298 The Molluscan Family Planorbidae 



PLATE 31 

 Helisoyna 



1-7. Helisoma corpulent lun (Say). From Knife Lake, Minne.?ota and Lake La Croix, 

 Ontario; collected by Dr. A. R. Cahn. 



1. Cross section of ovotestis. From Knife Lake. 



2. Cross section of prostate and uterus at X in fi^. 3. From Knife Lake. 



3. Genitalia dissected and organs separated. From Knife Lake. 



4. Penial complex with preputium pushed upward and penial gland duct imcoiled. 



5. Penial complex and penial gland duct in natural position. From Knife Lake. 



6. Penial complex of immature specimen, shell 12 nun. in diameter. From Lake 



La Croix. 



7. Penial complex of specimen with shell 14 mm. in diameter. From Lake La 



Croix. 



8-13. Helisoma corpulentinn multicostotum F. C. Baker. From Kahnipiminanicock 

 Lake, Ontario, Canada; collected by Dr. A. R. Cahn. 



8. Cross section of penial gland. Duct not shown. 



9. Penial complex of immature specimen, shell 5.5 mm. in diameter. Duct short. 



10. Penial comjilex of half-grown animal, shell 14.5 mm. in diameter. 



11. Penial complex of another half-grown specimen, shell 14.5 mm. in diameter. 



12. Penial complex of specimen almost adult, shell 16 mm. in diameter. 



13. Penial complex of adult animal, shell 23 mm. in diameter. Duct long, uncoiled. 



14-18. Helisoma corpulentum vermilionense F. C. Baker. From Lake Vermilion, Min- 

 nesota; collected by F. C. Baker. 



14. Penial complex showing preputium pushed upward. Duct imcoiled. 



15. Section of penial gland showing cup and penial gland duct. 



16. Penial complex, specimen about one-fourth grown. 



17. Penial complex in specimen somewhat older than fig. 16. 



18. Penial complex of animal about half-grown. Verge of different shape. 



19. Helisoma whiteavesi F. C. Baker. From Mille Lacs, Ontario, Canada; collected 

 by A. R. Cahn. 



19. Penial complex with small vergic sac, the penial gland duct uncoiled. 



20-22. Helisoma magnificiun (Pilsbry). From Greenfield Pond, 1 mile south of Wil- 

 mington, North Carolina; collected by Dr. Paul Bartsch. 



20. Penial complex with penial gland duct uncoiled. 



21. Penial complex in section. 



22. Penial gland in section. 



Line near figure indicates 1 mm. in length 



