A surf clam found only on the exposed sandy beaches of the South Island and Stewart Island, this species is a close relative of the better-known tuatua of the North Island. Its shell is more elongated and less triangular than the northern tuatua, with a smoother surface and a paler colour. The shell is white or pale grey, sometimes tinged with brown. It lives buried in the sand where waves break, with only its siphon showing. The siphon is a soft, fleshy tube that extends from the clam's shell to the surface of the sand. The clam draws water in through the siphon, filters out the plankton, and expels the waste. The siphon is also the clam's greatest vulnerability. A hungry fish or crab can bite it off, leaving the clam unable to feed. The clam can regenerate a lost siphon, but the process takes time and energy. It is often found washed up on beaches after storms. The waves tear it from its burrow, tumble it in the surf, and deposit it on the high tide line. There it lies, bleached by the sun, until a beachcomber picks it up. The shell is smooth and cool to the touch, a perfect oval in the palm of the hand. Its sweet, juicy flesh is delicious eating, but it is less commonly gathered than its northern relative because it lives in more remote, less populated areas. The South Island's west coast is wild and sparsely populated. The beaches are long, the waves are big, and the towns are few. Gathering southern tuatua requires a willingness to travel and a tolerance for cold water. The reward is a meal of sweet, tender clams, eaten on the beach where they were dug. The southern tuatua is a clam of the wild coast, a taste of the untamed South Island.