What Is Inside a Sand Dollar?

The "Doves of Peace" Inside a Sand Dollar

Doves of peace from inside a sand dollar
 Saylah Rossman/90269147@N03/Flickr/CC BY 2.0

Have you ever walked along the beach and found a sand dollar shell? This shell is actually called a test and is the endoskeleton of the animal. It is what is left behind after the sand dollar dies and its velvety spines fall off. The test may be white or grayish in color and has a star-shaped marking in its center.

If you pick up the test and shake it gently, you may hear rattling inside. What is inside?

What you hear are the remnants of the sand dollar's amazing eating apparatus. The sand dollar has five jaws with 50 calcified skeletal elements and 60 muscles. They extrude them to eat, scraping algae off rocks and other surfaces and biting and chewing prey. They can then retract them into the body. The sand dollar dries up after death and inside you will hear these jaw remnants when you shake it gently.

The Legend of the Sand Dollar

Visit a shell shop and you may find poems or plaques illustrating the Legend of the Sand Dollar, often with a sand dollar to accompany them. The author of the poem is apparently unknown. But one part of it says, 

Now break the centre open
And here you will release
The five white doves awaiting
To spread Good Will and Peace.

Christian authors have written many variations, likening different markings on the sand dollar to the Easter lily, Star of Bethlehem, poinsettia, and the five wounds of the crucifixion.

This sort of interpretation can turn the discovery of a sand dollar on the beach into a moment of religious reflection.

The Doves of Peace of Aristotle's Lantern

The five white "doves" are parts of the sand dollar's mouth. The mouth of a sand dollar and other urchins is called the Aristotle's lantern.

This apparatus was described by Greek philosopher and scientist Aristotle, who said it resembled a horn lantern, which was a five-sided lantern made of thin pieces of horn.

The five parts of the Aristotle's lantern are the five jaws of the sand dollar, including the calcium plates that serve as skeletal elements, plus muscles and connective tissue. Their shape can remind you of a dove, especially due to the dove gray or white color of the dried shell.

When a sand dollar dies and dries up, the Aristotle's lantern may break up into the five "doves" of legend, and create that rattling sound you hear when you shake a sand dollar test.

Now that you know what they are, you are still free to find inspiration in the science or the mythology handed down by a Greek philosopher and Christian metaphor.

Sources and Further Information