108 CLASSIFICATION OF AMPHIBIANS. 



formed for walking ; the feet of the chamelionSj how- 

 ever^ are of a very peculiar construction^ and show us 

 such a departure from the ordinary structure seen in 

 lizards^ that we are prepared to expect a new modification 

 ofthereptHe form. This is apparent in the £'?72^rfo5awre«j 

 or orocodiles^ which^ although possessing the general 

 form of the last^ are distinguished hy being entirely 

 aquatic : hence their feet are webbed ; while^ in lieu of 

 scaleSj their body is protected by hard shields or 

 bucklerSj sometimes called plates. Other character- 

 isticSj of a less obvious, but equally important nature, 

 are possessed by these gigantic creatures, all which 

 win be subsequently noticed. Following these, and 

 with scarcely any marked interruption of the series, 

 come the Chelonides_, or tortoises ; slow-paced animals, 

 enclosed, as it were, in a hard box or shell, covered 

 externally with plates^ into which they can withdraw 

 themselves in case of need. However widely different 

 as is the structure of a crocodile and a tortoise, we 

 might here pause to admire the exquisite ease and 

 harmony with which Nature can combine some of her 

 most apparently opposite forms. In the crocodiles, the 

 tail is invariably very long, and armed with ridges of 

 plates ; while in the majority of the tortoises, it is so 

 remarkablv short as often to be hid : nevertheless, in 

 order to unite these two dissimilar groups, we find in the 

 alligator tortoise the taO. of a crocodile engrafted, as it 

 were, upon the body of a tortoise. Thus conducted, we 

 pass onward to the marine turtles, which stand at the 

 opposite extremity of this order ; and here, again, we 

 meet with a perfectly analogous change to that by 

 which these chelonian reptiles are united to the cro- 

 codiles. The feet of the tortoises, although thick and 

 clumsy, are always separated into short toes ; but in the 

 turtles, these feet are metamorphosed into fins ; — in- 

 dicative, in fact, of the last order which we shall 

 notice, namely, the Exalosaures or fish-Hzards. Here 

 we have some of the most extraordinary reptiles in the 

 whole class. They are all fossU, and, with the ex- 



