The author is much indebted to F.J. Rohlf of the State University of New York, USA, and R.A. Reyment of the Swedish Natural History Museum, for their kind help throughout the course of the present study, valuable comments on the statistical terminology, as well as critical reading of the manuscript. My deep appreciation is due to M.A. Bassiouni and W.M. Abdel Malik of the Geology Department, Faculty of Science, Ain Shams University, Egypt, for their encouragements and continuous help. My deep gratitude is due to T.M. Puckett of Alabama University, USA, A. Lord (UCL, UK), chairman of the International Research Group on Ostracoda, and E. Brouwers of the US Geological Survey, for their critical reading of the manuscript. A special word of thanks is due to Omima H. El Sabainy, Central Lab for Microanalysis, Minia University and Fatma Mostafa of the Geology Department, Faculty of Science, Minia University, Egypt, for photographic assistance. Finally, I would like to thank all the editors of PE (especially W. Hagadorn and J. Rumford) for devoting much time to improving my paper.