CALIGUS EAPAX. 49 



maxillipeds moderately stout. Sternal fork con- 

 spicuous, its rami narrow, tolerably elongated, slightly 

 divergent, and with the ends blunt-pointed. 



The first three pairs of thoracic legs short, biramose, 

 with both rami three- j ointed ; fourth pair one- 

 branched, basal joint elongated, tolerably stout, and 

 furnished with a small seta on the upper distal angle ; 

 end portion narrow and consisting of two subequal 

 joints, the first with the outer distal angle slightly pro- 

 duced and bearing a short spiniform seta, the other 

 with a spiniform seta near the middle of the outer 

 margin and four at the apex, the second from the 

 inside being elongated, slightly curved and claw-like. 

 The fifth pair rudimentary, each consisting of a 

 minute plate bearing a few small setae, and situated 

 near the postero-lateral angles of the genital segment. 



Length about 5 to 6 mm. Egg-strings not greatly 

 elongated. 



Male. The male is smaller than the female ; the 

 form of the carapace is somewhat similar in the two 

 sexes, but the genital segment is narrow and scarcely 

 wider than the preceding one. Abdomen as long as 

 the genital segment and composed of two joints, the 

 end joint being about twice as long as the other. 

 Caudal rami as in the female. 



The antennas and second maxillipeds are stouter 

 than those of the female, and are provided with 

 stronger terminal claws ; the other mouth-appendages 

 and the thoracic legs are similar to those of the 

 female. Length about 4 to 5 mm. 



Habitat. Found parasitic on various fishes, but 

 perhaps most frequently on Gadoids. It is also not 

 uncommon in plankton collections, among Calanoids 

 and other free- swimming organisms ; both males and 

 females are frequently captured in this way, and the 

 latter are generally without egg-strings. Owing to the 

 wandering habits of this Caligus there is scarcely 

 a fish in our seas on which it may not at one time or 

 other be found. 



VOL. i. 4 



