STAURASTROI. 45 



Length, without spines, 26-32*5 ^ ; breadth, without 

 spines, 26-31 ^ ; breadth of isthmus 10-11^; length 

 of spines about 7 p: 



ENGLAND.- -Hampsfell, Lancashire ! Cross-in-hand, 

 Sussex (Ralfs). Penzance, Cornwall (Rolfs}. 



SCOTLAND. Aberdeen, Kincardine, Forfar, Perth 



(Roy & Biss.). 

 IRELAND. --Near Cllenties, Donegal! Dublin and 



Wicklow (Arch.). 



Geoyr. Distribution- -France. Germany. Hungary. 

 Norway.. Sweden. Denmark. Bornholm. Finland. 

 N. Russia. United States. 



The semicells of typical specimens of this species possess 9 

 spines, but irregularities in the number or position of the accessory 

 spines (i. e. those not at the angles of the cell) are not infrequent. 



71. Staurastrum Simonyi Heimerl. 

 (PL CXXXV, figs. 1-4.) 



M. Ximoiiyi Heimerl, Desm. alp. 1891, p. 606, t. 5, f. 23 ; Liitkem. Desm. 



Millstattersees, 1900, p. 81 ; Borge, Sao Paulo Siisswasseralgen, 1918, 



p. 53. 

 ,S7. Reinschii West, Ala-. W. Ireland, IS'.IL>, p. 174 ; West & G. S. West, Alg. 



S. England, 1897, p. 493 ; G. S. West. Variation Desm. 1899, p. 392, 



t, 11, f. 16-20; West & G. S. West, Alga-fl. Yorks. 1902, p. 98; Alg. 



N. Ireland, 1902, p. 47; Borge, Beitrage Alg. Schweden, 190(5, p. 48, 



t. 3, f. 39. 



Cells small, about as long as broad, deeply constricted ; 

 sinus acute, widening towards the exterior; semicells 

 usually elliptical or subfusiform, sometimes subsemi- 

 circular, dorsal and ventral margins as a rule almost 

 equally convex, lateral angles truncate and provided 

 with 2-4 sharp spines, apical margin with a series of 

 typically 4 spines between each pair of consecutive 

 angles, the two median ones being the largest and pro- 

 jecting conspicuously from the apex, the other two spines 

 sometimes entirely wanting : further with an occasional 



/ t_^ ' 



series of 4 smaller spines beneath the first series. Ver- 

 tical view triangular, lateral margins straight, slightly 

 concave or even a little convex, angles obtusely rounded 



