10 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 122 



from 20°N to 40°S, A comparison of species found in the western 

 Indian Ocean and the North Atlantic is as follows: 



It is quite clear from examination of this tabulation that very large 

 numbers of so-called North Atlantic species are present at all latitudes 

 and that no significant decrease is evident m either the number of 

 species within each interval (north of 30°S) or in the number within 

 each interval that are also present in the North Atlantic Ocean. 

 Thus, Sewell's view of the "falling off" of deep sea copepods and 

 especially the reduction of North Atlantic species northwards in 

 the Antarctic Intermediate water in the northern Arabian Sea is 

 not supported by our data. Since the two stations where Sewell 

 found the least number of copepods are in the Gulf of Oman and 

 Gulf of Aden, the reduction of diversity at these stations may be 

 related to conditions present in these relatively constricted areas. 

 Other studies on the hydrography of the western Indian Ocean 

 may not entirely support Sewell's interpretation of water mass 

 distribution. Sewell's report of Antarctic Intermediate water in the 

 Arabian Sea is based on an investigation of Mohamed (1940) of pH 

 distribution. Sewell also cited the work of Moller (1929), which 

 indicated that northward flowing subpolar water (500-2000 m) 

 is traceable only to about 5°N (Moller referred only to the eastern 

 Indian Ocean). Sverdrup et al. (1942) indicated that Antarctic 

 Intermediate water and Bottom water flows north and mixes with 

 the deep water in the region north of the Equator. These water masses 

 then flow to the south. According to Ivanenkov and Gubin (1960), 

 in the area between 10° and 16°S the upper part of the southward 

 flowing North Indian Deep water mixes with northward flowing 

 sub-Antarctic Intermediate water and the lower part of the North 

 Indian Deep water mixes with Antarctic Bottom water. This mixing 

 results in the formation of two water masses: the South Indian 

 Deep water (1500-3500 m), which flows southward and North Indian 

 Bottom water (a layer of 200-700 m), which flows northward. Most 

 of the NV and Be net samples considered in this paper, which were 



* Present in our samples. 



<From Grice and Hulsemann (1965) and otlier literature records from North 

 of 0°. 



