SHELLS. 43 



6. Describe the organs by which they feed 

 themselves. 



7. Name the two classes into which the mol- 

 lusks 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 ? 



1 1 . How is the form of the shell regulated ? 



12. What is there remarkable in the formation 

 of shells ? 



13. Give some examples of shells peculiarly 

 fitted for the different situations they occupy ? 



14. Mention some instances of the compensa- 

 tory providence of God manifested in the history 

 of the mollusks ? 



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 IX. 



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. 



