288 The Molluscan Family Planorhidae 



PLATE 26 



Helisoma 



1-5. Helisoma horni (Tiyon). From Paul Lake, British Columbia; collected by Prof. 

 D. S. Rawson. 



1. Penial complex in breeding condition, the preputium pushed upward. 



2. Outline of penial gland. 



3. Outline of genitalia dissected and organs separated. 



4. Cross section through oviduct, sperm duct, and nidamental gland. 



5. Cross section through prostate and o\iduct, near middle of gland. 



6-13. Helisoma iruncatum (Miles). From Winnebago Lake, near Oshkosh, Wisconsin; 

 collected by F. C. Baker. 



6. Penial complex with penial gland duct in normal position coiled on surface of 



preputium. 



7. Penial complex with penial gland duct pulled out to show great length. 



8. Cross section of ovotestis near anterior end. 



9. Cross section of penial gland. 



10. Cross section of prostate and oviduct near anterior end. 



11. Head showing position of pseudobranch, pneumostome, and rectum. 



12. Penial complex with penial gland duct spread out. Preputium is partly pushed 



upward. 



13. Genitalia dissected and organs separated. 



Line near figure indicates 1 mm. in length 



