52 REPTILES 



movements in water. Then, again, the nature of the dentition 

 and the form of the mouth-cavity appear adapted for a fish-diet. 

 And it is accordingly suggested that these huge reptiles cap- 

 tured fishes near the borders of lakes and rivers, which they 

 swallowed whole without mastication. The number of repre- 

 sentatives of the Chelonia which are vegetable-feeders has been 

 already referred to, but it may be mentioned that the giant land- 

 tortoises of the Galapagos, together with the land-iguana of the 

 same islands, subsist on large cactuses, which form the chief 

 vegetation of those islands. 



Lastly, the New Zealand tuatera {Sphenodon), the sole ex- 

 isting representative of the Rhynchocephalia, subsists upon ani- 

 mal food, although the nature of this seems to vary according 

 to individual taste. Some specimens, for instance, consume 

 insects and worms, and those which frequent the shore not 

 improbably eat crustaceans. This suggests that the food of the 

 extinct Triassic pavement-toothed tuatera {Hyperodapedon) may 

 also have consisted of crustaceans and perhaps of molluscs. 

 The bean-toothed reptiles (Placodontia) almost certainly sub- 

 sisted on a diet of the latter type. 



Brief reference to certain peculiar modes in which some 

 reptiles capture or kill their prey must suffice. An ingenious 

 method of capturing flies and other insects is employed by 

 chamaeleons, in which the tongue is developed into an elastic, 

 trumpet-like organ which can be shot out to a long dis- 

 tance in front of the mouth, and is furnished at its tip with a 

 glutinous secretion for securing the prey. Crocodiles and alli- 

 gators, having seized their victims in their cruel jaws, hold them 

 under water until they are drowned ; and it would seem that 

 these reptiles have developed the peculiar respiratory mechan- 

 ism by means of which they are enabled to breathe while their 

 mouths are under water for this purpose. Pythons kill their 

 victims by encircling them in their coils and gradually crushing 

 the life out of them ; and vipers and other venomous snakes 

 kill their prey by injecting poison into their tissues. In this 

 connection it is interesting to notice that the poison of different 

 groups of snakes is designed to destroy with the greatest rapidity 

 the particular kinds of animal on which they severally prey. 

 The venom of the sea-snakes, for example, acts much more 

 powerfully on fishes than on land animals, while that of cobras 



