278 



BRANCH CHORDATA 



Classification. — The classification of birds seems to be chaotic, 

 no two zoologists agreeing. Some claim birds are of too recent 

 origin geologically to have differentiated as yet into well- 

 marked orders. They might be grouped as land birds and water 

 birds, or as runners and flyers, but such classification would not 

 be scientific. If there were a geologic series showing the nat- 

 ural affinities, a natural classification would be a comparatively 

 easy task, as all classification should be based on development 

 and structure. 



Division A. Rati't^ 



Living birds are divided into two groups, the Rati'tas and the 

 Carina'tce. Ratitse are birds with a raft-like or keelless breast 

 bone, wings rudimentary or too small for flight, legs large, 

 strong, and fitted for rapid running. As examples may be 



Fig. 226. — Ap'teryx aiislral'is, a nocturnal flight li'.ss bird with nostrils near 

 the end of the bill. The external wing is shown in the upper part of the out. 

 (Romanes.) 



named the ostrich, emu, rhea, cassowary, kiwi (Fig. 22G), and 

 the extinct moa and other ostrich-like birds. None of these 

 birds is native to the United States, but in recent >ears they 

 have been imported into some parts of the west, as Pasadena, 

 California, Salt River Valley, Arizona, and some other dry, warm 



