Peterson: The Osteology of Promerycochcerus. 207 



the fore limb. 



The more delicate character of the axial skeleton, when compared 

 with Promerycochcerus carrikeri, is reflected in the appendicular parts. 



The Scapula. — An imperfect specimen, showing the glenoid cavity, 

 the spine, and a portion of the blade of the left scapula is preserved. 

 The glenoid cavity indicates a more direct antero-posterior articulation 

 with the head of the humerus than is the case in P. carrikeri. The 

 spine is not so high and the metacromion tubercle was undoubtedly 

 less developed, while the acromion apparently had about the same 

 proportions as in the latter species. The neck is more constricted and 

 the glenoid border is more prominent, so that the postscapular fossa 

 was perhaps deeper than in P. carrikeri. 



The Humerus. — The proximal end and the greater part of the shaft 

 of the humerus are at hand. The head is quite hemispherical, but 

 has not the antero-posterior diameter or the robustness which obtain 

 in P. carrikeri. The great trochanter is apparently as heavy and the 

 bicipital groove is wider and deeper than in the latter species. At the 

 proximal end the shaft has received considerable lateral crushing, so 

 that the antero-posterior diameter appears greater than it really was. 

 The deltoid ridge is prominent and extends somewhat lower down on 

 the shaft than in P. carrikeri; otherwise the humerus is similar to 

 the earlier species so far as the material at hand enables us to judge. 

 The distal trochlea of No. 1232, which is preserved, is apparently as 

 oblique as in P. carrikeri. The anconeal fossa is broad and low. No 

 supratrochlear foramen can be detected. 



The Radius and Ulna. — Unfortunately the radius and ulna of the 

 type are not represented. In Nos. 1232 and 12320, however, these 

 parts, especially the radius, are fairly well preserved, and again show 

 the characteristically broad shaft which is seen in P. carrikeri. In 

 the fully adult stage this broadening of the radius is especially notice- 

 able, the external border of the shaft broadening out (especially 

 on the distal half) into a sharp interosseous ridge, instead of being 

 rounded as in Merycoidodon. The distal end is transversely expanded. 

 There is a deep groove on the ulnar border of the scaphoid facet, and 

 a wide, deep groove on the positerior margin between the scaphoid and 

 lunar facets. In No. 1232c both radii are preserved and show more 

 rounded shafts which may be due partly to crushing, perhaps also to 

 immaturity. 



The ulna differs little from that of P. carrikeri, except in being less 

 robust. 



