RODEJJTIA-ARVICOLINAE—ARVICOLA EDAX. 
531 
inch. The tail, in the dried specimen, is about two-fifths the length of the body; it is well 
covered with hair and has a scanty pencil at the tip. 
The upper parts in this species are of a dark dull yellowish chestnut, or rufous brown, mixed 
with black ; no indication of rusty, however. The under parts are dirty whitish ash. The feet 
are light brown ; the tail brown ; slightly paler at the base beneath. The line of separation 
between the colors of the sides and belly is rather distinct. 
SJcull .—The skull belonging to skin 1268 has some striking peculiarities, which distinguish 
it from others with which it has been compared. It measures 1.08 inch by .61 (100:55.) The 
most prominent feature is the length of the skull anterior to the molars. Thus the distance 
from the molars to the base of the incisors (.31) is considerably more than one-third that from 
the incisors to occiput, or even rather more than one-third the length of the entire skull. The 
molars are thus thrown further back than in other species. The line of upper molars measures 
.24 of an inch, or less than one-fourth the length of the skull. 
The posterior upper molar has three exterior salient angles besides the posterior bent crescentic 
lobe, which is without any supplementary loop on its inner side. On the inside there are 
three salient angles, in addition to that of the posterior branch of the loop, or one anterior 
triangle, two exterior, one interior, and a posterior crescent, with two loops, both pointing to 
the inner side of the tooth. The anterior lower molar has one posterior triangle, three internal, 
two external, and an anterior trefoil lobe, the lateral loops of which are somewhat reduced. 
This species differs from A. townsendii in the smaller size and the proportionally less feet 
and ears, while it approximates to it in color. From A. edax its color and the smaller feet and 
ears will distinguish it. It is of a darker and more rufous color than A. edax and montana,{'?) 
while its wider head and longer muzzle separate it from the latter, which it otherwise resembles 
in the small feet and ears. The feet are still smaller, however, than in the A. montana. 
List of specimens. 
| Catalogue number. 
Corresp’g No. of skull. 
Sex and age. 
Locality. 
Whence and how 
obtained. 
Nature of 
specimen. 
Measurements. 
Collected by— 
Nose to tail. 
Tail to end of vert. 
Tail to end of hairs. 
Fore foot, length. 
Hind foot, length. 
Skull, length. 
Skull, width. 
Ear, height. 
Longest toe. 
1268 
2220 
9 
Upper Pit River, Cal... 
Lt. R. S.Williamson 
Mounted. 
4.50 
1.50 
1.60 
.40 
.73 
1.08 
.61 
.45 
.26 
Dr. Newberry. 
ARVICOLA EDAX, Leconte. 
California Ground Mouse. 
Arvicola edax, Leconte, Pr. A. N. Sc. Phila. VI, 1853, 405. 
Aud. & Bach. N. Am. Quad. Ill, 1854, 270 ; pi. cliv, fig. 2. 
Sp. Ch.—S ize moderate (head and body four inches ;) less than A. riparia Ears large, longer than the fore feet; as long 
as hind feet, minus the toes ; well furred. Tail about two-fifths of head and body, little over one and a half times as long as 
hind foot. Hind foot .9 inch ; toes long. Color above, pale dull yellowish brown, without any rufous ; uniformly sprinkled 
with black. Beneath grayish white. Tail strongly bicolor. Feet grayish white. 
The fur of this species is loose and harsh, not lying compactly, and without gloss. The hairs 
