ADVERTISEMENT. 



In this estimate, which the Author at first conceivexl 

 ^vould be completely adequate to every purpose of his 

 design, he afterwards perceived himself in some degree 

 mistaken. During the course of publication he has in 

 various instanced been kindly favoured with British Shells 

 not before described : neither are the acquisitions which 

 he has himself discovered in several remote parts of the 

 country altogether unworthy of attention. ]\Iany of the 

 species thus obtained were deemed too interesting to be 

 om.itted in a work of this nature, and it was therefore thouglit 

 advisable to exclude those, which, from their extreme 

 minuteness, are usually denominated Microscopic Shells, 

 in order to admit the most important of them. The 

 omission of the more diminutive species, for the sake of 

 inserting Shells of conspicuous figure, that had not been 

 before described as English, the Author trusts will rather 

 be considered as an advantage, than detriment to this 

 Avork, Nothing of material consequence, either in the 

 collection of the Author, or the cabinets of his friends, 

 to which he has access, has been neglected in this selection ; 

 and he could not feel himself completely justified in 

 extending the work beyond the limits originally prescribed 

 for no other purpose than to introduce the Microscopic 

 Shells. 



