146 FISHES OF ILLINOIS 



front and upper margin of the dorsal charged with clear satin-white pigment 

 in males in the spring; basal half of dorsal in full breeding dress light green; 

 lower fins lemon-yellow, except tips of ventrals and anal. Head small, 

 subconic, not so stout as in the last species, 3.9 to 4.2 in length; profile scarcely 

 angled at nape; width of head 1.9 to 2.2; interorbital space 2.5 to 2.7 in head, 

 very convex; eye small, 3.9 to 4.8 in head; nose somewhat longer than in the 

 last species, 2.8 to 3.2 in head, conic and usually more or less upturned, 

 especially in males; mouth slightly less oblique than in the last, the tip of the 

 upper lip scarcely above level of lower margin of orbit; maxillary longer than 

 eye, reaching to back of posterior nostril-opening, but not to orbit, 3.1 to 

 3.6 in head; lower jaw shorter than upper; isthmus less than pupil. Teeth 

 usually 1, 4-4, 1*, the edges of the grinding surface often more or less crenate, 

 intestine .8 to .9 times length of head and body; peritoneum silvery, finely 

 specked with black. Dorsal fin with 8 rays, set a little behind the ventrals, 

 its longest ray usually a little less than head, in which it is contained 1.9 to 

 1.2; anal rays 8 or 9; pectorals 1.2 to 1.4 in head, about % to ventrals in fully 

 grown specimens, about y§ in young but sexually mature males; ventrals 

 to vent in females, past front of anal in males. Scales 6, 36-39, 3; 14 to 16 

 before dorsal, where they are scarcely crowded; lateral line clecurved anteriorly 

 to about parallel with lower outline. 



Extremely abundant in Illinois, especially in the smaller 

 streams of the central part of the state, and taken in 270 of our 

 collections. A species of the creeks and smaller rivers in this 

 state, its frequency ratios for those streams being approximately 

 2}^, while those for lakes and the larger rivers are but .11 and 

 .35 respectively. It shows a marked preference for swift water 

 and for a clean bottom, our coefficients for these situations being 

 1.3 and 1.6 respectively. It is generally distributed from Lake 

 Champlain and the St. Lawrence River through the lakes of 

 central New York and the Great Lake basin to Minnesota, 

 Pennsylvania, Virginia, northern Alabama, and Arkansas. 



Two thirds of the entire food of 33 specimens examined, con- 

 sisted of insects, nearly half of which were terrestrial. Three of 

 our specimens had eaten small fishes, and a mixture of vegetable 

 elements derived from both aquatic and terrestrial plants had 

 been eaten mainly by four, one of which had fed only on algae, 

 while three others had taken some 90 per cent, of their food 

 from miscellaneous plant structures, including seeds, anthers, 

 and pollen, and fragments of grass-like vegetation. 



Females apparently about to spawn have been taken by us 

 from May 21 to June 12, but others which had not yet deposited 

 their eggs occur in our collections occasionally up to the middle 



* Cases of apparent N. whipplii in which the teeth are 4-4 or 1, 4-4, 1 occur in a few collec- 

 tions from localities in which iV. lutrensis and A', uh'nijilii seem to intergrade. In general our 

 collections show, however, that little variation need be looked for in tins species. 



