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of that genus, by the absence of spines or teeth on the inner margin of the first joint of the 
basiopodite of the fourth pair of feet. The rostrum is one-spined, and the exopodite of the first 
pair of feet is two-jointed. 
Three species, one of which appears to be new, were found in the plankton collected 
during the traverse of the ‘Siboga’. 
1. Undeuchaeta major Giesbrecht. 
Undeuchaeta major Giesbrecht, 1888, p. 335. 
Undeuchaeta major Giesbrecht, 1893, p. 227, pl. 37. 
Undeuchaeta major Giesbrecht & Schmeil, 1898, p. 34. 
Undeuchaeta major 1. C. Thompson, 1900, p. 278. 
Scolecithrix cristata 1. C. Thompson, 1903 (pars), p. 21, pl. III, male. 
Undeuchaeta major Wolfenden, 1904, p. III. 
Undeuchaeta major Cleve, 1904, p. 198. 
Undeuchaeta major Farran, 1905, p. 35. 
Undeuchaeta major Esterly, 1905 (pars), p. 148, fig. 16 (pars). 
Chirundina angulata Sars, 1905(a), p. 13. 
Undeuchaeta major Pearson, 1906, p. 15. 
. Undeuchaeta major Sars, 1907 (a), p. 3- 
Undeuchaeta major Farran, 1908, p. 37. 
Undeuchaeta major van Breemen, 1908 (pars), p. 43, fig. 49 (pars). 
Four specimens, all females, of this Umxdeuchaeta were found in the plankton collected 
at the following stations. 
Stat. 117%. — Stat. 141 (HENSEN vertical net 1500 metres to surface). — Stat. 148 (HENSEN 
vertical net 1000 metres to surface). — Stat. 230 (HENSEN vertical net 2000 metres to surface). 
The female of this species is distinguished from the others by the presence of a distinct 
and moderately high crest, by a blunt projection on the right side of the genital segment, and 
also by the hook on the right side of the genital opening. 
Undeuchaeta major was first described from the Pacific Ocean, but the distribution has 
since been found to extend to the North Atlantic. 
The ‘Siboga’ specimens measured 4,8—6,4 mm. 
I regard the male of the species recorded by the late I. C. TuHompson as Scolectthrix 
cristata from plankton collected during the cruise of the ‘Oceana’, to be the male of Unudeuchaeta 
major. It is not the male of Scaphocalanus magnus (TY. Scott). I recently had the opportunity 
of examining a male Copepod taken during one of the cruises of the Scottish International 
Fisheries Cruiser ‘Goldseeker’, in the deep water of the Farée Channel. This Copepod has a 
similar armature on the fifth pair of feet to that shewn by Tuompson (1903 pl. III, fig. 5), 
and appears to be identical with Undeuchacta major. The specimen has a median crest and a 
one-pointed rostrum. 
The form identified and illustrated by Esrerty (1905 p. 148, fig. 16), as the male of 
Undeuchacta major, is, 1 think, very doubtfully so. Esterty gives the length of the female as 
4,5—5,5 mm. and the male as 6—6,5 mm. It is very unusual to find the males of the Calanoids 
so much larger than the females. The figure of the left fifth foot resembles that of a species 
of Paracuchaeta. 
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