188 ZOOLOGY. 



such species are only preserved from extinction by their 

 nocturnal habits and their protective resemblance to the 

 herbage and leaves of trees, there is a little bright red and 

 blue frog in Nicaragua which hops about in bright day- 

 light. It owes its life to its bad taste, for ducks and fowl 

 will on this account not eat it. 



Class VI. — Eeptilia (Lizards, Snakes, Turtles, and 



Crocodiles). 



General Characters of Reptiles. — While the fishes and 

 Amphibians are much alike, the reptiles, with their scales 

 and claws, come near the birds. In their skull and skeleton, 

 and in the 4-chambered heart of the crocodiles, they are also 

 bird-like. Reptiles, then, are characterized by having their 

 bodies covered with scales and their toes ending in claws, 

 with the exception of the snakes, which have no legs and 

 consequently no claws. The reptiles also, unlike the fore- 

 going vertebrates, have true nostrils like those of birds and 

 beasts, and there is in all except snakes an upper and a 

 lower movable eyelid, while the tongue is long and forked 

 and can be darted out after insects. They have also true 

 lips, and a long windpipe like that of birds. There are 

 3000 species of living reptiles known, of which 358 are 

 North American. 



Orders of Reptiles. 



1. Body long, slender, cylindrical, limb- 



less Ojihidia (Snakes). 



2. Body with a long tail; usually two 



pairs of limbs Lacertilia (Lizards). 



3. Body enclosed in a thick shell Chelonia (Turtles). 



4. Lizard-like; vertebra? hollow at each 



end Rhynchocej)halia (Sphenodon). 



5. Body thick-scaled; teeth in sockets . Crocodilia (Crocodiles). 



Order 1. Ophidia (Snakes). — Notwithstanding the fact 

 that snakes have no legs, they can creep, glide, grasp, sus- 

 pend themselves, erect themselves, leap, dart, bound, swim, 



