400 SMITHSONIAN MISCELLANEOUS COLLECTIONS [vOL. 45 



middle. The mesosternal segments have a tendency to be less flat- 

 tened than they are in Lcpus. The xiphisternum is shorter than the 

 presternum, its ends moderately enlarged, the posterior end being 

 more enlarged, relatively, than in Lcpus. 



The ribs (pi. xciv, 5) are somewhat peculiar, but there is 

 nothing to distinguish them from the ribs of Oryctolagus. The 

 shafts of the anterior ribs are only moderately enlarged in their 

 ventral portions. The spine-like portion of tubercles is well de- 

 veloped on all the skeletons except that of Syh'ilagiis mincnsis where 

 the spines are poorly developed and are last seen on the seventh 

 pair of ribs instead of on the eighth as in the others. 



Shoulder Girdle and Upper Extremity. — The scapula (pi. xcvii, 

 7) of Sylvilagus is different in form from the same bone of 

 Lepus, Romerolagus, and Proiiolagus, but shows nothing tangible by 

 which it can be distinguished from the scapulae of the other genera. 

 It is relatively narrow\ the superior border relatively less convex, the 

 antero-superior angle moderately pronounced, and the supraspinous 

 fossa relatively narrow, w'hen compared with the scapula of Lepus. 



Regarding the humerus of Sylz'ilagus there is nothing peculiar 

 by which it can be distinguished from the humeri of many of the 

 other genera. 



The forms, relations, sizes, and positions of the radius and ulna 

 (pi. xcviii, 4) are alike in Syhnlagus and in Liumolagus. These 

 bones are subequal in size; the ulna is not reduced in the middle of 

 its shaft, and is situated external to radius rather than behind it. 

 Both bones are moderately slender. The radius is equal to the 

 hvunerus in length. 



The carpus, the metacarpus, and the phalanges of Sylvilagus are 

 entirely similar in form and position to these bones in any of 

 the Leporidse, as detailed in the general account of the wrist and 

 hand (p. 378). 



Pelvis and Loiver Extremity. — The os innominatum has about the 

 same general form in Sylvilagus and in Oryctolagus. The ilium is 

 not wide and shovel-like. The anterior edge of the acetabulum is 

 about midway between the extreme anterior and posterior points 

 of the OS innominatum or just a little posterior to the middle 

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

 rounded off. The obturator foramen is apparently less rotund than 

 is the case with Lcpus. 



The femur, the tibia, and the fibula of Sylvilagus are typical for 

 the family, as detailed in the general account (p. 382). and show 

 nothing that is peculiar to the genus. 



