DIVISIONS OF BIRDS. 295 



Amongst the more important tj'pes of the Nataiores may be enu- 

 merated the Penguins (Spkeuiscidce), the Auks {Alcid<e), the Gulls 

 and Terns (Laridce), the Petrels {Procellaridce), the Pelicans {Peli- 

 camis), the Cormorants {Phalacrocorax), the Gannets {Sula), the 

 Ducks {Anatidoe), the Geese {ATiseriiice), and the Swans (Cygnidce). 



The Penguins and Auks, with their allies the Divers, Guillemots, 

 and Grebes, have rudimentary, or at any rate small, wings, and are 

 all more at home in the water than upon land. In the Penguins 

 (tig. 209), the wings are rudimentary, and covered with a scaly 

 skin. They are used by the bird as iins in swimming under water. 

 The Penguins are confined to the southern hemisphere. The Gulls, 

 Terns, and Petrels, on the contrary, are all birds of powerful flight, 

 and some of them, such as the Albatross, are habitually found hun- 

 dreds of miles from the nearest land. The Pelicans, with their 

 allies the Cormorants, Frigate-birds, and Darters, are excellent 

 fliers, and also not uncommonly perch on trees, which few Nata- 

 torial birds do. They are distinguished by having the hinder toe 

 directed inward, and united to the innermost of the front toes by a 

 continuous membrane. The Ducks, Geese, and Swans have the bill 

 very much flattened (fig. 208 A), and covered by a soft skin. The 

 edges of the bill are also furnished with a series of transverse plates, 

 which form a kind of fringe or " strainer," by means of which these 

 birds sift the mud in which they habitually seek their food. 



Order II. Grallatores. 



The Wading Birds for the most part frequent moist situations, 

 such as marshes and shallow ponds, the shore of the sea or the banks 

 of rivers or lakes, though some of them keep entirely, or almost 

 entirely, to the dry land. In accordance with their semi-aquatic, 

 amphibious habits, the Waders are distinguished by the great length 

 of their legs — the increase in length being chiefly due to the elonga- 

 tion of the tarso-metatarsus. The legs (fig. 210, A) are also un- 

 feathered and naked as far as the lower end of the tibia, at any rate. 

 There are three anterior toes, and usually a short hind-toe ; but the 

 toes are never completely webbed, though they are sometimes par- 

 tially palmate. The wings are long, and the power of flight is 

 usually considerable ; but the tail is very short, and its function as 

 a rudder is chiefly transferred to the long legs, which are stretched 

 out behind in flight. The beak is almost always of great length, 

 generally longer than the head (fig. 210, B), and usually more or less 

 pointed, though it is sometimes flattened. In the Avocet (C) the 

 Ijill is curved upwards, instead of being straight, or bent down- 

 wards, as is generally the case. The typical Waders, as before said, 



