50 LESSON VIII. 



casioned by whorls. You can, perhaps, recol- 

 lect an instance in architecture, in which the 

 name is so applied. 



Child. Yes, the spire of a church. 



Teacher. When the spire of a shell is formed 

 by whorls, which is generally the case, it is said 

 to be spirally convoluted ; the latter term is de- 

 rived from the Latin words, con together, and 

 volutus rolled. Now examine the spire still 

 more attentively, and you will find some other 

 parts. 



Child. There is a line formed where the 

 whorls meet ; has this line any particular name 1 



Teacher. Yes, it is called the suttvre, from the 

 Latin sutura, a seam or joining ; do you perceive 

 any difference in the sutures ? 



Child. Yes, in some shells itis quite a ridge, 

 and in others it is more like a channel. 



Teacher. When it is raised like a ridge or 

 keel, it is called carinate, from the Latin carina, 

 a keel ; when it is a sunken line, it is said to be 

 channelled. Now look at your shells again. 



Child. Are any parts of the shells considered 

 to be the top and bottom. 



Teacher. Yes, the point of the spire is the 

 top. You recollect what the top and bottom of a 

 cone are called, and you may apply these terms 

 to shells. 



Child. The point of the spire is then the 

 apex, and the part immediately opposite, the 

 base. 



Teacher. You are right. 



Child. I think that when you described to us 



