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Stat. 141 (HENSEN vertical net, 1500 metres to surface), 2 females. — Stat. 142, 2 males. - — 

 Stat. 148 (HENSEN vertical net, 1000 metres to surface), 8 females and five males. — Stat. 

 185 (HENSEN vertical net, 1536 metres to surface), 2 females and 1 male. — Stat. 203 

 (HENSEN vertical net, 1500 metres to surface), 2 females and 4 males. 



Genus Metacalanus Geve, 1901. 



This genus was established in 1901 by the late Professor P. T. Cleve for a small 

 Calanoid found in plankton collected near the Island of Langkuss, N.W. of Billiton in the Malay 

 Archipelago. It is nearly related to Arietellns in the structure of some of the appendages. It 

 also comes remarkably close to the genus Scottula established by Professor G. O. Sars in 1902 

 in 'Crustacea of Norway'. 



The only obvious difference between this genus and Scottula, is in the structure of the 

 female fifth pair of feet. The fifth pair in Scottula has two free joints and a basal part. Metacalanus 

 has only one free joint and a basal part. 



One species is known. It was well represented in the area investigated by the 'Siboga'. 



1. Metacalanus aurivillii Cleve. 



Metacalanus aurivillii Cleve, 1901, p. 43, pis. IV & V. 

 Metacalanus aurivillii Thompson & Scott, 1903, p. 243, pi. II. 



Males and females belonging to this species were found in the plankton collected at the 



following stations. 



Stat. 16. — Stat. 19. — Stat. 35. — Stat. 36. — Stat. 37. — Stat. 40. — Stat. 47''. - 

 Stat. 66. — Stat. 75. -*- Stat. 93. — Stat. 96 (day). — Stat. 96 (night). — Stat. 98. — 

 Stat. 99. — Stat. ioó. — Stat. 109. — Stat. 117*. — Stat. 11S (Hexsex vertical net, 900 

 metres to surface). — Stat. 125 (day). — Stat. 128 (Hexsex vertical net, 700 metres to 

 surface). Stat. 136. — Stat. 138. — Stat. 141 (HEXSEX vertical net, 1500 metres to 



surface). - - Stat. 142. — Stat. 143 (Hexsex vertical net, 1000 metres to surfacej. — Stat. 

 148 (Hexsex vertical net, 1000 metres to surface). — Stat. 184. — Stat. 203 (Hexsex 

 vertical net, 1500 metres to surface). — Stat. 205. — Stat. 213. — Stat. 217 (horizontal 

 cylinder). — Stat. 220 (Hexsex vertical net, 200 metres to surface). — Stat. 252. — Stat. 

 276 (HEXSEX vertical net, 750 metres to surface). — Stat. 282. — Stat. 304. — Stat. 315. 



Metacalanus aurivillii is a very small Calanoid and is easily overlooked. The female 

 is .65 mm. and the male .5 mm. in length. 



The right antennule of the male and female is distinctly shorter than the left. The fifth 

 pair of feet of the female is composed of one free joint attached to a basal part. The free 

 joint is broad and lamelliform. It is furnished with ene outer marginal seta, one apical seta, 

 and one long plumose inner marginal seta. The male fifth pair is quite symmetrical. It consists 

 of four free joints attached to a basal part. The apical joint of the right and left foot is in 

 the form of a long slender claw. The second and third free joints are each furnished with one 

 outer marginal seta. The endopodite is absent. 



This species was obtained by Cleve from plankton collected in the Malay Archipelago 

 in 1899. It was present in the plankton taken at twenty-seven stations round the Island of 

 <. eylon by Professor Hekdmax in 1903. 



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