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are short. The joints are quite symmetrical, and are rather longer than the anal segment. Each 

 furcal joint is twice as long as broad. The second inner setae on the left furcal joint is much 

 longer and thicker than any of the others. 



The antennules are twenty-five-jointed and reach to the middle of the third abdominal 

 segment. The last joint is equal to two-thirds of the length of the second last joint. 



The antennules, mandibles and maxillae are nearly similar to those of Heter orhabdus. 



The apical portion of the first maxillipedes is furnished with two very stout and moderately 

 long spines. The inner surface of the spines is coarsely serrate (Plate XXXIX, fig. 18). 



The second maxillipedes are similar to those of Heterorliabdits. 



The exopodite and endopodite of the first, second, third and fourth pairs of swimming 

 feet are three-jointed. 



The exopodite and endopodite of the fifth pair of feet are also three-jointed. The joints 

 are short. The inner distal angle of the second joint of the exopodite is furnished with a 

 short, stout spine. The spine is rather suddenly contracted in the distal portion. The inner 

 margin of the first and second joints of the endopodite bears one moderately strong spine. 

 The proximal portion of each spine is finely plumose. The distal portion is rather coarsely 

 dentate (Plate XXXIX, fig. 21). 



Male unknown. 



This species is readily recognised by the truncate form of the last thoracic segment 

 when viewed from above, by the proportional length of the segments of the abdomen, by 

 the short symmetrical furcal joints, and by the armature of the two strong spines on the inner 

 margin of the endopodite of the fifth pair of feet. 



Occurrence. — One specimen was obtained from the plankton collected with the 

 Hexsen vertical net at Station 230, 2000 metres to the surface. 



Genus Disseta Giesbrecht, 1889. 



The members of this genus appear to be intermediate between Lucicutia and Hetcror- 

 habdus. The various appendages shew a close relationship to those of Lucicutia. The biting 

 edge of the mandible is almost identical in both types but it is quite distinct from Heterorhabdus. 

 The furcal joints are asymmetrical and resemble those of Heterorhabdus. The left joint is 

 longer and distinctly stouter than the right one. The male fifth pair of feet is quite distinct 

 from that of the male of Lucicutia or Heterorhabdus. 



Two species were represented in the plankton collected by the 'Siboga'. 



1. Disseta palumboi Giesbrecht. Plate XLI, figs. 11 — 21. 



Disseta palumboi Giesbrecht, 1889, p. 812. 

 Disseta palumboi Giesbrecht, 1893, p. 369, pis. 29 & 38. 

 Disseta palumboi Giesbrecht & Schmeil, 1898, p. 112. 

 Heterorhabdus grandis Wolfenden, 1904, p. 120, pi. IX, fig. 36. 

 Disseta palumboi Sars, 1905^), p. 3. 



Heterorhabdus grandis Wolfenden, 1905, p. 8, pi. IV, figs. 7 & 8 (male). 

 Heterorliabdits grandis Pearson, 1906, p. 26. 



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