32 INTRODUCTION. 



beautiful, even with this cuticle on them, they are much 

 more so when it is removed ; but I would by no means ad- 

 vise the collector of shells to remove it, unless he may have 

 several duplicates of the same species ; and then he may do 

 it by way of variety. It is always preferable, however, to 

 keep shells in their natural state. 



A shell with epidermis is represented in Plate III. fig. 2, 

 X; and the effect of the epidermis removed at /. 



All other circumstances relative to the forms and mark- 

 ings of shells, will be described at the end of the work, in 

 the Glossary of Terms used in the Science. 



We may now proceed to give an account of the Linnaean 

 genera composing the three orders of si tils. 



