Comparison with Dipodomys ordii evexus is made in account of that subspecies.
Remarks.—This animal is apparently not abundant at any place in its range. Two different attempts, by me, to obtain topotypes were unsuccessful. A single specimen was obtained and that was only a skull saved from a mutilated animal that was taken away from a rattlesnake. The habitat at the type locality is such that a person would not expect it to be inhabited by kangaroo rats. The soil is a heavy clay with a generous admixture of stones but in isolated spots there are light sandy soils which should be suitable for kangaroo rats. Even so, 500 traps set in the area of the type locality over a period of two nights yielded no Dipodomys.
This subspecies of Dipodomys ordii, inhabiting west-central Colorado and southeastern Utah, is darker than any other subspecies with which its range comes in contact. The races to both the north and south are larger, with the exception of the hind foot which is longer in D. o. nexilis than in either D. o. sanrafaeli or D. o. longipes. The affinities of D. o. nexilis are with D. o. longipes rather than with any of the other known subspecies of Dipodomys ordii.
Intergradation between D. o. nexilis and D. o. longipes is shown by animals from Bluff, San Juan County, Utah, which, however, are referable to the latter. In animals from sixteen miles northwest of Moab, Grand County, Utah, there is intergradation in size of skull and in color between D. o. nexilis and D. o. sanrafaeli. The specimens are referred to D. o. sanrafaeli.
D. o. nexilis is apparently prevented from extending its range to the northward by the presence there of D. o. sanrafaeli. To the south D. o. nexilis encounters D. o. longipes and the San Juan River. To the east it is limited by the Rocky Mountains and to the west by the deep canyons of the Colorado River.
[Warren] (1942:183) did not apply the name D. o. nexilis to Ord kangaroo rats in Colorado. He listed specimens from Montrose, Montezuma and Mesa counties as being referable to D. o. longipes. The specimens from Montezuma County, Colorado, probably are D. o. longipes and those from Montrose and Mesa counties (for which [Warren] gives no precise localities) are D. o. nexilis.
Specimens examined.—Total, 35, distributed as follows:
Utah: Grand County: Cisco, 4 (CM); 18 mi. NE Moab, 6000 ft., 1 (UU). San Juan County: 15 mi. N Monticello, 4 (MVZ); Blanding, 1 (UU).
Colorado: Delta County: Hotchkiss, 1 (USBS). Montrose County: Paradox, 1 (DRD); Bedrock, 4 (AMNH); 5 mi. W Naturita, 2 (USBS); Coventry, 3 (1 USBS; 2 AMNH).