184 KJELLMAN, THE ALGA OF THE ARCTIC SEA. 
Antithamnion americanum (Hary.) Fart. 
New Engl. Alg. p. 123; Callithamnion americanum Harv. Ner. Am. 2, p. 238. 
Deser. et Fig. Callithamnion americanum Harv. |. ¢. et t. 36 A. 
Syn. Callithamnion americanum Dickte, Alg. Walker. p. 86; Alg. Cumberl. p. 239. 
» » CroaLL, FI. Dise. p. 460. 
Habitat. According to existing statements it appears to occur both as litoral and 
as sublitoral at the places where it has been as yet observed in the Arctic Sea. In 
the former case it is attached to stones, in the latter to alee: Chatomorpha melagonium. 
Geogr. Distrib. It has been reported from the American Arctic Sea and Baffin Bay. 
Localities: The American Arctic Sea: Port Kennedy. 
Baffin Bay: Cumberland Sound, plentiful; the west coast of Greenland at or 
about Disco Island. 
Gen. Rhodochorton Naa. 
Ceram. p. 355. 
Subgen. 1. Thamnidium Txur. 
in Le Jon. Liste Alg. Cherb. p. 110. 
Rhodochorton intermedium KJrLun. 
Spetsb. Thall. 1, p. 28. 
Descr. Thamnidium intermedium KJrtum. 1. e. 
Fig. » » » DY ite te shee al) 
Rhodochorton intermedium tab. nostra 15, fig. 8. 
Habitat. Litoral, growing gregarious on rocks exposed to the surge. Specimens 
gathered in July bear few tetrasporangia. 
Locality: Found as yet only in the Greenland Sea on the west coast of Spitz- 
bergen in the interior of Icebay. 
Rhodochorton spinulosum (Sunr) nob. 
Callithamnion spinulosum Suur, Flora 1840, p. 292. 
Deser. Callithamnion spinulosum J. G. AG. Epicr. p. 12. 
Remark on this species. The present species resembles Ri, Rothi in habit, differing 
from it by the structure and arrangement of those branch-systems which bear tetraspo- 
rangia. With regard to those systems it approaches nearly to Rh. floridulum as deter- 
mined by Thuret and figured by Lr Joris, Liste Alg. Cherb. tab. 6. It differs from it 
in size, habit, ramification, ete. 
Habitat. According to Sunr this plant grows epiphytic on other alge. J. G. 
Acarpu doubts the correctness of this statement, and after having myself examined 
specimens in the herbarium of the Copenhague Museum I cannot but embrace the 
 ——— 
