.1 New Rabbit from México. 



171 



Animáis differing so widely in habits and manner ofprogres- 

 sion as the present species and the ordinary rabbits would be 

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

 preaerved 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 gemís 

 Lepus. 1 1 uxley describes the clavicle ofthe rabbit as"incom- 

 plete at both ends," and Flowerstates 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 

 of ribs ífig. 33), a condition 

 unknown in the gemís Lepus, 

 in which it is always long 

 and narrow (fig. 34). Flower 

 calis 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 _ steni „ m of 

 those rodents in which the Romeroiagus »,/ 



d- i . i t soni (nat. size). 



avíele is absent or rudimen- 



tary," as the bares, 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 binad manu- 

 brium. The segmente 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 páirs 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 vertebra?, as in Lepus (the first and 

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



Fig. 34— Sternum of 

 Lepus timidzts (much 

 reduced). 





