226 BRITISH DESMIDIACE.E. 



Cells very small, slightly longer than broad, very 

 deeply constricted, sinus narrowly linear; semicells 

 trapeziform-semicircular, basal angles subrectangular, 

 sides commonly 4-crenate (including the basal and 

 apical angles), with the third crenation from the base 

 usually emarginate and often with a retuse-emarginate 

 basal crenation, apex truncate and 4-crenate (including 

 the two upper lateral crenations), with one or two 

 series of small granules within the marginal crena- 

 tions, and with a subpapillate granule in the centre. 

 Side view of semicell subcircular from a flattened base, 

 with a well-marked granule at the middle on each 

 side. Vertical view elliptic or rather narrowly elliptic, 

 with a prominent granule at the middle on each side. 

 Chloroplasts axile, with one central pyrenoid. 



Zygospore unknown. 



Length 10-19 //, ; breadth 7-16 JJL ; breadth of isthmus 

 2'8 5'5 fj. ; thickness 8-11 p. 



ENGLAND.- -Harrop Tarn, Cumberland ! Helvellyn, 

 Westmoreland, at 2400 ft. (a small form) ! Cockett 

 Moss near Giggles wick, and Cragg Yale towards 

 Blackstone Edge, "W. Yorks ! Mickle and Cronkley 

 Fells, N. Yorks ! Skip with Common, E. Yorks ! 

 Bisley and Thursley Commons, Surrey! Hants (Roy). 



WALES. --Capel Curig, Llyn Padarn, Llyn-y-cwm- 

 ffynon, and Llyn-an-afon, Carnarvonshire ! 



SCOTLAND. - -Sutherland !, Ross, Inverness!, Aber- 

 deen !, Kincardine, Argyll (Mull), Fife (Roy $ 

 Bissetf). Kirkcudbright ! Lewis and Harris, Outer 

 Hebrides ! Orkneys ! 



IRELAND.- -Donegal! Mayo! Gal way ! Kerry! 

 Down ! 



Geogr. Distribution.- -France. Germany. Austria. 

 Galicia in Austria. Norway. Sweden. Bornholm. 

 Greenland. Central China. Ceylon. Siam. Australia 

 (form). New Zealand. Madagascar. Central and 

 E. Africa. United States. 



C. Blyttii is one of the smallest and most characteristic of 

 the rough species of Cosmarium. It has a very wide distri- 



