- 2 7 - 



At every point these currents are giving off water from their 

 seaward (left) side which falls into the abysses and forms the 

 strictly abyssal water ; this process is far more marked in the 

 southern hemisphere than in the northern. 



In the southwestern portion of these basins abyssal water 

 is constantly rising and flowing southward to take the place 

 of the water lost from the antarctic circulation through the 

 Humbolt, Benguela and Australian currents. 



In the central portions of these basins the general motion 

 of the water is from east to west, the water lost from the 

 northerly currents crossing the abysses and being picked up by 

 the southerly currents on the opposite shores. This circulation 

 of water in the central part of the basins is much more rapid 

 in the southern than in the northern hemisphere. 



The water of the circumpolar west wind drift of high 

 southern latitudes, north of the true antarctic current, is 

 mainly surface water from the north caught up and driven 

 forward by the strong wind. This west wind drift forms a 

 band dividing the abyssal antarctic circulation from the surface 

 circulation further north. 



By this drift many organisms, pelagic at some stage of 

 their existence, or capable of clinging to floating objects, are 

 distributed throughout the southern latitudes, though they 

 are unable to withstand truly antarctic conditions ; and to this 

 is largely due the similarity of the faunas of southern Africa, 

 southern South America, southern Australia and New Zealand. 



The shallow water crinoids of South Africa are very 

 different from those of southern Australia, and could not have 

 been at any time part of the same fauna ; both faunas are 

 derived from the much richer faunas lying immediately to the 

 northward of them. The crinoids of southern South America 

 are entirely antarctic, and have nothing whatever in common 

 with the crinoids of South Africa or of southern Australia, but 

 are derived from the abyssal types of the Indian Ocean. 



(285) 



