Mollusks

A very diverse group of invertebrates. For the cook, the three important categories are bivalves, univalves, and cephalopods. Bivalves are saltwater creatures with two shells, such as oysters, scallops, and clams. Univalves, such as snails and winkles, have only one shell and can be either saltwater or land inhabitants. Cephalopods, including squid, cuttlefish, and octopus, have bilateral symmetry and are somewhat inverted—they have a muscular mantle on the exterior of their shell. They move by expelling water from a siphon under the head. Cephalopods generally have well-developed eyes, arms, or tentacles, and they can eject ink from an ink sac as a means of defending or hiding themselves from predators.