136 FISHES OF ILLINOIS 



more usually 2, 4-4, 2, and the lateral line is nearly always com- 

 plete. Collections of the same form, which may be identical 

 with the unnamed* variety of N. heterodon described some years 

 ago from Switz City swamp, Indiana, and localities in southern 

 Illinois, have also been taken in lowland streams of the Wabash, 

 Ohio, and Big Muddy valleys. 



New York to Michigan, Minnesota, and Kansas, including 

 Lakes Michigan and Huron and the Ohio basin. Distributed 

 sparingly throughout the state, mainly in the lowland and glacial 

 lakes, and in a way to indicate an avoidance of the lower Illi- 

 noisan glaciation. Our 93 collections, from 21 localities, were 

 derived in extraordinarily small proportion from either creeks 

 or rivers of the smaller size. The order of relative abundance 

 in our waters is as follows: glacial lakes, 2.68; lowland lakes, 

 1.44; the larger rivers, .98; creeks, .63; and the smaller rivers, 

 .17. It is about equally abundant from northern and from 

 central Illinois, but is considerably less common in the waters 

 of the southern part of the state. 



The food of eighteen specimens studied, was peculiar in 

 respect to the large percentage of Entomostraca included — a fact 

 perhaps to be accounted for by the small size of the species and 

 the somewhat unusual development of the gill-rakers, although 

 many of the specimens examined were taken where Entomostraca 

 were very abundant at the time. Aquatic insect larvae, mainly 

 Chironomus, an amphipod crustacean (Allorchestes) , and flowers 

 and seeds, with filamentous algae, were the other principal 

 elements of the food. 



The species spawns in May and June in central Illinois. 

 The snout and top of the head of the male are finely tuberculate. 



* Nolrojris heterodon, var., Gilbert Proc. U. S. Nat. Mus. 1884 p. 207. 



