124 BRITISH DESMTDTACE.E. 



IRELAND. Mayo ! Galway ! Kerry ! Donegal ! 

 Dublin and Wicklow (Archer). Londonderry ! Down ! 

 Antrim ! 



(friHjr. Distribution. Generally distributed in Europe. 

 Kaeroes. Greenland. Spitzbergen. Nova Zembla. 

 India. Ceylon. Burmah. Singapore. Java. Central 

 China. Japan. New Zealand. East Africa. United 

 States. Brazil. 



Considering the wide distribution of this species it exhibits 

 little variation. Specimens from different localities may vary 

 in their comparative length and breadth and also in the relative 

 breadth of the apices. Sometimes the apices are a little 

 inflated, but this is not a common feature. The striolations 

 vary from 13 to 17 in 20 /t. In many of the mountain forms 

 the cell-wall is almost colourless. The curvature is some- 

 what variable but is never very great. In some forms the 

 central portion of the cell is straight and the apices are con- 

 siderably curved, but considering the large number of inter- 

 mediate states the name " var. orthonotum," given to this 

 form by Roy, is not warranted. 



The striolations are not very strong and towards the 

 extremities they become reduced in number, a character 

 found in many striolated Closteria. This is brought about 

 either by the gradual fading out of a few of the striolations 

 or the fusion of some of them before they reach the apex. 

 The cell-wall between the striolations is often minutely 

 punctulate. 



Forma recta West. (PI. XIII, fig. 17.) 



Closterium striolatum forma recta West, Alg. N. Wales, 1890, p. 285, 

 t. 5, f. 23. 



Cells straight and symmetrical around a longitudinal 

 axis. 



Length 216 /A ; breadth 33 p. 



WALES. Llyn Padarn, Carnarvonshire ! 



Lagerheim has suggested (Nuova Notarisia, II, p. 30) that 

 this form is a species of Penium, but this is not so. Except 

 for its straightness it is a typical CL striolatum. 



