Scaphopoda

The Scaphopods or "Tusk shells" are an unusual group of molluscs that are rarely found alive - except by divers or dredging - but often the empty shells are washed up on the shore. The curved shell (shaped like an elephants tusk - hence the colloquial name) is open an both ends and they live buried in sediment with then thinner end of the shell projecting in to the water. Evidence from fossils shows that the group first evolved in the Devonian period - some 400 million years ago. They burrow into the sediment using a muscualr foot very similar to that found in bivalves.