52 U.S. NATIONAL MUSEUM BULLETIN 291 



(1948) considered 10 of them to be B. dbyssicola; the remaining speci- 

 men (7 mm ML) he called Bathytheuthis sp. primarily on the basis of 

 different body proportions. Robson recognized that considerable varia- 

 tion exists in specimens referred to B. ahyssicola^ but he did not illus- 

 trate or adequately describe his specimens. Therefore, it is impossible 

 to know if these specimens should be referred to B. abyssicola or to 

 B. Ixicidifera. 



In conclusion, only one specimen mentioned in the literature prob- 

 ably can be referred to B. 'bacidifera: Chun's specimen of 18 mm ML 

 from Valdivia Sta. 221, 04°05'S 73°24'E, in the Indian Ocean. 



Occurrence in relation to physical parameters. — The specimens 

 of B. bacidifera all were captured in open nets that were calculated to 

 have fished at depths ranging from 683 meters to 1550 meters. The 

 depths of capture for the Dana specimens have been calculated by the 

 method suggested by Bruun (1943) ; since no wire angles were taken 

 during Dana tows, Bruun calculated that the fishing depth is one- 

 third the length of the wire for less than 1000 meters of wire out and 

 one-half the length of the wire for more than 1000 meters of wire out. 

 The Dana specimens were taken as follows : two at 750 meters, one each 

 at 1000 and 1050 meters, three at 1250 meters and one at 1550 meters. 

 Three Eltanin specimens were taken in an Isaacs-Kidd Midwater 

 Trawl (IKMT) that fished around 683 m, and a fourth came from 

 1373 m. It is extremely unfortunate that so few tows were taken dur- 

 ing the period that the Eltanin was working southward along the east- 

 em Pacific boundary. It is also unfortunate that Robson's eleven 

 Arcturus specimens from the Galapagos region and Hoyle's two Albat- 

 ross specimens from the Gulf of Panama are not specifically identifiable 

 from the descriptions. 



The temperature-salinity relationships of B. bacidifera are plotted 

 on figure 44. The zone of captures falls within the envelope of the 

 Eastern Pacific Equatorial Water Mass. The range of the depths of 

 capture corresponds to the band of the salinity minimum (34.55%o to 

 34.61%o) where the temperature ranges from just above 3° C in deeper 

 water to nearly 6° C in the shallower portion of the range. The density 

 values increase with depth from sigma-t= 27.20 to 27.60. In addition, 

 the oxygen concentration of the water layer between 200 to 2000 m is 

 extremely low, between 0.1 ml/L and 2.0 ml/L; it represents a very 

 broad oxygen minimum layer. The lowest values (0.1-0.5 ml/L) occur 

 at the shallowest depths (ca 200-700 m) so B. bacidifera, with depth- 

 of -capture values of 0.47 to 1.47 ml/L, lies just below the oxygen mini- 

 mum layer. 



The narrow band along the eastern boundary of the tropical Pacific 

 water mass is an area of high organic productivity (fig. 60). Z?. bacidi- 



