242 



2. Oncaea media Giesbrecht. 



Oncaea media Giesbrecht, 1891, p. 477. 



Oncaea media Giesbrecht, 1893, p. 591, pis. 2 & 47. 



Oncaea media Cleve, 190 1, p. 8. 



Oncaea media A. Scott, 1902, p. 419. 



Oncaea media Thompson & Scott, 1903, p. 284. 



Oncaea media Cleve, 1903, p. 366. 



Oncaea media Cleve, 1904, p. 193. 



Oncaea media Wolfenden, 1905(0), p. 1029. 



Oncaea media Pearson, 1906, p. 35. 



Oncaea media van Breemen, 1908, p. 187, fig. 200. 



This Oncaea appeared to be very scarce in the area investigated by The 'Siboga'. It 

 was only found in the plankton collected at two stations. 



Stat. 148 (HENSEN vertical net, 1000 metres to surface), 3 specimens. — Stat. 203 (HENSEN 

 vertical net, 1500 metres to surface), 4 specimens. 



Oncaea media is closely related to Oncaea mediterranea and Oncaea venusta, but it can 

 readily be separated by the difference in the proportional length of the last three abdominal 

 segments and furcal joints. 



This species is widely distributed in the great oceans. 



3. Oncaea minuta Giesbrecht. 



Oncaea minuta Giesbrecht, 1893, p. 591, pi. 57. 



Oncaea minuta I. C. Thompson, 1900, p. 287. 



Oncaea minuta I. C. Thompson, 1903, p. 34. 



Oncaea minuta Thompson & Scott, 1903, p. 284. 



Oncaea minuta Esterly, 1905, p. 217, fig. 56. 



Oncaea minuta Norman & T. Scott, 1906, p. 197. 



Oncaea minuta Farran, 1908, p. 92. 



Oncaea minuta van Breemen, 1908, p. 188, fig. 201. 



Specimens of this form were found in the plankton from the following five stations. 



Stat. 75 (HENSEN vertical net, 11 metres to surface), 1 specimen. — Stat. 93. — Stat. 143 

 (HENSEN vertical net, 1000 metres to surface). — Stat. 217 (horizontal cylinder), 10 specimens. — 

 Stat. 304. 



Oncaea minuta is a comparatively small species. It can be recognised by the rather 

 inflated genital segment of the female and by the furcal joints being as long as the anal segment. 



This Oncaea has been recorded from the Atlantic, Indian and Pacific Oceans, and from 

 the Mediterranean. 



4. Oncaea tenuimana Giesbrecht. 



Oncaea tenuimana Giesbrecht, 1891, p. 477. 



Oncaea tenuimana Giesbrecht, 1893, p. 591, pis. 44 & 47. 



This species appeared to be very scarce in the area traversed by the 'Siboga'. It was 

 only present in the plankton collected at two stations. 



