No. 3] REMARKS ON NORTHERN LITHOTHAMNIA. 27 



Frond spherical or irregular, the crust rather feeble or finally 

 disappearing (being attacked by animals), the lobes small and the 

 branches frequently delicate, short, approximate, often with wart- 

 like processes, or forming bundles rather approximate and sub- 

 fastigiate. 



f. subsimplex Fosl. mscr. 



The crust rather feeble or often vigorous, not or indistinctly 

 lobed, with branches simple or subsimple, frequently conical or 

 subcylindrical, erect. 



Syn : Lithothamnion calcareum Kleen, Nordl. Alg. (1874), p. 11; Kjellm. 

 Vinteralg. (1875), p. 64. 



Lithothamnion fasciculatum Dickie, Alg. Sutherl. I, (1852), p. 142? Aresch. 

 Obs. Phyc. 3 (1875) p. 5, partim! Kjellm. Spetsb. Thall. I (1875), p. 3! Algveg. 

 Murm. Meer. (1877), p. 7; Gobi, Algenfl. Weiss. Meer. (1878), p. 22! 



Lithothamnion glaciale Strom f. Algv. Isl. (1886), p. 18; Fosl. Contrib. I 

 (1890), p. 7; Rosenv. Gronl. Havalg. (1893), p. 7 73! Fosl. Norw. Lithoth. (1895), 

 p. 13 (excl. f. torosa); Rosenv. Deux. Mem. Alg. Mar. Gronl. (1898), p. 9! Fosl. 

 Rev. Syst. Surv. Melob. (1900), p. i 1 ; Saund. Alg. Harr. Alaska Exp. (1901), p. 

 442? Batt. Cat. Brit. Alg. (1902), p. 97! Jonss. Mar. Alg. Icel. I (1901), p. 153! 

 Borg. Mar. Alg. Faroes (1902), p. 400! Setch. Alg. Northw. Amer. (1903), p. 358? 

 Jonss. Mar. Alg. Jan Mayen (1904), p. 305! De Toni, Syll. Alg. (1905), p. 1730 

 (excl. f. flabellata). 



Lithothamnion colliculosum Fosl. Contrib. II (1891), p. 8, partim, Norw. Lithoth. 

 {1895), p. 75, partim, in Rosenv. Deux. Mem. Alg. Mar. Gronl. (1898), p. 11. 



Lithothamnion varians Fosl. Norw. Lithoth. (1895), p. 8, partim, in Rosenv. 

 Deux. Mem. Alg. Mar. Gronl. (1898), p. 11. 



Lithothamnion Ungeri f. intermedia Heydr. Mus. Lithoth. Paris. (1900), p. 540! 



Lithothamnion boreale Fosl. Contrib. II (1891), p. 2, t. 1, partim, Norw. Lithoth. 

 {1895), p. 12, partim; De Toni, Syll. Alg. IV (1905), p. 1731, partim. 1 ) 



a ) There is known only a solitary specimen of Lithoth. boreale, which is 

 figured 1. c. I now think this specimen likely to represent a coarse form 

 of Lithoth. glaciale, covered with Phymatolithon investiens except a 

 small portion ot the basal parts. The branches are rather elongated, but 

 this has probably taken place during the encompassing of the alga, and 

 the uppermost part of the branches seems to have been thoroughly formed 

 by Ph. investiens. It is difficult to fix the limit between both species, as 

 Ph. investiens clings closely to L. glaciale. Cp. below under the species 

 first-named. Also in a section the limit is often hardl} r discoverable, as a 

 new crust over older ones of Ij. glaciale is sometimes scarcely distinguish- 

 able from a closely covering crust of Ph. investiens. Also the. cells, parti- 

 cularly the hypothallic ones, are often much resembling each other. 



