102 BRITISH DESMIDIACE^}. 



Ph. (Stenactinium) paradoxum Nag. Gatt. einz. Alg. 1849, p. 128. 

 Didymidium (Stauraslrum) paradoxum Reinsch, Alg. Frank. 1867, p. 164 

 (in part). 



Cells of small or medium size, 1 |-2j times longer than 

 broad, excluding the processes ; constriction moderately 

 deep, sinus acute ; semicells cup-shaped or cuneate, 

 lower angles broadly rounded, semicells becoming wider 

 towards the apex, which is nearly flat, upper angles 

 produced to form fairly long tapering and diverging 

 processes, tipped with 3 or 4* spines of varying size, and 

 provided with numerous series of denticulations. Ver- 

 tical view usually 3- or 4-angular, sides straight or very 

 slightly concave, angles produced into ]ong processes, 

 centre of apex quite smooth, sometimes with a series of 

 short spines or granules just within each lateral margin. 

 Chloroplast axile, with a central pyrenoid in the centra 

 of each semicell and a pair of lobes extending into each 

 angle. 



Zygospore globular, not large, with few long spines,. 

 2-3-fid at the apex (Roy & Bissett). 



Length 21-36 (JL ; breadth, including processes, 41- 

 70 [Ji ; breadth of isthmus 5-12^. 



ENGLAND. Cumberland, and in the plankton of 

 Buttermere, Crummock Water, Derwentwater and 

 Wast Water ! Westmoreland, and in the plankton of Red 

 Tarn, Grasmere and Windermere ! W., N., and E. Yorkst 

 Oxfordshire ! Plankton of pools in Sutton Park, War- 

 wickshire ! Gloucester (Ralfs). Surrey ! Sussex (Rolfs). 

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



WALES.- -Bethesda !, Capel Curig ! (Cooke & Wills), 

 Llandudno !, Llyn Bochlwyd !. Bettws-y-coed (Roy), 

 Llyn-y-cwm-ffynon ! and Glyder Fach !, Carnarvonshire. 

 Llyn Cor on !, Anglesea, and Holy head ! 



SCOTLAND. General, zygospore from Kerloch, Kin- 

 cardine (Roy & Biss.). Lewis and Harris, Outer Hebrides! 

 Orkneys and Shetlands, and in the plankton ! Common 

 in the general plankton ! 



IRELAND.- -Donegal ! Mayo ! Galway ! Kerry ! Dub- 

 lin and Wicklow (Arch.). Down ! Plankton of Mayo 



