THE FRESHWATER ALG;E OF CEYLON, 159 
leviter convexis, membrana supra centrum semicellularum valde incrassata lutea et 
scrobiculata, ad basin supra isthmum cum granulo magno; a vertice vise rhom- 
boideo-ellipticee, polis spinulatis, ad medium utrobique valde incrassatis; a latere 
visee subcirculares, seriebus distantibus 2 spinarum verticaliter dispositis et diver- 
gentibus apicem versus, granulo singulo utrobique prope isthmum. 
Long. sine spin. 29-33 », cum spin. 32:5-35 u; lat. sine spin. 23-25:5 4; lat. isthm. 
6°5-7°5 u; crass. 17 n. 
Hab. Paddyfields, Heneratgodha. Among Podostemons, Mahawelli Ganga, near 
Peradeniya. 
This species at first sight much resembles Xanthidium lepidum (see next species), but 
differs in its smaller size, its much more irregular spines, which are always large near the 
apical angles and very small near the basal angles. The spines near the basal angles are 
disposed irregularly, but become arranged in pairs towards the apex. The scrobiculate 
thickened area above the centre of the semicells is of quite a different nature from that 
of X. lepidum ; seen from the side or apex it possesses several very small protuberances, 
which are entirely absent from the corresponding area of JY. lepidum. Another 
distinguishing feature of X. ceylanicum is the large granule at the base of the semicells 
just above the isthmus. Also, the series of four large granules within the apex of 
X. lepidum are entirely wanting in X. ceylanicum. 
This species might also be compared with X. searsolense, W. B. Turn. 
Both X. eeylanicum and X. lepidum occurred in abundance in the same gathering, 
and could always be distinguished from one another at a glance. 
140. XANTHIDIUM LEPIDUM, sp. n. (Pl. 20. figs. 22,23.) XY. subparvum, circiter 11-plo 
longius quam latum (sine spinis), profundissime constrictum, sinu angusto-lineari 
extremo valde ampliato; semicellulz rotundato-pyramidate, lateribus convexis serie 
spinarum parvarum 5-6 instructis (nonnunquam cum spinis parvis 2-3 intra angulum 
inferiorem), apicibus leviter convexis serie granulorum depressorum magnorum 
4 infra et juxta marginem instructis, supra centrum membrana incrassata scrobi- 
culis 8-12 ornata; a vertice visse truncato-ellipticze, in medio utrobique incrassate, 
apicibus truncatis spinis duobus instructis; a latere vise truncato-ovat:e, seriebus 
subparallelis distantibusque 2 spinarum verticaliter dispositis, granulo singulo ad 
angulum unumquemque superiorem. 
Long. sine spin. 36-43 4; lat. sine spin. 26:5-28 u, cum spin. 32-365 4; lat. isthm. 
1-T5 u; crass. 175 u; long. spin. 1:8-3:8 u. 
Hab. Paddyfields, Heneratgodha. 
'This species approaches X. searsolense, W. B. Turn. (in K. Sv. Vet.-Akad. Handl. 1893, 
xxy. no. 5, p. 101, t. 13. fig. 8), but is somewhat larger in size, has a series of four 
flattened granules just within the apices instead of two emarginate processes, and 
possesses a thickened scrobiculated area just above the centre of the semicells, which 
is entirely absent from X. searsolense. : 
We find the outward form of X. lepidum somewhat variable, and it possesses either 
5 or 6 pairs of spines along each lateral margin. It is usually the smaller forms which 
