A Sand Dollar and its five jaws.
The top of a fresh Sand Dollar.
The bottom of a fresh Sand Dollar.
The slot-less Sand Dollars (Echinarachnius parma) found on the coast from Labrador to Maine, and the 5- or 6-slot Keyhole Urchins (Mellita quinquiesperforata) found on the Southeastern coast are both members of the class Echinoidea. Close kin are the spherical Sea Urchins and Heart Urchins. The class Echinoidea, which contains approximately 950 species worldwide, is characterized by the fact that its members all have numerous mobile spines and a hollow test (or skeleton) made up of fused plates. All species have 20 rows of these plates, two for each of the five rows of tube feet and two for each of the five intervening areas, known as the interambulacra. These rows run from aboral to oral pole (meridionally). “Regular” Sea Urchins are nearly spherical, whereas “irregular” Sand Dollars are flattened urchins. Heart Urchins are also “irregular.”
Sand Dollars (people usually refer to the southern Keyhole Urchin as a Sand Dollar, too) are approximately 3-inch, cookie-shaped creatures which live near shore in the sand in crowded beds, lying parallel to the beach.
The nappy “fur” on Dollars varies in color. The northern Sand Dollars are reddish-purple and brownish, while the southern ones are silver-gray, tan, yellowish or greenish-brown.
The Sand Dollar has what looks like the outline of a five-petalled flower on its top (or aboral) side. [Note: The top of the Sand Dollar is the surface which is just a little bit more rounded.] Special tube feet extend from the openings forming the flower shape. These feet are used for gas exchange.
In the center of the “flower” there is a disc called the Madreporite disc. This structure sucks in water used to power the tiny tube feet which stick out on the underside of the Sand Dollar. The feet, equipped with suckers, enable the creature to move about, and/or dig in for defense. The feet are also used like hands to convey food to the mouth (a hole in the center of the underside — which also has a flower-like pattern on the surface).
Inside the mouth are five hard, bird-shaped jaws fit together in a flower-shaped pattern. This structure crushes sand grains and diatoms before they reach the Sand Dollar's stomach.
The creature reproduces by spewing out clouds of eggs or sperm from five pores located around the Madreporite disc on the top side of the test. These eggs and sperm come together thanks to ocean currents. The fertilized eggs develop into swimming larvae which soon metamorphose into Sand Dollars.
Living Sand Dollars may be washed ashore after a storm. These creatures will have their velvety coat. Dead Sand Dollars may also be found on the beach. When the dead animal has been bleached by the sun the surface is smooth and gray or white. If you want to speed the “aging” process, soak dead Sand Dollars overnight in a solution of 1 part bleach to 3 parts water. Then rinse, pat dry, and place outside to dry and lighten more. Don't leave out long or neglect to keep an eye on your treasures — we have found that squirrels love to eat close-cousin, globular Sea Urchins.
Sand Dollars are often used as canvases for paintings. Sand Dollar Christmas tree ornaments are especially popular, paintings of red cardinals being a frequent motif.
There is a pretty story associated with the Sand Dollar: According to the “Legend of the Sand Dollar,” the Sand Dollar (or Holy Ghost Shell) symbolizes the birth, crucifixion, and resurrection of Jesus Christ. The flower on the side of the Sand Dollar resembles an Easter lily, with a five-pointed Star of Bethlehem as its center. On the underside of the shell you can see the outline of the Christmas poinsettia. The five narrow openings, or “lunules,” in the Keyhole Urchin shell represent the five crucifixion wounds inflicted by Roman soldiers to Christ's hands, feet, and side. When the Sand Dollar is broken open, you will find five small white objects (the jaw apparatus) which resemble birds in flight. These birds are called the Doves of Peace and Good Will. Another interpretation of the legend states that these “winged creatures” symbolize the angels who sang to the shepherds on the morning of Christ's birth.