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ON THE CLASSIFICATION OF BIRDS. 



Falco sparverius y 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 

 striking : 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 the Falco graciles(j$w.) of Brazil, 

 (hitherto considered the same as sparverius), 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 met 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 decidedly shorter than the outer, although with 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 

 up 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- 



