Mermaid Money from Around the World

By Sarah Rosenbaum

Urchin in the Ten Thousand Islands, Florida. Sand dollar from Southwest Florida. Sea Star in the Ten Thousand Islands, Florida. Sea urchin tests from the Ten Thousand Islands, Florida.

Imagine you’re walking along the shoreline searching for treasures and up ahead of you something catches your eye. Partially buried in the sand, you can tell it’s sizable enough not to be your average sand clump.

Sea biscuit from the Florida Keys.

So, you march over to investigate, being the curious beachcomber that you are. You rummage your fingers around in the sand hoping it’s not just another piece of garbage.

Finally, the sand falls away to reveal the borders of a beautiful, intact sand dollar! Score! Now the hard part…getting the delicate treasure home in one piece.

Sand dollar from the Ten Thousand Islands, Florida.

When you’re imagining this, what kind of sand dollar do you envision? The classic image of a one-holed sand dollar has been used by coastal marketers, designers, and hobbyists for generations. Something about a round little sea cookie with a beautiful flower imprinted completely by forces of nature has captured the attentions of beachcombers across the globe.

But did you know that in each region of the world, the “sand dollar” looks different? In my recent years of shell swapping, I’ve aimed to collect as many varieties of echinoderms as possible from other places in the world, focusing specifically on what is commonly called a “sand dollar.” I admit this was quite a challenge due to shipping turbulence, as nearly all the sand dollar varieties are quite fragile, no matter their origin.

Echinoderms include spiny-skinned, radial sea creatures such as sea urchins, sea stars, and one of my favorites, sand dollars. However, most people only recognize one design as a traditional “sand dollar.”

Sand dollars from the Oregon Coast.

Maybe the sand dollar you find on your beach is a flat cookie-like shape with no holes in it. Perhaps it’s more puffed up like a ball of dough with asymmetrical round-edged flower petals. Or maybe your version of a sand dollar has several holes in it with pointy flower petals imprinted on it that resemble a hemp leaf.

Sea urchin from the Ten Thousand Islands, Florida. Sea star from the Ten Thousand Islands, Florida. Sea biscuit from the Bahamas (Mary Brink/shutterstock.com)

I admit, the nerd in me is fascinated by the ever so slight and yet distinct differences in these sand dollar cousins. What causes these shape differences? Why do some have more holes than others? What purpose do these creatures serve in their respective ecosystems?

Pansy shell from Mozambique (DorotaSe/Shutterstock.com).

Well let’s start with the basics of what we know.

Sand dollars and their kin are at one point living things. These creatures do not lay eggs, but rather reproduce by spawning in the water when in large groups, creating embryos that eventually grow into baby sand dollars. The “test” or the cookie-like bit that we often find is simply a structural element of the creature that grows with the animal. Early on in its life, a sand dollar will develop tiny, hair-like cilia covering the outside of the test, which allow the animal to move around the sea floor and bury itself in the sand.

Live sand dollar from Southwest Florida. Group of live sand dollars in the ocean (Mitch Cox Photo/Shutterstock.com).

Thanks to the efforts of conservation-minded beachcombers on social media and other platforms, most people have now come to know that the presence of these hair-like feet and the colors of the test can assist in determining whether the animal is still living and should remain in its environment, or if the animal is dead and the treasure can be taken home.

Sand dollar from the Ten Thousand Islands, Florida.

Now what about the holes? To be clear, we’re talking about the slit holes that will show around the flower petals on the sand dollar, not the hole at the center back, which is the anus.

Back sides of sand dollars: California sand dollar. Keyhole arrowhead sand dollar from Mexico. Sand dollar from Mutsu, Japan. Sand dollar from Southwest Florida.

The slit holes are present to allow filtration of water and sand through the body of the creature for food filtration as well as letting currents pass through to prevent the creature from being swept away.

California sand dollar with a barnacle attached to it.

Most sand dollar varieties I’ve investigated prefer to be at least partially buried in the sand. And if you’re a visitor of Florida beaches, you’ll likely have encountered a colony of these critters hiding in the sand beneath your toes. Once they’ve passed away and have shed their hair-like feet, they often wash up to shore to get bleached by the sun.

On occasion, sand dollars have been found with distinct veining still visible. The theory here is that the animal was very recently deceased, and you’re still able to see some of the vein patterns where nutrients would have traveled through the creature. In Florida, I’ve only seen this once or twice; most dead sand dollars are completely bleached to a beige or white by the time we find them.

Sand dollar from the Ten Thousand Islands, Florida.

In the photos in this article, you can see the differences in the shapes of the petals, the arrangement of the petals, and in some cases, the thickness of the sand dollars. All these features appear to be unique to their regions and bodies of water.

I find these differences to be a wonderful reminder that even though we are all created alike in many ways, it is our distinct differences that make the world a beautiful place.

Live sand dollars (Kirk Wester/Shutterstock.com). Dead sand dollar (Serge Skiba/Shutterstock.com).

How to Identify Live Sand Dollars

When sand dollars are alive, they are covered with small hairlike feet that move when the animal is still living. Sand dollars can’t survive out of water, so a sand dollar on the beach with no movement on the surface is no longer alive.

No live shelling: Be sure shells are empty and sand dollars, sea stars, and sea urchins are no longer alive before you bring them home.

All photos by Sarah Rosenbaum except as marked.

Learn more about seashells

Learn more about identifying shells, the history of seashell collecting, great shelling beaches, and the lives of the animals who make the shells we find on the beach. Articles ›

No live shelling: Be sure shells are empty and sand dollars, sea stars, and sea urchins are no longer alive before you bring them home.