224 THE TRANSFORMATIONS OF THE ANIMAL WORLD 



the order of the Cretacean Pythonomorphs, and 

 finally the whole group of Serpents. But there is 

 hardly need to add that even a superficial exam- 

 ination of the cranial and skeletal characteristics 

 suffices to show the slight importance of these 

 analogies, and to enable each of these serpentine 

 animals to be ascribed to the zoological rank to 

 which it really belongs. 



It would be easy to multiply these examples of 

 superficial convergences by showing the resem- 

 blance, as regards the hind limb and the tail, 

 between the Iguanodon and the Kangaroos, that of 

 several Reptiles of the South African Trias (Lyco- 

 saurus and Dicynodon) to the Carnivorous Mam- 

 mals and the Walruses, etc. But it will be easily 

 seen that this is simply a question of the phe- 

 nomena of adaptation to identical functions. 



We cannot, however, be satisfied with a similar 

 explanation for the comprehension of some cases of 

 remarkable convergence furnished to us by organs 

 limited and relatively of small importance to the 

 structure as a whole. I refer to the dermic plates 

 and the teeth. It is known that a large number of 

 living or fossil Amphibians and Reptiles, belonging 

 to very different groups, have the head or the body 

 protected by bony dermic plates of very varying 

 forms and sizes. Similar cutaneous plates are found 

 in a few Mammals, such as the Tatus of South 

 America. When these dermic plates are met with 

 in an isolated state in terrestial strata, it is not 

 always easy to determine the genus, or often even 

 the group of animals of which they formed part. 

 One might hesitate to attribute an isolated plate of 



