Quantitative and specific distribution of ostracodes are dependent on the physical and chemical limitations imposed by their environment, which in turn are controlled by geological, hydrological, botanical, and climatic factors. Once the nature of these controls has been defined for a region, the ecological limitation of specific ostracodes can be determined. Knowing the ostracode's tolerance limits then allows one to reconstruct the environments of the past, through paleoclimatic, paleoecologic, paleogeologic, and paleohydrologic interpretations.