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JOURNAL OF MAMMALOGY 
plicating the situation.^^ We therefore moved to a considerably more 
distant point. The spot chosen was a rocky range of hills near the 
village of Oro Grande, on the Mojave River, between fifty and sixty 
miles to the westward of our previous station. The new locality was 
some seven or eight hundred feet higher than the previous one, and 
perhaps differed somewhat climatically, as it did in respect to vegeta- 
tion. It was, however, a typical stretch of desert country, and many 
of the more abundant plant species were common to the two regions. 
The hills along the base of which we trapped were covered with large 
masses of igneous rock, whose prevailing hues were pale gray, buff and 
pinkish, interspersed with areas of finer materials (gravel and sand) 
of a still paler hue. No lava fields or other extensive masses of dark 
rock occur in this vicinity. 
One hundred and thirteen specimens of P. crinitus, together with 
thirteen belonging to other species, were taken in my live-traps in 
the course of 478 trap nights. Fifty skins were preserved, care being 
exercised, as before, that the choice of individuals should bear no rela- 
tion to the color of their pelage. 
A superficial comparison of this series of skins with that from the 
lava field revealed no obvious difference in their average color-tone. 
A careful quantitative study confirms this first impression. Indeed 
it seems rather remarkable that two random collections comprising 
such limited numbers, should agree so closely. The mean readings of 
the two series,^^ through the three color-screens of the Hess-Ives Tint 
Photometer, are as follows: 
EED 
GREEN 
BLUE- VIOLET 
Lava 
26.2 
19.2 
16.0 
15.9 
Oro Grande 
26.7 
19.4 
12 This second field is rather more than a mile distant (at the nearest point) 
from the “Pisgah” lava bed on which the trapping was done. The intervening 
area was occupied by level ground, entirely devoid of rock and likewise appar- 
ently of Peromyscus crinitus. Elsewhere, the “Pisgah” field is separated by 
much wider intervals from the nearest rocky hills. 
12 A few skins were rejected from each series owing to immaturity, or to obvious 
loss of hair. There remained 45 in the lava set, 46 in that from Oro Grande. 
