37^ SMITHSONIAN MISCELLANEOUS COLLECTIONS [vOL. 45 



In Penfalagns, in Romcrolagus, and to a less extent in Oryctolagus 

 the radius is slenderer than the ulna, except at the articular ends of 

 the radius, where normal conditions exist. The humerus is distinctly 

 longer than the radius, except in Oryctolagus where their lengths 

 are subequal. 



OCHOTONID.E 

 (Plate XCVIII, ii) 

 In the Ochotonidse the bones of the forearm resemble the ulna and 

 radius of the Leporidse in general form and position. The ulna is 

 distinctly the larger of the two bones of the forearm throughout its 

 whole extent. As noted in the description of that bone under the 

 Leporidse, the ulna has an extra facet at its distal surface for articu- 

 lating with the carpus. The proximal articulating extremity of the 

 radius maintains about the same relative size that it does in the 

 Leporidse, but the distal end is conspicuously reduced and the lower 

 end of the ulna is correspondingly increased. The radius is dis- 

 tinctively shorter than the humerus. 



CARPUS 



Leporid.e 

 (Figure 45, 1-3) 



The full number of carpal bones (nine) is found in the Leporidse. 

 An understanding of their form and position is best obtained from 

 consulting the figures. In all the skeletons the bones have the same 

 relative shapes, sizes, and positions. 



The pisiform is one of the largest carpal bones and has consider- 

 able dorso-palmar depth, except in Pcntalagus where this depth is 

 less and has about the same relative proportions that it has in 

 OcJwtona. 



In the cuneiform, together with a small portion of the pisiform, is 

 a cup-shaped depression into which fits the small rounded pro- 

 jecting head of the ulna. The internal and median portion of the 

 proximal aspect of the cuneiform in most hares is scarcely at all 

 developed, but in some of the skeletons (Pcntalagus, Romcrolagus, 

 Pronolagus, Brachylagus, and rarely in Syh'ilagus and Lcpus) there 

 is found internal to the cup-shaped cavity for the ulna, a small convex 

 surface which articulates with the ulna internal to the projecting 

 convexity. 



The OS centrale is a flask-shaped bone, only the neck of which 

 appears in an undissected carpus. The distal aspect of the neck- 

 like process articulates with the outer portion of the proximal end 

 of the second metacarpal. 



