64 1SKITISH DESMIDIACE^. 



WALES. OapelCurig!, Llyn-y-cwm-ffynon !, Glyder 

 Fawr (Roy), and Pen-y-gwryd (Roy), Carnarvonshire. 



SCOTLAND. --General, but scarce ! (Roy $' Bissett). 

 Common in the Outer Hebrides ! 



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

 Dublin and Wicklow (Archer). 



Geonr. Distribution. Germany. Galicia. Norway. 



' i/ i 



Sweden. Poland. Siain. India. Ceylon. West 

 Africa. New Zealand. Abyssinia. United States. 

 Paraguay. - Patagonia (form) . 



C. exiguum is a rather uncommon species of very charac- 

 teristic form. It has a wide distribution in bogs and swamps. 

 The largest forms are those mentioned by Nordstedt from 

 New Zealand as " forma paulo major 5 ': length 32-36 IUL 

 breadth 22 /LI ; breadth of isthmus 6-6*5 /,(. The same author also 

 describes a trigonal form (vide f Freslrvv. Alg. N. Zeal./ 1888, 

 p. 58, t. 6, f. 13). A form from Michigan, U. S. A., with more 

 rounded semicells, had a length of 41 /.t and a breadth of 24 /<; 

 vide West & G. S. West, ' Some Desm. U. S./ 1898, p. 303. 



Var. pressum West & G. S. West. (PL LXX, 



figs. 23, 24.) 



C. exiguum Arch. var. pressnm West & G. S. West, New Brit. Fresh ~vv. 

 Alg. 1894, p. 6, t. 1, f. 1. 



A smaller variety with proportionately narrower 

 cells, semicells slightly narrowed from base to apex, 

 and with slightly retuse apices. 



Length 12'5-14'5/x; breadth 5'8-6'5/x; breadth 

 of isthmus 3'5-4'5 /x ; thickness 5 /x. 



ENGLAND.- -Elter Water, Cumberland ! 



Var. subrectangulum var. nor. (PL LXX, figs. 20-22.) 



Cells proportionately broader; sinus closed, linear 

 with a dilated apex ; semicells transversely snbrectan- 

 gular. 



Length 14*5 ju-15 /^; breadth 10'7-11'5 JJL; breadth 

 of isthmus 2'2-3*2 \L\ thickness 7 /u. 



ENGLAND.- -Chippenham Fen, Cambridgeshire ! 



