152 BULLETIN 100, UNITED STATES NATIONAL MUSEUM 
most widely distributed species in the genus. It is especially abun- 
dant in surface tows and is included in all the plankton lists. 
ACARTIA DISCAUDATA (Giesbrecht) 
Dias discaudatus Girsprecut, Vierter Ber. Comm. Unters. deutsch. Meere, Jahrg. 
7, p. 148, pl. 3, figs. 4, 22, 23; pl. 5, fig. 18; pl. 6, fig. 17; pl. 8, figs. 32, 33, 
pl. 9, fig. 30, 1883. 
Stations 5175, 5176. Not included in any of the plankton lists and 
rarely reported by other observers. 
ACARTIA HAMATA [Sars MS.] Wilson, new species 
PLATE 2, FIGURES 1-5 
Found in the Butaritari Lagoon on Makin, the northernmost of 
the Gilbert Islands and in surface tows 5 miles south of the Suva 
Lightship in the Fiji Islands. 
Female.—Head separated from the first segment and constituting 
more than half of the metasome, widest across its posterior margin 
and a little narrowed anteriorly with a convex frontal margin. First 
segment a little wider than the head and three times as long as the 
second segment. Second, third, and the fused fourth and fifth seg- 
ments narrowed a little, and increasing in length, the last with stout 
spines at its posterior corners and a pair of smaller dorsal spines in 
front of the posterior margin, each halfway between the corner and 
the midline. Genital segment barrel-shaped, longer than wide, with 
a pair of dorsolateral spines at its posterior corners. Abdomen 
2-segmented, the anal segment a trifle the longer, the basal segment 
with a semicircular dorsal process projecting backward over the dorsal 
surface of the anal segment and reaching its center. Caudal rami 
about as wide as long, each with five setae, the second from the inside 
considerably longer than the others, which are approximately equal. 
The first antennae reach the caudal rami and are slender, with the 
basal segments imperfectly separated, but displaying the most dis- 
tinctive character of the species in the form of large spines. The 
basal segment has three spines, two on the anterior and one on the 
distal margin, the latter visible only in ventral view. The second 
seoment has a single strongly hooked spine on the ventral margin 
turned inward toward the head. Some of these spines are visible 
from any point of view and thus furnish the most convenient means 
of identification. The second antennae, mouth parts, and first four 
pairs of legs are of the usual pattern in this genus. The fifth legs 
are peculiar in having the terminal spike longer than the seta, curved 
almost into a half circle and perfectly smooth. The seta is rather 
loosely plumed, especially toward the tip, which tapers to a fine point. 
Total length 1.82 mm. Greatest width 0.32 mm. 
Type.—vU. 8S. N. M. No. 70729, Fiji Islands, south of Suva Light. 
