290 CALIFORNIA MAMMALS. 



or northern limits in this zone : Nuttall Woodpecker, Costa 

 Hummingbird, Yellow-billed Magpie, Nelson Oriole, Lawrence 

 Goldfinch, Black-throated Sparrow, Long-tailed Chat, Calif ornian 

 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 ex- 

 tent, 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 of 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 Butamias) occur. Several species of 

 Pocket Rats and Pocket Mice and the Big-eared Fox are peculiar 

 to this zone, the Gambel Partridge, Scott Oriole, Leconte 

 Thrasher, Crissal Thrasher, Yellow-headed Tit and Plumbeous 

 Gnatcatcher. 



The large valley known as the Sacramento Valley (north- 



