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Show 468 MR. P. W. BASSETT-SMITH ON [Apr. 18, placed laterally, the second small, central; third pair large, spreading. Genital segment as large as the cephalothorax. Abdomen small, hidden. Thoracic limbs very rudimentary. (1) PERISSOPUS DENTATUS. 2- Perissopus dentatus Stp. & Liitk. Bidrag til Kundskab, 1861, p. 393, pl. xii. fig. 25. communis Bath. Proc. U.S. N. H. Mus. 1887, x. p. 560. Hosts : Carcharias sp. and C. obscurus. (2) PERISSOPUS ARMATUS. 2 • Lepidopus armatus Dana, Proc. Am. Acad. Arts & Sc. 1843, p. 60. Perissopus armatus Stp. & Liitk. Bidrag til Kundskab, 1861, p. 394. Host: Mustelus vulgaris. Bio Janeiro. (3) PERISSOPUS INCISUS. 2 • Chlamys incisus V'. Ben. Bull. Acad. Boy. Belg. 1892, p. 227, pl. ii. fig. 1. Host:-? Bay of Dakar, Senegal. Family III. DICHELESTIID^. The body is as a rule elongated, and the head small. The free thoracic segments are simple (only exceptionally seen with dorsal plates). Abdomen generally rudimentary. The anterior antennae are slender, mostly with many joints up to 15, rarely short with only 2 or 3 joints. Posterior antennae unciform or cheliform, generally projecting beyond the border of the cephalothorax. Mouth-parts as in Caligidce. Generally there are four pairs of thoracic limbs, frequently short, stump-like, or suppressed, or the posterior ones transformed into lamellar plates. Eye single, median, or absent. Genital organs as in Caligidce. Male and female only relatively different. The majority are capable of a certain amount of locomotion. G. 1. ANTHOSOMA Leach. Head oval, infolding, broadest posteriorly. Two distinct dorsal thoracic plates, and three pairs of large overlapping ones which represent the limbs. Abdominal segment small, terminating in two long caudal appendages. Anterior antennae long, multi-articulate. Posterior antennae unciform, very large, and projecting. Bostrum elongated. (1) ANTHOSOMA CRASSUM. 2- Caligus crassus Abgd. M e m . de Copenhag. 1794. „ imbricatus Bisso, Hist. Nat. Crust. Nice, 1816, p. 162, pl. iii. fig. 13. |