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University of Calif orma Publications in Zoology [Vol. 21 



more slenderly pointed bill (compared with the blunt, stubby bill of 

 hrevicauda) (see fig. F), by more grayish coloration, and by longer 

 tail (see table 4). 



Remarks. — In all its characters stephens-i represents the cul- 

 mination of the line of development beginning with canescens and 

 continuing through monoensis and mariposae. Gray coloration is 

 common to all these forms, as compared with the more brownish hue 

 of the other subspecies of the Schistacea group, and there is no appar- 

 ent difference in this respect between these several southern subspecies. 

 There is, however, gradual increase in general size from canescens 

 along the line indicated to stephensi, with notable increase in size of 



Fig. DD. Bills of t7n-o subspecies of the Schistacea group (races that are 

 distinguished mainly by differences of size in this member), showing how variation 

 of adult and immature may be mistaken for variation differentiating subspecies. 

 a and & are, respectively, adult and undeveloped immature of stephensi, c and d, 

 of mariyosae ; h is more nearly Like c than liie a. 



a. Passerella iJiaca stephensi, adult male; no. 20505, Mus. Vert. Zool. ; Taylor 

 Meadow, Sierra Nevada, Tulare County, California; July 19, 1911. 



&. Passerella iliaca stephensi, immature male; no. 27388, Mus. Vert. Zool.; 

 Hume, Fresno County, California; August 18, 1916. 



c. Passerella iliaca mariposae, adult male ; no. 25693. Mus. Vert. Zool. ; Chin- 

 quapin, Yosemite National Park, California; June 10, 1915. 



d. Passerella iliaca mariposae, immature male ; no. 23195, Mus. Vert. Zool. ; 

 Blue Caiion, Placer County, California; August 28, 1912. 



bill, and there is also, to a lesser extent, some increase in proportionate 

 length of tail. 



Stephensi has a strikingly disconnected range, occurring in a 

 number of widely separated high mountain localities. In the southern 

 Sierra Nevada the subspecies is found in high Transition and Can- 

 adian from southern Fresno County (at points just south of Kings 

 River), south through Tulare County. The localities of occurrence 

 are all on the west slope of the range. Fox sparrows at this latitude 

 do not ascend into the Hudsonian and Alpine-Arctic zones, which 

 constitute so large a part of the summit of the Sierra Nevada. This 

 strip along the divide is an effective barrier to the general dispersal 

 of these birds, and in the case of stephensi it has apparently restricted 

 the subspecies to the western slope. 



