THE AERIAL ALGÆ: OF ICELAND 



379 



found, intcr alia. in puddlcs. In Iceland I have found it in similar loca- 

 lities, viz. among mosses in a mountain cleft in E. Iceland, and in the 

 partly desiccatcd river bed of Glji'ifiirholtsa among Vamheria. The species 

 will no doubt often be found among the »formations passagércs«. 



Achnanthes minutissima Kiitz. var. cryptocephala Grun. Cl. Syn. II, 

 p. 188. V. Heurck Syn. PI. 27, lig. 41-44. 



E. Icel. 8. - N. Icel. L. 219. 



This form was found in 27 samples by Østrup, so it must be 

 supposed that in Iceland it is chiefly aquatic. In sample 219 I found 

 it in (juantity among mosses on a bridle-path. 



Achnanthes subsalsa Boye Petersen n. sp. 

 Vcstmannaej'jar L. 399. 



Valva late lanceolata, long. 14,3,«, lat. 7,3//, striis 

 23 in 10 u per totam valvam radiantibus. Epitheca 

 area apicali angusta; arca hypothecæ in media parte 

 ovali, ceterum angusta. Fig. 4. 



Found only among Vaucheria and Rhizocloniuin in 

 a mountain cave on Heimacy at a hcight of abt. 20 m. 

 Most nearlj' related {o A. delicatiila Kiitz. but tincr-striated. the striæ are 

 radial on both valves, and the valve is comparatively broader. 



Fig. 4. Achndtithcs 



subsalsa Boye P. 



11. sp. (X 1200). 



Heteroneis Cl. 



Achnanthes marginulata Grun. Cl. Syn. II, 184. V. Heurck Syn. 

 PI. 27, Og. 45, 46. 



E. Icel. 8, L. 123, L. 124, L. 125, 128, 129, - N. Icel. 160, 169?, 

 L. 254 — N. W. Icel. 264 - W. Icel. 336. 



Area: Norway (Dovre), Russ. Lapl., Arct. Amer., Grl., Jan Mayen. 



An alpine-boreal species, only known to live in Iceland on the 

 ground and on rocks, mostly among mosses or Vaucheria, but also oc- 

 curring on the naked ground, c. g. by the roadsidc. However, I have 

 ascertained that it may also occur in running water, tims in samples 

 from Jan JJayen (Boye Petersen 1924 III, p. 18). Hustedt likewise found 

 it in water (1922 I, p. 98, 100). In this species the frustule is slightly 

 silicified. hcnce it shows itseif very hyaline in styrax preparations and 

 has no doubt often passed unnoticed. In air prejjaralions the striation 

 appears distinclly, inter alia the short marginal striæ on the epitheca. 

 By thesc characters it is distinguished from the otherwise very similar 

 A.kryophila Boye P. a924 II, p. 316). 



Achnanthes pyqmæa (Schum.) Cl. Cl. Syn. II, j). 184. Schumann, 

 Preuss. Diat. I Nachtr. p. 19, Taf. II, tig. 11. Fig. nostr. 5. 



X. \Y. Icel. L. 268. 



The species was first found by Schumann in the Baltic, and judging 

 from his remark, »truppweise in Schleimmassen auftretend«, he must 



