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Only two females were found. Length 3,5 mm. 



The 'Siboga' specimen that was dissected, and is illustrated in this report, agrees very 

 well with Giesbrecht's description. I do not attach much importance to the apparent absence 

 of the lamella on the basal joint of the second maxilliped, as it is evidently very small and 

 will, therefore, be easily folded up. 



Gaetanus armiger has a similar distribution to Gaetaniis miles, but does not appear, 

 so far, to have been taken in the deep water off the West Coast of Ireland. 



3. Gaetanus caudani Canu. Plate VIII, figs. 9 — 15. 



Gaetanus caudanï Canu, 1896, p. 422. 



Gaetanus caudani Giesbrecht & Schmeil, 1S98, p. 33. 



Gaetanus pileatus Farran, 1903, p. 16, pi. XVII, fig. 1 — 11. 



Gaetanus caudani Wolfenden, 1904, p. 114. pi. IX, figs. 20, 22. 



Gaetanus pileatus Farran, 1905, p. 33. 



Gaetanus caudani Sars, 1905 (a), p. 4. 



Gaetanus caudani Pearson, 1906, p. 13. 



Gaetanus unicornis Esterly, 1906, p. 57, pis. 9, 12, 13. 



Gaetanus pileatus Farran, 1908, p. 35. 



Gaetanus caudani van Breemen, 1908, p. 42, fig. 48. 



Gaetanus caudani was obtained from plankton collected with the Hp:nsen vertical net at 

 the following stations. 



Stat. 118 (900 metres to surface). — Stat. 128 (700 metres to surface). — Stat. 143 (iooo 

 metres to surface). — Stat. 230 (2000 metres to surface). — Stat. 276 (750 metres to surface). 



This Gaetanus, at first sight, looks like a large form of Gaetanus miles, but on careful 

 examination can readily be separated. 



The antennules are equal to one and a half times the length of the body, from the 

 apex of the cephalic spine to the end of the furca. They extend beyond the furca by the last 

 seven joints. The frontal spine is greatly prolonged, and viewed laterally, there is seen to be 

 a sudden change in the continuity of the outline, between the base and the apex. The spines 

 of the last thoracic segment reach to the middle of the genital segment. The combined length 

 of the abdomen and furca is distinctly less than one-fourth of the total length of the cephalo- 

 thorax, from the apex of the frontal spine to the base of the genital segment. The genital 

 segment is nearly as long as the combined lengths of the next three segments. The furcal 

 joints are about as long as broad, and are as long as the anal segment. The posterior margin 

 of the first three abdominal segments is fringed with fine spines. The rostrum is small and is 

 very faintly bifid at the apex. The lamella on the basal joint of the second maxillipedes is 

 narrowed at the apex and deeply excavated. The exopodite of the first pair of feet is two- 

 jointed, with a very faint line across the middle of the first joint. The first joint of the basio- 

 podite of the fourth pair of feet, is furnished with a number of fine bristles on its inner margin. 



Five specimens, all females, of this Gactantis were found. Length 6 mm. 

 Canu's description although given from an immature specimen, agrees fairly well with 

 the species now described. The 'Caudan' specimen was apparently an immature female, othervvise 



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