Q. I found these small purple shells on the beach after a late summer storm, but I can't find them in my shell books. Can you tell me what they are?

A. The lovely little lavender shells are violet snails (Janthina), sometimes called purple snails or bubble snails. Their "bubble" name derives from the mass of mucous bubbles they produce, which hardens into a plastic-like float that allows them to drift in warm seas worldwide. This drifting lifestyle is called "pelagic."

Violet snails spend their lives floating upside down on the ocean's surface. They feed on zooplankton, copepods, marine insects and jellyfish, including the Portuguese-man-of-war, blue buttons and their favorite jelly, the small by-the-wind-sailor (Velella).

Like many sea-surface drifters, the snails' fragile, paper-thin shells are countershaded. The snails bob beneath their raft of bubbles, with their dark underside facing up and their paler topside facing down. This helps camouflage them from both above and below. When feeding, they emit a purple dye that seems to anesthetize their prey. They will also release the dye if disturbed.

Violet snails don't get very large, reaching a maximum of about two-and-a-half inches in length. Ones found on beaches are usually much smaller.

The state operates three public aquariums; one in Pine Knoll Shores, another at Fort Fisher and a third on Roanoke Island. The aquariums are administered by the North Carolina Department of Environment and Natural Resources, and are designed to inspire appreciation and conservation of North Carolina's aquatic environment.

For more information about the Aquariums, visit www.ncaquariums.com, or call 800-832-FISH.