PREFACE. 



Tins PublictUiou is undertakcMi by nie after scvera years 

 of careful study. My researclies among the jrollusks have 

 not, however, been conlined to any prescribed area. Were i( 

 so, I should not venture to describe even the Si^ecies of one 

 county. My collections have been made in every part of the 

 world ; and I have thus accumulated abundant material for 

 study and comparison. I regret that my investigations of 

 the soft 2>arUH have not been more extensive and thorough, as 

 I regard a complete knowledge of these essential to the proper 

 understanding and delinite settlement of species. This is, 

 however, a branch of the study in Avhich all our naturalists 

 are deficient. The species of the United States have occupied 

 my attention more than those of any other country, from the 

 fact that specimens arc abundant and easily obtained. And, 

 also, the variations of many American species are very great, 

 thus challenging the wonder and attention of the naturalist at 

 every step. Not only new forms, but the dift'erences occuriug 

 in established species, are inducements to research. The field 

 is by no means exhausted or fully explored. If T shall succee«l 

 in turning attention in this direction, or in adding anything 

 of interest to the facts already known, my labors will be 

 amply compensated. In this County there are a large num- 

 ber interested in the study of Natural History, and this paper 

 is intended to aid them in prosecuting their investigations in 

 f he department of the Mollusca. 



A knowledge of the science of Conchology(or of any science,) 

 cannot be acquired in a day; neither in years can one become 

 perfect. We must climb step by step. I do not profess to 

 be more than a beginner myself. Professor Louis Agassiz 

 said that all he had accomplished might be summed up in one 

 siiigle sentence. Therefore, I would say to my young nat- 

 uralist friends — be not discouraged by the seeming vastness 



