A new dinoflagellate cyst, Pterocysta cruciformis Rochon gen. et sp. nov., is described from glacial Late Pleistocene sediments of the southwestern Black Sea and the central Marmara Sea. Pterocysta cruciformis is distinguished by a S-type paratabulation, the cruciform shape of the endocyst and the presence of a prominent narrow wing-like peri-phragm on the ventral side. Similarities between Pterocysta cruciformis and other camocavate cysts are discussed. The new species is associated with cold climatic conditions and probably indicates brackish to fresh water conditions.