XCV1 



FISHES OF ILLINOIS 



Differences between the Smaller Districts and the Illinois Basin 



Districts 



Ratios 

 of differ- 

 ence 



Illinois .... 

 Michigan. . 



Cairo 



Wabash . . . 

 Galena. . . . 



Saline 



Mississippi . 

 Rock River 

 Kaskaskia . 

 Big Muddy 



.16 



.08 



.061 



.046 



.038 



.032 



.032 



.014 



.000 



Five species were found in the Illinois system and not in 

 any other — three of them minnows of the genus Notropis 

 (anogenus, phenacobius, and pilsbryi), one of them a sunfish 

 (Lepomis euryorus), and one of them a darter (Hadropterus 

 evermanni). All of these species have been very rare in our 

 collections, occurring only from one to three times each, and it 

 was probable that they would be found, if at all, where the largest 

 number of collections was made. 



The Galena district is distinguished from the Illinois basin 

 especially by the presence of a minnow and a darter (Hybog- 

 nathus nubila and Crystallaria asprella), the latter southern in 

 its main range, and the former western, not occurring, indeed, 

 farther east than western Illinois. These two fishes appear in 

 the Rock River basin also, together with another distinctively 

 western darter (Hadropterus evides). In the Michigan district, 

 besides the five lake fishes already referred to — the whitefish, 

 the lake herring, the !ake trout, and two cottoids or miller's 

 thumbs, Coitus ricei and Uranidea kumlienii — are the brook 

 lamprey, the long-nosed sucker, the Great Lake catfish, and one 

 of the sticklebacks (Pygosteus pungitius). All but the lamprey 

 (•which is rare in Illinois) are northern species not taken by us 



