This paper is based on macrofossils obtained from core samples from 17 deep wells in Mississippi, distributed as follows: 8 in the Heidelberg field, 5 in the Eucutta field, 1 in Jones County, 1 in Simpson County, 1 in Jefferson Davis County, and 1 in Hinds County. The stratigraphic position of the significant fossils in the Eucutta and Heidelberg fields is shown diagrammatically in Figures 1 and 2. The presence of beds of Austin age is indicated by the following species: Inoceramus undulatoplicatus Roemer, Inoceramus aff. I. umbonatus Meek and Hayden, and Gryphaea aucella Roemer. Closely underlying the zone containing these species is a zone 160 feet or less in thickness characterized by the shells of Ostrea oleana Stephenson, a recently described species known only from hese wells. The presence of this oyster in wells as far apart as the Eucutta field and the J. R. Ball well No. 1 in Hinds County indicates that this zone is widespread in the subsurface in central Mississippi. Closely underlying the Ostrea oleana zone in several of the wells is a zone containing poorly preserved oysters that appear to belong to Ostrea sannionis White, a species known only from beds in northeast Texas corresponding in age with the base of the Austin chalk, and with beds of early Niobrara age in Utah. At a somewhat lower level were found poorly preserved ammonites questionably identified as Prionotropis, an upper Eagle Ford genus. Very imperfect shell impressions from the depth of 6,151 to 6,153 feet in the Helen Morrison well No. 1 in the Heidelberg field suggest species nown in the Lewisville formation in Texas.