SHELLS. 45 



When we have studied these characteristics, the 

 name will recall to our minds the idea of the set 

 of things signified by it. 



Child. A name then becomes very useful. 



Teacher. How does it become so useful 1 



Child. By recalling to the mind the things 

 which it signifies. 



Teacher. What is the class of objects which 

 you are about to study? 



Child. Shells. 



Teacher. In learning the names of shells, 

 you will learn also what the names imply. The 

 science which treats of shells is called Concho- 

 logy, from the Greek words KOVXV (conch) a shell, 

 and Xoyo? (logos) a discourse. From whence 

 does the shell derive its shape and colour? 



Child. From the animal that inhabits it. 



Teacher. What then do you think that we 

 ought to study as well as the shell ? 



Child. The mollusca. 



Teacher. Yes. But as we are not able to 

 procure many of these animals, we cannot pursue 

 that branch of the science ; and we will therefore 

 follow the classification of Linnaeus, which is 

 founded on the shells. He first divides shells 

 into three great classes. Here are a number of 

 shells. I will arrange them in three divisions, 

 and you must examine each set, and observe in 

 what respect the shells they contain resemble 

 each other. 



Child. The shells in one set are formed of 

 one piece, in the other of two pieces, and these 

 seem to have several pieces. 



