472 University of California Publications in Zoology — Vou. 17 
weight, with position of postorbital processes on the jugal faintly 
indicated in six crania out of sixteen; temporal ridges comparatively 
well marked, more accentuated than in either Aplodontia rufa rufa 
or A. r. pacifica, in some skulls widely separated, as in pacifica, Mm 
others approaching to within a few millimeters of each other, as in 
rufa; audital tubes tending to be of smaller caliber than in rufa, 
larger and straighter than in pacifica; incisive foramina comparatively 
short. 
External Characters.—Above, light ochraceous-buff or pinkish buff, 
obscured by an admixture of black hairs which is nearly uniform over 
all upper parts—an insprinkling of silvery-tipped hairs augments the 
grizzled appearance—some specimens appearing conspicuously black- 
ish ; under parts near pale quaker drab with many silvery white hairs; 
the faintest possible wash of buffy brown observable in certain ex- 
amples; a white spot usually present posteriorly in the vicinity of the 
external genitalia. 
Sexual Differences—Three males out of eleven have total length 
greater than the maximum of that measurement in the females; six 
have tail vertebrae longer than this maximum, and six also have hind 
foot longer. Comparison of fall examples demonstrates that the three 
darkest specimens are males, their darker coloration being more evi- 
dent ventrally. In this species in fall pelage the spot marks about 
the mammae do not afford a distinctive character. While they are 
in evidence in certain specimens of both sexes, they are lacking in 
others. In examples having the spot marks, females have them more 
accentuated than males. 
There is a tendency for the ridges and processes in the skulls of 
males to be somewhat more accentuated than in those of females. 
Temporal lines or ridges appear to come closer together with old age 
in males than in females. : 
Molt-—Two young specimens (nos. 9061, 9062, Field Mus. Nat. 
Hist.), collected August 16 and August 18, respectively, are molting 
into the adult pelage. The adult coat has replaced the juvenal pelage 
everywhere in these specimens except in a narrow band across the 
shoulders, although a patchy appearance posteriorly in one of them 
(no. 9061) suggests that the molt is incomplete in that region. An 
adult specimen (no. 21159, 4, Mus. Vert. Zool.) taken at Carlotta, 
’ Humboldt County, November 5, has almost completely assumed the 
fresh pelage. New hair is still coming in on a narrow longitudinal 
line on the back posteriorly. Another specimen (no. 21156, ¢, Mus. 
Vert. Zool.) taken October 29 has the winter pelage complete. 
