1. _D. o. richardsoni_ 2. _D. o. oklahomae_ 3. _D. o. compactus_ 4. _D. o. sennetti_ 6. _D. o. medius_ 7. _D. o. obscurus_ 14. _D. o. ordii_ 16. _D. o. extractus_ 23. _D. o. idoneus_ 29. _D. o. attenuatus_ 30. _D. o. fuscus_ 31. _D. o. longipes_ 35. _D. o. palmeri_ ] =Dipodomys ordii terrosus= Hoffmeister _Dipodomys ordii terrosus_ Hoffmeister, Proc. Biol. Soc. Washington, 55:165, December 31, 1942. _Dipodomys phillipsi ordi_, Coues and Allen, Monogr. North American Rodentia, p. 541, August, 1877 (part--the part from Yellowstone River, Montana). _Perodipus montanus richardsoni_, Cary, N. Amer. Fauna, 49:124, December, 1926 (part--the part from Glendive, Montana). _Type._--Male, no. 93477, Mus. Vert. Zool., Univ. California; Yellowstone River, 5 mi. W Forsyth, 2,750 ft., Rosebud County, Montana; obtained on June 2, 1940, by J. R. Alcorn, original no. 1528. _Range._--Extreme southwestern Saskatchewan and southeastern Alberta, eastern half of Montana, northern Wyoming and probably extreme western North Dakota; marginal localities are: 50 mi. W Swift Current, Saskatchewan; "near Medicine Hat," Alberta; in Wyoming, Sheep Creek, and 23 mi. SW Newcastle; in Montana, Medicine Rocks (14 mi. NE Ekalaka), and Glendive. _Diagnosis._--Size large (see measurements). Color dark, entire dorsal surface near (_c_) Ochraceous-Buff, purest on sides and flanks; upper parts mixed with black; arietiform markings, pinnae of ears, dorsal and ventral stripes of tail and plantar surfaces of hind feet brownish-black. Skull large; rostrum short, wide and deep; braincase slightly vaulted; auditory bullae markedly inflated ventrally; zygomatic arches heavy and bowed laterad; upper incisors long and robust. _Comparisons._--From _Dipodomys ordii priscus_, _D. o. terrosus_ differs as follows: Size larger in all measurements taken, except for length of hind feet, which is less; color darker in all pigmented areas; skull larger in all parts measured except width of interparietal, which is less; auditory bullae more inflated ventrally; zygomatic processes of maxillae wider; rostrum deeper and shorter. From _Dipodomys ordii richardsoni_, _D. o. terrosus_ differs as follows: Size larger; color darker in all pigmented areas; ventral stripe of tail extending farther distally; skull larger except in width across auditory bullae, which is the same. For comparison with _Dipodomys ordii luteolus_ see account of that subspecies. _Remarks._--As noted in the comparisons, _D. o. terrosus_ is larger and darker than _D. o. priscus_, _D. o. luteolus_ or _D. o. richardsoni_, its closest geographic neighbors, and does not resemble any of them, but rather resembles _D. o. longipes_ and _D. o. evexus_ in size and appearance, both of which are distantly removed geographically.