Limulus polyphemus. A true "living fossil", this representative of the class Meristomata is one of only five living still in existence. The crab is the most widely studied Meristomata because of their large compound eyes and their copper-based blue blood. It thrives in a marine aquarium such as WARD’S Marine Touch Tank. Culture instructions are included. Size: 1–3". Note: Shipped overnight. Additional shipping fee applies.