Abstract: In the present study, the determination and stratigraphic evaluation of the ostracode fauna of thesedimentary rocks of Montian-Cuisia n age exposing at south of:Polatlı, are carried out, and a systematicdescription of new species is given.At the bottom of the Lower Paleogene sequence in the region, takes place the «Mollaresul Formation» of UpperJurassic age. Abovethes unit, the Kartal(Montian), Kirkkavak (Thanetian-Ilerdian) and Eskipolatlı (Cuisian) formations come with a total measured thickness of 1230 m. The whole sequence is unconformably overlain by theAğasivri Formation of Neogene age.Five of the 44 ostracode species of this study, are found to be new, and described here in a systematic order,and a chronostratigraphic and ecostratigrapliic evaluation of the fauna is also given.