Lewis & Short

pīna, ae, f., = πῖνα (less correctly pinna, = πίννα), the sea-pen, a kind of mussel, Cic. Fin. 3, 19, 63; id. N. D. 2, 48, 123; Plin. 9, 35, 56, § 115; 32, 11, 53, § 150.