62 BRITISH DESMIDIACE^:. 



of lower part of semicell and particularly of polar lobe 

 much reduced (as seen in vertical view). 



Length 51-63 ju ; breadth 36-42 ^ ; breadth of polar 

 lobe 24-28/1 ; breadth of isthmus 10 ll'5fi ; thickness 

 21-26 p.. 



ENGLAND. More frequent than the type ! 



WALES. General in Carnarvonshire ! 



SCOTLAND. General and abundant ! 



IRELAND. General and abundant ! 



E. pectinatum forma intermedia Boldt ( f Desm. Gronland/ 

 1888, p. 6, t. 1, f. 3) comes very near this variety, but in 

 Boldt's form the polar lobe is very small and its lateral 

 margins are almost vertical. Boldt does not state whether 

 the protuberances are reduced in his form or not,, whereas 

 this is one of the leading features in var. inevolutum. In the 

 latter variety the angles of the polar lobe and the lateral 

 lobules are broadly truncate or truncate -emarginate in ver- 

 tical view, scarcely bilobulate as in the type. 



Var. brachylobum Wittr. (PI. XXXIX, fig. 16.) 



E. pectinatum var. brachylobum Wittr. Gotl. Ol. sotv. Alo-. 1872, p. 48, t. 

 4, f. 5 ; De Toni, Syll. Alg. 1889, p. 1068 ; Roy & Biss. Scott. Desm. 

 1893, p. 177. 



Lobes of semicell broad and very short, margins 

 widely retuse ; semicells with six protuberances, one 

 in the centre, one within the middle of the polar lobe, 

 and one within each angle of the lateral lobes ; poles 

 of vertical view simple and rounded (not emarginate). 



Length 70 /x; breadth 50 /x; breadth of polar lobe 

 32/x; breadth of isthmus 15/x; thickness 33/x. 



SCOTLAND.--" Not so common ' (Roy fy Bissett). 



Geogr. Distribution . Sweden. 



We have never seen any form of E. pectinatum at all 

 approaching var. brachylobnm Wittr. 



Half s in his ' British Desmids ' describes and figures a form 

 (p. 86, t. 14, f. 5c) which lie calls '< var. /3." He states that 

 the angles of the polar lobe are slightly emarginate in front 

 view, but it must be remembered that this effect is produced 

 when the cell is in a slightly-oblique position, and his figure 

 undoubtedly gives one the idea that this was the case. 



