10 
ON THE CLASSIFICATION OP BIRDS. 
The head is always large in proportion to that of other 
types; and these birds either actually live upon the sur- 
fece^ or habitually frequent the vicinity, of the water. 
They are well distinguished from those of the next, or 
grallatorial type, by the excessive width of their mouth, 
—a formation admirably adapted to the manner in which 
they feed, which is almost always, like swallows, upon 
the wing : this peculiarity, indeed, telongs to no other 
‘yP®- 'Phe tail is generally very short, and great bulk 
of body is a frequent accompaniment of the natatorial 
structure ; witness tlie gigantic albatross, the pelican.s, 
and the penguins, while the ostrich and the cassowaries, 
although not swimmers, are, nevertheless, the natatorial 
types of the gallinaceous order. The powers of flight 
are much diversified, but they are, in general, very 
great ; instances of this swiftness occur in the swallows, 
petrels, flycatchers, and many other groups belonging to 
this form. The graUatorial, or tenuirostral type, is 
shown in birds, as in quadrupeds, by a great slenderness 
and elongation of the jaws, muzzle, or bill; for all these 
are merely different terms to express nearly the same 
thing ; the notch in the bill, when it exists, is very 
slight, and the feathers of the front are considerably 
advanced upon the base of the upper mandible. The 
opening of the nostrils is very long, often tumid, but 
never round. Great swiftness, either of foot or of wing, 
is a constant indication of this type. Sometimes, as in 
file snipes, both these characters are united ; at other 
times, as we see in the humming birds, this swiftness is 
confined only to flight; while in some few, as the 
flamingo, the wings are short, but the feet very long. 
The aperture or gape of the mouth is generally very 
small, as in all suctorial animals ; witness the whole of 
the typical GraUatoveHy or waders, and their represent ■ 
atives, the TrocMlidts. The smallest birds, no less than 
the smallest quadrupeds, are of this type, which is again 
represented by the little glirifonn Mammalia. The 
Ranorial type is inferior only to the natatorial in bulk. 
Birds belonging to it have the tail greatly developed as 
