Moon Snail Egg Casing

Moon snails lay their eggs in special cases called sand collars. These collars look like round rings made of sand and can often be found on the seafloor. The snail uses the sand around her to build the collar, making it strong enough to hold many eggs safely inside.

The eggs stay hidden in the sand collar until they are ready to hatch. After this, the collar breaks apart and disappears, leaving no sign behind. Most sand collars are already empty, because the eggs have hatched or have been eaten, so it is rare to find one still filled with eggs.