56 LESSON VHI. 



would be next to the right hand of a person 

 looking at it, the front of the shell being placed 

 opposite to him. 



The left side is that part of the shell which 

 would be next to the left hand of the person 

 looking at it, the front being opposite to him. 



Teacher. Give me the derivation and appli- 

 cation of the word spire. 



Mention the different kinds of spires, with the 

 derivation of the terms which you use. 



Whence is the term suture derived? 



How do the sutures vary ? 



What different projections occur on the sur 

 faces of shells'? 



From what is the term varices derived? 



How are the cavities of the shells often closed ? 



Tell me the derivation of the word operculum. 



What different kinds of opercula are there? 



What are the shells called which have a beak? 



What is the mouth said tabe when it has no 

 beak?* 



* These model lessons have been drawn out. with so much 

 minuteness in order to exhibit two priciples, very important to be 

 applied in this kind of instruction. 1st. That the object itself should 

 be presented to the class ; that their powers of observation should 

 be stimulated and directed by appropriate questions ; and thus a 

 considerable portion of their knowledge should be acquired by them- 

 selves, instead of all being simply communicated by. the teacher. 

 2d That whatever supplementary information is given should be 

 reproduced by the children before the conclusion of the Jesson. 



