OP CREATION. 205 



tiles with these appendages, other mechanical con- 

 trivances are resorted to by which the power of flight 

 is obtained, and the common integument preserved 

 in the bat and Pterodactyl. 



In bats, which are flying quadrupeds, this modifi- 

 cation consists in the extraordinary development of 

 all the fingers, upon which skin is stretched like the 

 silk on the rods of an umbrella ; and this skin ex- 

 tends not merely between th.e elongated fingers, but 

 also from the last finger to the legs and feet, and so 

 to the tail. The thumb is partially left free, and 

 serves as a hook by which the animal suspends itself; 

 but the toes are exposed, and are moderately long. 



There is no really flying reptile now existing, but 

 in one species (the Draco volans), which is able to 

 support itself for a short time in the air, there is a 

 very imperfect flying apparatus, which chiefly acts as 

 a parachute, supporting the animal in its long leaps. 

 This consists of an expansion of the skin over a series 

 of false ribs extending horizontally from the backbone. 

 In the Pterodactyl, however, which is evidently 

 and expressly contrived for flight, a very singular 

 contrivance is introduced, and it is one which seems 

 to have ensured to the animal the power of walking 

 and swimming, as well as flying (see fig. 78). 



In order to effect this, the bones of the fore ex- 

 tremity, so far as regards the shoulder and arm- 

 bones, the wrist and the hand, scarcely differ from 

 the ordinary proportions of those bones in lizards, and 

 correspond with the dimensions of the hinder extre- 

 mity, so that up to this point there is no peculiar 

 adaptation for flying. On examining the bones of 

 the fingers, however, we find that the number of 



