28 MONOGRAPHS OF NORTH AMERICAN RODBNTIA. 



while tlic Pacific-coast forest-specimens have a rather coarser and harsher fur. 

 This character, too, lias entered into a specific diagnosis; yet, although 

 the poinl cannol be reduced to figures and proven mathematically, we declare 

 thai it is impossible to draw a dividing line between these conditions. 



'The under parts of this animal are white — usually snowy-white in United 

 States prairie skins, and dull soiled white, or even ashy-white, in Arctic and 

 Pacific coast specimens. The remark just made applies here with undimin- 

 ished force. 



The upper parts correspond with the under. In the prairie skins, the 

 color is very bright; a rich fawn or luteous-brown, lined with black on the 

 back. In all the Antic ones, and likewise in the Pacific-coast ones, the shades 

 are much darker, more inclining to ordinary rat-color, but always with more 

 or less of a clayey-brown or rusty-gray. Young animals from these regions, 

 respectively, are dull pale gray and deep slate-gray. One specimen (No 

 o318), apparently a sickly or otherwise abnormal example, is rusty-red 

 underneath. But all these various shades of color are so inextricably mixed, 

 that it is out of the question to base a specific character upon them. 



It is interesting to observe, in this connection, that the tail does not seem 

 to share this variation in color. In the tawniest prairie skins, as in the rest, 

 the tail is ashy-gray above, white below. Sometimes, indeed, the tail is paler, 

 or even a little browner, than in other cases; but it is essentially gray in all 

 cases — discolor with the back in the rusty skins, concolor with the back in 

 the dark ones. 



We are pleased to notice in this animal the strongest possible confirma- 

 tion of the views reached in our discussion of various supposed species oi 

 Hesperomys, concerning geographical strains. We solve the whole Neotoma 

 question in a nutshell, when we say that it is parallel with the case of Hes- 

 peromys "austerus" as far as dark color and length of tail of N. "occidentalis" 

 are concerned; anil with the "nebrascensis" style of "sonoriensis" as far as 

 color is concerned. We may. in a rude way, throw the Neotomn skins before 

 us into three heaps: first, the Arctic ones, thickly clad, short-tailed, dark-col- 

 ored ; secondly, the United States prairie ones, thinly clad, short-tailed, bright- 

 colored ; thirdly, the Pacific-coast ones, medium clad, long-tailed, dark-colored. 

 If there be more than one "species", there certainly are three; and granting, for 

 a moment, that there are two, the Arctic ones, of course the true N. drum- 

 mondii, look much more like the Pacific-coast ones than they do like the 



