Our previous chemical investigations of a yellow marine alga from Puerto Rico, tentatively identified as the tuft-forming cyanobacterium Hormothamnion enteromorphoides, led to the isolation of a structurally novel cytotoxic styrylchromone natural product, hormothamnione [2]. Continued chemical work with this organism has resulted in the isolation and spectroscopic structure elucidation of a closely related styrylchromone, 6-desmethoxyhormothamnione [1], which is also cytotoxic to cancer cells. The substitution pattern of proton, hydroxyl, and methoxyl groups on the chromone ring was established by long range 1H-13C heteronuclear correlation spectroscopy. The taxonomy of the source organism for these styrylchromone natural products, 1 and 2, is revised to the marine cryptophyte Chrysophaeum taylori as a result of detailed microscopic and cultural efforts.