98 University of Calif ornia Puhlicaiions in Zoology [Vol. 21 



which adds to the generally slenderer appearance, and several of the 

 Schistacea subspecies are actually of smaller size and lighter build 

 than the races forming the other groups. 



Here coloration is relatively uniform, the gray hues predominat- 

 ing and the browns at a minimum. The greatest variation lies in the 

 size and shape of the bill, one extreme in the small-billed oanescens, 

 the other in the large-billed stephensi. It should be pointed out here 

 that the "tooth" that is frequently seen upon the upper mandible 

 of birds of the Schistacea group is of no diagnostic value. It appears 

 indifferently in any of the subspecies, though mostly in those with 

 the larger bills, and is developed to a varying degree, apparently as a 

 peculiarity of the individual. 



It is not possible in this aggregation of subspecies, to trace any 

 such simple and direct line of variation as occurs in the Unalasch- 

 censis group, where the linear arrangement of subspecies, north and 

 south, accords precisely with the development of the several variable- 

 characters observed. In the Schistacea group the problem is much 

 more involved, and it is possible to trace different lines of develop- 

 ment as different directions are followed (see fig. D). 



In altivagans is seen a link between iliaca, which is among the 

 largest of the fox sparrows, of bright colors, and with fairly large 

 bill, and schistacea, of small general size, dull colors, and with 

 decidedly small bill. Schistacea, despite its name, is slate-colored only 

 in comparison with the Iliaca and Unalaschcensis fox sparrows. It is 

 among the brownest of the Schistacea group. Westward and south- 

 ward from the Great Basin, the habitat of schistacea, two lines of 

 variation may be followed, in both of which there is similarit}" in 

 development of the bill, while there are differences in color and pro- 

 portions. Southwest of the habitat of the small-billed and relatively 

 brown-colored schistacea lie the White Mountains, with the subspecies 

 canescens, also small-billed, but extremely gray in coloration. West 

 and south of this race lie in succession the gray-colored forms mono- 

 ensis, mariposae, and stephensi, progressively large-billed, a tendency 

 culminating in the enormous development of the bill seen in stephensi, 

 of the southern Sierra Nevada and the Boreal mountain tops of 

 extreme southern California (see fig. E). Besides the gray coloration 

 of these races they are further distinguished by greater length of tail. 



In the forms occurring in southern Oregon and northern California 

 another, somewhat similar line of development can be followed. 

 Starting again with the small-billed schistacea of the mountains of 



