April, 1910. Fishes of Chicago — Meek and Hildebranu. 259 



dd. Scales larger, 35 to 50 in lateral series; teeth 4-4. 



e. Scales between nape and dorsal fin slightly or not smaller than 

 those on rest of body; 12 to 16 in number; first short dorsal 

 ray closely attached to second. Hyhognathus , 261 



ee. Scales between nape and dorsal fin much smaller than those on 

 rest of body; 22 to 25 in number; first dorsal ray separated 

 from second by a membrane. Pimephales, 262 



bb. Alimentary canal less than twice the length of the body; 

 peritoneum usually pale. 



f. Premaxillaries protractile; scales in lateral series, usually less 

 than 60. 



g. No barbel at posterior end of maxillary. 



h. Mouth very small, its gape very oblique, making with vertical 

 an angle of less than 40°; peritoneum pale; teeth 4-5 or 5-5. 



Opsopceodus, 263 



hh. Mouth larger, its gape horizontal or more or less oblique, mak- 

 ing with the vertical an angle of more than 40°. 



i. Abdomen behind ventral fins with a sharp keel-like edge over 

 which the scales do not pass; lateral line much decurved, con- 

 curved with the ventral outline ; body much compressed ; teeth 

 5-5; anal rays 12 to 14. Notemigonus, 264 



ii. Abdomen behind ventrals rounded, its surface fully scaled. 



j. First dorsal ray separated from second by a membrane; snout 

 blunt; teeth 4-4. Cliola, 265 



jj. First ray of dorsal closely attached to second. 



k. Lips normal, nowhere conspicuously thickened. 



I. Lower portion of head without externally visible mucous 

 channels. Notropis, 266 



II. Lower portion of head with distended mucous cavities, ap- 

 pearing externally as transverse vitreous streaks. 



Ericymba, 275 

 kk. Lower lip thickened at each side forming fleshy lobes. 



Phenacohius, 276 



gg. One or two barbels at or near posterior end of maxillary. 



m. Maxillary barbel or barbels terminal; scales large, 35 to 45 in 



lateral series, 14 to 25 in series before dorsal. Hybopsis, 277 



mm. Barbel on upper side and near tip of maxillary; scales smaller, 



50 or 60 in the lateral series. About 35 scales in series before 



dorsal. Semotilus, 280 



ff. Premaxillaries not protractile; scales small, more than 60 in 



the lateral series. Rhinichthys, 281 



