1338 THE VOYAGE OF H.M.S. CHALLENGER. 



T7ie Mouth-Organs are placed at the lower hinder corner of the head, projecting 

 backwards below the perseon, and giving a very sinuous appearance to the hind margin 

 of the head. 



Epistome arched, broader than deep. 



Upper Li'p un symmetrically bilobed by a small cleft of the distal margin, one side 

 of the cleft being minutely furred. 



Mandibles. — The cutting edge shows six or seven little teeth ; the secondary plate 

 on the left mandible is narrow at the neck, then widening, but not nearly as broad 

 distally as the principal plate, the teeth eight or nine in number ; on the right mandible 

 there appears to be a secondary plate with the edge pectinate rather than denticulate ; 

 some small spines to the rear of the cutting plate run from the lower margin of the 

 trunk along a small ridge of the inner surface ; no molar tubercle or trace of palp could 

 be discovered ; the trunk of the mandible is comparatively large. 



Lower Lip very small, so far as could be made out. 



First Maxillas. — Inner plate (if rightly observed) smooth-edged, oval; the outer plate 

 appears to have seven or eight spines on the distal margin, the outermost the stoutest ; 

 there are also some cilia or setae on the plate ; the palp is broad for some distance from 

 the base, and has three very small spine-teeth and a short slender spine on the somewhat 

 oblique distal margin, and sometimes, if not always, a setule on the outer margin. 



Second Maxilla. — A single plate was doubtfully observed, with cilia on the rounded 

 distal margin and on the inner margin. 



Maxillipeds. — The first joint (or chin) short and narrow, the second joint also short, 

 expanding distally, the third joint much wider than the second, transversely oval, like a 

 rather deep dish, of which the width appears to be nearly twice the depth ; the distal 

 margin is sinuous, with a little central cleft, on either side of which the margin has three 

 little setules at a distance from one another ; there are also two small prominences, one 

 on each side of the central cleft, probably representing the distal margin of the inner 

 plate, which, as already suggested, would seem to be, not as usual distinct, but in 

 coalescence with the two outer plates. 



First Gnathopods. — The side-plates are not marked off from the segment, except in so 

 far as there is a narrow projection to which the limb is attached. In this respect all the 

 limbs of the perseon are alike, as also in the possession of gland-cells, to leave room for 

 which the muscles of the first joint are in no case extensive. The first joint wider than 

 any of the other joints and considerably longer than them all together, the margins 

 smooth ; the second joint not longer than broad ; the third a little longer than the 

 second ; with scarcely any free front margin, the hind margin smooth, the truncate distal 

 margin projecting behind the wrist, set round with six strong spines ; the wrist as long 

 as the hand and finger together, and more than twice the breadth of the hand, widening 

 a little distally, the convex front longer than the nearly straight hind margin, the hind 



