CHELICERATA/MEROSTOMATA
Among the three subphyla in the Arthropod phylum, the Chelicerata subphylum contains two classes of animals, the Arachnida (spiders, scorpions, ticks, and mites) and the Merostomata (horseshoe crabs).

With a "horseshoe"-shaped outer shell serving as protection, horseshoe crabs are one of the few contemporary members of the Merostomata class. Using their spike-shaped tail to help them move and explore, they feed on worms, mollusks, and other ocean-floor invertebrate species.

During the spring in the mid-Atlantic in North America, huge numbers of horseshoe crabs invade shallow intertidal areas where they lay their eggs. The abundance of eggs serves as a vital food resource for migrating shorebirds traveling north to breeding grounds.