144 MONOGRAPHS OF NORTH AMERICAN RODENTIA. 
that in gapperi the feet and tail are lengthened pari passu. There seems to 
be a positive difference in the shape of the tail, which in gapperi, besides 
being longer, is slimmer, or of less caliber, than in rutidus, and it tapers to a 
finer point. In gapperi, again, the hairiness of the tail is much less than in 
rutilus, the annuli being always visible, and the terminal pencil never equaling 
a fourth of the length of the member. There is a corresponding decrease 
in the hairiness of the feet; the soles of the Massachusetts specimens, even 
winter ones, showing a naked space behind the posterior tubercle. 
We cannot agree with Professor Baird that gappert “appears quite dis- 
tinct from the Hypudeus glarcola of Keyserling and Blasius”. It is true that 
our material is insufficient to bring us to any conclusions to which we should 
wish to finally commit ourselves; but, for all that we can see, rutidus has in 
Europe undergone precisely correspondent modifications with climate, result- 
ing in the so-called “glareola”. Our samples purporting to be of this last 
are only two, Nos. 402 and 403, both from Sweden, and one of these is 
young and in poor condition, and therefore not eligible for comparison; but 
No. 402, taken in the depth of winter of 1847, seems to us in every respect 
identical with winter skins from Massachusetts and Lake Superior. Thus 
No. 402 and No. 910 (from Lake Superior) might have belonged to the same 
litter, for any difference that we can discover. 
We feel justified in using substantially the same language respecting the 
so-called Hypudeus rubidus of Europe; that is, provided No. 2994, from 
Switzerland, labeled ‘‘Myodes rubidus”, be really an example of that form. 
This, our only example purporting to be “rubidus”, is a little smaller, perhaps, 
than average gapperi or “glareola”, with length of tail and feet at a maximum, 
as was to have been expected from its very southern habitat; but we find 
nothing to raise a suspicion of its specific distinction. 
However, in a memoir upon North American mammals, we need not go 
out of our way to discuss a question affecting those of other countries exclu- 
sively. We do not, therefore, pursue the subject; and in the same spirit we 
refrain from adducing any European names as synonyms of the American 
gapperi, or rather we retain the latter name as the designation of our animal, 
not making the change in nomenclature that might be necessary were gap- 
peri, glareola, and rubidus combined. 
A specimen of gapperi from Chilowk Lake, Washington Territory, 
collected in August by Dr. Kennerly, while attached to the Northwest Boun- 
dary Survey, enables us to extend the known range of the species materially. 
