• Norwegian: reirskjell


The mantle margin bears a large number of red or orange, contractile tentacles. The shell itself is off-white and is usually no more than 2.5 cm long (occasionally 4 cm). It has approximately 50 fine ribs radiating towards the margin. The shell gaps on both sides (unable to close the shells). When disturbed it moves quickly, by expelling jets of water by 'clapping' its shells together, combined with running motions with the tentacles. It builds nests from byssus threads.


It is often found hiding under rocks or in crevices in coarse sand or gravel, from the subtidal zone and down to a depth of 700 meters.


The gaping file shell is registered in the northern North Sea, as far north as Lofoten, Norway. The southernmost registrations are from the Mediterranean and the Canary Islands.