During one of the scuba diving we met the Pinna nobilis, common name the noble pen shell or fan mussel, is a large species of Mediterranean clam, a marine bivalve mollusc in the family Pinnidae, the pen shells. It reaches up to 100 cm of shell length.
The bivalve shell is usually 30–50 cm long, but can reach 100 cm. Its shape differs depending on the region it inhabits. It attaches itself to rocks using a strong byssus. These keratin fibres that the animal secretes by its byssus gland can be up to 6 cm long. The inside of the shell is lined with brilliant mother-of-pearl.
This species is endemic to the Mediterranean, where it lives offshore at depths ranging between 0.5 and 40 m. It could be found buried beneath soft-sediment areas.