52 THE MERYCOIDODONTIM: 



deep. The deltoid ridge is prominent and passes farther down than is usual in the artiodactyls, and the supinator 

 ridge is also well developed. . . . The trochlea is divided into three surfaces almost equally large, of which the 

 middle is strongly convex and is sharply differentiated from the compressed ridge present in the ruminants. 

 The internal horder of the trochlea is continued obliquely downward. . . . The humerus of Oreodon is far more 

 like that of Anoflothcrium than that of any of the recent artiodactyls. 



The radius and ulna are separate. The proximal end of the radius extends transversely over the entire 

 trochlea of the humerus and is divided into three corresponding surfaces, of which the middle is deeply excavated, 

 the inner less excavated, and the outer almost flat and obliquely placed. . . . The distal end is occupied with the 

 marked articular surfaces for the scaphoid and lunar; the former is concave forwardly and inwardly, convex 

 posteriorly and externally, and is separated from the crescent-shaped surface by the contact of the anterior and 

 posterior borders. These surfaces lie on somewhat higher levels and are concave fore and aft. In all of the 

 specimens which I have studied the radius has no contact surfaces with the pyramid. . . . 



The ulna is a moderately strong bone, with a laterally compressed shaft, triangular in cross section, and 

 with a somewhat short olecranon. The excavated articular surface for the humerus stands almost parallel to the 

 long axis of the ulna. . . . The lower end is deeply notched to receive the radius, and the distal surface for the 

 pyramid is decidedly flat and rounded; on the posterior side of it there is a small facet for the pisiform bone. 



The carpus of Oreodon is in many respects primitive and in others very much specialized. The scaphoid is 

 a proportionally massive bone, almost cubical, with only the anteroposterior diameter surpassing that in the other 

 two directions; the scaphoid is much lower than in recent swine. . . . The posterior side is nearly flat, lacking 

 the laterally compressed process that is present in Dieotyles. . . . The distal side is divided into three large unequal 

 articular surfaces, of which the largest is definitely for the magnum, while that for the trapezium is extremely 

 small; the surfaces for the trapezoid and magnum are only indistinctly separated. The lunar is very character- 

 istic; the proximal surface is strongly convex fore and aft but has almost no posterior excavation; the diameter 

 fore and aft is relatively small, but the vertical is greater. The distal surface departs most significantly from the 

 structure usual in the artiodactyls in that the beak-shaped process is not in the mid-line but is directed almost 

 entirely toward the radial side. Seen from the front the lunar appears scarcely to rest upon the magnum, touch- 

 ing it only laterally. However, posteriorly the magnum curves below the lunar, and in this manner the magnum 

 surface of the lunar is directed partly distally. The distal surface is also for the most part occupied by the great 

 facet for the unciform. ... In accord with the large ulna the pyramid is proportionally well developed. Like 

 the scaphoid it is wide and low; the ulnar articular surface is a simple groove, narrow fore and aft, expanded 

 transversely and limited to the proximal side of the bone. It is very different from the complicated facet of most 

 of the artiodactyls. The pisiform facet is a conspicuous hollow, separated from the ulnar surface by a sharp edge. 

 The entire distal side is occupied by the semicircular shallow facet for the unciform. The pisiform makes a sharp 

 contrast to the short and stout pisiform of the recent ruminants and swine in that it is strikingly slender and 

 elongated and resembles rather certain creodonts (for example, Mewnyx). Since the articular surfaces for the 

 ulna and pyramid are only indistinctly separated, the proximal end is a rounded head, and the free end is but 

 slightly expanded. . . . The trapezoid is a rather large bone, especially in the anteroposterior direction; it carries 

 only Mc. II and touches none of the other metacarpals. The anterior side of the magnum is wide and low; 

 posteriorly, however, the bone rises in altitude to form a round projection, which is inserted into an excavation of 

 the lower side of the scaphoid. The proximal side is almost entirely occupied by the pronounced facet for the 

 scaphoid, while the lunar surface is placed so obliquely that it, also posteriorly, can be called lateral rather than 

 proximal. On the distal side is a large saddle-shaped facet for Mc. Ill and on the radial side a small surface 

 for Mc. II. . . . Here is found the first stage of "adaptive reduction," which has progressed much farther in many 

 of the later genera. The long uncinate process of the posterior side of the magnum, which has become so large 

 in most of the hoofed animals, is very diminutive in Oreodon. . . . The unciform is the largest of the carpal 

 bones and penetrates deeply into the carpus. . . . The articular surface for the pyramid is larger than that for the 

 lunar; . . . both facets are of nearly equal size in front, but posteriorly the lunar surface is somewhat smaller. 

 On the radial side is a small pronounced facet for Mc. Ill, forming a sharp edge with the lunar facet; the 

 distal side is occupied by the facets for Mcs. IV and V; that for Mc. IV is large, quadratic, flat, and strong 

 distally, while that for Mc. V is small and saddle-shaped. The posterior hook is small. . . . The unciform is fairly 

 widely separated from the magnum by the unusual development of the distal rostral process of the lunar, instead 

 of being in contact with each other, as in most hoofed animals. In spite of this these bones occupy more than 

 half the width of the carpus, which is brought about by the shifting of the lunar to the radial side of the carpus 

 and by the small size of the element. 



.... A rudimentary thumb is present in the metacarpals. ... I have been able to verify this by observation 

 of several specimens. . . . There is therefore no question that the hand of Oreodon is normally pentadactyl, which 

 is further corroborated by the presence of the thumb in Protoreodon. Mc. I is short and slender. ... In the 



