_Z. princeps_ builds a gra.s.s nest on the ground which is placed under cover of vegetation or surface litter. Bailey (1932:227) writes that in New Mexico jumping mice of this species use fibers of gra.s.s to construct a ball-shaped nest. The nest usually has one opening but sometimes there are two. In the Ruby Mountains, of Nevada, Borell and Ellis (1934:37) found the globular nests of this mouse on the ground in tall gra.s.s.

=Zapus princeps cinereus= Hall

_Zapus princeps cinereus_ Hall, Univ. California Publ. Zool., 37:7, April 10, 1931.

_Type._--Female, adult, skin and skull; No. 45422, Mus. Vert. Zool.; Pine Canyon, 6600 feet alt.i.tude, Raft River Mountains, 17 mi. northwest Kelton, Boxelder County, Utah; obtained on July 14, 1930, by Annie M.

Alexander; original No. 689.

_Range._--Raft River Mt's in northwestern Utah and in isolated mountains in southern Idaho. See fig. 46. Zonal range: Transition and Canadian.

_Description._--Size, medium; back with broad mid-dorsal band, varying from pale brown mixed with Pinkish-Buff to dark brown mixed with Warm Buff or Ochraceous-Buff; sides varying from near Pinkish-Buff to near Ochraceous-Buff; ventral surface white to base of hairs, not suffused with other color; tail bicolored, pale brown above and white to yellowish-white below; ears dark, edged with white or yellowish-white; upper teeth divergent anteriorly; auditory bullae small; skull relatively long; zygomata relatively weak and not widely bowed; nasals wide posteriorly; pterygoid fossae relatively narrow.

_Comparisons._--From _Zapus princeps nevadensis_, _Z. p. cinereus_ differs as follows: Size averaging smaller; entire coloration lighter; zygomata not so widely bowed; incisive foramina not so wide posteriorly; auditory bullae smaller; nasals wider posteriorly; pterygoid fossae narrower.

From _Zapus princeps idahoensis_, _Z. p. cinereus_ can be distinguished by: generally paler color; smaller auditory bullae; broader interorbital region; anteriorly diverging tooth-rows; narrower pterygoid fossae.

For comparison with _Zapus princeps utahensis_ see account of that subspecies.

_Remarks._--Davis (1939:343) writes that "since _cinereus_ was described from nine specimens, only two of which are near adult, one cannot place much value on the coloration ascribed to it by Hall (1931:7)." I examined the type series and found, as did Davis (_loc. cit._), that the type is much lighter and grayer than is a near adult paratype, which was obtained the same day; however, I do not concur with Davis (_loc. cit._) that specimens from Mt. Harrison, 10 mi. S Albion, Idaho, which are darker and much more ochraceous than the paratype, necessarily are more nearly typically colored. These individuals, judged by cranial characters, are more nearly typical of _cinereus_ but show intergradation with _Z. p. idahoensis_ in their darker and more ochraceous pelage.

Durrant (1952:387) found that the gray color of _Z. p. cinereus_ was not diagnostic in separating _Z. p. cinereus_ from _Z. p. utahensis_, because gray animals are also found in _Z. p. utahensis_. Specimens from Camp Tendoy, Pocatello, Idaho, are intermediate in color and in cranial characters as between _Z. p. idahoensis_ and _Z. p. cinereus_, but here are referred to _Z. p. cinereus_. Whitlow and Hall (1933:268) compared these individuals with specimens of _Z. p. princeps_ and _Z. p.

cinereus_, finding them intermediate but in the aggregate of several differential characters better referred to the latter.

_Specimens examined._--Total, 35, distributed as follows:

IDAHO: _Bannock County_: Camp Tendoy, Pocatello, 2 (MVZ). _Ca.s.sia County_: Mt. Harrison, 10 mi. S Albion, 16 (MVZ).

UTAH: _Boxelder Co._: _south fork of George Creek, 5 mi. SE Yost, Raft River Mts., 6700 ft._, 1 (UU); _George Creek, 7 mi. SE Yost, Raft River Mts., 6500 ft._, 6 (UU); _Pine Canyon, 6600 ft., 17 mi. NW Kelton, Raft River Mts._, 8 (MVZ); Pine Creek, 3 mi. N Rosette, Raft River Mts., 6100 ft., 2 (UU).

_Marginal records._--Idaho: Camp Tendoy, Pocatello. Utah: Pine Creek, 3 mi. N Rosette, Raft River Mts., 6100 ft. Idaho: Mt. Harrison, 10 mi. S Albion.

