Crustaceans are not a class of mollusk. Lobsters and crayfish are two types of crustaceans. Gastropods are a class of mollusk that includes snails, conchs and whelks. They are also called univalves. Bivalves are a class of mollusk that includes clams, oysters and scallops.
Cephalopods are a class of mollusk that includes squid, nautilus and octopus.
Next Question 3. An operculum is a snail s trapdoor . The antennae on a mollusk are called tentacles. Next Question 2. Pupa is not a development phase of mollusks.