LEPORID^— GEOGEArniCAL DISTIUDUTION. 



275 



the (lamp, heavily-wooded region of British Columbia and Washington and 

 Oregon Territories. 



In the interior, we meet next with Lepns campestris, which ranges over 

 the treeless region from the Saskatchewan Plains southward to about the 

 If.titude of Middle Kansas, or mainly between the isotherms of 36° and 5G°. 



Each of the three above-named species becomes more or less white in 

 winter, and they arc the only species which thus change. The whiteness of the 

 winter pelage extends to the very base of the fur in the more northern spe- 

 cies, but generally affects only the more superficial portions in the others, 

 the whiteness decreasing to the southward in the representatives of the 

 L. americanus group (excepting var. Bairdii), till in the extreme southern 

 portions of the habitat of this species the change occurs merely at the surface. 

 In L. campestris, the change is still less complete, decreasing similarly in 

 extent southward, till in the extreme southern portion of its range the change 

 fails to be universal, and rarely extends throughout the pelage, being confin(!il 

 mainly to a limited portion of the dorsal aspect. 



The habitat of Lepus sylvatkus (including its several varieties) extends 

 from Southern New England on the Atlantic coast southward to Yucatan, 

 its representatives nowhere presenting marked seasonal changes of color. 

 Throughout this vast extent of latitude, it also preserves a remarkable con- 

 stancy of characters. From the Atlantic coast westward (south of the 

 isotherm of 45°) to the eastern edge of the Great Plains, it is represented 

 solely by variety syloaticus. Here it passes by imperceptil)le stages into 

 variety Nuttalli (= artemisia auct.), which ranges thence westward nearly 

 or quite to the Pacific coast north of the State of California. To the south- 

 ward of this boundary, it is replaced, on the Pacific slope, by its nearly 

 related variety Auduboni, and over the Great Colorado Desert becomes 

 modified into another closely-allied form, to which we have given the - 

 yar. arizonee. Variety iV«//fl//t ranges southward from the isotherm o 

 to the plains of Western Texas and New Mexico, and even as far south ..o 

 the arid Mexican plateau. Variety arizonce seems confined to the limited 

 region of the almost rainless deserts of Arizona and Southern California, or 

 the so-called Sonomn district. Variety Auduboni occupies the Pacific slope 

 from the northern boundary of California southward to Cape Saint Lucas, 

 and in the interior seems to gradually pass into var. arizorxe. 



The Sierra Nevada Mountains seem also to form a l)arricr to t!ic east- 



If 