=Zapus princeps curtatus= Hall

_Zapus princeps curtatus_ Hall, Univ. California Publ. Zool., 37:7, April 10, 1931.

_Zapus princeps oregonus_, Taylor, Univ. California Publ. Zool., 7:281, June 24, 1911.

_Type._--Female, adult, skin and skull, No. 7991, Mus. Vert. Zool.; head of Big Creek, 8000 feet alt.i.tude, Pine Forest Mountains, Humboldt County, Nevada; obtained on June 30, 1909, by Walter P. Taylor and C. H.

Richardson, original No. 777 of W. P. T.

_Range._--Pine Forest Mt's, Humboldt County, Nevada. See fig. 46. Zonal range: Transition and Canadian.

_Description._--Size medium; back pale near Light Ochraceous-Buff with admixture of black hair forming dark dorsal band; sides lighter than back; lateral line faintly indicated; ventral surface white; tail bicolored, grayish-white to yellowish-white below and pale brown above; ears dark, edged with yellowish-white; feet grayish-white above; palatal bridge short; tooth-rows almost parallel; mastoid region of skull relatively narrow; incisive foramina wide posteriorly; narrow across zygomata; nasals relatively narrow posteriorly.

_Comparisons._--For comparison with _Zapus princeps oregonus_ see account of that subspecies.

_Remarks._--This jumping mouse, which was described from the Pine Forest Mountains, closely resembles _Zapus princeps oregonus_ but differs in lighter color, slightly smaller body, less divergent tooth-rows, shorter palate, and narrower skull across the mastoid region.

The Pine Forest Mountains are isolated from neighboring boreal regions by a belt of the Upper Sonoran Life-zone, which is inhospitable to _Zapus_; therefore, intergrades between _Z. p. oregonus_ and _Z. p.

curtatus_ are not known and probably do not exist. Nevertheless, _Z. p.

curtatus_ shows close affinity with _Z. p. oregonus_, as indicated by Taylor (1911:281), and I agree with Hall (1931:7) that the relationships of _Z. p. curtatus_ are best expressed by arranging it as a subspecies of _Zapus princeps_.

_Specimens examined._--Total, 18, all from Nevada, distributed as follows: _Humboldt County_: Pine Forest Mts.; Alder Creek, 6000 ft., 2 (MVZ); head of Big Creek, 8000 ft., 14 (MVZ); _Leonard Creek, 6500 ft._, 2 (MVZ); Meadow, 1 (MVZ).

_Marginal records._--Nevada: Pine Forest Mts., Alder Creek; Meadow.

=Zapus princeps idahoensis= Davis

_Zapus princeps idahoensis_ Davis, Jour. Mamm., 15:221, August 10, 1931.

_Jaculus hudsonius_, Allen, Bull. Ess.e.x Inst., 6:61, April, 1874 (part--the part in Carbon County, Wyoming).

_Zapus hudsonius_, Merriam, N. Amer. Fauna, 5:72-73, July 30, 1891.

_Zapus princeps princeps_, Preble, N. Amer. Fauna, 15:22-23, August 8, 1899 (part).

_Type._--Male, adult, skin and skull; No. 54845, Mus. Vert. Zool.; 5 mi.

E Warm Lake, 7000 ft., Valley County, Idaho; obtained on July 9, 1932, by Robert T. Orr; original No. 660.

_Range._--From Banff, Alberta, southward through extreme southwestern Alberta and extreme southwestern British Columbia, most of the panhandle of Idaho, Kamiak b.u.t.te in eastern Washington, western Montana, and western Wyoming (Green, Wind River and Absoroka ranges of the Rocky Mt's). See fig. 46.

_Description._--Size, medium; back from near Clay Color to near Warm Buff, usually overlaid with black hairs forming broad dorsal band; sides lighter than back; lateral line indistinct or wanting; belly pure white, occasionally faintly tinged with Ochraceous-Buff; tail indistinctly bicolored, tan to grayish-white below and pale brown above; hind feet grayish-white above; ears dark, edged with white or yellowish-white; postpalatal notch anterior to posterior border of last molars; proximal part of inferior ramus of zygomatic process of maxillary relatively narrow and usually without enlarged median projection; auditory bullae well inflated; incisive foramina relatively narrow.

