40 BRITISH DESMIDIAOE7K. 



Zygospore unknown. 



Length 12-21 / ; breadth 6-7'4 /i. 



ENGLAND. Shipley Glen, W. Yorks ! 



WALES. Capel Curig (Roy). 



SCOTLAND. Braes of Gight, Scotston Moor, Dalbagie, 

 Aberdeen; Muchalls, Kincardine (lt<>i/ ' Bissetl). 



IRELAND. Dublin and Wicklow (Archer). 



Geogr. Distribution. France. Germany. Switzer- 

 land. Hungary. Sweden. Faeroes. United States. 



This is distinguished from the preceding species by its 

 larger size and cylindrical cells. The chloroplast is also 

 relatively broader. 



1. Spirotsenia truncata Arch. 

 (PI. II, figs. 24-20.) 



Spirottenia truncata Arch, in Proc. Dubl. Nat. Hist. Soc. 1862, p. S3, t. 2, 

 f. L'S 31; in Micr. Journ. 1802, p. 253, t. 12; Conj. Spirotsen. 1867, 

 p. 191, t. 8, f. 12; Kabenh. Flor. Europ. Alg-ar. Ill, 18(58, p. 147; 

 Cooke, Brit. Desm. 1886, p. 51, t. 19, f. 4 ; Nordst. Index Desiuid. 1896, 

 p. 261. 



Cells small, cylindrical, 5-8 times longer than their 

 diameter, attenuated near the apices which are trun- 

 cate ; chloroplast with two to six rather close revolu- 

 tions leaving a minute clear space at the poles ; this 

 clear space or apical vacuole sometimes contains one 

 or more moving granules. 



Zygospore globose, closely covered with large, 

 acutely-conical teeth. 



Length 50 n ; breadth 7 /u; diam. zygospore without 

 spines 18 /u, with spines 30-35 /u. 



ENGLAND. Angle Tarn, Cumberland ! 



WALES. Capel Curig, Carnarvonshire ! 



SCOTLAND. Inverness (Skye), Aberdeen, Kincardine, 

 Forfar, Perth, Argyle (It<>// g Bissett). 



IRELAND. Dublin and Wicklow (Archer). Mourne 

 Mts., Down ! Zygospores from Glencar, Kerry, and 

 from Westmeath (Archer}. 



Geoi/r. Distribution. Denmark. Sweden. Nova 

 Zembla. India (var.). 



