7 
The Upper Austral Zone lies next below or south of the ‘Transi- 
tion Zone. in many parts of the Upper Austral Zone a thick growth 
of several species of shrubs, collectively known as chapparral or 
chemisal, covers the hills. Forests are few and west of the Sierras 
are composed mostly of oaks, which east of the Sierras are replaced 
by Pinons and Junipers. ‘The Gray-leafed Pine is common in this 
Zone in some places within the drainage of the San Joaquin and 
Sacramento valleys. ‘The most characteristic mammals of the Upper 
Austral Zone are Pocket rats, two genera and several species, Pocket 
Mice of several species, Californian Grasshopper Mice, Striped 
Skunk, Gray and Island Foxes. The following species of birds find 
their upper or northern limits in this zone, Nuttall Woodpecker, 
Costa Hummingbird, Yellow-billed Magpie, Nelson Oriole, Law- 
rence Goldfinch, Black-throated Sparrow, Long-tailed Chat, Califor- 
nian Thrasher and Black-tailed Gnatcatcher. 
That part of the Upper Austral Zone lying on the west side of the 
Sierra Nevada Mountains, consisting of a long narrow strip along 
the sides of the lower parts of the mountains, may be called the 
Foothill Fauna. A broken region of moderate extent, bounded on 
the west by the Humboldt Fauna, on the north by the Shasta Fauna, 
on the east and south by the Sacramento Valley, may be called the 
Clear Lake Fauna. The region bounded on the west and southwest 
by the Santa Cruz Fauna and the Pacific Ocean, on the southeast by 
the Santa Ynez Mountains and on the northeast by the San Joaquin 
Valley may be called the San Luis Obispo Fauna. All the islands 
lying off the Southern California coast may be grouped together 
under the name of the Island Fauna. That part of the Upper Austral 
Zone south of the San Luis Obispo Fauna, and the Mojave Desert 
and west of the Colorado Desert may be called the San Jacinto 
Fauna. 
The Lower Austral Zone includes most of the Mojave Desert, the 
San Joaquin and Sacramento valleys, and a strip along the coast from 
Santa Barbara to San Diego and southward. Over much of this 
area cactuses form a characteristic part of the vegetation. But few 
trees occur and these are found mostly along streams and in damp 
land. Much oi this zone is very arid. Shrews are nearly wanting 
in this zone. Several species of bats find their northern limit in it, 
as do several species of ground squirrels. No species of tree squirrels 
or chipmunks (genera Sciurus and Eutanuas) occur. Several species 
