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( Examples , Cuttle-fish, Nautilus.) CETACEA An order of Mammalia, including the Whales, Dolphins, &c., having the form of the body fish-like, the skin naked, and only the fore-limbs developed. CHELONIA An order of Reptiles including the Turtles, Tortoises, &c. CIRRIPEDES An order of Crustaceans including the Barnacles and Acorn-shells. Their young resemble those of many other Crustaceans in form; but when mature they are always attached to other objects, either directly or by means of a stalk, and their bodies are enclosed by a calcareous shell composed of several pieces, two of which can open to give issue to a bunch of curled, jointed tentacles, which represent the limbs. COCCUS The genus of Insects including the Cochineal. In these the male is a minute, winged fly, and the female generally a motionless, berry-like mass. COCOON A case usually of silky material, in which insects are frequently enveloped during the second or resting-stage (pupa) of their existence. The term `cocoon-stage' is here used as equivalent to `pupa-stage.' COELOSPERMOUS A term applied to those fruits of the Umbelliferæ which have the seed hollowed on the inner face. COLEOPTERA Beetles, an order of Insects, having a biting mouth and the first pair of wings more or less horny, forming sheaths for the second pair, and usually meeting in a straight line down the middle of the back. COLUMN A peculiar organ in the flowers of Orchids, in which the stamens, style and stigma (or the reproductive parts) are united. COMPOSITÆor COMPOSITOUS PLANTS Plants in which the inflorescence consists of numerous small flowers (florets)brought together into a dense head, the base of which is enclosed by a common envelope. ( Examples , the Daisy, Dandelion, &c.) CONFERVÆ The filamentous weeds of fresh water. CONGLOMERATE A rock made up of fragments of rock or pebbles, cemented together by some other material. COROLLA The second envelope of a flower usually composed of coloured, leaf-like organs (petals), which may be united by their edges either in the basal part or throughout. CORRELATION The normal coincidence of one phenomenon, character, &c., with another. CORYMB A bunch of flowers in which those springing from the lower part of the flower stalk are supported on long stalks so as to be nearly on a level with the upper ones. COTYLEDONS The first or seed-leaves of plants. CRUSTACEANS A class of articulated animals, having the skin of the body generally more or less hardened by the deposition of calcareous matter, breathing by means of gills. ( Examples , Crab, Lobster, Shrimp, &c.) CURCULIO The old generic term for the Beetles known as Weevils, characterised by their four-jointed feet, and by the head being produced into a sort of beak, upon the sides of which the antennæ are inserted. CUTANEOUS Of or belonging to the skin. DEGRADATION The wearing down of land by the action of the sea or of meteoric agencies. DENUDATION The wearing away of the surface of the land by water. DEVONIANSYSTEM or formation A series of Palæozoic rocks, including the Old Red Sandstone. DICOTYLEDONSor DICOTYLEDONOUS PLANTS A class of plants characterised by having two seed-leaves, by the formation of new wood between the bark and the old wood (exogenous growth) and by the reticulation of the veins of the leaves. The parts of the flowers are generally in multiples of five. DIFFERENTIATION The separation or discrimination of parts or organs which in simpler forms of life are more or less united. DIMORPHIC Having two distinct forms. Dimorphism is the condition of the appearance of the same species under two dissimilar forms. DIOECIOUS Having the organs of the sexes upon distinct individuals. DIORITE A peculiar form of Greenstone. DORSAL Of or belonging to the back. EDENTATA A peculiar order of Quadrupeds, characterised by the absence of at least the middle incisor (front) teeth in both jaws. ( Examples , the Sloths and Armadillos.) ELYTRA The hardened fore-wings of Beetles, serving as sheaths for the membranous hind-wings, which constitute the true organs of flight. EMBRYO The young animal undergoing development within the egg or womb. EMBRYOLOGY The study of the development of the embryo. ENDEMIC Peculiar to a given locality. ENTOMOSTRACA A division of the class Crustacea, having all the segments of the body usually distinct, gills attached to the feet or organs of the mouth, and the feet fringed with fine hairs. They are generally of small size. EOCENE The earliest of the three divisions of the Tertiary epoch of geologists.