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U.S. NATIONAL MUSEUM BULLETIN 291 



Figure 27. — Vertical section, 65°W, 56°-63°S; temperature °C, oxygen concentration ml/L. 

 Capture points of Bathyleuthis abyssicola. 



Isopycnics across the Drake Passage in general follow the isohaline 

 contours (fig. 28). The denser water occurs at shallower depths on 

 the southern side of the Passage. A sigma-t of 27.75 occurs at 350 m 

 at about 63°S; at 56°30'S the same value is encountered at nearly 

 2500 m. 



Isopleths of oxygen concentration also lie deeper along the South 

 American continental shelf than along the southern edge of the 

 Drake Passage (fig. 27). At 61°10'S the oxygen minimum occurs at 

 a depth of 500 m with values of 4.21 ml/L to 4.23 ml/L. At 58° S the 

 minimum oxygen layer lies between 1000 and 1500 m with values of 

 4.03 ml/L to 4.12 ml/L. Below the minimum layer the oxygen con- 

 centration increases slightly with depth to values just under 5.0 

 ml/L. 



The fourteen captures that are plotted on the sections represent 

 successful tows between 60° W and 70° W during EJtanin Cruises 4 

 and 5. During Cruise 4, fourteen tows were made at depths greater 

 than 500 m and ten of these were successful in catching B. ahyssi- 

 cola; the four unsuccessful tows were in less than 1000 m (two from 



