148 



U.S. NATIONAL MUSEUM BULLETEST 291 



Figure 48. — Vertical section, 85°W; phosphate, microgram atoms/L. Capture points of 

 Bathyteutkts abyssicola and B. bacidifera in the eastern Pacific. 



between Dominica and Martinique where a narrow channel drops to 

 less than 1500 m. The deepest portals into the Caribbean are the Wind- 

 ward Passage between Cuba and Hispaniola and the Anegada and 

 Jungfeni Passages between the Virgin and Windward Islands, and 

 the Virgin Islands and St. Croix Island. The sill depth of these pas- 

 sages does not exceed 1600 m. Similarly the sill across the Yucatan 

 Channel into the Mexican Basin is about 1600 m ; the portal into the 

 Straits of Florida has a sill depth of 800 m. The water that flows 

 through the Caribbean is a mixture of North and South Atlantic 

 Water Masses. The surface waters are composed of western North 

 Atlantic (Sargasso Sea) w^ater in a ratio of 3-i to 1 over South At- 

 lantic waters; slightly deeper, the ratio falls to 2 to 1 (Sverdrup et al., 

 1942). Antarctic Intermediate Water and Upper Deep Water flow in 

 over the sills; the deep water of the Caribbean is renewed from the 

 North Atlantic through the Windward and the Anegada and Jungfem 

 Passages. Below 500-1000 m the temperature and salinity conditions 



