Reexamination of the configuration of sarcotins A-C, first isolated from the marine sponge Sarcotragus sp., revealed that the proposed stereochemistry of the tetronic acid moiety needs to be revised as shown in 1-3. Additional new pyrrolosesterterpenes (5-11), furanosesterpene derivatives (4, 12-14, 19), and furanoterpenoids, including two trinorsesterterpenes (15, 16) and two diterpenes (17, 18), were isolated from the same sponge by bioactivity-guided fractionation. The planar structures were established on the basis of NMR and MS analysis. The stereochemistry was defined by combined use of NMR, CD spectroscopy, and chemical degradation. The compounds were evaluated for cytotoxicity against five human tumor cell lines and were found to exhibit moderate to significant activity.