Dolphin ridge is in North Atlantic Ocean while Challenge ridge is in South Atlantic Ocean. Cocos ridge is in Pacific Ocean. South East Indian ridge is in Indian Ocean.
a-supposed-map-of-the-location-of-atlantis-from-a-bit-of-atlantis-by-d-erskine-pen-name-of-john-stuart-buchan-1852-1927-published-1900-dolphins-ridge-is-now-termed-the-mid-atlantic-ridge-2G0R9FH