EXTINCT ANIMALS 



some animals, such as the flying squirrels and 

 flying lizards (Draco volans) of to-day, which 

 do not really fly, since they have no wings to 

 beat the air with, but can spread out a great 

 flat surface on each side of the body which 

 enables them to sail through the air for some 

 distance without falling when they jump from 

 the branch of a tree. This, however, is a long 

 way from the point reached by animals which 

 have wings and can strike the air as a fish 

 strikes the water with its fins. Probably the 

 wings of birds and of insects were both derived 

 from fin-like organs which were used to swim 

 with — ^before they were used in the air. But 

 the origin of the wing of the Pterodactyles, and 

 independently that of the wing of the bats, does 

 not seem to have been of this nature, and is one 

 of the many very puzzling matters which 

 further discoveries may one day enable us to 

 understand. 



In Fig. 172 two other kinds of Pterodactyle 

 are shown. Some Pterodactyles had no teeth, 

 but long beak-like jaws (Fig. 169). Others had 

 numerous sharp-pointed teeth and were beasts 

 of prey. 



It seems natural to pass from the winged 

 234 



