208 BRITISH DESMIDIACE.K. 



(Roy). Leicestershire(7n>//). Lincolnshire! Norfolk! 

 Middlesex ! Kent ! Surrey ! Devon ! Cornwall ! 



tj 



(Marquand). 



AVAL i:s.- -General in Carnarvonshire and Merioneth ! 



SCOTLAND.- -Rhiconich, Sutherland ! Ross ! Near 

 Dinnet, and pool TV. side of Loch Dawin, Aberdeen ; 

 Glen Gany, Perth ; near St. Andrews, Fife (Roy $* 

 Rititett). Lewis and Harris, Outer Hebrides ! Orkneys ! 

 Shetlands ! 



IRELAND. Donegal ! Mavo ! Galway ! Kerry ! 



O e.' / / 



Tyrone! Wicklow ! (Archer). Armagh! Down! 

 Londonderry ! In the lake-plankton of Galway ! 



Geogr. Distribution. France. Germany. Galicia 

 in Austria. Hungary. Italy. Spain (form). Norway. 

 Sweden. Denmark. Bornholm. Finland. Poland. 

 Russian Lapland. Central and S. Russia. Faeroes. 

 Iceland. Nova Zembla. Spitsbergen. Greenland. 

 Siberia. Mongolia. Central China. Japan. Afghan- 

 istan. India. Ceylon. Singapore. Celebes. New 

 Zealand. Madagascar (var..). E. and Central Africa. 

 Azores. United States. Brazil. Paraguay. Pata- 



fc> 



C. punctulatum has a wide distribution in the British 

 Islands, occurring most abundantly in peaty pools and ditches, 

 especially among submerged Sphagnum. The semicells have 

 a characteristic trapeziform shape, with rounded angles. 

 The granulation is fine, and the granules are of a uniform 

 size, and near the centre of the semicells there is very fre- 

 quently a clear space of indefinite extent, around which the 

 granules are often much reduced. The apex of the semicell 

 is granulate although the granules may be somewhat reduced. 

 Thus, even the most typical specimens of C. punctulatum 

 commonly show a slight differentiation in the granulation, 

 due mostly to the indefinite clear area in the centre of the 

 semicells causing a separation of certain granules above the 

 isthmus from the remainder of the cell-granules. 



Other forms of C. punctulatum in which there is a much 

 clearer differentiation in the granulation are quite frequent. 

 These forms possess certain strongly developed central 

 granules, larger than the others, and generally surrounded 

 by a clear space. The number of central granules is very 



