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 conyex 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 haye 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 proximal 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 attamment of the more usual radial-pyramidal 
articulation. ; 
The ulna of Hippopotamus is proportionately much shorter and in eyery way more 
massive than that of Hotherium ; 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. 
4 
Measurements. 
Scapula, height. ...-...--.seeesceeceeseeeeeesnereneeneecesesesceaceces, cteeecseccrecscesnececesssennseeccensceessnsees 0.430 
Scapula, greatest Widthh...........-.c0s--sssececsneceeceeteceeeeecncecerenee cuneecccueseccceccccnseseceeererscerene 245 
Scapula, breadth Of NECK -..--+.-..-s0scescnceeeeccececcnaeevteeouanasssscancavestceccccattsencteacncesessccccrese= 065 
Scapula, glenoid cavity, ant.-post. Ciameter........:1.cesecseeeeeseceeessseeeseecceceneereesssesaneeereeees .068 
