246 THE VOYAGE OF H.M.S. CHALLENGER. 



lies ; in this hollow the ophthalmopod rests, protected on the inner side from contact with 

 its fellow by the thick and bushy prosartema, and on the outer by the thickly-set fringe 

 of hairs on the margin of the joint : the second joint is short, about one-third the length of 

 the first, longitudinally arched above and curved below ; fringed on the inner and outer 

 sides with short, thickly-packed hairs : the third or terminal joint is very short, scarcely 

 half the length of the second, and terminates in two short, subequal, multiarticulate 

 flagella, which are only about twice as long as the third or terminal joint of the 

 peduncle. 



The second pair of antennas (c) has a very short peduncle, and all the joints articulat- 

 ing ; the first joint is short, and on the inner side, just in front of and immediately before 

 the mouth, it carries a phymacerite in the form of a small, circular, membranous plate ; the 

 next two joints, closely compressed together, are short and thick, and carry at their upper 

 extremity a large scaphocerite, of which the outer margin is rigid, long, and terminating 

 in a sharp point ; the inner side is foliaceous, broad at the base, slightly tapering and 

 rounded at the extremity, and reaches beyond the external point ; the whole plate 

 is of extreme tenuity and is longitudinally and obliquely ribbed, the lines increasing 

 in number suddenly as they approach the margin, where they appear in connection 

 with the several hairs of the fringe. The terminal joints of the peduncle are short, 

 of small diameter, and are lodged on the under surface of the scaphocerite. The 

 terminal flagellum is slender, flexible, and rather longer than the animal. 



The mandible (d) is short and broad, having a large molar tubercle and a large, 

 squamous, Inarticulate synaphipod. 



The first pair of siagnopoda (e) is three-jointed, two of the joints being foliaceous, 

 and terminally fringed with spines, whereas the third is biarticulate, cylindrical, and 

 continuously tapering. 



The second pair (f) consists of three joints, of which the first two are biramose and 

 foliaceous, and the third cylindrical and irregularly truncate ; externally there is a broad, 

 flat, mastigobranchial plate, anteriorly and posteriorly produced, and fringed with cilia. 



The third pair of siagnopda (g) consists of five or six joints, of which the first two 

 are biramose and foliaceous, increasing in size as they proceed distally ; the third and 

 following joints are cylindrical and gradually taper to the extremity. Attached to 

 the second joint or basis is a large squamiform plate (basecphysis) projecting con- 

 siderably forwards, and fringed with cilia, while attached to the first joint or coxa is 

 another squamous plate that is broader than the preceding, projects backwards, and is 

 fringed with fine and soft cilia. 



The first pair of gnathopoda (h) is subpediform, having the meros long, broad and 

 marginate: the propodosis reflexed, and, like the dactylos, which is spatuliform, is fringed 

 with a mat of hairs and rests against the inner margin of the meros : the basis carries a 

 long two-jointed ecphysis, the first joint of which is short, and the second long, multi- 



