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the final larval stage of development of cirripede crustaceans (barnacles). The cypris has a bivalve shell that covers the entire body; the shell resembles that of representatives of the subclass Ostracoda, particularly species of the genus Cypris. It has a median eye, two pairs of antennae, one pair of mandibles, two pairs of maxillae, and six pairs of thoracic legs. The abdomen is reduced. The cypris swims in the water and then descends to the bottom, attaching itself by the first pair of antennae to the substrate, where it is transformed into an adult. The antennae become reduced, and the shell fold is converted to a mantle, in which the skeletal plates characteristic of adult cirripedes are formed. In parasitic cirripedes the cypris undergoes regressive metamorphosis.