407 
Five species were found in the Illinois system and not in any 
other—three of them minnows of the genus Notropis (anogenus, 
phenacobius, and pilsbryz), one of them a sunfish (Lepomts euryorus), 
and one of them a darter (Hadropterus evermannt). All of these spe- 
cies 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 espe- 
cially by the presence of a minnow and a darter (Hybognathus 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, to- 
gether 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 lake trout, and two cottoids 
or miller’s thumbs, Cottus ricer and Uranidea kumlienti—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 in the 
Illinois valley. The Mississippi district is distinguished from the 
Illinois by the presence of the rare white sturgeon (Parascaphirhyn- 
chus albus), hitherto taken only in the Mississippi itself, and by a 
southern darter and a western minnow already referred to. In the 
Kaskaskia district we find another southern darter (Etheostoma squam- 
iceps). The six fishes of the Wabash district not found in the Illinois 
or its tributaries, are all southern species. The Big Muddy list con- 
tains no species not found in the Illinois basin; and the Saline River 
district contains two southern darters (Etheostoma squamiceps and 
E. obevense). 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 wildert and Rhintchthys cataracte). 
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 
