V. HISTORICAL SKETCH OF PREVIOUS MONOGRAPHS. 



The fresh-water Pulmonata have been written upon to a greater 

 extent than almost any other group of mollusks, excepting perhaps, the 

 land snails. Scarcely a paper has been published on inland mollusks 

 that did not mention some member of the group, hence the literature 

 is extensive. Of illustrated monographs and other papers of a mono- 

 graphic character dealing with American Lymnseas, upwards of six- 

 teen have been published that are especially notable. These may be 

 summarized as follows : 



I. 1832-34. THOMAS SAY. In his American Conchology, Say, 

 the father of American Conchology, enumerates and figures 6 species 

 of the genus. The Journal of the Academy of Natural Science of 

 Philadelphia also contains descriptions of many species, published 

 between the years 1817 and 1825. The article "Conchology" in the 

 American edition of Nicholson's Encyclopedia of Arts and Sciences, 

 contains 2 species of Lymnsea. 



II. 1841. AUGUSTUS A. GOULD. In the Invertebrata of Massa- 

 chusetts, Dr. Gould lists and figures for the most part 7 species and 

 1 variety of Lymnsea from New England. This report was reprinted 

 in 1870 under the editorship of Mr. W. G. Binney. 



III. 1842. S. S. HALDEMAN. This is one of the best of the 

 monographs of Lymnsea, the figures being superb, exceeding in this 

 respect those of any other monograph. 24 species are described and 

 figured. An attempt is here made to divide the American Lymnseas 

 into subgeneric groups, five of which are recognized, two being de- 

 scribed as new. 



IV. 1843. JAMES E. DEKAY. In the Zoology of New York 23 

 species of Lymnsea are mentioned, 15 of which are figured. 



V. 1858. W. G. BINNEY. In Binney's edition of the complete 

 writings of Thomas Say on the Conchology of the United States 16 

 species are described, many of them being figured. 



VI. 1862 AND 1886. H. C. KUSTER and S. CLESSIN. *H. C. Kiis- 

 ter began a monograph of Lymnsea in the Conchylien Cabinet of Mar- 

 tini and Chemnitz in 1862 which was completed by S. Clessin in 1886. 

 40 American species are described and figured in the two parts of 

 this monograph. 



