_ TYPICAL GROUPS CONNECTED. 59 
beyond the length of the nostrils: the first quill (g) is 
scarcely perceptibly shorter than the two next: the tail 
is very slightly forked, or rather divaricated. This, in 
short, is the typical structure of the group: as we 
proceed, however, in the series of species, we trace a 
slight increase in the breadth of the bill. This is very 
observable in the Sylvicola canadensis (b), upon which 
Wilson makes the following remark: ‘ Though the 
form of the bill of this bird is decidedly that of a 
warbler, it has much of the flycatcher in its manners.’ 
The Sylvicola coronata advances us a step further (c) ; 
and accordingly, Wilson remarks, that “although the bill 
of this species obliges me to arrange this bird with the 
warblers (Sylvicola), yet in his food and all his motions 
he is decidedly a flycatcher.’ Again, on the black- 
poll warbler (S. striata), our author writes, “ This 
bird may be considered as occupying an intermediate 
Station between the flycatchers (Setophaga Sw.) and 
the warblers (Sylvicola Sw.) ; having the manners of 
the former, and the bill, partially, of the latter.” The 
change gradually continues, until finally, upon reaching 
the hooded flycatcher (d), the most aberrant form of our 
genus Setophaga, but which is a Sylvia (Sylvicola Sw.) 
both of Vieillot and Bonaparte, our author bursts out 
with the following exclamation: —‘‘ Why this bird 
should have been arranged with the warblers (Sy/vé- 
cola) is to me unaccountable, as few of the Muscicapa 
(Setophaga) are more strongly marked than the species 
now before us; it is perpetually in pursuit of winged 
insects.” Now, in what respect does this bird differ, 
in its externa! structure, from the Sylvicola americana ? 
simply in having the bill somewhat broader at the base, 
and the bristles extending to half the length of the 
bill; the wings, the feet, and the tail, are precisely the 
same, with this exception only, — that the two outer 
feathers of the tail are very slightly graduated, and 
shorter than the others. The next link is furnished 
by Setophaga canadensis(e),where all the tail feathers are 
graduated ; and this is immediately followed by the type 
