VI PREFACE. 



expense ; and in the genera in which there are but few shells 

 known, and those chiefly fossil and very rare, as it could only 

 be a copy of a figure already published, it was thought that it 

 would be better to refer to other works. For instance, the genus 

 Nautihis of Linnaeus is divided now into twenty-two : only five 

 figures are given : for examples of the rest, which consist of 

 either fossil or minute species, a reference is given to Parkin- 

 son's Organic Remains, excepting two, for which M. Bourguet 

 is referred to : while in the genus Venus of Linnaeus, which is 

 divided into five by Lamarck, the figure of a shell in each is 



given. 



Those who wish to learn more of the animal inhabitants 

 will do well to consult M. Adanson's Hutoire Natm-elle du 

 Senegal, and Mr. Montagu's Testacea Britannica. M. Fa- 

 vanne also has figured several of the animals in the Zoomor- 

 phose, from which work and M. Adanson's the plates of ani- 

 mals are principally copied. 



The figures of the shells, which are drawn and engraved 

 chiefly from specimens in my own collection, are given as 

 examples of the genera used by Lamarck; at the same time 

 they serve to show the principal varieties that are arranged 



