While it's tangential to our interest in Milton's Sin, the iconography of Medusa does offer a few suggestive parallels -- a beauty who was turned into a snaky horror, who also became, in some legends, the protectress of the fruits of an earthly paradise:
Originally a beautiful maiden, she was raped by Neptune in the temple of Minerva. That goddess of culture and society, outraged, transformed Medusa's famous golden hair into a nest of serpents and decreed that anyone looking on her would be turned to stone. Medusa was then banished to an ambiguous place in the west, where Perseus later went to slay her with the help and encouragement of Minerva especially.
…certain received facts in the myth of Medusa suggest her association with poetry and the earthly paradise. Some traditions assert that when she was cursed by Minerva she became the guardian of the golden apples of the Hesperides, the fabulous western islands of the earthly paradise. All the legends agree, moreover, that at her death the winged horse Pegasus, traditional symbol of poetic inspiration and energy, sprang forth from her body.
Apollodorus tells us that she had two blood systems and that the physician Asclepius* collected some of each after her death. The one he used to revive the dead, the other to destroy his enemies.
Minerva as well recognized this deathless Medusan force and sought to appropriate it for herself: the aegis of her power, represented on her famous shield, is the Medusa's head.
*This story about Asclepius also turns up in the tale of Ophiucus.

