Surely one of the most beautiful British marine molluscs, the living Necklace or Moon Shell, Polinices catenus (da Costa), is shown here washed up on the sands of Rhossili Bay, Gower, South Wales.
This gastropod is a carnivorous predator that inhabits the lower shore. It often ploughs a furrow in the wet surface sediments at low tide level as it travels around on incoming tides, searching for small bivalved molluscs on which to feed. It drills through the shell of its prey making a neat circular hole through which it can eat the flesh. The hole is almost invariably drilled near the umbo or hinge area of the valve. It particularly likes to eat Thin Tellins (Angulus tenuis), Banded Wedge Shells (Donax vittatus) and young specimens of Striped Venus Shells (Chamelea gallina).
The photograph below shows the other side of the same living Necklace Shell. The brown chitinous operculum (lid) is visible in the shell opening or mouth where the animal has withdrawn into the cavity of the shell and sealed itself safely inside.
This species of gastropod mollusc derives its name from the shape of the egg masses that it lays. These look a bit like a torque type of necklace – a broad open curved band of eggs.
Revision of a post first published 15 May 2011
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