Thanks for the information, Bob, and Cannonmn. Max, now that you mention it, I can see that you are definitely right, the figure is riding on the back of some type of sea serpent. When I first saw the photo, I didn't save and enlarge the pic because it was already pretty clear, but I kept trying to figure out why Poseidon was holding a bouquet of flowers on his belly; what did this symbolism mean? Well, now I know that that isn't a bunch of flowers, it's the sea creatures head.