X. \XTHIDIUM. G5 



middle on each side, and with a pair of slightly 

 divergent spines on each polar margin. Cell-wall 

 finely punctate. Chloroplasts generally parietal, four 

 in each semicell, each with one, or more rarely with 

 two, pyrenoids ; sometimes irregular, and not infre- 

 quently wholly axile. 



Zygospore globose, furnished with long, slender 

 spines, slightly widened at the base, and shortly 

 bifurcate at the apex. 



Length without spines 42-76 jn, with spines o4- 

 114 /x; breadth without spines 42-72 //,, with spines 

 5 7-108 ju; breadth of isthmus 14*5-26 p. ; thickness 

 2137 /^; diam. zygosp. without spines 45-58 ju,, with 

 spines 80-98 //,. 



EXGLAXD.- -Cumberland ! Westmoreland ! (Ralfs). 

 Lancashire! (Ralfs). W. and ]SF. Yorks ! Cheshire 

 (Rolfs). Essex! Buckinghamshire! Surrey (with 

 zygospores from Thursley Common)! Sussex (Ralfs). 

 Hants \ (Rolfs). Wilts! Devon! Cornwall ! (Raffs). 

 Plankton of Buttermere, Ennerdale Water, Brothers' 

 Water, Hayes Water, Hawes Water, Grasmere, Easdale 

 Tarn, and Stickle Tarn, in the English Lake District ! 



WALES. Fairlv general ! Plankton of many Welsh 



il O e/ 



lakes ! 



SCOTLAND.- -Common ! Zygospores from Loch Inver, 

 Sutherland, and Logie Coldstone, Aberdeen (Ruy and 

 Bissett). Common in the plankton. 



IRELAND.- -Donegal! G-alway (zygospores from Bally - 

 nahinch)! Kerry! Dublin and Wicklow (Archer). 

 Armagh ! Down ! Plankton of the lakes of Gralwav 



e/ 



and Kerry. Lough Xeagh ! 



G-eor/r. Distribution.- -France. Germany. Austria 

 and Galicia. Roumania. Xorway (and Finmark). 

 Sweden. Bornholm. Finland. X. Russia. Faeroes. 

 Siberia. Mongolia. Japan. JSL India. Central 

 Africa (var.). United States. W. Indies (var.). Brazil. 

 Paraguay. 



Xanthidiam antilop&umistliemosk frequent British species 

 of the genus. It rarely occurs in bog's, having a decided pre- 

 VOL. IV. 5 



