228 BRITISH DESMIDIACE.E. 



row of o vertically elongated granules. Side view of 



I/ 



semicell subcircular. Vertical view elliptic or sub- 

 rhomboid-elliptic, margins granulate, the 3 granules 

 at the middle on each side more prominent than the 

 others. Chloroplasts axile, with a central pyrenoid. 



Zygospore unknown. 



Length 25ft; breadth 19 ju ; breadth of isthmus o//. 



(reogr. Distribution.- -Q&licia, in Austria. 



The typical form of this species has not been observed from 

 the British Islands. 



Var. tristriatum (Liitkem.) Schmidle. (PI. LXXXVI. 



figs. 8, 9.) 



Cosmarium Blyttii Wille forma tristriatum Liitkem. Desm. Attersees, 



1893, p. 553, t. 8, f. 5 ; Desm. Millstattersees, 1900, p. 66. 

 C. sexnotatum Gutw. var. tristriatum (Liitkem.) Schmidle, Beitr. alp. Alg. 

 1895, p. 458. 



Semicells pyramidate-trapeziform, with a truncate 

 apex, straight or slightly undulate ; one or all of the 

 3 elongated central granules divided into two parts, 

 generally into a larger and a smaller portion. 



Length 16-26/x,; breadth 14-22 /x; breadth of isth- 

 mus 4-8 p. ; thickness 9-14' 5 /x. 



WALES. G-lyder Fach, Carnarvonshire ! 



SCOTLAND.- -Khiconich, Sutherland ! Harris, Outer 

 Hebrides ! 



IRELAND.- -Lough G-artan, Donegal ! Near Oughter- 

 ard, Gal way ! 



Geogr. Distribution.- -Austria,. Sweden. Roumania. 



This variety exhibits considerable variation in size and in 

 the details of the central granules. Its chief distinction from 

 typical C. sexnotatum is in the pyramidate form of the semi- 

 cells. 



200. Cosmarium subcrenatum Hantzsch. 

 (PL LXXXVI, figs. 10-14.) 



Cosmarium subcrenatum Hantzsch in Kabenli. Alg. 1861, no. 1213; Babenh. 

 Flor. Europ. Alg. Ill, 1868, p. 164 ; Nordst, Desm. Arctose, 1875, p. 21, 

 t. 6, f . 10-11 ; Desm. Ital. 1876, p. 35 ; Wille, Ferskv. Alg. Nov. Semlj. 

 1879, p. 40 ; ? Wolle, Desm. U. S. 1884, p. 84, t. 18, f . 6-7, t. 19, f . 20 ; 

 Boldt, Siber. Chlorophy. 1885, p. 106; Hansg. Prodr. Algenfl. Bohm. 

 1888, p. 201 ; Boldt, Desm. Gronland, 1888, p. 18 ; Nordst. Bornh. Desm. 



