THE Fourth Volume of the Manual oi' Conchology contains 

 monographs of four important families, embracing genera of 

 which many representatives are included in the cabinet of every 

 collector of marine shells. It is hoped that it will be found 

 useful in facilitating the identification of specimens, as well as 

 in correcting the hitherto veiy confused synonymy. 



The kind offices of many correspondents in furnishing speci- 

 mens (particularly nnfigured types), drawings and information 

 concerning the species, are again gratefully acknowledged ; and 

 I am equally indebted to others for their endeavors to promote 

 the sale of the Manual. I shall endeavor to deserve and recom- 

 pense this active interest in behalf of the work by making it 

 as thorough as circumstances will permit. 



G. W. T., Ju. 



January, 1882. 



