Snails, clams, worms, and insects are all invertebrates. This number was even greater in the past. Although they do not have bones, many invertebrates have a shell or a hard exoskeleton that can be fossilized. The exoskeleton is like a suit of armour, giving the animal support and protection. Modern invertebrates like lobsters, cockroaches, and spiders have exoskeletons.
Snail lives in ocean.
Dead snail is buried. Soft body decays. Almost all fossils are preserved in sedimentary rocks , rocks that formed when layers of sediment such as clay, mud, silt, or sand became compressed and hardened over millions of years. These types of sediments are laid down in lakes, swamps and oceans. This is one of the reasons why most fossils are the remains of animals who lived in or near the water.