COLLECTION OF BIRDS. 383 



ashy blue on the back and white on the belly, in 

 the adults; when young they are of a greyish 

 colour. Twenty-three species of sea-swallows 

 [sterna) fill the lower shelves of this case ; they 

 owe their name to the extraordinary length of 

 their wings and tails, and to the rapidity of their 

 flight. They skim the surface of the water to 

 catch molluscas and small fish. Some species 

 ascend large rivers, others keep on the lakes. 

 The cut- waters (rhyncops) , which are at the bot- 

 tom of the case, are distinguished from all other 

 birds by the extraordinary form of their beaks ; 

 the upper mandible of which is like the blade of 

 a knife, and much shorter than the inferior. This 

 singular form renders it impossible for the bird 

 to pierce any thing with its beak, but he uses it 

 when flying over the surface of the waves, to 

 seize the molluscas which float on them. One of 

 these species, the rhjncops nigra, is commonly 

 found in the seas of the West Indies ; the other, 

 but recently known, inhabits the Austral ocean. 



The fifty-second and fifty-third cases contain 

 the totipalmesy so named because their great toe 

 is united to the others by a membrane ; notwith- 

 standing this formation they perch upon trees. 

 The largest of them is the pelican, which is re- 

 markable for the length of its beak, whose lower 

 mandible supports a naked dilatable membrane 9 



