vi PREFACE. 
collectors will be supplied with many of these Arctic species, Of those 
known to seience a considerable portion extend southwards to Cape Cod, and 
are consequently herein described. Our southern limit, on the other hand, 
will include a considerable number of tropical forms which, dispersed and 
protected by the warmth of the Gulf Stream, have spread to various por- 
tions of our southern coast. I could not extend my limits southward to the 
southern coast of Florida or that of the Gulf of Mexico without including 
the great West Indian province, which would have enlarged my work to five 
or six times its present bulk. This portion of our marine molluscous fauna, 
like that of our Pacific coast, may be advantageously presented in separate 
treatises.- 
It gives me great pleasure to acknowledge my obligations to many friends 
for their active interest in my work; Iam particularly indebted to Mr. Joun 
H. Txomson, of New Bedford, Mass., and Dr. H. C. Yarrow, of Fort 
Macon, N. C., for extensive collections from localities rich in species. I 
have dedicated my work to the memory of the three deeply lamented natu- 
ralists to whom we are principally indebted for our knowledge of American 
Marine Mollusca. ‘Two of them, Dr. Goutp and Dr. Srrmpson, were per- 
sonal friends, and from the time when they fostered my first efforts in natural 
science almost to the period of their deaths I never applied to them in vain 
for assistance and advice in my Conchological studies. 
The generic and specific descriptions used in this book are principally 
copied from ‘‘ Woodward’s Manual of the Mollusca,” Adams’ “ Genera of 
Recent Mollusca,” De Kay’s “ Mollusca of New York,” Gould’s “ Inverte- 
brata of Massachusetts,” and from the original diagnoses of Say, Adams, 
Mighels, Stimpson, and others. I think that it is unnecessary to make any 
apology for using so extensively the language of other writers in preference 
to preparing original descriptions—the latter course I have adopted when- 
ever I believed that I could improve or correct the original description. I 
trust that this general acknowledgment will save me from the reproach of 
egotism in avoiding the use of cumbersome and unsightly quotation marks. 
Upon the completion of each of my former volumes I have promised 
myself that it should be my last book ; that pledge I am.again impelled to 
violate. Those alone, who labor in a similar field, can understand how im- 
peratively science requires her votaries to publish her truths for the instruc- 
tion of the world. 
GEO. W. TRYON, Jr. 
January 1, 1873. 
