28 



Charles Zeleny. 



Fig. 8 

 ^-Ditrupa subulata, showing single naked stalked operculum ia line with branchix of left side. 

 Dorsal view. Note indication of basal suture ( X 15)- B, C-Side view and dorsal view of operculum 

 of Pomatoceros triquetroides, showing highly modified terminal and lateral spines. Basal suture 

 present (X 10). Z)— Operculum of Vermilia multivaricosa, showing curved stalk and absence of a basal 

 suture. Dorsal view — Left-handed individual ( X 8). 



