FLYING-DRAGONS. 167 



respects, varied greatly in size and shape among 

 the different groups. The jaws were either 

 armed with teeth lodged in sockets, and appar- 

 ently adapted for holding slippery prey, such as 

 fish ; or were toothless and ensheathed in horn, 

 or in thin leathery skin, as in birds. 



The tail was in some species exceedingly short, 

 in others of great length. 



In size these creatures varied greatly, the 

 smallest species not exceeding that of a sparrow, 

 the largest having an expanse of wing of over 

 twenty feet, these reaching the highest maximum 

 ever attained by any flying animal. 



During life the body was probably invested 

 in a covering of scales, and it is quite probable, 

 especially having regard to the extreme activity 

 of these creatures, that these scales were bril- 

 liantly coloured, as in many Eeptiles of to-day. 

 When at rest, it is supposed that they passed 

 the time clinging to the surfaces of rock-cliffs by 

 the large claws on the short digits immediately 

 in front of the wing-finger. 



Concerning the origin of this group of extra- 

 ordinary creatures we know nothing. They 

 appear suddenly, fully developed, in the Lower 

 Lias, e.g. Dimorphodon, and vanished from the 

 face of the earth quite as suddenly in the Cre- 

 taceous period. It is instructive to notice that 

 the earliest forms to appear were small, the 

 huge bulk ultimately attained by certain species 

 in the Cretaceous epoch being reached by slow 

 stages. 



Since the wing is the most important feature 

 in these creatures we may profitably revert to 



