234 

 Three specimens belonging to the above species were obtained from the plankton collected 

 at the following two stations. 



Stat. 128 (HENSEN vertical net, 700 metres to surface), 2 specimens. — Stat. 148 (HENSEN 

 vertical net, 1000 metres to surface), 1 specimen. 



Aegisthus aculeatus is much smaller than the next species and the rostrum is not nearly 

 so prominent. The antennules are seven-jointed. The knob on the upper margin of the lïrst 

 joint is comparatively short. 



This species has only been recorded from the Atlantic and Pacific Oceans. 



2. Aegisthus miicronatus Giesbrecht. 



Aegisthus mucronatus Giesbrecht, 1891, p. 476. 



Aegisthus mucronatus Giesbrecht, 1893, p. 573, pis. 46 & 49. 



Aegisthus longirostris T. Scott, 1893, p. 104, pi. XI, figs. 31—34. 



Aegisthus mucronatus I C. Thompson, 1903, p. 33. 



Aegisthus mucronatus Cleve, 1904, p. 185. 



Aegisthus mucronatus Farran, 1905, p. 46. 



Aegisthus mucronatus Pearson, 1906, p. 36. 



Aegisthus mucronatus Farran, 1908, p. 91. 



Aegisthus mucronatus van Breemen, 1908, p. 183, fig. 197. 



Twenty specimens of this species were obtained from the plankton collected at the 

 following stations. 



Stat. 109. — Stat. 112. Stat. 118 (HENSEN vertical net, 900 metres to surface). — Stat. 



128 (HENSEN vertical net, 700 metres to surface). — Stat. 138. — Stat. 141 (HENSEN vertical 

 net, 1500 metres to surface). — Stat. 143 (HENSEN vertical net, 1000 metres to surface). — 

 Stat. 144. — Stat. 148 (HENSEN vertical net, 1000 metres to surface). — Stat. 203 (HENSEN 

 vertical net, 1500 metres to surface). — Stat. 215 1 . — Stat. 216. — Stat. 276 (HENSEN 

 vertical net, 750 metres to surface). 



This is a moderately large species with six-jointed antennules. The knob on the distal 

 end of the upper margin of the first joint is very prominent. The rostrum is long and pointed. 



Aegisthus vmcronatus appears to have a wider distribution than the previous species. 

 It has been recorded from the Atlantic Ocean, off the Coast of Africa and off the West Coast 

 of Ireland, and from the Pacific. The form described by my father from the Gulf of Guinea 

 as Aegisthus longirostris appears to be identical with Aegisthus mucronatus Giesbrecht. 



40. Family Monstrillidae. 

 Genus Monstrilla Dana, 1848. 



The body is elongate and rather cylindrical. The cephalic segment is of considerable 

 size and in some cases exceeds the combined length of the thorax and abdomen. There is 110 

 true rostrum. The abdomen is composecl of three segments in the female and four in the 



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