A New Rabbit from Mexico. 



171 



Animals differing so widely in habits and manner of progres 

 sion as the present species and the ordinary rabbits would be 

 expected to differ in their skeletons. Fortunately, Mr. Nelson 

 preserved a perfect skeleton of the new rabbit, which on com 

 parison with those of the several subgenera of Lepus shows differ 

 ences of considerable morphologic weight. 



The clavicle is complete and articulates directly with the 

 sternum (fig. 33) a thing that never happens in the genus 

 Lepus. Huxley describes the clavicle of the rabbit as " incom 

 plete at both ends," and Flower states that it "is very short and 

 is suspended by long ligaments between the scapula and the 

 sternum." The manubrium or presternum is broadly expanded 

 between and anterior to the 

 articulation of the first pair ^*)J 

 of ribs (fig. 33), a condition 

 unknown in the genus Lepus, 

 in which it is always long 

 and narrow (fig. 34). Flower 

 calls attention to the corre 

 lation existing between the 

 form of the presternum and 

 the degree of development of 

 the clavicle, stating that " the 

 presternum is compressed 

 and produced forwards in FlG . 33 _ sternum of 

 those rodents in which the Romeroiagus nei- 

 clavicle is absent or rudimen- soni (nat> size) ' 

 tary," as the hares, and " is generally broad in the forms which 

 have the clavicle well developed, as the rats, beavers, &c." This 

 interesting correlation is well exemplified in the Popocatepetl 

 rabbit, which, having a complete clavicle, has also a broad manu 

 brium. The segments of the mesosternum (between the pre 

 sternum and xiphoid) are only three in number (fig 33), while 

 in all the subgenera of Lepus the number is four (fig. 34). The 

 ribs are correspondingly reduced, only six pairs instead of seven 

 articulating with the sternum. The tubercles of the ribs are not 

 produced into spiniform processes, as in Lepus, and disappear in 

 the sixth pair. In Lepus they extend to the eighth pair. The 

 scapula is rather narrow, with a long metacromial process, as in 

 Lepus. There are four sacral vertebrae, as in Lepus (the first and 

 anterior part of the second articulating with the ilia), and nine 



FIG. 34 Sternum of 

 Lepus timidus (much- 

 reduced). 



