Eccentric sand dollar

The Eccentric sand dollar is basically a flattened sea urchin that burrows in the sand. The average size is 76 mm wide with a dome shape. They are colored gray, brown, black or shades of purple. The underside is covered with tiny spines (pics 1 and 2) and like most sand dollars, are filter feeders, and they use the small spines that cover their bodies to snag crustacean larva, plankton, and other tiny prey. The food is slowly passed from spine to spine until it reaches mouth at the middle of the bottom side of the body. The spines are also used for locomotion, along with a series of tube feet, so called because they are operated by a hydraulic system controlled by the main body. When eccentric sand dollars move, they lay flat on the bottom with the mouth side facing down. The tube feet are also utilized for obtaining oxygen from the environment.