144 MONOGRAPHS OF NOKTH AMERICAN KODENTIA. 



that in gapperi the feet and tail are Lengthened pari passu. There seems to 

 lie a positive difference in the shape of the tail, which in gapperi, besides 

 being longer, is slimmer, or of less caliber, than in ruHlus, and it tapers to a 

 liner point. In gapperi, again, the hairiness of the tail is much less than in 

 rutilus, the annul i 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 feel ; the soles of the Massachusetts specimens, even 

 winter ones, showing a naked space behind the posterior tubercle. 



We cannot agree with Professor Baird that gapperi "appears quite dis- 

 tinct from the Hypudceus glareola 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, rutilus 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 Hypudceus 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. 



