Paleontologists working in Tertiary oil fields are using smaller forminifera as effective tools in correlation of strata., It seems, however, only one face of fauna, i., e., qualitative face, is being considered in the form of range chart, or distribution chart, which may be called "a qualitative analysis., " The author expressed the necessity of another face of fauna, that is "quantitative" in character., The quantitative analysis means a statistic analysis of fauna which is a new branch of Paleosynecology., Foraminiferal fauna to be stndied by this method should be treated statistically, and after numbering individuals and species of foraminifera, paleosynecological considerations will be done to assemblages., The author discussed in this paper, 1) Necessity of statistical method in applied paleontology of oil field, 2) Sampling method, and 3) Method of statistical studies in general.,