8 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 122 



pelagic families, were found in the NV samples collected below 

 1000 m. 



The vertical range of many of the species in the 2000-1000 m in- 

 terval extends into depths of less than 1000 m. Notably among 

 these are species in the large families Aetideidae, Scolecithricidae, 

 Lucicutiidae, and Aiigaptilidae. Each of these families is represented 

 in our collections by 15 or more species. 



Nine families of copepods had one-half or more of their species 

 represented in depths below 2000 m. Only one family (Bathy- 

 pontiidae) had more than one-half of its species (6 of 11) restricted 

 to depths greater than 2000 m. The range of 9 of the 16 species 

 in the family Spinocalanidae extended below 2000 m, but only 1 

 species was found exclusively below this depth. Species in these 

 last two families are typical of collections made below 2000 m. 



Concerning the 153 species, the largest number was found in the 

 2000-1000 m depth interval (122), an intermediate number in the 

 3000-2000 m interval (73), and the least number in the 4000-3000 m 

 interval (13). A similar decrease in species diversity with increasing 

 depth was noted by us (Grice and Hulsemann, 1965) in the north- 

 eastern Atlantic, where the decrease in diversity was as follows: 2000- 

 1000 m (71), 3000-2000 m (59), and 4000-3000 m (28). In the 

 Indian Ocean seven species were continually distributed from 1000 

 to 4000 m: Mimocalanus cuUrifer, Spinocalanus abyssalis, S. magnus, 

 Metridia discreta, M. princeps, Lucicutia longiserrata, and Haloptilus 

 longicornis. Except for L. longiserrata, which we misidentified 

 in our Atlantic samples (see Hulsemann, 1966), these species also 

 occiu-red below 1000 m in the northeastern Atlantic. The first 

 four we recorded in samples collected in excess of 4000 m. 



Zoogeography 



Geographic distribution of species. — Sewell (1948) has dis- 

 cussed the geographic distribution of copepods in some detail. His 

 account represents an intensive analysis of the literature and attempts 

 to relate the distribution of copepods to ocean currents. The dis- 

 cussion of the copepods in the Indian Ocean is based largely on his 

 own numerous studies made there. A considerable section of his 

 study is devoted to the deep-living copepods of the western Indian 

 Ocean. We are mainly interested here in this discussion and that 

 included in a recent paper by De Decker and Mombeck (1965) as 

 these appear to be the only accounts concerning the zoogeogi'aphy 

 of the deep-living copepod species of the Indian Ocean. 



Sewell (1948) recognized many North Atlantic Ocean species in the 

 northern Indian Ocean. He indicated that these species may be 

 carried southward from the North Atlantic by the North Atlantic 



