A Multitude of Mollusks

Mollusks are among the oldest living organisms, their fossils dating back 600 million years. And to this day, wherever there's water -- fresh or salty -- you'll find at least one of these fascinating Invertebrates. The second largest group in the Animal Kingdom, they come in a wide variety of sizes, shapes, and surroundings, from high-mountain Snail to deep-ocean Squid.