Mount Ixtaccihuatl, Puebla.

1911. _Romerolagus diazi_ Miller, Proc. Biol. Soc. Washington,
24:228, October 31, 1911.

1896. _Romerolagus nelsoni_ Merriam, Proc. Biol. Soc. Washington,
10:173, December 29, 1896, type from west slope Mount
Popocatepetl, 11,000 feet, M['e]xico.

_Range._--Canadian Life-zone of the mountains bounding the eastern,
southern and western sides of the Valley of Mexico. _Marginal
records._--M['e]xico: Monte R['i]o Fr['i]o, 45 km. ESE Mexico City (Davis,
1944:401). Puebla: type locality. M['e]xico: Mt. Popocatepetl (Nelson,
1909:280). Distrito Federal: 31 km. S Mexico City (30815 KU). M['e]xico:
Llano Grande, 3 km. W Tlalmanalco (28278 KU).

Genus SYLVILAGUS Gray--Cottontails and Allies

Revised by Nelson, N. Amer. Fauna, 29:58-158, August 31, 1909.

1867. _Sylvilagus_ Gray, Ann. and Mag. Nat. Hist., 20 (ser. 3):221.
Type, _Lepus sylvaticus_ Bachman, _Lepus nuttalli mallurus_
Thomas.

Total length, 291-538; tail, 18-73; hind foot, 71-110; ear from notch
(dry) 41-74. Grayish to dark brownish above and lighter below; sutures
of interparietal bone distinct throughout life; second to fourth
cervical vertebrae broader than long with dorsal surface flattened and
without carination.

The delectable flesh of members of this genus, the large numbers that
occur on a small area, even in thickly settled rural areas, and the
wariness that rabbits soon develop when much hunted, give them top
ranking among small game mammals. Tens of thousands of cottontails in
Kansas and Missouri (_Sylvilagus floridanus_ and some _S. audubonii_)
are captured alive, transported to the eastern United States and
released there to bolster the local supply of game. Considering that
certain ectoparasites are limited to certain hosts and that some
ectoparasites transmit such diseases as Rocky Mountain Spotted Fever
whereas other ectoparasites do not, this transplantation of rabbits is
dangerous. Also, expenditure of $100.00 on improving the habitat for
_Sylvilagus_ in a given area in the eastern United States would produce
more cottontails than the expenditure of the same sum for live animals,
from the Middlewest, that are to be released (see Langenbach and Beule,
1942:14, 15 and 30).

Different species venture different distances from cover to feed. The
Audubon cottontail of west-central California ventures a hundred feet
and more from cover but the brush rabbit was never seen (