The southwest coastal region of Florida offers one of the richest sequences of shelly marine faunas representing the last five million years of biological evolution in the region. This interval is of great interest because of its fundamental environmental and biotic changes including closure of the Panamanian seaway, reorganization of the Gulf Stream, severing of the Pacific-Atlantic connection between marine faunas and the interchange of North and South American land faunas. Recent work by Florida State Museum parties has shown that potentially rich land animal samples interfinger with the well- known marine mollusk faunas in southwest Florida. These vertebrate samples will be enlarged and studied, and they are expected to greatly improve the precision of present dating of the entire late Neogene sequence in the region. At the same time, intensive analysis of the largely neglected gastropod mollusks in the marine faunas will be undertaken. A relatively new approach to checking the correlation of these same marine and non-marine faunas will be tried, using strontium isotope ratios, in comparison with the sequence based on world-wide marine readings. This work is urgent because the major excavations now open will be closed and forever buried in about two years.
