RODENTIA—ARVICOLINAE—ARVICOLA CALIFORNICA. 533 
belly grayish white, the colors passing quite insensibly into each other. Tail bicolor, upper 
and lower surfaces not distinctly separated. Skull, 1.14 by .65, or 100: 57. 
This animal in size nearly equals the larger species of the Atlantic States, and is provided 
with soft and unusually long fur, measuring nearly six-tenths of an inch above. The whiskers 
are as long as the head, and grayish white in color. The ears are rather large, and scarcely 
concealed beneath the fur, about five-eighths as long as the hind foot; they are well covered 
with long hairs on both sides, except about the meatus, and have a distinct segmental anti- 
tragus. The feet are broad and stout, the hinder rather short, the anterior a little more than 
half as long as the posterior. The thumb of the hand is obsolete, and its place indicated by a 
blunt claw. The tail is moderate, about twice as long as the hind feet, tapering considerably, 
and uniformly coated with appressed hairs to the pencilled tip. 
The prevailing color above is lustrous, light yellowish brown, varied with the black or dark 
rufous brown points of the longer hairs. These do not obscure the ground color much, however, 
leaving the general tint a yellow brown or brownish reddish yellow. The sides are rather 
paler. The under parts are grayish white with a yellow tinge, due, perhaps, to alcohol. The 
feet above are brownish gray ; the tail is dark brown above, passing insensibly into a paler 
beneath. The feet and tail have a rufous tinge, in addition to the colors described. 
Skull.—The skull of this species is large and broad ; the width about 57 hundredths of the 
length. The muzzle is long in proportion, and the narrow interorbital portion of the frontal 
bone widens out behind at a point about midway between the end of the nose and the occiput, 
instead of being considerably forward of this point, as in A. occidentalis. The anterior extremity 
of the upper molars is distant from the posterior face of the incisors one-third the distance from 
the incisors to the occiput. 
The posterior upper molar has one anterior triangle, two exterior and one interior, besides 
the posterior bent crescent. This sends out a short lobe outwards near its posterior portion or 
bend, a character rarely observed in American Arvicolae. We have thus, instead of three 
external salient angles with a rounded space behind them, this last mentioned space indented 
by a shallow furrow, so as to produce two short, blunt salient angles, making five external in 
all. The anterior upper molar has one posterior triangle, three interior, two exterior, and an 
anterior tri-lobed trefoil, the lateral exterior lobe of which is produced backwards to form nearly 
as decided a salient angle as the three behind it. There are thus four external salient angles 
and five internal, besides the sub-angular anterior loop of the trefoil. 
Measurements. 
| Inches. 
Head and body (@ricayee: Sec aaeee set ee ee ee eecenes | 4.00 
Pail; (vertebre)*< 2222s coe sb shosss asst oes Pek aeee | 1.50 
Hail: with bains)=- 22. = Lessl sess tte eee ees 1.65 
Mindifeetsiromincells= ae asta yt2 shed ety ole - 80 
LONG CRE LOC Sh ee aia an ee ae pcheata aa ew dewase +40 ~ 
OTE GOUT ATOM: WN ate = om = Se ee ee Se el - 50 
PRG een nied ee 5 ee Sn oon wes ae emai ee a - 50 
Trees inci se el Sea el alba 1.14 
Wile (here earner ea een oe toes noua eens daa asase . 65 
Proportions of skull..-100 : .57. 
