270 The MoUuscan Family Planorbidae 



PLATE 17 



Gyraulus 



1-5. Gyraulus circumstriatus (Tryon). From Wainwright Park, near Mott Lake, 

 Alberta, Canada; collected by Dr. Swales. 



1. Genitalia dissected and organs separated. Outline. Penial complex in natural 



position. 



2. Distal end of genitalia showing duct connections. From left side. 



3. Pseudobranch and pneiunostome. 



4. Animal removed from shell showing position of several organs. 



5. Two diverticula of ovotestis in gravid condition. 



6-12. Gyraulus parvus (Say). From Winnebago Lake, near Oshkosh, Wisconsin; col- 

 lected by F. C. Baker. 



6. Genitalia dissected and organs separated. 



7. Distal end of genitalia, from left side. 



8. Portion of fore end of animal showing pseudobranch, etc. 



9. Albumen gland showing attachment of oviduct. 



10. Three di^'erticula of prostate with prostate duct below and sperm duct at the 



side. 



11. Two diverticula of ovotestis. 



12. Penial complex opened to show verge, stylet, papilla, etc. 



Line near figure indicates 1 mm. in length. Figures 5, 10, and 

 11 have same magnification as fig. 12. 



