Peromyscus boylii (Baird, 1855) . Proc. Acad. Nat. Sci. Philadelphia, 7:335.

TYPE LOCALITY: USA, California, Eldorado Co., Middle Fork of American River, near Auburn .

DISTRIBUTION: California to westernmost Oklahoma, USA, south to Queretaro and W Hidalgo, Mexico.

SYNONYMS: gaurus, glasselli, major, metallicola, parasiticus, pinalis, robustus, rowleyi, utahensis.

COMMENTS: Many taxa previously arrayed as subspecies by Osgood (1909) or Hall (1981) have been elevated to species, including P. attwateri (see Schmidly, 1973«), P. aztecus (see Alvarez, 1961; Carleton, 1979; Hooper, 1968b), P. levipes (see Schmidly et al., 1988), P. madrensis (see Carleton, 1977; Carleton et al., 1982), P. simulus (see Carleton, 1977), and P. spicilegus (see Carleton, 1977). Others have been realigned with other species— cordillerae and evides under P. aztecus (Carleton, 1979); ambiguus, baetae, and sacarensis under P. levipes (Carleton, 1979; Schmidly et al., 1988); and penicillatus under P. difficilis (Diersing, 1976) . Chromosomal variation of P. boylii and its kin investigated by Houseal et al. (1987), Lee et al. (1972), and Schmidly and Schroeter (1974); biochemical variation by Avise et al. (1974«), Kilpatrick and Zimmerman (1975), Rennert and Kilpatrick (1986, 1987); morphological variation by Bradley and Schmidly (1987), Carleton (1977), and Schmidly et al. (1988). P. boylii species group.