CONUS. CONE. 55 



Child. Their being composed of only one 

 valve. 



Teacher. And what are the points of dis- 

 similarity that lead you to separate this smaller 

 set from the whole group ? 



Child. The difference in their general ap- 

 pearance, and in their mouth. 



Teacher. You have now formed a smaller 

 class. Such a subdivision is called a Genus, 

 from the latin word gen us, a kind ; the plural 

 of genus is genera. The characteristic distinc- 

 tion of each genus among the univalves is foun- 

 ded on the general appearance of the shells, and 

 the form of their mouth. The specimens which 

 you have chosen belong to the genus called 

 Conus, the plural of which is Coni. You must 

 now examine the shells carefully and try and 

 discover in what respect they resemble each 

 other ; you will then be able to describe their 

 generic character, or mark those qualities pos- 

 sessed in common by them all, and which dis- 

 tinguish them from all other shells. How will 

 you set about this ? 



Child. We must compare them together, 

 and put down those qualities which they all 

 possess. 



Teacher. First consider their general ap- 

 pearance. 



Child. Their shape is very similar ; it re- 

 sembles a cone. 



Teacher. Yes, and it is conical, and from 

 hence they have received their scientific name, 

 Conus, and their common English name, Cone. 



