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University of California Fiihlications in Zoology [Vol. 21 



northern Nevada, and going westward, there can be traced through 

 fulva, of southern Oregon and of the Warner Mountains of extreme 

 northeastern California, an increase in bulk of bill and a deepening 

 of the brown coloration, both tendencies culminating in the large-billed 

 hrevicauda of the Yolla Bolly Mountains, which latter is geograph- 

 ically also at the end of the series (see fig. F). The development of. 

 the bill in this chain is similar to that seen in the canescens-monoensis- 

 mariposac-stephensi series, but the brown coloration is quite diiferent, 

 as is also the ratio of tail to wing. A large-billed race, stephensi, at 

 the end of one line of variants, possesses an extremely long tail and 



a 



Fig. E. Bills of four subspecies of fox sparrow of the Schistacea group, show- 

 ing the trend of variation in this member in the four contiguous races extending 

 from northern Nevada {schistacea) through the Mono Lake region (mo)ioensis) 

 and the west slope of the central Sierra Nevada (mariposae) to southern Cali- 

 fornia (stephensi) ; natural size. 



a. Passerella iliaca scldstacea, adult male; no. 9055; Mus. Vert. Zool. ; Pine 

 Forest Mountains, Nevada; June 24, 1909. 



i. Passerella iliaca monoensis, adult male; no. 26930; Mus. Vert. Zool.; type 

 specimen; Mono Lake Post Office, Mono County, California; May 21, 1916. 



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

 specimen; Chinquapin, Yosemite National Park, Calif oniia; June 10, 1915. 



d. Passerella iliaca stephensi, adult male; no. 20505, Mus. Vert. Zool.; Taylor 

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



grayish coloration; a large-billed race at the end of another chain, 

 hrevicauda, is relatively short-tailed and of a brown tone of coloration. 

 It will be observed in the distribution of the several subspecies in 

 California, Nevada, and Oregon, that geographic position accords so 

 exactly with the nature and extent of development of the various 

 features of the races, that the changes of character can be traced from 

 one extreme to the opposite by a series of steps going either from north 

 to south or from east to west. Which of these lines, if either, is 

 indicative of the course actually followed by the species in the original 

 settlement of its present habitat is not evident. Since Passerella iliaca 

 is a Boreal species it is probably safe to assume that the general trend 



