On the Groups of the Falconidce. 341 



On looking back to the characters that have been particularized 

 as tending to distinguish the foregoing groups, it is evident that 

 they differ considerably in their relative importance : some being 

 strong, prominent, and ostensible, while others may be considered as 

 comparatively of inferiour moment. How far the latter are of suf- 

 ficient consequence to form a ground for generick distinction is a 

 question which I should prefer to propose to others, rather than at- 

 tempt at present to determine myself. It is difficult indeed to lay 

 down any rules for deciding what would generally be allowed to 

 be a true generick difference, Much of course must depend upon 

 the nature of the group to be subdivided, and much also upon its 

 extent. The species of some groups, though considerable in 

 point of number, are yet often so uniformly characterized, that it 

 is not easy to seize upon any ostensible peculiarity that divides 

 them. Here where the extent calls for subdivision, and yet where 

 no apparently important or distinctive character is observable, it 

 becomes a question, whether it may not be expedient to seize upon 

 any character that is at all tangible, for that necessary purpose, 

 even though it may at first sight appear of inferiour conse- 

 quence. Generally speaking I confess myself an advocate for all 

 such subdivisions ; and chiefly for the reason, that it is impossible 

 for us to form a determination respecting the importance of any 

 character of which we know not the actual use. What may appear 

 to us trivial may in reality tend to some material purpose. The 

 cylindrical ungues of Pandion, and Elanus, for instance, or their 

 reticulated acrotarsta, though to us apparently indicating nothing 

 important to the economy of the bird, may yet be conducive to 

 some material function unknown to us. And indeed when we 

 consider the fact, that these and similar characters, are not to be 

 found indiscriminately attached to the groups of the Falconidce., 

 but united together with considerable appearance of regularity and 

 design, we should feel less confidence in asserting their want of 

 importance. But the question of what actually constitutes a gene- 

 rick difference is one which requires more attention than can be 

 bestowed upon it in a mere casual reference. I hope hereafter to 

 be able to enter more carefully and more at large upon the sub- 

 ject. In introducing at present those genera into the foregoing 



