A chemical study of the pink encrusting sponge Aplysilla glacialis collected in Barkley Sound, B.C., has led to the isolation and structure elucidation of terpenes which are believed to be derived biogenetically from the hypothetical "spongian" precursor. In addition, the first example of a diterpene from a sponge containing a "marginatane" skeleton has been found. Cadlinolide A (75) was isolated and its structure elucidated by a combination of spectroscopic interpretation, chemical degradation, and confirmed by a single crystal x-ray diffraction analysis. The structure of a related metabolite, cadlinolide B (76). was also isolated and elucidated by spectroscopic interpretation and conversion to the known metabolite tetrahydroaplysulphurin-1 (72). The structure of a nor-diterpene, aplysillolide A (101) was determined by spectroscopic interpretation and chemical interconversion along with its dehydrated analogue, aplysillolide B (102). Glaciolide (110). a degraded and highly rearranged diterpene was solved by extensive NMR analysis of both the parent compound and its chemically interconverted derivatives. Glaciolide (110) represents only the second known example of a metabolite containing a "glaciane" skeleton. Marginatone (112) is the first example of a diterpene containing a "marginatane" skeleton from a sponge. The "marginatane" skeleton was first encountered in a metabolite, marginatafuran (111), isolated from the nudibranch Cadlina luteomarginata which is generally found in the same location as Aplysilla glacialis. The structure of cadlinolide C (131), containing both methyl ester and γ lactone moieties, was elucidated by spectroscopic interpretation. This compound is believed to be an isolation artifact Examination of the chemical constituents of the nudibranch Cadlina luteomarginata found feeding on the sponge Aplysilla glacialis yielded a mixture of terpenes mcluding cadlinolide A (75). glaciolide (110) and tetrahydroaplysulphurin-1 (72). Compound 72 was previously isolated from a New Zealand sponge. A review of "spongian" and "marginatane" derived metabolites from sponges and nudibranchs as well as a review of Cadlina luteomarginata terpenoids is presented. [Formulas omitted] / Science, Faculty of / Chemistry, Department of / Graduate