Il8 MADRAS FISHERIES BULLETIN VOL. XIV, 



has a half-cup shape whence has come the popular name. Ihese 

 small shells are not uncommon in fairly shallow water; on hard 

 bottom they usually adhere to stones, where it is muddy to any 

 shells that manage to exist there, particularly to the Window-pane 

 oyster {Placuna). The exterior of the shell is rough and irregular 

 and always white, in marked contrast to the pale-yellow tint of the 

 body within. 



The form of the SLIPPER LIMPETS {Crcpidiihi) is well express- 

 ed by the name— a long oval, much flattened, and with a shelf-like 

 projection within, across the posterior half, exactly like the toe-end 

 of a slipper. They show a remarkable resemblance in the 

 shape of the shell to Navicdla, the fresh water Nerite ; the internal 

 ledge is however not the remains of the lip of the columella, but a 

 purchase for the attachment of the adductor muscles. Under 

 favourable conditions slipper-limpets may increase so prodigi- 

 ously as to become a danger to the prosperity of the oyster 

 industry. An example of this is the damage done within the last 

 few years to valuable oyster beds on the east coast of England by 

 the American Slipper-limpet {Crepidula foniiratd), imported 

 inadvertantly with a consignment of oysters from the United 

 States. The intruder found conditions so favourable that now a 

 dredge sometimes brings up as many slipper-limpets as oysters, 

 and their consumption of the available food is so great that the 

 oysters, which live on the same organisms ?s the limpets, have 

 insufficient food and do not fatten and thrive as they should. 

 During the war, the plague of slipper-limpets became so alarming 

 that the Fisheries Department in England, after investigation, 

 arranged for the oyster fishermen to be paid for all slipper-limpets 

 collected, and these were then turned into meal and shell-grit for 

 use on poultry farms. 



The Naticidac are active sand-burrowing animals. In Natica 

 proper the shell is strong and handsome and highly polished, 

 usually almost globular, but in some cases with the mouth whorl so 

 expanded as to appear roughly ear-shaped The whorls are few, 

 the spire small and obtuse. The columella is often much thickened. 

 They are predaceous in habit, and exceedingly voracious. The 

 foot is enormously enlarged and has developed a system of water 

 canals that enables it to burrow with remarkable celerity — a most 

 ingenious device. Lobes of the foot rise over the shell before and 



