22 BRITISH DESMIDIACE^. 



Hungary. Italy. Norway. Sweden. Denmark. 

 S. Russia. Faeroes. Kordofan. Central China. 

 Japan. India. Burma. Ceylon. Australia. Mada- 

 gascar. Central Africa. United States. Jamaica. 

 Porto Kico. Brazil. Ecuador. Bolivia. 



Roy states that " one form of this species has a distinct 

 isthmus,, connecting the semicells ; its zygospore (found in a 

 small pool north of Loch Dawin, Aberdeen) is globular, 

 smooth, and twice the size of a semicell." Perhaps this 

 statement refers to forma panduriformis Heimerl, a form 

 which we find fairly generally distributed. 



Forma punctata Lagerh. (PL LXVII, fig. 4.) 



C. moniliforme (3 punctatum Lagerli. Algol. Bidr. II, 1887, p. 197 ; West 

 & G. S. West, Alg. Madag. 1895, p. 70, t. 9, f. 31. 



Cell-wall punctate, often becoming yellow. 



Lenth 24-43 breadth 14-25 breadth of 



* 



isthmus 3 '5-6* 



WALES.- -Moel Siabod, Carnarvonshire ! 



Geoqr. Distribution. Madagascar. Porto Eico. 



' O 



Forma panduriformis Heimerl. (PI. LXVII, figs. 8-9.) 







C. moniliforme forma panduriformis Heimerl, Desm. alp. 1891, p. 598, 

 t. 5, f. 11 ; West in Naturalist, 1893, p. 214; Schniidle, Beitr. alp. Alg. 

 1895, p. 387 ; West & G. S. West, Alg. S. England, 1897, p. 491 ; Some 

 Desm. U.S. 1898, p. 310; Alga-fl. Yorks. 1900, p. 86; Alg. N. Ireland, 

 1902, p. 41 ; Further Contrib. Plankton Scott. Lochs, 1905, p. 484. 



Dysphinctium inferum Turn. Freshw. Alg. E. India, 1893, p. 40, t. l,f. 21. 



? Pleurotseniopsis Volkensii Hieron. Conj. in Eiigl. Pflanzenw. Ost-Africa, 

 1895, p. 20. [Consult Schniidle, Ost-Afrika Desmicl. 1898, p. 25.] 



Cells with a broader isthmus and an obtusely 

 rounded sinus ; cell- wall smooth. 



Length 1 7*5-25 /x; breadth 10-15//,; breadth of 

 isthmus 6-10 p.. 



ENGLAND.- -Brothers' Water and Helvellyn, West- 

 moreland ! Pilmoor, N. Yorks ! Riccall Common, E. 

 Yorks ! Thursley Common, Surrey ! New Forest, 

 Hants ! Withiel, Cornwall ! 



WALES.- -Capel Curig, Carnarvonshire ! Not un- 

 common in the plankton of the Carnarvonshire lakes ! 



SCOTLAND. Rhiconich, Sutherland ! Moidart, and 



