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



and fragile structure, so as only with great difficulty to be separated from the sur- 

 rounding parts. It consists as usual of two membranous lobes connected at the base, 

 each lobe exhibiting an irregular oval form, with the inner corner produced to a small 

 somewhat incurved point. The inner edge of the lobes and part of the outer are 

 finely ciliated. 



The mandibles (figs. 8, 9) exhibit a structure essentially differing from that of all other 

 known genera of Cumacea. They are not very strong, with the body oblong and on the 

 inner side forming a rounded expansion, to which the chitinous tendon of the rotatory 

 muscles is affixed. The anterior branch (see fig. 10), forming the direct continuation 

 of the body, is slightly incurved and somewhat compressed, terminating in a strongly 

 dentate, oblique, cutting edge. On the right mandible this edge is simple and armed 

 with six teeth, increasing in size internally ; on the left mandible, on the other hand, 

 the edge appears double, a secondary bidentate plate occurring in juxtaposition to the 

 principal plate. At some distance posterior to the cutting edge there is a densely 

 crowded series of strong denticulate spines, six on the right and four on the left 

 mandible. The posterior branch or the molar process is very unlike that in other 

 Cumacea, constituting an exceedingly narrow and somewhat flexuous styliform projection, 

 terminating in a sharp point and bearing a few small denticles along the anterior edge. 

 The first pair of maxillae (fig. 11) are unusually strong, with the basal parts very 

 massive and partly connected at the base. The outer masticatory lobe is rather broad 

 and strongly incurved, with the extremity abruptly truncated and armed with numerous 

 powerful spines, some of which are finely dentate on one of the edges. The posterior 

 masticatory lobe is considerably smaller and somewhat tapering, with the extremity 

 narrowly truncate and armed with five spines, the three median rather strong and 

 densely ciliated. The palp, which as usual points straight backwards, is very slender 

 and elongate, and bears at the tip two unequal setae. 



The second pair of maxillae (fig. 12), unlike those of the first pair, are poorly 

 developed, forming simple membranous plates, without any trace of the usual bifid 

 palp. The inner slightly produced part, representing the masticatory lobe, is provided 

 with eight bristles, the posterior of which is somewhat removed from the rest and 

 densely ciliated. 



The maxillipeds (fig. 14) are likewise imperfectly developed, the terminal part 

 appearing at first sight to be represented by only a single oval and lamellar joint, 

 finely ciliated along the outer edge, and provided along the inner with a few email 

 bristles. On closer examination, however, a very small terminal joint is found affixed 

 to the inner corner. This joint (fig. 14a) is conical in form and provided with only a 

 single small apical bristle. The basal part, which about equals in length the terminal, 

 exhibits at the end, on the inner side, an imperfectly developed, rounded, masticatory 

 lobe, with two ciliated setae at the end, and is, moreover, provided on the inner edge 



