EXTINCT ANIMALS 



preserved in the Lithographic slates (see Fig. 

 31, p. 47), and each consisted of a membrane 

 spread from one enormously big elongated 

 finger to the side of the body and little hind 

 legs. 



Fig. 170 gives some idea of the form and 

 appearance of the wings when expanded. Such 

 a wing is more like that of a bat than that of a 

 bird, since it is a membranous skin and not a 

 series of feathers. The bat's mng is a mem- 

 brane supported by three of the fingers as Avell 

 as the side of the body and hind leg. 



In Fig. 171 the fossil wing of a Pterodactyle, 

 that of a recent bird with the bones and the 

 great quill-feathers only in place (the smaller 

 feathers having been plucked off), and the mng 

 of a bat are photographed and placed together 

 for comparison. There are two other kinds of 

 flying animals, namely, the flying flshes (which 

 do not fly far), and the six-legged insects or 

 flies, bees and beetles. They have all inde- 

 pendently acquired the habit of flying and have 

 had certain parts of their bodies changed into 

 wings. The process of change must have been 

 gradual and have taken an enormous lapse of 

 time to bring it about in each kind. There are 



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