28 
Plate I 
Figures 1-7. Helisoma corpulentum (Say). Figures 1-5, 7, lac la Croix, Out., University 
Illinois, Z32624; figure 4, shell about size of Say's type, University Illinois. Z32625; 
figure 6, Rainy lake, Out., Baker coll., 1101. 
Figures 8-13. Helisoma corpulentum vermilionense F. C. Baker. Vermilion lake, Minn. 
Figure 8, holotype, Baker coll., 3021; others paratypes, Baker coll., 3014. Figures 
7 and 10 back views of corpulentum (7) and vermilionense (10). 
Figures 14-20. Helisoma corpulentum multieostatum F. C. Baker. Kalinipiminanikok 
lake, Ont. Figure 14, holotype Z3230G; figures 15-17, paratypes, University Illinois, 
Z32307. Figures 18-20, Birch lake. Out., Z308G4. 
Figures enlarged l£ diameters. 
