Andros Island, Sept. 14 — Don't ever suggest to Paula Mikkelsen that snails are wimpy.

Sitting around late at night playing sea creature charades with the biologists, I have the gall to say: "Can you imagine being killed by a snail? What a lame way to go."

That's all it takes.

"Some snails are real predators!" Paula protests. "They have file-like teeth that they use to bore holes through the shells of other mollusks. Then they suck the other guy out."

The scientists launch into a debate about whether killer snails actually drill holes or secrete an acid that eats through shell, but I drift off, thinking about a tiny, velvety-maroon snail, about a quarter-inch long, with "wings" of pliant tissue that it uses to soar through the sea like a miniature bird.

That snail was one of Paula's "finds of the day." Another was Paula's self-proclaimed favorite: two delicate flame scallops with red gills and white, tendril-like tentacles fanning out from the edges of their shells into the water.

Curator of malacology at the American Museum of Natural History, Paula finally is finding the gastropods (snails), bivalves (clams), octopus and squid she came here for, though she's had to look harder for them than in the Florida Keys, where she does most of her research.

During her first week prowling the Andros reef, she said again and again, "I'm not seeing things that I thought should be here. ... It's weird."

She wasn't prepared to say why that was so, or to concede that the animals weren't here. But she grew more mystified every day.

Now, after several weeks, Paula has glided over much more territory and is busy sorting the hordes every night. "There are plenty of species here — I keep finding new ones all the time," she says. "But not in the same proportions as in the Keys."

"One particular species of snail is everywhere here, from the sand plain to reef crest. It's the snail of Andros. Others aren't very abundant."

That's somewhat strange, given that the reef is slowly turning into an algae garden, and, as Paula says, "mollusks love algae."

Snails make perfect algal grazers, with their hundreds of minute teeth that scrape the algae off of the calcified limestone that forms the reef. Many bivalves, on the other hand, are filter-feeders, sucking seawater in and out through a double siphon, eating microscopic plankton strained through tiny cilia on the gills.

Paula speculates that the very thing mollusks love could be keeping them away: Too much algae and the boring and cementing mollusks that normally coat a reef can't take hold. In clearer areas of the back reef, near a channel that keeps the surrounding waters flushed, Paula is finding more species attached to the rocks.

But overall, the cementing and boring bivalves are scarcer than expected. "There are hardly any around," Paula says. "I don't understand it."

Despite their drastically different looks, mollusks generally share three features. They all have a mantle, a sheet of tissue that surrounds the internal organs. The mantle secretes the second common feature — the shell — which can be external, as in flamingo tongues and tulip snails, or internal, as in a squid. (Some other mollusks, like the octopus and nudibranch, have lost the shell entirely). Third, all mollusks have a muscular foot that motors them around, from the "stomach foot" of a snail to the tentacles of a squid or octopus.

Paula's eyes have been focused largely on the sand and the rocky reef these weeks, so she's often missed seeing the squid that sometimes hover near the divers, curious as children. Their enormous, clear eyes share a physical structure that is nearly identical to our eyes.

I looked up from a sandy patch on the reef one day to find a group of three squid apparently watching me. On my knees, I walked to within three feet of them, where we studied each other for some minutes. I glanced around for Paula, but she was off somewhere collecting her snails, oblivious to the puppy-like creatures above me.

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