Ovid Metamorphoses Book IV:563-603 Cadmus and Harmonia become serpents
The son of Agenor, Cadmus, did not know that his daughter and little grandson were now sea-gods. Conquered by the pain of this run of disasters, and daunted by all he had seen, the founder departed his city, as if the misfortunes of the place and not himself were oppressing him. Driven to wandering, at length his journey carried him and his wife to the borders of Illyria. Now, weighed down by age and sadness, they thought of the original destiny of their house, and in talk reviewed their sufferings. Cadmus said ‘Surely that snake, my spear pierced, must have been sacred, when, fresh from Sidon, I scattered the serpent’s teeth, a strange seed, over the earth? If that is what the gods have been avenging with such sure anger, may I myself stretch out as a long-bellied snake.’ And, so speaking, he did extend into a long-bellied snake, and felt his skin hardening as scales grew there, while dark green patches checkered his black body. He lay prone on his breast, and gradually his legs fused together thinning out towards a smooth point. Still his arms were left to him, and what was left of his arms he stretched out, and, with tears running down his still human cheeks, he said ‘Come here, wife, come here, most unfortunate one, and while there is still something left of me, touch me, and take my hand, while it is still a hand, while the snake does not yet have all of me.’
He wanted to say so much more, but suddenly his tongue was split in two, and though he wished for words none came, and whenever he started on some plaintive sound, he hissed: this was the voice that Nature bequeathed him. Then, striking her naked breast with her hands, his wife cried out ‘Cadmus, wait, unhappy one, tear away this monstrous thing! Cadmus, what is it? Where are your feet? Where are your hands, shoulders, face, colour, everything – while I speak? Why do you not change me as well, you gods, into this same snake’s form? She spoke. His tongue flickered over his wife’s face, he slid between her beloved breasts as if known there, and clasped her, and searched about for the neck he knew so well. Everyone who was there (their comrades were present) was horrified, but she stroked the gleaming neck of the crested serpent, and suddenly there were two snakes there, with intertwining coils, until they sought the shelter of the neighbouring woods. Even now they do not avoid human beings or wound them, quiet serpents, remembering what they once were.