HYRACOTHEEIUM. 641 



though much longer, than that of the lesser tuberosity. The latter surface 

 has a subround outline, and is quite smooth, although doubtless the surface 

 of insertion of the subscapularis muscle. The facet for the teres minor is a 

 subround concavity. The bicipital groove is short, owing to the early dis- 

 continuance of its bounding ridges. Thus the deltoid crest is little promi- 

 nent. At the distal part of the shaft the inner side is rather flat; the exter- 

 nal has only an obtuse indication of the crest usual in many types, e. g., 

 Hyracliyus agrestis. In this respect it resembles Triplopus cubitalis. There 

 are no epicondyles. The principal or internal condyle is, as usual, a troch- 

 lea with bounding ridges, of which the internal is an arc of wider diameter 

 than the external, and is the more acute of the two. It is, however, not ex- 

 panded as in many other mammals. The internal condyle has an articular 

 surface which is flat transversely and is widest posteriorly. Its external 

 border is obliquely directed inwards and forwards, but turns abruptly in- 

 wards at the middle of the inferior or distal curve, thus discontinuing the 

 condyle. Its place is then occupied by an oblique muscular insertion. 

 This external condyle, which applies to an oblique process of the head of 

 the radius, is much more prominent than in either Hyrachyus eximius or 

 Triplopus cubitalis. 



Measurements of humerus. 



M. 



Length from edge of great tuberosity 096 



Width of head with tnberosities (greatest) 022 



Diaraetersof articular surface of head ^'^°*^^°P°^*''"°'" "1*^ 



( transverse 018 



Diameters of middle of shaft J •■^°t''™PO^*''r^°r 0095 



I transverse 0100 



anteropo8teriorJ°^^°°«'""'^g« 0120 



c of outer ridge : 0125 



transverse^ °^'°°«'''='"i''yl*^ 0090 



( of outer condyle 0060 



Diameters of condvles < 



The radius is about as long as the humerus; it is thus longer than in 

 Hyrachyus agrestis and not nearly so long as in TripJopus cubitalis. As it 

 has no acute edges, its section is everywhere a transverse, flattened oval. 

 The diameters of the shaft are subequal, increasing a little distally. The 

 head is flattened below and above; and the internal and external borders 

 are gently convex. The portion that applies to the external condyle is an 

 aliform projection with an acute exteinal border. Its articular plane is 

 41 



