140 Annals of the Carnegie Museum. 



at an obtuse angle, it meets the convex superior border. The anterior 

 border is convex. The postscapula is triangular in outline, while the 

 general outline of the prescapula is subcrescentic. The coracoid is 

 small. The spine extends from about two inches above the glenoid 

 cavity to the superior border. It is triangular in outline with a rather 

 strong spinous process directly opposite the angle formed by the junc- 

 tion of the posterior and superior borders. The glenoid cavity is 

 rather deep and subcircular in outline. 



The humerus, like all the other bones of the fore leg, is propor- 

 tionately rather long and slender. The greater and lesser tuberosities 

 are prominent, and the bicipital groove is correspondingly deep. 

 The deltoid ridge is well developed and continuous throughout one 

 half the entire length of the bone. The supinator ridge is low and 

 short. The external condyle is prominent, while the internal is faint, 

 or obsolete. The ulnar and radial articulations enter subequally into 

 the construction of the trochlea, the former slightly predominating. 

 The anconeal fossa is deep. 



The radius is rather broad and flat, with its transver.se diameter 

 almost twice the fore and aft diameter. The distal end is much 

 broader and deeper than the proximal. The anterior surface is strongly 

 convex inferiorly, while the posterior surface is concave. 



The shaft of the ulna is triangular in cross-section. The olecranon 

 is of moderate height, broad, and with an anterosuperior notch. 

 The coronoid process is large and sharp anteriorly, in harmony with 

 the deep anconeal fossa of the humerus. Distally there is a moderate 

 articular facet for the pyramidal, and relatively a rather large articular 

 surface for the pisiform. 



The manus of Tn'goinas oshorni differs from all other American 

 Aceratheres, so far as we know their structure, in being functionally tet- 

 radactyl. In the present genus and species the fifth digit is not only 

 present, but it still retains all the elements (metacarpal, first, second, 

 and third phalanges and sesamoids) common to digits II, III, and 

 IV. These elements are however somewhat reduced in size. 



The carpus is composed of those elements that are ordinarily found in 

 that of the perissodactyl manus, viz., superiorly, the scaphoid, lunar, 

 pyramidal, and pisiform ; inferiorly, the trapezium, trapezoid, mag- 

 num and unciform. The scaphoid is much the larger bone of the 

 ]jroximal series. It articulates above with the radius by a concave 

 surface of irregular pentagonal outline. Inferiorly the scaphoid artic- 



