Answer:
Book lungs
Explanation:
The horse shoe crab has a hard outer surface carapace which has the shape of a horse shoe.
It has book lungs which come in 5 sets. The lungs are usually found on the ventral side of the crab.
The book lungs acts as gills which is used in breathing when the horseshoe crab is in water . The book lungs also helps the crab to breathe on land for a certain period of time provided the lungs are moist.
