SYSTEM OF LINN.^US. 15 



CHAPTER III. 



" As you both assure me," said Mr. Elliot, 

 " that you do not fail to make yourselves familiar 

 with the nomenclature^ or terms, used in con- 

 chology, I shall proceed this morning to the ar- 

 rangement of Linnaeus. 



^' This system is established upon the outward 

 appearances, or external characters, of the cover- 

 ing bestowed by nature upon the animal, not upon 

 the form of the animal itself. 



" The three principal divisions you are already 

 acquainted with, namely, Multivalves, shells 

 composed of several parts called valves; Bivalves, 

 formed of two parts ; and Univalves, composed 

 of one part or piece only. 



" These divisions contain several ^ewerff, and 

 the genera usually include many individual shells, 

 but occasionally only one. 



" The characters of every genus are permanent, 

 and are therefore to be observed in every one of 

 the species contained in the genus. 



" Species are determined by shape, colours, or 



