STAURASTRUM. 97 



usually horizontal, sometimes slightly converging. Ver- 

 tical view usually triangular, sometimes quadrangular ; 

 sides straight or rarely slightly concave, angles produced 

 to form long processes, lateral margins often with a 

 series of minute granulations, sometimes paired, just 

 within the margin. Chloroplast axile, with a central 

 pyrenoid in each semicell. 



Zygospore spherical, provided with numerous spines, 

 broad at the base, and once or twice divided at the 

 apex. 



Length 27-60 y. ; breadth, including processes, 44- 

 110 IJL ; breadth of isthmus o'o-lSpi; diam. zygosp., 

 without processes, 32 jx ; with processes, 60 (JL. 



ENGLAND. Cumberland, and in the plankton of 

 Buttermere ! Westmoreland ! Lancashire ! (Rolfs). W., 

 N., and E. Yorks., and in the plankton of Gormire, N. 

 Yorks ! Leicestershire (Roy). Essex ! Burnham Beeches, 

 Bucks ! Oxford ! Surrey (zygospores from Thursley 

 Common) ! Hants ! (Roy). Devon ! (Harris). Cornwall ! 



WALES. Fairly general (at 2200 feet on Glyder 

 Each) ! In the plankton ! 



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

 deen, Kincardine, Forfar, Perth !, Argyle and Fife (Roy 

 & Biss.). Cumbrae, Ayr ! Near Lochmaddy, N. Uist, 

 and in Lewis and Harris, Outer Hebrides ! Orkneys and 

 Shetlands, also in the plankton ! More or less general 

 in the plankton ! 



IRELAND. --Donegal ! Mayo and Clare Isle, and in the 

 plankton of Mayo ! Galway and in the plankton ! 

 Kerry and in the plankton ! Dublin and Wicklow 

 (Arch.). Plankton of Lough Neagh ! Londonderry ! 



Geogr. Distribution.- -Fiance. Germany. Switzerland. 

 Galicia and Austria. Hungary. Roumania. Italy. 

 Norway. Finmark. Sweden. Denmark. Bornholm. 

 Finland. Poland. N. Eussia. Caucasus. Greenland. 

 Siberia. Mongolia. Central China (var.). Japan. Turkey 

 in Asia. Ceylon. Australia. Madagascar (var.). E., 

 Central, and S. Africa. United States. Canada. Brazil. 

 Paraguay. 



VOL. v. 7 



