SHELLS. 41 



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 word WM (conche) a shell, 

 and Xoyoq (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 we ought 

 to study besides the shell ? 



Child. The mollusca. 



Teacher. Yes. But as we should not be 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 large 

 number which I will arrange in three divisions, 

 and you must examine each, and observe in what 

 respect the shells I have classed together resemble 

 each other. 



Child. In this set the shells are formed of 

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

 seem to have several pieces. 



Teacher. These distinct pieces are called 

 valves. Where have you ever heard of a valve ? 



Child. A pump has a valve, and steam-en- 

 gines have valves. 



