Image from Torpedo 2005 Marine Life News Bulletin

True Crab

Image from SUNY Cortland

Horseshoe Crab

True crabs and horseshoe crabs are part of the phylum Arthropoda. Most of the creatures in this phylum have bilateral symmetry, their appendages are joined, and have a complete digestive system. Horseshoe crabs come from a very ancient phylum, which includes things like the extinct water scorpion. The subclass Merostomata, which is horseshoe crabs, is primarily found in marine habitats. True crabs come from the subphylum Crustacea, and has a pair of antennae.