Peromyscus nasutus (J. A. Allen, 1891) . Bull. Amer. Mus. Nat. Hist., 3:229.

TYPE LOCALITY: USA, Colorado, Latimer Co., Estes Park .

DISTRIBUTION: C Colorado and SE Utah, south through New Mexico and Transpecos, Texas, USA, to NW Coahuila, Mexico.

SYNONYMS: griseus, penicillatus .

COMMENTS: Considered a distinct species (Osgood, 1909) until synonymized under P. difficilis by Hoffmeister and de la Torre (1961). Recognized as a sibling species separate from P. difficilis by Zimmerman et al. (1975, 1978). Includes penicillatus, which Osgood (1909) had misclassified under P. boylii (see Diersing, 1976). P. truei species group.