SCHILBEODES 201 



which closely related species may avoid disadvantageous competi- 

 tion with each other, flavus and miurus occupying similar situations 

 in similar waters, but mainly distribued 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 explana- 

 tion of its limited distribution in Illinois. 



From the tributaries of Lake Mchigan on the north it ranges 

 south to Louisiana and west to the lower part of the Missouri basin. 

 Hay, in his list of Indiana fishes, mentions its occurrence in Minne- 

 sota and North Carolina. 



