32 NORTH AMERICAN FAUNA. 



Color. Fall pelage: Sides yellowish, moderately lined with black- 

 tipped hairs; dorsal area well-defined, rather dark, and thickly flecked 

 with yellowish ; ears like back, narrowly edged with yellowish ; beneath. 

 pure white; tail dusky above and gray beneath. Compared with Z. 

 trinotatus in corresponding pelage, the back is slightly darker, the tail 

 darker above, and gray, instead of yellowish-white beneath. 



Cranial characters. Compared with Z. trinotattis, the skull of Z. sal- 

 tator differs as follows : Brain case narrower; zygomatic breadth con- 

 siderably less; nasals broader posteriorly. Compared with skulls of 

 Z. princeps from Field and Glacier, British Columbia, and Heniy House, 

 Alberta, the skull of Z. saltator has the rostrum longer; palate from 

 incisive foramina to postpalatal notch shorter; and molars, especially 

 last upper, smaller. All of the skulls of Z. saltator examined agree 

 very well among themselves, and all have the incisive foramina very 

 large and broad posteriorly. The zygomatic expansion is small and 

 the brain case high and narrow. 



Measurements. An adult from Port Simpson, British Columbia, 

 measures : Total length, 245; tail vertebrae, 145 ; hind foot, 32. Average 

 of five young adults from same locality: Total length, 234; tail verte- 

 brae, 151; hind foot, 32. 'Skull: An adult skull from Port Simpson, 

 British Columbia, measures: Basilar length, 20; zygomatic breadth, 

 11.8; rnastoid breadth, 10.5; interorbital constriction, 4.5; incisor to 

 postpalatal notch, 9.4; foramen magnum to postpalatal notch, 8; fron to- 

 palatal depth at middle of molar series, 6.4. 



General remarks. Zapus saltator is a well-marked form, differing con- 

 siderably from its relatives to the southward. With Z. hudsonius alas- 

 censis, which probably meets it on the north, it requires no comparison, 

 the immensely larger incisive foramina and larger molars of the pres- 

 ent species distinguishing the two forms at a glance. A small series 

 of Z. saltator^ which forms the basis of the present description, was 

 taken by the writer at Port Simpson, British Columbia, in August, 

 1897. Some of these were taken in a grassy thicket near the edge 

 of the forest, a few feet above high-water mark, and the remainder in 

 a garden in the village. Z. saltator may be found to intergrade with 

 either Z. trinotatus or Z. princeps (it seems nearer the latter), but until 

 its true relationship is proved it seems best to allow it full specific rank. 

 The tail is longer and the hind foot shorter, relatively, than in Z. trino- 

 tatus. Through the kindness of Dr. J. A. Allen, J have been enabled 

 to examine the type of Z. saltator. The skull of the type being imper- 

 fect, the cranial characters given above are taken from Port Simpson 

 specimens. 



Specimens examined. Total number, 8, from the following localities : 



Northwest Territory: Telegraph Creek, 1 (the type). 



British Columbia: Inverness (mouth of Skeena River), 1 ; Port Simpson, 6. 



