92 THE MERYCOIDODONTID/E 



glenoid fossa in the former is anteroposterior and in the latter transverse. The position of the 

 acromion and metacromion in E-poreodon is very similar to that of recent carnivores in which the 

 acromion extends over the neck and in the direction of the coracoid, while the metacromion is but 

 slightly removed from the acromion and is located on the distal end of the spine. The spine of the 

 carnivore scapula divides it also into two subequal parts, as in Eporeodon and in Agriochcerus. 



The humerus (Fig. 57) has about the same length as that of Sus but is far less robust. The 

 head (Fig. 58) has nearly the same shape but does not overhang the shaft as far as in the pig. 

 The external tuberosity is not prominent and does not extend far above the articular surface. The 

 medial and lateral tuberosities are well marked. The bicipital groove is shallow and undivided. 

 The external and lateral tuberosities are separated by a wide, deep groove. The shaft is nearly 

 straight. Near the distal end the flattening is in an anteroposterior direction. The lateral tuber- 

 osity does not rise above the articular surface, as it does in the pig, sheep, camel, and deer. In this 

 respect it resembles Agriochcerus rather than Merycoidodon. The shaft of Eforeodon is decidedly 

 carnivore-like in appearance, because of its cylindrical form and the anteroposterior flattening at its 

 distal end. Another character not possessed by the ordinary ungulates is the breadth and unusual 

 size of the internal condyle. The deltoid ridge is weak. There is no entepicondylar foramen. The 

 most dependent part of the bone is formed by the internal flange of the inner trochlea. It is thick 

 and rounded, forming the border of the anconeal fossa. The distal articular surface is divided into 

 an external and internal trochlear surface by a low, thick, rounded carina, located nearer the outer 

 than the inner side, i.e., the articular facet for the ulna much exceeds that for the radius in width. 

 This is true for all of the recent artiodactyles, except that the carina is placed much nearer the outer 

 border than in E-poreodon. The external trochlear surface of the latter is much narrower and 

 deeper, terminating externally in a prominent flange. The distal end of this bone in many ways 

 resembles that of a bear more closely than that of an ungulate. In Merycoidodon the two trochlear 

 facets are nearly subequal. The olecranon fossa is very deep and is separated from the coronoid 

 fossa by an extremely thin osseous plate. The condyloid ridges are rounded and well defined. 

 The external condyle is very rugose. 



The radius and ulna (Fig. 59) are of approximately the same length in Sus and in Eforeodon. 

 The radius is slender and curved. It is large at both ends, and the proximal surface extends across 

 the entire humeral trochlear facet. The radius abruptly expands near the distal articular surfaces. 

 The proximal articular surface is very suggestive of Agriochcerus, but probably there was not so 

 much freedom of movement possible as in that genus. The distal end shows no marked peculi- 

 arities. The articular facets for the scaphoid and lunar are concavoconvex. There is a deep and 

 narrow groove on the middle of the front of the distal end. 



The ulna is long and slender. The olecranon is stout, thick and oblong-shaped in lateral out- 

 line. There is a deep groove at its proximal end, probably for the insertion of the tendon of the 

 triceps. In its function and structure the olecranon resembles the patella. The greater sigmoid 

 cavity is divided by a slight rounded ridge into two nearly equal articular facets. The inferior 

 boundary of this cavity forms a rudimentary coronoid process. The shaft is moderately heavy in its 

 proximal portion but tapers and flattens medially and distal ly. There are deep grooves on its outer 

 and inner surfaces. Its distal end shows a distinct articulation for the pisiform. The styloid process 

 is represented by a small rugosity. 



The carpus is primitive (Fig. 60) for an artiodactyle ungulate. That is, the bones of the carpus 

 are interlocking in that the cuneiform rests upon the unciform, the lunar on the unciform and os 

 magnum, and the scaphoid on the os magnum and trapezoid. In Agriochcerus the carpus shows a 

 more serial arrangement in that the cuneiform rests on the unciform, the lunar (semilunar) mainly 

 on the os magnum, and the scaphoid chiefly on the trapezium and trapezoid, with a considerable 

 contact with the os magnum. This is not surprising, because Agriochcerus was more specialized in 

 some other respects than the members of the Merycoidodontidae. 



The pisiform bone is well developed, but the trapezium is lacking. The carpal elements are not 

 so flattened as are those of Agriochcerus and do not differ materially from those of Merycoidodon. 



