Sand dollars are flat, round marine animals related to sea urchins and sea stars, not actual shells or “sand coins.” They live just under or on top of sandy seafloors in shallow coastal waters around the world.

What is a sand dollar?

  • A sand dollar is an echinoderm, the same group as sea urchins, sea cucumbers, and sea stars.
  • The “shell” people find on the beach is the hard skeleton, called a test , usually bleached white by the sun and surf.
  • When alive, sand dollars are covered with tiny moving spines and hairs (cilia) and are usually gray, brown, or purple rather than white.

How they look and live

  • Size: Most sand dollars are about 2–4 inches (3–10 cm) across, with a thin, disk-like body.
  • Pattern: The familiar “flower” or star shape on top is formed by five petal-like regions of pores used for gas exchange and moving water.
  • Habitat: They prefer sandy or muddy bottoms just below the low-tide line, often half-buried for protection.
  • Range: Different species occur in temperate and tropical seas along many continental coasts, including North America and the Caribbean.

How sand dollars move and eat

  • Movement: Sand dollars use their tiny spines and tube feet, along with water flowing through their pores, to slowly crawl or burrow through the sand.
  • Feeding: They are mostly deposit feeders, picking up tiny bits of organic matter, algae, and detritus from the sand and water.
  • Mouth and teeth: On the underside is a small central mouth with a structure called “Aristotle’s lantern,” containing five tooth-like elements used to grind food.

Life cycle and predators

  • Reproduction: Many sand dollar species reproduce by broadcast spawning, releasing eggs and sperm into the water, often seasonally (for some species, late fall to early winter).
  • Young: Larvae are planktonic, drifting in the water before settling and transforming into the flat adult form on the seafloor.
  • Predators: Fish such as cod, flounder, sheepshead, and haddock can crush and eat sand dollars despite their tough tests.

Beach finds, value, and ethics

  • Beach finds: A smooth, bright white, lightweight test with no velvety covering is almost always a dead sand dollar skeleton, safe to collect where local rules allow.
  • Live individuals feel velvety, are darker in color, and may leave a faint yellowish mark on your hand; these should be gently returned to the water.
  • Monetary value: Because they are common, cleaned sand dollar tests in gift shops typically sell for about 1–5 dollars each, with larger ones costing more.

Information gathered from public forums or data available on the internet and portrayed here.