Scattered along the beaches of both the East and the West Coast, you sometimes see hard, flat discs with a faint five-pointed star pattern on one side. Although they seem like chalk or compacted sand, they are actually the tests, or skeletons, of a type of sea creature called a sand dollar. Shell collectors prize sand dollars for their beauty, but you need to handle them carefully to take one home intact.
The Sand Dollar
Sand dollars live on the sandy or muddy bottoms of shallow ocean water, often in dense colonies. Although they look very different from sea urchins, they're very closely related. Like sea urchins, they are covered with spines, but a sand dollar's spines are soft and fine, giving the appearance of a velvety fur. Sand dollars use their spines to convey tiny particles of food to their mouths located on the underside of their bodies. When predators approach, sand dollars burrow into the sand to escape.
The Search for Sand Dollars
When a sand dollar dies and decays, its test can sometimes wash up onto the ocean shore, especially if there's been a storm the night before. To find a sand dollar's test, therefore, walk along the beach at low tide, paying close attention to the area below the high tide line. Look for round patches or depressions in the sand; these may turn out to be sand dollars on closer inspection. If the test has been on the beach for a long time, it may have bleached to a pale, almost white color, which makes it easier to spot.
Proper Collection of Tests
When collecting sand dollar tests, the most important thing to remember is never to collect a live specimen. Not only is collecting live sand dollars harmful to the local environment, it is illegal in many parts of the United States. If the sand dollar still has its spines and feet, return it to the water. However, if the sand dollar is just a test, gently remove it from the sand using your fingers or a flat implement such as a knife. Store it in a soft container, as the test can be very fragile. A sock makes a surprisingly good wrapping for a sand dollar.
Proper Preservation of Tests
Once you've got the test home, rinse it in water. The water will cloud at first; keep adding fresh water until it's mostly clear. Once you've rinsed the test, soak it for about 15 minutes in a solution of water and 30 % bleach and water, which should whiten the exoskeleton without damaging it. Allow the sand dollar to dry.
Once the test is dry, help prevent future damage by applying a mixture of water and white glue to the surface with a paint brush. Allow each side to dry before painting the other one with the glue mixture. Alternatively, use a spray acrylic varnish or shellac.