164 U.S. NATIONAL MUSEUM BULLETIN 291 



other hand, appears to be restricted to the Equatorial Water Masses 

 of the Pacific and possibly the Indian Ocean; no equatorial water 

 mass occurs in the Atlantic, and despite heavy exploratory fishing 

 efforts in equatorial regions, no specimens of this species have been 

 captured. 



"VVlierever Bathyteuthh is found, it occurs within waters of relatively 

 higli productivity that have similar oceanographic characteristics. 

 Figure 61 presents the T-S-density relationships of BathyteutMs cap- 

 tures from Antarctic, Pacific, Atlantic, and Indian Oceans. In the 

 Antarctic the great majority of captures (small box) falls between 1° 

 to 2.5° C, 34.65%o to :M.75%o, and sigma-t=27.70 to 27.85. The few re- 

 maining Antarctic captures (large box) range from 0° to 3° C, 34.30%o 

 to 34.75%o, and sigma-t =27.20 to 27.90. In the Pacific Equatorial 

 Waters (P) the caiptures were made between 3° to 6° C, 34,55%o to 

 34.65%o, and sigma-t=27.25 to 27.55. In the Atlantic (N, S) most cap- 

 tures came from conditions between 2.5° to 4.5° C, 34.85%o to 34.97%o, 

 and sigma-t = 27.70 to 27.87. Other scattered captures from shallower 

 South Atlantic Central Water (S) range from 4° to 7.5° C, 34.50%o 

 to 34.75%o, and sigma-t = 27.00 to 27.50. The few captures in the Indian 

 Ocean (I) range from 2.5° to 7.5° C, above 34.70%o to 34.95%o, and 

 sigma-t= 27.30 to 27.80. B. ahysslcola occurs over a broad range of 

 oxygen concentrations from about 1.50 ml/L to greater than 5.25 ml/L, 

 while B. hacidifera occurs in lower concentrations from less than 0.50 

 ml/L to about 2.75 ml/L. In either case, specimens occur in or, most 

 often, below the oxygen minimum layer. 



Finally, Bathyteuthh is most closely associated with areas where 

 high productivity takes place in the surface layers (fig. 60). Captures 

 come from the layer of maximum or high phosphate concentrations. 

 The high productivity, of course, is responsible for the oxygen mini- 

 mum layer. 



In conclusion the species of Bafkyfenthis may be considered steno- 

 thermic (l°-5° (-7°) C), stenohaline (34.50%o-34.95%o), stenopycnic 

 (sigma-t= 27.00-27.20-27.90), and euryaerobic (1.5-5.25 ml/L). {B. 

 hacidifera is oligoaerobic (0.5-2.75 ml/L)). They are true bathy pe- 

 lagic cephalopods that seldom approach within 1000 m of the bottom 

 (usually more than 2000 m) or within 500 m of the surface. Specimens 

 that occur in less than 750 m are generally juveniles or larvae and are 

 in waters that have suitable temperature and salinity values (because 

 of high latitude locations or areas of upwelling). 



But, above all, the limiting factor that has the greatest effect upon 

 the distribution of Bathyteuthis is organic productivity. 



