142 



FISHES OP ILLINOIS 



caudal peduncle shorter than head, its depth 1.9 to 2 . 3 in its length. 

 Color very pale olive; sides with a very broad silvery to plumbeous 

 band; commonly a large black spot at base of caudal fin; scales faintly 

 cross-hatched on upper part of body and for a little distance below 

 lateral line forward; spots above and below pores of lateral line faint or 

 wanting; fins pale. Head short, 4.1 to 4 . 7 in length of head and body; 

 width of head 1.8 to 2.1; interorbital space 2.5 to 2.9; eye moderate, 

 2 . 8 to 3 . 5 in head, equal to nose or slightly shorter or longer in adults; 

 nose blunt, usually somewhat decurved, 3 . 2 to 3 . S in head ; mouth rather 

 -small, nearly horizontal, the tip of upper lip below level of lower margin 

 of pupil; maxillary usually not quite reaching orbit, 3.7 to 4. 5 in head; 

 lower jaw shorter than upper; isthmus less than pupil. Teeth variable: 

 "0, 4-4, 1 ; 1, 4-4, 1 ; 1 , 4-4, 2 ; or 2, 4-4, 2 ; teeth of main row more or less 

 hooked, and generally quite compressed, the grinding surface developed 

 as a quite narrow groove whose edges are smooth; intestine .9 to 1.4 

 times length of head and body ; peritoneum silvery, finely but not densely 

 specked with dark. Dorsal fin with 8 rays, set usually a trifle in advance 

 of the ventrals and nearer snout than base of caudal; longest dorsal ray 

 about equal to the length of the short head ; anal rays 8 ; pectorals scarcely 

 | to ventrals; ventrals usually short of vent. Scales 5 or 6, 36 to 39, 4; 

 15 to 18 before dorsal; longitudinal rows of scales above lateral line with 

 the appearance of "running out" behind dorsal fin, as in N. cormttus; 

 lateral line usually complete, not much decurved anteriorly. 



( ia 



Fig. 36 



This abundant, graceful, and we'1-known species, essentially 

 a northern minnow in this state, is much the most abundant in our 

 largest rivers and in lakes, its frequency ratio in the former being 

 1.8, and in the latter 1.76. In small rivers and in creeks it has been 

 taken only occasionally, the corresponding ratios being .29 and .14. 

 It is abundant in its favorite localities, and appears in 147 of our 

 collections. In Illinois it is limited to the Mississippi and Lake 

 Michigan drainage, and has occurred but twice south of the central 

 part of the state, once in Union county and once from the Ohio at 

 Cairo. We have found it most frequently in the Illinois River and 

 its adjacent waters at Havana and Meredosia, from which two 

 places 119 of our collections have come. It is also one of the com- 



