e associated
in the popular mind with rabbits than with other kinds of mammals.
Actually, many kinds of mammals are quite as likely to have tularemia as
are rabbits. Now that streptomycin is available, cases of tularemia in
persons are easily cured.

KEY TO SPECIES OF THE GENERA SYLVILAGUS AND ROMEROLAGUS

1. Antorbital extension of supraorbital process more than 1/2 length of
posterior extension; first upper cheek-tooth with only one
re-entrant angle on anterior face; re-entrant angle of second upper
cheek-tooth not crenate
_Sylvilagus idahoensis_, p. 139

1'. Antorbital extension of supraorbital process less than 1/2 of
posterior extension or entirely absent; first upper cheek-tooth with
more than one (usually 3) re-entrant angles on anterior face;
re-entrant angle of second upper cheek-tooth crenate.

2. Anterior extension of supraorbital process absent (or if a point is
barely indicated, then 5/6 or all of posterior process fused to
braincase).

3. Tympanic bulla smaller than foramen magnum; hind foot more than
74; geographic range wholly in United States.

4. Ear more than 58 from notch in dried skin; basilar length of
skull more than 63
_Sylvilagus aquaticus_, p. 166

4'. Ear less than 58 from notch in dried skin; basilar length of
skull less than 63.

5. Underside of tail white; posterior extension of supraorbital
process tapering to a slender point, this point free of
braincase or barely touching it and leaving a slit or long
foramen
_Sylvilagus transitionalis_, p. 160

5'. Underside of tail brown or gray; posterior extension of
supraorbital process always fused to skull, usually for
entire length but in occasional specimens there is small
foramen at middle of posterior extension of supraorbital
process
_Sylvilagus palustris_, p. 147

3'. Tympanic bulla as large as foramen magnum; hind foot less than
74; geographic range limited to southern edge of Mexican
tableland at high elevations
_Romerolagus diazi_, p. 138

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