Reithrodontomys megalotis (Baird, 1858) . Mammalia in Repts. U.S. Expl. Surv., 8(1):451.

TYPE LOCALITY: Mexico-USA boundary region, between Janos, Chihuahua, and San Luis Springs, Grant Co., New Mexico .

DISTRIBUTION: SC British Columbia and SE Alberta, Canada; W and NC USA; south to N Baja California and through interior Mexico to central Oaxaca.

SYNONYMS: alticolus, amoles, arizonensis, aztecus, caryi, catalinae, cinereus, deserti, distichlis, dychei, hooperi, klamathensis, limicola, longicaudus, nebrascensis, nigrescens, pallidus, pectoralis, peninsulae, ravus, santacruzae, saturatus, sestinensis.

COMMENTS: Subgenus Reithrodontomys, megalotis species group. Formerly included R. zacatecae, which Hood et al. (1984) identified as a separate species. The substantial chromosomal variation reported (see Engstrom et al., 1981) cautions that other species may be lumped under R. megalotis . See Webster and Jones (1982a, Mammalian Species, 167).