The velvet-like skin of live keyhole sand dollars is usually tan, brown, grey or dark green in colour.

Like all sand dollars, they are found in shallow seawater below tide lines, where they burrow into the seabed to obtain food.

Keyhole sand dollars are so named because of the distinctive keyhole-shaped perforation toward the rear of the endoskeleton.

The radial symmetry is characteristic of echinoids generally, including the ancestors of sand dollars.

Sand Dollars Mellita isometra ranges across the East coast of the United States.