THE VERTEBRATE ANIMALS 293 



REFERENCE BOOKS 

 ELEMENTARY 



Davison, Practical Zoology, pages 199-211. American Hook Company. 

 Herrick, Textbook in (/cm nil Znnlniji/, Chap. XX. American Hook ('ompany. 

 Hodge, Nature Study and Life, Cl laps. XVI, X\"II. ( linn ami ( 'ompam -. 

 Jordan, Kellogg, and Heath. Animal Stmlifis. I). AppletOD an<l Company. 

 Nature Study Leaflets, Cornell Nature Study, Hulk-tins XVI, XVII. 



ADVANCED 



Ditmars, The Batrachians of New York. Guide Leaflet 19, American Museum 



of National History. 



Dickinson, The Frog Book. Doubleday, Page, and Company. 

 Dickinson, Salamanders. Doubleday, Page, and Company. 

 Holmes, The Biology of the Frog. The Macmillan Company. 

 Morgan, '/'// Development of the Frog's Egg. The Macmillan Company. 

 Parker and Haswell, Textbook of Zoology. The Macmillan Company. 



Reptiles 



Turtles and Tortoises, Adaptations for Life. The turtles and 

 tortoises, the latter land animals, form a large and interesting 

 group. The body is flattened, and is covered on the dorsal and 

 ventral sides by a bony framework. This 

 covering is composed of plates cemented to 

 the true bone underneath, the whole form- 

 ing one horny cover. This covering, an 

 adaptation for protection, is more perfect 

 in the box tortoise, where a hinge on the 

 ventral side allows the animal to retreat 

 within the shell, the head and legs being 

 completely covered. Wl . atcrn painted turtle . 



Adaptations for Food Getting. The long 



neck and powerful horny jaws are factors in the food procuring. 

 Turtles have no teeth. Prey is seized and held by the jaws, the 

 claws of the front legs being used to tear the food. 



Turtles are very strong for their size. The stout legs carry the 

 animal slowly on land, and in the water, being slightly webbed, 

 they are of service in swimming. In some water turtles the front 

 limbs are modified into flippers for swimming. The strong claws 

 are used for digging, especially at egg-laying season, for some 

 turtles dig holes in sandy beaches in which the eggs are deposited. 



