Explanation of Plate VI. 



Fig. 1. Polygyra albolabris (Say) Pils. 



2. Polygyra exoleta (Binn.) Pils. 



3. Polygyra profunda (Say) Pils. 



4. Polygyra elevata (Say) Pils. 



5. Polygyra obstricta (Say) Pils. The upper specimen has 

 lost the parietal tooth. 



6. Polygyra thyroides bucculenta (Gld. ) Pils. The upper 

 specimen without parietal tooth. 



7. Polygyra stenotrema (Fer. ) Pils. 



8. Polygyra monodon fraterna (Say) Pils. 



9. Polygyra monodon (Rack.) Pils. 



10. Polygyra hirsuta (Say) Pils. 



11. Polygyra inflecta (Say) Pils. 



12. Omphalina kopnodes (Binn.) Pils. 

 13". Pyramidula alternata (Say) Pils. 



14. Pyramidula alternata (Say) Pils. 



15. Circinaria concava (Say) Pils. 



16. Succinea ovalis Say. 



17. Gastrodonta ligera (Say) Pils. 



18. Pyramidula perspectiva (Say) Pils. 

 1 ( >. Cochlicopa lubrica (Mull.) 



20. Helicina orbiculata Say. 



21. Vitrea indentata (Say) Pils. 



Two views of each species are given, front and lower surface, ex- 

 cepting in figs. 9 and 19, of each of which only one view is given, and 

 13 and 14 which show three views each. The figures are natural size. 



