ILLUSTRATIONS. 



Frontispiece. Page. 

 Summary of census of Michigan Terrestrial MoUusca, showing number of 



species reported from each (Jounty .* 427 



Fig. 1. Diagram showing parts of a shell and method of measurement 458 



2. Genitalia of Polygyra albolabris • 460 



3. Animal of Polygyra albolabris 460 



4. Jaw of Polygyra albolabris 461 



5. Dentition of Polygyra albolabris 461 



6. Polygyra tridentata 462 



7. Polygyra fraudulenta 462 



8. Polygyra inflecta 463 



9. Polygyra profunda 463 



10. Polygyra sayana 464 



11. Polygyra albolabris 464 



12. Polygyra albolabris dentata 465 



13. Polygyra albolabris maritima 465 



14. Polygyra zaleta. 466 



15. Polygyra multilineata 466 



16. Polygyra palliata 467 



17. Polygyra elevata 468 



18. Polygyra pennsylvanica 468 



19. Polygyra thyroides 468 



20. Polygyra clausa 469 



21. Polygyra mitchelliana 469 



22. Polygyra hirsuta 470 



23. Polygyra fraterna 470 



24. Polygyra monodon 471 



25. Animal of Circinaria concava 472 



26. Jaw of Circinaria concava 472 



27. Dentition of Circinaria concava 472 



28. Circinaria concava 472 



29. Animal of Omphalina fuliginosa 474 



30. Jaw of Omphalina fuliginosa 474 



31. Dentition of Omphalina fuliginosa 474 



32. Omphalina fuliginosa 474 



33. Omphalina inornata 475 



34. Animal of Vitrina 475 



35. Jaw of Vitrina limpida 475 



36. Dentition of Vitrina limpida 476 



37. Vitrina limpida 476 



38. Animal of Vitrea cellaria. 476 



39. Jaw of Vitrea cellaria 476 



40. Dentition of Vitrea cellaria • 476 



41. Vitrea cellaria 477 



42. Vitrea hammonis 477 



43. Vitrea wheatleyi 478 



44. Vitrea binneyana 479 



45. Jaw of Vitrea ferrea 479 



46. Dentition of Vitrea ferrea 479 



47. Vitrea ferrea 479 



48. Vitrea indentata 480 



49. Vitrea rhoadsi ". 480 



50. Vitrea multidentata 481 



