(Κέρβερος), the many-headed dog that guarded the entrance of Hades, is mentioned as early as the Homeric poems, but simply as " the dog," and without the name of Cerberus. (Il. 8.368, Od. 11.623.) Hesiod, who is the first that gives his name and origin, calls him (Theog. 311) fifty-headed and a son of Typhaon and Echidna. Later writers describe him as a monster with only three heads, with the tail of a serpent and a mane consisting of the heads of various snakes. (Apollod. 2.5.12; Eurip. Here. fur. 24, 611; Verg. A. 6.417; Ov. Met. 4.449.) Some poets again call him many-headed or hundred-headed. (Hor. Carm. 2.13. 34; Tzetz. ad Lycoph. 678; Senec. Here. fur. 784.) The place where Cerberus kept watch was according to some at the mouth of the Acheron, and according to others at the gates of Hades, into which he admitted the shades, but never let them out again.