Barnacles is a name for animals in the subclass of crustaceans. Balanus Glandula is the scientific name for them. When Barnacles are still larvae they float around in the water. When they become mature they will attach to things like rocks, bottoms of boats and shell fish. Acorn Barnacles are mostly found in temperate and cold salt water. They like to attach to hard surfaces. Acorn Barnacles eat plankton by sucking in the water around them, while closing their teeth and opening their mouth. Then they lick all the plankton that got stuck in their teeth. The Acorn Barnacle is usually 3-4 inches across. The Acorn Barnacle shell is made with six big pieces of shells connected by smaller pieces of shells. By all the things we know about the Acorn Barnacle we can tell it is certainly a very interesting animal.