DIVISION A. LOPILYROPODA (Gr. lophouras, having stiff hairs). Possessing few bran cilia, and attached to the appendages of the month. Feet few, mainly locomotive. Mouth not suctorial, but has organs of mastication. There are two orders.
Order I. Ostrawda (Gr. ostrakon, a shell; eidos, form), water-fleas. Small animals inclosed in a shell composed of two valves united along the back by a membrane. The respiratory organs are attached to the posterior jaws, -and there are only two or three pairs of feet. Most of them pass through several stages of metamorphosis. See CMOs.
Order II. Copepoda (Gr. trope, an oar, and podes, feet). These animals inhabit both salt and fresh water. Head and thorax covered by a shell, and furnished with five pairs of swimming feet, and generally two caudal locomotive appendages. One.of the most common of the water-fleas is a member of this order, under the name of cy•lops These oar-footed crustaceans are regarded by some zoologists as being the same in the larval state as ichthyophira. the hitter animal becoming modified by being,attached to, and existing upon, other animals.
Drvisrox B. BRANCHIOPODA (q.v.). These animals have many branchim attached to the legs, which are numerous and formed for swimming. This division is made to include cladocera, phyllopoda, and tritobita, although the latter departs somewhat from the characteristics of the other members.
Order I. Cladocera (Gr. Rados, a branch, and keras, a horn). Carapace or shell simi lar to ostracoda; feet, four to six pairs, usually bearing respiratory organs; two pairs of antennae, one pair large, branched, and used for swimming. The daphnia puler, or branched-horned water-flea, is inclosed within a bivalve shelf which opens anteriorly. The head is not inclosed, and has a single eye. The gills are in the form of plates, attached to five pairs of thoracic. legs. The animal is parthenogenetic (see PARTHENO
GENESIS), and it produces two kinds of eggs. One kind, the summer eggs. are deposited between the valves of the carapace, are hatched there; but the winter eggs are deposited in a receptacle on the back of the carapace, called the saddle, \\ditch after a time is east off and floats about till the water becomes warm enough to hatch the eggs.
See AVATER-FLF_A.
Order II. Phyllopoda (Gr. pkyllon, a leaf), leaf-footed crustaceans. Carapace covering head and thorax. or the body entirely naked. Feet never less than eight pairs, leaf formed and respiratory, and also used in swimming. They arc interesting On account of their affinity to the extinct order of trilobites. The various species of the genus brattehipptis have no carapace. and exist in ponds and swamps in ninny parts of the world. The brine-shrimps (genus arteuria) are found in the brine pans of salt-works, and in lakes much salter than the ocean. They abou.al in the Great Salt lake of Utah. See BRINE-SRI:IMP.
Order III. Trilobite( (three-lobed crustaceans). See TRILOBITES.
Order IV. Nerostomata (Gr. meron, thigh. and stoma. month). Crustaceans, often of great size, in which the month is furnished with mandibles and maxillm, whose termi nations become walking or swimming feet and. organs of prehension. Divided into two suborders, xi/rhos-um and eurypterida.
Sub-order 1. Xiphosura (Gr. alphas, a sword; oura, a tail). The only living repre sentatives are the king-crabs (horse-shoe crabs), of which there are but few species. See KING-CRAB and IYIEnosTomATA.
Sub-order 2. Eurypterida (Gr. euros, broad. and pteron, wing). extinct crustaceans, some of which reached gigantic dimensions. See MEnosTom.vrA.