THE AERIAL ALGÆ OF ICELAND 



381 



This exceedingly widespread and common species was found by 

 Østrup in 140 samples from Iceland. In most of the above-mentioned 

 samj)les I bave only seen some few spceimens of it, while it was im- 

 possible to find individuals witb cell contcnts in tbese samples. Conse- 

 ([uently I presume tbat it is a casual giiest in the samples and has not 

 perbaps lived in tbese localitics at all. The samples in which it occurred 

 in fairly large quantities and in which there were individuals with cell 

 contcnts were all derived from piaces with plenty of moisture. I must 

 thus consider the species to be a rather pronounced bydroi)hilous species. 



VI. Naviculeæ. 



Diploneis Ehrb. 



Diploneis oculata Bréb. Cl. Svn. I, j). 92. V. Heurck Syn. PI. 9, 

 fig. 10. 



E. Icel. L. 92 — X. Icel. L. 217. 

 Area : Eur. 



The specimens I have found of this species are somewhat smaller 

 than those generalh- described. viz. 1.13—14//, br. 5,5//, str. 23—27 in 10//. 

 The two localities in which it occurred dilfer wideh', one being a large 

 stone in the ravine »Stora Gjå«, the other the hlaå of a farm. In both 

 piaces there grew Prasiola, in the first place also mosses. In the litera- 

 ture this species is recorded as living in fresh water, especially running 

 water. 



Diploneis minuta Boye P. n. sp. 



Valva lineari, apicibus rotundatis. long. 13//, lat. 4,4 //, 

 striis delicatissimis, vix visibilibus. Fig. 6. 



E. Icel. 7, L. 25. 



In this very small species the strongly silicilied apical 

 »horns« are plainly seen, surrounding the rapbe. The striæ 

 are so fine tbat I have only seen a faint glimpsc of them. 

 Thev are outside the longitudinal furrows. 





Fig. 6. 



Diploneis 



minula 



BoN'eP. n.sp. 

 Found in the same two samples as Xavicnla brijophila n.sp. ("< 1200). 



Diploneis ovalis Hilse. Cl. Syn. I, p. 92. V. Heurck, Syn. PI. 10, 

 fig. 10 b. 



E. Icel. 7, 14, 40, L. 77, 78, 92, L. 112 ~ N. Icel. 1G9 — S. Icel. 

 L? 294, 295. 



There is a gradual transition from D. ovalis typica to var. oblongella. 

 Such transition forms occurred in most of the above-mentioned samples. 

 The species, which seems to be cosmopolitan. was found by Østrup 

 in 49 samples from fresh water. According to the data it would thus 

 seem to be as frequently terrestrial as aquatic. Most of the samples in 

 which I found it were derived from turf walls or the immediate vicinity 

 of houses. 



