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of its antennules. The antennules extend beyond the body by five joints. It can be also 
recognised by the armature of the distal part of the last joint of the exopodites of the fourth 
pair of feet. The armature consists of a number of very fine teeth. 
This species has been recorded from the Atlantic, Indian, and Pacific Oceans, and also 
from the Red Sea. 
2. Acrocalanus gractlis Giesbrecht. 
Acrocalanus gracilis Giesbrecht, 1888, p. 332. 
Acrocalanus gracilis Giesbrecht, 1893, p. 171, pls. 6 & Io. 
Acrocalanus gracilis Giesbrecht, 1897, p. 318. 
Acrocalanus gracilis Giesbrecht & Schmeil, 1898, p. 25. 
Acrocalanus gracilis Cleve, 1901, p. 4. 
Acrocalanus gracilis Thompson & Scott, 1903, p. 243. 
Acrocalanus gracilis Cleve, 1903, p. 356. 
Acrocalanus gracilis Cleve, 1904, p. 184. 
Acrocalanus gracilis Wolfenden, 1905 (a), p. 1003. 
This Acrocalanus although not so common as the preceeding species, was more plentiful 
than either of the next two. It occurred at the following stations. 
Stat. 16. — Stat. 36. — Stat. 4o. — Stat. 75. — Stat. 93. — Stat. 98. — Stat. 99. — 
Stat. 101. — Stat. 109. — Stat. 117%. — Stat. 118. — Stat. 138. — Stat. 141. — Stat. 
142. — Stat. 143. — Stat. 148. — Stat. 203 (1500 metres to surface). — Stat. 213. — 
Stat. 215%. — Stat. 217 (horizontal cylinder). — Stat. 224. — Stat. 225. — Stat. 229. — 
Stat. 243. — Stat. 245. — Stat. 315. 
This species is easily distinguished from the other three, by its larger size, and by the 
smoothly rounded dorsal surface of the cephalothorax, when viewed from the side. 
Acrocalanus gracilis has a distribution similar to the preceeding species. 
3. Acrocalanus gibber Giesbrecht. 
Acrocalanus gibber Giesbrecht, 1888, p. 332. 
Acrocalanus gibber Giesbrecht, 1893, p. 171, pls. 6 & Io. 
Acrocalanus gibber Giesbrecht & Schmeil, 1898, p. 65. 
Acrocalanus gibber J. C. Thompson, 1900, p. 276. 
_ Acrocalanus gibber Cleve, 1901, p. 4. 
Acrocalanus gibber A. Scott, 1902, p. 402. 
Acrocalanus gibber Thompson & Scott, 1903, p. 243. 
Acrocalanus gibber Cleve, 1903, p. 356. 
Acrocalanus gibber Cleve, 1904, p. 184. 
Acrocalanus gibber Wolfenden, 1905 (a), p. 1003. 
Acrocalanus gibber although not common, apparently had a moderately wide distribution 
in the area traversed by the ‘Siboga’, as shewn by the following records. 
Stat. 16. — Stat. iO, —= Sia 26 — Sta go, == Sie, 976 —] Sela 77) —= Sieie Of, — 
Sine, OS — Sick, 12 — Stat, wi, —= Seis me == Siete Wiis = Sikhs adi, —— Siete, 
143. — Stat. 184. — Stat. 215°. — Stat. 247 (horizontal cylinder). — Stat. 315. 
This species when present, can be easily identified by its very compact body, and although 
2Y) 
