7$ ELEMENTS OF COMPARATIVE ZOOLOGY, 



on external features. The student should, however, re- 

 member that the so-called "orders" are in no wise equiva- 

 lent to orders in other groups. 



ORDER I. STRUTHII (Ostriches). 



The ostrich-like birds have long running legs and wings 

 so reduced as to be useless in flight, and with this the keel 

 of the sternum (p. 74) has disappeared. The foot contains 

 usually three, occasionally but two, toes. These birds are 

 mostly large, and embrace the true ostriches of Africa, so 

 valuable for their feathers; the South American nandus; 

 the emeus and cassowaries of Australia, and the nearly 

 wingless kiwi of Australia. 



* 

 ORDER II. RASORES (Scratching Birds). 



These, like all the remaining birds, have a keeled sternum. 

 They have a weakly curved beak, feet well fitted for run- 

 ning, with three toes in front, and a fourth at a higher 

 level behind. Here belong the grouse, the pheasants, and 

 the domestic fowl and turkeys, as well as a considerable 

 number of tropical forms. Our common hens, in all their 

 numberless varieties, are descendants of the wild fowl of 

 India. The turkeys are natives of America. 



ORDER III. NATATORES (Swimming Birds). 



In these the short feet are adapted for swimming by 

 having a web between the anterior toes. The body varies 

 greatly in shape. In the penguins the wings have lost the 

 powers of flight, the wing-feathers being short and scale- 

 like. On the other hand, they are strong swimmers, and 

 the loons almost equal them in this respect. The other ex- 



