46 LESSON IX. 



Teacher. This very pointed spire is said to 

 be subulate,* from the latin subul a, a pointed 

 tool. The term spire is now applied to any form 

 which resembles that produced by whorls, rising 

 one out of the other, and decreasing in diameter, 

 though it be not formed by whorls. You can 

 perhaps, recollect an instance in architecture, in 

 which the name is so applied. 



Child. 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 

 volut us, 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 ? 



Teacher. Yes, it is called the suture, from 

 the Latin suture, a seam or joining ; do you 

 perceive any difference in the sutures of shells ? 



Child. Yes, in some shells it is 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 carin a, 

 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 shell 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 

 * See Buccinum Subulatum. Plate III. Fig 4. 



