Samples of Siderastrea collected by the geologist C. F. Hartt during expedition to Brazil (19th century), and deposited at the National Museum of the Natural History, Smithsonian Institution, have been re-examined. Taxonomical analyses resulted in the identification of a colony of S. siderea from offshore northern Bahia state. Following recent studies, the occurrence of Caribbean siderastreids to western South Atlantic provides new criteria to assess intra- and interpopulational morphological variation of the endemic S. stellata, refuting historical trends of synonymizations possibly biased by long-term taxonomical misunderstandings.