No. 3.] OSTEOLOGY OF MESOHIPPUS AND LEPTOMERYX. 353 



humerus is not so deep in Leptomeryx. The shaft is flattened 

 and nearly straight. The distal end is much less expanded than 

 in Tragiilus. The ulna is much reduced and has a very slender 

 shaft ; the olecranon is higher than in the modern genus, but of 

 less antero-posterior diameter. 



The manus, which has been described by Cope (No. 10), is 

 very traguline in character, both in general appearance and in 

 details of structure. The scaphoid is not preserved in any of 

 the specimens, nor is the trapezium ; not improb- 

 ably the latter was altogether wanting. The prox- 

 imal end of the lunar is shaped very much as in 

 the Pecora, but the distal end is very different, in 

 that the lunar rests almost wholly upon the unci- 

 form and has only a lateral contact with the mag- 

 num — a traguline character upon which Cope has 

 laid much stress. The cuneiform is very small, 

 and is not in contact with the radius ; its ulnar sur- 

 face is saddle-shaped and extends well down upon 

 the external surface of the bone. The trapezoid 

 and magnum have coalesced ; the compound bone 

 is low, rising slightly behind; it is supported almost 

 exclusively by the scaphoid. Distally it presents 

 facets for the second and third metacarpals. The 

 unciform is the largest bone in the carpus, but is 

 not so high proportionately as in Tragiilus. 



The metacarpus consists of four digits, none of which shows 

 any tendency to coalesce with another. The lateral digits are 

 very slender, though not so much so as in the chevrotains ; the 

 median digits are of about the same relative length, but de- 

 cidedly more slender. Metacarpal II. articulates with a down- 

 ward projection from the trapezoid element of the trapezo-mag- 

 num. Metacarpal III. articulates medially with the side of this 

 same projection, proximally with the magnum, and laterally with 

 the unciform, sending out a process which overlaps the head 

 of No. IV. Metacarpals IV. and V. articulate only with the 

 unciform. The manus is thus of the "adaptive type." The 

 carinae of the metacarpals are entirely confined to the palmar 

 surface. 



The phalanges of the manus do not differ appreciably from 

 those of Tragiilus, 



Fig. E.— Left 

 manus of Lepto- 

 meryx Evansi; 

 natural size. 

 Cope collection. 



