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spines on the apical lobes are more slender and flexible. The internal and external margins of 
the claw-like spines are fringed with fine hairs. The apex is furnished with three long plain 
filaments and five short organs with inflated heads. (Plate XXXV, fig. 15). 
The second pair of maxillipedes is similar to that of NXanxthocalanus. 
The exopodite of the first pair of feet is three-jointed, and the endopodite is one-jointed. 
The exopodite of the second pair of feet is three-jointed, and the endopodite is two-jointed. 
The second joint of the endopodite is furnished with three transverse rows of strong spines. 
The exopodites and endopodites of the third and fourth pairs of feet are each three- 
jointed. The second and third joints of the endopodite of the third pair of feet are each furnished 
with two transverse rows of strong spines. The second and third joints of the endopodite of 
the fourth pair of feet are furnished with fine spines as shewn (Plate XX XV, fig. 17). 
The fifth pair of feet is symmetrical, but obviously rudimentary. The basiopodite is two- 
jointed. Fhe exopodite is distinctly two-jointed. The first joint is furnished with one outer-edge 
spine. The second joint is broadly triangular in outline. It bears one apical and three subapical 
Spines a (ivlate: XOOGV tics ano): 
Occurrence. — One specimen was obtained from the plankton collected with the 
HENSEN vertical net at. Station 185, 1536 metres to the surface. 
The specimen is apparently an immature male, and the fifth pair of feet is very similar | 
to the figure given by Farran (1905 pl. XI, fig. 10). Farran regards his species to be closely : 
related to Odthrix bidentata (= Neoscolecithrix koehlert Canu). The present species, however, 
does not appear to belong to that genus, as the short sausage-shaped organs, on the apex of 
the first maxilliped, which are so characteristic of that genus are absent. FARRAN’s specimens 
measured 3,35 mm. 
I= 
J 
Genus Onchocalanus G.. O. Sars, 1905 (a). 
This genus is closely related to Xanthocalanus, but the females are easily recognised 
by the strongly bifurcate rostrum, and by the apical lobe of the first pair of maxillipedes being 
furnished with a very stout curved claw. The posterior surface of the joints of the swimming © 
feet is armed with numerous fine spines. The fifth pair of feet is small. 
Two of the known species were represented in the plankton collected by the ‘Siboga’. 
1. Onchocalanus cristatus (Wolfenden). Plate XXXIV, figs. 1—8. 
AXanthocalanus cristatus \Wolfenden, 1904, p. 119, pl. IX, figs. 18 & Ig. 
Onchocalanus trigoniceps Sars, 1905(a@), p. 20. 
AXanthocalanus cristatus Pearson, 1906, p. 20. 
Onchocalanus cristatus Sars, 1907 (a), p. 3. 
Onchocalanus cristatus Farran, 1908, p. 49. 
Xanthocalanus cristatus van Breemen, 1908, p. 62, fig. 70. 
One female belonging to this species was found in the plankton collected with the 
HENSEN vertical net at each of the following two stations. 
Stat. 148 (1000 metres to surface). — Stat. 185 (1536 metres to surface). 
82 
