66 THE VOYAGE OF H.M.S. CHALLENGEE. 



of ciliated setae. No trace of any apical urticulatiou occurs either iu this or in other 

 ■genera of Euphausiida?. 



The anterior lip (see PI. XI. fig. 6, I ; PL XII. fig. 7) forms a triangular fleshy 

 l^rominence, placed between the basal parts of the antennae, and to some extent concealing 

 the inner ends of the mandibles. It projects anteriorly into a sharp point, and exhibits, 

 on the lower face, a thin transverse membrane, doubling over the 1iody from behind, and 

 deeply incised in the middle. 



The posterior lip (PI. XII. fig. 8) is formed of two membranous lobes, of triangular 

 form, separated by a deep incision almost to the base. The inner edges of these lobes 

 are finely ciliated throughout. 



The mandibles (see PI. XL fig. 6, m ; PL XII. fig. 9) have a rather strong, curved body, 

 with the masticatory part securiform-expanded. The cutting edge is armed wdth strong, 

 dentiform projections, somewhat difi"erent in shape on the two mandibles, and in recent 

 specimens of a vivid reddish-brown colour. The molar prominence is well defined, and 

 has a rather extensive fluted surface. The palp (PL XII. fig. 11; PI. XITl. fig. 10; 

 PL XV. figs. 5, 15) scarcely exceeds the body of the mandible in length, and presents a 

 somewhat deviating form in the difi"erent species. It consists, as usual, of three joints, 

 of which the median is the largest, and is furnished with a moderate number of ciliated 

 bristles, those on the last joint sometimes assuming the character of spines. 



The first pair of maxilte (PL XII. fig. 12; PL XIII. fig. 11 ; PL XV. figs. G, IG) exhibit 

 a somewhat difi"erent form from that observed iu the other families of Schizopoda, being 

 furnished with both a well developed palp and an exognath. The basal part is divided 

 into two imperfectly defined segments, both of which 23roject inward as well marked 

 masticatory lobes. Of these lobes, the outer one is by far the stronger, and abruptly 

 truncate at the end, wdiich is furnished with a row of strong spines as well as a series of 

 delicate bristles. The inner or l)asal lobe is mcjre decidedly membranous in consistence, 

 and somewhat linguiform, fringed along the anterior margin and at the rounded tip with 

 a row of strong setse, diminishing in length outwards. The palp, issuing from the distal 

 segment of the basal part, and directed forward, consists of a single lameUiform joint, 

 beset along the inner edge and tip with a double row of strong, ciliated bristles. Finally, 

 the exognath forms a rather large but very thin and pellucid plate of an oval, or rather 

 elliptical form, affixed to the outer side of the proximal segment of the basal part, and 

 fringed at the rounded anteri(n' end with a few short bristles. 



The second pair of maxUte (PL XII. fig. 13 ; PL XIII. fig. 12 ; PL XV. figs. 7, 17) 

 also diS"er considerably in their general appearance from what is observed in other 

 Schizopods. Both of the masticatory lobes are very sliort and broad, and proceed directly 

 inward at right angles. They are slightly cleft in the middle, forming together four 

 densely setiferous lobes. The palp, as in the first pair, consists of only a single rather 

 large, lamelliform, joint, issuing from the end of the basal part and beset with bristles. 



