136 FISHES OF ILLINOIS 



have about 80 collections, chiefly from the sluggish waters of the 

 Illinois River and tributary lakes at Havana and Meredosia, in 

 which the dentition is more usually 2, 4-4, 2, and the lateral line is 

 nearly always complete. 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 Illinoisan 

 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 equal- 

 ly abundant from northern and from central Illinois, but is con- 

 siderably 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 Entotnostraca 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 speci- 

 mens examined were taken where Entomostraca were very abundant 

 at the time. Aquatic insect larvae, mainly Chironomus, an am- 

 phipod crustacean (Allorchestes) . and flowers and seeds, with fila- 

 mentous 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. 



*N 'otropis heterodon, var., Gilbert, Proc. U. S. Nat. Mus., 1884, p. 207. 



