10 University of California Publications in Zoology. {VoL.9 
must be understood, can be easily extended by a short excursion 
out onto the chaparral-clothed slopes to the westward, where such 
birds as the Bell sparrow and black-chinned sparrow are plainly 
in evidence, or by a few thousand feet climb towards San Ber- 
nardino peak, which would carry one through a Transition set 
of animals well into the Boreal zone. As to individuals, Seven 
Oaks is within a region of perhaps as abundant animal life as any 
locality of like extent in the San Bernardino mountains. Its 
moist meadows, densely-wooded stream-bottom, and chaparral 
slopes combine to furnish an abundant shelter and food-source 
for its large population. 
Upper SANTA ANA CANYON. 
The upper Santa Ana river flows west through a broad valley, 
not at all of the character of a true canon, separating the range 
on the north, of which Sugarloaf is the culminating peak, from 
the more lofty one on the south, which includes San Bernardino 
and San Gorgonio peaks. The main stream heads in a broad, 
nearly level, depression, at 6700 to 7000 feet altitude, known as 
Big Meadows, and in the space of ten miles down to Seven Oaks 
makes a descent of 2000 feet, so that the grade is not very steep. 
The south-facing north wall of this upper course of the Santa Ana 
is relatively hot and arid, only a few intermittent streams flowing 
from it; while the shaded south wall is always at least one zone 
higher at the same level, and is drained by several large and per- 
manent streams. These in their order of importance are: South 
Fork, Fish creek, Barton creek, and Lost creek. The first-named 
stream heads in the great amphitheatre on the northwest side of 
San Gorgonio peak, where the snowfall is heavy, and where snow- 
banks last nearly, if not quite, all summer. And this stream 
carries as much water, especially late in the summer, as all of the 
others combined. It was along this upper reach of the Santa 
Ana, and along its tributaries, that I did more work than any- 
where else, partly because the region is an exceptionally inviting 
one to the camper, as well as to the naturalist. 
The life zones show a decided response to the law of slope ex- 
posure. The shaded south wall below 9000 feet altitude is almost 
entirely lower and upper Transition; while the sunny north wall 
