890 NEW OR CRITICAL BRITISH MARINE ALG^. Oallithamnion spar sum preserved in the Hookeriau Herbarium. In habit they resemble either Acrochmtia or Uhodochor tones, but, as I was fortunate enough to find on the first fragment I examined a few axillary monospores, I am satisfied that the plant should be referred to the genus Acrochmtium [Chantransid) . The Rhodochorton sparsum of my List of Berwick Algce, although it is, I believe, the plant usually so called by British authors, is very different from C. sparsum Carm., and appears to be distinct from any described form of Rhodochorton. It is closely related to R. Rothii Nag., but can at once be distinguished from that species by its parasitic habit and scattered mode of growth, not to mention the difference in habitat of the two species, R. Rothii growing only on rocks and near high- water mark, while R. parasiticum is always parasitic on the stems of Laminaria hyperhorea at extreme low-water mark and beyond. I have seen no authentic specimen of Kjellman's R. sparsum, but most probably it is identical with the plant described above. 16. LiTHOTHAMNioN INCRUSTANS FosHe, " Norwegian forms of Lithothamnia (Det. Kgl. Norske Videnskabers Selskabs Skrifter, 1894, 94, pi. 18). Chapman's Pool, Dorset, and Cumbrae, E. A. B. f. Harvetji Foslie, I. c, pi. 18, figs. 12-15. Cumbrae, E. A. B. 17. LiTHOTHAMNioN SoNDERi Hauck, MeevesaJcf. 273, pi. 3. Cum- brae, E.A. B, Isle of Man, R. Harvey Gibson. 18. LiTHOTHAMNioN ORBICULATUM FosHe, I. C. 143, t. 22, figS. 10-11. Arran, E. A. B. Sea, Mill, E. M. Holmes. 19. LiTHOTHAMNioN FLABELLATUM Eosenv. Gvonl. Havalg. 772, figs. 1-2. f. Rosenvingii Foslie, I. c. 70. Isle of Man, R. Harvey Gibson. f. Granii Foslie, I. c. 70, tab. 17, figs. 1-7 et 22. Port Banna- tyne, Bute, D. Robertson. 20. LiTHOTHAMNioN Stromfeltii FosHc, I. c. 145. Bognor, E.A.B. Plymouth, G. Brebner S E. A. B. 21. LiTHOTHAMNioN Lenormandi (Aresch.) f. sublcBvis Foslie I. c. 151. Berwick, jE;. J. 5. 22. LiTHOTHAMNioN Battersii FosHe, New or Critical Litho- thamnia, 1, figs. 1-5. Cumbrae, E.A.B. 23. LiTHOTHAMNioN coRALLioiDES Cm. Fl. Finist. 152, t. 20. f. australis Foslie, Norw. Lith. I. c. 62, tab. 16, figs. 24-31. Cumbrae, E.A.B. i. flabelligera Foslie, I.e. 62, tab. 16, figs. 32-87. Cumbrae, E.A.B. Port Bannatyne, Bute, D. Robertson.
