EXPLANATION OF PLATE 6. 



The figures (with the exception of fig. 19) are tracings from photo- 

 micrographs. Fig. I shows the normal radula of Neptunea antiqua, 

 and fig. 14 that of Volutopsis norvegiciis respectively. The rest are 

 varieties. 



Figs. I to 13. — Neptunea antiqua. 

 Figs. 14 to t6. — Volutopsis norvegicus. 

 Figs. 17 to 19. — Buccinofusus berniciensis. 



