NATURAL SCIENCES OF PHILADELPHIA. 
375 
the genu3, and not existing in any other, though there is seen an approach to 
it in Canndbina. 
In the type of the genus the bill is exceedingly acute and much compressed, 
the lateral outlines even concave. From this character of bill, there is seen 
through A. Ilolbolli and fuscescens, a gradual transition to the A. rostratus , 
where the bill is much larger, less compressed and acute, and more full and 
turgid. The plumuli are also considerably shorter and more scant ; and the 
whole appearance of the bill much that of a Cannabina or even of a Carpodacus. 
The wings are very constant throughout the genus, differing scarcely appre- 
ciably in length or pointedness in the different species, though the proportions 
of the primaries vary considerably in the same species. Exactly the reverse, 
however, is the case with regard to the feet ; i. e. the characters differ con- 
siderably in the different species, but always are quite constant in each. Thus 
in linarius , rufescens, Ilolbolli, fuscescens and rostratus the proportions of tarsus 
and toes are much the same, the difference in absolute length being only pro- 
portional to the size of the birds. In exilipes the feet are smaller and weaker, 
and the toes shorter, the difference being specially noticeable in the middle 
toe, which, with the claw, is shorter than the tarsus. In canescens, on the other 
hand, the feet are larger and stronger, even more so than is proportional to 
the greater size of the bird ; but the toes are excessively short, so much so 
that even the unusually long claw does not make the middle toe equal to the 
tarsus. The tail differs but slightly, if at all, in the different species ; for 
though A. canescens is spoken of by authors as having a comparatively longer 
tail than has linarius , the difference seems hardly more than is proportional to 
the greater size of the bird. 
With respect to color, the species present a remarkable similarity, not only in 
the pattern of coloration, but also in the tints.^ In all, there is found the crim- 
son pileum, which varies in size, and in the intensity of the color, with sex and 
age. It has sometimes a peculiar coppery or brazen reflection, very different 
from the usual deep crimson tint. The breast, with the sides of the head and 
body to some distance, as well as the rump, are tinged with rosy or carmine. 
In the examination of a great number of specimens I have noticed a fact that i 
have seen nowhere stated. It is that the depth and intensity of the color on 
the breast and rump is in direct proportion to the lightness or darkness of the 
general colors of the bird. Thus, in rostratus and fuscescens , the rosy on the 
breast becomes so bright as nearly to equal in intensity the crimson of the 
crown. Canescens and exilipes present the other extreme, the rosy of the breast 
being very light, scarcely more intense than that on the rump. Linarius , and 
rufescens and Holbolli are intermediate between the two extremes in this respect. 
The females of every age, and the very young males, either want entirely this 
rosy on the breast and rump, or else show but very slight traces of it. All the 
species are streaked above ; the feathers having very dark centres and light 
borders ; but in fuscescens and rostratus these borders are so narrow that the 
parts appear almost uniformly dusky. In canescens and exilipes these streaks 
disappear on the rump, leaving that part pure white ; in the other species of the 
genus the rump is thickly streaked. In all, the sides of the body are more or 
less streaked with dusky ; and here the same rule holds good as with regard 
to the rosy of the breast. In the darkest colored species — A. fuscescens and 
rostratus — the streaks are most numerous, darkest, and most distinctly defined ; 
they become less numerous and distinct in linarius and exilipes , and are some- 
times almost wanting in canescens . In the females these streaks extend quite 
across the breast. 
It will thus be seen that the species of the genus are all very closely related ; 
the characters, when taken from the colors, being chiefly those of intensity, 
and when based upon form, being found in the varying combination of several 
features. A. rostratus , indeed, differs from the others in the possession of a 
much larger and more turgid bill ; but as the other characters agree strictly 
with the type, and especially as the transition from one extreme to the other, 
1861.] 
