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Disseta grandis Esterly, 1906, p. 72, pis. 9, il, 13 & 14. 



Disseta palumboi Farran, 1908, p. 67. 



Heterorhabdus grandis van Breemen, 1908, p. 126, fig. 145. 



Four females and four males apparently identical with Giesbrecht's species were found 

 in the plankton collected with the Hensen vertical net at the following stations. 



Stat. 141 (1500 metres to surface), 3 specimens. — Stat. 230 (2000 metres to surface), 4 spe- 

 cimens. — Stat. 243 (1000 metres to surface), 2 specimens. 



Length — female 8 mm., male 7,75 mm. 



With the exception of the difference in size I see nothing to separate the 'Siboga' 

 females from the description and figures given by Giesbrecht. 



The male was unknown when the original description was given but it has been found 

 within recent years by Wolfenden in the plankton collected by the 'Gauss' and by Esterly 

 in the Pacific. Wolfenden described the female and male as Heterorhabdus grandis. Esterly 

 recognised the identity of his specimens with the genus Disseta, and named the form Disseta grandis. 



With the exception of an apparent difference in the proportional length of the abdominal 

 segments of the female, and an asymmetrical genital segment, the specimens from the Pacific 

 are identical with those obtained by the 'Siboga'. The abdominal segments of the Copepoda 

 are apt to become telescoped at death, and an unnatural shortening may, therefore, easily take 

 place, which will give rise to incorrect proportional lengths. The asymmetry of the genital 

 segment of Esterly's specimens may be due to accident. The genital segment of the 'Siboga' 

 females is quite symmetrical as shevvn in the illustration. 



The last abdominal segments, and the furcal joints of the male, are similar to those 

 of the female. Esterly's figure of the male left fifth foot, shews the apical spine on the third 

 joint of the exopodite to be short and stout, but the more slender distal portion may easily 

 have been damaged. Wolfenden's figure of the fifth pair of the male of Heterorhabdus grandis 

 is identical with the one given in this report. 



Difference in size unless accompanied by some other decided feature is of little or no 

 specific value. 



Disseta palumboi appears to have a fairly wide distribution. 



2. Disseta seopularis (Brady). Plate XLII, figs. 1 — 9. 



Leuckartia seopularis Brady, 1883, p. 51, pi. XIV, figs. 1 — 5. 

 Leuckartia seopularis Giesbrecht & Schmeil, 1898, p. 125. 



A single male specimen, evidently identical with Brady's Leuckartia seopularis, was 

 found in the plankton collected with the Hensen vertical net at Station 250, 2000 metres to 

 the surface. 



The specimen was rather mutilated. The antennules, antennae, mandible palps and 

 second maxillipedes were incomplete. The more important characters, however, were intact. 

 The biting edge of the mandible (Plate XLII, fig. 4) clearly shews that this Calanoid is not, 

 as stated by Wolfenden in 'Plankton Studies' part I, page 23, a Heterorhabdus. The biting 



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