_Zapus hudsonius preblei_, on the basis of 11 specimens, agrees most closely in size and color with _Z. h. campestris_; there is much less resemblance between _Z. h. preblei_ and _Z. h. pallidus_. An adult from Springhill, 12 mi. N Laramie Peak, is typically _Z. h. preblei_ as is one from Cheyenne. Although specimens of _Z. h. preblei_ are few (4 adult, 7 non-adults), the differences between this and neighboring named kinds is considerable. _Specimens examined_: Total, 11, distributed as follows: COLORADO: _Boulder County_: 3 mi. E Boulder, 1 (UCM); _5 mi. E Boulder_, 1 (UCM); _south of Boulder_ (no exact locality), 1 (UCM). _Jefferson County_: Semper, 1. _Larimer County_: Loveland, 2 (USBS). WYOMING: _Albany County_: Springhill, 12 mi. N Laramie Peak, 6300 ft., 3 (USBS). _Laramie County_: Cheyenne, 1 (USNM). _Platte County_: Chugwater, 1 (Clev. MNH). _Marginal records._--Wyoming: Springhill, 12 mi. N Laramie Peak, 6300 ft.; Chugwater; Cheyenne. Colorado: Loveland; Semper. =Zapus hudsonius tenellus= Merriam _Zapus tenellus_ Merriam, Proc. Biol. Soc. Washington, 11:103, April 26, 1897. _Zapus hudsonius tenellus_, Hall, Univ. California Publ. Zool., 40:377, November 5, 1934. _Zapus hudsonius hudsonius_, Baker, Univ. Kansas Publ., Mus. Nat. Hist., 5:111, November 28, 1951 (part--the part from E side Minaker River, 1 mi. W Trutch and 3 mi. N Fort St. John, British Columbia). _Type._--Female, young adult, skin and skull, No. 66932 U. S. Nat. Mus., Biol. Surv. Coll.; Kamloops, British Columbia; obtained on August 25, 1894, by Clark P. Streator, original No. 4196. _Range._--British Columbia. See fig. 47. Zonal range: Canadian and Hudsonian. _Description._--Size medium; back from near Clay Color (brighter) to near Cinnamon-Buff with admixture of black tipped hairs forming a weakly defined dorsal band; sides lighter than back from near dull Ochraceous-Buff to near Cinnamon-Buff frequently with admixture of dark-tipped hairs; lateral line usually distinct, of clear Ochraceous-Buff; belly white sometimes with slight suffusion of Ochraceous-Buff; tail bicolored, brownish to brownish-black above, white or grayish-white to yellowish-white below; ears dark, edged and flecked on inner surface with color of sides; feet grayish-white above; auditory bullae relatively narrow, moderately inflated, elongate when viewed from below, anterior edge slightly concave; incisive foramina relatively short; braincase relatively narrow; vertical depth of skull at junction of frontals and nasals relatively great; nasals relatively narrow; pterygoid fossae moderately broad; zygomata relatively short. _Comparisons._--For comparisons with _Zapus hudsonius hudsonius_ and _Zapus hudsonius alascensis_ see accounts of those subspecies.