Scylla  (sill ´a ), and Charybdis  (ka-rib ´dis ).—The names of two rocks, opposite to one another, between Italy and Sicily. In the one nearest to Italy was a cave in which dwelt Scylla, who was a terrible creature (female) with six long necks and heads, each of which contained three rows of sharp teeth, twelve feet, and barking like a dog. On the opposite rock, Charybdis, dwelt a being of the same name under an immense fig tree. Thrice a day she swallowed the waters of the sea and thrice threw them up again. Between these rocks, Scylla and Charybdis, the sea was very narrow and very dangerous. Hence mariners had to exercise great vigilance lest while avoiding Scylla they did not fall on Charybdis. This last expression is often used in speaking of cases where a middle course has to be carefully steered between two threatening difficulties.