neio Parasitic Copepods on Fish. 5 



Family Caligidae. 



Genus Caligus, Mlill. 



Caligus parvus^ sp. n. (PI. II. figs. 1, 2.) 



This species was found very frequently on the inner surface 

 of the operculum and also free on the surface of Tetrodon 

 ohlongus from Bombay Harbour : they were often seen 

 actively moving about, and were of a pinkish colour, both 

 sexes being equally common. I have been unable to place 

 tliis species with any known ones, though it bears a resem- 

 blance to C. abbreviatiis, Kr., in form, but differs in detail 

 (PI. II. fig. 1). 



In the female the cephalothorax is almost circular, slightly 

 broader than long, equalling in length the remainder of the 

 whole ; it narrows anteriorly, where it unites with the frontal 

 plate, being evenly rounded at the posterior angles. The 

 frontal border is narrow, concave in the centre, and bears 

 small lunul^e in the outer third. Tlie first joint of the anterior 

 antenme is short and thick, with about twenty short plumose 

 seta3 on the front border ; the second joint is shorter and 

 carries fine hairs at the end. Posterior antennce are placed a 

 short distance behind the frontal plate, are three -jointed and 

 of moderate size. Hamulus suhsidiarius anterior is in the 

 shape of a short hook with a dilated base. First maxilliped 

 is very slender, ending in two small claws, the outer being 

 the longer. Second maxilliped very large and characteristic, 

 the end claw being extremely strong and thick, the basal 

 joint having a large process to which the other is opposable. 

 Furcula is small, with very short blunt branches, spreading 

 but slightly. 



The first of the swimming-feet (perfeopoda) has a short 

 basal joint, elongated second, and the third terminating in 

 three short bristles, with four elongate plumose seta3 on the 

 posterior border, the one at the angle being the longest. 



Genital segment is square, with rounded angles. The ab- 

 domen is very short, carrying extremely short caudal plates ; 

 these are as broad as long, and are provided with three long 

 plumose setfB terminally and two minute short hairs on the 

 outer border. 



Length 8*4 millim. 



Male. — This has the after portion of the body more elon- 

 gated, the posterior angles of the genital segment produced, 

 carrying two fine hairs, the caudal plates are longer ; but 

 the most characteristic change is in the great development of 

 the accessory hook, probably for better holding the female. 



Length 2*3 millim. 



