Key to the Species of Nocomis

2a. (From 1b.) Tubercles on head in two rows between nostrils and eyes and one row above each eye; total number of tubercles 7 to 9, usually 8.
bluehead chub

Nocomis leptocephalus interocularis

2b.  (From 1b.) Tubercles on head in one row between nostrils (absent between eyes); no row of tubercles above each eye; total number of tubercles 4 to 6, usually 5.
bluehead chub

Nocomis leptocephalus bellicus