The Fountain
The central figure of the fountain, in front of a large niche, is Neptune, god of the sea. He is riding a chariot in the shape of a shell, pulled by two sea horses. Each sea horse is guided by a Triton. One of the horses is calm and obedient, the other one restive. They symbolize the fluctuating moods of the sea. http://www.aviewoncities.com/rome/trevi.htm