Echinothuriid Sea Urchin (Tromikosoma panamense)
The Tromikosoma panamense sea urchin has only been observed on a few occasions, and is not common at Axial. This specimen was seen at the base of Axial Seamount. These Echinothuriid urchins have a weakly calcified, more leathery test than most urchins. They are deposit feeders, moving over the sediment feeding on material that has settled onto the seafloor from the water column above, leaving distinctive tracks behind as they move on their tube feet.
References:
http://www.marinespecies.org/aphia.php?p=taxdetails&id=513622
http://www.mbari.org/benthic/echinoids.html