OCR Text |
Show 92 CRUST A<.n~A. unique in this order-the internal extremity of the third joint of the peduncle is provided with a little articulated thread. It distin. guishes the GAMMARus, Lat., Where the four anterior feet have the form of small forceps, the movable toe folding beneath. The species best known and the type of this subgenus is the Cancer pulex, L.; Squillu pulex, De Geer, Insect., VII, xxxiii, 1, 2. It inhabits brooks, etc. The other species are marine(!). The antenn::e of the following, as in all the other Amphipoda, are simple or without appendages. MELITA, Leach. The second pair of feet, in the male, terminated by a large com. pressed forceps, the toe folding under its internal surface; the an. ' tenn::e nearly equal in length; a small foliaceous appendage on each side of the posterior extremity of the body(2). MERA, Leach. The second feet in the males terminated as in the Melit::e, but the toe folds under the inferior edge of the forceps and is not concealed. The superior antenn::e are longer than the inferior, and the foliace· ous appendages of the posterior extremi1y of the body are want· ing(3). AMPHITHOE, Leach. The four anterior feet nearly similar in both sexes; the penultimate article or hand proper, ovoid( 4 ). PHERusA, Leach. The Pherusre only differ from the preceding subgenus in the hand of the forceps, which is filiform( 5). There, the peduncle of the antenn::e is only composed of two joints, ( 1) See Desmar., Consid., p. 265, 267. (2), C~ncer palma:us, Montag., Trans., Lin. Soc., VII, p. 69; Encyclop. Method., Atl. d H1st. Nat., CCCXXXVI, 31: Desmar., Consid., XLV, 7. (3) Cancer gammarus grosimanus, Montag., Trans. Lin. Soc., IX, iv, 5; Desmar. Consid. p. 264. ( 4) C~ncer rubricatua, Montag., Trans. Lin. Soc., IX, p. 99; Encyclop. Method., Atl. d'H1st. Nat., CCCXXXVI, 33; Desmar., Consid., XLV, 9;-0niscus cancellw, Pall., Spic. Zool. Fascic., IX, iii, 18; Gammarua cancel!Jus, Fab. (5) Pheru.~a fusicola, Leach; Trans. Lin. Soc., XI, p. 360; Desmar., Conaid., p. 268. AM:PIUPODA. 93 h third being so small as to be confounded with those of the stem, t eforming that of the base; the superior are longer than the infe-o; All the feet are simple, or without forceps. Such is rtor. · DEXAMINE, Leach( I). In those, the movable toe of the two forceps is hi-articulated. 'fhe antennre are of equal length. LEuooTHoE, Leach. •rhe antennre short, their peduncle formed of two joints; the four anterior feet terminated in a stout forceps; toes of the two first bi~articulated; those of the second pair consisting of a single and long join~~l). CERAPUS, Say. Large antennre, the peduncle consisting of three-the superioror four-the inferior-joints; the two anterior feet small, with a uni-articulated toe; the two following terminating in a large triangular, smooth, dentated hand, with a hi-articulated finger. Ceraphus tubularis, Say, Journ. Acad. Nat. Sc. of Philad., I, iv, 7-11; Desmar., Consid., XLVI, 2. It inhabits a little cylindrical tube, and in this respect approaches the subsequent subgenus. Very common at Egg Harbour, New Jersey, among the Sertulari::e on which it appears to feed. Finally, the inferior antenn::e, sometimes much larger than the superior, their stem consisting at most of four joints, have the form of feet, and appear to serve, at least occasionally, as organs of pre-hension. Here the second feet are terminated by a large forceps. PonooEnus, Leach. Eyes very prominent(3). JAssA, Leach. Eyes not prominent( 4). There, neither of the feet is terminated by a large forceps. (1) Cancer gammarus apinoaus, Montag., Trans. Lin. Soc., XI, p, 3; Desmar., Consid., XLV, 6. (2) Cancer articuloaua, Montag., Trans. Lin. Soc. VU, 6; Desmar., Consid., p. 263, XLV, 5. {3) Podoctrus variegatm, Leach, Trans. Lin. Soc., XI, p. 361; Desmar., Consid. p. 269. (4) Jassa pulcltella, Leach, lb., p. 361; Desmar., Conaid., p. 269. |