572 CRIBRATORES. SIFTERS. 



dents of British Ornithology, we are not concerned, I have 

 shewn, by the description of its digestive organs, in the fifth 

 volume of Mr. Audubon's Ornithological Biography, to be 

 nothing else, as some would say, than " a modified Goose." 

 Setting aside these for the present, let us take a general view 

 of the main body. 



The species generally known as Swans, Geese, and 

 Ducks appear to form a single, well-defined family, of which 

 the members present various gradations. Thus, the bill may 

 be as long as the head, or a little longer, or shorter in all 

 degrees to half its length. It is always higher than broad at 

 the base, but it may be of the same uniform breadth to the 

 end, or it may become narrower, or in a few instances 

 broader. Its terminal unguis may be round, elliptical, 

 oblong, obovate, triangular or linear, very convex or nearly 

 flat; moderately, much, or abruptly decurved, sometimes, 

 though very rarely, so much as to have its edge directed 

 backwards. The margins of the upper mandible may be 

 arched, sinuate, or straight. The lamellae may be large or 

 small, distant or close, prominent or scarcely elevated, and 

 their outer ends may be rounded, triangular, tooth-like, or 

 sometimes acicular or capillary, projecting far beyond the 

 margin, or moderately, or slightly, or not at all. So is it 

 with the other organs. The legs may be long, short, or very 

 short; the tarsi roundish or compressed. The hind toe, 

 always small and elevated, may be free, or with a slight 

 membrane, or having a membranous lobe, connecting it in 

 some degree with the base of the two-lobed membrane of 

 the inner toe. The interdigital membranes may be full, even 

 at their margin, or emarginate in various degrees, or in a 

 few instances dimidiate. The claws, never large, may be 

 compressed or flattened, acute or obtuse. The wings may 

 be long, of moderate length, or very short, convex in various 

 degrees, and with a varying number of quills ; the tail ex- 

 tremely short, short, moderate, or long, with from twelve to 

 twenty-four feathers. The digestive organs vary less in their 

 general characters, but yet exhibit differences of considerable 

 amount. The trachea, however, presents extraordinary pecu- 

 liarities, being sometimes nearly of uniform width, some- 



