NEW OR CRITICAL BRITISH MARINE ALG^. 385 6-5 /A in diameter. Articulations nearly square or slightly longer than broad ; colour a dark purple-red. On an old shell dredged at the mouth of the Yealm, G. Brehner. This variety differs from the typical form in the slightly greater thickness of the trichomes, which are of a deep, clear, purplish red colour, instead of the light bluish green of ordinary specimens ; the patches are also much smaller, and the filaments are not collected into such evident teeth. 3. MicRocoLEUs TENERRiMUS Gom. Mouog. Oscil. 93. On rocks near high- water mark, Torquay, E.A.B. Easily distinguished from the only other marine species of Microcoleus found on the shores of Britain by the slenderness of the trichomes, which are only 1 to 1-5 />t in diameter and sharply pointed, and by the smaller number of them contained in each sheath. 4. Hyella c^spitosa Bornet et Flahault in Morot Journ. cle Botanique, ii. 162 ; var. nitida, nov. var. Filaments clear purplish carmine, much and irregularly branched, and more slender than in the typical form ; cells varying from square to several times longer than broad, frequently divided longitudinally (chroococcoid fila- ments, however, are rare) ; five, six, or more contiguous cells of the same filament often simultaneously converted into short, simple, forked, or irregularly-branched chains of sporangia. In old shells from deep water, Weymouth, E.A.B.; Malahide, T. Johnson; Plymouth, G. Brehner. The colour of this alga is clear purplish-pink, not unlike that of CoHcJwcelis rosea, with which it is frequently associated, but very unlike that of typical Hyella caspitosa, from which it is also dis- tinguished by many slight differences more easily seen than described. It is by no means improbable that it is really specifically distinct from Hyella ccsspitosa, but I have seen too few specimens at present to be certain that the characters are constant. It is worthy of remark that Oscillatoria rosea, the variety of Symploca atlantica described above, and the present variety, all of them obtained from deep water, where one would not expect to find any Myxophycece, are of the same purplish-red or pink colour, while specimens of the same genera obtained from the shallow water near high-water mark are always bluish green or greyish purple. 5. Ralfsia disciformis Crn. Fiorule du Finist. 166. Dredged from deep water near the mouth of the Yealm, and in Plymouth Sound, G. Brehner. Plymouth specimens agree well with those distributed in Des- mazieres' exsiccata by the brothers Crouan. As a species, however, it must be confessed that the plant comes too near to Ii. clavata, from which it is distinguished by the shorter, less clavate para- physes, which are often composed of but one or two cells, and are then hardly any longer than the sporangia. 6. Lithoderma simulans ( = Sorapion simulans Kuckuck, Bemerk. zur Mar. Alg. Helgoland, 236). " Queen's Ground," Plymouth. I detected this species on some old shells dredged from the Queen's Ground, Plymouth, and sent to me by Mr. Brebner. The species
