The Moon Snail Mystery

Moon snail, photographed at Old Garden Beach, Rockport, Mass.

FOR A LONG TIME, DURING MY NEW ENGLAND DIVING DAYS, the northern moon snail (Euspira heros) represented a mystery to me. I kept seeing these structures I knew were moon snail “sand collars,” mucus-bound masses of sand that were said be be egg-laden. Except that there didn’t appear to be any eggs.


An apparently eggless moon snail sand collar, crab not normally included. 


Then, one day, I found this:

moon snail sand collars
The culprits gobbling up the eggs in this moon snail sand collar look to me like Atlantic oyster drill snails, except that according to excellent “Marine Life of the North Atlantic” guide, they’re supposed to be on hard surfaces like oyster beds and rocks, not on sandy bottoms. Perhaps the scent of an easy meal draws them out onto the sand, albeit at a snail’s pace. 


Thinking about moon snails brings to mind the theme from “Butch Cassidy” in which the singer compares himself to “the guy whose feet are too big for his bed.” The scientific name for Moon Snails ought to be something funny like “Gastropodia Gigantis,” since their big feet are, in fact, too big for their shells. Actually, they’re named Euspira heros.

It would be tempting to work into a fake name something about being disgusting, but, at bottom, they’re just snails. Big ones. “Marine Life of the North Atlantic”  says they grow up to five inches, but I’d swear I I’ve seen bigger ones. But, then, things are magnified underwater.


Northern moon snails are pretty common, found mostly on muddy and sandy bottoms in a range stretching from the Gulf of St. Lawrence to North Carolina. Their big feet help them scrounge underneath the sand to search out clams and other mollusks.

They use their snailish radulas to drill into their prey’s shells, dispense digestive enzymes and suck out the liquified tissues inside. “Marine Life” says its common to see their feet completely covering the victim as they feed.


While it’s not unusual to encounter northern moon snails – or at least moon snail sand collars – in New England diving, worldwide there are in fact some 270 species of moon snails in the gastropod family Naticidae. In contrast to the northern moon snail, some are actually striking in appearance.  

PRINCIPAL SOURCES:Marine Life of the North Atlantic,” Andrew Martinez; “Euspira heros,” Wikipedia; “Naticidae,” Wikipedia.