X PREFACE. 



himself preferred, and which is prefixed to the work by 

 which he is best known as a conchologist. 



A parting word to the critics ! When a mere youth, 

 I was encouraged by my lamented friend, Mr. DiUwyn, 

 to commit to print what little I then knew of the subject 

 comprised in the present volume ; and my first essay, 

 entitled " A Synopsis of the Testaceous Pneumono- 

 branchous Mollusca of Great Britain,^^ was honoured 

 by the Linnean Society by publication in their Trans- 

 actions. Now, in mature years, I have become still 

 more bold, and venture to appeal to the public. But, 

 although I cannot hope to be exempt from the fate of all 

 authors — -criticism (and indeed, for the sake of science 

 and the elucidation of truth, I would rather in\dte it, 

 instead of considering it a calamity) , I cannot send forth 

 this little work without a mixtm-e of the same feeling 

 of hope and doubt, which made the ancient poet thus 

 apostrophize his book : — 



" Faucis ostendi gemis, et eomniuuia laudas, 

 Non ita natritus. Fuge, quo descendere gestis : 

 Non erit emisso reditus tibi." 



25 Devonshire Place, London, 

 24 May, 18G2. 



