THE MOLLUSC A OF GEORGIAN BAY 109 



SESSIONAL PAPER No. 39b 



E. 7. Shell small, about 5 mm. in length. 

 Family amnicolidae. 



F. 15. Shell globoid or low conic; apex rounded. 



Amnicola limosa. 

 F. 16. Shell low, conic, apex emarginate. 



Amnicola emarginata. 

 F. 17. Shell high conic, apex sharp. 

 Amnicola lustrica. 

 E. 8. Shell large and heavy. Apex usually eroded. 

 Family viviparida. 



Campeloma decisum. 

 D. 8. Umbilicus wide. 

 Family valvatidae. 

 E. 9. Whorls bearing three carinae. 

 Valvata tricarinata. 

 F. 10. Whorls without carinae. 

 Valvata sincera. 

 A. 2. Bivalve shell consisting of two valves, united by a dorsal hinge. 

 B. 3. Shell large, one set of cardinal teeth in each valve. 

 Family unionidae. 

 C. 5. Shell heavy, bearing hinge teeth. 



D. 9. Height behind beaks not greatly in excess of that in front. 

 Genus Lampsilis. 

 E. 11. Rays numerous and narrow. 



Lampsilis luteolis. 

 E. 12. Rays few and broad. 



Lampsilis ventricosus. 

 C. 6. Shell light, no hinge teeth. 

 Genus Anodonta. 

 D. 11. Shell high, no radiating sculpture on posterior part of beak. 



Anodonta grandis. 

 D. 12, Shell low, elongated, radiating sculpture on posterior of beak. 

 Anodontoides ferussacianus. 

 B. 4. Shell small, two sets of cardinal teeth in each valve. 

 Family sphaeridae 

 C. 7. Not trigonal in outline. 

 Genus Sphaerium. 

 D. 13. Beak not calyculate. 



E. 13. Lines of growth regular, coarse. 



F. 19. Shell usually with definite narrow yellow border and rhombic 

 outline. 

 Sphaerium rhomb oideum. 

 F. 20. Shell without definite yellow border and oval in outline. 

 Sphaerium simile. 



