FRESHWATER PLANKTON ALG.F FROM CEYLON 
169 
M. Americana (Ehrenb.) Ralfs. Loc. 24, 32. Distr. Eur., 
Greenland, N. and S. Amer., Afr. 
M. foliage a Bail. Loc. 27. Distr. Eur., Ceylon. 
Cosmarium Corda. 
C. obsoletum (Hantzsch) Reinsch. Loc. 27. Distr. General 
(incl. Ceylon). 
C. circ glare Reinsch. Loc. 44. Distr. Eur., N. andS. Amer., 
Afr., India. 
C. undulatum Corda. Loc. 5. Distr. General. 
C. depressum (Naeg.) Lund. The form of semi-cell agrees with 
that of forma brunnea Schmidle 1888, the forma figured by Strom 
1921, and with C. Scenedesmus Delponte var. intermedium Gut- 
winsky 1892, now regarded as belonging to this species. The cell- 
wall was colourless. Loc. 5, 24, 43, 56. Distr. General (incl. 
Ceylon). 
C. pseud onitidulum Nordst. Loc. 6,9. Distr. Eur., N. Amer., 
Central China, Siam. 
C. moniliforme (Turp.) Ralfs. Loc. 32. Distr. General (incl. 
Ceylon). 
C. subreinschii Schmidle var. ocellatum W. & G. S. West. 
Loc. 6 (rare), 9 (rare). Distr. Ceylon. 
C. pygmjeum Arch. Loc. 6, 9. Distr. General (incl. Ceylon). 
C. bireme Nordst. W. & G. S. West record this and the closely 
similar C. bipaxillum from Ceylon. The latter we have not found, 
all our specimens being distinguished in vertical view by the more 
elongated and tapering papilla, which is represented in C. bipaxillum 
by a small hemispherical granule directed backwards. C. bireme is 
also allied to C. polygonum , but here the papilla is represented by a 
broad central tumour. Loc. 5, 24. Distr. Mostly tropical (incl. 
Ceylon). 
C. sexangulare Lund. Loc. 6, 9. Distr. Eur., N. Amer., Afr., 
Austral., Japan. 
C. Regnelli Wille. Loc. 5. Distr. General (incl. Ceylon). 
C. PRiEGRANDE Lund. Loc. 56. Distr. Eur., Greenland. 
C. humile (Gay) Nordst. Loc. 1. • Distr. General. 
C. Pardalis Cohn. Loc. 6, 9. Distr. Tropics of Old and New 
World. 
C. pseudobroomei Wolle. The specimens from the canal near 
Bentota showed rather larger granules than in the one figured by 
W. & G. S. West. These authors find the granulation to be variable 
in C. pseudobroomei, and we have therefore no hesitation in referring 
our specimens to this species. Loc. 24, 35. Distr. Largely tropical 
(incl. Ceylon). 
Xanthidium Ehrenb. 
X. armatum (Breb.) Rabenh. Loc. 6, 9, 56. Distr. General. 
X. ANTiLOPiEUM (Breb.) Kuetz. Loc. 27, 56. Distr. General. 
Artiirodesmus Ehrenb. 
A. Incus (Breb.). Loc. 23, 56. Distr. General. 
