Fascinating science-

“This humble snail lives in hydrothermal vent fields two miles deep in the Indian ocean, and is surrounded by vicious predators. For example, there’s the “cone snail”, which stabs at its victims with a harpoon-style tooth as a precursor to injecting them with paralyzing venom. Then there’s the Brachyuran crab, which has been known to squeeze its prey for three days in an attempt to kill it. Yowsa.”

“Ah, but the scaly-foot gastropod has its own tricks.  It takes the grains of iron sulfide floating in the water around it and incorporates it into the outer layer of its shell. It it thus an “iron-plated snail”.

from – http://www.collisiondetection.net/mt/archives/2010/02/life_isnt_easy.php