;_• THE I • MINNESOTA 



a. Annulus b6 not obviously enlarged and subdivided. 



18. Eyes three pairs; male orifice at X\lb2/ct2, fe- 



male at XII&5/&<5; atrial horns simply 

 curved and vas deferens reaching forward 

 to the level of ganglion XL 



Erpobdella punctata, 121 

 aa. Annulus b6 obviously enlarged and subdivided. 



19. Eyes four pairs ; male orifices at XIlb2/a2, fe- 



male at XII bj/b6; atrial horns spirally 

 turned, vas deferens reaching forward to the 

 level of ganglion XI. 



Nephelopsis obscura, 123 



20. Eyes four pairs ; male orifice at XII bi/a2 or 



occassionally XII aj/bj, the female at XIII 

 bi/b2, atrial horns simply curved, vas defer- 

 ens reaching forward to ganglion XI. 



Dina parva, 125 



21. Eyes three or four pairs; male orifice at XII 



b2la2, female at XII bj/b6; atrial horns 

 simply curved, vas deferens not reaching 

 anterior to atrium. Dina fervida, 127 



