SI 
Stat. 118 (HENSEN vertical net 900 metres to surface). — Stat. 141 (HENSEN vertical net 
1500 metres to surface). — Stat. 203 (HENSEN vertical net 1500 metres to surface). 
The species is very distinct. It is easily identified by its elongate body and greatly 
produced last thoracic segment. 
The posterior margins of the last thoracic segment reach to near the distal end of the 
genital segment. The combined length of the abdomen and furca is equal to one-fourth of the 
total length of the cephalothorax, from the frontal margin to the posterior end of the last thoracic 
segment. The rami of the rostrum are two-jointed and the apical section is very slender. The 
antennules are twenty-four-jointed, and extend to the end of the second abdominal segment. 
The fifth pair of feet is composed of two free joints attached to a basal part. The second joint 
is furnished with one apical and two subapical spines (Plate XXXII, fig. 18). 
Length of female 2,68 mm. 
Xanthocalanus agilis is apparently very rare. It has only been recorded from the Gulf 
of Naples by GirsBREcHT. 
Genus Brachycalanus Farran, 1905. 
The members of this genus are separated from the other genera belonging to the family, 
chiefly by the very strong, slightly bifurcate, and highly chitinised rostrum. The mouth organs 
and swimming feet closely resemble. those of Xanthocalanus. 
The genus was represented in the ‘Siboga’ plankton by a single immature specimen. 
1. Lrachycalanus gigas nov. sp. Plate XXXV, figs. 10—18. 
Length — 7,2 mm. 
Viewed from above, the body appears moderately robust, and elongate ovate in outline. 
The head is distinctly separated from the first thoracic segment, and is furnished with a low 
median crest. The fourth and fifth thoracic segments are~separated. The last thoracic segment 
is produced to the end of the first abdominal segment, and terminates in distinct points that 
project outwards from the segment. Seen from the side, the forehead is arched, and the median 
crest is rounded at the apex. The last thoracic segment is irregularly triangular in outline, with 
a small point at the apex. The rostrum is robust, of moderate length, and is slightly bifurcate 
at the upturned apex. No filaments are present. 
The abdomen is composed of five segments. The combined length of the abdomen and 
furca is contained about three and a half times in the total length of the cephalothorax, from 
the frontal margin to the base of the genital segment. The abdominal segments are wide, and 
are comparatively short. The anal segment is very small. The furcal joints are rather longer 
than broad, and are about twice as long as the anal segment. 
The antennules are composed of twenty-four joints, and extend to the end of the third 
abdominal segment. The eighteenth joint is faintly divided. 
The antennae, mandibles and maxillae are similar to those of Xanthocalanus. 
The first pair of maxillipedes also resembles that of Xanthocalanus, but the claw-like 
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