These two “miserable brothers” are Alessandro and Napoleone, sons of Alberto degli Alberti, lord of Falterona in the valley of the Bisenzio. After their father’s death they quarrelied, and one treacherously slew the other. ↩

Caina is the first of the four divisions of this Circle, and takes its name from the first fratricide. ↩

Sir Mordred, son of King Arthur. See Le Mort d’Arthure , III ch. 167:⁠—

“And there King Arthur smote Sir Mordred under the shield with a foine of his speare throughout the body more than a fadom.”