Rock-clinging mollusks are a type of marine invertebrate that attach themselves to rocks or other hard surfaces. ABALONE, oysters, and limpets are all examples of rock-clinging mollusks. ABALONE is a large sea snail with a single shell and a row of tentacles around its head. Oysters are bivalve mollusks that have two shells and filter feed on plankton. Limpets are small, cone-shaped mollusks that have a single shell and a strong muscular foot that they use to cling to rocks.