SCHILBEODES 201 



gyrinus, offer an interesting example of the methods by which 

 closely related species may avoid disadvantageous competition 

 with each other, flavus and miurus occupying similar situations 

 in similar waters, but mainly distributed in different parts of the 

 state, while gyrinus, with its general distribution covering the 

 area of both the other species, is related differently from these 

 both to water bodies and to situations in them. Like both the 

 other species mentioned, miurus has a wide general range which 

 offers no explanation of its limited distribution in Illinois. 



From the tributaries of Lake Michigan on the north it 

 ranges south to Louisiana and west to the lower part of the Mis- 

 souri basin. Hay, in his list of Indiana fishes, mentions its 

 occurrence in Minnesota and North Carolina. 



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