INTRODUCTION. xi 



Living in a maritime city, and pursuing a profession which ad- 

 mits of but the occasional absence of an hour or two, my opportu- 

 nities for exploring and collecting have been very limited. I have 

 been dependent upon others, less confined than myself, for speci- 

 mens, and to them am I indebted for most of the new and rare 

 species which I have examined. I have experienced a liberality 

 and cooperation from them, without which I could have done 

 little. 



I would especially acknowledge the liberality of Col. J. G. 

 Totten, U. S. Engineers, for a choice collection of shells dredged 

 by him in the harbour of Provincetown, and for unlimited per- 

 mission to select specimens from his extremely perfect cabinet of 

 American shells. Dr. L. M. Yale, of Martha's Vineyard, has 

 supplied me abundantly with the shells and Crustacea found at that 

 island, with much information concerning them. Prof. C. B. 

 Adams has contributed the numerous new species found by him 

 in the vicinity of New Bedford. From Dr. J. B. Forsyth, of 

 Sandwich, I have received shells of that vicinity. Mr. J. P. 

 Couthouy, besides contributing numerous sjiecies, directed atten- 

 tion to the examination of the entrails of fishes, especially of the 

 haddock, as an effectual and easy mode of acquiring the deep- 

 water shells, which the fishes swallow for nourishment. To the 

 cabinets of Rev. F. W. P. Greenwood, Dr. Seth Bass, and Dr. 

 D. H. Storer, Mr. T. J. Whittemore, G. B. Emerson, Esq., 

 and Amos Binney, Esq., I have had free access, and the liberty 

 of employing choice specimens for descriptions and figures. On 

 the last-named gentleman I have been mainly dependent for books ; 

 and without the use of his extensive library of works on Natural 

 History, I could not have proceeded with any degree of assurance 

 or satisfaction. 



Every species described, and indeed almost every species men- 

 tioned, has passed under my own eye. The descriptions of spe- 

 cies previously known have been written anew ; partly, that they 

 might be more minute in particulars, and partly, with the hope of 

 using language somewhat less technical than is ordinarily employed 

 by scientific men. Technical terms cannot be wholly avoided ; 

 and wherever they are dispensed whh for the sake of intelligibihty, 

 it is at the expense of precision. 



