One species of extinct Trilobite. The modern horseshoe crab is the living animal for this species. There are 4 living horseshoe crabs: one species living on the eastern seaboard & the gulf of Mexico and the other 3 live in Southeast Asia. Horseshoe Crab, Petrified Wood, Gems And Minerals, Prehistoric, Dinosaurs, Rocks, Play Dough, Extinct, Crabs