1899.] PARASITIC COPEPODA ON PISHES. 459 



articulate and lobed laterally. Frontal plates conspicuous. An- 

 terior antennae biarticulate. Posterior antennae unciform, with a 

 spur on base of the terminal joints. Rostrum elongated ; palp ar- 

 ticulated ; second maxilliped with short toothed end-claw. Fourth 

 thoracic ring without dorsal plates. Grenital segment elongated. 

 Abdomen short. Caudal plates small, with plumose setae. All 

 the thoracic limbs biramose, first three biarticulate, fourth uni- 

 articulate. 



(1) ]S"bssiptjs oeibntalis. 



Nessipus orkntalis Heller, Eeise d. Xovara, 1865, p. 194, pi. xviii, 

 fig. 2. 



Host : gills of Prionodon menisorrah. Java. 



(2) NeSSIPUS CETPTtTETJS. 



Nessipus crypturus Heller, Reise d. Novara, 1865, p. 196, pi. 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 Liitken, and by 

 Gerstacker — (1) Those in which the fourth pair of thoracic limbs 

 are biramose and biarticulate, like the first three pairs, and 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, Deinoleus, 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 foi'ms 

 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 Beneden ^ 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, 

 pi. I. fig. 1. 



1 Bull. Acad. Roy. Belg. vol. xxiv. 1892, p. 245, pi. i. 



