[Tombstones are placed on graves of unidentified refugees and migrants who drowned at sea during an attempt to cross a part of the Aegean Sea from the Turkish coast, in Lesbos]By Karolina Tagaris LESBOS, Greece (Reuters) - She drowned trying to reach Europe, but her headless body was never identified. Like others buried beside her in an olive grove on the Greek island of Lesbos, the marble plaque on her unmarked grave will proclaim the victim "Unknown". Sixty-four earthen graves have been dug in this land plot for refugees and migrants who drowned crossing the Aegean Sea trying to reach Europe.