CHAPTEK YII 



EAKLY BIEDS AND MAMMALS 



The history of early birds in this country 

 is short, and contained wholly in rocks of the 

 Cretaceous period. Before that time there is 

 so far no trace of bone* or imprint of feather 

 to hint at their existence. And yet birds there 

 must have been, for a great proportion of the 

 birds from the chalk cliffs of western Kansas 

 are flightless species, and had been devoid of 

 the power of flight for so long a period that 

 only vestiges of ^vings were left. It may be 

 asked what reason there is to suppose that the 

 ancestors of these birds did fly, and the answer 

 to this is that the character of the wing (in 

 Baptornis at least) is such as to show that it 

 must have been derived from a limb that once 

 served a good purpose. Even the flightless 



* Laopteryx, described by Professor Marsh, from the Jurassic 

 of Colorado, is very probably a pterodactyl. 



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