DIVISIONS OF BIRDS. 473 



which cannot fly, such as the Ostriches, Emeus, and Casso- 

 waries. It is characterised by the fact that the sternum has 

 no median ridge or keel for the attachm'ent of the great pec- 

 toral muscles. The sternum is therefore raft-like (ifrom the 

 Lat. rates, a raft), hence the name of the order. 



3. CARiNATiE. — This comprises all the living Flying birds, 

 and is characterised by the fact that the sternum is furnished 

 with a prominent median ridge or keel (carina) ; hence the 

 name of the order. 



This is probably the nearest approach to a strictly natural 

 classification of Birds which has yet been proposed ; but the 

 order Carinatce is so disproportionately large as compared with 

 the other two, that it would lead to considerable inconvenience 

 if it were to be adopted here. 



For the purposes of the present work it will be better to 

 adhere, with some modifications, to the classification of the 

 Birds originally proposed by Kirby, and since sanctioned by 

 the adoption of other distinguished naturalists. In this more 

 generally current, but certainly artificial, arrangement, the 

 Birds are divided into the following seven orders, founded 

 chiefly on the habits and mode of life, and on the resulting 

 anatomical or structural peculiarities. To these an eighth 

 order must be added for the reception of the Mesozoic bird, 

 the Archceopteryx, the discovery of which dates from a recent 

 period. Before entering upon a consideration of the indivi- 

 dual orders, it will be as well to present to the student, synop- 

 tically and in an easily-remembered form, the leading differences 

 between these eight orders. 



1. Natatores or Swimmers. — These are characterised by the 

 fact that the toes are united by a membrane or web ; the legs 

 are short, and are placed behind the point of equilibrium of 

 the body. The body is closely covered with feathers, and 

 with a thick coating of down next the skin. {Ex. Ducks, 

 Geese, Pelicans, Gulls.) 



2. Grallatores or Waders. — The Wading birds are charac- 

 terised by the possession of long legs, which are naked or 

 are not covered with feathers from the distal end of the tibia 

 downwards. The toes are long, straight, and not united to 

 one another by a membrane or web. {Ex. Curlews, Herons, 

 Storks.) 



3. Cursores or Runners. — The Cursorial birds have very 

 short wings which are not used in flight, and the sternum is 

 without a ridge or keel. The legs are exceedingly robust, and 

 there are only two, or at most three developed toes, the hind- 

 toe or hallux being always absent or quite rudimentary. The 



