This is a tender and brittle shell-fish of a very peculiar species; its length is about an inch, and its diameter about three quarters of an inch. The shell is not composed of two pieces or valves, as in others, but of five; two of these are larger than the rest, to which are affixed two smaller ones; the fifth piece is long, slender, and crooked, running down length-ways, and covering the joinings of the other pieces. The shell part is of a pale red, variegated with white; it adheres to a neck or pedicle of an inch long, and about a fifth of an inch in diameter; by which means it affixes itself to old wood, to stones, to sea-plants, or any other solid substance that lies under water. It can shorten or extend this neck at pleasure, which resembles a small gut, and is usually full of a glareous liquor; it is composed of two membranes, an external one, hard and brown, an internal one, soft and of an orange colour. The large portions of the shell open and shut in the manner of the bivalves; the others, being moveable by means of their membranaceous attachments, give way to the opening of these, and to the motions of the body of the fish in any direction. It is furnished with a cluster of filaments or tentacida, placed in a row on each side, usually twelve, sometimes fourteen in number. They are a kind of arms appropriated for catching its prey, and therefore placed so as to surround the mouth of the animal, which is situated between them, and consequently easily receives what they thrust towards it. By the motion of these arms, which may be exerted in such a manner as to play either within or without the cavity of the shell, it forms a current of water, which brings with it the prey it feeds upon. Fig. 1 represents two of these arms as magnified by the microscope; Fig. 2, the natural size of those from which these drawings were made. Each arm consists of several joints, and each joint is furnished on the concave side of the arm with a brush of fibrillæ or long hairs. The arms, when viewed in the microscope, seem rather opake; but they maybe rendered transparent, and form a most beautiful object, by extracting out of the interior cavity a bundle of longitudinal fibres, which runs the whole length of the arm. Mr. Needham[102] thinks the motion and use of these arms illustrates the nature of that rotatory motion which some writers have thought they discovered in the wheel animal. [101] This animal is classed by Linnæus among the Vermes Testaceæ. Its generic character is: Animal, resembling a triton; Shell, consisting of several unequal valves; affixed by its base. Specific character: Pedunculated Barnacle, with compressed shell consisting of five valves. Syst. Nat. p. 1107, 1109. EDIT. [102] Needham’s Microscopical Observations.