ANASTASIUS BIBLIOTHECARIUS:  One of the few important men among the Roman clergy in the middle of the ninth century; d. 879. He grew up in Rome, and inherited from his uncle Arsenius (whose visits to the Carolingian courts in 865 had such an important influence on the development of the papal power) close relations with both the spiritual and secular powers of the day.  He was for some time abbot of what is now Santa Maria in Trastevere, and about the end of 867 Adrian II. made him librarian of the Roman church.  In 869 Emperor Louis II. sent him to Constantinople to arrange the marriage of his daughter Irmengard with the eldest son of Basil the Macedonian.  Here he attended the last session of the eighth ecumenical council; and when the acts of the council, entrusted to the Roman legates, were taken from them by pirates on the homeward journey, he supplied a copy of his own.  He seems to have influenced John VIII. in favor of his friend Photius.  Hincmar of Reims begged his intercession, which was successful, with Adrian II.  The references in Hincmar's writings seem to identify the librarian with the cardinal-priest of St. Marcellus who was the iconoclastic candidate for the papacy in 855, and was several times excommunicated. (On the question of his part in the compilation of the Liber Pontificalis see LIBER PONTIFICALIS.) His Chronographia tripartita is important for its influence on the study of general church history in the West. In a rough age, when East and West were drifting further asunder, he labored zealously to make the fruits of Eastern culture accessible to the Latins.  Most of his works are in MPL, cxxix.; the Chronographia tripartita is in Theophanis chronographia, ed. C. de Boor, Leipsic, 1883, pp. 31-34b.