CLASS II. AVES: ORDER 6. CURSORES. 



259 



OSTRICHES. 



ORDER 6. CURSORES. 



Of the Cursores or Runners, which have been inckided by many authors among the Gralla- 

 tores, the Common Ostrich is a prominent example. They are nearly all large birds, with strong 

 and generally elongated legs ; the wings, on the contrary, are always reduced to a rudimentary 

 condition, although the bones in number and form agree with those of the wings of other birds.. 

 In consequence of this small size of the wings, these birds are quite incapable of flight, and the 

 only use they ever appear to make of them is to spread them out as if to catch the air, and thus 

 aid them in running. In accordance with this deficiency of the power of flight, the bones are 

 almost entirely destitute of the air-cells which in the ordinary birds give so much lightness to the 



