84 BRITISH PARASITIC COPEPODA. 



Second maxillipeds armed with strong terminal claws. 

 Thoracic legs four pairs, all biramose ; both rami of 

 the first pair two -jointed, the outer ramus tolerably 

 elongated, but the inner very small ; both rami of the 

 second and third pairs composed of three joints, but in 

 the second the rami are nearly of equal length, with the 

 end joints very small, while in the third the outer ramus 

 is distinctly shorter than the inner. These three pairs 

 of thoracic legs all liberally supplied with densely 

 plumose setae. In the fourth pair the outer ramus 

 stout, and composed of sub-equal joints, both the first 

 and second joints having a strong and slightly-curved 

 spine on their outer distal angle, while the end joint 

 has three similar spines on its outer margin, and three 

 or four small ones on the inner margin; the inner 

 ramus, which is situated close behind the outer, small, 

 and composed of two subequal joints ; the basal joint 

 of the fourth pair also tolerably large, and gibbous 

 below. Length about 11 '5 mm. 



Male. The male, though somewhat similar to the 

 female in its general appearance, is smaller, and the 

 second maxillipeds are more powerfully clawed ; and 

 while the genital segment is only about half as large, 

 the abdomen is rather longer than in the female. The 

 postero-lateral corners of the penultimate segment of 

 the abdomen are angular, while the anal segment has 

 a subquadriform outline. The caudal rami are furnished 

 with four setae longer and more densely plumose than 



O / I 



in the female. Length about 9 mm. 



Habitat. Parasitic on the tunny, Orcynus thynnus, 

 Plymouth (Bassett- Smith). Outer Hebrides (Dr. Alex. 

 Bowman). We are indebted to Dr. Bowman for speci- 

 mens of this interesting species. 



Distribution. European seas. 



The species is not an uncommon one on the tunny. 



