THE OSTEOLOGY OF ELOTHERIUM. 301 



trochlea, no part of the articular surface on the ulna presenting proximally, for the radius 

 occupies the entire distal aspect of the humerus. Only the proximal portion of the facet 

 for the humerus extends across the entire breadth of the ulna ; for the rest of its course 

 this facet is confined to the inner side. The shaft of the ulna is somewhat reduced, but 

 is not interrupted at any point and, indeed, it is quite stout for its entire length ; its prin- 

 cipal diameter is the transverse, the antero-posterior thickness being decidedly dimin- 

 ished. Below the head it narrows and then expands to its maximum breadth, from 

 which point it narrows gradually to the distal end. On its external side the shaft is 

 quite deeply channeled. The distal end is small and bears a saddle-shaped facet for the 

 pyramidal, which is concave transversely and convex in the dorso-palmar direction ; its 

 external border is compressed and extends as a sharp edge behind the body of the bone, 

 forming a concavity on the palmar face. The pisiform facet is continuous with that for 

 the pyramidal. The ulna extends distally below the level of the radius and thus arises the 

 very exceptional condition of an articulation between the ulna and the lunar. The facet 

 for this carpal element is small and is entirely confined to the radial side of the ulna, the 

 distal end of the latter not extending at all upon the proximal face of the lunar. In most 

 artiodactyls in which the functional digits have been reduced to two, the radius tends to 

 encroach more or less extensively upon the proximal face of the pyramidal, for which 

 extension the diminution of the ulna makes a way. In Elotherium the arrangement is 

 different, the ulna occupying the entire j>roximal surface of the pyramidal, and by 

 extending below the level of the radius securing a lateral contact with the lunar. Indeed, 

 this arrangement quite precludes the attainment of the more usual radial-pyramidal 

 articulation. 



The ulna of Hippopotamus is proportionately much shorter and in every way more 

 massive than that of Elotherium ; it also has a very much larger and more prominent 

 olecranon, as would naturally follow from the immensely greater weight of body which 

 requires support upon the limbs. There appears to be a slight disto-lateral contact 

 between the ulna and the lunar ; at all events, the radius does not extend over upon the 

 pyramidal. In Sus the ulna is free throughout and its shaft is relatively much shorter 

 and heavier than in Elotherium ; the ulna and lunar do not come into contact. The 

 ulna of Dicotyles is more reduced than that of the White River genus and the connections 

 of the carpals with one another and with the metacarpus are upon quite a different plan. 



Measurements. 



Scapula, height 0.430 



Scapula, greatest width 245 



Scapula, breadth of Deck 065 



Scapula, glenoid cavity, ant. -post, diameter 06S 



