56 BRITISH DESMIDIACE.E. 



constricted, sinus open, almost rectangular ; semicells 

 broadly elliptical ; cell- wall beset with spines of varying 

 lengths, the longest being arranged at the angles. 

 Vertical view triangular with slightly convex sides. 

 Chloroplast axile with a central pyrenoid in each semicell. 



Zygospore unknown. 



Length 76-85 (JL ; breadth 55-65 JJL ; breadth of isth- 

 mus 25 [Ji ; length of spines at angles 11-15 [A. 



ENGLAND. Lindeth, Westmoreland ! 



WALES. Capel Curig, Carnarvonshire ! 



This species differs from St. polytrichum in its larger size and 

 in its relatively sharper spines of varying lengths. St. Saxonicum 

 differs in its snorter uniform spines. 



Tar. cambricum West. (PL CXXXVII, figs. 15, 16.) 



St. cumbricum var. cambricum West, Alg. N. Wales, 1890, p. 17, t. 5, f. 0, 

 t, 0, f. 37. 



Differs from the type in its narrower isthmus and 

 somewhat rhomb oidal form of the semicells. 



Length 62-83 ^ ; breadth 48-64 JJL ; breadth of isthmus 

 13-20 pi. 



WALES. Capel Curig. Carnarvonshire ! 



82. Staurastrum echinatum Breb. 

 (PL CXXXVII, fig. 12.) 



St. echinatum Breb. in Ralfs, Brit, Desm. 1848, p. 215, t. 35, f. 24 ; Arch, in 

 Pritch. Inf. 1861, p. 739; Rabenh. Flor. Europ. Alg. 1868, p. 213; 

 Kirchn. Alg. Schles. 1878, p. 166 ; Wolle, Desm. U. S. 1884, p. 141, 

 t. 45, f. 31. 32 (fig. not accurate) ; Hansg. Prodr. Algenfl. Bohm. 1888, 

 p. 214 ; West, Desm. Maine, 1888, p. 340 ; De Toni, Syll. Alg. 1889, 

 p. 1171 ; Turn. Freshw. Alg. E. India, 1893, p. 112, t. 16, f. 48 ; Roy & 

 Biss. Scott. Desm. 1894. p. 19 ; Comere, Desm. de France, 1901, p. 172, 

 t, 12, f. 22 ; ? West & G. S. West, Freshw. Chlorophy. Koh Chang, 1901, 

 p. 177, t. 3, f. 31 (forma) ; Cushman in Rhodora, 19*03, p. 224 and 253 ; 

 ? G. S. West, Alg. Third Tanganyika Expedit. 1907, p. 125 (forma) ; 

 Borge, Botan. Notiser, 1913, p. 49, t. 3, f. 36. 



Cells small, slightly longer than broad, deeply con- 

 stricted, sinus open and acute-angled ; semicells broadly 

 elliptical, angles rounded ; cell- wall covered with rather 

 short spines, which are considerably dilated at the base, 



