In addition to acanthellin-1 (1), an isonitrile previously found in Acanthella acuta, five new nitrogenous sesquiterpenes (2-6) have been isolated from the Mediterranean sponge Axinella cannabina and their structures elucidated on the basis of chemical and spectral data. These metabolites form two new isocyanide-isothiocyanate-formamide series thus confirming the biogenetical relationship between these three classes of compounds. The isonitrile 4 was characterized by HRMS, IR, NMR spectra and dehydrogenation to eudalene. Isothiocyanates 2 and 5 were obtained by treating 1 and 4 with sulfur, respectively. Formamides 3 and 6 were synthesized by hydrating 1 and 4, respectively. The isolation from A. cannabina of two formamide-isothiocyanate-isocyanide series supports the argument that these three functionalities are biogenetically related and shows the capability of this marine organism to elaborate a large number of sesquiterpene skeletons.