MUSEUM OF COMPARATIVE ZOOLOGY. 47 



EXPLANATION OF THE PLATES. 



PLATE I. 



Fig. 1. Mesodon armigerus. 

 " 2. Same : epidermis enlarged. 

 " 3. Mesodon ptychophorus, var. major. 

 " 4. Mesodon labiosus. 

 " 5. Same: epidermis enlarged. 



" 6, 7. Triodopsis Harfordiana. 

 " 8. Mesodon armigerus. 

 " 9. Triodopsis Sanburni. 

 " 10. Patula solitaria. 

 " 11. Triodopsis Mullani. 

 " 12. Polygyrella polygyrella. 

 " 13. Fruticicola Cautiana. 

 " 14. Polygyrella polygyrella. 

 " 15. Triodopsis Levettei. 

 " 16. Mesodon ptychophorus. 

 " 17. Triodopsis Hemphilli. 



PLATE II. 



Fig. 1, 2. Patula Idahoensis. 



" 3. Patula strigosa, var. albofasciata. 



" 4. Patula strigosa, var. albofasciata : toothed. 



" 5. Patula strigosa, var. Gouldi. 



" 6. Patula strigosa, var. multicostata. 



" 7. Patula strigosa, var. Wasatchensis. 



" 8. Patula strigosa, var. Newcombi. 



" 9. Patula strigosa, var. Gabbiana. 



" 10. Patula strigosa, var. 



" 11. Patula strigosa, var. castanea. 



" 12. Patula strigosa, var. Oquirrhensis. 



" 13. Patula strigosa, var. Binneyi. 



" 14. Patula strigosa, var. castanea. 



" 15. Patula strigosa, var. Hemphilli. 



" 16. Patula strigosa, var. Gouldi. 



