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both species have been found most frequently in the eastern 

 part of the state. A close comparison of the distribution maps 

 shows that both have been taken from eighteen of the thirty lo- 

 calities in which the less abundant one was found; and they have 

 been taken together in seventeen of the one hundred and five 

 collections containing either or both. 



A comparison of their local preferences indicates a close 

 agreement in ecological relationship. Each of the species was 

 found in the larger rivers in 3 per cent, of the collections; zonale 

 in 97 per cent, of those from the smaller rivers and creeks, and 

 cceruleum in 89 per cent. — the remainder of the latter coming 

 from lowland lakes and ponds (1 per cent.) and from various 

 miscellaneous sources. Eighty-nine per cent, of the collections 

 of zonale and 83 per cent, of those of coeruleum were from streams 

 of swift or moderate flow; 89 per cent, of zonale and 92 percent, 

 of coeruleum, from rock and sandy bottom. The only notable 

 difference between these species is the preponderant disposi- 

 tion of zonale towards the smaller rivers rather than the 

 streams classed as creeks. 



The next highest coefficient (5.69) is that of Hadropterus 

 yhoxocephalus and Etheostoma zonale (1418 and 1461), which 

 have occurred together sixteen times in my one hundred and 

 one collections of one or the other. Both have been taken 

 from seventeen of the thirty localities in which we have found 

 zonale. The general distribution of the two differs but little, 

 except that zonale is very much less abundant than phoxocepha- 

 lus, and has been limited much more closely to the Illinois and 

 Rock river basins. The ecological ratios for zonale and phoxo- 

 cephalus respectively are, — larger rivers, 3 per cent, and 7 per 

 cent.; smaller rivers, 74 per cent, and 56 per cent.; creeks, 23 

 per cent, and 26 per cent. ; lakes and ponds, and 3 per cent. 

 The ratios of preference for rapid and slow waters respectively 

 are still more closely approximate — 89 per cent, of zonale and 

 87 per cent, of phoxocephalus from moderate or rapid currents. 

 The preferences of the two species for rock and sandy bottom 

 are similarly close— 89 per cent, for zonule and 94 per cent, for 

 phoxocephalus. 



