This undated photo provided by Monterey Bay Aquarium and Research Institute, shows a mystery mollusc (Bathydevius caudactylus) observed by MBARI's remotely operated vehicle (ROV) Tiburon in the outer Monterey Canyon at a depth of approximately 1,550 meters. (MBARI via AP)

This undated photograph, provided by Monterey Bay Aquarium and Research Institute, shows a mystery mollusk (Bathydevius caudactylus), observed by MBARI's remotely operated vehicle (ROV) Doc Ricketts offshore of Central California at a depth of approximately 1,660 meters. (MBARI via AP)

This undated photo provided by Monterey Bay Aquarium and Research Institute, shows a mystery mollusk (Bathydevius caudactylus) observed by MBARI's remotely operated vehicle (ROV) Doc Ricketts in the outer Monterey Canyon at a depth of approximately 1,810 meters. (MBARI via AP)

This undated photograph, provided by Monterey Bay Aquarium and Research Institute, shows a mystery mollusc (Bathydevius caudactylus), observed by MBARI's remotely operated vehicle (ROV). (MBARI via AP)