False cowries are a family of snails which live on, and prey on corals, particularly soft corals and sea fans.
These snails are sometimes considered external parasites, as they can attach themselves to soft corals with their molluscan foot, and then slowly devour the coral polyps.
These snails have smooth shiny shells with a long opening which can be shaped like a pear, an egg, cylinder or lance. The shell is often plain white, but can also be reddish or pink. The false cowrie shell is almost completely covered with a colourful mantle (from the latin 'robe' or 'cloak') which secretes the calcium carbonate required for shell growth.
False cowrie mantles can often adopt the colour and pattern of the 'host' coral which they are eating. This provides an excellent camouflage for the snail.