248 CURSORES. 



ORDER VI. CURSORES. 



birds.) 



In the Poultry we have seen the power of fly- 

 ing, so characteristic of a bird, reduced to a feeble 

 and imperfect condition ; we come now to species 

 in which it is totally lost, the wings themselves in 

 some being reduced to mere rudiments. On the 

 other hand, as the reduction and gradual extinction 

 of one set of organs are frequently connected with 

 the increased development of another series, in some 

 respects correspondent, so here we find the poste- 

 rior limbs increasing in size and muscularity with 

 the decrease of the anterior. The pectoral muscles 

 are small and slender, and the breast-bone (sternum) 

 presents an uniform convex surface, like that of a 

 shield, utterly destitute of even the rudiment of the 

 keel, which is so large and prominent in the Swal- 

 lows, Humming-birds, and other powerful fliers. 



The Runners are all large birds, most of them 

 equalling, if not exceeding, the average height 

 and bulk of the Mammalia, to which indeed they 

 exhibit a closer approximation than any other of 

 the feathered tribes. The single Family in which 

 they are all included (for the Bustards seem to be 

 more allied to the Waders, and the place of the 

 extinct Dodos is yet doubtful) is almost confined 

 to the Southern Hemisphere, one species alone 

 reaching to the north of Africa and Arabia. They 

 chiefly inhabit immense plains. 



