LErORIDiE— GEOGRAPHICAL DISTRIBUTION. 275 



the damp, heavily-wooded legion of British Columbia and Washington and 

 Oregon Territories. 



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

 the treeless region from the Saskatchewan Plains southward to about the 

 latitude of Middle Kansas, or mainly between the isotherms of 36° and 56°. 



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

 winter, and they are 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 

 tails to be universal, and rarely extends throughout the pelage, being confined 

 mainly to a limited portion of the dorsal aspect. 



The habitat of Lepus sylvaiicus (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 sijlmticus. Here it passes by imperceptible stages into 

 variety Nuttalli (zz 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 Audubo/ii, and over the Great Colorado Desert becomes 

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

 var. arizonm. Variety Nuttalli ranges southward from the isotherm of 45° 

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

 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 Sonoran district. Variety Auduhoni 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. arizonce. 



The Sierra Nevada Mountains seem also to form a barrier to the east- 



