X 
PREFACE. 
been compared with the specimens^ and corrected 
where required. There have also been added to 
these plates other figures of the same species^ and 
enlarged details of those parts of the smaller kinds 
which are calculated to facilitate the determination 
of the species ; a short description of the animals^ and 
a few notes on their habits, have also been added ; 
and this new feature in the work might have been 
greatly extended, had it not been feared to add too 
much to its bulk. Indeed, although this work has 
been called in the titlepage a new edition of Dr. 
Turton’s Manual, it may be almost considered a new 
publication, as the only portions of the former edition 
that have been retained are the descriptions of the 
species, and a few of the general observations ; inso- 
much that, on revising it in its printed form, it is a 
matter of regret to me, that it was not rather under- 
taken as an entirely new work, which would not 
have cost me nearly so much trouble as editing the 
present one. 
As an Appendix, there have been added, for the 
purpose of assisting the young student, or those who 
study the mere shells, without paying any attention 
to the animals that form them, an artificial table of 
the genera ; an outline of the history of the various 
additions that have been made, from time to time, in 
this part of our Fauna; a list of the species which 
I have reason to believe had been, from various 
causes, erroneously introduced into works of this 
