MICE AST ERIAS. 109 



median notch; semicells in vertical view lanceolate- 

 fusiform, with acuminate poles, and a broad, rounded- 

 conical elevation at the middle on each side. 



Breadth 170 /A; thickness 50 /x. 



ENGLAND. Bowness, Westmoreland ! 



Note. In Cooke's f British Desmids' 011 PL XLYII is figured 

 (fig. 5) " M. denticidata var. licmoides Wills," but no descrip- 

 tion of this form is given. It has both polar lobe and lateral 

 lobes much reduced, and appears to us to be merely a mon- 

 strosity produced by rapid cell-division. Imperfectly de- 

 veloped semicells lobed in the manner of "var. licmoides" are 

 not uncommonly met with in collections containing large 

 numbers of M. denticidata. 



M. denticidata var. intermedia Bennett ( ( Freshw. Alg. 

 Hamps. and Devon/ 1890, p. 6, t. 1, f. 8) is a doubtful form, 

 so imperfectly described and badly figured that it is quite 

 impossible to identify it. There is, moreover, a var. inter- 

 media of this species described by Nordstedt (in "\Yittr. & 

 Nordst. ' Alg. Exsic/ 1880, no. 370). 



13. Micrasterias verrucosa Bissett. 



(PL LI, fig. 2.) 



Micrasterias verrucosa "'Roy" in Wolle, Bull. Torr. Bot. Club, 1885, p. 127, 

 t. 51, f. 10; Wolle, Freshw. Alg. U.S. 1887, p. 41, t, 59, f. 10; Bissett in 

 Eoy and Biss. Scott. Desni. 1893, p. 174, t. 1, f. 2 ["Bissett" stated to 

 be the .author of the species]. 



Cells large, about ly times longer than broad, 

 octangularly elliptic, very deeply constricted, sinus 

 narrowly linear ; semicells 5 -lobed, incisions narrowly 

 linear; lateral lobes somewhat unequal and broadly 

 cuneate, upper ones slightly broader than lower ones ; 

 lobulation similar to that of M. denticidata, ultimate 

 divisions more rounded in the upper lateral lobes 

 than in the lower ones ; polar lobe similar to that of 

 M. denticidata. Vertical view linear - oblong, with 

 acute poles and deeply undulate sides. Cell- wall of a 

 brownish colour, with numerous small subgranulate 

 protuberances scattered over its surface ; the three 

 largest in a transverse row near the median base of 



