SHELLS. 47 



5. Describe the different methods by which 

 they render themselves stationary. 



6. Describe the organs by which they feed 

 themselves. 



7. Name the two classes into which the 

 mollusca are divided. 



8. Describe how the animals of these two 

 classes differ from each other. 



9. Of what substances are the shells formed? 



10. How are they coloured ? and what is, sup- 

 posed to occasion the regularity in the markings ? 



11. How is the form of the shell regulated? 



12. What is there remarkable in the formation 

 of shells? 



13. How are shells fitted for the different 

 situations they ccupy ? 



14. How is the compensatory providence of 

 God manifested in the history of the mollusca ? 



15. Into how many classes are shells divided? 



16. How are the shells of each class distin- 

 guished ? 



17. Give the derivation of the names of the 

 classes. 



LESSON VIIL 

 PARTS OF AN UNIVALVE SHELL. 



Teacher. To what class do all these shells 

 belong ?* 



* A variety of univalve shells should be placed before the party 



