This is a large species of clam, endemic of the Mediterranean sea (it can only be found here), which can reach up to 120cm (4ft) of shell length, although it is usually 30-50cm (1-1,6ft) long. It usually lives in areas with Neptune's seagrass meadows, at depths between 0,5 and 60m.
The Pinna nobilis has a symbiotic relation with a little crayfish often found living inside the shell. The little crayfish pinches the mussel when spotting danger. When pinched the mussel closes its shell.
The inside of the shell is lined with brilliant mother-of-pearl, which already romans used to make buttons. The collection of individuals for food and craftwork, plus its special fragility to pollution and shell damage, has made it an endangered species. It is currently been affected by an invasive organism, which is quickly ending with its populations in the Western Mediterranean.