l.KHYMBA 157 



caudal peduncle as a rule about % length of head, slender, its depth con- 

 tained 2.2 to 2.9 in its length. Color pale olive above, the scales rather nar- 

 rowly and indistinctly dark-edged; sides pale silvery with bluish reflections; 

 a dark dorsal streak and an indistinct plumbeous lateral band developed 

 posteriorly; no caudal spot; fins all 

 plain; cheeks and opercles bright silvery; 

 iris silvery below, with some dusky 

 above; spring males without bright 

 colors. Head long for its depth, de- 

 pressed above, with prominently de- 

 curved muzzle: chin broad and flat; 

 length of head 3.5 to 3.7 in body and 

 head, its width 1.9 to 2.4 in its length; 

 interorbital space nearly flat and quite 

 narrow, 3.5 to 3.9 in head; eye 3.3 to FlG 38 



to 3.6 in head; suborbitals, inter- 



opercles, and lower jaw-bones with greatly developed mucus channels, 

 appearing externally as vitreous streaks; nose 2.6 to 3 in head, always dis- 

 tinctly longer than eye; mouth small, horizontal, subinferior, tip of upper 

 lip below level of lower margin of orbit; maxillary 3.5 to 4 in head, not reach- 

 ing past anterior nostril-opening; lower jaw much shorter than upper; 

 isthmus less than pupil. Teeth 4-4, or 1, 4-4, 1, rather strongly hooked, 

 the grinding surface somew T hat weakly developed as a narrow groove whose 

 edges are smooth; intestine .9 to 1.0 times length of head and body; peri- 

 toneum bright silvery, with a very few scattered dark specks. Dorsal fin 

 with 8 rays, set nearly directly over ventrals, but distinctly nearer tip of 

 snout than base of caudal; longest dorsal ray 1.1 to 1.2 in head; anal rays 8, 

 sometimes 7; pectorals long, reaching nearly to ventrals; ventrals past vent 

 but not quite to front of anal. Scales 5, 32-35, 3; 13 to 15 rows before 

 dorsal; breast without scales; lateral line nearly straight. 



This interesting little fish is especially peculiar because of the 

 tubular cavities, the so-called mucus canals, in the bones of the 

 side of the head and the lower jaw. It has, on the whole, an 

 easterly distribution, ranging, according to Jordan and Ever- 

 mann, from Michigan and western Pennsylvania to Kansas and 

 southward to western Florida. In our collections it has been 

 limited almost wholly to the central eastern part of the state, 

 occurring chiefly in the headwaters of the minor tributaries of 

 the Wabash and in the upper course of the Kaskaskia River, 

 and in the tributaries of the Iroquois and of the Sangamon. 

 The distribution map of the state for this species suggests a 

 relation to an eastern center, and an extension past the water- 

 sheds from the tributaries of the Wabash to the headwaters of 

 adjacent streams. Our 74 collections came in so large a propor- 

 tion from the smaller streams that the coefficient of frequency 

 for creeks is 4.85, and that for the smaller rivers is 1.06. It has 



