104 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
4, Aga acuminata, n. sp. 
Plate II. Fig. 3-30. 
Only one specimen, a female without marsupium, 
Head. The frontal margin scarcely as concave on each side as in Æ. maxima, 
the median elongation not reaching the middle of the interior margin of the 
first joint of the antennule. The frontal plate conspicuously broader than 
long, seen from the side shaped as in the preceding species, seen from in front 
somewhat concave with projecting lateral margins. The eyes as in the preced- 
ing species. 
Antennule (Fig. 3). Reaching considerably beyond the peduncle of the 
antenne, to the middle of the first thoracic segment. The peduncle slightly 
shorter than the flagellum; the basal joint, seen from in front, quite as broad. 
as long ; the dorsal surface somewhat convex ; the antero-interior angle a little 
produced, acute-angled. The flagellum 18-jointed. 
Antenne. When reflexed, reaching to the posterior margin of the second 
thoracic segment, The relation of the peduncle to the flagellum is about that. 
of 2 to 3; the flagellum 19-20-jointed. 
Thorax (Fig. 3 a). The posterior margin of the epimera of the second to the 
fifth segment and the corresponding margin of the first segment sinuate, being 
directed a little forward just inside the somewhat produced postero-lateral angle, 
which is scarcely rectangular, but a little acute-angled. The epimera of the 
sixth segment forming a transition between those of the fifth and of the seventh 
segment, the last named pair posteriorly and laterally considerably produced 
and acute. 
Thoracic Legs. They are robust, though scarcely as clumsy as in 4%. maxima, 
but very similar in shape and armature. In the three anterior pairs the claw 
is somewhat longer ; the thick fourth joint in the first pair with one spine, in 
the second with five, in the third with six to eight spines. The spines on the 
four posterior pairs scarcely as numerous as in the preceding species, but some- 
what longer. 
Abdomen. The first segment almost totally covered, very conspicuously 
broader than the fourth. The last segment scarcely 14 times broader than long 
(in Fig. 3 b it seems to be proportionally broader, owing to the circumstance 
that the figure presents the projection of the posterior segments) ; posteriorly 
it is considerably produced, acute, with about three spines on each side of the 
tip ; the dorsal surface is rather convex, median keel and sublateral depressions 
scarcely visible. 
Uropods (Fig. 3b). Much as in Æ. maxima, so that only the more essential 
differences will be pointed out. The outer ramus reaching a little beyond the 
inner one; the inner ramus is more deeply incised on the exterior side, and the 
posterior margin is somewhat longer : thus we obtain a distal part forming an 
obtuse angle with the larger proximal part. 
