Noble Pen Shell

The bivalve shell is usually 30–50 cm (12–20 in) long, but can reach 120 cm (4 ft). Its shape differs depending on the region it inhabits. Like all pen shells, it is relatively fragile to pollution and shell damage. It attaches itself to rocks using a strong byssus composed of many silk-like threads which used to be made into cloth. The animal secretes these fibres from its byssus gland; they consist of keratin and other proteins and may be as long as 6 cm (2+1⁄2 in). The inside of the shell is lined with brilliant mother-of-pearl.

This species is endemic to the Mediterranean Sea, where it lives offshore at depths ranging between 0.5 and 60 m (2 and 200 ft). It could be found buried beneath soft-sediment areas (fine sand, mud, often anoxic).

This species is the origin of sea silk, which was made from the byssus of the animal.