BIRDS 



293 



Subgenus Geospiza Gould. 



Geospisa Gould, Proc. Zool. Soc. Lond., p. 5, 1837. (Type, Geospiza mag- 

 nirostris Gould.) 



Adult males almost entirely black, under tail coverts edged with 

 whitish; sexes dissimilar; females never blackish ; the young resemble 

 the adult female ; bill conical but varies greatly in size and propor- 

 tions ; culmen generally straight. 



During their growth males of this subgenus go through Stages II to 

 VI. There is never at any age any plumage resembling the yellowish- 

 olive plumage of Stage I in Cactosfiza and Camarhynchus. Young 

 birds in the first plumage are in Stage II. The adult female is the 

 same as in the two preceding groups. 



The evolution of this subgenus is not so simple as that of Cama- 

 rhynchus. G. fuliginosa farvula we take as the most generalized 

 member of the group, partly because it is most convenient to form a 

 series beginning with it, and also because it resembles in size and 

 general proportions Geospiza ( Camarhynchus) prosthemelas with 

 which we started the Camarhynchus series. Starting with G. fuli- 

 ginosa parvula, and constructing the series according to the size and 

 shape of the bill, we can form a continuous line from G. fuliginosa 

 parvula to the more slender billed varieties of the same species, and 

 from these through G. debilirostris and G. septentrionalis to the 

 more slender billed members of the subgenus Cactornis. In the latter 

 subgenus there is again an evolution in the color, consisting of a 

 farther advance in melanism affecting die young of both sexes and 

 the adult females. From G. fuliginosa parvula also a second line 

 branches off in the opposite direction with regard to the size of the 

 bill, /. e., instead of becoming longer and more slender, the bill be- 

 comes proportionally larger and thicker at the base. This series 

 begins with G. fortis fortis, runs through the other varieties of the 

 same species, and then through G. darwini and G. strenua to G. 

 magnirostris . 



The species G. conirostris we place in the subgenus Cactornis. 

 This is contrary to any disposition of it made by other authors, but 

 the species have heretofore been grouped solely according to the 

 shape of the bill. This, we think, is certainly a mistake, for the color 

 is so characteristically different in the four groups as we here give 

 them, and manifestly so much more constant than the shape of the 

 bill, that we feel confident in relying on it as being a more important 

 character for classifying the members of the genus. However, the 

 bill in G. conirostris propinqua almost grades into that of G. scandens 

 Proc. Wash. Acad. Sci., January, 1904. 



