Fi". 1. Operculum of Turbo fluctuates; 

 a, outside. 



Pig. 2. Operculum of Imperator olivaceus; 

 b, outside ; e, inside. 



Kg. S. Ceritliium telescopium } 

 , longitudinal section. 



Kg. 6. Marpinella glabella, 

 longitudinal section. 



Fig. 7. Cypra?a Turdus, 

 transverse section. 



Fig. 3. Operculum of Turbo Sarmaticus— b, exterior surface ; a, interior surface. 

 OPERCULA AND SECTIONS OP SPIRAL SHELLS. 



