104 BRITISH DESMIDIACE.E. 



its angles may be produced to form very short bidentate 

 processes. 



The inferior lateral lobes occasionally possess the same 

 number of ultimate lobules as the superior lateral lobes, and 

 in more normal specimens in which the inferior lateral lobes 

 are only subdivided into four divisions, some or all of these 

 divisions are sometimes tridentate. 



Forma graimlata West. 



M. rotata forma granulata West, Alg. W. Ireland, 1892, p. 134. 



Cell-wall distinctly granulate, granules flattened and 

 irregularly scattered. 



IRELAND. Lough Aunierin, Galway ! 



Forma evoluta Turn. 



M. rotata forma evoluta Turn. Freshw. Alg. E. India, 1893, p. 167, 



t. 23, f. 1. 

 M. rotata var. pulchra Lemm. Zweiter Beitrag zur Algenflora des Ploner 



Seengebietes, Forschungsberichte Biol. Stat. Plon, iv, 1896, p. 173, 



fig. 7. 



Incisions between the lobes and lobules more open 

 than in the type ; polar lobe furnished with a pair of 

 small teeth on the apical margin on each side of the 

 median emargination. 



Length 270-282^; breadth 220-262^. 



SCOTLAND. Sligachan in Skye, Inverness ! 



Geocjr. Distribution. Germany. India. 



The polar lobe of this form may or may not be exserted, 

 and the cell-wall is sometimes strongly punctate. 



Var. urnigera Bennett. 



M. rotata var. urnigera Benn. Freshw. Alg. Hamps. and Devon, 1890, 

 p. 6, t. 1, f. 9. 



Slightly larger than the type ; polar lobe " urn-like' 

 and projecting for a distance of 25 p.. 



Length (including projecting polar lobe) 325 /n ; 

 breadth 250 p,. 



ENGLAND. Lyndhurst, Hants (Bennett). 



We are unacquainted with this variety, and have not 

 reproduced Bennett's figure, as it is too much of a caricature. 



