The Probert Encyclopaedia of Nature

CIRRIPEDIA

Cirripedia is the Cirrepedes subclass of crustacea. These are the barnacles and acorn shells. They are sedentary animals with a reduced head and abdomen. The most striking appendages are usually the six pairs of biramous thoracic feet, which are used in catching food, being swept through the water after the fashion of a fishing net. They are crustaceans which have undergone retrograde metamorphosis, being free-swimming in the larva form, but becoming after a time attached by the head. When adult they are affixed to some substance, either set directly upon it, as in the genus Balanus; or placed on a foot-stalk, as the barnacle; or sunk into the supporting substance, as the whale-barnacle.
Research Cirripedia