A D V E R T I S P: IVI E N T . 



The Smithsonian Institution, realizing the lack of 

 knowledge in refere^'^e to the land and fresh-water shells 

 of North America/ issued a circular, several years ago, 

 to its correspondents and the friends of science generally, 

 asking contributions of specimens from as many localities 

 as possible, with a view of publishing a report on the 

 subject. In the course of a few years a gratifying re- 

 sponse was made to this appeal from all parts of the con- 

 tinent, in the form of extensive collections of specimens, 

 embracing not only the several species, but those illus- 

 trating geographical distribution. 



The specimens thus obtained were placed by the Insti- 

 tution in the hands of specialists, for the preparation of 

 a series of monographs to bear the general title of "Land 

 and Fresh-water Shells of North America." This was 

 subdivided into : I, Pulmonata Geo2)Jdla^ terrestrial uni- 

 valve shells, breathing free air ; II, Pulmonata Lim- 

 nojjJilla and ThalassojjMla^ free air breathing univalves, 

 l)ut usually living in or near fresh waters (^Limnophila) 

 or the sea {Thalassophila) ; III, all the operculated land 

 and fresh- water molhisks (excepting the Strepomatidce 

 or American Melanians) and embracing the Amj^ullar- 

 iidcBy Vidvatidcc, VlviparidcR, Pissoidcey Cyclojjhoridai, 

 TruncateUidcGy JVei'itidce and HelicinidcE ; IV, the Strej)- 

 omcdidxE; V, the Corbiculadce; and YI, the Unionidce. 



Of these monographs, Parts II and III, by Mr. W. G. 

 Binncy, were published in September, 1865. Part I, 

 hy Mr. Binney and Mr. T. Bland, in February, 1869 ; 

 and Part V, by Mr. Temple Prime, December, 1865. 

 An elaborate monograph of the Ilydrohiincc, a subfamily 

 of PissoidcB, treated in less detail by ]\lr. Binney in Part 



(iii) 



