than 53;
interorbital breadth less than 16.
_Sylvilagus brasiliensis_, p. 141

12'. Tail of moderate length (more than 30) and
dingy gray; ear from notch (dry) more than
53; interorbital breadth more than 16
_Sylvilagus insonus_, p. 168

11'. Underside of tail distinctly white.

13. Total length more than 476; ear from notch
(dry) more than 64; interorbital breadth
usually more than 19.3; geographic range,
southwestern Mexico north of the Isthmus of
Tehuantepec.
_Sylvilagus cunicularius_, p. 169

13'. Total length less than 476; ear from notch
(dry) less than 64; interorbital breadth
usually less than 19.3; geographic range,
Canada to Panam['a]
_Sylvilagus floridanus_, p. 154

Genus ROMEROLAGUS Merriam--Volcano Rabbit

1896. _Romerolagus_ Merriam, Proc. Biol. Soc. Washington, 10:173,
December 29. Type, _Romerolagus nelsoni_ Merriam = _Lepus diazi_
Diaz.

Total length 300 to 311; tail rudimentary; hind foot, 52; ear from notch
(dry), 36; upper parts grizzled buffy brown or dull cinnamon brown;
underparts dingy gray; anterior projection of supraorbital process
absent; jugal projecting posteriorly past squamosal root of zygomatic
arch more than half way to external auditory meatus. The two cranial
characters mentioned are resemblances to pikas although the skull
otherwise resembles that of the true rabbits. The genus contains only
the one living species.

Living in well defined runways in the dense sacoton grass, these small
rabbits are mainly nocturnal and crepuscular, but sometimes are active
by day, especially in cloudy weather in the period of mating.

[Illustration: FIG. 6. Distribution of _Romerolagus diazi_.]

=Romerolagus diazi= (Diaz)

Volcano Rabbit

1893. _Lepus diazi_ Diaz, Catal. Com. Geogr['a]f.-Expl. Repub. Mex.
Expos. Internac. Columb. Chicago, pl. 42, March, 1893, type from
eastern slope of