BAIANIJS, a genus of cirrhopoda (q.v.); the type of a family, including all those cir rhopods which are destitute of a flexible stalk, and of which the shell is symmetrical. These characters at once distinguish them from barnacles (q.v.). In the genus B. the base is usually formed of a thin calcareous plate, the sides of six valves; and four small valves form the operculum, exactly closing the aperture at the top. The name (signify an acorn) was originally given by the ancient Greeks, from a supposed resemblance of someof the kinds to acorns; and acorn-shell has sometimes been adopted as an Eng lish name. There are many species, and they are found in almost all seas, attached to stones, timber, shells, crustaceans, etc. They cover the rocks between high and low water-mark on many parts of the coast as with a white calcareous incrustation, so that arithmetic fails in computing, and imagination in conceiving their multitudes. They may, however, be readily passed over as individually objects of little interest when they are seen after the title has left them, for then their valves are closed, and they exhibit no sign of life; but if observed in a pool of the rocks, or anywhere under water, they pre sent a'very different and extremely pleasing spectacle, the opercular valves continually opening and shutting with a quick but pretty regular motion, and an exquisitely delicate apparatus of feathery arms or eirrhi (see CIRRI1OPODA) being as frequently thrown' out and retracted like a hand or a little net, to seize and carry into the mouth the minute nutri tious particles or very small animals upon which the creature feeds. Thus, the little Wan'. immovably fixed to the rock, or carried about at the pleasure of mollusks or
crustaceans to which they adhere, obtain their food from the waters around them.
A remarkable fact in the natural history of these creatures has recently been discov ered by Mr. Thompson of Cork, that in the earlier stages of their existence they are not fixed as in their adult state, but move about very actively in a succession of bounds, by means of swimming-feet like those of the cyclops (q.v.); having, however, a shell, appar ently of two valves, resembling a very minute muscle. Still more remarkable is the discovery made along with this, that in their early locomotive state they possess large stalked eyes, which disappear along with the organs of locomotion when they attach themselves—probably by the guidance of some peculiar instinct—to their final place of repose, undergoing a transformation into perfect cirrhopods, and acquiring as a covering their Some of the larger species of B. were esteemed a delicacy by the ancient Romans. The Chinese entertain the same estimation of B. liatinnahulura, which is said to resemble lobster in taste; and B. psittacus, a South American species, which is in like manner compared to crab, is exported in large quantities from Concepcion de Chili to Valparaiso and Santiago. This species is sometimes almost 4 In. in diameter, the height considera bly more. It is chopped off the rocks with a hatchet. The two posterior opercular valves are beaked, from which it receives the name of pica, and its scientific trivial name, psittacus (a parrot).