32 BRITISH DESMIDIACE^:. 



SCOTLAND.- -Logie, Coldstone and Blairglas, Aber- 

 deen ; Glen Coe, Argyle (Roy & Biss.). 

 IRELAND. Connemara (Arch.). 

 Geogr. Distribution.- -Finland. 



Until quite recently this species had never been seen since 

 it was discovered by Archer except by Roy and Bissett. 



The latter investigators remark that it is "extremely rare," 

 and that ' its nearest ally is St. maamense Arch.," but that " the 

 stout spines sufficiently distinguish it." Gronblad now records 

 it from Finland. 



61. Staurastrum Gatniense W. & G. S. West. 

 (PL CXXXV, figs. 14, 15.) 



St. Gatniense West & G. S. West, Alg. N. Ireland, 1902, p. 48, t. 2, f. 35. 



Cells small, slightly broader than long, not counting 

 the spines, very deeply constricted, sinus open, narrow, 

 and finally dilated at the extremity ; semicells elliptic- 

 trapeziform, apex broad and slightly undulate, basal 

 angles provided with a short stout converging spine, 

 lateral margins slightly convex, and with two distant 

 spines. Vertical view triangular, angles tumid and with 

 a ring of denticulabions, sides smooth and very slightly 

 concave. 



Zygospore unknown. 



Length 27 '5^ ; breadth, without spines, 29 y. ; with 

 spines, 33*5 ^ ; breadth of isthmus 8 ji. 



IRELAND. --Lough Gatny, Co. Donegal ! 



This peculiar Staurastrum is not very closely allied to any 

 other British species of the genus. 



62. Staurastrum bifidum (Ehr.) Breb. 

 (PL CXXXIV, fig. 4.) 



Desmidium bidens Ehr. Inf. 1838, p. 141, t. 10, f. 11. 



Phycastrum bifidum Kutz. Phyc. Germ. 1845, p. 138 ; Spec. Alg. 1S49, 



p. 180. 

 Staurastrum bifidum (Ehr.) Breb. in Ralfs, Brit. Desm. 1848, p. 215; Arch. 



in Pritch. Inf. 1861, p. 741 ; Rabenh. Krypt. El. Sachs. 1863, p. 192 ; 



