38 BEITISH DESUIDIACE./E. 



poles acutely rounded, with a truncate granulate pro- 

 tuberance at the middle on each side. 



Zygospore unknown. 



Length 39-50 /x ; breadth 28-33 /x ; breadth across 

 polar lobe 20-23 p. ; breadth of isthmus 7-9 /x ; thick- 

 ness 18-20 /x. 



ENGLAND. Hampsfell, Lancashire ! 



SCOTLAND. Rhiconich, Sutherland ! Aboyne, Aber- 

 deen ! 



IRELAND. Near Grlenties and Lough Nacally, 

 Donegal ! Derryclare Lough, Galway ! 



Geogr. Distribution . Australia. 



This species differs from E. denticulatum (Kirclin.) Gay in 

 its larger size, in the form of the polar lobe, and in the 

 bilobulate condition of the lateral lobes. 



23. Euastrum spinosum Ralfs. 

 (PI. XXXVII, figs. 14, 15.) 



Euastrum spinosum Ralfs in Ann. Mas^. Nat. Hist. 1844, xiv, p. 192, t. 7, 



f . 6 ; Hass. Brit. Freshw. Alg. 1845, p. 384, t. 91, f . 9. 

 E. elegans (Breb.) Kiitz. v&r.spinosv.m Ealfs, Brit. Desm. 1848, p. 89, t. 14, 



f . 7 f-l ; Kabenh. Flor. Europ. Algar. Ill, 1868, p. 185 ; Kirchn. Alg. 



Schles. 1878, p. 159 ; Cooke, Brit. Desm. 1886, p. 74, t. 35, f. 5 ; Hansg. 



Prodr. Alcjenfl. Bohui. 1888, p. 252 ; West & G. S. West, Some N. Amer. 



Desm. 1896, p. 244, t, 14, f. 27. 



Cells small, almost If times longer than broad, 

 deeply constricted, sinus narrowly linear ; semicells 

 pyramidate, with convex sides which are gently sinuate, 

 bearing one or two dentic illations on the basal sinua- 

 tion, and a short, upwardly-directed spine on each of 

 the other two sinuations, apex rounded-truncate, with 

 a rather deep and narrow median incision ; semicells 

 with a quadriverrucose protuberance in the middle 

 above the isthmus, a wart-like granule on each side of 

 the apical incision, and a number of small granules or 

 fine denticulations within the marginal sinuations and 

 at the apex. Side view of semicell ovate-pyramidate, 

 apex rounded, with a small emarginate protuberance 

 at the base on each side, lateral margins undulate. 



