of or pertaining to the biogeographic zone of the ocean bottom between the bathyal and hadal zones: from depths of approximately 13,000 to 21,000 ft. (4000 to 6500 m).
Of or relating to the region of the ocean bottom between the bathyal and hadal zones, from depths of approximately 3,000 to 6,000 meters (10,000 to 20,000 feet).