XV. — SHELLS OF OYSTERS KILLED BY PURPURA. 

 Note the round, clean-edged hole that Is bored in the shell. This is done 

 by the rasping "tongue" of the borer, and the work of hours of steady boring. 

 Through this hole the snail pours out digective fluids which kill the oyster. 

 Only a very small portion of the oyster is eaten, but if there are other borers 

 within "smelling" distance, they will be attracted, and so a single oyster may 

 serve for a meal to several snails. 



