NO. 3583 COPEPODS — GRICE AND HULSEMANN 9 



Intermediate water, then eastward into the southwestern Indian 

 Ocean, and finally northward into the northern Indian Ocean by the 

 Antarctic Intermediate water. Citing S0mme's (1933) view that the 

 number of species in a current will decrease in the downstream 

 direction, Sewell examined the occurrence of deep-water copepods at 

 five stations in the Arabian Sea, the Gulf of Aden, and the Gulf of 

 Oman. He indicated that the samples probably came from the 

 Antarctic Intermediate water. He noted a gradual reduction of both 

 deep-sea and North Atlantic copepods in a northward direction; i.e., 

 the number of copepod species decreased from a maximum of 70 

 (including 56 North Atlantic species) to a minimum of 20 (12 North 

 Atlantic species) . The minimum number and the next to the minimum 

 number of species were found in collections obtained in the Gulf of 

 Aden and the Gulf of Oman, respectively. De Decker and Mombeck 

 (1965) cited SeweU's Arabian Sea data and then apphed Sewell's 

 technique of examining the contribution of North Atlantic species to 

 an even larger section of the Indian Ocean. These authors compared 

 the number of Atlantic species (134) they found in the bathypelagic 

 fauna of the southwest IncUan Ocean with the number of Atlantic 

 species found in the contents of six midwater trawl hauls (described 

 by Sewell, 1929, 1932) made in the area between the Laccadive Sea 

 and west of Andaman Island in the western part of the Bay of Bengal. 

 De Decker and Mombeck pointed out that a gradual decrease of 

 Atlantic species (20 to species) occurred in a northerly and easterly 

 cUrection. 



Our transect of stations extending from approximately 1S°N to 

 40°S along 65°E and 70°E, and one station at 29°S 49°E, in conjunc- 

 tion with the three different methods of collecting deep-water copepods 

 has permitted us to sample a large number of deep-living calanoid 

 species. We have specifically identified 269 species of calanoid cope- 

 pods excluding the new species and those species found in two Be net 

 collections made in the eastern Indian Ocean (80°E). As we pro- 

 gressed in our taxonomic analyses of the samples, the similarity of 

 the deep Indian Ocean copepod species to those of the Atlantic 

 became clear. Of interest to us was the appearance of 13 of the 18 

 species we had recently described from the northeastern Atlantic 

 (Hulsemann and Grice, 1963; Grice and Hulsemann, 1965). 



Since our sampling program provided more systematic coverage 

 of bathypelagic species than that of either Sewell (1929, 1932, 1947) or 

 De Decker and Mombeck (1905), it is possible to look more closely 

 into the occiurence of North Atlantic copepod species in the western 

 Indian Ocean. For this analysis we have determined the number 

 of copepod species in our samples in each of 10° latitude intervals 



