71 BRITISH DESMIDIACE^. 



i> or :5 concentric series of verrucsc around the middle of 

 the apex, the actual centre being smooth. 



X\ -os pore unknown. 



Length 40-48 [Ji ; breadth 30-34 (JL ; breadth of apex 



IT-:. -JO;/.. 



ENGLAND- -Penyghent and Mickle Fell, N. Yorks ! 



SCOTLAND. Craig Phiobaidh near Girnoc and Corrie 

 cf Loch Ceanmhor, Aberdeen; Canlochan, Forfar; Alva 

 (iliMi. Stirling (Roy & Biss.). 



Geogr. Distribution. Norway. Sweden. Faeroes. 

 Nova Zembla, Spitzbergen. W. Greenland. 



The British examples differ from the original specimens from 

 Spitzbergen in their proportionate greater length and in the 

 convex sides in the vertical view. They also seem to be more 

 Mnmuly \Trrucose. 



Yar. eboracensis West. (PL CXL, figs. 8-10.) 



St. n,;iriih-* var. eboracensis West, Alg. X. Yorks. 1889, p. 273, t. 201, f. 8 ; 

 \\t-t ,V G. S. West, Alga-fl. Yorks. 1902, p. 106. 



Differs from the type in its deeper lateral incisions,, 

 which are almost linear. 

 Dimensions as in the type. 

 KN< ; LA XD. Mickle Fell, N. Yorks ! 



95. Staurastrum asperum Breb. 

 (I'l. CXL. figs. 11-13; PL CXLI, fig. 21.) 



,v/'/'//v/.x//-///,, asperum Breb. in Ualfs, Brit. Desm. 1848, p. 139, t. 22, f. G, 

 t. 2:5. f. 12 a : Arch, in Pritch. Inf. 18(51, p. 740; Rabeuh. Flor. Europ. 

 AI-. isr.s. ,,. -Jd'.i : Ci.Dke, Brit. Desin. 1887, p. 154, t, 53, f. 4 : De Toni, 

 Syll. Alg. lssi, p. 117.-): |{,,y & Biss. Scott. Uesm. 1893, p. 179: West 

 A- G. S. West, X<-\\ Brit. Freshw. Alg. 1894, p. 11, t. 2, f. 48; Comere,. 

 Desm.de l-'ram-r, I'.ml, p. KJO, t. 12, f. 27. 



l>i'h/nii<litti,, (Xtii/ir.i*/nnn) iixj^ntnt Reinsch, Algenfl. Frank. 1867, p. 160. 



I VI Is i-jitlicr under medium size, about li times longer 

 than broad, deeply constricted, sinus open and nearly 

 rectangular : semicells broadly elliptical, widest towards 

 tho apex, dorsal margin much less convex than the 

 ventral, aii^los broadly rounded; peripheral margin 



