The largest beak in the genus Geospiza is shown in (Plate 81) Figure 1, and the smallest in Figure 3; but instead of there being only one intermediate species, with a beak of the size shown in Figure 2, there are no less than six species with insensibly graduated beaks.

The beak of the sub-group Certhidea, is shown in Figure 4.

The beak of Cactornis is somewhat like that of a starling, and that of the fourth sub-group, Camarhynchus, 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, originally 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 only three (including a rail confined to the damp summits of the islands) are new species.