Sand dollars, like their close relatives the sea urchins, are found on sandflats from the low intertidal to about 30 feet, from Alaska to Baja California. Adapted for a lifestyle of burrowing in sand, sand dollars use their many spines to drive themselves into the sand. When burrowing is done, they position themselves at an angle with their posterior ends projecting above the sand surface. Cruising across the sand surface is accomplished by the spines on the lower surface which operate in waves. In rough waters, these animals lie flat on the surface of the sand.
When it comes to eating, sand dollars may be likened to feeding factories as they engage an assembly line of hundreds of tiny appendages in their food processing system. Spines, tube feet and pedicellaria (tiny pincers) on both sides of the body help in the complex capture, transport and sorting of food items. Tiny whiplike cilia on the surface of the sand dollar sweep the very small, immobile particles. Larger immobile particles are collected by tube feet. A five-toothed apparatus called Aristotle's lantern chews up the food.
Sand dollars release sperm and eggs into the water from about May through July in Southern California. Sand dollars reach a diameter of about 75 mm and have a life span of about 8 years. Predators include California sheephead, starry flounder, spiny sand star and pink star. Sand dollars avoid approaching pink stars by burrowing down.
Sand dollars are usually found at the Aquarium in tank number 23.