Crusta

[Lat.] (Fine Arts.) An engraved gem; an intaglio. Crustaceæ, CRUSTACEANS, n. pl. (Zool.) A cla of animals, branch Articulata, which are covered with a soft shell or crust. These consist of crabs, lobsters, and many others of a much le complicated structure. Their solid envelope may be regarded as a kind of epider. mis; for beneath it we find a membrane like the true skin of higher animals; and at certain times it detaches itself and falls off, in the same manner as the epidermis of reptiles separates itself from their bodies. The Cre spire by means of branch iæ, usually attached to their feet or to their jaws; they have from five to seven pairs of feet; their head is frequently not distinct from the trunk, provided with from two to four jointed, setaceous antennæ; and two compound movable eyes seated on peduncles, which are sometimes movable, and at others fixed: they have a distinct heart, and a regular circulating system; and their organs of reproduction are placed either in the feet or tail. The limbs vary from ten to fourteen, each having six articulations. The two anterior limbs, and sometimes even three on each side, are provided with forceps; at other times they are terminated by simple hooks, and in many instances by appendages which fit them for swimming. The mouth has usually two mandibles, a labium or lip below, and from three to five pairs of jaws; these small leg-shaped appendages are not fitted for locomotion, but being situated near the mouth, a ist in the operation of feeding. Animals of this cla live in various situations, suited to their organization: some inhabit considerable depths of the ocean, others are found on rocky shores, or in muddy shallows; some, such as crawfish, inhabit rivers, under stones and banks; while the land-crab takes np its abode in inland situations, making periodical journeys to the coast in vast numbers, for the purpose of depositing its eggs. Some of the C. have the power of emitting light in the dark. Others are endowed with the power of not only detaching one of their limbs, when seized upon by an enemy, but have also the faculty of reproducing the severed limb. C. may be divided, according to Dana, into the three orders DECAPOD A, TETRA DECAPODS, and ENTOMOSTRACA, 9. v. Crustacean, a. Crustaceous; relating or pertaining to the Crustacea. -n. A member of the Crustacea cla of animals. Crusta ceo logʻical, a. Relating or pertaining to crusta ceo logy. ology.