55 



There are two main drainage areas, one. very small, in the 

 northern part of the state, draining into Lake Michigan, and 

 the other, including the larger part of the state, draining into 

 the Mississippi River by way of the Illinois, Rock, Fox, I lesplaines, 

 Kankakee, Wabash, and Ohio, and other rivers and streams. 

 When the state is more thoroughly explored conchologically 11 

 will probably be found that its mollusks will show peculiar 

 geographical variations due to its extent through five ami ;i half 

 degrees of latitude (from 37° to42|°). 



While the literature relating to the Mollusca of Illinois is 

 rather extensive, it is a singular fact that not one catalogue 

 has been published which gives a list of all of the species of 

 the state. Some of the more extensive catalogues which have 

 been published are mentioned below. 



In 1854 Mr. H. A. Ulffers published a list of the Mollusca 

 of Southern Illinois inthe Transactions of the Illinois Horticul- 

 tural Society (Vol. I., p. 610). This included 87 species. Of 

 these, 14 are now r considered synonyms. 



In 1871 Mr. John Wolf published his "Catalogue of the 

 Shell-bearing Mollusca of Fulton County, Illinois," inthe Amer- 

 ican Journal of Conchology (Vol. VI., p. 27), listing 138 spe- 

 cies, of which 8 are now considered synonyms. 



In 1874 Mr. W. W. Calkins listed the Mollusca of Northern 

 Illinois in the Cincinnati Quarterly Journal of Science I Vol. I., 

 p. 321). This list included 129 species, of which but 6 are 

 now considered synonyms. The same author, in the Proceed- 

 ings of the Ottawa Academy of Sciences for ls74. enumerates 

 105 species as occurring in La Salle County. 



In 1887-89 Mr. William A. Marsh enumerated 110 species 

 of land and fresh-water shells as found in Mercer county, his 

 lists being published in the Conchologist's Exchange I \ ol. Land 

 II.) and in the Nautilus (Vol. III.). Several of the species listed 

 are now considered synonyms. 



Dr. W. S. Strode (Nautilus, Vol. V., p. 61, American Natur- 

 alist, Vol. XXVI., p. 495) enumerates :;:> species, mostly Unios, 

 from Spoon River, near Bernadotte. 



