40 BIUTLSH PARASITIC COPBPODA. 



of the inner margin of the first joint, and two smaller 

 setae from near the middle of the second joint, while 

 from the proximal half of the terminal claw there 

 spring two slender bristles of unequal length, the 

 longer one extending considerably beyond the end of 

 the claw. 



Thoracic legs somewhat similar in structure and 

 armature to those of Bomolochus solese. Length about 

 1*3 mm. 



The species is colourless, with the exception of a 

 slight chalky whiteness along the alimentary tract. 



Male. — The male of Bomolochus onosi differs little 

 from the female, except that the terminal claw of the 

 second maxillipeds is more powerful, more evenly 

 curved, and has its inner edge minutely dentated. 



Habitat. — Found parasitic on the inner surface of 

 the gill-covers of four-bearded and five-bearded rock- 

 lings, Onos (Motella) cimbrius and Orios (Motella) 

 mustelus. Firth of Forth, Moray Firth, and Bressay 

 Shoal, east of Shetland (T. Scott). 



The species described above has a close resemblance to 

 Bomolochus solem, and might easily be mistaken for it. The 

 most obvious difference is perhaps in the form and armature 

 of the posterior maxillipeds; this difference is so marked that 

 it may be detected even without dissection, when the creature 

 is viewed from the ventral aspect with the aid of a hand-lens. 



3. Bomolochus zeugopteri T. Scott. 

 (Plate I, fig. 2; Plate III, figs. 8, 9.) 



1902. Bomolochus zeugopteri T. Scott. (114) p. 290, pi. xiii, figs. 23-25. 



Female. — Cephalic segment equal to the combined 

 length of the next three segments, broadly rounded in 

 front, rostrum not very prominent ; the next segment 

 nearly as wide as the preceding one, and about half as 

 long, the remaining segments narrower and shorter. 

 Abdomen narrow, the genital segment about as long 

 as the combined length of the next three segments, 

 the last two segments subequal and rather shorter 

 than the second one. Caudal rami short. 



