The source for the mythological subject represented in this painting is an episode from Ovid's Metamorphoses , book IV. Andromeda is chained to a rock with the sea-monster approaching , to which she has been offered as a sacrifice by Neptune . A skull and some bones are scattered in the foreground, announcing her likely fate. Perseus mounted on Pegasus, the winged horse, and is coming to rescue with his sword outstretched. Size: 39.1 x 31.2 cm