Recently found materials of large beyrichiacean ostracodes from the Early Devonian of the Darlık, Korucuköy, and Kabalakdere sections in NW Anatolia stimulated the restudy of ostracode collections from the İstanbul area, including the Toula collection (GBA Vienna) and Endriss collection (previously in GPI Marburg and currently in SMF Frankfurt), and their biostratigraphical and palaeogeographical significance. | Notes on beyrichiacean ostracodes from the Early Devonian of NW Turkey and their palaeobiogeographical relations