THE FRESHWATER ALGZ OF CEYLON. 177 
not uncommon to find an example in which some angles are furnished with two spines 
and the others with three. 
223. STAURASTRUM FREEMANII, sp.n. (Pl. 21. fig. 21.) S. mediocre, pæne tam longum 
quam latum (sine spinis), profunde constrictum, sinu aperto; semicellulee obverse 
subsemicirculares, angulis in processus breves tenues solidos productis, apicibus 
processuum profunde bifureatis, aculeis latissime divergentibus, apicibus semicellu- 
larum subrectis parte mediana paullo elevata, angulis lateralibus elevationis spinis 
horizontalibus pr:editis; a vertice visse subanguste elliptieze, polis in processus breves 
produetis, spinis validis subdivergentibus binis infra basin processuum. 
Long. (sine spin.) 29,4; lat. sine proc. 324, cum proc. 634; lat. isthm. Un: 
crass. l4 u. 
Hab. Paddyfields, Heneratgodha. 
Var. TRIQUETRUM, var. n. (Pl. 21. fig. 22.) Var. paullo minor, semicellulis a vertice 
visis triangularibus ; ceteris ut in forma typica. 
Long. (sine proc.) 224; lat. sine proc. 25 u, cum proc. 49u; lat. isthm. Bn, 
Hab. With the typical form. 
Perhaps the nearest species to A. Freemanii is S. patens, W. B. Turn. (K. Sv. Vet. 
Akad. Handl. xxv. 1893, no. 5, p. 108, t. 14. fig. 21), from which it differs in its smooth 
lateral margins, its much more produced angles, and in the characteristic pairs of 
spines at the apices. The solid processes are also peculiar. 
224. STAURASTRUM ALTERNANS, Bréb. in Ralfs, Brit. Desm. 1848, p. 132, t. 21. 
fig. 7. 
Var. DIVERGENS, var.n. (Pl.21.fig. 18.) Var. minor, apicibus semicellularum concavis, 
angulis levissime dilatatis (subeapitatis) sursum leviter divergentibus ; a vertice visis 
ut in forma typica sed angulis levissime subcapitatis. 
Long. 17 p; lat. 17-18 p; lat. isthm. 5:5 y. 
Hab. With the preceding species. 
This variety may perhaps be S. sinense, Lütkem. (in Annalen des k. k. naturhist. 
Hofmuseums, Wien, xv. 1900, p. 124, t. 6. figs. 39, 40), but it differs from the latter 
in the form of its semicells. 
225. STAURASTRUM DILATATUM, Ehrenb. Infus. 1838, p. 143, t. 10. fig. 13; Ralfs, Brit. 
Desm. 1848, p. 133, t. 21. fig. 8. 
Var. OBTUSILOBUM, De Not. Desm. Ital. 1867, p. 53, t. 4. fig. 47; Nordst. in K. Sv. 
Vet.-Akad. Handl. xxii. 1883, no. 8, p. 41, t. 4. fig. 19. 
Long. 28:5 a; lat. 30-32 u; lat. isthm. 85 p. 
Hab. Paddyüelds, Heneratgodha.  Paddyfield between Kosgoda and Urahaighasma- 
hendai. 
