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Show 108 t:ltUSTACEA. it has passed the winter. The male, much larger than th , 1 . 1 P • l e Je. rna e, ca~r1es the atter .or e1ght days, c asping her with the fourth pa1r of feet. When he abandons her she is loaded w· h · a great number of ova inclosed in a membranous sac, situa:;d under the thorax, which affords an issue to the young thro h a longitudinal fissure. ug . ONrsconA, Lat. The ?nis~odre or J a.nirre( 1) o_f Leach differ from the Aselli in the approximatiOn of the1r eyes, m. the superior antennre which are shorter than the peduncle of the mferior, and in the hooks of th tarsi which are bifid. e The only• species known, the Janira maculoaa ' Leach•, De s. mar., Cons1d., p. 315, was found on the coast of England a the Fuci and Ulvre. mong J ..£RA, Leach, But two tubercles at the extremity of the tail in place of the sty lets. But a single speci~s has been described, the g~ra albifrom, Leac~; Desm., Cons1d., p. 316, which is very common on the Enghsh coast among the Fuci and Ulvre. L Finally, the lsopoda of the sixth and last sect1' 0 n- 0 NISOIDES at.-have f?ur antennre also, but the two intermediate ones are ver; ~~all, but slightly apparent, and are composed at most of but two JO.mts; the lateral are ~etaceous. The tail consists of six segments, Wlth two or four styhform appendages on the posterior margin of the last one, and is. without lateral fins. Some of them are aquatic and others terrestrial. In the latter, the first leaflets of the under part of the tail exhibit a series of small holes, through which air penetrates to the organs of respiration therein contained. In some, the sixth joint of their antennre, or the stem, is so com· posed, that by counting the little joints of this part the total num· her amounts at least to nine. These Isopoda are marine and form two subgenera. The TYLos, Lat., Appears to possess the faculty of rolling A itself into a ball. The qu(e1n)t lAy bneaemn eo beim' pldo yt ed by Ris fi 1 ~0 ~r a genua of the same class; I have conae· Jge 0 rep ace 1t wtlh another. ISOPODA. 109 last segment of the body is semicircular, and exactly fills up the emargination formed by the preceding one; the posterior appendages are very small and entirely inferior. The antennre consist of nine joints, the last four composing the stem. On each side is a depressed tubercle r~pre~enting. one of th~ interme~iate ~n_tenn~; the intervening space 1s ratsed. 1 he branch1re are ves1cular, Imbricated, and covered by laminre( 1 ) • LIGIA, Fab. The stem of the lateral antennre composed of a great number of small joints; two very salient stylets divided at the end into two branches, at the posterior extremity of the body. 1in Ligia oceanica; Oniscus oceanicus, L., Desmar., Consid., XLIX, 3, 4, about an inch long, grey, with two large yellowish spots on the back. The lateral antenn~ ~re less than half th~ length of the body, and their stem consists of thi~:teen . joints. The stylets are as long as the tail. This animal is very common on the coast of France, where it is seen climbing up the rocks, Stc. If an attempt be wade to capture it, it quickly folds up its feet and lets itself fall. In the Ligia italica, Fab., the lateral antennre are nearly as long as the body; the sixth joint, or the stem, is divided into seventeen small ones. The stylets are much longer than the tail. Ligia muscorum; Oniscus hypnorum, Fab., Cuv., Journ. d'Hist. Nat. II, xxvi, 3, 4, 5; Oniscus agilis, Panz., Faun., Ins. Germ., Fascic. IX, xxiv. The lateral antennre shorter than the half of the body, and their stem composed of but ten small joints. The peduncle of the posterior stylets is furnished on the inner side with a tooth and seta. In others, all terrestrial, the lateral antennre consist at most of eight joints which gradually diminish in size towards the extremity, so that no one of them appears to be divided or compound. Here, the posterior appendages, or stylets~ project beyond the last segment. The body does not contract into a ball, or does it im-perfectly. I l 1 ' ( PHILOSOIA, Lat. The lateral antennre divided into eight parts and exposed at base; (1) Tyl08 armadillo, Lat., fig. in the pl. u'Hist, Nat. of the great work on Egypt-from the Mediterranean. |