﻿10 ON THE CLASSIFICATION OF BIRDS. 



The head is always large in proportion to that of other 

 types; and these birds either actually live upon the sur- 

 face, 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, belongs to no other 

 type. The tail is generally very short, and great bulk 

 of body is a frequent accompaniment of the natatorial 

 structure ; witness the gigantic albatross, the pelicans, 

 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 grallatorial, 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 

 the 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 cf 

 the typical Grallatores, or waders, and their represent ■ 

 atives, the Trochilidce. The smallest birds, no less than 

 the smallest quadrupeds, are of this type, which is again 

 represented by the little gliriform Mammalia, The 

 Hasorial type is inferior only to the natatorial in bulk. 

 Birds belonging to it have the tail greatly developed as 



