298 ON THE CLASSIFICATION OP BIRDS. 
Falco sparverius, the inner toe, with its claw, is scarcely 
shorter than the outer ; while in others, from the very 
same quarter of the globe, the disproportion is much more 
striyng : some of the large species, again, as the Falco 
peregrinus ? of New' Holland, have the tarsi proportion- 
ably much shorter; while in the Falco unicolor of Se- 
negal, the two lateral toes, when measured with their 
claws, are of precisely the same length : we cannot, how- 
ever, view this latter bird in any other light than as an 
aberrant species; for although its different locality might 
suggest the propriety of detaching it as the type of a geo- 
graphic group, yet this idea must be altogether aban- 
doned upon finding that theJ'a/coiiratfifc«(Sw.) of Brazil, 
(hitherto considered the same as xparverius'), actually 
possesses the same character, although the toes, divested 
of their claws, are slightly unequal. We have been 
much surprised, in fact, in discovering the great diver- 
sity in the proportionate length of the lateral toes in 
the typical falcons, — a variation which we do not re- 
member to have jnet with in any other subgenus of 
ornithology, and which, therefore, requires particular 
attention. The general character of the majority of the 
species, as before remarked, is that of having the inner 
toe decidedlyshortcr than the outer, although witli a much 
larger claw : of this the well-known sparverius, a bird 
in almost every collection, is a good example. But this 
deficiency in the length of the inner toe is often made 
^ by its claw ; which thus brings it equal to the other, 
if both are measured in their full length : such is the 
case in Falco unicolor, and in some of the supposed 
varieties of sparverius. In others, however, from 
tropical America, the outer toe of the claw is by far the 
longest : while, in an undescribed kestrel from Western 
Africa, this proportion is actually reversed, — the two 
lateral toes only are perfectly equal ; but as the claw of 
the inner one is much longer than that of the outer, it 
gives to this claw the appearance of being longer than 
the other. The same structure we observe in a kestrel- 
like species from Java, which is probably the F. tin- 
