EUASTKHM. 



Vertical view elliptic, with a spine at each pole, and a 

 granulate or emarginate protuberance at the middle on 

 each side. 



Zygospore unknown. 



Length 3(3-45 p.; breadth 31-36 //,; breadth of 

 isthmus 6-7 p; thickness 16-19 /x. 



SCOTLAND. G-len Coe, Argyll (Roy and Bissett). Loch 



O / \ e / 



Iron Sineur, Perth! (J. Murray). Rhiconich, Suther- 

 land ! 



Geogr. Distribution. Austria and G-alicia. Norway. 

 Sweden. Denmark. Poland. N. Russia. India (var.). 

 United States. West Indies and Brazil (var.). 



This is a very rare species in the British Islands and has 

 essentially a western distribution. 



27. Euastrum dubium Nag. 

 (PI. XXXVIII, figs. 5-8.) 



Euastrum binale Ralfs, Brit. Desm. 1848, t. 14, f . 7 d. 



E. dubium Nag. Gatt. eing. Alg. 1849, p. 122, t. 7 D, f. 2 ; Nordst. Index 



Desm. 1896, p. 113. 

 E. lobulatum Breb. Liste Desm. 1856, p. 124, t. 1, f . 4 ; West & G. S. West 



Alg. Notes II, 1900, p. 290 ; Alga-fl. Yorks. 1900, p. 63 ; Alg. N. Ireland, 



1902, p. 29. 

 E. elegans (Breb.) Kiitz. var. lobulatum (Breb.) Jacobs. Desm. Danein. 



1875, p. 191. 

 E. binale (Tiirp.) Elirenb. var. rotundata Istvanffi, Diag. prsev. Alg. nov. 



Hungar. 1887, p. 236 (according to Istvanffi). 

 E. erosum Lund. var. notabile West, Alg. Eng. Lake Distr. 1892, p. 723, 



t. 9, f. 17 ; West & G. S. West, Alg. S. England, 1897, p. 484. 



Cells very small, 1^- times longer than broad, very 

 deeply constricted, sinus narrowly linear witli a slightly- 

 dilated extremity ; semicells truncato-pyramidate, five- 

 lolled ; polar lobe short, oblong-rectangular, apex trun- 

 cate with a narrow median incision, apical angles 

 furnished with a small conical granule ; upper lateral 

 lobes rounded ; lower lateral lobes very slightly larger 

 than the upper ones, rounded, obliquely truncate, or 

 sometimes slightly emarginate ; semicells with two 

 granules within the apex, one on each side of the 

 notch, with two faint granules within each basal angle, 

 often with a faint granule below the apical notch, and 

 with a slight trace of a smooth central protuberance. 



