In pauper graves or stones with unknown or unidentified, please place the name Unknown as a surname.  DO NOT USE Jane or John Doe unless this is on the stone.  In this case, place it in quotations and use the name Unknown as a surname. 

For unidentified military graves please read the following article: Blank Military Stones

For stones with first names, but no visible last names please read the following article: No surname found on the stone