370 SMITHSONIAN MISCELLANEOUS COLLECTIONS [vOL. 45 



in the other genera in having its two portions very unequally de- 

 veloped, the main one being very broad and shallow, and the external 

 portion much reduced. 



Bracliylagiis and Romerolagiis have the slenderest humeri ; Orycto- 

 lagns and especially Pcntalagiis have rather thick, heavy ones. All 

 the other groups may be said to have moderately developed humeri. 



The external condyloid ridge is very short and poorly developed 

 in all the hares. Romcrolagits has the most prominent external 

 condyloid ridge ; Brachylagits has a ridge as wide but not so long ; 

 Lininolagus has a short and comparatively wide ridge, but only a 

 trifle more conspicuous than the ridge in Sylz'ilagiis or in the other 

 genera. 



OCHOTONID.E 



The humeri of the Ochotonidse have a strong resemblance to those 

 of the Leporidas. The head of the bone is more globular in the 

 former, the bicipital groove does not encroach on its anterior surface. 



The tuberosities of the humeri of Ochotona bear about the same 

 general proportions to one another that they do in the hares and 

 rabbits. The greater tuberosity does not project so far upward in 

 Ochotona as it does in the Lcporidce, so that the head of the humerus 

 is the highest point of the bone, while in the hares and rabbits the 

 greater tuberosity is the highest point. 



When viewed from the side, the head of the humerus in the pikas 

 is seen to project farther backward than in the hares, and to form a 

 sort of hook wnth the shaft of the bone. 



The double trachlear surface at the distal end of the humerus is 

 shallow^ and wider in Ochotona than in any of the Leporidge. 



The groove subtending the internal condyle is rather shallow and 

 inconspicuous in Ochotona; it is developed to about the same 

 degree that it is in Ronicrolagus. 



RADIUS AND ULNA 



Leporid.e 

 (Plate XCVIII, i-io) 



The bones of the forearm of the Leporidge show some interesting 

 differences among the various genera, in regard to their relative 

 development and the length of the radius compared with the length 

 of the humerus. 



The radius and ulna are always perfectly distinct, but they are in 

 contact with one another throughout the greater part of their extent. 

 At the point of contact there is a certain amount of fusion, but at the 

 same time each bone maintains its individual distinctness. 



