5G 



NORTH AMEKICAX FAUNA. 



[NO. 16. 



peratuie still more. Higlier parts of tbe same slope are not only very 

 iiiucli drier, but are exposed to the direct rays of the afteruoon suu, 

 which, owing- to the increasing steepness, strike the ground more nearly 

 at a right angle than at lower elevations, the result l)eing a material 

 increase in the amount of heat received. It is obvious, therefore, that 

 on the southwest and w^est slopes the middle ])ai't of the Transition 

 zone is the hottest and driest, the part in which low Transition or even 

 Upper Sonoran species are most apt to be found, while the upper and 

 loiccr parts are coolest and dampest, the parts most likely to be invaded 

 by Canadian zone species. Hence it is not surprising- that J)ouglas and 

 white hrs, willows, alders, elder, snowberry, red spinca, osier, and thiui- 

 bleberry tiourish at the top and bottom of the Transition slope, but are 

 absent from the middle part. At the extreme foot of the slope, along 

 the cool streams near Sisson Tavern, two normally boreal ])lants occur 

 ■which were not found at all in the boreal belts on the mountain. These 

 are Limuva borealis and Pachi/stima myrsinites. With them is associ- 

 ated the mountain chin(|uaiiin {('((sttoiopsis strnprrrirens). There is 

 something- peculiar about the distribution of l'<(ch!/stiiua. It is abund- 

 ant in the neighborhood of Sisson Tavern and occurs here and there, 

 apparently on dry soil, up to an altitude of 4,700 feet, but not above. 

 Since all three of these species are boreal, it is possible that the forms 

 here referred to are Transition zone subspecies. 



MAMMALS OF TKANSM'IOX /.ONE. 



(1) Species kiiuirn to 



Autilocapra aiiieiicaiia. 



J3a8.saris(U.s astiitus niptor. 



(_'all()sj)eim(ipbiln.s clirysodririis. 



Caiiis ochropus. 



Ca.stor cauadcnsis.' 



Cervii.s occidentalis. 



Dipodoiiiys calit'iiriiiciis. 



Eietlii/.ou ei)ixaiitbus. 



Entaniias aiiKi'iius. 



Eutauiias scnex. 



Felis oregoiieusis. 



Lutra liudsonica. 



Liitreola vison. 



Lyux fasciatua palle.scens. 



Mepliitis occidentalis. 



MicrotiiB nioiitaiiiis. 



MiiTotUfs uiorda.x. 



Myotis evotis. 



Myotis lucifiigiiH loiijfic^nis. 



Nt'otoina ciiiciea. 



Neotoiiia fuscipes. 



Neurotrichns gibbsi major. 



■uf in llie Traiiaition zone of 5/ia.s/a. 



(•(loco ileus coluinliianus. 

 Pei'ognatbus niollipilosvia. 

 Peromyscus boyli. 

 Peroiuysciis gaiubeli. 

 Procyon p.sora pacilica. 

 Scapaims cnlifornicus. 

 Scinroptorns (klaiiiatbcnsis?). 

 Sciiirus alboliinbatiis. 

 Scinru.s fossor. 

 Sorex inoiitcroyensis. 

 Sorex vagrans anmiius. 

 iSpermopbilns douglasi. 

 Spilogalc latifroiis. 

 Tax idea tax us. 



Tbomomys iiionticol;i piiu'toiiim. 

 1,'rocyou califoniiiMis tnwiiscndi, 

 Ursiis atncricaiiii.s 

 Ursiia bonibilis. 

 A'espertilio fu.sciis. 

 Viilpes iiiacronrus.- 

 Zapus pacilicus. 



' li'e.stricteil to cold strcims wjiirji tlinii 

 Bori'nl t,(^ni])(!ratur«'s. 



- l'roliai)ly does not hncd Ixdow ( ,iii;Hli;iii. 



li t I'.n ersinir tlii' Tr.iiisitioii /one all'ord 



