The De Stefani collection represents a very important historical, museological and scientific heritage of the Natural History Museum of Florence. the collection counts approximately 1000 specimens total samples: 1012, for a total number of specimens: 982) of a fossil macroflora collected by carlo De Stefani at the end of the 19th century in the Upper Paleozoic. graphite-rich metapelites and metasandstones of the San Lorenzo Schists Formation in the Pisani Mountains. The fossil species together with the geology and stratigraphy of this area of Tuscany, are described in the monograph "Flore carbonifere e permiane della Toscana". The San Lorenzo Schists formation as a whole, was referred by previous authors to a fluvial-lacustrine environment. The museological reorganisation and a general overview of this collection is the first stage of a project aimed at carrying out a detailed stratigraphic and paleoenvironmental study. A new 110.000 scale geological survey of the San Lorenzo Schists in the valle del Guappero type-area (see enclosed geological map) has been accomplished, during which the classical fossil localities were precisely positioned on the map; new localities characterized by the occurrence of marine fossils were also found. Many of the correspondent specimens figured in De Stefani's monograph have been round in the collection (i.e. no. 51 specimens/85 figures). The results of our studies indicate a relevant taxonomic diversity, mostly among terms and sphenophytes, and point to an intertropical humid climate. These preliminary data improve the knowledge of the paleoenvironmetnal scenario of Tuscany during the Late Carboniferous.