The biostratigraphic value of graptolites of Polish Silurian is discussed. This group makes possible a detailed zonation of deposits ranging in age from the Llandovery to the Ludlow the teintwardinensis Zone. Younger Silurian deposits of Poland divided into Siedlce and Podlasie Series and subsequently graptolite biozones, represent reference section for Upper Silurian of other regions. Shelly fauna of the Polish Silurian, sometimes accompanied by graptolites, indicates isolation of shelves of the Gondwanian and Fennosarmatian continents. An attempt is made to reconstruct the history of the Proto-Tethys Ocean separating the continents and its relation to the Proto-Atlantic.