42 BRITISH DESMIDIACE2E. 



W. Ireland/ 1892, p. 139), and others that we have seen, bear 

 a striking resemblance to large forms of E. bidentatum Nag. 

 They differ from E. pic-turn in having the lateral teeth reduced 

 to acute granules, and in the replacement of the special, 

 granulated -protuberances by single large granules. They 

 would be almost equally well placed under E. bidentatum, 

 except for their size and additional protuberances. 



Length 79 /n ; breadth 52 // ; breadth of isthmus 14 /m. 

 (PL 38, fig. 2.) 



WALES. Moel Siabod and Llyn Ogwen, Carnarvonshire ! 



SCOTLAND. Rhiconich, Sutherland ! 



IRELAND. Lakes near Recess, Oorid and Arderry Loughs, 

 Gal way ! Glen Caragh, Lough Guitane, Castletown and 

 CarrantuohilL Kerrv ! 



7 *. 



26. Euastrum divaricatum Lund. 

 (PI. XXXVIII, figs. 3, 4.) 



Euastrum divaricatum Lund. Desm. Sviec. 1871, p. 21, t. 2, f . 5 ; ? Wolle, 

 Desin. U. S. 1884, p. 104, t. 26, f . 18-19 ; De Toni, Syll. Alg. 1899, 

 p. 1100 ; Turner, Freshw. Mg. E. India, 1893, p. 84, t. 11, f. 22 ; Eichler, 

 Mat. flor. Meidz. 1894, p. 130. 



Helierella divaricata, Kuntze, Revis. gen. plant. 1891, p. 898. 



Cells small, 1 J times longer than broad, very deeply 

 constricted, sinus narrowly linear with a dilated 

 extremity ; semicells subtriangular, rapidly attenuated 

 to the convexo-truncate apex, more or less three-lobed ; 

 polar lobe very broad, rectangular-oblong, each apical 

 angle furnished with a small spine, median incision 

 deep and open ; lateral lobes bilobulate, upper lobules 

 widely triangular and rounded, lower lobules truncate- 



t/ O 



rounded, furnished with a denticulation at the entrance 

 to the sinus and with a horizontal or upwardly- 

 diverging spine ; semicells with a protuberance in the 

 middle above the isthmus, biverrucose, triverrucose, or 

 granulate, with a large rounded granule on each side 

 of the apical incision at the base of the polar lobe, and 

 with about four granules within the lateral margins 



o o 



and two within the apex. Side view of semicell ovate, 

 apex furnished with a small spine, and with a granulate 

 or emarginate protuberance at each side near the base. 



