28 
arched when seen from the side. The rami of the rostrum are slender and sharply pointed, and 
the excavation is deeper than in the other two species (PI. IV, fig. 17). The last thoracic spines 
extend to the end of the genital segment only, and are not greatly chitinized. The proportional 
lengths of the abdominal segments are very different from 4tzdeus giesbrechtt. The combined 
length of the abdomen and furca is slightly more than one-third of the total length of the 
cephalothorax, from the forehead to the base of the genital segment. The genital segment is 
distinctly longer than the combined length of the next two segments. The second, third, and 
fourth segments are of nearly equal length. The furcal joints are longer than the anal segment, 
and are about twice as long as broad. 
Length of female 2 mm. 
Etideus armatus appears to be widely distributed, if all the records be regarded as 
correct. SARS in the appendix to the volume on the Calanoids ‘Crustacea of Norway’, states, 
that he examined two of the ‘Challenger’ specimens, and could find no difference between them 
and the Norwegian forms. It was present in the plankton from the Gulf of Guinea, but I was 
unable to find it in the Ceylon material. 
3. <Etideus bradyz nov. sp. Plate V, figs. 1—12. 
Aitideus armatus Brady, 1883 (pars), p. 76, pl. X, figs. 5—16. 
Aitideus armatus T. Scott, 1893 (pars), p. 70. 
Etideus armatus Giesbrecht & Schmeil, 1898 (pars), p. 31. 
Etideus armatus Thompson & Scott, 1903 (pars), p. 224. 
Female — length 1,8 mm. 
In general appearance this species resembles 4tzdeus giesbrechte but it can be distinguished 
both from that species, and from #tzdeuws armatus, by the following characters: — Viewed 
from the dorsal aspect, the forehead is marked by a deep constriction just behind the front 
margin. A slight expansion is caused by the wide base of the rostrum, and the front margin 
appears to have a bluntly rounded, knob-like projection. In lateral view, the forehead is boldly 
arched, and a distinct chitinized crest is present. The rostrum is very large and horny, with a 
moderately deep excavation. The rami are slightly converged at the apex. The last thoracic 
segment is distinctly chitinized, and is produced into strong spines. The spines project to near 
the middle of the second abdominal segment. The combined length of the abdomen and furca, 
is slightly greater than one-third of the total length of the cephalothorax, from the forehead 
to the base of the genital segment. The genital segment is equal to the combined length of 
the next two segments. The second and fourth segments are of equal length, but the third 
segment is distinctly shorter than these two. The furcal joints are about as long as the anal 
segment, and are fully twice as long as broad. 
The various appendages have a general resemblance to those of the previous species. 
Occurrence — twenty-five specimens of this species were obtained from the plankton 
collected at the following stations. 
Stat. 118, 2 specimens. — Stat. 128, 1 specimen. — Stat. 141, 4 specimens. — Stat. 143, 
2 specimens. — Stat. 185, 4 specimens. — Stat. 203 (1500 metres to surface), 6 specimens. — 
Stat. 220 (vertical net), 2 specimens. — Stat. 276, 4 specimens. 
38 
Pe 
