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



The form of the body (see PI. XVI. fig. 1) is very slender, though perhaps less so 

 than in Euphausia gracilis. 



The carapace is very similar in form and structure to that of Ewphauda gracilis, 

 with this exception, however, that the lateral denticle does not occur in the middle of 

 the inferior margin, having a somewhat posterior position, just above the point of 

 insertion of the third pair of legs. The rostral projection (see fig. 2) would appear to be 

 a trifle narrower and very acute. 



The caudal segments are on the whole more powerfully developed than in the 

 preceding species, the epimera being also larger and more projecting inferiorly. The 

 third segment in all the specimens forms a very conspicuous angle with that succeeding 

 it, giving to the tail in the middle, as it were, a geniculate appearance or gibbous character, 

 precisely as in several Caridea, for example the genus liipjwlyte. As in that genus, 

 moreover, an acutely pointed lappet is seen to project posteriorly from the dorsal face of 

 the third segment, arching over the base of the following segment, to which it is closely 

 applied when the tail is fully extended. The last segment, very elongate and slightly 

 compressed, is about as long as the two preceding segments taken together. The pre- 

 anal spine is nearly the same as in Euphausia gracilis, though in some examples a small 

 secondary tooth occurs at its base. 



The eyes (see fig. 2) are comparatively very small, Init have the cornea distinctly 

 expanded, whereby they acquire a more regular pyriform shape than in Euphausia 

 gracilis. 



The antennular peduncle (ibid.) exhibits a structure very similar to that of the 

 preceding species, with this exception, however, that a small Ijifid lappet (fig. 4) occurs 

 at the end of the basal joint above. 



The antennal scale (fig. 5) is rather large, reaching appreciably beyond the second 

 joint of the antennular peduncle ; it appears, too, relatively broader as compared with 

 that in Euphausia gracilis, and has an ovate form, with the apex obtusely truncate and 

 the outer corner unarmed. The basal spine is very slender, and, as in Euphausia 

 gracilis, denticulate along the inner edge. 



The oral parts and the legs would not seem to exhibit any essential diflerence from 

 those of EuphaMsia gracilis. 



The gills are comparatively more fully developed, being furnished ^\dth a greater 

 number of lobules, and the last pair (fig. 8) have five lobuliferous branches. 



The copulatory appendages to the first pair of pleopoda in the male (fig. 6), although 

 developed much as in Euphausia gracilis, still show well-marked specific difi"erences in 

 their structural details. Thus, the middle process exhibits a very extensive development, 

 being highly chitinised, and bent in the middle to a hook-shaped form, whereas the two 

 other processes are comparatively feeble in structure. The appendages of the second 

 pair of pleopoda (fig. 7) difi'er l)ut slightly from those in Euphausia gracilis. 



