WINGS COMPARED 



Fig. 171. — Photographs of three wings for comparison of their 

 strvicture. A. That of a Pterodactyle, membrane sup- 

 ported by one long finger. B. That of a Bird, feathers 

 set on the fore-arm {cubitus) and hand. C. That of a Bat, 

 membrane supported by three elongated fingers. 



233 



