OCR Text |
Show 1899.] PARASITIC COPEPODA ON FISHES. 459 articulate and lobed laterally. Frontal plates conspicuous. Anterior antennae biarticulate. Posterior antennae unciform, with a spur on base of the terminal joints. Rostrum elongated ; palp articulated ; second maxilliped with short toothed end-claw. Fourth thoracic ring -without dorsal plates. Genital segment elongated. Abdomen short. Caudal plates small, with plumose setae. All the thoracic limbs biramose, first three biarticulate, fourth uni-articulate. (1) NESSIPUS ORIENTALIS. Nessipus orientalis Heller, Beise d. Novara, 1865, p. 194, pl. xviii. fig. 2. Host: gills of Prionodon menisorrah. Java. (2) NESSIPUS CRYPTURUS. Nessipus crypturus Heller, Beise d. Novara, 1865, p. 196, pl. xviii. fig. 4. Host: gills of Zygcena malleus. Java. NOGAGUS Leach. Only male forms of this genus have been described, which have been divided into two groups by Steenstrup and Liitkeu, and by Gerstacker-(1) Those in which the fourth pair of thoracic limbs are biramose and biarticulate, like the first three pairs, aud also having the abdomen with two joints. (2) Those in which the fourth pair are biramose, but with only a single joint, the first three being biramose and biarticulate; abdomen of a single joint. The first are in many cases proved to be the male forms of various species of Pandarus; the second are most probably the males of species of Nessipus, Demoleus, Ecthrogaleus, and Dinematura. I have here enumerated the species which have so far been described, bub as a distinct genus Nogagus should not appear. When taking these parasites from Sharks, among specimens of Pandarus, some of the male forms are almost invariably found. As has been pointed out by Thomson, the amount of pigment in them varies very considerably, from almost black to light yellow; but no observations have been made as to whether the lighter forms are mostly found on the white undersurface of the fish, and the dark forms above, a point which would be interesting to elucidate. The Nogagus angustatus represented by Van Benedenl with a male attached would appear to be a species of Dysgamus, though the characters of the thoracic limbs are incompletely described, and poorly shown in the plates. DIVISION I. Nogagus latreillii Leach,Diet, des Sci. Nat. vol. xiv. p. 536 (1819). „ grandis Stp. & Liitk. Bidrag til Kundskab, 1861, p. 338, pl. x. fig. 1. 1 Bull. Acad. Roy. Belg. vol. xxiv. 1892, p. 245, pl. i. |