28 MONOGRAPHS OF NORTH AMERICAN RODENTIA. 
while the Pacific-coast forest-specimens have a rather coarser and harsher fur. 
This character, too, has entered into a specific diagnosis; yet, although 
the point cannot be reduced to figures and proven mathematically, we declare 
that 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 Arctic 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 
3318), 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 of 
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 JV. “occidentalis” 
are concerned; and with the ‘‘nebrascensis” style of ‘‘sonoriensis” as far as 
color is concerned. We may, in a rude way, throw the Neotoma 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 WV. drum- 
mondit, look much more like the Pacific-coast ones than they do like the 
