(Atrina zelandica).
This large but rather thin and fragile shell, like a half-closed fan, grows to a foot or 18 in. in length. The shell is purplish-black with a metallic lustre and is studded with light-brown, sharp, hollow spines. This shellfish lives at and below low tide, almost completely buried, point downward in mud. Occasionally it has purplish-black pearls.
by Arthur William Baden Powell, Assistant Director, Auckland Institute and Museum.