Pinnidae

The Pinnidae are a taxonomic family of large saltwater clams sometimes known as pen shells. They are marine bivalve molluscs in the order Pteriida. The shells of bivalves in this family are fragile and have a long and triangular shape, and in life the pointed end is anchored in sediment using a byssus. The shells have a thin but highly iridescent inner layer of nacre in the part of the shell near the umbos (the pointed end). The family Pinnidae includes the fan shell, Atrina fragilis, and Pinna nobilis, the source of sea silk. Some species are also fished for their food value. As Rosewater commented in 1961: