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



The mandibles (fig. 8) are comparatively small, and exhibit a structure rather differing 

 from that in the above described Cumacea. Thus the body of the mandibles is not, as in 

 these forms, navicular, but almost triangular, with two projecting angles, the outer pointed, 

 the inner obtusely rounded. By the outer angle the mandible is fixed to the inside of 

 the carapace at the point where the fissure limiting the frontal lobe terminates ; to the 

 inner the strong rotatory muscles are affixed, whose points of insertion are visible as a 

 number of lucid spots in the middle part of the carapace, symmetrically arranged on each 

 side of the middle line (see fig. 2). The anterior branch of the mandibles is comparatively 

 short and strongly incurved, with the cutting edge divided into two comparatively simple, 

 dentiform projections ; instead of the regular comb-like series of curved spines occurring 

 in most other Cumacea behind the cutting edge, only two simple bristles are found on 

 each mandible affixed close together. The posterior branch is very thick and massive, 

 with a large fluted molar surface. 



The first pair of maxilla? (fig. 10) exhibit the usual structure, with this exception, 

 however, that the posteriorly bent palp has but a single terminal seta. 



The second pair of maxillae (fig. 11) are comparatively small and want the dense 

 series of delicate bristles affixed to the inner edge of the basal part in other Cumacea, 

 instead of which there are only found three hook-like spines. 



The maxillipeds (fig. 1 2) are likewise rather feeble in structure, the basal part being 

 comparatively short and forming a more or less pronounced angle with the termiual part. 

 The masticatory lobe arising from the basal part is almost quadrangular, and bears at the 

 base a very strong anteriorly curved seta. Of the joints belonging to the terminal part, 

 the antepenultimate is, as usual, the largest, and exhibits along the inner edge a series 

 of short curved spines, provided at one of their edges with a few slender denticles 

 (fig. 14). Moreover, this joint has on the lower side numerous fine hair dike bristles, 

 partly arranged in fascicles, and at the outer corner a very long anteriorly curving seta, 

 densely ciliate at the outer part. Two similar, but somewhat shorter, setae are also 

 found originating from the succeeding joint. The last joint (see fig. 13) is very small, 

 sublinear, and provided at the tip with three bristles, one of which is quite short but 

 furnished with a few very long cilia on both edges. 



The branchial apparatus (see fig. 15) affixed to the base of these limbs, is less fully 

 developed than in most other Cumacea. The epipodite-plate is rather narrow and has 

 only five small digitiform gill-lobules, the largest of which is affixed at some distance 

 from the inner edge and points posteriorly. The anteriorly directed narrow division of 

 the apparatus, representing the modified exopodite, is considerably longer than the 

 epipodite-plate and terminates in a somewhat dilated lanceolate plate bordered by a very 

 thin and pellucid membrane. In conjunction with the corresponding plate this part 

 forms an elongated tube, which admits of being exserted from the tip of the pseudo- 

 rostral projection, and serves for the expulsion of the water introduced into the branchial 



