A series of pirardixanthin derivatives, 1, 2, 3, 4, and 5, possessing the 5,6-dihydro-beta-end group were isolated from the spindle shell Fusinus perplexus.(1,2) Their structures and absolute configurations were determined by modern spectroscopic analysis to be (4S,5S,6S,4'S,5'S,6'S)-5,6,5',6'-tetrahydro-beta,beta-carotene-4,4'-diol (1), (3S,4R,5S,6S,4'S,5'S,6'S)-5,6,5',6'-tetrahydro-beta,beta-carotene-3,4,4'-triol (2), (3S,4R,5S,6S,3'S,4'R,5'S,6'S)-5,6,5',6'-tetrahydro-beta,beta-carotene-3,4,3',4'-tetrol (3), (5S,6S,4'S,5'S,6'S)-4'-hydroxy-5,6,5',6'-tetrahydro-beta,beta-caroten-4-one (4), and (4'S,5'S,6'S)-4'-hydroxy-5',6'-dihydro-beta,beta-caroten-4-one (5).