424 SMITHSONIAN MISCELLANEOUS COLLECTIONS [vOL. 45 



tween the two superior angles is contained but one and a half times 

 in the scapular length. 



There is little that is peculiar about the humerus. Like that of 

 Brachxlagiis it is slenderer than in most of the other genera. The 

 groove subtending the internal condyle is not well marked. The 

 external condyloid ridge is better developed than in the other genera. 

 The humerus of Romcrolagiis is distinctly longer than the radius. 



Unlike the other genera, except Oryctolagns and especially Pcnta- 

 lagiis, the radius of Rouierolagns is slenderer than the ulna (pi. 

 xcviii, 9) ; at its articular ends the usual degree of development 

 takes place. 



The carpus, the metacarpus, and the phalanges of Romcrolagiis 

 are entirely similar in form and position to these same bones in any 

 of the Leporidas as detailed in the general account of the wrist and 

 the hand (page 378). 



Pelvis and Lozccr Extremity.- — The os innominatum of Rouiero- 

 lagns closely resembles that of Limnolagiis. The only marked dif- 

 ference, aside from its slenderer formation, is the more pronounced 

 development of the short, blunt spine at the antero-ventral angle, 

 and the straightness of the ventral edge of the ilium. The ilia are 

 wide, but their antero-superior angles are not obliquely rounded off. 

 The horizontal rami of the pubic bones slope backward to a greater 

 extent than they do in other genera with the exception of Limno- 

 lagiis. 



The femur of Rouierolagns is entirely similar to the same bone in 

 any of the Leporidse and needs no special mention. 



The fusion of the fibula with tibia (pi. xcix, 9) in Rouierolagns 

 takes place at the middle of the latter bone, thus resembling Ochotona. 

 In other genera of the Leporidse, except Pentalagus, it occurs just 

 above the middle. The tibia of Rouierolagns, like that of Limnolagiis 

 and Pentalagus, is relatively heavier and also more curved than in the 

 other genera, the inner surface of the lower part of its shaft being 

 concave as in Ochotona. 



The basal width of the metatarsus is contained twice in the length 

 of the third metatarsal. 



The combined lengths of the three phalanges approximately equal 

 the length of the metatarsals to which they belong. 



Rouierolagns nelsoni, the only species of the genus, is represented 

 by a single complete skeleton and several separate skulls. 



Rouierolagns is one of the best marked genera of the Leporidse. 

 Externally it appears much like Pentalagus. 



