Ixxxii 



FISHES OF ILLINOIS 



Arranged according to the number of Illinois species in each, 

 these districts succeed each other in the following order. 



Next to the two Mississippi Valley districts and the Great 

 Lake basin, which average 124 Illinois species, our fishes are 

 most largely represented in the east Gulf and the Quebec and 

 New England districts, averaging 54 Illinois species the first 

 closely related to the lower Mississippi, and the second a con- 

 tinuation eastward of the Great Lake basin. Then follow the 

 north and south Atlantic and the west Gulf districts, with an 

 average of 43 species; the far North, the Florida peninsula, and 

 the Hudson River districts, with 37 to 19 species; and, finally, 

 the far Northwest, with but 4 Illinois species. 



The northern and the southern affiliations of the assemblage 

 of fishes represented in our Illinois collect ons may be contrasted 

 by comparing the list of Illinois species occurring in either or 

 both of the more northerly divisions that is, the far North 

 and the Quebec and New England districts on the one hand, 

 with a list of those found in either or all of the three most 

 southerly districts that is, the Florida peninsula, the east 

 Gulf, and the west Gulf and Rio Grande on the other hand. 

 In this northern list of Illinois fishes there are 64 species, and in 

 the southern list there are 77; but 25 of these species are more 

 or less common to both north and south, leaving 39 Illinois 

 fishes distinctively northern in their distribution and 52 dis- 

 tinctively southern. Northern and southern species thus mingle 

 in our territory in unequal proportions, the southern element 

 largely preponderating. 



