130 FISHES OF ILLINOIS 



its frequency coefficients for those stream systems (3.31 and 2.27 

 respectively) being many times those for any others in the 

 state. It is an exception to the general rule in the fact that it 

 enters freely the lower Illinoisan glaciation, notwithstanding its 

 evident preference for clear water. 



Gravid females occur in our June collections, and in others 

 taken as early as the 21st of May. Females are uniformly 

 smaller than males, and the latter are further distinguished in 

 spring by nine large tubercles on the snout, five of them in a 

 row just above the upper lip, two additional ones between the 

 nostrils, and one on each side between the nostril and the eye. 



GENUS NOTROPIS EAFINESQUE 



Body oblong or elongate, either more or less compressed; mouth mostly 

 terminal and oblique, sometimes subinferior; premaxillaries protractile; no 

 barbels; teeth in 1 or 2 rows, the main row always 4-4; peritoneum as a rule 

 pale, though often dusky, and in some species black (anogenus}; dorsal rays 

 usually 7 or 8; anal rays ordinarily 7 or 8 (or 9), in a few species 11 or 12; 

 scales usually rather large, as a rule less than 40 in lateral series; lateral line 

 complete or imperfect. Size usually small, most species not exceeding 3 or 

 4 inches. A very large group, embracing about 100 species, all confined to 

 the fresh waters of America east of the Rocky Mountains; 17 species in 

 Illinois. 



KEY TO THE SPECIES OF NOTROPIS FOUND IN ILLINOIS 



a. Anal rays typically 7 or 8; occasionally 9 in two compressed forms (see bb, 



below), in which, however, scales before dorsal are not over 17, and no 

 black spot is present at base of first dorsal rays; teeth 4-4; 1, 4-4, 1; or 

 1 or 2, 4-4, 1 or 2. 



b. Eye moderate, 2% to 2% in head, always less than 4; body not usually much 



compressed, the back gently and broadly rounded in front of dorsal fin; 

 scales not closely imbricated; teeth 4-4; 1, 4-4, 1; or 1 or 2, 4-4, 1 or 2. 



c. Small species, seldom over 2% inches in length; with (1) a black lateral 



stripe along sides and through eye to end of snout, or (2) a conspicuous 

 dark spot above and below each pore of lateral line anteriorly, or (3) pale 

 species, with no vertebral streak and the spots above lateral pores incon- 

 spicuous; teeth 4-4 or 1, 4-4, 1 (except heterodon). 



d. Eye 3 or more in head (sometimes under 3 in heterodon, in which dark 



lateral stripe extends through eye to end of snout, tipping chin) ; small, 

 usually less than 2% inches. 



e. Scales before dorsal large, 12 to 15 in number; teeth 4-4 (except heterodon). 



f. A black stripe along sides through eye to end of snout. 



g. Chin white; mouth small, nearly horizontal, the upper lip below level of 



lower margin of pupil cayuga. 



gg. Chin black at tip; mouth moderate or very small, oblique, tip of upper lip at 

 level of upper margin of pupil. 



