CALIGITS PELAMYDIS. 59 



it might be readily passed over for that species. The 

 abdomen is two-jointed and slightly shorter than the 

 genital segment. The first joint is comparatively short 

 and about equal to half the length of the second joint. 

 The furcal joints are short and broad and nearly as 

 long as the first abdominal segment. The specimen 

 was not dissected, but so far as could be made out 

 from the examination of the entire animal the various 

 appendages are almost identical with those of the 

 female. The fourth pair of feet of the female, which 

 are quite distinct from those of any of the other 

 members of the genus, form a quite reliable distin- 

 guishing character. The fourth pair of feet of the 

 male now illustrated are identical with those of the 

 female. The living male was dark red in colour, and 

 it was easily detected running over the inner surface 

 of the operculum of its host. Length 2*9 mm. 



Habitat. — Parasitic on the belted bonito, Pelamys 

 sarda, and the mackerel, Scomber scombrus. Plymouth, 

 on the inside of the gill-covers of mackerel (Bassett- 

 Smith). Aberdeen (T. Scott). Irish Sea (A. Scott). 

 Kroyer's specimens were obtained on Pelamys sarda. 



Distribution. — G aligns yelamyclis has apparently a 

 wide distribution in the seas of Europe. C. B. 

 Wilson describes this species in his work on ' North 

 American parasitic Copepocls,' and mentions the name 

 of its host, but does not state if the fish was captured 

 in American waters.* 



We think there can be no reasonable doubt that the form 

 obtained by Kroyer on Pelamys sarda, and described by him 

 in the work referred to under the name of Caligus 

 pelamydis, is identical with that from the mackerel; the 

 general structure of the animal, the shape of the sternal fork 

 and of the genital segment, and the structure and armature 

 of the fourth pair of thoracic legs, are similar in both forms. 



* See Part I (The Caliginse), p. 594. 



