In addition to sea urchins, the Class Echinoidea contains the sand dollars, which have flattened bodies. Sand dollars are usually found on soft bottoms, burrowing through sand in search of food. It commonly reaches a size of 75 mm in diameter. Although the common conception of the Sand Dollar is the smooth white empty body, known as the test, which washes ashore on North American coasts, the living animal varies in color from pale grayish lavender to a dark purplish black.