PREFACE. 



In preparing the present work, it was my purpose to furnisli to Coucbo- 

 logical students and to sea-shore collectors succinct and plain descriptions, 

 illustrated by characteristic figures of the American Marine Mollnsks in- 

 habiting our coast from Maine to Florida. I could uot undertake, within the 

 limits of a single volume, to give a complete portraiture of each species, or 

 to present its entire bibliography, and I have therefore cultivated brevity — 

 I hope in no case at the expense of lucidity. 



Following the plan adopted in my previous memoirs on American Con- 

 chology I have prepared copious analytical tables of families, genera, and 

 species, presenting their prominent distinctive characters at a glance, and 

 thus greatly facilitating their correct determination. In my classification I 

 have not always followed the most approved modern systematists, simply 

 because it appeared to me to be very unnecessary in a work of such partial 

 character as the present one to introduce a host of systematic divisions, where 

 an older, more simple, and more generally comprehensible method would sub- 

 serve my purpose. 



Space could not be found for full notes of the habits of all of our species 

 heretofore observed, but I think that I have described a sufficient number of 

 them to give the I'eader a reasonably good idea of their appearance, mode of 

 life, etc., and to incite collectors to observe and to study the living specimens. 

 The limits of bathymetrical as well as of geographical distribution of the 

 species have been carefully stated, and collectors may expect their occurrence 

 in suitable situations at all intermediate localities and depths. 



With regard to the geographical limits which I have assigned to my work, 

 I would explain that, northward of the Canadian waters, the coast has not 

 been sufficiently explored to lead to the conjecture that we have been made 

 acquainted with the moiety of its species ; moreover it is very unlikely that 



