66 



ANIMALS OF THE PAST 



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Stages in the Development or Flight 

 Tetrapteryx, ArchEeopteryx, Hypothetical Stage, Modern Bird. 

 After Beebe. 



the Tetrapteryx or four-winged stage. At this stage, to 

 quote from Mr. Beebe, "flight was merely gliding, the 

 fingers were too free, the arm bones too delicate, the 

 sternum small or absent, and these facts considered in 

 connection with the small, weak pelvis, make it impos- 

 sible to picture the creature as flying skilfully about. 



