoid appears to be distinct from the 

 magnum, though this point is somewhat uncertain; it is very small. The 

 magnum is rather narrow, but quite high ; its proximal end is divided sym- 

 metrically between the facets for the scaphoid and lunar, and distally it 

 appears to have a very limited contact with the second metacarpal. Of the 

 unciform it can be said only that it is broad and high, and carries a stout 

 hook upon the plantar face. The pisiform is short and stout, laterally com- 

 pressed, but deep vertically ; at the free end it is moderately thickened and 

 incurved towards the radial side; its shape is very much as in Protylopus, but 

 somewhat shorter and heavier. 



The metacarpus consists of four functional elements and has a general 

 resemblance to that of Protylopus, but differs from it in the more uniform 

 size of the bones, the median pair being less enlarged and the lateral pair 

 less reduced. 



Metacarpal ii. is long, straight, and quite slender, though decidedly stouter 

 than in Protylopus ; the proximal end is enlarged in the dorso-palmar diameter, 

 but not transversely ; the head articulates by means of a concave facet with the 

 trapezoid and sends out a short process towards the ulnar side, which probably 

 reaches the magnum, though the state of preservation of the bones is not 

 sufficiently good to make this point clear. Below the proximal end the shaft 

 is of nearly uniform size and quite straight, though with a slight curvature 

 towards the ulnar side. The distal trochlea is low and small. 



Metacarpal iii. is considerably longer than mc. ii. and distinctly heavier, 

 though as compared with mc. iii. in either Protylopus or Lcptomcryx it is still 

 slender. The head has the usual transversely concave facet for the magnum, 

 and sends out a prominent process to meet the unciform, which process is 

 somewhat larger than in Protylopus, and beneath it the shaft is more excavated 

 for the head of mc. iv. than in the latter. The shaft is straight and narrow, 

 but rather thick, while the distal trochlea is narrow and very low. As always 

 in these early selenodonts, the carina is entirely plantar in position. 



Metacarpal iv. differs from mc. iii. only in the shape of the proximal end, 

 which has but a single carpal articulation, that with the unciform. 



