94 B1UTISH DESMIDIACE/E. 



times very little longer than broad), deeply constricted, 

 sinus narrow and linear ; semicells subqiiadrate or 

 subrectangular, inferior angles scarcely rounded, sides 

 straight and parallel, superior angles obliquely truncate, 

 apex truncate and straight. Side view of semicell 

 subcircular. Vertical view elliptic, ratio of axes about 

 1 : 1'7. Cell- wall smooth. Chloroplasts axile, one in 

 each semicell, with a central pyrenoid. 



Zygospore globose-octahedral, with eight subacute 

 undulations round the margin. 



Length 14'5-28/x,; breadth 13-5-18 ft; breadth of 

 isthmus 3'2-6/ji; thickness 7'7-9'5/x. 



ENGLAND.- -Near Bowness, Westmoreland (Bissett). 

 Pilmoor, N. Yorks ! Skip with Common, E. Yorks ! 

 Near Brio-o- Lincolnshire ! Dernford Fen and Wicken 



DO 3 



Fen, Cambridge! Enbridge Lake, Hants (Roy). 



WALES.- -Llyn Cor on, Anglesey ! 



SCOTLAND. -- General ! Zygospore from Blackball, 

 Kincardine (Roy fy Bissett). 



IEELAND. Grortahork, and Loughs Connell and 

 Magrath, Donegal! Dublin and Wicklow (ArcJ/er). 



Geoc/r. Distribution.- -France. Germany. Bohemia 

 and Gralicia in Austria. Norway. Sweden. Den- 

 mark. Faeroes. Siam. Australia. United States. 

 Central Africa. 



C. angulosum is closely related to C. Meneghinii, but is 

 distinguished from it by the straight sides and apex of the 

 semicells, the truncate upper angles, and the greater 

 angularity of the semicells. That these distinctions were 



i_^ i/ 



justifiably regarded as specific in character received con- 

 firmation on the discovery of the zygospore by Messrs. Hoy 

 and Bissett. This zygospore differs much from that of C. 

 Meneghinii, being furnished with a few rather low pro- 

 tuberances instead of spines. 



Var. concinnum (Rabenh.) West & Gr. S. West. 



(PL LXXII, figs. 37, 38.) 



Euastrum concinnum Eabenh. Alg. Europ. 1362., no. 1303 cuni fig. 

 Cosmarium concinnum E,einscli Spec. Gen. Alg. 1867, p. 140, t. 22 B. I, 

 f. 1-7 (formse) ; Eacib. Desmidyja Ciastonia, 1892, p. 371 ; Turn. 



