172 Merriam — .1 New Rabbitfrom México. 



caudal vertebra 1 , the last three of which are upturned and rudi- 

 mentary. 



The fifth cervical vertebra is peculiar. Its transverse procesa 

 projects directly outward instead of backward, and its inferior 

 lamella has only a trace of the posterior extensión usual in rali- 

 hits. The metapophyses begin on the tenth dorsal vertebra and 

 are present inall the succeeding vertebra? to the last lumbar, in- 

 clusive. The anapophyses are much as in Lepus proper, being 

 present, tbough sinall, on the ninth totwelfth dorsals, inclusive, 

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

 The transverse processea of the lumbar vertebra? are peculiar, 

 each developing a broad posterior flange, which extends the full 

 length of the side of the vertebra. Hypopophyses are present 

 on the first, second, and third lumbar vertebra?, as in Lepus, 

 though relatively short. 



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

 important differences, sume of which may be mentioned here. 

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

 humeras is small and Hat instead of deeply sulcate ; thefibular 

 malleolus is less strongly developed ; the navicular bone differs 

 materially in form and its inferior crest is conspicuously shorter 

 than in Lepus, and «lies not reach forward beneáth the basi - 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 (subgenus Sylvilagus), but differs in the postorbital pro- 

 cesses, which are small. divergent posteriorly, and altogether 

 wanting anteriorly, and in thejugal, -which is greatly elongated 

 posteriorly. The interparietal is distinct, and in oíd 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 Lepus, 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 valué 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. Xow the 



