Centipedes are crawling creatures with many pairs of legs. They are most active at night time, and hide under things during the day. Centipedes can move very fast, and eat insects. Their bite is poisonous and can be very painful, but isn't strong enough to kill a person. Centipedes are often confused with millipedes.
Horseshoe crabs are more closely related to spiders and scorpions than to crabs. They have six pairs of legs, a hard shell that looks like a horse's hoof, and a long tail. Their first pair of legs are very small and are used for putting food into their mouths.
Horseshoe crabs are called a living fossil because there are fossils of almost identical creatures found that are 230 million years old.
The two horseshoe crabs in the picture are upside down.
Millipedes are a type of creature that has many body segments, and two pairs of legs on each segment. They are related to centipedes, but they move a lot slower. Centipedes have only one pair of legs per segment.