OCR Text |
Show 60 ClWSTACEA. separates them from the fourth ot· that of the Cal'ides. The antenure are inserted at the same height, or on a level; the peduncle of the latet·al ones, when accompanied by a scale, is never entir·ely covered by it. Thet·e are frequently but four pairs of sub-caudal false feet. The two mediate antenn::e arc always terminated by two filaments onlr, usually &hortcr than their peduncl~, or scarcely any longer. The external leaflet of the natatot·y appendages of the penultimate segment of the tail is never divided by a tt·ansvet•se sutut·e. In our· second section, o1· the LocusTJE, so cal!etl f1·om the name Locust a gi vcn by the Latins to the most remarkable Cr·ustacca of this division, and from which is derived that of Langouste applied to them in Fr·auce, there are never more than four pairs of false feet. The posterior extremity of the fin that terminates the tail, is always nearly membranous, or less solid than the rest. The peduncle of the mediate antenn::e is always longer than the two terminal filaments, and more or less bent 01' geniculate; the lateral ones are neve1· fur·nished with scales; sometimes they are reduced to a sin~le peduncle which is dilated, ver·y flat, and in the form of a crest; sometimes they are large and long, terminating in a point and bristled with spines. All the feet ar·e nearly similar and end in a point; the two first are merely somewhat larger; their penultimate joint and that of the two last are at most unidentated, but without forming with the last a perfectly didactyle hand. The pectoral space included between the feet is triangular; the thorax is almost square or sub-cylindrical, and without any frontal prolongation or rostrum. ScYLLARus, Fab. The Scyllari, or Sea-Grasshoppers as they are called, present a very unusual character in the form of their lateral antennre; the stem is wanting and the joints of the peduncle, very much dilated transversely, form a large, flattened, horizontal crest more or less den· dated. The external branch of the sub-caudal appendages is terminated by a leaflet; but the internal one, in some of the males, is a mere tooth. Doctor Leach has established three genera of them, founded on the proportions and form of the thorax, the position of the eyes, and some other parts. They are, 1. SoYLLARus, where the thorax is as long as it is broad 01' longer, and without any lateral incisure, the eyes always situated near its ante· rior angles; the penultimate joint of the two posterior feet uniden· tated in the females. They excavate holes in the clayey soil near the shore which serve them for habitations. DECAPOD A. 61 In one of them, the 8cyllare ours; Cancer arctus, L.; Oigale de; mer, Rondel., lin. XIII, chap. VI; Herbst., XXX, 6, the external Ol' late1·al antenn<e are much dentated. The thorax is marked with tluee longitudinal and dentated ridges, and the super·ior surface of the tail sculptured, but its lateral margin not crcnulated. The other·, 8cyllartts a>quinoxialis, Fab.; 8cyllartts orientalis, Risso; 8quille large, or the Orc!Letta, Ronde!.; Gesn., I-Iist. des Anim., III, p. 1097, is large, shagrecncd, and without ridges. The crests are edcntated, and the mar·gin of the segments of the tail crenulated. Its flesh is highly esteemed and the O\'a are of a vivid red. 2. TuENUS, \vhere the fore part of the tho1·ax is br·oader than it is long, each lateral margin deeply incised, and the eyes are placed at its anterior angles( 1 ). 3. !BAcus, only differing from Thenus in the position of the eyes, which are app1·oximated to the origin of the intermediate antennre. In an Australian species, lbacus Pronii, Leach, Zool. Miscel., CXIX; Desmar., Consid., XXX, 12, the exterior lateral margin of the third joint of the external foot-jaws is transversely striated and notched in the manner of a crest(2). In the PALINURus, Fab. The lateral antennre are large, setaceous, and bristled with spines. Of these Crustacea, called Oarabos by the Greeks, and Locusta by the Latins, and on which Aristotle made several important observations, some attain a length of nearly two metres, the autenn::e included. The species found in European seas remains in deep water during the winter, and only visits the coast on the return of spring. Rocky localities are its favourite haunts. It subsequently deposits its ova, which ar·e of a beautiful red colour, whence their name of Coral. At this period more males arc taken than females, while after the spawning season the latter are most abundant. According to Risso a second copulation, followed by another production of ova, takes place in the month of August. The Palinuri are disseminated throughout all the seas of the temperate and intertropical zones, but are particularly abundant in the latter. Their shell is rough, covered (1) TILenus indicus, Leach; Scyllarus orientalis, Fa.b.; Rumph., :Mus., II, D.; Herbst., XXX, 1; Encyc., Atl. d'Hist. Nat., CCCXIV; Desmar., Consid., XXXI, 1. (!Z) Add Scyllarus antarcticus; f'abr., Herbst., xxx, 2; Rumph., Mus., 11, D. See the article Scyllare, Encyc. :Mcthouique. |