300 THE OSTEOLOGY OF ELOTHERIUM. : 
external border, while in Klotherium this difference is decidedly less marked. In Sus 
the humerus resembles that of the White River genus in form, but is proportionately 
very much shorter; the deltoid ridge is shorter and less prominent, while the supinator 
ridge and the epicondyles are more so. 
The radius and ulna (Pl. XVIII, Fig. 10) are firmly coéssified in all the known 
species of Klotherium, though the suture between them is clearly marked, eyen in old 
animals. ‘The radius is relatively very long, but rather slender; the head is quite thick, 
but of only moderate breadth, projecting most toward the external side. The humeral 
surface is composed of three connected facets, of which the internal one is much the 
largest and bears an elevated ridge for the corresponding depression on the humeral 
trochlea. The groove for the intercondylar ridge of the latter is quite broad and notches 
the anterior border of the radius. The shaft is rather narrow transversely, but quite 
thick and heavy, and arches forward but moderately ; the distal portion is broadened and 
thickened and bears upon its dorsal face a deep tendinal sulcus, bounded by very promi- 
nent ridges. The distal face is quite broad, but without much dorso-palmar extension, 
and carries two well-distinguished carpal facets, which pursue an oblique course, from 
before backward and inward. The scaphoidal facet, which is the smaller of the two, is 
concave in front, saddle-shaped behind, and is reflected up upon the posterior face of the 
bone. The facet for the lunar is much larger than that for the scaphoid, and has a 
somewhat similar shape, but the anterior concayity is not so deep, and the articular 
surface is carried much farther up upon the palmar side of the radius. The radius has 
no contact with the pyramidal. 
In Hippopotamus the forearm bones are ankylosed, though somewhat less intimately 
than in Elotherium. The radius is very short, broad and thick, and is almost straight. 
The external facet for the humerus is larger and more concaye and the carpal facets are of 
more nearly equal size, while that for the lunar rises much more steeply toward the ulnar 
side. In Sus the two bones are separate, and the radius is short, very heavy and arched 
forward ; its distal end is much more thickened than in Elotherium, the facet for the 
scaphoid is relatively larger, while that for the lunar is smaller and is extensively 
reflected upon the palmar face of the radius. In Dicotyles the ulna and radius have 
coalesced even more completely than in Elotheriwm. 
The w/na has a very long, thick and prominent olecranon, which projects far behind 
the plane of the shaft. The process is conyex on the outer side and concave on the inner, 
thickened and club-shaped at the free end, which displays a broad, shallow sulcus for the 
extensor tendons. The sigmoid notch is deep and the coronoid process prominent, as is 
required by the great depth of the anconeal fossa on the humerus. ‘The articulation of 
the ulna with the latter is confined to the posterior and superior aspects of the humeral 
