40(i JOHS. BOYE PETKHSKN 



l-'ornis ol P.liitti linve |)rL'\iously hccn l'ouiul uii (Inin]) locks De 

 Toni. V. Schonfcltit. Hiistedt. Dellandre 1926). bul iio »ioiibt the 

 species occiirs most commoiily in fresli water. Ostru|) does nol nien- 

 lion V. Hahciihorslii as occuniiij^ in Iceland. I dnrc nol inIVr from Ihis 

 faet, however, Ihal it was not present in the malerial. l'ossijjly Ostrup 

 niay not liave dislinguished it from tlic main si)ecies, and perhajjs tliere 

 is not suflicient reason to do so. 



Tiie 4 samples from E. Iccl. in whicli I found specimens with cell 

 contenls wcre all derivcd Ironi damp rocks, and prccisely from very 

 nioist parts thai will hardly ever be quite dry even in summer. The 

 sanijjle from S. Iceland originales from turi in the wall of a house, in 

 a place where the water runs down in rainy wcather, lience the most 

 damj) |)lace of the wall. Thus this form will nol. probably. survive much 

 desiccalion. nor does it probably nced much organic nourishment. 



Pinnularia major Kiilz. Cl. Syn II. p. 89. \. S. .Ml. Taf. 42, fig. 8. 

 N. Icel. L. 2 lo. 



The form founil in this sample was somewhat smaller than the ene 

 described by Cleve (i. c). Its dimensions were: L. 109//. br. 2<S /<, 

 sir. 8,2 in 10 /r The sample was taken from very damj) mud from Ihe 

 floor of the ravine »Stora Gja« near .Myvatn. and the species can hardly 

 be an aerial one. 



Pinnularia mesolepta Fhrb. var stauroneiformis Grun. GI. Syn. II. 

 p. 76. Ad. Schm. All. Taf. 45. fig. 53. 



N.Icel. L. 215, L. 217, L. 218 - S. Icel. 372. 



According lo Østrup var. stauroneiformis is the most commonly 

 occurring form of P. mesolepla in Iceland. where he found it in 55 samples. 

 The 3 above-mcnlioned sam|)les from N.Icel. all oiiginale from ».Stora Gja« 

 where il is probably always moist. This form can therefore hardly be 

 reckoned among the true aerial algæ. But few sjjecimens were found in 

 the sample from S. Icel.. and possibly they had not lived on the spot 

 i^ground in Ironi of the house . 



Besides the typical form, another form, shorter, hardly capitate and 

 with straight lateral walls, was found in sani])les 215 and 217. Ils di- 

 monsiiuis were; L. 28 //, br. 11//, sir. 14 in 10/(. This form I have liere 

 includcd wilhin the present variety, since it forms a gradual Iransilion 

 to the typical form by intermediate forms. But it mighl |)erhaps with 

 equal correctness be referred lu P. microstanron. 



Pinnularia molaris Grun. GI. Svn. II. p. 74. .1. Schm. .Ml. Taf. 313, 

 fig. 18. 



E. Iccl. 7. 8. 125 — N. Icel. L. 215, 217. 218 - W. Icel. L. 3U7, 309a, 

 L. 321. L. 336. L. 338 - S. Icel. L. 352. L. 364. 



Ostrup only found Ihc s|)ecies in 3 samples Irom fresh water in 

 Iceland, so according to the data it is probable liial it lives chielly as 

 a terrcslrial species in Ihe island. 1 have found it several times (samples 



