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and ScumeiL doubtfully refer the two species described by Brapy to Undeuchaeta major, but 
I fail to see any reason for this. Neither Brapy’s descriptions or figures indicate the presence 
of a median crest on the forehead, or of a hooked spine on the ventral surface of the genital 
segment. These two characters are quite obvious in the ‘Siboga’ specimens of the female of 
Undeuchaeta major. It is extremely unlikely that Brapy would overlook the median crest, had 
it been present in the ‘Challenger’ specimens. The hook at the genital opening might be broken, 
as I have noticed it to be slightly damaged in some of the ‘Siboga’ specimens, but none had 
the median crest damaged in any way. The dorso-lateral spine, on the right of the genital 
segment when seen from above, is not always visible when the female is lying perfectly flat 
on its left side, and it cannot be seen at all when lying perfectly flat on the right side. A slight 
movement one way or the other, from the true lateral position is sufficient to bring the spine 
into view. This would account for its absence in the figure on Plate XXI, and its presence 
in the figure on Plate XIV. The view of the furcal joints in the latter figure shews quite well, 
that the specimen was not lying perfectly flat. The absence of the median crest is of more 
importance than the want of the spine. Female — length 3,5—4,5 mm. 
The fifth pair of feet of the males found in the ‘Siboga’ plankton is identical with the 
figures given by Lussock and by Brapy. The right and left sides have been reversed in the 
figure in the ‘Challenger Report’. 
The exopodite of the right and left foot is three-jointed. The endopodite of the right 
foot is apparently two-jointed. The endopodite of the left foot is only one-jointed. The second 
joint of the left exopodite is furnished with a strong spine on its inner distal angle. The middle 
of the inner margin of the third joint bears a tuft of setae. The apex of the joint is prolonged 
into a spine. 
The exopodite of the first pair of feet is distinctly three-jointed, but there is no outer- 
edge spine on the first joint. The endopodite of the second pair of feet is only one-jointed. 
The various mouth organs are much reduced as in the males of Awchaeta. 
The last thoracic segment is very slightly produced and the extremities are rounded. 
The rostrum is similar to the female but rather smaller. Male — length 3,2—3,6 mm. 
The species is widely distributed. I have examined males and females from collections 
of plankton taken in the deep water of the Farde Channel, by the Scottish International 
Fisheries Cruiser ‘Goldseeker’. There appears to be no difference between the North Atlantic 
type of Undeuchaeta plumosa, and those taken by the ‘Siboga’. 
3. Undeuchaeta intermedia nov. sp. Plate XXIII, figs. 1—8. 
Female — length 4,5 mm. 
The cephalothorax is oblong ovate and moderately robust. The head is distinctly separated 
from the first thoracic segment, and is furnished with a very faint median crest, which may 
only be a slight thickening of the integument, and a moderately long, one-pointed rostrum. 
The fourth and fifth thoracic segments are completely fused. The last thoracic segment is 
slightly asymmetrical, and both sides are prolonged into fine points. 
The abdomen is composed of four segments. The combined length of the abdomen and 
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