Triton, the sea god, son of Neptune and Amphitrite, is here represented as a merman, although sometimes he is depicted at fully human. His scaly "legs" rise up above the open shell and he blows the typical trumpet-conch shell.
The base of this fountain is comprised of four dolphins. Also represented are papal symbols and bees--a specific heraldic symbol of the Barberini family. (Pope Urban VIII was from the Barberini family.)