esignate a type or type locality. Osgood (1909:157) designated as
lectotype the mounted specimen, in the Geneva Museum, which has the
skull inside and of which Saussure figured the molar teeth. Osgood
(_loc. cit._) examined one of the three specimens (No. 3926 USNM) that
Saussure used in describing _P. aztecus_ and found that it agreed "in
every respect with recently collected specimens from Mirador, Veracruz,
which, in the lack of exact knowledge, may be assumed to be the type
locality, as it is certain that some at least of Saussure's specimens
were taken near there."

[Illustration: FIG. 1. Two species of _Peromyscus_.
1. _P. boylii ambiguus_
2. _P. boylii beatae_
3. _P. boylii levipes_
4. _P. aztecus_ (triangles)]

Osgood regarded _P. aztecus_ as a subspecies of _P. boylii_ because of
the resemblance between _aztecus_ and _P. b. evides_, but _evides_ is
far removed geographically (occurring only in western Mexico) from
_aztecus_, and is smaller. _P. aztecus_ is larger than any known
subspecies of _P. boylii_, and is not known to intergrade with _P. b.
levipes_ or _P. b. beatae_ (with which _aztecus_ occurs sympatrically at
Jalapa, Veracruz), the two subspecies of _boylii_ that are found nearest
the geographic range of _P. aztecus_. Also, as mentioned previously,
_aztecus_ possesses distinctive characters that distinguish it from all
subspecies of _boylii_. For these reasons I regard _aztecus_ as a
distinct species.

According to Hall and Kelson (1959:634), _P. aztecus_ occurs in San Luis
Potosi, Hidalgo, and west-central Veracruz, but their map 364 is based
on the records of Osgood (1909:158) and Dalquest (1953:143). I have
examined all the specimens reported by the two authors last named and
find that those from San Luis Potosi are _P. boylii levipes_.

The diagnosis and comparisons here presented of _aztecus_ were based on
specimens from Mirador in comparison with all the specimens of _P.
boylii_ from eastern Mexico listed beyond. The largest specimens of _P.
boylii_ that I have examined are from Las Vigas, Veracruz, and
localities within a radius of five kilometers thereof. Some measurements
of these large specimens of _P. boylii_ overlap those of _P. aztecus_
but the two kinds of mice differ greatly in characters of the skull, in
color, and in length of tail.

The specimens (three adults and three juveniles) from Huachinango,
Puebla, are slightly darker than specimens from Mirador but do n