142 



KAY AND JOHNSON 



From the Holocene record, 65% survive today on 

 Enewetak. 



Of the 140 extinct species listed by Ladd (1966, et 

 seq.), 84% became extinct in the Miocene, 14.8% in the 

 Holocene. The Enewetak record may be contrasted with 

 that reported by Newman (1986) who calculated from 

 Ladd (1982: Table 4) that of 126 extinctions since the 

 Eocene, 56 or 44.4% became extinct in the Pleistocene 

 and only five (3.5%) of the extant species survived from 

 the Miocene. This last figure is too low for Enewetak and 

 may be peculiar to the fossil record of Fiji and the New 

 Hebrides (Vanuatu). 



There is no single pattern of extinction and survival 

 such as Wells (1982) found for the Midway corals, where 

 at the end of the Miocene there was complete replacement 

 of the Miocene genera. At Enewetak, the Turbinidae and 

 Rissoidae show a pattern in which equal numbers of 

 species have been extinct since the Miocene, occur both in 

 the Miocene and today, and appear only in the modern 

 record. The trochid, neritid, and littorinid records, in con- 

 trast, are almost entirely modern. 



ACKNOWLEDGMENTS 



The checklist of Enewetak mollusks (Table 1) is based 

 on the references cited in the Introduction, the Enewetak 

 collections in the USNM, the EMBL reference collection 

 (now housed at the B. P. Bishop Museum, Honolulu, 

 Hawaii), material collected for an earlier checklist by A. S. 

 Bernstein and A. Miller which has been incorporated into 

 the Enewetak collections at B. P. Bishop Museum, and 

 observations by the authors. These observations are based 

 in part on examination of private shell collections of mili- 

 tary personnel stationed at Enewetak between 1978 and 

 1983. We are especially grateful to Carol Hopper, Richard 

 Houbrick, and the late Joseph Rosewater for their contri- 

 butions to the checklist. 



Numerous people have contributed to the listing 

 through collection and/or identification of mollusks from 

 Enewetak and by way of their assistance with the 

 literature. Among them are A. Adams, H. Bertsch, 

 W. O. Cernohorsky, C. Christensen, P. Colin, the late D. 

 Devaney, A. Ferreira, R. Houbrick, J. Lamberson, 

 J. Le Renard, V. O. Maes, W. B. Rudman, E. Vokes, 

 and T. Waller. Lisa Boucher and Lori Bell have been of 

 particular help in locating unrecorded species. Special 

 thanks go to Rich Nakagawa for the use of his unpublished 

 listing of Kwajalein shells and to Jeannete Hammon, Karen 

 deCroff, Dave Johnson, D. J. MacDonald, Lee Rousseau, 

 and Jim and Judy Wedge for additional information and 

 assistance in finding Kwajalein material. 



The senior author is grateful to Kenneth Boss and 

 Ruth Turner of the Museum of Comparative Zoology, 

 Harvard University; Philippe Bouchet, Laboratoire des 

 Invertebres marins et de Malacologie, Paris; George Davis, 

 Academy of Natural Science, Philadelphia; Oliver Paget 

 and Erhard Wawra, Naturalhistoriske Museum, Vienna; the 

 late Joseph Rosewater, Department of Invertebrates, U. S. 



National Museum, Smithsonian Institution; and J. D. Tay- 

 lor, Mollusca Section, British Museum (Natural History), 

 London, for permission to utilize the collections in their 

 care. 



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