lvon] the hares and their allies 3° I 



The obturator foramen is more rotund in Lcpus than in most other 

 genera. 



In Oryctolagus, Syh'ilagus, and Bracliylagiis the ossa innominata 

 have about the same general form. There is nothing to distinguish 

 these bones in the first two genera, but the innominate bone of 

 Brachylagiis can be distinguished by its smaller size and the greater 

 prominence of the tubercle in front of the acetabulum and by a 

 slenderer descending ramus of the pubis and shorter distance from 

 the tuberosity of the ischium to nearest point of the obturator 

 foramen. In the above three genera the ilium is not so wide and 

 shovel-like as it is in Lepiis. The anterior edge of the acetabulum 

 is about equidistant between the extreme anterior and posterior 

 points of the os innominatum, or just a little posterior to the equidis- 

 tant point. The antero-superior angle of the ilium is obliquely 

 rounded off. The thyroid foramen is usually less rotund than it is 

 in Lcpiis. 



The genus Linmolagus has wide ilia, much like those of Lcpus, 

 but the antero-superior angle is not obliquely rounded off. The 

 antero-ventral angle is produced into a blunt, very short spine. The 

 horizontal rami of the pubic bones slope backward more than they 

 •do in the other genera except Romcrolagus. 



The OS innominatum of Romerolagus closely resembles that of 

 Limnolagus. The only marked differences, aside from its slender 

 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. In all the other groups except the genus Prono- 

 Jagiis the ventral edge of the ilium has a more or less pronounced 

 •concavity on its posterior half. 



The genus Pronolagus has an os innominatum resembling in most 

 respects that of Sylz'ilagiis and Oryctolagus, but the ilium is even 

 narrower than it is in them. Its ventral edge is straight, in this 

 respect being like the ventral edge of the ilium of Romcrolagus. 



Ochotonid.e 



The pelvis of the Ochotonidse is very different from the pelvis 

 •of the Leporidas. The most notable difference is the absence of the 

 symphysis pubis. As none of the few available skeletons is sexed, 

 it is impossible to say whether the difference is sexual or not. The 

 pubic bones are widely separated from one another, but are connected 

 by a ligament. 



The OS innominatum of the Ochotonidae as a whole is longer and 

 .more slender than that bone in the Leporidse. The ilium is less ex- 



