GENERAL AND INTERIOR DISTRIBUTION XCV11 



in the Illinois valley. The Mississippi district is distinguishe 

 from the Illinois by the presence of the rare white sturgeon 

 (Parascaphirhynchus albus), hitherto taken only in the Missis- 

 sippi itself, arid by a southern darter and a western minnow 

 already referred to. In the Kaskaskia district we find another 

 southern darter (Etheostoma squamiceps). The six fishes of the 

 Wabash district not found in the Illinois or its tributaries, are 

 all southern species. The Big Muddy list contains no species 

 not found in the Illinois basin; and the Saline River district 

 contains two southern darters (Etheostoma squamiceps and E. 

 obeyense). And, finally, among the eight species by which the 

 Cairo district differs from the Illinois are three southern and 

 two western species, a cave-fish, and two species of general 

 distribution but rare in Illinois (Lampetra wilderi and Rhinichthys 

 cataractce) . 



Thus, of the twenty- three Illinois fishes not found by us in 

 the waters of the Illinois basin, eight are distinctively southern, 

 six are purely northern, if we include in this number the Great 

 Lake fishes, four are western, one is an extremely local cave- 

 fish, and four are so rare in Illinois that their appearance in any 

 waters is a matter of unusual chance. The limitation upon the 

 range of these imperfectly distributed species is thus climatic 

 and general, and not geographic or local. This state lies on the 

 extreme borders of their proper territory, and they are not found 

 more commonly in our waters because climatic and other general 

 conditions most favorable to their maintenance, here reach the 

 vanishing point. 



LISTS OF SPECIES DISTINGUISHING DIFFERENT DISTRICTS FROM THE ILLINOIS BASIN 



GALEXA DISTRICT (2): 



Hybognathus nubila (Western) 

 Crystallaria asprella (Southern) 



ROCK RIVER DISTRICT (3): 



Hybognathus nubila (Western) 

 Hadroplerus evides (Western) 

 Crystallaria asprella (Southern) 



MICHIGAN DISTRICT (9): 



Brook lamprey (rare) 

 Long-nosed sucker (Northern) 

 Whitefiah (Great Lakes) 

 Lake herring (Great Lakes) 

 Lake trout (Great Lakes) 

 Great Lake catfish (Northern) 

 Nine-spined stickleback (Northern) 

 Coitus icei (Great Lakes) 

 Uranidea kumlienii (Great Lakes) 

 7 P 



MISSISSIPPI STRIP (3): 



White sturgeon (rare; Mississippi only) 

 Hybognathus nubila (Western) 

 Crystallaria asprella (Southern) 



KASKASKIA RIVER DISTRICT (1): 



Etheostoma squamiceps (Southern) 



WABASH DISTRICT (6): 



Harelipped sucker (rare; Southern) 

 Pigmy sunfish (Southern) 

 Eupomotis heros (Southern) 

 Hadropterus ouachitce (Southern) 

 Crystallaria asprella ^Southern) 

 Etheostoma squamiceps (Southern) 



SALINE RIVER DISTRICT (2): 



Etheostoma obeyense (Southern) 

 E. squamiceps (Southern) 



