32 
two free joints attached to the basal portion. In the male, the left foot is greatly elongated, 
and is composed of five joints. The right foot is very short and consists of one or three joints. 
Two species belonging to this genus were represented in the ‘Siboga’ plankton. 
1. Clausocalanus arcutcornis (Dana). 
Calanus arcuicornis Dana, 1849, p. 12. 
Clausocalanus arcuicormis Giesbrecht, 1893, p. 186, pls. 1, 2, 10, 36. 
Clausocalanus 
Clausocalanus 
Clausocalanus 
Clausocalanus 
Clausocalanus 
Clausocalanus 
Clausocalanus 
Clausocalanus 
Clausocalanus 
Clausocalanus 
Clausocalanus 
Clausocalanus 
Clausocalanus 
Clausocalanus 
Qarcuicornis 
QV CULCOY NLS 
arcuicor nis 
ar cuicornts 
ar Culcornis 
arcuicornis 
ar cuicor nts 
arcutcornts 
arcutcornts 
ar culcornis 
ar cuicornts 
Qry CuLCOY NLS 
ar cutcornis 
ar cuicornts 
AS SOU, WOR, 9b 74 jolle Ge 
Giesbrecht & Schmeil, 1898, p. 27. 
I. C. Thompson, 1900, p. 277. 
Wheeler, 1900, p- 171, fig. 9. 
Glevie soo rp as: 
Thompson & Scott, 1903, p. 243. 
Harran, LOO3s5 Dumler. 
Cleves 19032) psas 59: 
Cleve, 1904, p. 188. 
ldgredhy, UCOE, (Os WA, ies 113 
Sars) 1905 (2); page 
Wolfenden, 1905 (a), p. 999. 
IPSBKASOIN, UGCOO, Ds Os 
Farran, 1908, p. 28. 
Clausocalanus arcuicornis van Breemen, 1908, p. 23, fig. 20. 
This species was moderately common, and appeared to be generally distributed in the 
area investigated, as shewn by the following records. 
Stat. 16. — Stat. 19. — Stat. 35. — Stat. 36. — Stat. 47°. — Stat. 71. — Stat. 75. — 
SUENS Oo = SU Cle) (Gey) —= Stic, Clo) (ilolei|s —— Silt, Oi, —— Sieh 112, —= Sia wis, — 
Stat. 121. — Stat. 128. — Stat. 141. — Stat. 142. — Stat. 143. — Stat. 148. — Stat. 168. — 
Stat. 174. — Stat. 185. — Stat. 203 (1500 metres to surface). — Stat. 205. — Stat. 213. — 
Stat. 215*. — Stat. 217 (horizontal cylinder). — Stat. 220 (vertical net). — Stat. 223. — 
Stat. 224. — Stat. 225. — Stat. 230. — Stat. 243. — Stat. 276. — Stat. 282. — Stat. 315. 
The females of Clawsocalanus arcutcornts, are not unlike those of the next species. They 
are rather larger than CJlauwsocalanus furcatus, and can be separated by the difference in the 
engths of the segments of the abdomen and furcal joints. In this species the genital segment 
is longer than each of the next two segments. The furcal joints are about as long as broad. 
This species has a wide distribution in the warm seas. It has also been recorded from 
the deep water of the Atlantic, off the West Coast of Ireland by G. P. Farran. 
2. Clausocalanus furcatus (Brady). 
Drepanopus furcatus Brady, 1883, p. 77, pls. IV & XXIV. 
Clausocalanus furcatus Giesbrecht, 1893, p. 186, pl. 36. 
Clausocalanus furcatus VY. Scott, 1893, p. 72. 
Clausocalanus furcatus Giesbrecht, 1896, p. 318. 
Clausocalanus furcatus Giesbrecht & Schmeil, 1898, p. 27. 
Clausocalanus furcatus Cleve, 1901, p. 5. 
Clausocalanus furcatus A. Scott, 1902, p. 403. 
Clausocalanus furcatus Thompson & Scott, 1903, p. 244. 
32 
