294 CLASS AVES. 



behind in flight, contrary to others, which fold them 

 under the belly. 



"We establish in this order five principal families, 

 and some isolated genera. 



Nevertheless the family of 



Brevipennes, 



although similar, in general, to the other waders, 

 differ from them considerably in one point, namely, 

 the shortness of their wings, which deprives them of 

 the faculty of flight ; in their bill, moreover, and the 

 nature of their food, they approach the characters of 

 the gallinaceous birds. 



It appears as if the muscular force of nature would 

 be insuflicient to move wings so extended as the 

 bulk of these birds would have required to sustain 

 them in the air. Their sternum is a simple buckler, 

 and is destitute of that ridge observable in other 

 birds. The pectoral muscles are very slender, but 

 their posterior extremity has all the strength of 

 which the wings are deprived ; the muscles of 

 the thighs, and especially of the legs, are enormously 

 thick. 



None of them have a thumb ; the number of pha- 

 langes is as follows, commencing at the internal 

 toe : the ostrich, four and five ; the American 

 ostrich, or nandou, and cassowary, three, four, and 

 five ; returning to the usual number in birds. Two 

 genera of them are made. 



