The Nautilus. 



Vol. v. OCTOBER, 1891. No. 6. 



MOLLUSKS OF SPOON KIVEK, ILL. 



BY DR. W. S. STRODE, BERNADOTTE, ILL. 



Spoon river is a tributary of the Illinois, For a hundred miles 

 from its junction with that stream its average width is about one 

 hundred and fifty feet. It is a clear, swift-running stream, pursuing 

 a sinuous course through a valley a half mile wide. Its banks are 

 fringed by willows that here and there sweep the current in rhythmi- 

 cal response to every passing breeze. Overshadowing this border 

 are silver-leafed maples, elms, and intertwining undergrowth, and 

 beyond, towering above all like gigantic sentinels, stand the monarchs 

 of the forest — giant sycamores. 



Ko systematic study of the mollusks of this river has ever been 

 made. Prof. Jno. Wolf, an aged naturalist of Canton, 111., has 

 made some researches, and probably knows more of the mollusks of 

 the Illinois and Spoon Rivers than does any other living man, but 

 he has written little of his discoveries. 



Some of the Unios found, attain a size and perfection of form 

 rarely equalled by shells of the same species found elsewhere. This 

 perfection is due to the fact that each species finds in the variety of 

 deep and shallow water, swift and sluggish currents, deposits of 

 black mud, blue clay, sand, rock, and gravel, or a mixture of all 

 these, the environment most suitable for perfect development. 



Specimens of U. multiplicatiis have been found over eight inches 

 in length, and weighing three pounds. Margaritana comiilanata also 



