THE FRESHWATER ALGA OF CEYLON. 147 
Genus Evastrum, Ehrenb. 
100. Evastrum DIDELTA, Ralfs, 1844; Brit. Desm. 1848, p. 84, t. xiv. fig. 1. 
Hab. Paddyfields, Heneratgodha. 
101. EUASTRUM DIDELTOIDES, sp. n. (Pl. 19. fig. 12.) E quadriceps, Nordst., forma 
dideltoides, Racib. in Rozpraw. Wydz. matem.-prz. Akad. Umiej. Krakow, tom. xxiv. 
p. 979, t. 2. fig. 31. E mediocre, 2-21-plo longius quam latum, profundissime 
constrictum, sinu angusto-lineari ; semicellule pyramidato-triangulares, angulis 
basalibus subrectangularibus, lateribus leviter concavis cum undulo lato singulo 
supra et prope angulos basales; lobo polari producto truncato, leviter dilatato eum 
angulis rotundatis, in medio apicis incisura subprofunda lineari; tumore singulo 
supra isthmum, tumore singulo intra angulum basalem utrinque, in centro semi- 
cellularum tumoribus parvis binis transverse dispositis et scrobiculis magnis binis 
verticaliter dispositis; a vertice vis: late ellipticee, lateribus subtriundulatis, lobo 
polari globoso-elliptico in medio constricto ; membrana minute punctata. 
Long. 127-170 » ; lat. 58-824; lat. lob. polar. 24-28 w ; lat. isthm. 16-25 4; crass. 38 y. 
Hab. Paddyfield between Kosgoda and Urahaighasmahendai. 
The plant we found from Ceylon was undoubtedly identical with that described from 
Australia by Raciborski as E. quadriceps forma dideltoides. Raciborski does not describe 
nor figure the vertical view of the plant in question, otherwise he would have observed 
that it could not possibly belong to E quadriceps, Nordst. 
E. dideltoides differs from E. quadriceps in being more elongate, in the different 
arrangement of the protuberances, and the presence of two very large scrobiculations. 
Moreover, the vertical view is quite different, being broadly elliptical with undulate 
margins (not rotundo-quadrate as in E quadriceps) ; also, the polar lobe when viewed 
from above is subglobose or very broadly elliptical, whereas that of E. quadriceps is 
subquadrate with concave sides. 
E. dideltoides should also be compared with E Didelía, Ralfs, and E. ansatum, Ehrenb., 
particularly the latter species, of which it is a close ally. 
102. Evastrum ANSATUM, Ehrenb. in Akad. Wissenschaft. Berlin, 1832, p. 82; Infus. | 
1838, p. 162, t. 12. fig. vi. 2; Ralfs, Brit. Desm. p. 85, t. 14. fig. 2. 
Hab. In stream, Victoria Park, Colombo.  Paddyfield between Kosgoda and Ura- 
haighasmahendai. Paddyfields, Heneratgodha. i 
103. EvAsTRUM GNATHOPHORUM, West & G. S. West, in Journ. Linn. Soc., Bot. xxxiii. 
1897, p. 100, t. 9. figs. 3, 4. 
Long. 654; lat. 314; lat. apic. 185; lat. isthm. 9:5 u. 
Hab. Paddyfields, Heneratgodha. Paddyfield between Kosgoda and Urahaighasma- 
hendai. 
SECOND SERIES.— BOTANY, VOL. VI. Y 
