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MONOORAl'IIS OF NORTH AMEUH^AN UODENTIA. 



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Two specimens collected on the Nortliwcsteni Bounilnry Survey by Dr, 

 Keiincrly (doubtless in Washington Territory) can be exactly matched, both 

 in si?c and color, by specimens from l^Ialamagaminque, Onada, except that 

 ((uc is more yellow l)elow than the Canada s|)ecinR'iis. Another, from Fort 

 Crook, Cal., is much darker than tiie specimens from Washington Ter- 

 ritory, with a strong yellowish wash below, which extends over the whole 

 lower surface of .he tail. No. !)625, from Idaho, and No. 9704, from the 

 Uintah Mountains, a-e two of the darkest specimens in the collection; but 

 in the series from Big Island, Great Slave Lake, there is one fully as dark, 

 while one from the Rv?rt River district is scarcely lighter. 



Specimens from tl:e United Slates, and especially from the more south- 

 ern portions, are more yellowish-brown above, with much less black on the 

 tail, and more yellowish below, than specimens from Northern New England, 

 Canada, and the more boreal parts of the continent. In some of the southern 

 specimens, there is no dusky or black on the tail, which inclines to a rufous 

 shade of brown above and yellowish-brown below. 



Average southern specimens differ from average northern specimens 

 most strikingly in size and in the length and fullness of the pelage, but also 

 in tbe tail being relatively narrower, and the soles of the feet nakeder, and 

 also quite appreciably in color, especially in the ujjper side of the tail being 

 nearer of the color of the back. There is, however, no break in the sequence 

 from north southward, either in size, color, or other characters, by which the 

 group can be subdivided specifically, or even vnrietally. The recognition, 

 as above, of a northern and southern subspecies, is, in great measure, arbitrary. 

 Apparently, those inhabiting the Rocky Mountains of Montana and the Uintah 

 Mountains are darker in color than those from other regions, and rather more 

 ferruginous above, running into a phase corresponding somewhat with van 

 rir.hiirdgoni of the Sciurus hudsonius group, inhabiting the same regioi;. 

 Ncnthcr this form {Ptcromt/s alpinus auct.) nor the so-called ^'Pteromi/s 

 nregontnuis" seems to me to be varietally distinguishable, especially the latter, 

 specimens of which ai'e, sometimes at least, absolutely indistinguishable from 

 Canadian specimens. The supposed differences in the length and direction 

 of the carpal fascia sup|H>rting the flying-membrane, I am unable to appreciate. 



In respect to differences of a strictly individual character, we meet 

 oeciisionaily with specimens from both the Atlantic and Pacific slope, as well 

 as from the interior, in which the color of the lower surface of the tail ia 



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