^ 





J 



s 



I Grooved Top-shell ; 2 Small Pearly Top ;■ 3 Swollen Top ; 4 Common Top 



5 Grey Top ; 6 Flat Top ; 7 Thick Top ; 10 Many-grained Top ; 



8, 9 Pheasant-shell; ii, 12 Freshwater Nerite. 



