34 
U. S. P. R. R. EXP. AND SURVEYS—ZOOLOGY—GENERAL REPORT. 
The specimen described was collected by Mr. Peale in California, and is the original of the 
species as presented in the Report on the Mammals and Birds gathered by the United States 
Exploring Expedition under Captain Wilkes. 
This species and A. occidentalis differ in their decided clear and bright rufous tinge from any 
others I have yet seen from the Pacific coast. Indeed, there are none belonging to their division 
among Arvicolae which resemble them among eastern specimens, except one from Holmes’ Hole, 
Massachusetts, already described on page 526. 
From its ally, A. occidentalis , the A. californica differs in being larger, with shorter tail and 
feet, and longer ears. The fur is longer. The color above is more yellowish and more inter¬ 
rupted by the dark tips of the longer hairs, and the tints of the back, sides, and belly pass much 
more insensibly into each other. Indeed, there is but little difference appreciable between the 
back and sides in this respect. 
ARVICOLA OCCIDENTALIS, Peale. 
Arvicola occidentalis, Peale, Mamm. and Birds, U. S. Ex. Ex., 1848, 45. 
Leconte, Pr. A. N. Sc. Phila. VI, 1853, 408. 
Aud. & Bach., N. Am. Quad. Ill, 1854,294. 
Sp. Ch. —Size rather small. Length 3| inches ; tail half this length or more ; nearly twice as long as the head. Ears short 
concealed, less than half the hind feet, well furred. Feet large ; anterior half the posterior. Hind toes two-fifths the rest of the 
foot. Fur soft, short, .35 of an inch. 
Above, uniform bright rufous, paler on sides, grayish white, tinged with yellow beneath ; colors not distinctly separated. No 
appreciable mixture of black hairs above. Skull, 1.12 X .62, or as 100 : 55. 
The fur of this species is soft and fine, with considerable lustre; it measures about 35 hundredths 
of an inch on the back and half as much beneath. The whiskers are light gray and black, 
shorter than the head. The ears are short and rounded, concealed by the fur which projects an 
eighth of an inch or more beyond them; they are a little less than half the length of the hind 
foot, coated on both sides with rather short hairs which are more closely implanted than in 
many species ; the region around the meatus, however, is bare. The antitragus is moderate. 
The feet are quite large ; the anterior, measured from carpal joints, are about half as long as 
the posterior. There is a short, rather obtuse claw to the thumb. The hind feet are hairy 
beneath from the heel to the tubercles ; the toes are rather short; the longest scarcely reaching 
-fth the length of the tarsus and metatarsus. The tail is large, nearly twice as long as the head ; 
thick and tapering, uniformly coated with hair of equal length to the tip, which is terminated 
by a pencil. 
The predominant color of this species is a rather bright and uniform rusty along the back 
and cheeks, paler and more yellowish on the sides ; grayish white, with a tinge of yellow 
beneath, the line of demarkation not distinctly defined. There are the usual long hairs inter¬ 
spersed among the shorter ones on the back; these, however, are tipped with very dark rufous 
instead of black, and to them the darker color of the back is mainly owing. The feet above are 
sparsely covered with rufous hairs; the tail is also rufous ; passing insensibly beneath with a 
slightly paler tint. 
