Cirripedes, Or Cirrkopoda (Lat. cirrus, curly, and pes, a foot), a group of articulated animals, long regarded as belonging to the mollusca, but really to the class of crustaceans, and to the order of entomostracans. The barnacles and acorn shells formerly described among the multivalves are included in this class. Their bodies are soft and protected by the shelly covering secreted from their surface. But the anatomical structure of the cirripedes (of the nervous system particularly) connects them with the articulata, and so also their development from the egg and subsequent transformation. (See Barnacle.) A peculiar feature is the prolongation of the body and its division into several branches, each of which is furnished with a pair of curled arms filled with cilia or hair-like filaments resembling feathers, and which are constantly moving in the water for the purpose of collecting food. The class is divided into two principal groups, the pedunculated and the sessile; the former, like anati-fa, having a long peduncle, or footstalk, by which the animal fastens itself to rocks or wood; and the latter, like the barnacle, being deficient in this, the shell consequently lying close to the substance to which the animal adheres.
Several genera of each group are described, all marine.
Specimens of the Group of Cirripcdes. 1 and 2. Coronula diadema (sessile). 8. Conchoderma aurita (pedunculated).