OCT., 1899 ] UPPEK SONORAN ZONE. 53 



to tix with certaiuty the normal zone altitudes. Hence those here given 

 must be regarded as approximate only. Tlie average width of the belt 

 of overlapping of adjoining zones appears to be about 800 feet; so that 

 the normal vertical distribution of the distinctive species of each zone 

 overreaches in both directions the altitudes given by about 400 feet. 



The zone positions accorded the various species are based on per- 

 sonal Held experience, and in the great majority of cases are believed to 

 be correct; in a few instances, however, the evidence is inconclusive — 

 hence the zone lists must be regarded as provisional and subject to 

 correction. Species recently exterminated or driven away, as the moun- 

 tain sheei^, elk, and griz;^ly bear, are included in the tables. 



UPPER SONORAN ZONE. 



The Upi>er Sonoran element in the region about Shasta is dilute and 

 is limited to Shasta Valley at the north base of the mountain, which it 

 reaches by way of the Klamath country on the north and northeast. 

 It has no connection whatever with the Upper Sonoran of the Sacra- 

 mento Valley on the south, which ends near the point where Pitt River 

 joins the Sacramento, about 50 miles below Shasta. 



Shasta Valley is an arid plain about 25 miles in length by 10 or 12 in 

 breadth, studded with small volcanic buttes and lava Hows. It varies 

 in altitude from a little less than 4,000 to about 2,700 feet, and is lowest 

 at the north, where the Shasta Kiver, by which it is traversed, tiows 

 into the Klamath liiver. Shasta Kiver is in places bordered by decid- 

 uous trees, mainly Foj)nluH triehocarpaj Betula occidentaUs, and Alnus 

 rhomhij'olia. The valley is sparsely covered with rahbit brush of sev- 

 eral species, mainly ChriisotJiamnns occidentaUs and ('. rlscuJiJiorus, and 

 in some places, chietly on the east and south, by the true sagebrush 

 {Artemisia tridentata). The southeastern part contains an open forest 

 of junipers [Junipcrus occidentaUs), which meets the pine forest of the 

 basal slopes of the mountain. The western i)art is an open plain very 

 scantily dotted with rabbit brush and a few small and mainly incon- 

 spicuous plants, among which were observed: Mentzelia hci-icaulis, 

 Xanthium strnmarium, Heliotropium cnrassavicum, Verbena bracteosa, 

 Datura meteloides, Sarcobatus rermiculatus and Nicotiana sp. ? Along 

 the western border of the valley, near the Scott Mountains, several 

 characteristic shrubs occur, among which are Ceanothus cuneatus, Arcto- 

 staphyJos {viscida!'), Cercocarpus parvifolius, Eriodictyon glutinosKm, and 

 Garry a fremon ti. ' 



The zone position of this region is further indicated by the presence 

 of such birds as the chat {Icteria virens lonyicauda), bush-tit {Pstdtri- 

 parus minimus calif or nicus), California towhee [Pipilo fuscus crissalis), 

 California jay {Aphelocoma californica), and California valley quail 

 {Lophortyx caUfornicus vallicola). Formerly antelope were common 

 here, but now they are rarely seen. The most abundant mammals are 

 jack rabbits (Lepus caUfornicus), sagebrush cottontails {Lepus nut 



' (iarriia fremonti is both Upiim- .Sonoran and Transit ion. 



