A Hawaiian Rough-Spined Sea Urchin (Prionocidaris Hawaiiensis), sits at rest displaying its spines-on-top-of-spines, an endowment that give it another common name–the Thorny Sea Urchin. This particular species of prionocidaris is endemic to the Hawaiian islands.
You can see some intriguing close up shots of the microscopic life living on and in a similar sea urchin itself on Reef Guide’s site.
Location: University of Hawaii Institute of Marine Biology. Credit: Photo Collection of Dr. James P. McVey, NOAA Sea Grant Program