One of the first rules of collecting on the beach is to make sure when you take something home, you’re not taking anything that’s still alive. You should always make sure there’s not something still making a home in any shells you collect, make sure barnacles aren’t still living when you head home, and make sure you don’t take any live sand dollars.
Sand dollar is the common name for sea urchins in the order Clypeasteroida, who are relatively flat and burrow in the sand. It’s actually really easy to tell if a sand dollar is alive or if what you’ve found is just its “test,” or bony skeleton.
When sand dollars are alive, they are covered with a coating of cilia, small hairlike feet that help the sand dollar move and bury itself in the sand. These tiny spines move when the animal is still alive, so if you hold a sand dollar in your hand and feel the spines moving, it is living. The spines also give the sand dollar a dark color ranging from brown to grey to purple and red. Finally, some sand dollars will leave a yellowish stain on your hands if you hold a live specimen. This harmless substance called echinochrome is another sign that you should return the critter to the water.
Sand dollars can’t survive out of the water, so if you find a live one, put it gently back in the water. If you find a sand dollar on the beach, it is probably no longer alive and it is ok to take. Even sand dollars that look grey or tan in color are dead if they have no tiny coating of furry spines on them. And, if you find one that is rock-hard and unbreakable, you’re lucky enough to have found a sand dollar fossil, which is a sand dollar that is definitely dead!
This article appeared in the Beachcombing Magazine May/June 2019 issue.