HYBOPSIS 165 



An uncommon species in this state, its known localities being 

 one on the lower Kaskaskia, one on the upper Embarras in Coles 

 county, one on the Sangamon in Macon county, one on the Kick- 

 apoo in Logan county, one on Spoon River in Fulton county, and 

 four on Rock River, in Lee and Winnebago counties. In north- 

 ern Illinois it has been taken chiefly in swift water flowing- 

 over sand. Outside the state it is to be found from Lake Erie 

 to the headwaters of the Tennessee, west to Arkansas and Iowa, 

 and north to the Saskatchewan River and to Calgary. 



HYBOPSIS AMBLOPS (Eafixesque) 



BIG-EYED chub; SILVER CHUB 

 (Map XLIX) 



Rafinesque, 1820, Ichth. Oh., 51 (Rutilus). 



G., VII, 179 (Ceratichthys hyalinus); J. & G., 214 (Ceratichthys) ; M. V., 64; J. & 

 E., I, 320; J., 62 (Ceratichthys); F., 75 (Semotilus) ; L., 19. 



Length 2 to 3 inches; a small but rather robust species, the body less 

 slender and more compressed and the eye larger than in H. dissimilis; depth 



4.6 to 5.2 in length, being greatest in 

 the predorsal region; caudal peduncle 

 rather slender, its depth 2.2 to 2.5 in 

 its length. Color olivaceous, overlaid 

 above with translucent greenish and 

 with silvery on sides; scales above lateral 

 line everywhere finely punctulate, only 

 Fig. 43 indistinctly dark-edged; a dusky to 



blackish lateral stripe continued forward 

 through eye to end of snout; no vertebral streak or caudal spot; fins all plain; 

 males and females similarly colored. Head 3.6 to 3.9, broad and flattened 

 above; width of head 1.9 to 2 in its length; interorbital space 3 to 3.9 in 

 head; eye large, usually longer than interorbital space or snout, 2.8 to 3.1 

 in head; muzzle bluntly decurved, the nose 2.9 to 3.4 in head, projecting 

 sometimes as much as width of pupil beyond mouth; mouth small, hori- 

 zontal, inferior, the tip of the lower jaw little in advance of first nostril; 

 maxillary 3.6 to 4.6 in head, usually reaching to vertical from front of orbit; 

 barbel variable, usually rather small, sometimes scarcely discernible, and 

 as a rule not projecting below cheek; isthmus less than pupil. Teeth 1.4-4, 

 1, occasionally 4—4 or with the supernumerary tooth absent On one side; 

 teeth stoutish towards base, with a very small and sharp hook; grinding 

 surface not much developed; intestine shorter than head and body; peri- 

 toneum coarsely specked with brown. Dorsal fin with 8 rays, set as a rule 

 almost directly over ventrals about equidistant between muzzle and base of 

 caudal; longest dorsal ray 1.1 to 1.3 in head; anal rays 7 or 8; pectorals about 

 M to ventrals; ventrals to vent. Scales 5, 35-38, 4 or 5; 12 to 15 rows in 

 front of dorsal; lateral line nearly straight. 



n 



