Cephalosome generally well defined from the 1st pedigerous segment, and slightly 

 carinated dorsally in the male, frontal part obtuse, and more or less projecting 

 between the insertions of the anterior antennae. Lateral corners of last pedigerous 

 segment generally rounded off. Urosome symmetrical, with the genital segment 

 in female comparatively short and but slightly protuberant below. Caudal rami 

 well defined from the anal segment, and in male movably articulated to it, admit- 

 ting of being spread outwards, 2nd caudal seta (from within) longer than the 

 others. Anterior antennae generally longer than the body, and much more strongly 

 built in male than in female, with the first 2 articulations fused together into 

 a broad, somewhat flattened segment. Posterior antennae with the outer ramus 

 7-articulate. Posterior maxillipeds with the terminal part longer than either of 

 the basal joints, and 5-articulate, setae of the outer edge in male remarkably 

 developed and densely plumous. Legs comparatively slender, inner ramus well 

 developed, though considerably shorter than the outer, its 2nd joint (except in 

 last pair) having 2 natatory setae inside. Last pair of legs with the 1st basal 

 joint denticulate along the inner edge, but without the plumose seta present in 

 the other pairs; outer ramus in male without any natatory setae, and more strongly 

 developed on left side, though imperfectly prehensile; inner ramus in both legs 

 well developed, and resembling that in female. 



Remarks. In the restriction here adopted, this genus is chiefly charac- 

 terised by the imperfect prehensility of the last pair of legs in the male, this 

 pair still preserving its natatory character, \vhereas in the 2nd genus, Undina, 

 it is very much transformed, the left leg being quite enormously developed and 

 pronouncedly prehensile. Otherwise these 2 genera are closely related. The pre- 

 sent genus comprises several species, and seems to be represented in all parts 

 of the Oceans. To the Norwegian fauna belong 3 nearly-allied species, one of 

 which, however, has generally been confounded with the type species. 



l. Calanus ftnmarehieus, (Gunnerus). 

 (PI. i, n, in.) 



Monoculus finmarchicus, Gunnerus, Acta Hafnia, Vol. X, p. 175, figs. 20 23. 



Syn: Cetochilus septentrionalis, Goodsir. 

 ;; Calanus spitsbergensis, Kroyer $. 

 qvinqueannulatus, Kroyer cf- 



Specific Characters. Female. Anterior division of body, seen dorsally, 

 oblong oval in form, greatest width equalling y 3 of the length and occurring 

 about in the middle, frontal part but slightly produced; seen laterally, somewhat 

 dilated anteriorly, with the frontal margin broadly rounded and forming, together 



2 Crustacea. 



