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 northern 

 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 head- 

 waters of the Tennessee, west to Arkansas and Iowa, and north to 

 the Saskatchewan River and to Calgary. 



HYBOPSIS AMBLOPS (Rafinesque) 

 (big-eyed chub; silver chub) 



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



G.,VII, 179 (Ceratichthys hyalinus); T- & 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 great- 

 est in the predorsal region ; caudal ped- 

 uncle 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 lat- 

 eral line everywhere finely punctulate, 

 ^^'^- ^^ only indistinctly dark-edged ; a dusky to 



blackish lateral stripe continued for- 

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

 all plain ; miales 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, horizontal, 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 , occasionallv 4-4 or with the supemumerar}^ tooth 

 absent on one side; teeth stoutish towards base, with a very small and 

 sharp hook; grmuing surface not much developed; intestine shorter than 

 head and body; peritoneum 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 | to ventrals; ventrals to vent. Scales 

 5, 35-38, 4 or 5: 12 to IS rows in front of dorsal; lateral line nearly 

 straight. 



(12) 



