I'VE BOUGHT MANY CYPRAEA FROM THE PHILIPPINES THAT HAVE FOREIGN GROWTHS RANGING FROM CORAL(ALSO BLACK CORAL), BIVALVES, BARNACLES, CREPIDULA, OR SPONGE. ALWAYS THE MARGINAL LINE(WHERE THE 2 MANTLES MEET)IS DISTORTED. I BELIEVE NATURAL PREDATORS DAMAGE THE MANTLE THAT CAUSES THE IRREGULAR MARGINAL LINE. THIS CAUSES SURFACE AREAS OF THE CYPRAEA TO BE OPEN TO FOREIGN GROWTH & IRREGULAR CALCIFYING. ALOHA ALL! CHRIS:) c",)