18 



Placopharynx duquesnci (Le Sueur). — Red-horse. (85) 



Not certainly distlneulshable from M. aureolutn without removal and examination of 

 the pharyngeal teeth. Occurs In Illinois, but out collections have not yet been carefully 

 enough examined to determine how frequently it may have been mistaken for M. aureolum. 



Family Cyprinid.e (The Minnows).* 



KEY TO THE GENERA OF ILLINOIS CYPRINID^. 



(It must be understood that this key is intended only for Illinois representatives of 

 these genera, and in many cases will not apply to those found elsewhere.) 



a. Minnows with Intestine of length more than twice that of the body; peritoneum 

 usually black or dark gray. 



b. Intestine spirally wound around the air-bladder Campostoma. 



bb. Intestine not wound around the air-bladder, 



c. Scales small, about 63 to 80 in lateral line. 



d. Body plain silvery Oxtqeneum. 



dd. Body striped longitudinally, frequently highly colored Cheosomus. 



cc. Scales larger, about 37 to 45 in lateral line. 



e. Scales not crowded before the dorsal, and not differing: much In size from those 



on other parts of the body; breast scaly; first ray of dorsal slender and closely 

 attached to second Hyboqnathus. 



ee. Scales small and irregularly crowded before the dorsal; breast naked; first 

 ray of dorsal ^ the length of second, not closely attached to it, a mem- 

 brane Intervening Pimkphales. 



aa. Minnows with intestine short, less than twice the length of the body; peritoneum 

 usually pale. 



f. Maxillary without evident barbel. 



g. Scales minute, 70 or 80 in lateral line.k, 



gg. Scales larger, less than 70 in lateral line. 



h. Mouth very small, upturned; lower jaw more nearly vertical than horizontal 

 when mouth is closed: angle formed by cleft of mouth and long axis of body 

 more than 45 degrees Opsopceodus. 



hh. Mouth horizontal or more or less oblique; angle formed by cleft of mouth and 

 long axis of body less than 45 degrees. 



i. Body strongly compressed between ventrals and anal fln. forming a ventral 

 keel over which the scales do not pass Abeamis. 



11. Body not strongly compressed ventrally. ' 



j. First ray of dorsal club-like and not in close contact with the second ray, a mem- 

 brane intervening Cliola. 



jj. First ray of dorsal slen '"7 and attached closely to the second. 



k. Upper lip not mnch thickened near angles (lips thin); mouth horizontal or ob- 

 lique. 



I. Lower portion of head normal, not swollen Notbopis. 



II. Lower portion of head swollen, semitransparent; rectangular mucous cavities 



apparent in bones of face Ericymba. 



kk. Upper lip much thickened at angles, giving appearance of sucker mouth; snout 

 somewhat projecting, mouth Inferior, horizontal Phenacobius. 



ff. Maxillary with a barbel at or near the extremity. This is sometimes quite small 

 and difficult to see in preserved specimens. 



m. A pair of barbels on the upper lip a short distance from the distal extremity, 

 n. Scales 50 to 60; eye small, one-fifth the length of head; dorsal usually .with 

 rays Semotilds. 



nn. Scales 60 to 70; eye large, as long as snout; dorsal usually 8.' 

 mm. Barbels at the distal extremities of upper lip. 

 0. Scales small, 60 to 70 in the lateral line; premaxlllary not protractile. 

 Khinichthys. 



* The common German carp {Cvprinus carpio), belonging to the family CyprinidjB, 

 though not native to Illinois waters. Is now found in all streams of the State. It may be 

 recognized by the two long barbels at either side of the mouth, and by the long spine at the 

 front of the dorsal. The large number of rays of the dorsal and the form of the body fre- 

 quently lead to a confusion of this fish with the buffaloes. 



' LeHciseus; a genus not certainly known to occur in this State. 



' Couesius vlumbeus; a northern form, which may occasionally be found in Illinois. 



