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Show 102 CRUSTACEA. In some, where the tail always consists of six segments, the len tb of the inferior antennre never surpassed the half of that of the bo~ We will begin with those whose mandibles, as usual, are by; slightly, or in no degree salient. u CYMOTHOA, Fab. The antennre nearly equal in length; eyes scarcely apparent; last segment of the tail forming a transverse square; the two pieces ter· minating the lateral fins, linear, equal and styliform( 1 ). loTHYOPHILus, Lat.-Nerocila, Livoneca, Leach. The antennre, equal in length, and but slightly visible eyes; the last segment of the body almost triangular; the two pieces termi. nating the lateral fins in the form of leaflets or laminre, the exterior of which is largest in the N erocilre, and of the size of the other in Livoneca(2). In the four following subgenera the superior antennre are mani· festly shorter than the inferior. In several, as in Cymothoa, all the feet are terminated by a small stout, and strongly curved nail; the last eight are not spinous; th~ eyes are always separated and convex. They form three genera in the system of Leach, but may be united in a single subgenus under the common denomination of one of them, or the ' CANOLIRA, Leach.-Anilocra, Olenc·ira, Ejusd. The laminre of the fins in the Olencirre(3) are narrow and armed with ~pines. In the Anilocrre( 4) the external leaflet of the same parts 1s longer than the internal; the reverse is the case with the Canolirre( ~)· The eyes, besides, are but slightly granulous while in the precedmg that disposition is evident. In the three following subgenera, the second, third and fourth feet alone ~re termi~ated by a strongly curved nail, and the last eight are spmous. 1 he eyes are usually but slightly convex· they are large and converge anteriorly. ' F (1)t hO ymtho thoa res·t rum, Fab. ; Desmar. ' Consid. ' XLVI' 6, 7·, -0 . z·m bri ca t a, Fa b . or e o er spec1es, see Desmar., loc. cit . . (2) See Desmar., op. cit., p. 307, genera Nerocila and Livoneca and various spe· c1es of Cymothoae of Uisso, P· 310, 311. ' (3) Desmar., Consid., p. 305. (4) Desmar., Consid., .llnilocredu Cap, XLVIII, 1. (5) Desmar., Consid., p. 305. ISOPOD A. 103 .iEGA, Leach. 'fhe two first joints of the superior antennre very broad and compressed, while in the two subsequent subgenera they are almost cy-lindrical( 1 ). RooiNELA, Leach. The Rocinelre differ from the JEgre, as just stated, in the form of the two first joints of their superior antennre, but otherwise approach them, as in their large eyes which approximate anteriorly(2). The CoNILIRA, Leach, Resembles Rocinela in the antennre; but the eyes are smaller and distant, and the edges of the segments nearly straight and not falciform nor prominent( 3). The last subgenus, among those of this section in which the an-tennre are placed on two lines, where the tail is composed of six segments, and the inferior antennre are always short, is distinguished from all the preceding by strong and salient mandibles. It is the SvNonus, Lat., A subgenus established on a single species( 4). In those that follow, the tail is usually composed of but five segments. The length of the inferior antennre is more than the half of that of the body. CrROLANA, Leach. The tail composed of six segments( 5). In the N .ELOOIRA, Leach, It consists of but five. The cornea of the eyes is smooth(6). EuRYDicE, Leach. Similar to Nelocira in the number of caudal segments, but removed from it by the granulous eyes(7). (1) Desmar., Consid., p. 304, .!Ega entailUe, XLVII, 4, 5. (2) Desmar., Consid., p. 304. (3) Desmar., Consid., p. 304. (4) See Encyc. Method., article Synodua. (5) Desmar., Consid., p. 303. (6) Desmar., Consid., p. 302; Nelocire de Swaimon, XLVIII, 2. (7) Desmar., Consid., p. 302. |
