given original descriptions of new species, whether the specific names 

 be Carpenter's or my own. the types are understood to be the 

 ment described by me, in the collection of the Academy; wherever 

 and whatever the original < mens may be. A case 



in j...int is /> // ocrtor, p. 60, and /. conspicuus, p. 63. It is 



liy this expedient that confusion can be avoided in cases of real 

 or fancied wrong identification, on my part, of Carpenter's .V . 

 species. 



Many new species not illustrated in the body of the work are 

 figured from the typos in the Appendix. The Appendix should 

 always be consulted when a species is not found elsewhere, as forms 

 .M known generic position have been included therein. 



e grateful task remains of acknowledging assistance from 

 scientific friends and institutions. Through the intervention of DR. 

 \\"M. H. DM. i.. Honorary Curator of the Department of Mollusks, 

 U. S. National Museum, the writer has received from S. P. LAV-- 

 . Secretary of the Smithsonian Institution, the drawings and 

 .i/v prepared by the lamented PHILIP P. CARPENTER upon this 

 group, a work of priceless value, embodying the results of many 

 years study of the subject. Throughout the text of this volume will be 

 foun fcfl from this MS.; such quotations in every case being 



idly credited. For the loan of a large number of type spec- 

 iim -us from the Smithsonian collections, the writer is indebted to the 



nued kimlnesi of DR. DALL. To J. F. WHITEAVES of the 



ula Geological Survey, PROF. WHITFIELD of the American 



urn of Natural Hi>tory, New York City, PROFESSOR F. W. 



of Christchurch, New Zealand, and many other con- 



chologists, the thanks of the author are due for specimens presented 



or loaned. 



H. A. P. 



