Scyla or Scylla: How To spell?

The word Scyla is misspelled against Scylla, a noun meaning "A dangerous rock on the Italian coast opposite the whirpool Charybdis on the coast of Sicily, -- both personified in classical literature as ravenous monsters. The passage between them was formerly considered perilous; hence, the saying "Between Scylla and Charybdis," signifying a great peril on either hand."