_Comparisons._--From _Zapus princeps kootenayensis_, _Z. p. idahoensis_ differs as follows: Size averaging larger; upper parts with greater suffusion of ochraceous, not grayish or dusty; skull larger; incisive foramina longer and relatively wider; zygomatic breadth averaging greater; nasals broader at tips; auditory bullae more inflated.

From _Zapus princeps oregonus_, _Z. p. idahoensis_ differs in: Size averaging smaller; upper parts generally more suffused with black hairs, on the average more yellowish with less ochraceous; skull smaller; incisive foramina narrower (breadth less, instead of more, than 52 per cent of length); palatal bridge shorter; zygomatic arch shorter; pterygoid fossae narrower.

From _Zapus princeps utahensis_, _Z. p. idahoensis_ can be distinguished by: Size less; color slightly darker; skull averaging smaller in zygomatic breadth, least interorbital constriction, and occipitonasal length; palate narrower; upper tooth-rows nearly parallel as opposed to diverging anteriorly.

From _Zapus princeps minor_, _Z. p. idahoensis_ differs in: Size larger; color of underparts less ochraceous; lateral line indistinct or wanting; skull averaging larger in all measurements taken except that the two subspecies are approximately same in least interorbital constriction, length of zygomatic arch, and distance from anterior face of incisors to postpalatal notch; nasals, in profile, straight instead of with proximal third depressed; postpalatal notch anterior to posterior face of last molar, instead of even with, or usually posterior to, same.

From _Zapus princeps saltator_, _Z. p. idahoensis_ differs as follows: Size averaging slightly larger; color darker, being less ochraceous and more yellow dorsally and laterally; auditory bullae more inflated; zygomatic arches less bowed laterally; incisive foramina narrower.

For comparison with _Zapus princeps princeps_ and _Zapus princeps cinereus_ see accounts of those subspecies.

_Remarks._--Intergradation occurs at almost all of the places where the range of _Z. p. idahoensis_ is known to touch that of any other geographic race. Nevertheless, each of the populations studied has characters which make this subspecies recognizable as a taxonomic unit, although its characters are not yet stabilized even in the central part of its range.

Among named subspecies of _Zapus princeps_, _Zapus p. idahoensis_ most closely resembles _Zapus princeps kootenayensis_, its nearest geographic neighbor to the north. Three specimens from 2 mi. NE Weippe, 3000 ft., Idaho, are best referred to _Z. p. idahoensis_ but show relationship to _Z. p. kootenayensis_ in size and shape of the tympanic bullae. The relationship of individuals from Idaho, here referred to _Z. p.

idahoensis_, from Glidden Lakes, Enaville, Cascade Creek, and 13 mi. E and 5 mi. N Coeur d'Alene, is discussed in the account of _Z. p.

kootenayensis_. British Columbian specimens from Newgate and Crows Nest Pa.s.s, 4450 ft., as well as Albertan specimens from Crows Nest Pa.s.s and various places in Waterton Lake Park, resemble _Z. p. kootenayensis_ in color but cranially are more nearly like _Z. p. idahoensis_.

Intergradation with _Zapus princeps oregonus_ was noted by Davis (1939:340) in a specimen from Cedar Mountain in Idaho. I have not seen this individual which he referred to _Z. p. idahoensis_ but have seen a specimen from the N Fork of Potlatch River (15 mi. SE Cedar Mt.), which, in color, closely resembles _Z. p. oregonus_ but cranially (shape of incisive foramina, size, and inflation of auditory bullae) is more nearly like _Z. p. idahoensis_ to which it is referred. Davis (_loc.

cit._) indicates that specimens from summit of Smith Mt., from 1 mi. N Bear Creek R. S., from 1/2 mi. E Black Lake, and from 3 mi. W Payette Lake, Idaho, are in an area of intergradation between _Z. p. oregonus_ and _Z. p. idahoensis_, but he referred them to _Z. p. idahoensis_ on the basis of cranial characters and length of hind foot. Seven specimens from Alturas Lake, 7000 ft., Idaho, were likewise so allocated by Davis (_loc. cit._). I concur with him and in addition refer the following intermediate individuals from Idaho to _Z. p. idahoensis_: New Meadow, 1; Warren, 1; Perkins Lake, 7000 ft., Sawtooth Nat'l Forest, 1; Prairie Creek, 12 mi. W Ketchum, 2400 ft., 3. All are more nearly like _Z. p.

oregonus_ in color but cranially they show more resemblance to _Z. p.

idahoensis_.