SWAN. NATATORES. CYGNUS. 287 



ridge of the keel, instead of narrowing downwards as in the 

 other species, gains breadth as it approaches to the posterior 

 extremity of the keel, or where the cavity widens and occu- 

 pies a lateral portion of the sternum. In its habits the pre- 

 sent bird resembles the Whistling Swan, and is, like it, a na- 

 tive of the Arctic Regions of Europe, Asia, and America, as it 

 would appear to be the Lesser Swan mentioned by HEARNE 

 (in his " Journey to the Northern Ocean") as visiting Hud- 

 son's Bay in summer. It feeds upon aquatic vegetables and Food, 

 seeds. As might be expected from the form of the lower 

 larynx, and that part of the trachea adjoining it, its voice is 

 much weaker than that of the preceding species. 



PLATE 47.* Represents the Cyg. Bewickn of nearly one-half 



the natural size. 



Bill, as far as the nostrils, black ; the base orange-yellow ; General 

 and the upper mandible having a tubercle or knob, tion. 

 varying in size according to the age of the bird. Fore- 

 head and region of the eyes with numerous specks of a 

 pale orange-yellow. In adults, the rest of the body 

 pure white, and in the young pale-grey. Tail wedge- 

 shaped, and consisting of eighteen feathers. Legs black. 



SUBFAMILY ANATINA. 

 GENUS TADORNA, FLEM. SHIELDRAKE. 



GENERIC CHARACTERS. 



Bill shorter than the head, higher than broad at the base, 

 depressed or concave in the middle, with the tip flattened and 

 turning upwards, nearly of the same breadth throughout ; 

 dertrum, or nail, abruptly hooked. Upper mandible laterally 

 grooved near the tip ; under mandible much narrower than 

 the upper one, and, when closed, hidden by the deflected 



