A new staurosporine analog, 4′-N-demethyl-11-hydroxystaurosporine (1), has been isolated by cytotoxicity-guided fractionation of an organic extract of the prosobranch molluskCoriocella nigra. The known staurosporine derivative 3,11-dihydroxystaurosporine (2) was also isolated from this extract. Concurrent investigations ofCoriocella hibyaeresulted in the isolation of two known compounds, lamellarins C (3) and U (4). The structures of1, 2, 3 and 4were elucidated by spectroscopic methods and the compounds were evaluated for cytotoxicity against 10 human tumor cell lines. Compounds1and2demonstrated potent cytotoxic activity with IC50's ranging from approximately 2 to 66 ng/mL.