In the search for new structures to assist the development of conformational analysis, water-soluble polysarcharides have been extracted from the title algae and where possible separated into 3,6-anhydrogalactose-rich and 3,6-anhydrogalactose-poor components, i.e. into χ and λ-fractions. The sixteen polysaccharides were investigated by (i) direct analysis, (ii) measurement of the sulphate elimination to form extra 3,6-anhydrogalactose residues, and (iii) determination of the proportion of the structure that is composed of alternately arranged galactose and 3,6-anhydrogalactose residues, before as well as after the sulphate elimination. The results were consistent with existing concepts of the structural chemistry of these polysaccharides but several new forms are noted that may be valuable for conformational studies, including an agarose sulphate and several possible new variants of λ-carrageenan.