We came across lots of these creatures while walking at low tide on the beach east of Memories Caribe Resort. They are also known as Cake Urchins. Officially they are called a Clypeaster. These were pretty big, so they might have been Clypeaster Rosaceus. It is interesting how they cover themselves with shell fragments and grass bits, which makes sense since grass and debris are what they eat. Apparently while feeding they grind up sand into smaller bits. It makes you wonder how much they have contributed to the beautiful sandy beaches over millions of years?
When they bury themselves in the sand they are very hard to distinguish from their surroundings.