BIRDS. 
99 
Mandibuld superiori tomiis medium versus sinum exkibentibus , ad mandibulce inferioris 
processum recipiendum. Mandibula inferior ad basin lata, hoc infra oculos tendente. 
Alee mediocres remige primo paulo breviore secundo , hoc longissimo. 
Cauda brevissima et cequalis. 
Tarsi magni et validi, digito postico, cum ungue robusto et cligito intermedio breviore ; 
digitis externis inter se cequalibus at digito postico brevioribus. Color in maribus 
niger, in fcem.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, 1 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 spe- 
cimens from the different islands of the group ; but from the collection 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 he 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 undistinguishable from each other in habits ; 
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, were named by Mr. Gould at a meeting of the Zool. Soc. Jan. 10 
1 837, p. 4. of Proceedings. 
t Remarks on the Plumage of Birds, Charlsworth’s Mag. of Nat. History, vol. i. p. 480. 
