. Elementary text-book of zoology, tr. and ed. by Adam Sedgwick, with the assistance of F. G. Heathcote. 456 CEUSTACEA. slender flagellum composed of few joints. The posterior antennae .are in the male very long and folded three to four times together in a zigzag fashion ; in the female they are short and straight, sometimes quite reduced. The basal joints of the fiflh and sixth pairs of legs are usually enlarged into great lamellae, which cover the thorax. The seventh pair is generally rudimentary. Eutyphls (T//j}his Risso) ovoides Eisso (Platyscelus serratvs Sp. Bate), Mediter- ranean. Oxycf
. Elementary text-book of zoology, tr. and ed. by Adam Sedgwick, with the assistance of F. G. Heathcote. 456 CEUSTACEA. slender flagellum composed of few joints. The posterior antennae .are in the male very long and folded three to four times together in a zigzag fashion ; in the female they are short and straight, sometimes quite reduced. The basal joints of the fiflh and sixth pairs of legs are usually enlarged into great lamellae, which cover the thorax. The seventh pair is generally rudimentary. Eutyphls (T//j}his Risso) ovoides Eisso (Platyscelus serratvs Sp. Bate), Mediter- ranean. OxycfpJtalus pisedtor Ed\v., Indian Ocean. 2. Sub-order:—Isopoda.* Arthrostraca with usually broad, more or less arched body, with seven free tho- racic rings, with lamellar legs function- ing as branchice on the short-ringed, often reduced abdomen. The structure of the body, which is flat in shape and covered by a hard, usually encrusted integument, presents a great agreement with that of the Amphipoda, to which the in many respects peculiar Tanaidce are most nearly allied. The abdomen of the Isopodsis, however, usually much short- ened and composed of six short seg- ments, which are often fused with one another; it terminates with a large c ludal lamella. The abdominal legs are only exceptionally (Tanaidce) swimming feet; as a rule they have the form of branchial lamellae. The sixth pair may be fin-like or styliform. The anterior antennae are, with a few exceptions, shorter than the posterior and external antennae ; in rare cases (Oniscidai) they bscome so much reduced that they are hidden beneath the cephalic carapace. In exceptional cases only (Apseudes). Fir,. 359.—AstUun aquatictin (after G. O. Sars). Female with brood pouch, seen from the ventral side- * H. Rathkc, " Untcrsuchungen liber die Bildung und Entwickelung der Wasserasscl," Leipzig, 1832. Lereboullet, "Sur les Crustaces de la famille res Cloportidcs. etc," Mem. du Museum d'hist. nat. de Stras
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