34 TEETIAET VEETEBEATA OE THE EAYtTM. 



backwards as in the present specimen; moreover, as in the Elephant, the supra- 

 scapular border is sharply bent above the origin of the spine, the portion in front 

 making an angle of 65 degrees with that behind. The coracoid process is also quite 

 dissimilar, while the spine inclines forwards rather than backwards and the prescapular 

 fossa is smaller. 



The humerus (text-fig. 16) differs very considerably both from that of Elephas 

 and also from that of the Dinocerata. Its most striking general characteristic is 

 the great antero-posterior compression of its shaft and distal end. The head (A.) 

 is large and much more convex antero-posteriorly than from within outwards, so that 

 it almost forms part of a cylinder. The head is most prominent posteriorly. The 

 inner (lesser) tuberosity {It.) is small and its inner face flattened. The outer (greater) 

 tuberosity (g.t.) is large and forms a very prominent crest projecting considerably in 

 front, but is not continued down the face of the shaft as a well-marked ridge, 

 such as occurs in Uintatherium, nor is it so massive as in Elephas. The bicipital 

 groove {b.g.) is broad and not very distinct. Beneath it the shaft is strongly 

 compressed from before backwards, and about the middle of its length it bears 

 on its outer border a prominence [d.) formed by the great development of the deltoid 

 crest for a short distance. From this prominence a short ridge runs obliquely across 

 to about the middle of the shaft. The coronoid fossa {c.f.) is very shallow ; it is 

 bordered internally by a broad rounded ridge running up towards the lower end 

 of the oblique deltoid ridge above mentioned. The outer border is the inner edge 

 of the prominent supinator ridge (s.r.), which, though much less developed than in 

 Elephas, is much more so than in Uintatherium. The outer condyle (o.c.) is large, 

 but does not project far posteriorly ; the inner condyle {i.e.) also is very large, and is 

 produced backwards into a prominent projecting flange. The olecranon fossa {o.f.) 

 is broad and shallow, and the surface of the whole shaft above it is strongly concave 

 from side to side, owing to the backward projection of the condyles. 



The trochlear surface for articulation with the bones of the forearm is divided by 

 a shallow depression into an outer and less convex portion {tr.o.) articulating with 

 the radius and ulna, and an inner more convex portion {tr.i.) articulating almost 

 entirely with the ulaa, the inner surface of the radius being very small (see radius). 



The bones of the forearm are separate (text-fig. 19, p. 40); in their proportions 

 they are short and stout, and the ulna is very much larger than the radius, as in the 

 Proboscidea. In their general form these bones approach very nearly to those of 

 Elephas, and differ widely from those of the Dinocerata. Fortunately, in one 

 instance at least, an ulna and part of a radius were found associated with undoubted 

 Arsinoitherium remains, with no intermingling of PalcBomastodon bones, in such a 

 way as to leave no doubt as to the correctness of their reference to the present 

 genus. Moreover, the size and massiveness of some specimens, as well as the large 

 number found, point in the same direction. 



