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



masticatory lobes are much smaller, and very narrow, and arise from a common lamellar 

 expansion lying outside the princijjal lobe. They were devoid of any armature, but it 

 may be that a few bristles have been originally affixed to their obtusely rounded 

 extremities. Neither the palp nor the exognath are distinctly defined from the basal 

 part but appear only as simple expansions of it. The palp has the form of a rather large 

 oval projection extended in the axis of the maxilla, and provided with numerous slender 

 ciliated sette on both edges, those of the outer edge being the longest and arranged in 

 several rows. The apex is evenly rounded and unarmed, whereas a row of very small 

 spine-like bristles is found along the inner edge, inside the slender ciliated setas. The 

 exognath is exceedingly small, constituting only a very slight lamellar expansion of the 

 outer edge, and provided with four densely plumose and somewhat fiexuous setae 

 increasino; in size towards the base. 



The branchial legs (fig. 3) are at first sight very unlike those in the two other known 

 genera, and comparatively fixr inferior in size, as also much more widely separate from 

 one another (see figs. 1, 2). They are very simple in structure, forming, as they do, 

 merely delicate membranous lamellse of oblongo-lanceolate form and slightly lobular at 

 the outer edge. There is no marked limit between basal and terminal part, nor are the 

 endopodite and exopodite distinctly defined, the epipodite being the only part distinctly 

 marked off from the plate. The inner edge of the plate forms a very slight and even 

 curve, and is bordered by a single row of slender setae, continued also on the narrowly 

 rounded extremity. Beyond the middle there is outside a very slight lobiform expansion, 

 the distal end of which is somewhat produced and separated from the terminal part of 

 the plate by a narrow incision. This expansion, which is quite smooth, may, from its 

 position, answer to the exopodite, and the part of the leg projecting beyond the above 

 mentioned incision of course corresponds to the terminal part of the endopodite in the 

 other NebaUidaB. The epipodite forms a narrow elliptical lamella affixed on the outer 

 side nearer to the base, and separated from the exopodite by another narrow incision. 

 It is connected to the leg by a narrow neck, and has the upper extremity considerably 

 more produced than the lower, the former even reaching somewhat beyond the base of 

 the leg. The substance of the branchial legs is very soft, almost parenchymatous, and 

 between the two investing cuticles there is accumulated a granular opaque mass disposed 

 in small patches, apparently coagulated blood. All parts of the leg, indeed, seem here 

 to be equally well adapted for respiratory purposes. Moreover, in the proximal part 

 several tliin muscular .bundles are seen, partly crossing each other and disappearing at 

 about the middle of the length of the lew. 



The pleopoda (fig. 4) arc rather powerful and, as in the other genera, composed of a 

 large lamellar basal part, to the end of which two unequal branches are affixed. The 

 basal part is oblongo-quadrangular in form and quite smooth, though projecting at the 

 end externally as an acute angle. Of the branches the outer one is uniarticulate and 



