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The four pairs of swimming feet are very similar to those of Aucalanus attenuatus. 
Male unknown. 
This species is easily distinguished from the other members of the genus by its strong, 
well defined cephalic spine, and by the absence of segmentation in the exopodite of the 
mandible palp. 
Specimens of this species were found in samples of plankton from the following stations. 
Stat. 141, I specimen. — Stat. 172, 3 specimens. — Stat. 184, 2 specimens. — Stat. 315, 
I2 specimens. 
Genus Rhincalanus Dana, 1852. 
The members of this genus are distinguished from Lwcalanus, by the peculiar beak-like 
projection of the forehead, by the spines on the thoracic segments, and by the presence of a 
fifth pair of feet in the female. Two species were represented in the plankton collected by 
the ‘Siboga’. 
1. Rhincalanus cornutus Dana. 
Rhincalanus cornutus Dana, 1852, p. 1083, pl. 76. 
Rhincalanus cornutus Brady, 1883, p. 41, pl. VII. 
Rhincalanus cornutus 1. C. Thompson, 1888, p. 148. 
Rhincalanus cornutus TV. Scott, 1893, p. 30. 
Rhincalanus cornutus Giesbrecht, 1893, p. 153, pls. 12 & 35. 
Rhincalanus cornutus Giesbrecht & Schmeil, 1898, p. 23. 
Rhincalanus cornutus 1. C. Thompson, 1900, p. 276. 
Rhincalanus cornutus Cleve, 1901, p. 8. 
Rhincalanus cornutus A. Scott, 1902, p. 402. 
Rhincalanus cornutus 1. C. Thompson, 1903, p. 16. 
Rhincalanus cornutus Thompson & Scott, 1903, p. 242. 
Rhincalanus cornutus Cleve, 1903, p. 368. 
Rhincalanus cornutus Cleve, 1904, p. 190. 
Rhincalanus cornutus Sars, 1905(a), p. 2. 
Rhincalanus cornutus Wolfenden, 1905 (a), p. 996. 
Rhincalanus cornutus Pearson, 1906, p. 8. 
Rhincalanus cornutus van Breemen, 1908, p. 18, fig. 15. 
This species although not very common except at Station 141 and Station 148, appeared 
to be generally distributed throughout the area traversed by the ‘Siboga’, as shewn by the 
following records. 
Stat. 35. — Stat. 36. — Stat. 37. — Stat. 40. — Stat. 50. — Stat. 66. — Stat. 81. — 
Stat. 98. — Stat. 99. — Stat. 106. — Stat. 112. — Stat. 117%. — Stat. 118. — Stat. 125 
(day). — Stat. 128. — Stat. 133. — Stat. 136. — Stat. 138. — Stat. 141, 160 specimens. — 
Stat. 143. — Stat. 144. — Stat. 146. — Stat. 148, 422 specimens. — Stat. 157. — Stat. 
165. — Stat. 168. — Stat. 169. — Stat. 172. — Stat. 174. — Stat. 177%. — Stat. 184. — 
Stat. 185. — Stat. 189%, — Stat. 203 .(1500 metres). — Stat. 204. — Stat. 213. — Stat. 
216. — Stat. 220 (vertical net). — Stat. 220 (surface). — Stat. 223. — Stat. 230. — Stat. 
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243. — Stat. 276. — Stat. 282. — Stat. 315. 
Rhincalanus cornutus appears to be widely distributed in the warmer seas. WOLFENDEN 
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