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FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



tin and E. C. Jones. I wish also to thank Dr. 

 Paul lllg for his advice during the course of 

 the work, Dr. Thomas E. Bowman for review- 

 ing the manuscript, and my wife, Joan, for 

 assistance in completing the drawings. 



MATERIALS 



The present report is based on the examina- 

 tion of 14 plankton samples collected between 

 5° N. and 5° S. latitude and between 130° E. 

 and 120° W. longitude in the Pacific Ocean 

 (fig. 1). The pertinent data associated with 

 each plankton collection are presented in table 

 1. Hydrographic data associated with these 

 collections are given by King, Austin, and Doty 

 (1957) for the research vessel Hugh M. Smith, 

 cruise 31, and by Austin (1957) for cruise 85. 

 Processed reports containing hydrographic data 

 have been issued for Orsom cruise 56-4 (Le- 

 gand, 1957), for Stranger and Horizon cruises 

 (Scripps Institution of Oceanography, 1957), 

 and for Satsufna and Kagoshima cruises (Japa- 

 nese Hydrographic Office, 1956). 



Four of the 14 samples (Smith cruise 31, 

 stations 94, 144, 178, and cruise 47, station 31) 

 were obtained from the recently discovered 

 equatorial undercurrent (Knauss and King, 

 1958) by means of closing net gear. In addi- 

 tion, one oblique tow {Smith cruise 35, station 



63) apparently passed within the undercurrent 

 at least during part of the tow. 



The three samples obtained on cruise 47 were 

 oriented with respect to the undercurrent. One 

 sample (cruise 47, station 31) was collected 

 within the current, and the other two were ob- 

 tained from below it (cruise 47, station 29) 

 and from above it (cruise 47, station 30). 



Six collections (Smith cruise 35, station 63, 

 Stranger 34, Orsom 10, Horizon 32, Satswma 

 32, and Kagoshima 613) were selected from a 

 large number of plankton samples obtained by 

 vessels participating in a large scale quasi-syn- 

 optic study (Operation Equapac) in Pacific 

 equatorial waters. The samples used in the 

 present studies are those obtained nearest to 

 the Equator by each of the vessels. 



METHODS 



Owing to the large volume of most of the 

 samples, except Kagoshima 613, it was not 

 practical to examine the entire contents of each. 

 In order to estimate the percentage represen- 

 tation and the numerical abundance of the 

 common species, small quantities of the orig- 

 inal samples were examined. These sub-sam- 

 ples, the sizes of which are given in table 2, 

 were obtained by means of a plankton splitter 

 (McEwen, Johnson, and Folsom, 1954). On 



Table L — Plankton station data 



1 ZT, zone time; LT, local time; GMT, Greenwich mean time. 



2 CN, closing net: Qt oblique open net; V, vertical open net. 



