The Pacific or Japanese Oyster is an introduced species normally confined to oyster farms, but can sometimes be found on beaches of south-west Wales and England, especially after stormy weather. It can grow up to 7" in length and is coloured mostly greys, whites and yellows with rough concentric ridges and a crenulate margin. The left valve is deeply concave; the right valve fits inside the left and is almost flat. The inside of both halves is white, with a dark purple-brown adductor scar.
Found at Angle Bay, Pembrokeshire