_Dipodomys phillipsi ordi_, Coues and Allen, Monogr. North American Rodentia, p. 541, 1877 (part--the part from El Paso, Texas). _Dipodops ordii_, Merriam, N. Amer. Fauna, 4:42, October, 1890 (part--the part from El Paso, Texas). _Cricetodipus ordii_, Trouessart, Catalogus Mammalium, 1:581, 1897. _Perodipus ordi_, Elliot, Field Columbian Museum, Zool. Ser., 2:238, 1901. _Perodipus montanus richardsoni_, Bailey, N. Amer. Fauna, 25:144, October, 1905 (part--the part from Carlsbad, New Mexico). _Perodipus ordii_, Goldman, Proc. Biol. Soc. Washington, 30:113, May 23, 1917. _Type._--None designated. Species characterized from specimens obtained by Dr. Woodhouse at El Paso, Texas. _Range._--Southeastern Arizona, southern New Mexico, western Texas and north-central Mexico; marginal occurrences are: in Arizona, 20 mi. NE Calva, Oracle and Calabasas; in Sonora, Nogales; in Chihuahua, Casas Grandes, Corralitos and Santa Rosalia; in Texas, 16 mi. E Van Horn and 30 mi. N Van Horn; in New Mexico, 40 mi. N Roswell, 40 mi. SE Corona and Mangos Valley. _Diagnosis._--Size small (see measurements). Color dark, entire dorsal surface (16'') between Pinkish Cinnamon and Cinnamon-Buff, purest on sides and flanks, upper parts suffused with black; arietiform markings, pinnae of ears, plantar surfaces of hind feet, dorsal and ventral stripes of tail, brownish-black. Skull of medium size; rostrum narrow and relatively long; braincase flattened; auditory bullae but slightly inflated; zygomatic arches slender and straight; upper incisors short and narrow. _Comparisons._--From _Dipodomys ordii richardsoni_, _D. o. ordii_ differs as follows: Size smaller; color somewhat lighter; dorsal and ventral stripes of tail brownish instead of blackish; skull smaller in all measurements taken. From _Dipodomys ordii montanus_, _D. o. ordii_ differs in: Size smaller; color lighter; skull narrower across bullae and rostrum; wider interorbitally; all other measurements taken the same, thus imparting to the skull, in dorsal view, a longer, narrower appearance. From _Dipodomys ordii chapmani_, _D. o. ordii_ differs in: Size smaller; color lighter; skull smaller; zygomatic arches narrower at suture of jugal and zygomatic process of maxillary; rostrum narrower; upper incisors smaller; nasals shorter; least interorbital width less. For comparisons with _Dipodomys ordii sennetti_ and _Dipodomys ordii compactus_ see accounts of those subspecies.