PREFACE. 
In preparing the present work, it was my purpose to furnish to Concho- 
logical students and to sea-shore collectors succinct and plain descriptions, 
illustrated by characteristic figures of the American Marine Mollusks in- 
habiting our coast from Maine to Florida. I could not 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 reader a reasonably good idea of their appearance, mode of 
life, ete., 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 
