ADVERTISEMEXT 



THE FOURTH EDITION. 



An this Edition the new species recently discovered have 

 been added; and a considerable alteration has been made 

 in the arrangement of the species of each genus, with a 

 \-iew to aiFord greater facility to the student's acquiring a 

 knowledge of their distinctive characters. 



It would have been beyond the scope of an elementary 

 v^-ork of this nature to have described every species ; but we 

 have endeavoured, by forming numerous divisions and fa- 

 milies, and affixing to each a concise description, so to 

 class together the species, that the student will have little 

 difficult}' in assigning any shell that may present itself to 

 his observation to its proper didsion and family; and 

 should the shell have obtained a name descriptive of a 

 leading character, he will have no difficulty in discovering 

 it by referring to the lists of scientific and English or tri- 

 vial names accompanying the genera. 



