In cirripeds the maxillopodan body plan is so different from the general crustacean body plan that it is almost unrecognizable. The carapace is either bivalved with numerous small calcareous plates embedded in the tissue or consists of a fleshy mantle that secretes the large plates that encase the animal.
Cirripeds are the only crustaceans other than the Conchostraca that keep the exoskeleton of their carapace throughout life instead of growing a new one each time they molt. They simply add material to the calcareous plates that surround their bodies as they grow. However, they do molt the chitinous exoskeleton from the rest of their body. These transparent, flaccid, spidery molts are often found floating in surface waters.