372 VERTEBRATA. AVES. 



which it was intended."* Its peculiarity consists in 

 the bill, the lower mandible being much longer than 

 the upper, which is thin, and falls into the lower like 

 the blade of a knife into the haft. This singular 

 organ is thus used : the bird, skimming along the 

 surface of the ocean on its broad and powerful 

 pinions, opens its beak, and allows the lower mandi- 

 ble to cleave the water, scooping up the shrimps, 

 small fry, spawn, and mollusks that come in its way. 

 Many beautiful contrivances aid this operation, and 

 prevent attendant inconveniences, which we cannot 

 here particularize, amply sufficient, however, to jus- 

 tify Wilson's defence. 



FAMILY III. THE WHOLE-WEBS. 



The hind-toe in these birds is no longer free, but 

 united to the rest by the common membrane ; not- 

 withstanding which, they are enabled to perch on 

 trees, which few other swimming-birds can do. 

 " They are good swimmers, and some of them, at 

 least, can dive ; but the peculiar structure of their 

 feet, and the use which they make of them in walk- 

 ing up to the surface of the water after they have 

 plunged into it from a considerable height, render 

 them very distinct from the other sea-birds. "f 



* Am. Orn. vol. iii. p. 148. f Mudie, Birds, p. 152. 



