RODENTIA-MURINAE —HESPEROMYS LEUCOGASTER. 
481 
anterior of these are larger, the posterior smaller in proportion than usual, the fore feet are 
very strong, and appear quite fossorial. The fore arm is as long or even longer than the 
hind foot from the heel, instead, as in H. Leucopus, of being appreciably shorter. The fore feet 
are not appreciably different from those of H. leucopus , except that they are much larger, the 
toes longer, and the claws fully twice the length of the hinder ones ; the tubercles are similar. 
The hind feet are short in proportion to the anterior ; the first claw does not reach beyond 
the base of the adjacent toe ; there are hut four tubercles, as far as I can ascertain, the two 
posterior in Hesperomys leucopus not being represented at all. The sole is very densely hairy 
from the heel to these tubercles, or for nearly two-thirds the length of the foot; this hairiness 
more extended and much more dense than in H. leucopus , the tubercles themselves appear quite 
similar in size. 
The tail is short, about twice the length of the hind feet, and contained two and a half times 
in the head and body. It is thick at base, quadrate, and tapers rapidly to an attenuated tip ; 
it is very closely covered with shortish hairs, pressed flat to the surface. 
The fur is rather long and full; it is, however, soft and fine like that of H. leucopus , or even 
finer, and without any of the rough appearance of Arvicola and Sigmodon. The general color 
of this species above is a grayish brown, finely lined with black ; this color predominating on 
the hack. Towards the sides there is an infusion first of reddish and then of yellowish brown, 
until finally, on the lower part of the sides, is seen quite a distinct band of fulvous, The entire 
under parts, the feet, and outside of the fore leg, with the lower half of the tail, are white, in 
the alcoholic specimen, with a yellowish tinge. 
In the following table I give the measurements of some parts of this animal, (from a specimen 
in alcohol, 2549,) compared with a large H. leucopus , (2732,) to illustrate the differences in 
proportion : 
2549. 
2732. 
Nose to occiput____ „,_ 
1. 25 
1. 26 
root of tail_,_„_ 
4.10 
3. 55 
Ear___ 
.46 
. 60 
Tail, vertebras_____ 
1. 65 
3. 05 
hairs_____ 
1.70 
3. 15 
Fore arm___ 
. 82 
. 66 
Hand_......_ 
. 55 
. 44 
Longest finger and claw___ 
. 34 
. 25 
its claw_ 
. 20 
.06 
Femur____ 
. 85 
. 80 
Tibia_____ 
1. 05 
1. 05 
Hind foot__ 
. 85 
. 87 
Longest toe and claw_ 
. 30 
. 30 
its claw alone_ 
. 14 
.07 
To show the peculiar proportions of this mouse, I need scarcely do more than to refer to the 
preceding table. 
In external appearance this mouse bears quite a close resemblance to an Arvicola , so much 
so, indeed, as to have been described by Prince Maximilian, several years before Audubon and 
Bachman, as Hypudaeus leucogaster. His specimen was taken at the Mandan village, where it 
61 L 
