White furrow shells are small shellfish which are sometimes found in gigantic amounts. When the circumstances are right, more than 1000 animals live within 1 square meter. In the spring and autumn, many white furrow shells wash ashore along the entire Dutch coast during or after a period of offshore winds. The smooth translucent white shell is thin and fragile. Both halves of the shell are more or less identical. White furrow shells are resistant to pollution.