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half of the total length of the ceplialothorax, from the frontal margin to the base of the genital 

 segment. The genital segment is as long as the combined length of the second and third seg- 

 ments. It is rather cylindrical in outline, and appears slightly asymmetrical when viewed from 

 above. Seen from the side, the dorsal surface is acutely pointed (Plate XLV, figs. 3 & 4). The 

 furcal joints are one and a half times longer than broad. They are about a third less than 

 the length of the anal segment. 



The apex of the last joint of the exopodite of the fifth pair of feet is divided into six 

 teeth. The third outer tooth is rather larger than the others (Plate XLV, fig. 6). Length of 

 female, 3,2 mm. 



The outer margin of the apical joint of the exopodite of the left foot of the male fifth 

 pair is boldly rounded. The distal end of the joint is produced into a short stout tooth-like 

 projection. The strong distal outer edge hook is about half the length of the joint (Plate XLV, fig. 9). 



Length of male, 3 mm. 



The figure of the animal shewn on plate VI in the report 'On Entomostraca from the 

 Gulf of Guinea' by my father, is identical with the female of the present species. The fifth 

 pair of feet shewn on the same plate does not belong to that individual. This is due to the 

 fact that drawings of two forms were prepared for publication, but through an error, the fifth 

 pair of feet belonging to the form represented by the figure of the copepod was omitted. 

 The fifth pair of the second form was inserted instead. The number of plates allowed by the 

 Linnean Society for the illustration of doubtful forms proved insufficiënt, and many figures had 

 to be suppressed although completed. I have compared the drawings that were intended for 

 publication with those identified in this report as Phyllopus bidcntalus, and find that the fifth 

 pairs of feet are identical. 



The single specimen described by Brady was obtained from plankton collected by the 

 'Challenger' in the South Atlantic, between Rio de la Plata, and the Island of Tristan da 

 Cunha. Sars records this species from the plankton collected by the Prince of Monaco, but as 

 no illustrations have yet been given one must regard the identity as doubtful. 



2. Phyllopus helgae Farran. Plate XLVI, fig. 7 — 14. 



Phyllopus bidentatus I. C. Thompson, 1903, p. 29, pi. III, figs. 6 — 9. 

 Phyllopus bidentatus Wolfenden, 1904, p. 124, pi. IX, fig. 16. 

 Phyllopus bidentatus Farran, 1905 (pars), p. 45, pi. XI, figs. 18, 19 & 21. 

 Phyllopus bidentatus van Breemen, [908 (pars), p. 143, fig. i6(</ — e). 

 Phyllopus helgae Farran, 1908, p. 83, pi. IX, figs. 5 & 6. 



One female and one male belonging to this species was found in the plankton collected 

 with the Hensen vertical net at Station 128, 700 metres to the surface. 



The female of this form is reaclilv recognised by the almost symmetrical and only 

 slightly produced distal ends of the last thoracic segment. The genital segment is asymmetrical. 

 It has a large protuberance on the right side. The fifth pair of feet is slightly asymmetrical. 

 The serration at the distal end of the apical joint of the fifth pair of the 'Siboga' female is 

 rather different from that shewn by Farran (Plate XLVI, fig. 11). 



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