Padilla Bay National Estuarine Research Reserve. The Mud Snail, Batillaria
attramentaria, is abundant on soft mud or high intertidal zones of quiet bays
and estuaries from Boundary Bay, British Columbia, to Elkhorn Slough, California
. The shell is long, slender, and about 35mm long. It was introduced from
Japan to the U.S. and is common where Japanese oysters were planted.