292 MONOGRAPHS OF NORTH AMERICAN RODENTIA. 
Arctic America (No. 4583, 8. I.) is intermediate in color between two others 
(Nos. 1779, M. C. Z., and 410, 8S. L), 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. t2medus are from the 
extreme southern limit of the habitat of the species in Europe (excepting 
the mountains of Central Europe), and correspond both in size and propor- 
tions with the skull of Z. arcticus 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 Rae), 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. ¢émidus corresponds very nearly 
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 glucialis the pelage is white to the base. It further differs 
from ZL. americanus in the proportions of the skull and in the form of the 
