10 THE BIRDS OF THE AIR. 
According to the Linnean system, which, 
however, I shall not rigidly follow in my ar- 
rangement, the Land Birds are divided into 
four classes ; the Rapacious Birds (accipitres) ; 
the Pies (pica?) ; the Passerine Birds (passeres) ; 
and the Gallinaceous Birds (gallinse): the Wa- 
ter Birds consist of two classes, the Waders 
(grallse) ; and the Swimmers (anseres). Of the 
Rapacious Birds, the bills are hooked, and 
there is an angular projection on the upper 
mandible; of the Pies, they are sharp-edged, 
compressed on the sides, and convex on the 
upper surface ; of the Passerine Birds, conical 
and sharp pointed ; of the Gallinaceous Birds, 
the upper mandible is considerably arched ; 
the Waders have a roundish bill, and a fleshy 
tongue ; and of the Swimmers, the bills are 
broad at the top, and covered with a mem- 
branaceous skin. 
