INTRODUCTION. 9 



naeus or others, with a reference to the author in whose 

 work it is figured or described. 



The genera\>f fossil species, and naked molluscse, are 

 mentioned in the respective places assigned to them, 

 as they assist in explaining geological facts, and are 

 most important in connecting the evidence upon which 

 La Marck has founded his system. The reasons that 

 have prompted him to depart from the classification of 

 previous authors on Conchology, are invariably stated, 

 and such additional observations and illustrative re- 

 marks added or interspersed, as the writer's experience 

 has enabled him to offer, which it is humbly presumed 

 may tend to elucidate this interesting subject in an easy 

 and concise manner. 



A Synoptic Table is also added, exhibiting the ar- 

 rangement made by La Marck, of the molluscous ani- 

 mals with and without testaceous coverings, including 

 also the fossil genera. 



No pretensions to originality or merit are made, 

 beyond that of endeavouring to assist or promote, by 

 every possible means, a pursuit that must tend to ele. 



