1920] Swarth: Revision of Avian Genus Passerella 173 



are September 24 (San Antonio Canon) and March 28 (San Clemente 

 Island) ; other specimens have been taken during October, December, 

 January, and February. 



Passerella iliaca mariposae Swarth 

 Yosemite Fox Sparrow 

 Original description. — Passerella iliaca mariposae Swarth, 1918, p. 161. 



Type specimen.. — No. 25693, Calif. Mus. Vert. Zool. ; adult male; 

 ridge at 7000 feet, near Chinquapin, Yosemite Park, California; 

 June 10, 1915; collected by J. Grinnell; original number 3284. 



Range. — Summer visitant to the Canadian and high Transition 

 zones in the northern and central Sierra Nevada. Breeding stations 

 represented by specimens in hand range from central Siskiyou County 

 (head of Little Shasta River) at the north, south at least to the 

 Yosemite region on the west slope of the Sierras, to Kearsarge Pass 

 on the east slope. There are a few winter specimens at hand from 

 scattered points in San Diego, Los Angeles and San Bernardino 

 counties, but too few to indicate accurately the entire winter habitat 

 or migration routes. 



Specimens examined. — 206 (see list, pp. 206-209). 



Distingwishiyig char\acters. — Of the Schistacea group (see p. 89). 

 With the gray coloration common to the oanescens-nwtioensis-niariposae- 

 stephensi series, and not to be distinguished in color and markings 

 from the other members of this chain of subspecies. In bill structure 

 mariposae lies between monoensis and stephensi (see fig. E). In gen- 

 eral size and length of tail in this line there is progressive increase 

 from canescens to stephensi, and in these particulars as in size of 

 bill, mariposae occupies its appropriate intermediate position (see 

 table 4). 



Remarks. — While there is at hand an abundance of summer speci- 

 mens of mariposae, there is a notable dearth of winter collected birds. 

 These facts, coupled with the reverse condition in megarhynchus, of 

 which I have seen winter specimens only, may be used by some as 

 arguments proving the two to be identical, and only suffered to 

 masquerade under different names through a misunderstanding of 

 seasonal differences. In contravention to this idea it may be pointed 

 out that there are many specimens in the available series of mariposae 

 taken at summer stations just prior to the birds ' departure therefrom 

 in the fall, and after they had assumed the winter plumage, these 

 specimens sufficing to show the color differences distinguishing mari- 

 posae from megarhynchus. Shape of bill is an excellent differentiating 

 character between adults at any season. 



There are a few examples of mariposae at hand taken in winter 

 at various points in southern California, but they are so few in 



