BIRDS 



187 



to the absence of a keel on the broad sternum. It will be 

 remembered that the keel in an ordinary bird (p. 145) serves 

 for the attachment of the large muscles of flight. There is no 

 " merry-thought ", while the scapula and coracoid are in the same 

 line with one another instead of being at an angle. The overlap- 



Fig. 127. King Penguin (Aptenodytes] 



ping uncinate processes, which in a flying bird help to strengthen 

 the chest, are here absent or few in number. 



The strong legs are well adapted for running, and in nearly 

 all cases there is a reduction in the number of toes. 



The structure of these birds is best explained on the assump- 

 tion that they are descended from carinate birds in which the 

 power of flight has been lost, and their nearest relatives are 

 probably the Tinamous. 



The Ratitae which are now living may be divided into African 

 Ostriches American Ostriches, Cassowaries and Emeus, and 

 Kiwis. 



