VERTEBRATA. 



275 



the rest of the birds, and is divided into sub-groups 

 according to characters which are dependent on the 

 respective modes of life adopted by birds. These are 

 as follows: — The iVaiaio?-eSj or SwiinmingBirds, include 



Fig. 103. — 4, Breast-bone of a Ratite bird, the Oatricii, sliowin/]; absence of 

 keel. .B, Breasfc-bone of a Garinate bird, the Gaillemot, showing presence of 

 keel. (From Proc. ZotA. Soc, June, 1885.) 



the gullsj gannets, divers/ducks and geese, and swans, 

 and also the penguins, which differ from these in being 

 swimming birds only, and incapable of flight. The 

 typical Ch'allatores, or Waders, have long legs adapted 



