40 
Lradyidius armatus T. Scott, 1906(a), p. 298. 
Lradyidius armatus van Breemen, 1908, p. 31, fig. 31. 
Female — length 1,7 mm. 
The cephalothorax seen from above appears oval fusiform in outline, with both extremities 
about equally narrowed. Viewed laterally it is seen to be moderately arched, with the forehead 
obtusely truncated, and produced into a small bifurcate rostrum with divergent points. The last 
thoracic segment is produced posteriorly into moderately strong spines, which scarcely reach 
to the end of the genital segment. The combined length of the abdomen and furca is equal 
to slightly less than one-third of the total length of the cephalothorax, from the front margin 
to the base of the genital segment. The genital segment is nearly as long as the combined 
length of the next three segments. The second segment is longer than the third. The third and 
fourth segments are of nearly equal length. The furcal joints are about as long as the anal 
segment, and are slightly longer than broad. The posterior margin of the genital segment is 
furnished with a fringe of fine spines. 
The various appendages are similar to the figures given by Sars in the ‘Crustacea 
of Norway’. 
The ‘Siboga’ specimens differ from the Norwegian form in size, and in the length of 
the spines of the last thoracic segment. Sars states that the spines reach beyond the genital 
segment. I have compared the ‘Siboga’ specimens with examples found in plankton collected 
in the Firth of Clyde, and with the exception of the smaller size, there appears to be no material 
difference between them. This can be seen on comparing the figures now given, with those in 
the ‘Sixteenth Annual Report of the Fishery Board for Scotland’ (1898). Dr. R. N. WoLFenDEN 
records a form obtained from plankton collected around the Maldives, under the name Lradyzdius 
armatus, which is probably identical with the species now figured. WoOLFENDEN’s specimens were 
even smaller than those obtained from the ‘Siboga’ plankton, but unfortunately no figures are 
given by that author, to enable a comparison to be made. 
This species was only represented by three specimens in the plankton collected during 
the traverse of the ‘Siboga’. The specimens were obtained at the following stations. 
Stat. 141, HENSEN vertical net, 1500 metres to surface, 2 specimens. 
Stat. 276, HENSEN vertical net, 750 metres to surface, I specimen. 
Genus AXtideopsis Sars, 1903. 
The genus “#tideopsi7s approaches -4tzdeus in general appearance, but is easily distinguished, 
by the fourth and fifth thoracic segments being completely separated. 
Only one species is known. Specimens not differing materially from the description and 
figures given by Professor G. O. Sars were found in the ‘Siboga’ plankton. I have, therefore, 
placed them under 4t:deopszs rostrata for the present. 
1. £tideopsts rostrata Sars. Plate V, figs. 13—24. 
Etideopsis rostrata Sars, 1903, p. 160, pls. IV & V (suppl.). 
Aitideopsis rostrata van Breemen, 1908, p. 33, fig. 35. 
40 
