Having petrified Cetus , the sea monster threatening Andromeda , Perseus placed Medusa 's head on the riverbank while he washed his hands .
The origin of coral is explained in Greek mythology by the story of Perseus .
Having petrified Cetus , the sea monster threatening Andromeda , Perseus placed Medusa 's head on the riverbank while Perseus washed Perseus ' hands .
The origin of coral is explained in Greek mythology by the story of Perseus .