Italian, circa 1800

Thetis was a sea goddess and leader of the Nereids in Greek mythology, one of the 50 daughters of Nereus and Doris. Zeus and Poseidon both desired her, but a prophecy warned that her son would surpass his father in greatness Thetis would bear a son greater than his father. To prevent this, she was married to the mortal Peleus.

Thetis is most famous for being the mother of Achilles, but she may also have been one of the earliest deities worshipped in Archaic Greece. Evidence suggests she was venerated in Laconia, where a cult centered around a wooden image of her was established.

A similar but vertical composition of Thetis riding a Hippocamp is found on a 17th century gem from the Medici Collection, housed at the Museo degli Argenti, Florence (inv. no. 1637).