24 



PROCEEDINGS OF THE ISTATIOISrAL MUSEUM 

 31. NEMATOBRACHION FLEXIPES (Ortmann) 



Occurrence 



Remarks. — All the specimens have a spine on the lateral margin 

 of the carapace. This confirms my previous observations on this 

 point and Hansen's definition of the genus will require modification 

 in this respect. The species appears to be widely if sparingly dis- 

 tributed throughout the tropical oceanic area. It is most abundant 

 in the upper 200 meters, 153 out of 178 specimens in this collection or 

 86 per cent being captured between 200 meters and the surface. 

 Only one specimen was actually taken at the surface and only five 

 at 50 meters. The species therefore appears to be an epiplanktonic 

 form with a maximum distribution between 50 and 200 meters. 



32. NEMATOBRACHION SEXSPINOSUS (Hansen) 



Occurrence. — Station 10166, 1100-0 m., 1 female, 27 mm.; station 

 10192, 1000-0 m., 1 male, 23 mm. 



Remarks. — Both specimens have a well-developed spine on the 

 lateral margin of the carapace near the posterior end, in this respect 

 agreeing with N. flexipes. In addition to the characters enumer- 

 ated by Hansen as distinguishing these two species it may be men- 

 tioned that N. sexspinosus possesses a prominent supraocular spine 

 on the lateral margins of the rostral plate immediately over the eye. 



N. sexspinosus is among the rarest of Euphausians. Only three 

 specimens have been previously recorded, two from the tropical East 

 Pacific and one from the temperate North Atlantic (Hansen, 1911 

 and 1912). In all cases the specimens were captured in deep water. 



