MUSEUM OF COMPARATIVE ZOOLOGY. 47 
EXPLANATION OF THE PLATES. 
PLATE I. 
Fig. 1. Mesodon armigerus. 
“* 2. Same : epidermis enlarged. 
** 38. 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 Cantiana. 
** 14, Polygyrella polygyrella. 
“* 15. Triodopsis Levettei. 
** 16. Mesodon ptychophorus. 
** 17. Triodopsis Hemphilli. 
PLATE II. 
. Patula Idahoensis. 
Patula strigosa, var. albofasciata. ¢ 
Patula strigosa, var. albofasciata : toothed. 
Patula strigosa, var. Gouldi. 
Patula strigosa, var. multicostata. 
Patula strigosa, var. Wasatchensis. 
Patula strigosa, var. Newcombi. 
Patula strigosa, var. Gabbiana. 
Patula strigosa, var. 
Patula strigosa, var. castanea. 
“12. Patula strigosa, var. Oquirrhensis. 
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“18.  Patula strigosa, var. Binneyi. 
“* 14. Patula strigosa, var. castanea. 
“* 15. Patula strigosa, var. Hemphilli. 
“16. Patula strigosa, var. Gouldi. 
