PREFACE. 



The aim of the present book was to describe and notice 

 a large number of shells in a limited number of pages. It 

 was designed, originally, as an abridged translation of the 

 excellent edition of Lamarck's ' Animaux sans Vertebres' 

 by Deshayes, enlarged by the addition of such species as 

 appeared to the writer to be most decidedly distinct from 

 any enumerated in those volumes. This selection proved 

 embarrassing; since many of the Lamarckian diagnoses, 

 being far too brief for the purpose of definition, suited 

 fairly enough, from their very succinctness, the characters 

 of several subsequently named shells, which otherwise the 

 author would have gladly introduced. Up to the genus 

 Nucula the plan of the work has been uniform, the species 

 of the 'Animaux' following each other in numerical suc- 

 cession ; beyond that point, the author has allowed himself 

 a less fettered exercise of his more matured judgment; 

 nevertheless, no Lamarckian species has been wilfully 

 omitted. 



In the Naiades, the skeleton outline given by Lea in the 

 second edition of his ' Synopsis ' has been accepted as a 

 standard authority ; because such contradictory opinions, 



a 



