THE MAMMALIA OF THE DEEP RIVER BEDS. 175 



The fore limb is represented by a broken humerus, with the ulna, radius and 

 cannon-bone nearly complete. The length of the humerus cannot be determined, as 

 the proximal end is missing, but apparently it was about equal to that of Antilocapra. 

 On the other hand, the shaft is heavier, especially in the transverse dimension, than 

 in that animal and the deltoid ridge much more roughened and prominent and de- 

 scending farther. The anconeal fossa is deep, but notably small, and the supratroch- 

 lear fossa is shallower and less distinctly marked than in the modern genus. The 

 trochlea is wider and the intercondylar ridge even more prominent and has a more 

 oblique course, downward and inward ; the external condyle for the radius is rela- 

 tively somewhat broader ; the internal epicondyle is distinctly larger. The distal 

 end of the humerus is much like that of Dicroceros in the less uniform vertical height 

 of the trochlea, which tapers towards the outer side, and in the more external posi- 

 tion of the intercondylar ridge (ef. Filhol, No. 13, PI. XXXVIII, Fig. 4). 



The ulna is somewhat more reduced than in Palceomeryx furcatus and less so 

 than in the American antelope, and, so far as can be judged from the only available 

 specimen, was not coossified with the radius at any point. The olecranon is missing, 

 but appears to have projected more decidedly backward than in Antilocapra. The 

 proximal radio-ulnar articulation is very different from that of the last-named genus, 

 especially in its much greater vertical diameter and in the larger size of the external 

 radial facet, which, however, is set off less distinctly from the body of the bone. 

 The radio-cubital arcade is longer than in the prong-buck, but owing to the shape of 

 the ulnar shaft is narrower. The shaft is very thin and compressed, but proximally 

 has a considerable antero-posterior diameter, which diminishes rapidly as we pass 

 downward. The distal end has but a slight fore-and-aft dimension, but is somewhat 

 thickened transversely and is deeply notched to receive the external angle of the 

 radius. 



The radius (PI. VI, Fig. 49) is but little shorter than that of Antilocapra, but 

 has quite a different shape ; the lateral and antero-posterior curvatures of the bone 

 are very much as in the recent genus, while the shaft is much broader and less 

 rounded, of oval transverse section and more uniform diameter, much compressed 

 antero-posteriorly, except for the lower one-third of its length. Filhol's figure of 

 the radius of Palaiomeryx magnus (No. 13, PI. XXVIII, Fig. 3) shows a very simi- 

 lar shaft, except for a more pronounced lateral flexure which approximates a sigmoid 

 curvature and for a narrower proximal end. The radius of Blastomeryx, so far as 

 its general shape is concerned, is more like that of the fallow deer than of the prong- 

 buck. The trochlea is wider than in the latter, the groove for the intercondylar 

 ridge of the humerus is narrower and emarginates the anterior border more deeply, 



A. p. s. — VOL. xviii. w. 



