276 The MoUuscan Family Planorhidae 



PLATE 20 



Planorbarius corneus (Linn.)- 



From branch of Wista River at Morysinek, 5 km. .south of Warsaw, Pohuid; 

 collected by A. Jankovvski. 



1. Penial gland and appendages in extended position. 



2. Section through appendage at C in fig. 1. 



3. One diverticulum of ovotestis with ripe ovum (greatly enlarged). 



4. Cro.ss section through prostate, uterus, and nidamental gland. 



5. Cross section of ovotestis in gravid specimen. 



6. Vergic sac opened to show verge and canal in gland. 



7. Retractor muscles in tyjjical specimen. 



8. End of verge showing i)enial appendage. 



9. Albumen gland. 



10. Portion of head .showing jiseudobranch, pneumcstome, and rectum with ridge. 



11. Penial complex opened to show position of jienial gland, verge, pilasters, etc. 



Penial appendage is retracted. 



12. Penial complex from outside showing muscles. 



13. Genitalia dissected and organs separated, showing particularly the form of jirostate 



and its junction with the vas deferens and sperm duct. 



Line near figure indicates 1 nmi. in length. Line at right of fig. 1 is also for 

 fig. 2. Line at left of fig. 6 represents 0.5 mm. in length. 



