506 ORDER NATATORES ; GENERAL CHARACTERS. 



for their harsh and discordant voices, but for the sharp hard 

 spurs with which the wings are armed at the shoulder joint. 

 These are very efficient weapons of defence; and enable the 

 birds to resist the attacks of the Snakes, which infest the places 

 they inhabit. One species is also remarkable for the possession 

 of a slender pointed horn, three or four inches in length, which 

 arises from the top of the head, and curves gently forwards. 

 The use of this singular appendage is unknown. 



ORDER VII. NATATORES. 



453. The Swimmers or Web-footed Birds are, of all the 

 orders of the feathered race, the most easily distinguishable, on 

 account of the peculiar structure and position of their oar-like 

 feet. These members are placed very far back, so as to be more 

 efficient instruments for the propulsion of the body in water ; 

 but this arrangement gives to the Birds an awkward waddling 

 gait on land. The feet are always webbed ; that is, the toes 

 are connected together by a membrane ; but this in a different 

 manner in the different families. In making the swimming- 

 stroke, the foot is first drawn forwards ; and the toes then close 

 together, and the webs fold, so as to offer to the water the least 

 possible resistance : but when the back-stroke is made, the toes 

 spread out, so as to present a large surface to the water. The form 

 of the body is boat-shaped, so as to move through the water with 

 little resistance ; and the neck is usually long, so as to enable the 

 Bird to plunge the head far down in search of its food. The tail is 

 generally short ; in some instances it is composed of rigid feathers, 

 and serves as a rudder to direct the Bird in the act of diving ; 

 but in some of the aquatic Birds it is very long, and guides them in 

 their rapid flight. The form and size of the wings, and the powers 

 of flight, vary greatly in the different tribes of this order ; some of 

 them are almost unsurpassed in the extent of their wings ; whilst 

 in others, these organs are so short as to be utterly useless in 

 flight, and can be only used as paddles for urging them througl 

 the water. The plumage is dense, and is oiled by a secretic 



