d with hairs colored like back; feet
white; tail scaly in appearance, indistinctly bicolored with
short dark hairs above and short pale hairs below; skull
without beaded or ridged supraorbital border; rostrum
expanded anteriorly with sides almost parallel; teeth with
strongly developed outer accessory cusps on the first and
second upper molar teeth; anteriormost loph
(parastyle-protoconule of Goldman, N. Amer. Fauna, 43:11,
September 23, 1918) of the first upper molar large, almost
as broad as greatest breadth of tooth.

_Comparisons._--_Peromyscus ochraventer_ has been compared
with _P. difficilis_ (specimens from Veracruz), _P. boylei_
(Veracruz), _P. banderanus_ (Guerrero), _P. mexicanus_
(Veracruz), _P. furvus_ (Veracruz), and _P. latirostris_
(San Luis Potosi). From _P. difficilis_, _P. ochraventer_
differs in having underparts distinctively brownish, rostrum
expanded anteriorly with sides almost parallel, anteriormost
loph of the first upper molar larger, and auditory bulla
smaller. From _P. boylei_, _P. ochraventer_ differs in
having underparts distinctively brownish, tail less
distinctly bicolored, rostrum expanded anteriorly with sides
almost parallel, and anteriormost loph of the first upper
molar larger. From _P. banderanus_, _P. ochraventer_ differs
in having underparts distinctively brownish, tail less
distinctly bicolored, rostrum expanded anteriorly with sides
almost parallel, anteriormost loph of the first upper molar
larger, auditory bulla smaller, and in lacking a beaded or
ridged supraorbital border. From _P. mexicanus_, _P.
ochraventer_ differs in having underparts distinctively
brownish, tail not irregularly blotched with dusky, rostrum
expanded anteriorly with sides almost parallel, anteriormost
loph of the first upper molar larger, and in lacking a
beaded or ridged supraorbital border. From _P. furvus_ and
_P. latirostris_, _P. ochraventer_ differs in being smaller,
having underparts distinctively brownish, tail not
irregularly blotched with dusky, rostrum proportionately
shorter, and interpterygoid space relatively narrower.

_Remarks._--_Peromyscus ochraventer_ is considered to be a distinct
species showing little evident relationship with other Mexican
_Peromyscus_. In the shape of the skull, especially the anteri