STAURASTRUM. ] 59 



Length 38-48 /x ; breadth 25'5-36/x; breadth of 

 isthmus 8-14 /x. 



ENGLAND.- -Stye Head Tarn, Cumberland! Rydal 

 Fell, Westmoreland ! Near the side of Windermere, 

 Lancashire ! Cautley Spout, Cocket Moss near 

 Giggleswick, Ogden Clough, and Arncliffe (with 

 zygospores), W. Yorks ! Mickle and Cronkley Fells, 

 and bog near Widdale Beck, N. Yorks ! 



WALES.- -At over 3000 ft. on Snowdon, Carnarvon- 

 shire ! 



SCOTLAND. --General, but scarce; zygospores from 

 near Dinnet, Aberdeen (Roy fy Bissett). 



Geogr. Distribution. Germany. Austria. Norway. 



21. Staurastrum suborbiculare W. & G. S. West. 



(PI. CXXV, figs. 3-5.) 



Staurastrum orbiculare Kalfs forma? Roy & Biss. Scott. Desm. 1893, t. 4, 



f. 7. 

 St. suborbiculare W. & G. S. West, New and Int. Freshw. Alg. 1896, p. 158, 



t. 4, f. 48 ; Alga-fl. Yorks. 1901, p. 101. 



Cells small, about as long as broad, very deeply 

 constricted, sinus narrowly linear ; semicells pyrami- 

 date-subsemicircular, basal angles slightly rounded, 

 sides convex, apex narrow and faintly retuse. Vertical 

 view triangular, angles rounded, sides almost straight 

 (very slightly concave). Cell-wall minutely and densely 

 punctate. 



Zygospore globose, densely covered with small 

 conical verrucae, each of which bears a very short 

 spine at its apex. 



Length 35-44 /x; breadth 35-38 p.; breadth of 

 isthmus 7'5-9'5/x; diam. zygosp. with short spines 

 37*5-45 p,. 



ENGLAND. Cam Fell, W. Yorks ! 



SCOTLAND. --Glas Mhoel, Perth (with zygospores) ! 



This species is distinguished from St. orbicular ev SLY. Ralfsii 

 by the more depressed semicells, with retuse apices., and by 

 the very different nature of the zygospore. 



