The labels will be printed on white card-board, and will be 

 of the above appearance and size, so as to fit readily within the 

 ordinary three-inch- wide shell trays. The number in the lower 

 centre serves as a reference to the Catalogue, so that the biblio- 

 graphy, etc., can be examined instantly. The Catalogue, it is 

 believed, will answer admirably as a check list of public or 

 private collections, as well as for making exchanges, by simply 

 attaching a mark to each species possessed or wanted, or, for 

 the latter purpose, by quoting numbers from it. To the stu- 

 dent it will serve a higher purpose, in saving the vast amount 

 of valuable time heretofore expended in searching for descrip- 

 tions, by indicating at once, not only where they are to be 

 found, but also the entire number of species described in each 

 genus, thus facilitating and encouraging the description of new 

 species, and preventing the inadvertent re-description of species 

 already characterized. 



It is proposed to meet the expense of this publication by the 

 sale of Catalogues and Labels, and it is hoped that both will be 

 extensively adopted by col]ectors and museums, so as to make 

 throughout the world one principal standard of nomenclature 

 and numbering. 



The entire Catalogue will be completed within about live 

 years. 



TERMS. 



Subscriptions will be received at the following rates for each 

 16-page for?n, payable on delivery: 



To one address. 

 1 copy. 2 copies. 3 copies. 5 copies. 



'To subscribers to the whole 



Catalogue, . . . .25, .20, .18, .15 



To subscribers to any por- 

 tion, such as Land Shells, 

 Fresh-water Shells, He- 

 lix, Cyprasa, or any family 

 or genus, . . . .32, .27, .22, .17 



*#* Special and very liberal arrangements will be made 

 with gentlemen who may require a large number of copies for 

 their exchanges, etc. 



The following estimate is probably approximately correct : 

 Entire Catalogue, 2500 pp., $40. Land Shells, 1000 pp., $20. 



Fresh-water Univalves, 250 pp., $5. Fresh-water Bivalves, 



150 pp., $3. Marine Shells, 1100 pp., $22. 



