1. Somites 5-annulate with all annuli equal in length; three pairs of eyes; gonopores separated by two annuli; length 100 mm. Preatrial loops of the male paired ducts simple, not coiled. . . . . . . . . . . . . . . . . Erpobdella punctata
Somites 6- or 7-annulate; annuli or unequal length units will be either subdivided or longer than the others; in any group of six consecutive annuli, at least one annulus narrower or wider than the others; three or four pairs of eyes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Four pairs of eyes, two labial and two buccal, of similar size. . . . . . . . . . . . . 4
3. Three and a half to four annuli between gonopores; body heavily blotched with median stripe; anus large, opening on a conical tubercle; length 60 mm. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Erpobdella dubia
Three to three and a half annuli between goonopores; nearly pigmentless or with a few dark spots; anus small, not on tubercle; length 30 mm. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Erpobdella parva
4. Three pairs of eyes; gonopores separated by three annuli; length 50 mm. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Erpobdella microstoma
Gonopores separated by 4-4 1/2 annuli; three paris of eyes; length 40 mm. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Erpobdella tetragon