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Show 88 CH.UST ACEA. 1. Those which have fourteen feet all terminated by a hook · a point. 'or tn 2. Those which also have fourteen feet, but which are-the four last at least-simply natatory. 3. Those which have only ten apparent feet. The first section is divided into two. Some of them,-the URoPTEllA, Latr., usually have a large head· the antennre are frequently short, and in some but two in nu b : the body is soft. All the feet, the fifth pair at most excepte: er, si. m p Ie , th e an t er1· or are short or small, and the tail is either' faurre-mshed at the extr.e mity with lateral fins, or is terminated by pot·n ts or appendages, Widened and bidentated, or forked at their poste · extr em1. t Y· Tl1 ey m. h ab1. t the bodies of various Acephala or LrliOn-r nrean Medusre, and of some other Zoophytes. Here, as in PHRONIMA, Lat., There are but two-very short and biarticulated-antennre· the fifth pair of feet is the largest of all and terminates in a did:ct 1 forceps; the six appendages of the extremity of the tail are st~i~ 1fo rm, elongated and forked or bidentated at th e en d ; s·t x vest·c u-ar sacs m.ay be observed between the last feet. Several species a • pe~r to exist, but they have not been strictly and comparatively d~scrlbed. :hat which has been taken for our type is the Cancer seden· tar~us, ~-orsk:, Fa~n. ~rab., P· 95; Latr., Gener. Crust. et Insect.' I, u, 2, "' which IS found in the Mediterranean, and in· habits a membranous transparent body that haQ the fi f cask d h' h w gure o a · ' an w 1c appears to proceed from the body of · of Beroe. a species T· he Pf lwonime sentinelle, Risso ' Crust ., II , 3, m. h ab 1't s t he t.n · t~rwr o, Medusa::, constituting the genera Equoree and Gero· hm· e obf Peron und Lesueu r. A not h er speci. es, according to Leach, , as ecn observed on the coast of Zealand. 'df hefr eh we observ· e four antennre·' all the ~11e et are S.i mp1 e · on each l si fie 0 t fe ex:remity of the tail is a lamellated or foliaceo~s fin the ea ets o wh1ch are a cumm· ated or unidentated at the end. ' HYPERIA, Lat. The body thickest anterio I . th cupied by oblong r y' e greater portion of the head oc· eyes somewhat emarginated on the inner edge; AMPlilPODA. 89 two of the antennre, at least half as long as the body and terminated by a long setaceous stem composed of several small joints( 1 ). PHROSINE, Risso. Form of the body and that of the head similar to the Hyperire, but the antennre, at most, the length of the latter, composed of but few and styliform joints, or terminated by a stem resembling an elon-gated cone(2). DAoTYLOOERA, Lat. The body not thickened anteriorly; the head moderate, depressed, nearly square; eyes small; four extremely short antennre composed of but few joints, as in Phrosine, of various forms-the inferior being thin and styliform, and the superior terminated by a small concave plate on the inner side-t·esemble a spoon or forceps(3). The others-GAMMARIN.JE, Latr.-always have four antennre; their body, invested with coriaceous and elastic tegments, is generally compressed and arcuated ; the posterior extremity of the tail is deprived of fins; its appendages are styliform and cylindrical, Ol' coni- (1) Cancer monoculoidea, Montag., Ttans. Lin. Soc. XI, ii, 3;-Hyp!rie deLesueur, Lat., Encyclop. Method., Atl. d'Hist. Nat., CCCXXVIII, 17, 18; Desmar. Consid., p. 258. N.B. Near the Hyperia: should be placed the genus TuEMIBTo, Lat., carefu1ly figured and described in the Mem. de la Soc. d'Hist. Nat., tome IV. As in the Hyperia:, the eyes are very large and occupy the larger portion of the head; two of the antenna: (the inferior), all terminated by a multi-articulated stem tapering to a point, are evidently longer than the others. The part there called levre inferieure, is the ligula; those which appeared to form the thil·d pair of jaws are the first of the foot-jaws, and, as in the Ampbipoda and Isopoda, close the mouth inferiorly under the form of a lip. The four remaining foot-jaws are very short, directed forwards and laid upon the mouth in such a way that they seem to constltute a. part of it, so that if we do not count them, or if we merely consider the following locomotive and much more apparent organs as feet, this animal, like the Hyperia and Phrosine, appears at the first glance to have but ten feet instead of fourteen. The third pair offoot-jaws is terminated by a small didactyle forceps. The same pair of feet, properly so called, is much longer than the others; its penultimate joint is greatly elongated, and is armed with a range of small spines forming a sort of comb. Dut a single species is known. (2) Phros. macrophthalma, Risso, Journ. de Phys., Octob. 1822; Desmar., lb., p. 259; Cancer galba, Montag., Trans., Lin. Soc., XI, ii, 2. (3) Phros. seminulata, Uisso, lb.; Desmar., lb. The stem of the inferior antenna: consists of two ot• three joints, while in Phrosine it is inarticulate. There also, the joints of the peduncles of the -arne antenna: are shorter. VoL. IU.-M |