92 BRITISH DESMIDIACEJE. 



42-44 p, with processes 67-72 /A; length of processes 

 15-17*5 /I. 



ENGLAND. Cumberland! Westmoreland! (Rolfs). 

 W. and N. Yorks ! Lancashire! Warwick (Wills). 

 Surrey ! (Ralfs). Sussex (Ralfs). Hants ! (Rolfs). 

 Devon ! Cornwall ! (Ralfs). 



WALES.- -Fairly general in the north ! Zygospore 

 from Dolgelly, Merioneth (Ralfs). 



SCOTLAND. Greneral ! Zygospores from Dinnet, 

 Aberdeen, and from Fowlis Wester, Perth (Rot/ fy 

 Bissett). Outer Hebrides ! Orkneys! Shetlands ! 



IRELAND.- -Donegal ! Mayo ! Galway ! Kerry ! 

 Dublin and Wicklow (Archer). Antrim ! 



Geoc/r. Distribution. France. Germany. Austria 

 and Gralicia. Hungary. Italy. Norway. Sweden. 

 Denmark. Bornholm. Finland. 1ST. and S. Russia. 

 Russian Lapland. Greenland. New Zealand. United 

 States. Brazil. 



This is the most abundant of the smaller British species of 

 the genus which possess deeply-lobecl semicells. It is known 

 at once by the form of the polar lobe and by the denticula- 

 tions bordering the interlobular incisions. It is somewhat 

 variable in its relative proportions. Most specimens are a 

 little longer than broad, but individuals are sometimes met 

 with of equal length and breadth. 



M. papillifera cannot be confused with M. conferta if the 

 polar lobe is carefully examined. It must likewise be 

 remembered that the latter species is smaller, very much 

 rarer, and more restricted in its distribution. 



Some forms occasionally exhibit a roughness on the exte- 

 rior of the cell-wall somewhat similar to that commonly 

 present on M. Jenneri. Cells of this kind are invariably old 

 ones and may exhibit a rather corroded outline. Schmidle 

 ('Beitv. alp. Alg./ 1896, p. 23 cum fig.) has named forms of 

 this nature which he found in the Austrian Tyrol " var. 



verrucosa.' 



Forma major. (PI. XLIV, fig. 3.) 



Length 200 /JL; breadth 170 //,; breadth of polar 

 lobe 51 /JL; breadth of isthmus 29 p. 



WALES. Llyii Ogwen, Carnarvonshire ! 



