CVl J FISHES OF ILLINOIS 



Notropis cayuga Yellow perch 



N- heterodon Banded darter 



Straw-colored minnow Rainbow darter 



Notropis gilberti Fan-tailed darter 



Spot-tailed minnow White bass 



Common shiner Yellow bass 



Notropis jejurms Miller's thumb 



Fishes Tolerant of the Lower Illinoisan Glaciatio 



Dogfish Silver chub 



Channel-cat Grass pike 



Yellow bullhead Common top-minnow 



Black bullhead Viviparous top-minnow 



Mud-cat Pirate-perch 



Tadpole cat White crappie 



Brindled stonecat Round sunfish 



Chub-sucker Warmouth 



Striped sucker Green sunfish 



Silvery minnow Long-eared sunfish 



Blunt-nosed minnow Orange-spotted sunfish 



Opsoposodus emilice Large-mouthed black bass 



Golden shiner _ Black-sided darter 



Bullhead minnow Boleosoma camurum 



Silverfin Sand darter 



Shiner Etheostorna jessiw 



Blackfin Boleichthys fusiformis 

 Ericymba buccata ■ 



Among the ninety-eight Illino"s species for which distribu- 

 tion maps have been prepared, thirty-four belong clearly to this 

 group of fishes which seem to avoid the conditions common to 

 the flat gray lands of the southern part of the state. Thirty-five 

 species, on the other hand, are distributed over this glaciation in 

 a way to indicate a tolerance of its conditions if not an indiffer- 

 ence to them, the data concerning the remainng twenty-nine 

 species being ambiguous or indecisive in this respect. 



Two facts concerning the soil and waters of the lower Illi- 

 noisan glaciation may be held to account, at least in part, for 

 the failure of certain species of fishes to thrive in its streams. 

 Compared with the other regions of the state, this oldest of our 

 glaciation areas has developed its drainage system to a point 

 such that the rainfall runs off rapidly in a large number of small 

 streams, leaving no marshes or ponds to hold back the waters 

 during periods of dry weather. It is a level country whose 

 streams fill up quickly and run down rapidly, the smaller ones 

 drying up completely during the midsummer drought, which is 

 here more marked than farther north. These variable and tem- 

 porary creeks are, of course, less favorable to the maintenance of 

 a varied and permanent fish population than the waters of the 

 earlier Illinoisan or the Wisconsin areas. 



