292 MONOGRAPHS OF NORTH AMERICAN RODENTIA. 



Arctic America (No. 4583, S. I.) is intermediate in color between two others 

 (Nos. 177!l, M. C. Z., and 410, S. I.), from Sweden, except that in the 

 former the feet are white, and in the latter of the same color as the body. 



The subjoined tables of measurements, taken partly from specimens and 

 partly compiled from authors, indicate a considerable range of both individual 

 and geographical variation. The three skulls of L. timidus are from the 

 extreme southern limit of the habitat of the species in Europe (excepting 

 the mountains of Central Europe), ami correspond both in size and propor- 

 tions with the skull of L. arclkus from Newfoundland, the southern limit of 

 the habitat of the latter. The Fort Anderson specimen is also but slightly 

 larger than the one from Newfoundland. On the other hand, the Greenland, 

 Melville Island, and Plover Bay specimens are very* much larger, while 

 the Yukon River specimens are intermediate, as are the geographical 

 positions of the localities, the whole together forming an intergrading series. 

 Between the largest (from Melville Island), with a length of 4.30 and a 

 width of 2.08, and the smallest (from Newfoundland and Fort Bae), with 

 a length of 3.55 and a width of 1.75, the difference is very considerable, 

 and, without the intermediate specimens, might be regarded as indicating 

 specific distinction. 



The table of measurements of the animal are not wholly satisfactory, 

 probably having all been made from skins; but doubtless furnish trustworthy 

 data for the comparison of the two forms, the character of the material being 

 the same for each. The variation in size in var. timidus ranges from 17 to 

 25.50 inches for the length of the body, and in var. arcticus from 22 to 26 

 inches. The single Lapland specimen of var. timidus corresponds very nearh 

 in size with the Greenland, Baffin's Bay, Labrador, and Bering's Straits 

 specimens of var. arcticus, while the Swedish and Scottish specimens are very 

 near the size of the Newfoundland specimens. The ear appears to average 

 rather larger in the var. arcticus series, but in no other respect are there any 

 essential differences in proportions. 



The L timidus var. arcticus differs but little in its general proportions 

 from L. americanus, but it is at once readily distinguishable by its much 

 larger size. It also differs in the color of its winter pelage, that of L. ame- 

 ricanus being plumbeous at base, then yellowish-brown, with only the surface 

 white, while in glatialis the pelage is white to the base. It further differs, 

 from L. americanus in the proportions of the skull and in the form of the 



