22 NORTH AMERICAN FAUNA. 



ZAPUS PRINCEPS Allen. Rocky Mountain Jumping Mouse. 



(PI. I, figs. 6, 6a.) 

 Zapus princeps J. A. Allen, Bull. Am. Mus. Nat. Hist., N. Y., V, p. 71, April 28, 1893. 



Type locality. Florida, La Plata County, Colo. 



Geographic distribution. Rocky Mountain region from northern New 

 Mexico northward to Henry House, Alberta. 



General characters. Size large; skull broad and heavy, much as in 

 Z. hudsonius, but much larger. 



Color. Summer pelage: "Above with the middle of the dorsal region 

 pale yellowish brown, profusely mix< d with blackish, so that sometimes 

 the blackish color, sometimes the pale yellowish brown, predominates; 

 sides of the body, forming a band on either side about equal to the 

 dark dorsal area, yellowish brown, slightly mixed with blackish, except 

 over a narrow lateral line, adjoining the white of lower parts, which is 

 a clear, strong yellowish brown; lower parts white to the base of the 

 hairs, varying in some specimens to strong ochraceous; tail indistinctly 

 bicolor grayish white below and pale brown above, and very thinly 

 haired; hind feet grayish white above like the lower surface of the 

 tail; ears narrowly edged with yellowish white." 1 In fall pelage adults 

 have the dorsal area with more black and sides more yellowish than in 

 summer; under parts pure white; immature in same pelage similar, 

 but with dorsal area more suffused with yellowish ; under parts some 

 what suffused with color of sides. 



Cranial characters. Skull large and heavy, with rather heavy denti- 

 tion. In some specimens the premolar is very small, occasionally being 

 flattened against the adjacent tooth and scarcely functional. Imma- 

 ture skull short and broad, with large brain case. The incisive foramina 

 in this and closely related species much larger than in those more nearly 

 i elated to Z. hudsonius. 



Measurements. Average of 7 specimens from Fort Garland, Colo. : 

 Total length, 245; tail vertebrae, 147 ; hind foot, 32. Average of 4 from 

 La Barge Creek, Wyo.: Total length, 239; tail vertebra, 150; hind 

 foot, 32. Average of 6 from St. Mary Lake, Mont, : Total length, 232; 

 tail vertebrae, 139; hind foot, 32. Skull: Average of 2 adult skulls 

 from Fort Garland, Colo. : Basilar length , 20.7 ; zy gomatic breadth, 12.5 ; 

 mastoid breadth, 11; interorbital constriction, 45; incisor to post- 

 palatal notch, 9.8; foramen magnum to postpalatal notch, 8.8; fronto- 

 palatal depth at middle of molar series, 6.6. One from Preuss Moun- 

 tains, Idaho: Basilar length, 20.5; zy gomatic breadth, 13.2; mastoid 

 breadth, 11; interorbital constriction, 4.8; incisor to postpalatal notch, 

 9.8; foramen magnum to postpalatal notch, 8.8; fron to palatal depth 

 at middle of molar series, 6.5. 



General remarks. Zapus princeps is one of the largest species of 

 the genus and has the widest range of any except Z. hudsonius. It 

 is mostly confined to mountains, though northward its range extends 



'From original description in Bull. Am. Mus. Nat. Hist., N. Y., V, p. 71, 1893. 



