58 BRITISH DESMIDIACE^E. 



Cells rather under medium size, about as long as 

 broad, sinus acute and not very widely open ; semicells 

 elliptic -reniform, dorsal and ventral margins almost 

 equally convex, cell wall uniformly covered with stout 

 spines, about 14-20 visible along the peripheral margin, 

 arranged in obscure circles round the angles, and more 

 or less scattered further away. Vertical view triangular, 

 sides slightly concave, angles broadly rounded, about 

 9 spines visible along each lateral margin, spines in the 

 centre of the apex sparsely scattered. 



Zygospore unknown. 



Length, without spines, 37*5-41 pi ; with spines, 

 47*5-51 [x ; breadth, without spines, 37 '5-40 pi; with 

 spines, 48-50 pi ; breadth of isthmus 11-1 2 pi. 



ENGLAND. Gunwen Moor, Cornwall ! 



WALES. Capel Curig, Carnarvonshire ! 



Geogr. Distribution. --India (var.). United States. 



Var. delicatulum W. & G. S. West. (PL CXXXVII, 



%. 3.) 



St. gladiosiun var. delicatulum West & G. S. West, Notes Algse, II, 1900, 

 p'. 296, t. 1, f. 14 ; Alga-fl. Yorks. 1902, p. 99. 



A variety with more delicate spines, which are some- 

 times slightly curved, and are far less numerous more 

 remote from the angles. 



Length, without spines, 37*5 pi: with spines, 44 pi; 

 breadth, without spines, 38 '5 pi; with spines, 50 pi; 

 breadth of isthmus, 14 pi. 



ENGLAND.- -Malham Tarn, W. Yorks! 



The form of the cell in this variety, also the number and length 

 of the spines, are nearer to those of St. gladioswn than any other 

 species. The semicells are more depressed than in St. teliferum, 

 and the spines are longer and more delicate. 



84. Staurastrum teliferum Ralfs. 

 (PI. CXXXVI, figs. 2-6.) 



St. teliferum Ralfs. Brit. Beam. 1848, p. 128, t. 22, f. 4, t, 34, f. 14 ; Arch, in 

 Pritch. Inf. 1861, p. 739, t. 3, f. 20-21 ; Rabeiih. Krypt.-fl. Sachs. 1863, 

 p. 190 ; De Not. Desm. Ital. 1867, p. 50, t. 4, f. 40 ; Rabenh. Flor. Europ. 



