118 NORTHERN ITSIIES 



Bigmouth Buffalofish, Megastomatobus cyprinella (Valenciennes) 



Mouth small, lower and proctractile downwards; upi)er lip far below lower 

 margin of orbit; lips rather thick and coarsely striated; gill-rakers on first 

 arch all shorter than the longest gill-filaments of anterior row, less than 60 

 (counted from posterior face of arch) 5 



5. Back elevated and compressed; distance from mandibular symphysis to ex- 

 treme end of maxillary less than the length of orbit (between free rims of 



orbit) ; standard length more than 5 times thickness of head 



; Smallmouth Buffalofish, Ictiobus bubalus (Rafinesque) 



Back rounded and scarcely elevated; distance from mandibular symphysis 

 to extreme end of maxillary more than length of orbit; standard length less 



than 5 times thickness of head 



Black Buffalofish, Ictiobus niger (Rafinesque) 



6. Mouth mostly anterior to the nostrils (Diagram 6) 



Quillback, Carpiodes cyprimis (LeSueur) 



Mouth mostly posterior to the nostrils (Diagram 6) 7 



7. Adults with anterior rays of dorsal fin very much lengthened, sometimes 



equaling the length of the base of the fin 



Highfin Sucker, Carpiodes velifer (Rafinesque) 



Adults with anterior rays of dorsal fin scarcely elevated 



Northern Carpsucker, Carpiodes carpio earpio (Rafinesque) 



8. Lateral line absent or incomplete in adult; greatest depth more than one- 

 fifth standard length 9 



Lateral line complete and continuous in adult; greatest depth less than 

 one-fifth standard length 11 



t). Lateral line wholly lacking at all ages; body oblong; scales in lateral line 

 usually 36-41; markings consist of two longitudinal streaks in young, 

 more or less combined with, or replaced by, narrow vertical bars in adult. . . 

 (Genus Erimyzon) 10 



10. Dorsal rays usually 11, sometimes 12; scale rows usually 36-38; depth in 

 adult seldom more than one-third standard length (to last vertebra) ; size 



large, up to 10 inches in length 



Western Lake Chubsucker, Erimyzon sucetta kennerlii (Girard) 



Dorsal ray usually 10, sometimes 11; scale rows usually 39-41; in adults 

 depth usually contained more than 3.4 times in standard length; length less 



than 6 inches 



Western Creek Chubsucker, Erimyzon oblongus claviform,is (Girard) 



11. Scales small and crowded anteriorly, 55-110 in the lateral line 



(Genus Catostomus) 12 



Scales large and nearly equal all over the body, less than 50 in the lateral 

 line 13 



12. Scales very small, more than 80, about 100 in the lateral line; snout pointed 

 . .Northern Sturgeon Sucker, Catostomus catostomus catostomus (Forster) 

 Scales larger, usually less than 80, about 65 in lateral line; snout not pointed 

 Com- 

 mon White Sucker, Catostomus commersonnii com.mersonnii (Lacepede) 



13. Air bladder in 3 parts; scales in lateral line less than 50; head convex above 



(Genus Moxostoma) 14 



Air bladder in 2 parts; scales in lateral line 46-50; head concave above 



Hog Sucker, Hypentclium- nigricans (LeSueur) 



14. Halves of lower lip meeting at a rather sharp angle, sometimes becoming 



