CONUS CONE. 63 



which preserves the fine polish of the surface. 

 They are all natives of the ocean, and belong to 

 the seas'of hot climates, where they live at a depth 

 of about ten or twelve fathoms, They are never 

 found 011 our coasts. Their name is derived from 

 the Greek, KWQS (conos) a cone. Now attend and 

 answer the questions I shall put to you upon what 

 I have detailed. What kind of animal inhabits 

 the cone? 



Child. A mollusk with a head, it has a pair 

 of tentacula bearing eyes ; and its mouth is a 

 long proboscis ; it breathes by means of gills. 



Teacher. There is one part of the animal 

 which you have not noticed. 



Child. It has an operculum attached to its 

 foot, with which it closes the aperture of its shell. 



Teacher. What is remarkable in the habits of 

 this mollusk ? 



Child. It is supposed to absorb the matter of 

 which the interior convolutions of its shell are 

 composed. 



Teacher. What then is the appearance of 

 the shell when cut in halves ? 



Child. The interior parts of the whorls are 

 thin, whilst the outer part of the shell is thick 

 and strong. 



Teacher. What advantage is the animal sup- 

 posed to derive from the external convolution 

 being so much thicker than those within the 

 shell ? 



Child. The thinness of the interior diminishes 



