20 BRITISH DESMIDIACE^. 



ENGLAND. Cowgill Wold Moss, Widdale Fell, W. 

 Yorks ! 



Var. Davidsonii (Roy & Biss.) West & Gr. S. West. 



(PL LXVI, figs. 25, 26.) 



0. Davidsonii Roy & Biss. Scott. Desm. 1894, p. 45, t. 1, f. 8. 

 C. tetragonum var. Davidsonii (Roy & Biss.) West & Gr. S. West, Alga-fl. 

 Yorks. 1900, p. 81. 



Cells rather more hexagonal ; sides of semicells 

 straighter, apical angles ronnded and more prominent, 

 giving the apex a protracted appearance; isthmus 

 sometimes broader ; with minute granules within all 

 the undulations, disposed approximately in radial rows, 

 2 or 3 in each row. 



Length 37--40 //,; breadth 25-26 p.; breadth of isth- 

 mus 14-16 p. ; 



ENGLAND. Penyghent, W. Yorks ! Mickle Fell, N. 

 Yorks ! 



SCOTLAND. Morven and near Aboyne, Aberdeen; 

 near Grillan in Strachan, Kincardine ; near Belquhadly 

 in Fern, and in Canlochan, Forfar (Roy fy Bissett). 



Var. elegans (Roy & Biss.) nob. (PI. LXVI, fig. 27.) 



C. elegans Roy & Biss. Scott. Desm. 1894, p. 45, t. 2, f. 5. 



Cells rather more hexagonal ; apical angles large, 

 rounded, and very prominent, causing the apex to 

 appear outstanding with a slight subapical constric- 

 tion ; sides of semicells with 3-4 small undulations 

 between the basal and apical angles ; within each 

 undulation are two radial rows of about 5 or 6 very 

 minute granules. 



Length 43-45 p. ; breadth 28-30 ^ ; breadth of isth- 

 mus 17 p.. 



SCOTLAND. Logie-Coldstone and Grlassel, Aberdeen 

 (Roy $ Bissett). 



60. Cosmarium moniliforme (Turp.) Ralfs. 

 (PI. LXVII, figs. 1-3.) 



? Tessarthonia moniliforme Turp. in Dictionnaire des sciences naturelles, 

 53, 1828, p. 239. 



