3^2 SMITHSONIAN MISCELLANEOUS COLLECTIONS [vOL. 45 



panded, thicker, its ventral third separated from the dorsal two- 

 thirds by a well-marked ridge, which terminates anteriorly and 

 ventrally in a well-marked, recurved, pointed spine. The tuberosity 

 of the ischium is not so heavy and it lacks the processes seen in the 

 Leporidse. The thyroid foramen is egg-shaped, the small end of 

 the egg being directed forward toward the acetabulum. 



The horizontal ramus of the pubis is very short, the descendin'g 

 ramus long, directed oblicjuely backward and downward. 



FEMUR 



The femora in all the Leporidge resemble one another very closely. 

 The bone is stout and heavy in Pcntalagus, it is relatively thicker in 

 Oryctolagiis than in the remaining genera, and it is slenderest in 

 Brachylagus, but individuals vary much in this respect. Of two 

 Lcpiis cainpcstris, one from Nebraska and the other from Kansas, 

 one is relatively thicker than the other. The same individual varia- 

 tion is found in the series of skeletons of SylvUagns floridanus. In 

 .most of the skeletons the femur is a little shorter than the tibia. 

 In Lepiis {Macrotolagns) tcxianns, however, it is decidedly shorter, 

 in Pcntalagus the two bones are subequal in length. 



The femur in the Ochotonidse has the same general characteristics 

 that it has in Leporidse, but it is a relatively thicker and heavier bone ; 

 the third trochanter is much reduced in size, the lesser trochanter is 

 relatively larger, and the fossa behind the great trochanter is not 

 so deep. Its length is a trifle less than that of the tibia. 



TIBIA AND FIBULA 



(Plate XCIX) 

 The tibia and fibula show about as few variations in the different 

 groups of the Leporid?e as do the femora. The fibula is a free, dis- 

 tinct bone above, but at a point somewhat above the middle of the 

 tibia it becomes intimately fused with the bone and its identity is 

 lost sight of from there on, in all the genera except Romcrolagiis and 

 Pentalagus, in which genera the fusion of fibula and tibia occurs at 

 the middle of the latter bone. The point of fusion is highest in 

 Lepiis, next highest in Syknlagus, Oryctolagns, Pronolagus, and 

 Linmolagus, and in Brachylagus it is just above the middle point 

 of the tibia. In Pcntalagus the tibia and fibula are relatively much 

 heavier than they are in the other genera. In Ronicrolagus and 

 Linmolagus also the tibia is relatively heavier than in the remaining 



