The Tetrapoda: Amphibia, Reptiles, Birds 623 



of the birds of the North American continent. The birds of Europe 

 also show these same mass movements toward Africa. 



Economic Importance of Birds. — Economically birds may be 

 ranked among the most important of the vertebrates. Many of the 

 wild birds feed largely on noxious insects and weed seeds. Without 

 their constant feeding, both insects and weeds would be even more diffi- 

 cult to control. The hawks and owls feed largely on small rodents and 

 aid materially in reducing the population of these destructive animals. 



Birds have always been an important food item to human beings, 

 and their present commercial prodviction constitutes an important in- 

 dustry. Both their flesh and eggs are highly valued. Of somewhat 

 lesser importance are their feathers. 



To the sportsman, game birds such as quail, ducks, geese, and pheas- 

 ants are important for the pleasure which he gets from hunting them. 

 Finally there are the many uncounted persons who gain unmeasured 

 pleasure from their observation and study of wild birds. Certainly all 

 of our lives would be somewhat drabber without the songs and bright 

 colors of our common birds. 



The Orders of Birds 



The 30,000 recent and fossil-known birds are grouped into some 

 thirty orders. These are as follows : 



Subclass 1. Archaeornith«s. 



Order 1. Archaeopterygiformes. Examples: Archaeoptery.v and Archaeornis. 



Subclass 2. Neornithes. 



Superorder Odoniognathae... New World toothed birds. 



Order 1. Hesperornithiformes. Examples:.. Hesperornis from Cretaceous 

 deposits of Kansas and Montana. Were diving, swimming, flightless 

 birds with teeth set in grooves and with webbed feet, and were about 4 

 feet in length. 



Order 2. Ichthyornithiformes. Example: Ichthyornis from Cretaceous de- 

 posits of Kansas. Had w-ell-developed wings, teeth set in sockets; were 

 small, about the size of a pigeon. 



Superorder Palacognathae. Walking birds, flightless, without teeth. 



Order 1. Caenagnathiformes. Example. Caenagnathus, fossil form from upper 

 Cretaceous. 



Order 2. Struthioniformes. Example: ostriches of Africa. 



Order 3. Rheiformes. Rhea, large running birds from South America. 



Order 4. Casuariiformes. Examples: cassowaries from Australia and emus 

 from New Guinea. 



