Triplofusus giganteus, previously known as Pleuroploca gigantea, common name the Florida horse conch, is a species of extremely large predatory subtropical and tropical sea snail, a marine gastropod mollusc in the family Fasciolariidae, the spindle snails, tulip snails and their allies.

Although known as a horse conch, this is not a true conch, as it is not in the family Strombidae.

This species is the largest gastropod in the American waters, and one of the largest univalves in the world.

The shell reaches upwards of about two feet.

Photo via The Charnel House on tumblr.
Quoted text via Wikipedia.