_Comparisons._--From _Dipodomys ordii columbianus_, _D. o. monoensis_ differs as follows: Size larger; color lighter; skull larger; rostrum longer and narrower; interorbital region narrower; breadth across auditory bullae less; lacrimal processes larger; braincase less vaulted; auditory bullae more inflated ventrally; pterygoid fossae smaller; zygomatic arches more robust; cutting edge of upper incisors wider. From _Dipodomys ordii fetosus_, _D. o. monoensis_ differs in: Hind foot shorter; color lighter; skull smaller; rostrum shorter and narrower; interorbital width less; interparietal region larger; lacrimal processes smaller; auditory bullae less inflated. For comparison with _Dipodomys ordii inaquosus_ see account of that subspecies. _Remarks._--This subspecies retains all of its diagnostic characters throughout nearly all parts of its geographic range. Intergradation occurs in animals from the southern end of Pyramid Lake, Big Smoky Valley and near Toquima Peak, Nevada; these animals, although typical of _D. o. monoensis_ in coloration, resemble _D. o. columbianus_ cranially. Three-way intergradation between _D. o. columbianus_, _D. o. fetosus_ and _D. o. monoensis_ is noted in animals from east-central Nye County, Nevada. These animals resemble _D. o. monoensis_ in size, _D. o. fetosus_ in color and resemble _D. o. columbianus_ in certain cranial features. These animals are referred to _D. o. monoensis_. Animals from Toulon, Nevada, in the inflation of the auditory bullae, the vault of the braincase, the color and the total length show intergradation with _D. o. inaquosus_ but are referable to _D. o. monoensis_. _Specimens examined._--Total, 264, distributed as follows: =California=: _Mono County_: Pellisier Ranch, 5 mi. N Benton Station, 17 (7 DRD; 10 MVZ); Benton, 5639 ft., 2 (1 LACM; 1 MVZ); Taylor Ranch, 2 mi. S Benton Station, 5300 ft., 2 (MVZ). _Inyo County_: Deep Springs Valley, 1 (LACM).