96 STUDIES OF ANIMAL LIFE. 



2. What is done with these parts in times of danger ? 



3. What effect does such a shell have upon the move- 



ments of the turtle ? 



4. Parts of the Shell.' 



a. The carapace, the dorsal portion. 



b. The plastron, the ventral portion. 



c. The bridge, the. lateral connecting portions. 



5. The Dermal Plates. 



The dermal plates are the "scales " which form the 

 outer covering of the shell. 



a. What color markings are there on these plates ? 



b. What is the arrangement of the plates on the 



carapace ? On the plastron ? 

 0. Is this arrangement of the plates the same for all 

 turtles ? 



d. What variations do you find in the texture of 



the dermal plates of turtles ? 



6. Make two drawings of the shell, one of the carapace 



and one of the plastron. 



7. The Bony Shell. 



The bony shell is the shell which lies beneath the 

 dermal plates and may be seen by removing 

 these plates. (Dem.) 



a. Is this shell thicker or thinner than the dermal 



shell ? 



b. Is the arrangement of the bony plates the same 



as that of the dermal plates ? 



c. Observe the fusion of the ribs and backbone with 



the bony shell. 

 Is it correct to include a study of the bony shell 

 in a study of exoskeletons ? 



8. What exoskeletal parts besides the shell has the 



turtle ? 



