66 LESSON XII. 



inequalities of the surface. Here is a shell called 

 Conus marmoreus : I wish you to examine it, and 

 draw out its specific character ; it is considered 

 as the type or representative of the Conus, from 

 its having the characteristics of the genus strongly 

 marked. Now, tell me what you have to do. 



Child. We must try and describe this shell. 



Teacher. And you must recollect that you 

 have to point out the specific distinctions only, 

 you must now omit the generic marks, as you 

 have already determined them, and they are 

 implied in the name Conus. First, what is the 

 size of this Cone ? * 



Child. It is rather more than two inches long. 



Teacher. Yes, in length it generally varies 

 from two to three inches. What is the colour of 

 the shell, and that of its markings ? 



Child. The ground is a dark chesnut brown, 

 approaching to black, and the markings are white. 



Teacher. What form do the spots most 

 nearly resemble ? 



Child. They are nearly triangular. 



Teacher. You may call them white sub tri- 

 angular spots ; sub means under, and when pre- 

 fixed to an adjective implies that the quality at- 



* The children should have the length of an inch given 

 to them, and by degrees they will learn to determine the 

 dimensions of the specimens without measuring them. They 

 should also be practised in deciding colours and their various 

 shades, by referring at first to some standard. Werner's 

 Nomenclature of colours is a useful work for this purpose. 



