118 THE CHICAGO ACADEMY OF SCIENCES. 



VII. 1865. W. G. BINNEY. Land and Fresh-Water Shells of 

 North America. This is the most complete and pretentious mono- 

 graph of American Lymnseas which has yet been published and has 

 been constantly referred to by all workers on this group of snails. 

 Its great drawback has been the extreme conservatism with which the 

 author treated the species, placing many names in the synonymy of 

 other species which, upon recent critical study, have been found to 

 be worthy of recognition. 31 species are considered valid by Binney. 

 Figures (mostly outline) are given of all the species of American Lym- 

 nseas, which had been described at that time, some 80 in all. 



VIII. 1872. GEO. W. TRYON, JR. Continuation of Haldeman's 

 Monograph of the Fresh-Water Univalve Mollusca of the United 

 States. In this monograph 37 species are recognized, 32 figures being 

 given on three plates. An attempt is made to utilize a number of group 

 names in a subgeneric sense. While not as conservative as Binney, 

 Tryon's work nevertheless shows that little critical study was given to 

 the smaller species of the genus. 



IX. 1872. G. B. SOWERBY in Reeves' Conchologica Iconica. In 

 this monograph, which is fairly well illustrated, 40 species of Ameri- 

 can Lymnaeas are recognized and figured. 



X. 1880. FISCHER, PAUL and CROSSE, H. In the Mission Scien- 

 tifique au Mexique et dans 1'Amerique Central, these gentlemen de- 

 scribe 4 and figure 2 species of southern Lymnaeids. 



XI. 1874. W. D. HARTMAN and EZRA MICHENER, in Concholo- 

 gia Cestrica, figure and describe 8 species of Lymnaea from the eastern 

 part of the United States. 



XII. 1899. EDUARD VON MARTENS. In the Biologia Centrali 

 Americana, Mollusca, .this author describes 6 species of Lymnaeids 

 principally from the Central American region. 



XIII. 1900. R. E. CALL. In his report on the Mollusca of In- 

 d 1 'ana, this author describes and figures 5 species. 



XIV. 1902. F. C. BAKER. In the Mollusca of the Chicago Area, 

 Part II, this author describes and figures 10 species of Lymnseas which 

 inhabit northern Illinois. 



XV. 1904. JOSIAH KEEP. In West American Shells, this 

 author describes 9 and figures 4 species of west coast Lymnaeas. 



XVI. 1906. W. H. BALL. In the Land and Fresh- Water Mol- 

 lusks of Alaska, this author figures 26 species of Lymnaeas as occur- 

 ring in the northern part of the United States and in British America. 

 This essay is the first attempt to place the classification of this group 

 of fresh-water shells on a modern basis. 



