140 BRITISH DESMIDIACE.E. 



f . 2-4 ; Cooke, Brit. Desm. 1886, p. 85, t. 37, f . 1 ; Hansg. Prodr. Algenfl . 



Bohm. 1888, p. 198; De Toni, Syll. Alg. 1889, p. 970; West, Alg. W. 



Ireland, 1892, p. 14-i ; Alg. Eng. Lake Distr. 1892, p. 724 ; Roy & Biss. 



Scott. Desm. 1894, p. 170 ; Nordst. Index Desm. ]896,p. 193; West & 



G. S. West, Alg. S. England, 1897, p. 485 ; Alga-n. Yorks. 1900, p. 69. 

 C. pachydermum a. typicum Klebs, Desni. Ostprenss. 1879, p. 34, t. 3, f. 36. 

 Ursinella pachyderma Kimtze, Revis. gen. plant. 1891, p. 925. 



Cells large, broadly elliptic, about 1J times as long 

 as broad, deeply constricted, sinus narrowly linear 

 with a dilated apex ; semicells widely semi-elliptic, 

 apices broad, basal angles broadly rounded, lower part 

 of sides at first somewhat straight. Side view of 

 semicell subcircular. Vertical view elliptic, ratio of 

 axes about 1 : 1'5. Cell- wall thick and densely punc- 

 tate. Chloroplasts axile, each with two pyrenoids. 



Zygospore unknown. 



Length 78-117 ^; breadth (50-87 ^', breadth of 

 isthmus 30-40 p,-, thickness 50-59 /x; thickness of 

 cell- wall 2 '5-3 JJL. 



EXGLAXD.- -Foot of Brant Fell, Westmoreland ! 

 Malham Tarn and Penygheiit, \V. Yorks ! Pilmoor 

 near Thirsk, X. Yorks ! Mitcham Common and near 

 Chapel Wood, Surrey! Millford Lake, Hants (Ron). 

 Xear Bovey Tracey, Devon (Bennett). Tremethick 

 Moor, Cornwall ! 



SCOTLAND.- -Sutherland, Ross, Aberdeen, Kincardine, 

 Stirling, Argyll (in Mull) (Rot/ $ Bissett). 



IRELAND. - -Lough Aunierin, G-alway ! Dublin and 

 \Yicklow (Archer). Clough, Antrim ! 



Geoc/r. Distribution.- -France. Germany. Austria 

 and Gralicia. Hungary. Italy. Xorway. Sweden. 

 Denmark. Bornholm. Finland. N. and S. Russia. 

 Faeroes. Japan. Sumatra. Java. New Zealand. 

 Australia. Azores. United States. Brazil. Argen- 

 tina. Patagonia. 



C. pachydermum is rendily distinguished from C. Lundetlii 

 by its inflated semicells and its thick cell-wall. The vertical 

 view is also more elliptic. 



Var. sethiopicum nob. (PI. LVII, figs. 8, 9.) 



C. Lundellii var. athiopicum West & Ci. S. West, Welw. Afric. Freshw. 

 Alg. 1897, p. 32 ; Scott. Freshw. Plankton, I, 1903, p. 526, 541. 



