Large Dried, Molted Atlantic Horseshoe Crabs for Sale, found in the Atlantic Ocean.  These large dried molted horseshoe crabs will measure between 11 and 13 inches long from the edge of the head to the tip of the tail. They may have some sand inside them and some are empty on the underside of the crab. Some are ALL NATURAL and have algae, hard sand and have not been sprayed with a clear sealant.   They are also known as the American horseshoe crab. Scientific name: Limulus polyphemus and can be found on the American Atlantic coast and in the Gulf of Mexico.  A horseshoe crab is built like a tank! Its heavily-armored exterior protects the vulnerable parts inside. Despite their name, horseshoe crabs, are not crabs but are members of the order Xiphosura and are more closely related to  scorpions, spiders and ticks, than they are to true crabs. For the horseshoe to grow larger, it must molt and shed its shell. These "molts" can sometimes be found near tidal flats. After its third or fourth year it sheds its skin annually, sometime during July or August.