16 NORTH AMERICAN FAUNA. 



Color. Summer pelage : Fur of entire upper parts plumbeous at base, 

 with tips of hairs ranging from yellowish fawn to rather dark ochra- 

 ceous, rather thickly necked with black-tipped hairs; broad dorsal, 

 stripe reaching from upper part of face to base of tail much darker than 

 remainder of upper parts, the black-tipped hairs predominating; tail 

 rather sharply bicolor, grayish brown above and whitish beneath ; lower 

 parts white, sometimes suffused with color of sides; feet white. Fall 

 pelage: Ochraceous of sides duller and more yellowish, encroaching 

 more on the dark dorsal area, which is sometimes almost obliterated. 

 Young of the year with more ochraceous in fall pelage than the adults, 

 and a greater tendency to fulvous wash on lower parts. 



Cranial characters. Skull rather lightly built, with rather narrow 

 brain case, small incisive foramina, and small molars; zygomata not 

 widely spreading; rostrum not appreciably deflected. 



Measurements. Two specimens from James Bay, Canada, measured 

 from alcohol, average: Total length, 209; tail vertebrae, 124; hind foot, 

 30.5. Eleven from Tower, Minn., average: Total length, 218; tail ver- 

 tebrae, 133 ; hind foot, 30.2. Thirty- four adults from Keene Valley, Essex 

 County, N. Y., average : l Total length, 216.6 ; tail vertebrae, 129.25 ; hind 

 foot, 31.25. Skull: An adult skull from James Bay measures: Basilar 

 length, 18.5; zygomatic breadth, 11; mastoid breadth, 10; iuterorbital 

 constriction, 4.2; incisor to postpalatal notch, 8.5; foramen magnum to 

 postpalatal notch, 8; fronto-palatal depth at middle of molar series, 6.5. 

 An adult ? from Ossipee, N. H., measures: Basilar length, 18.8; zygo- 

 matic breadth, 11.6; mastoid breadth, 10; interorbital constriction, 4.3; 

 incisor to postpalatal notch, 8.6; foramen magnum to postpalatal notch, 

 8.2; frou to-palatal depth at middle of molar Aeries, 6.2. 



General remarks. Zapus hudsonius, the type of the genus, was until 

 recently the only well established species. The foregoing list of 

 synonyms indicates that it attracted the attention of many naturalists 

 during the early part of the century, all the names published previous 

 to 1856 referring almost exclusively to it. Jaculus hudsonius of Baird 

 (= Zapus hudsonius Coues) is a composite species including nearly a 

 dozen forms now recognized as distinct. The distribution of hud- 

 sonius^ including its four well-marked subspecies, is by far the most 

 extensive in the genus, few North American rodents equaling it in 

 this respect. 



The only specimens of Zapus from Hudson Bay at present available 

 are four alcoholic examples, in rather poor condition, from James Bay, 

 and a part of a skin from Fort Churchill, Northwest Territory. This 

 skin has evidently been in alcohol, and hence its color can not be 

 depended upon. I have removed several skulls from the James Bay 

 specimens, including one perfect adult. Since this skull agrees essen- 

 tially with skulls from Tower, Minn., from which place the Biological 

 Survey has a large series, these specimens have been assumed to be 



i Fide Batchelaer. 



