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Show 1899.] PARASITIC COPEPODA ON FISHES. 473 G. 6. DICHELESTIUM Herm. Head obtuse. Body elongated, consisting of four distinctly articulated segments, without dorsal plates. Genital segment oval, long. Abdomen oblong, with two minute caudal plates. Anterior antennae slender, with 8 joints. Posterior antennae large, cheliform at the end. The first two pairs of thoracic limbs small, two-branched, the third lamellar, the fourth suppressed. (1) DICHELESTIUM STURIONIS. 2 cf. Dichelestium sturionis Herm. Me'm. Apterologique, 1804, p. 125, pl. v. fig. 5. „ Nordm. Mikrogr. Beitrage, 1832, p. 41. M.-E. Hist. Nat. Crust, iii. 1840, p. 483, pl. xxxix. fig. 4. » -> H. Eathke, M e m . Acad. Sci. St. Petersb. iii. 1837, p. 401. » » V. Ben. Ann. Sc. Nat. vol. xxi. 1854, p. 96. In Coll. Brit. Mus. Host: gills of Acipenser sturio. G. 7. LONCHIDIUM Gerst. (Kroyeria V. Ben.) _ Head broad, with two long movable styliform processes projecting backwards. Three distinct free thoracic segments without lobes on dorsal plates. Genital segment very long, oval shape. Abdomen elongated, simple, terminating in two lanceolate setose caudal plates. Anterior antennas 8-jointed. Posterior antennas short, cheliform; the second maxillipeds are large and uncinate. AH four pairs of thoracic limbs are biramose, each branch having three joints furnished with plumose setas. 1) LONCHIDIUM LINEATUM. 2 • Kroyeria lineata V. Ben. Bull. Acad. Boy. Belg. 1853 t xx pt. i. p. 94. » » V. Ben. Bech. sur les Crust. Belg. 1861, p. 149, pl. xxii. » » C. Claus, Beitrag Parasit. Crust. 1858, p. 24, pl. ii. Host: gills of Galeus canis. (2) LONCHIDIUM ACULEATUM. 2 • Lonchidium aculeatum Gerst. Archiv. f. Natur. 1854 p. 189 Host: "Shark." Atlantic. G. 8. CLAVELLA Oken. Head small, rounded ; thorax biarticulate, without dorsal plates or lateral processes. Genital segment very long (5 or 6 times as long as cephalothorax). Abdomen short. Caudal plates minute Anterior antennas 6-joiuted. Posterior antennae uncinate. Second |