THE AERIAL ALGÆ OF ICliLAND 413 



IX. Epithemieæ. 



Epithemia Bréb. 



Epithemia Argus Kiitz. Meistcr 1912, p. 198, Taf. 34, lig 3—4. 

 E. Icel. 28 - W. Icel. 338. 

 Hardly an aerial species. 



Epithemia Zebra (Elwb.) Kutz. Van Heurck Traité, p. 296, PI. 9, 

 fig. 357. 



E. Icel. 41, 112, 129 - N. Icel. 162, 169, 252 — S. Icel. L. 294. 



In Iceland the species is extremely common in fresh water (Østrup 

 264 samplesl Only in one of the above-mentioned samples, from the 

 wall of a house with water trickling down it in rainy weather did I 

 find specimens with cell contents, Several of the other localities (41, 169 

 were very damp. Hence it is hardly probable that the species withstands 

 desiccation well. 



Rhopalodia O. Muller. 



Rhopalodia gibba (Kiitz.) O. M. Meister 1912, p. 200, Taf 35, lig. 6. 

 E. Icel. 24 - N. Icel. L. 169, 179 — W. Icel. 336. 



This species is quite predominantly hydrophilous (Østrup 216 

 samjiles), and the specimens found are perhaps for the most i)art erratic. 

 except in sample 169, originaling from the damp bank of a pool near 

 Ljosavatn. 



Rhopalodia gibberula (Ehrb.) O. M. Epithemia g. V.H. Traité, p. 297, 

 PI. 30, fig. 825. 



E. Icel. 24, L. 25, L. 28, 40, 77, 113, L. 124 — N. Icel. 256 - W. Icel. 

 L. 297, 321. 336, L. 337 — S. Icel. 295, 372. 



Only in rather damp localities did I find specimens of this species 

 which contained chromatophores, viz. among mosses in rocky clefts and 

 beside a hot spring (Helgavatn). In the other samples there occurred a 

 grealer or less number of empty frustulcs of the s[)ecies, but from tiiis 

 nothing can be inferred with certainty as to its occurrence in Ihe said 

 localities. It probably has its greatest distribution in fresh water (Østrup 

 69 samples), but owing to its comparatively solid valves it will often 

 occur in a subfossil state. It is known from olden times as a species 

 that will thrive among niosses, on damp rocks and in similar piaces 

 (De Toni). 



Rhopalodia parallela O. M. var. minor Meister. Meister 1912, p. 202, 

 Taf. 35, lig. 10. 



E. Icel. 85, 92? 



Found on a rocky wall witli dripjjing water in Fljolsdalur. It is 

 hardly an aérial species. 



