Abul Hasan ali-ibn Muhammad Samarri (326 A.H. - 329 A.H.)  He was the last legate and succeeded Abul Qasim Husain ibn Ruh.  When he was asked about his successor, he said, "God now wills otherwise and the duration of such a period is known only to Him." 

A few days before he died, he had received a letter from the Imam al-Mahdi.  He died in 329 A.H. and his grave is one the Sharia Khalbakhi near the canal Nagrabi.