KEEL-BREASTED BIRDS. 237 



powerful, and provided with only two toes, the inner one 

 being twice as long as the outer. 



VALUE. The oil, skin (leather), and feathers are all used. Os- 

 triches are now farmed in this country for their feathers. 



FIG. 277. Ostrich (Struthio cametus) running at full speed. 



Sub-Class IV. KEEL- BREASTED BIRDS (Carinata). 



General Characteristics. All the rest of the birds are 

 included in this class. They are distinguished by a keeled 

 sternum or breastbone, the fore-limbs in the higher forms 

 being developed as organs of flight. 



Order I. Penguins (Sphenisci). The Penguins (Fig. 

 278) are confined to the Antarctic region, and are remark- 

 ably fish-like in their habits. The wings are small, and cov- 

 ered with scale-like feathers, and are used, as well as their 

 webbed feet, as paddles. The king-penguin (Aptenodytes 

 longirostris] is one of the largest, attaining a height of three 



