Teredo navalis

Linné, 1758

Description (shell):
Shell thin and fragile. Anterior lobe triangular, with fine horizontal ridges; anterior disc with fine vertical to oblique ridges; median disc narrow, concave, with concentric sculpture; posterior disc with fine concentric lines; auricle semi-elliptical, almost as large as anterior lobe. Both valves strongly convex. Umbonal reflection closely applied to umbo; posterior hinge line broad, concave, with a bounding ridge. Junction of auricle with posterior disc visible as a ridge on the inner surface, median disc generally indistinct. Apophysis long, curved, slender, and rod-like, extending two-thirds of the depth of the shell. A knoblike condyle below the umbone and another on the opposite, ventral, border. Pallet blade elliptical with a concave edge, handle short, cylindrical, not extending on to blade (T. navalis-detail).

Up to 10 mm long.

White, periostracum light brown. Inner surfaces white.

Worm-like animal with enormously developed siphons. For the protection of the body a chalky tube is secreted. At the mouth of the tube, the animal has developed a pair of accessory valves - pallets - the handles of which are attached to the body. The oval blades of the pallets serve to close up the tube when the siphons have been withdrawn.

The borings are frequently found in drifted, waterlogged wood, each lined with a thin tubular, calcareous deposit (T. navalis-borings).

Widespread around the world (Distr. T. navalis).