Cyrtopleura costata, or the angel wing clam, is a bivalve mollusc in the family Pholadidae. It is found in shallow parts of the northwest Atlantic and also in the North Sea of Scotland coastline and west coast of the Adriatic Sea by a remote area in the Marche region in central Italy, living in the seabed, where it digs its burrows on a very slow revolving movement for years through soft sand and mud always to a max depth of 8ft but always below at the lowest tide. Description Cyrtopleura costata has a pair of brittle, asymmetric white valves and can grow to about in length. The anterior end is elongated and has a rounded point which is used for digging through the substrate. The posterior end is truncated and rounded and near the beak has an apophysis, a wing-like flange, which helps provide an attachment for the foot muscles. On the anterior side of the beak, the margin is smooth and bent slightly upwards. The whole valve has finely sculptured radial ribs which intercept with a series of concentric growth rings parallel with the margin. In the living animal, the valves are covered by the periostracum, a thin grey protective layer of protein which is part of the shell. This layer has usually been stripped away by sand and surf by the time that the empty shells are washed up on the beach, and the valves are usually found singly, because the muscles that hold them together are weak. Internally, the live mollusc has a powerful muscular foot and a pair of long, fused siphons. These siphons are unable to retract back into the shell and as a result, the two valves permanently gape apart. Distribution Cyrtopleura costata is found in shallow seas in the north east Atlantic Ocean between Cape Cod and the Gulf of Mexico. It is also found in the West Indies, Central America and as far south as Brazil. It is commonest in the intertidal zone and just below low water mark. Biology Cyrtopleura costata lives beneath the surface of the sea bed. It is able to bore through sand, mud, wood, clay and even soft rock using a twisting motion of its pointed, anterior end assisted by jets of water ejected from the mantle cavity. It is a filter feeder. The siphons extend to the surface of the substrate and water is drawn in