1. School of Oceanography, Oregon State University, Corvallis 97331
2. Scripps Institution of Oceanography, La Jolla, California 92037
3. Instituto Mexicano del Petroleo, México 14, D.F.
4. Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543
5. Geologisches Institut, 74 Tubingen, Federal Republic of Germany
6. Lamont-Doherty Geological Observatory, Palisades, New York 10964
7. Scripps Institution of Oceanography
8. Universidad Nacional Autónoma de México, México 20, D.F.
9. School of Oceanography, Oregon State University
10. Department of Geology, Stanford University, Stanford, California 94305
11. Centro de Investigación Cientifica y de Educación Superior de Ensenada, Oceanografia, Ensenada, Baja California, México
12. Department of Geology, Dickinson College, Carlisle, Pennsylvania 17013
13. Instituto Mexicano del Petroleo
14. Department of Geology, Bedford College, London NW1 4NS, England
15. University of California, Los Angeles 90024