Crab trouble
though called a "crab', the horseshoe crab is not really one in essence. It derives its name from shape of its shell, which closely resembles a horse's hoof. While most crabs have two pairs of antennae, a pair of mandibles or jaws and five pairs of legs, the horseshoe crab can only boast of small pincers in the front for maneuvering its food. It lacks the antennae and the mandibles. The most arresting feature of the species is its nine eyes and consequently, the horseshoe crab has one of the largest optic nerves in the animal kingdom.
Once widespread and flourishing in the Paleozoic Era, just four species of Horseshoe crabs survive today. These belong to three genera: Limulus, Carcinoscorpius and Tachypleus. And all three belong to the family Limulidae , also known as "Living Fossil'. Limulus and Carcinoscorpius has one species each