new Parasitic Copepods on Fish. 363 



terminal joint of the outer with four ciliate hairs, increasing 

 in lengtli from without inwards ; a longer one is seen from 

 the inner side of the penultimate joint ; the inner paddle has 

 six plumose hairs on the last joint. 



Hamulus with a dilated base and a short, thick, curved 

 claw. 



Fourth perceopods, rising from an elongated posterior tiioracic 

 segment, are robust in form, four-jointed, the basal joint biing 

 of a long oval shape, the three last of nearly equal size, the 

 first two each aivins: off a strono' claw ; the last has three 

 placed close together. 



Genital segment heart-shaped, having a constriction above, 

 giving the appearance of a double posterior thoracic segment ; 

 the whole length equals about two thirds that of the cephalo- 

 thorax; the rudiments of the fifth pair of limbs are visible 

 on the posterior rounded border. 



Abdomen slightly longer than the last segment; it is very 

 constricted at its origin, becoming rapidly broader to near the 

 extremity, where there is another constriction, forming a joint 

 as long as broad. 



Caudal plates longer than broad, giving off three short 

 terminal ciliate hairs and two smaller ones on the outer side. 

 Length 7-10 millim. 



Male. — This is smaller, and has the cephalothorax more 

 oval in shape ; the genital segment is narrower, terminating 

 posteriorly in two stout spines ; two fine hairs are also seen 

 on the outer border ; the abdomen is made up of a short 

 broad joint and a second oblong one ; the caalal plates are 

 rather large, with the inner borders finely fringed with hairs, 

 'i'he second antennce have the last joint reduced to a short 

 though rather powerful hook, and the hamulus anterior 

 remains of the same size as in the female, which is unusual. 

 Length 5 millim. 



Caligus tenax, Heller. (PL XL fig. 3.) 



As the male of this has not yet been described, 1 here take 

 the opportunity of putting it on record. Heller found speci- 

 mens of the species on Caranx carangis, Brazil ; in these 

 eastern seas I have taken very large numbers from the gill- 

 chambers of various species of Caranx found at Trincomalee, 

 Colombo, Muscat, and Aden, the males being fairly plentiful ; 

 these specimens were seen to have the abdominal segment 

 generally shorter than those described by Heller *, but agree 

 in detail of structure, except that on careful examination the 



* ' Reise der Fregatte Novara,' pp. 172-173. 



