ddnted, eonve.\o-l rnncate ; cell-wall finely and densely 

 loiigil ndinally plicate-striate. 



Zygospore unknown. 



Length 210-200 /A; breadth 20-:>5 /x (///VA/rr). 



Length 175 /x ; breadth 14 /x, (Ijinnlcll}. 



SCOTLAND. Poolewe, Ross; ('ambus O'May, Aber- 

 deen; Bishop's Dam and Dalbrake in Strachan, Kin- 

 cardine; near Kingshouse, Argyll (J.toi/ mnl Hiwll}. 



\ UK!, AND. Grlengariff, Kerry (Archer}. 



(it'oi/i-. Distribution. Germany. Sweden. Poland. 



Wo have never seen tins species from any part of the 

 world. It apparently differs from _D. uiululuktiiit, J>ail. in 

 being of stouter build, with less dilated apices, and in the 

 structure of the cell-wall. We give llichters and LiiiideM's 

 measurements separately, as there is considerable discrepancy 

 between them. The figures we give (1*1. XXVII, iigs. Jo-15) 

 are careful copies of lliehter's figures in ' lledwigia.' These 

 figures, according to Richter's stated magnification, measure 

 >30-o5o (JL in length and 30-33 /.< in breadth. 



Genus 11. PLEUROT^ENIUM Nag. 184'.). 



Nag. Gatt. uinz. A1-. IS 19, p. 101-. 



liabenh. Flor. Eurup. Algtir. Ill, 1868, p. 1 iU. 



Kirclm. Alg. Schles. 1878, p. 1 1-i. 



M.-uisg. Proilr. Algenfl. Biilnu. 1888, p. 189. 



De Toni, Syll. Alg. 1889, p. 895. 



Cells straight, elongated and cylindrical, viewed 

 from the end circular, slightly constricted in the 

 middle, with a prominent and usually projecting 

 suture ; semicells commonly with an inflated base, 

 which is never plicate, lateral margins straight, undu- 

 late, or nodulose; apices truncate or truncately rounded, 

 frequently plicated round the periphery or furnished 

 with a ring of tubercles ; cell-wall rarely smooth, 

 commonly punctate or minutely scrobiculate, some- 

 times granulose or papillate. Chloroplasts parietal, 

 numerous, arranged in irregular longitudinal bands 

 which are frequently broken up into small rhomboidal 

 or lanceolate masses, each with a single pyrenoid. 



