Pinna nobilis
Ccommon name the "noble pen shell" or "fan mussel" is a species of large salt-water clam, a marine bivalve mollusc in the family Pinnidae, the pen shells. It reaches up to 120 cm of shell length. The bivalve shell is usually 91 cm (3 feet) long, and its shape differs depending on the region it enhabitates. 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. These keratin fibres that the animal secretes by byssus gland are even 6 cm long. The inside of the shell is lined with brilliant mother-of-pearl.