CHAPTER XV. 

 BRANCH CHORDATA. 



CLASSIFICATION OF AVES. 



EXISTING birds are divided into two great groups. All 

 flying birds have the keeled breastbone, and from this fact 

 of structure are placed together in the division Carinatae, 

 meaning " keeled." The ostrich has no keel on the breast- 

 bone, hence is placed in the division Ratitae, from a word 

 meaning " raftlike," referring to the shape of its breastbone. 



DIVISION I. RATITAE. 



The best-known representative of this division is the 

 African ostrich. It cannot fly, the wings being small ; but 

 it is a swift runner, equaling a horse in speed. The breast- 

 bone is not only without a keel, but is relatively very small, 

 as might be expected since there are no large flying 

 muscles. The feathers on the wings and tail have no 

 booklets on the barbules ; the result is a plume instead of 

 a firm vane as in the flying birds. These plumes have 

 been valued as ornaments from the earliest time, and now 

 the rearing of ostriches for the plumes is an important 

 industry in South Africa and southern California. 



The ostrich is also noteworthy from its size, being the 

 largest of existing birds, standing from six to eight feet 

 high. It has but two toes on each foot. In the same 

 division are also the South American ostrich, the emu 

 of Australia, the cassowary of Australia and the East 

 Indies. The kiwi of New Zealand has bristlelike feathers, 



