226 THE STORY OF BIRD-LIFE. 



Exactly how this was done, and what this wing 

 was like, can be seen by a reference to our 

 picture (fig. 5). 



Fig. 5. 

 A restoration of an extinct flying lizard or pterodactyle. 

 By the author. 



The bat's wing differs from the pterodactyle's 

 in that all five fingers are well developed. The 

 thumb in some species is very long and armed 

 with a powerful claw. The four fingers are 

 exceedingly long and slender, and support a 

 thin membrane much after the fashion of the 

 ribs of an umbrella. 



Now compare these two with the wing of the 

 bird. Let us begin with the skeleton. At the 

 first glance this will appear to have but one very 

 short finger — representing the thumb — and one 

 very long one, representing the index or first 

 finger. If we look at this closely in a very 

 young bird, we shall find that this long finger 

 really consists of two fingers closely joined to- 

 gether, representing the second and third digits 



