MARMORA (anc. Proconnesus), an island in the sea of the same name. Originally settled by Greeks from Miletus in the 8th century B.C., Proconnesus was annexed by its powerful neighbour Cyzicus in 362. The island has at all times been noted for its quarries of white marble which supplied the material for several famous buildings of antiquity (e.g. the palace of Mausolus at Halicarnassus).
See C. Texier, Asie mineure (Paris, 1839-1849); M. I. Gedeon, Προικόννησος (Constantinople, 1895); an exhaustive monograph by F. W. Hasluek in Journ. Hell. Stud., xxix., 1909.