Mollusk Phylum Overview
The Phylum Mollusca contains the widest range of difference between it's animals. Some Mollusks are found everyday, that include Snails, Slugs, Clams, Muscles and Octopuses. Mollusca also contains animals that are almost never seen, deep under water, know as Aplacophorans and Monoplacophorans. Monoplacophorans we're discovered moderately recently, in 1952 in the deep sea. Monoplacophorans we're only known to exist before that from fossils. All Mollusks have a muscular foot, excluding the Aplacophorans. This leg is used for movement, clinging to surfaces, burrowing, anchoring in sediment, swimming, and grabbing. The diversity of the foot shows the diversity in the Mollusks. Mollusks have a layer of tissue on their epidermal layer called the Mantle. Shell structures are made from extracellular excretions which come from "specialized glands". In all molluscan groups the shell is produced in layers of (usually) calcium carbonate, either in calcite or aragonite form. The shell is normally produced in layers of calcium carbonate, either in aragonite or calcite form. Aragonite is a commonly found crystal forms of calcium carbonate, calcite is also another crystal form of calcium carbonate.