A 



172 Merrkim — A New Rahhit from Mexico. 



caudal vertebrae, the last three of which are upturned and rudi- 

 mentary. 



The fifth cervical vertebra is peculiar. Its transverse process 

 projects directly outward instead of backward, and its inferior 

 lamella has only a trace of the posterior extension usual in rab- 

 bits. The metapophyses begin on the tenth dorsal vertebra and 

 are present in all the succeeding vertebne to the last lumbar, in- 

 clusive. The anapophyses are much as in Lejms proper, being- 

 present, though small, on the ninth to twelfth dorsals, inclusive, 

 and on all the lumbar vertebra^ except the sixth and seventh. 

 The transverse processes of the lumbar vertebrae are peculiar, 

 each developing a broad posterior flange, which extends the full 

 length of the side of the vertebra. Hypopoi)hyses are present 

 on the first, second, and third lumbar vertebrfc, as in Lepus, 

 though relatively short. 



The bones of the legs and feet show a number of more or less 

 important differences, some of which may be mentioned here. 

 The depression on the inner side of the trochlear facet of the 

 humerus is small and flat instead of deeply sulcate ; the fibular 

 malleolus is less strongly developed ; the navicular bone differs 

 materially in form and its inferior crest is conspicuously shorter 

 than in Lepas, and does not reach forward beneath the bases of 

 the metatarsals. 



The skull, singularly enough, does not show the departure 

 from Lepus that one would expect from a study of the other 

 bones. It agrees in the main with skulls of the American cot- 

 tontails (sul)genus Sylvilagus), but differs in the postorbital pro- 

 cesses, which are small, divergent posteriorly, and altogether 

 wanting anteriorly, and in the jugab which is greatl}^ elongated 

 posteriorly. The interparietal is distinct, and in old age becomes 

 ankylosed with the supraoccipital. The thoroughly leporine 

 character of the skull shows that the animal can hardly be re- 

 garded as ancestral to Lepm, as might have been inferred from 

 its short ears, short hind legs, and various skeletal characters, 

 but that it is a specialized offshoot from the genus Lepus itself. 



The taxonomic value of the characters which serve to dis- 

 tinguish the Popocatepetl rabbit from the true rabbits, and more 

 particularly the peculiarities of its sternum and clavicle, require 

 the erection of an independent genus for its reception. Hereto- 

 fore the genus Lepus has enjoyed the distinction of coincidence 

 in characters with the family to which it belongs. Now the 



