STAURASTRUM. 19 



A form with smaller cells and relatively stouter 

 spines ; sinus broadly rounded and isthmus cylindrical. 



Length, without spines, 25-28 [i ; breadth, without 

 spines, 16-18 [JL ; length of spines 25-31 [i ; breadth of 

 isthmus 6*5-7 ^. 



SCOTLAND.- -Plankton of Loch Raiar, Loch Morar and 

 Loch Ghriama, Sutherland ! 



51. Staurastrum curvatum West. 

 (PL CXXX, figs. 15, 16.) 



Staurastrum curcnium West, Alg. W. Ireland, 1892, p. 172, t. 22, f. 13 ; 

 West & G. S. West, Scott. Freshw. Plankton, I, p. 543, t. 17, f. 12 ; Further 

 Contrib. Freshw. Plankton Scott. Lochs, 1905, p. 485 ; Brit. Freshw. 

 Phytoplankton, etc., 1909, p. 202 ; Wahlburg, Bidr. kanne. Littois- 

 trask, 1913, p. 48. 



Cells of medium size, rather longer than broad, not 

 including the spines, deeply constricted, sinus nearly 

 rectangular and obtuse at its apex, semicells lunate, 

 directed away from each other ; apex of semicell concave, 

 each angle terminating in a long graceful diverging spine. 

 Vertical view triangular, lateral margins concave, angles 

 attenuated, and each one ending in a long spine. 

 Cell-wall smooth ; chloroplast axile, with a central 

 pyrenoid and a pair of lobes extending into each angle. 



Zygospore unknown. 



Length, without spines, 25-32'5 \L ; breadth, without 

 spines, 20-35 \L ; including spines, 71-75 \L ; length of 

 spines 20-23 \L ; breadth of isthmus 5-8 pt . 



ENGLAND. Plankton of Buttermere, Ennerdale Water, 

 Bassenthwaite Water, and Wast Water, Cumberland ! 

 Plankton of Codale Tarn, Grasmere, Stickle Tarn and 

 Windermere, Westmoreland ! Plankton of Bracebridge 

 Pool, Sutton Park, War wicks ! 



WALES.- -In the plankton. 



lRELAND.--Derryclare Lough and Ballynahinch, Co. 

 Galway ! Lough Guitane, Co. Kerry ! 



SCOTLAND.- -Plankton of Loch Shin and Loch nan 

 Cuinne, Sutherland ! Loch Luichart and Loch Rosque, 

 Eoss ! Plankton of Loch na Cloiche Sgoilt, Loch Morar, 



