270 



MONOGllAl'IlS OF NOItTH AMKUICAN RODENTIA. 



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The sninc tiling is also well seen in the Arctic Ilnrc {Lepus (i?iii({u.<i),\n com- 

 paring Newroundliind specimens with those from the arctic coast, or those 

 of Ireland and the mountains of Central Europe with those of Scandinavia. 

 Tiio Northern Ilare also presents a somewhat parallel variation to that seen 

 in L. si//c<ificus in passing from the Atlantic coast to the llocky Mountain 

 region. In even arctic specimens, there is always, in the winter pelage, a 

 pale rufous zone underlying the white color of the surface, which in turn 

 has still a plumbeous zone beneath it. In winter specimens from the Rocky 

 Mountains, the white of the surface often extends to the very base of tho 

 fur, tiie rufous and plumbeou.s zones being both undeveloped. Passing still 

 farllier westward, we meet, in the Columbia River region, a phase in which 

 the summer pelage is even more rufous than in specimens from the Atlantic 

 coast under the same parallels. The dilference between northern and southern 

 specimens in summer livery consists not so much in the absolutely darker 

 color of the southern examples as in the greater intensity of the rufous, 

 while the form living in the middle elevated region of the continent dilfers 

 from those of both the Atlantic and Pacific coasts in the almost entire sup- 

 pression of the rufous tint that forms the prevailing hue in the others. 



The only other species of this llimily having a very extended habitat 

 arc the Lcpus nquaticug, which ranges from the Gulf States to Yucalan and 

 Central America, and the Lepus callot is, found throughout the dry interior 

 from Southern Wyoming and Nevada far down upon the Mexican plateau. 

 In the former, the variations in color between specimens from the most 

 extreme points of its range are almost inapjireciabie ; while, in the latter, 

 there is a considerable increase of rufous to the southward. 



In respect to general size, the variation with locality is not more marked 

 than is that of color; specimens from northern localities being generally not 

 much larger than those from southern localities. I know, in fact, of no 

 species of American mammals which so nearly form an exception to the 

 almost universal law of a decrease in size with the decrease of the latitude 

 under which they live as do some of the species of the LeporidtB. Yet, in 

 the majority of instances, the law is here also borne out. Taking the skull 

 as the most convenient element on which to base a comparison, it is found 

 (see Table I) that a series of sjiecimens of Lfpus americanus from New 

 York, Pennsylvania, and Massachusetts averages larger even than anothci 

 series from Norway, Me.; while the latter averages larger than another series 



