Crustacea

a sub-kingdom of the great group of articulate or annulose animals, and agrees with the Insects, ‘Arachnids and Myriapods in having the body divided into transverse rings or somites, all of which may and some do po e each a pair of appendages or limbs made up of several pieces jointed or articulated to each other. This character of the limbs separates the group from the annulate animals (earth-worms, sand-worms, tubeworms, leeches), the limbs of which consist only, when present, of projections of the integument supporting movable bristles. The Crustacea are mostly aquatic, and all, even the terrestrial forms, breathe through the integument, or through the projections of the integument which are known as branch is or gills. Locomotion is by the limbs in walking or swimming, or by the limbs together with the flapping of the posterior part of the body, as in the lobster.