One of my favorite pastimes here in Mexico’s Sea of Cortez is exploring the vacant fisherman’s camps that dot the bays and islands. Each camp belongs to a particular angler and his family and friends, and is used as a place to eat and sleep during extended fishing expeditions.

Some camps are simple stone windbreaks with fire pits, and others include wooden huts containing cooking gear and mattresses. All, though, have one feature in common: Each camp contains years’ worth of shells and skeletons from the marine animals the anglers either ate in the camp or caught and cleaned for market. And depending on the areas’ species and the fisherman’s tastes, each pile is different.

These castoffs are trash to camp owners, but they’re treasures to me and last week I found a king’s jewels. Lying on the sand, along the waterline and in a nearby camp’s recent kitchen midden, were countless magnificent round shells, their central interiors pearly white and their exteriors and fluted edges shades of pink, purple and orange. Down the shells’ curved backs ran fingerlike ridges, each bearing knobs that looked like knuckles. The largest of these thick shells were bigger than my outspread hand.

These gems of the sea, which for an hour I washed, examined and admired, are scallop shells called, appropriately, lion’s paws.

About 360 scallop species inhabit the world’s tropical and temperate waters, ranging in size from a quarter-inch wide to 11 inches wide. One of my two shell field guides says that the lion’s paw scallop grows up to 4 inches wide; the other book says 6 inches. If that’s so, the shells I found were giants of their kind, plausible here in the nutrient-rich Sea of Cortez (Gulf of California). My lion’s paws were 6 1/2 inches wide, 6 inches long and as heavy as old-time glass ashtrays.

The animals that create these shells are as remarkable as their exteriors. Scallops are among the few bivalves that live free on the surface of sand, mud or rubble, un- attached in most cases to anything on the ocean floor. These bivalves are also among the few that can swim. The rear muscle that other bivalves use to shut their shells tight is located in the center in scallops. We know this round muscle as the seafood delicacy, the scallops of the dinner plate.

By clapping its valves shut with its central muscle, the scallop ejects water from its interior cavity through the shells’ liplike edges, one stream from each side of the muscle. The two-sided jet propulsion allows the animal to leap, or swim, up to three feet per puff.

Some scallops use their water jets to blow a depression in the sand where they settle down, from 1 foot deep to more than 1,000 feet, depending on the species. Most scallops, though, use their swimming ability to escape their main predator, starfish.

Scallops know a starfish is approaching because embedded in the flesh between the two shells are 30 to 40 eyes that can detect shadows and movement. Along with the eyes, which can be blue, red, gold or other colors, are tentacles so sensitive that if just one starfish tube foot touches it, the scallop leaps away.

Such jetting isn’t foolproof. Sometimes the scallop jumps straight up, landing right on top of the starfish it’s trying to avoid.

Throughout history, painters, designers and collectors have been inspired by the elegant shape and structure of the fan-shaped scallop shells. Botticelli stood Venus on a scallop shell in his painting "The Birth of Venus." We boomers grew up associating a bright yellow scallop shape with the Shell Oil Co. And now I am the owner of a stunning collection of lion’s paw shells.

I planned on keeping only two or three, but when the friendly fish camp owner returned and saw me dithering over the mind-boggling choices, he said, "You like? Take! Take!"

Thank heaven Christmas is coming.

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Susan Scott can be reached at www.susanscott.net.