BIRDS 



405 



most curious fact is the perfect gradation in the size of the 

 beaks in the different species of Geospiza, from one as large as 

 that of a hawfinch to that of a chaffinch, and (if Mr. Gould is 

 right in including his sub-group, Certhidea, in the main group) 

 even to that of a warbler. The largest beak in the genus 

 Geospiza is shown in Fig. i, and the smallest in Fig. 3 ; but 

 instead of there being only one intermediate species, with a 

 beak of the size shown in Fig. 2, there are no less than six 

 species with insensibly graduated beaks. The beak of the 

 sub-group Certhidea is shown in Fig. 4. The beak of 



I. Geospiza magnirostris. 

 3. Geospiza parvula. 



2. Geospiza fortis. 

 4. Certhidea olivacea. 



FINCHES FROM GALAPAGOS ARCHIPELAGO. 



Cactornis is somewhat like that of a starling ; and that of the 

 fourth sub-group, Camarh}'nchus, is slightly parrot -shaped. 

 Seeing this gradation and diversity of structure in one small. 

 intimately related group of birds, one might really fancy that 

 from an original paucity of birds in this archipelago, one 

 species had been taken and modified for different ends. In a 

 like manner it might be fancied that a bird original!}' a 

 buzzard had been induced here to undertake the office of the 

 carrion-feeding Polybori of the American continent. 



Of waders and water-birds I was able to get only eleven 

 kinds, and of these onh' three (including a rail confined to the 

 damp summits of the islands) are new species. Considering 



