798 



MONOORAPITS OF NORTH AMERICAN RODENTIA. 



localitios, as well as with the detailed descriptions giren by authors of the 

 Old World form. P'iXamples from Fort Resolution, Fort Rae, Fort Liard. 

 Fort Simpson, and Nelson's and Mackenzie Rivers are much paler than 

 those from the region more to the southward, with less rufous edging to the 

 black stripes of the back (many of them being quite without such edging, 

 just us in Siberian examples) and less rufous on the sides of the body. 

 Specimens taken along the forty-ninth parallel are intermediate between 

 tliose from the far north and the bright richly-colored phase commonly met 

 with in the mountains of Colorado. Many of the specimens from the Black 

 Hills of Montana are equally rich in color with those from Colorado, being, 

 in most cases, absolutely indistinguishable. Others of like tint come from 

 the Uintah and Sierra Nevada Mountains In the Coloradan or quadrivittatus 

 form, the rufons of the sides assumes a peculiarly rich, lively tint of rust, the 

 light dorsal stripes pre whiter, and the dark ones are more intensely black 

 and more narrowly edged with rufous. A much paler form is met with on 

 the plains east of the Rocky Mountains, wherever the species is represented, 

 becoming palest in the Mauvaises Terres region, where it also decreases very 

 much in size. The form met with in the Rocky Mountain ranges north of 

 the South Pass is larger, and has the rufous parts of a duller brown than is 

 seen in the form which prevails in the mountains more to the southward. 

 In the Bitter Root and Cascade ranges, the size still further increases, and 

 the colors become still duller and heavier, jmssing here into the very ' .rge 

 anu peculiarly dark form of the coast region of Washington Territory and 

 British Columbia. In this phase, the rufous tint of the sides no longer 

 brightly contrasts with the general color of the dorsal surface, which has 

 become of a nearly uniform shade of dull yellowish-rusty-brown, varied with 

 three or five (generally five) more or less strongly defined longitudical stripes 

 of black ; in many instances, the spaces between the stripes are not different in 

 tint from the general color. In some cases, the general color is so dark that 

 the outer black lines are effectually obscured, and the others are only dimly 

 defined. In other examples, from the same rogion, the intervals between the 

 dark lines are decidedly lighter than the general surface, varying in some 

 specimens (especially the outer stripes) to grayish-white. The hairs of the 

 tail become deep reddish-brown at the base, and tipped with white instead 

 of yellowish-white. In passing southward, the jize decreases, the general 

 color lightens, especially on the sides, and the 'i^ht and dark stripes become 



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