528 GENERAL CHARACTERS OF REPTILES. 



in Birds. The members do not in general present anything very 

 remarkable. Sometimes they are abruptly terminated at the 

 end, and can only serve to push the animal forward, as in Land 

 Tortoises for example ; sometimes they are terminated by slender 

 fingers, and furnished with claws, which allow the animal to 

 hook itself on by inequalities of the surface, and to climb with 

 facility ; the feet of the Lizard are formed in this way. In other 

 instances there is at the extremity of the fingers a particular 

 arrangement, which is singularly favourable to this kind of move- 

 ment ; thus, among the Hyla, or Tree-Froys (Fig. 343), we see 

 at the extremity of each of these organs a kind of rounded and 

 adhesive cushion, which allows the animal to fasten itself against 

 the substances upon which it climbs, even when their surfaces 

 are very smooth ; and among the Geckos (Fig. 331) the fingers 

 are very much expanded towards the end, and furnished under- 

 neath with little folds of skin, which appear to perform the 

 function of suckers, and which permit these hideous Reptiles to 

 ascend along the smoothest walls, and even to walk in an inverted 

 position upon ceilings. There are also some Reptiles whose 

 fingers are opposible, almost as in the hand of Man ; in fact, 

 among Chameleons (Fig. 330) they are united in two sets, which 

 spread out and approach each other, like the arms of a pair of 

 pincers, and which enable these animals to take a firm hold of 

 the branches on which they rest ; Chameleons have also a pre- 

 hensile tail, which makes them essentially climbing animals. 

 Finally, in other Reptiles adapted to a life more or less aquatic, 

 the fingers are sometimes webbed, as is seen in the posterior feet 

 of the Frog ; or are even transformed to a kind of flattened 

 paddle, unfit for walking, but very favourable for swimming. 

 The Turtles (Fig. 328) are the only Reptiles, which at the 

 present time possess this last form of structure ; but at more 

 remote periods of the geological history of the globe, our seas 

 were peopled with large animals provided with similar paddles, 

 and presenting as to the rest of the body great resemblance to 

 Lizards and Serpents ; some of these skeletons have been dis- 

 covered in the fossil state, and they have been designated by the 

 names of Icthyosaurus (Fig. 337) and Plesiosaurus (Fig. 338). 



