

INTRODUCTION. 



> Y the pcrfuafions of our fcientific friends to give 

 delineations of many of the fliells defcribed in Tejlacea 

 Britannica, which at the time were omitted from tlie magni- 

 tude of the undeitaking at a diflance from the arts, we have 

 been induced at our Icifure to fele(5l fuch of them whole 

 figures may lerve to ekicidate, and have had them engraved, 

 togetlier with feveral new and intercfling fpecies, for the 

 ufe of tlie public. The additional plates will therefore con- 

 fift of about ninety dillincl fpecies, many of which ai'e only 

 to be met with in the cabinet of the author, or in that of one 

 or two of his fcientific friends ; others, though common, arc 

 figured for tlic purpofe of defining the adiual diftincSlion 

 betv/ecn funilar (liells which have been, and Itill in part con- 

 tinue to be confounded. And we have been inclined to 

 prefer a large proportion of land and frefli-water fpecies, 

 becaufe they are within the reach of many who live remote 

 from the fea coafl, and have in many inftances been lo com- 

 pleatly jumbled together, that this divifion more immediately 

 within the reach of all, requires the more immediate atten- 

 tion. We have not however neglected the marine divifion, 

 where figures could dilplay that difiinction which might 

 elucidate the fubjetfl : it mufl: however be admitted that there 

 are in this, as in every other branch of phyfiology, fome 

 fpecies whofe affinity is ib extremely great, that were it 

 not for fome invariable minute diftin^lions undefinable by 



A 2 the 



