Have you ever taken a walk along the beach to collect shells and found a gray, flat disk about 3 inches wide? If so, chances are what you found was the “shell” of a small animal known as a sand dollar that had been washed up by the tide.
Of course, the sand dollar looked much different when it was alive than it did when you found it. sand dollars live in shallow coastal waters.
A living sand dollar’s body is covered with many tiny spines that form a purplish, furlike cover. By means of its spines, it pushes itself through the sand.
The sand dollar’s mouth is a small hole in the center of its flat underside. It swallows sand and digests the tiny bits of food contained in it.
The spines drop off when the animal dies.
Not all sand dollars are round. Some may contain slits, or even be notched. The notched ones are often called “arrowhead” sand dollars. – Dick Rogers