The razor shell, officially called Ensis Ensis (latin for sword sword) is a common burrowing mollusk containing two parallel and elongated fragile valves. They open or shut by an elastic ligament. Ensis is found
at sandy beaches off the coasts of northwest Europe. Its taxonomy is still a matter of debate: whether it belongs to the bivalve moluscs family of Pharidae or Solenidae. Related species (or synonyms) are E. directus, E. magnus,
E. minor ans E. siliqua . Some of these species may differ in size and geographical location.
You can often find empty razor shells on our beaches at low tide, the two shells often still connected with their hinges. The adult shell can become 10 cm in length. Most of the time it is hidden under sand, with its two siphons, two parallel tubes at the upward side of the shell. One opening is used to take in water and other opening to expel the water. The bottom side of the shell (its foot) contains a long muscle used for digging into the sand (see picture, upper part: c and d at left =siphon, b in midde =shell, a at right=foot)
At high tide the razor shell comes out from the sand and filter feeds, but at low tide it burrows into sand for safety. This is a reason why they are not often seen alive. With their gills they filter out phytoplankton from the seawater. Like other bivalves they also collect heavy metals and other pollutants that build up in their tissues. The reason why they are often used for measuring the degree of pollution in certain areas. A razor shell can bury itself rapidly in the bottom when needed, by taking a vertical position and using its ‘tail’ muscle to dig in. see: https://www.facebook.com/staatsbosbeheerwadden/videos/1020223211366825/
At low tide, a keyhole-shaped depression in the sand is often the only visible sign that the bivalve is present (see picture, lower part)
Cosel, R. von, 2009. The razor shells of the eastern Atlantic, part 2. Pharidae II: the genus Ensis Schumacher, 1817 (Bivalvia, Solenoidea). Basteria, 73: 9-56