SCOTT : TOXODONTA OF THE SANTA CRUZ BEDS. 
155 
of the elbow-joint are very peculiar ; the sigmoid notch is deep, describ- 
ing nearly a semicircle, and the coronoid process is prominent. Aside 
from the facet for the anconeal fossa, the humeral surface is altogether 
internal — there is no .trace of any external facet, such as is found in 
almost all other ungulates. Thus, when viewed from the front or dorsal 
Fig. 25. Fig. 26. 
side, the articular surface pursues a very oblique course, from above 
downward and inward, and does not embrace the head of the radius, but 
merely touches it on the internal side. The shaft is heavy and of tri- 
hedral shape, with prominent interosseous crest on the anterior face, and 
tapers but slightly toward the distal end, though the very conspicuous 
styloid process is abruptly contracted ; it has a strongly convex facet for 
the pyramidal, which passes uninterruptedly on the palmar side into the 
surface for the pisiform. 
