5. Diastylis rostrata, (Goodsir). 
(PI. XXXIX.) 
Alauna rostrata , Goodsir, Edinburgh New Phil. Journal 1843, Yol. XXXIV. 
Syn: Diastylis Icevis, Norman. 
Specific Characters. — Female. Body moderately robust, with the anterior 
division ovoid in form and hut slightly arcuate above. Carapace comparatively 
larger than in I). lucifera and more evenly vaulted above, surface perfectly 
smooth, hut clothed with scattered hairs; pseudorostral projection rather pro¬ 
duced, acuminate, horizontally extended, subrostral corners very slight. Exposed 
part of trunk, like the carapace, smooth, with scattered hairs, last segment with 
the anterior edge minutely serrate and setiferous, lateral parts slightly produced 
behind. Tail about the length of the anterior division, exclusive of the pseudo¬ 
rostral projection, and perfectly smooth. Eye well developed and somewhat 
convex. Superior antennaj very slender, with the peduncle extending far beyond 
the tip of the pseudorostral projection, its 1st joint much shorter than the other 
2 combined and unarmed, last joint very narrow, linear. First pair of legs much 
longer than the carapace, basal joint densely fringed with plumose setse, pen¬ 
ultimate joint considerably longer than the antepenultimate one, last joint some¬ 
what exceeding half the length of the penultimate one; 2nd pair rather densely 
setiferous, antepenultimate joint about the length of the last 2 joints combined; 
3rd and 4th pairs, like the 2 preceding pairs, without any denticles on the basal 
joint. Uropoda with the outer ramus about half the length of the stem, inner 
ramus somewhat shorter, and having the 1st joint as long as the other 2 com¬ 
bined. spinules of the inner edge about 12 in number (7 on the 1st, 3 on the 
2 nd, and 2 on the last joint), apical spine strong, forming the immediate con¬ 
tinuation of the joint. Telson rather produced, reaching as far as the stem of 
the uropoda, proximal thickened part occupying about Vs °f the length of the 
telson, distal part very narrow, with about 12 spinules on each side, apical 
spinules scarcely different from the lateral. Colour greyish white. Length 
amounting to 10 mm. 
Adult male resembling in external appearance that of D. cornuta, the 
carapace having on each side a distinct longitudinal carina crossed in front by 
an obliquely transverse plica; but this carina is quite smooth, not, as in the 
male of D. cornuta. serrate. Last pedigerous segment with the lateral parts 
considerably produced behind. Caudal segments spinulous. Eye larger than in 
the female, though, in the lateral view of the animal, partly concealed by a 
