This is a picture of a snail, a gastropod. Actually, you can only see the shell, but the snail is inside. A snail is an example of a mollusk. The shell is made of chitin and protein. They also have a large, muscular foot that allows movement. Mollusks also have a radula, which is a rasping tongue. They also have a mantle cavity. Other members of the phylum are cephalopods, such as squids and octopi, and slugs.