BIRDS. 147 



and. even tone of voice. Secondly, there are two 

 owls, representing the short-eared and white ham- 

 owls of Europe. Thirdly, a wren, three tyrant fly- 

 catchers (two of them species of Pyrocephalus, one 

 or both of which would be ranked by some orni- 

 thologists as only varieties), and a dove — all anal- 

 ogous to, but distinct from, American species. 

 Fourthly, a swallow, which, though differing from 

 the Progne purpurea of both Americas, only in be- 

 ing rather duller coloured, smaller, and slenderer, 

 is considered by Mr. Gould as specifically distinct. 

 Fifthly, there are three species of mocking-thrush — 

 a form highly characteristic of America. The re- 

 maining land-birds form a most singular group of 

 finches, related to each other in the structure of 

 their beaks, short tails, form of body, and plumage : 

 there are thirteen species, which Mr. Gould has 

 divided into four sub-groups. All these species 

 are peculiar to this archipelago ; and so is the whole 

 group, with the exception of one species of the sub- 

 group Cactornis, lately brought from Bow Island, 

 in the Low Archipelago. Of Cactornis, the two 

 species may be often seen climbing about the flow- 

 ers of the gi-eat cactus-trees ; but all the other spe- 

 cies of this gi'oup of finches, mingled together in 

 flocks, feed on the dry and sterile ground of the 

 lower districts. The males of all, or certainly of 

 the greater number, are jet black, and the females 

 (with perhaps one or two exceptions) are brown. 

 The most curious fact is the perfect gi-adation 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. 1, 

 and the smallest in Fig. 3 ; but, instead of there 



