174 BRITISH PESMIDIACE^E. 



and E. Yorks ! Bucks ! Oxfordshire ! Warwickshire 

 (Wills). Gloucestershire (Rolfs). Surrey ! Sussex 

 (Balfs). Kent (Rolfs). Hants ! (-Boy). Devon! Corn- 

 wall ! 



WALKS.- -Capel Curig!, Llyn Padarn !, Llyn Idwal!, 

 Llyn Gwynant!, Llyn-y-cwm-ffynon !, near Dolbadarn 

 Castle !, Bettwys-y-coed (Rot/), Pen-y-gwryd (Roy), 

 and Grlyder Fawr (Roy), Carnarvonshire. 



SCOTLAND.- -General : zygospore near Dinnet, Aber- 

 deen (Roy $ Bissett). Sutherland ! Inverness ! Lewis 

 and Benbecula, Outer Hebrides ! Scottish plankton 

 generally ! Plankton of Loch Beosetter in Bressay, 

 Shetlands ! 



IRELAND.- -Donegal ! Mayo (including Achill and 

 Clare Islands) ! Several lakes in Galway ! Several 

 lakes in Kerry (also in plankton) ! Dublin and 

 Wicklow (Archer). Louth ! Down ! Londonderry ! 



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

 and Galicia. Hungary. Roumania. Servia. Mace- 

 donia. Italy. Portugal. Norway. Sweden. Denmark. 

 Central and S. Russia. Greenland. Japan. India. 

 Ceylon. Australia. New Zealand. Madagascar. 

 Central Africa. Azores. United States. Brazil. 

 Bolivia. Paraguay. Argentina. 



Staurastrum dilatatum is most frequent in bogs and at the 

 boggy margins of lakes, and in some of the western areas of 

 the British Islands it is commonly found in association with 

 Cosmarium conspersum var. latum, C. tetraophthalmum, C. 

 reniforme, C. subundulatum, Staurastrum teliferum, and other 

 Desmids. 



Half's' figures are poor and do not give an adequate idea of 

 the characters of the species. We find the semicells somewhat 

 variable in outward form. They may be regularly elliptic- 

 fusiform, but more often there is a more or less distinct 

 ventral inflation. The regularity of the granulation, especi- 

 ally as seen in the vertical view, is one of the principal 

 characters of the species. The angles were described and 

 figured by Ralfs as truncate, in consequence of which De 

 Notaris (1867) founded for the form with rounded angles 

 the var. obtusilobum. This form was admirably figured by 

 Nordstedt in 1888, and since that date has been repeatedly 



