| A | B |
|---|
| Phylum Mollusca | consists of mollusks; they are soft-bodied animals the usually have an internal or external shell |
| trochophore | free-swimming larval stage of an aquatic mollusk |
| foot | muscular part of a mollusk |
| mantle | thin layer of tissue that covers most of a mollusk’s body |
| shell | structure in mollusks made by glands in the mantle that secrete calcium carbonate |
| visceral mass | area beneath the mantle of a mollusk that contains the internal organs |
| radula | tongue-shaped structure used for feeding by snails and slugs |
| siphon | tubelike structure through which water enters and leaves a mollusk’s body |
| open circulatory system | blood is pumped through vessels by a simple heart |
| Class Gastropoda | members of this class include pond snails, land slugs, sea butterflies, sea hares, limpets, and nudibranchs |
| gastropods | shell-less or single-shelled mollusks that move by using a muscular foot located on the ventral side |
| Class Bivalvia | members of this class have two shells that are held together by one or two powerful muscles |
| bivalves | common species include clams, oysters, mussels, and scallops which stay in place for most of the time |
| Class Cephalopoda | typically soft-bodied mollusks in which the head is attached to a single foot (the foot is divided into tentacles or arms) |
| cephalopods | most active of the mollusks including octopi, squids, cuttlefishes, and nautiluses |
