18 BRITISH DESMIDIACE^]. 



depth ; lateral lobes subquadrate, with rounded angles 

 and retuse sides ; intermediate lobules mamillate and 

 prominent ; semicells with a large protuberance within 

 each lateral lobe, and with four in the centre, two small 

 ones immediately above the isthmus, and two larger 

 ones immediately above them. Side view of semicell 

 subquadrate in the lower half, with retuse sides ; upper 

 half pyramidate, with deeply retuse sides and a dilated, 

 rounded-truncate apex ; intermediate lobule emar- 

 ginate ; lateral lobes (at base) rhomboidal, with rounded 

 angles and retuse sides. Vertical view elliptic, with 

 four prominent protuberances along each side ; inter- 

 mediate lobules emarginate ; polar lobe quadrate- 

 oblong, sides slightly convex, poles deeply emarginate. 

 Cell-wall punctate. 



Zygospore unknown. 



Length 98-117^; breadth 53-64 //,; breadth of 

 isthmus 17-18 /A; thickness 35-38 {JL. 



ENGLAND. Cumberland ! Westmoreland ! (Ralfs) . 

 W. and N". Yorks ! Lancashire ! Surrey ! Sussex 

 (Rolfs). Hants. (Ralfs). Wilts! (Tat urn). Devon! 

 (Bennett). Cornwall (Marquand). 



WALES. General in Carnarvonshire (Glyder Fach 

 at 2,200 ft.) ! Dolgelly, Merioneth (Ralfs). 



SCOTLAND. General, but not abundant ! (Roy fy 

 Bissett). Outer Hebrides ! 



IRELAND. - - Donegal ! Mayo ! Gal way ! Kerry ! 

 Dublin and Wicklow (Archer). 



Geogr. Distribution. France. Germany. Norwa}^. 

 Sweden. Denmark. X. Russia, India. United States. 



E. affine is a very characteristic species and cannot be 

 easily confused with any other. The disposition of the surface 

 protuberances and the form of the polar lobe at once dis- 

 tinguish it from E. Didelta. It often occurs in quantity in 

 upland Sphagnum-bo gSj and is not infrequently associated 

 with E. ampullaceum. 



Nordstedt has described a " forma scrobiculata" of it/ with 

 a conspicuous central scrobiculation, hut we have not observed 

 this form from Britain. 



