A land snail (Helix sp.) gliding in slow motion along a wet plank on its muscular foot, gastropod, after a rain storm. They glide by secreting a slimy mucus and leave shimmery trails. Land snails are terristrial gastropod mollusks with shells made of calcium carboanate coiled in a logrithmic spiral which grows exponentially as the snail grows. Snails are considered agricultural pests because they feed on plant leaves, stems, soft bark, fruit, vegitables, shredding them with their ribbon-like tongue, called a radula. The radula has thousands of microscopic hook structures acting like teeth which tear and shred what the snail is eating. Snails can often be heard 'crunching' their food. The snail's eyes can be seen as tiny spots on the upright tentacle ends of its head, 'eyestalks', whereas the lower tentacles act as olfactory organs.