Horseshoe crabs are closely related to crabs and even spiders. Their body divided into two sections (prosoma shaped like a horse shoe and opisthosoma) can be up to 60 cm long. The cephalothorax and abdomen are protected by the greenish-gray color carapace that is perfect for camouflage. The front edge of the carapace is pointed.
used to be my pet...
In all seriousness though. The last photo makes me sick.
incorrect. horseshoe crabs are not crustaceans at all and in fact are more closely related to mites, spiders, scorpions, etc.