Caption:
Neptune, Roman god of rivers and the sea, holding a trident and riding a chariot drawn by seahorses. Neptunus. Engraved on agate and dactylotheca from the collection of Algernon Percy, First Earl of Beverley. Mezzotint copperplate engraving by John Spilsbury from his Collection of Fifty Prints from Antique Gems, John Boydell, London, 1785.