4 U.S. NATIONAL MUSEUM BULLETIN 236 



such a way that comparison is facilitated. All drawings have been 

 made with a camera lucida and show a certain formalization: unim- 

 portant details have been omitted in order not to obscure the essential 

 points. This applies particularly to the setae, the plumosity of which 

 usually has not been represented. 



All the material, including type specimens and slides, has been 

 deposited in the U.S. National Museum of the Smithsonian Institu- 

 tion. Before each dissection the animal was stained in a weakly 

 alkaline solution of Chlorazol Azurine or Chlorazol Black E (Edward 

 Gurr, London). The dissected parts were mounted in "Berleze." 



In the enumeration of the species of the various genera, a trivial 

 name in parentheses (usually only one of the sexes) indicates that 

 this particular stage has been mentioned but not actually described. 

 The use of parentheses in the lists of measurements indicates the 

 average in a series of length measurements. 



I want to express my sincere gratitude to Dr. Fenner A. Chace, Jr., 

 Curator, Division of Marine Invertebrates, U.S. National Museum, 

 who originally suggested that I should study the Ifaluk copepods and 

 who, in various ways, has stimulated this work. Financial support 

 from the Pacific Science Board (National Academy of Sciences- 

 National Research Council), for which I would like to convey my 

 thanks to the authorities concerned, greatly facilitated this study. 

 Gratitude is also due to Dr. H. Boschma, Dr. L. D. Brongersma, and 

 Dr. L. B. Holthuis, all of the Rijksmuseum van Natuurlijke Historic, 

 Leiden. Finally, I am indebted to Miss M. L. A. van Welij for her 

 care in preparing the typescript. 



Collecting Localities 



81-A-3-d. Sept. 28, 1953. Washed from beds of alga Lyngbya, 

 lagoon shelf, sandy bottom, near patch of reef about 100 ft. from 

 lagoon shore. Lagoon shelf W. of SW. end of Falarik Islet. Depth 

 about 6 ft. Coll. D. P. Abbott. 



Ifanella chacei, new species Metamphiascopsis hirsutus (Thompson 



Eudactylopus fasciatus Sewell and Scott) 



167-D-7. Oct. 25, 1953. Washed from Halimeda. From bottom 

 of ship passage between Falalap and Ella islets, near the W. tip of 

 Falielang (the reef extending W. from the W. shore of Falalap Islet). 

 Depth 13-14 ft. CoU. Yaniseiman, Bakalimar, and R. Harry. 



Peltidium intermedium A. Scott 



194-E-5. Oct. 10, 1953. Plankton haul, surface water of open la- 

 goon, taken at 2100-2300 hours. Coll. D. P. Abbott. 



Centropages orsinii Giesbrecht Oithona oculata Farran 



Acartia tonsa Dana 



