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Show BIRDS. 99 Mandihula superiori tomiis medium versus sinum exltibentibus, ad mandibulce inferioris p1·ocessum ?'ecipiendum. Mandihula inferior ad basin lata, hoc infi·a oculos tendente. Alm mediocres remige primo paulo breviore secundo, ltoc longissimo. Cauda brevissima et cequalis. Tm·si magni et validi, digito postico, cum ungue 1·obusto et digito intermedio breviore; digitis externis inter se cequalihus at digito postico brevioribus. Color in maribus niger, infmm.fuscus. This singular genus* appears to be confined to the islands of the Galapagos Archipelago. It is very numerous, both in individuals and in species, so that it forms the most striking feature in their ornithology. The characters of the species of Geospiza, as well as of the following allied subgenera, run closely into each other in a most remarkable manner. In my Journal of Researches, p. 475, I have given my reasons for believing that in some cases the separate islands possess their own representatives of the different species, and this almost necessarily would cause a fine gradation in their characters. Unfortunately I did not suspect this fact until it was too late to distinguish the specimens from the different islands of the group; but fr·om the colJection made for Captain FitzRoy, I have been able in some small measure to rectify this omission. In each species of these genera a perfect gradation in colouring might, I think, be formed from one jet black to another pale brown. My observations showed that the former were invariably the males; but Mr. Bynoe, the surgeon of the Beagle, who opened many specimens, assured me that l1e found two quite black specimens of one of the smaller species of Geospiza, which certainly were females : this, however, undoubtedly is an exception to the general fact; and is analogous to those cases, which Mr. Blyth«< has recorded of female linnets and some other birds, in a state of high constitutional vigour, assuming the brighter plumage of the male. The jet black birds, in cases where there could be no doubt in regard to the species, were in singularly few proportional numbers to the brown ones: I can only account for this by the supposition that the intense black colour is attained only by three-year-old birds. I may here mention, that the time of year (beginning of October) in which my collection was made, probably corresponds, as far as the purposes of incubation are concerned, with our autumn. The several species of Geospiza are undistinguishabJe from each other in lmbits; they often form, together with the species of the following subgenera, and likewise with doves, large irregular flocks. They frequent the rocky and extremely arid parts of the land sparingly covered with almost naked bushes, near the coasts; • This genus, and the following sub-genera, wore named by .l\lr. Gould at a meeting of tho Zool. Soc. Jan. I 0 1837, p. 4, of Proceedings. + Remarks on the Plumage of Birds, Charlsworth's Mag. of Nat. History, vol. i. P· 4-80. |
