_Cotypes._--Male, no. 2400, and female, no. 2398, Amer. Mus. Nat. Hist.; Fort Verde, Yavapai County, Arizona; obtained on January 26, 1887, and October 1, 1885, respectively, by Edgar A. Mearns. (Type not seen.) _Range._--Central Arizona from the Grand Canyon of the Colorado River, southeastward to, and probably beyond, Fort Verde; marginal occurrences are: lower end Prespect Valley, Kirkland, Prescott, Camp Verde, Bill Williams Mountain. _Diagnosis._--Size medium (see measurements). Color dark; entire dorsal surface between (_10''_) Pinkish Cinnamon and Cinnamon-Buff, purest on sides and flanks, upper parts strongly suffused with black; arietiform markings, pinnae of ears, plantar surfaces of hind feet, dorsal and ventral stripes of tail, blackish. Skull medium in size; rostrum long and narrow; nasals long; auditory bullae slightly distended; braincase vaulted. _Comparisons._--For comparisons with _Dipodomys ordii cupidineus_, _Dipodomys ordii longipes_ and _Dipodomys ordii ordii_ see accounts of those subspecies. _Remarks._--This subspecies of _Dipodomys ordii_ is relatively isolated from other subspecies of the species. The Colorado River with its deep canyons is interposed between the ranges of _D. o. chapmani_ and _D. o. cupidineus_. A high range of mountains separates _D. o. chapmani_ from the range of _D. o. longipes_. The only race with which _D. o. chapmani_ probably comes into contact is _D. o. ordii_ to the southeast. No specimens are available from the southeastern part of the range of _D. o. chapmani_. Animals from the northwestern part of the range of _D. o. ordii_, without exception, have dark-colored pelage which is characteristic of _D. o. chapmani_. In the shape of the nasals, vault of the braincase, interorbital width and auditory bullae, animals from Rice, Arizona, resemble _D. o. chapmani_, but in other characters resemble _D. o. ordii_ to which subspecies they are referred. Animals from 20 miles northeast of Calva, Arizona, are dark-colored and are intermediate between the dark _D. o. chapmani_ and the pale _D. o. ordii_ in size of the cranium and body but are referable to _D. o. ordii_. In the northwestern part of the range of _D. o. chapmani_ the animals are not typical in that they have a shorter, wider rostrum and a heavier zygomatic arch than topotypes. _Specimens examined._--Total, 90, all from Arizona, distributed as follows: _Mohave County_: lower end Prospect Valley, 4500 ft., Grand Canyon, 7 (USBS); Kingman, 9 (LACM). _Coconino County_: Aubrey Valley, 10 mi. S Pine Spring, 4 (USBS); Bill Williams Mountain, 1 (USNM). _Yavapai County_: 3 mi. N Fort Whipple, 11 (USBS); Fort Whipple, 4 (2 USBS; 2 USNM); Willow Creek, 4 mi. N Prescott, 4 (MVZ); 1 mi. W Camp Verde, 1 (MVZ); Camp Verde, 33 (15 USBS; 3 MVZ; 3 AMNH; 9 LACM; 3 DRD); 1/2 mi. S Camp Verde, 4 (MVZ); Kirkland, 9 (USBS); Turkey Creek, 3 (USBS).