Denticula Ktz. (1844). V.H. Traité p. 351. 
67. D. Van Heurekii Brun. Brun. esp. nouv. tab. XIII, fig. 8 and 
tab. XIV, fig. 10. 
Solitary in a sample from Lem Dan. 
Area: Java. 
Cyclotella Ktz. (1833). V.H. Traité p. 445. 
68. (€, Meneghiniana Ktz. A.S. Atl. tab. CCXXII, fig. 25. 
Solitary in a sample from Lem Dan. 
Area: Europe. 
Coscinodiscus Ehr. (1838). V.H. Traité p. 595. 
69. ¢. lacustris Grun. var. australiensis Grun. Grun. Fz. Joseph-L. 
tab. IV, fig. 31. 
Lem Dan. 
Area: China, Australia. 
The material examined by me is not particularly rich neither 
in individuals nor in species and a few samples only make an 
exception from this. More important genera are: Frustulia, Gom- 
phonema, Eunotia, in some samples also Synedra. 
In samples from inland waterfalls in Koh Chang I especially 
found small Achnanthes and Cymbella gracilis vay., then Synedre 
and Hunotice. 
In samples from riverbeds or pools Anomoeoneis exilis is 
predominant. 
The samples from ricefields at Lem Dan are distinguished by con- 
taining some forms usually belonging to brackish water viz. Navicula 
Yarrensis, Niteschia scalaris var. Nitzschia Tryblionella var. and 
Coscinodiscus lacustris australiensis. The two Niteschia however may 
also be met with in freshwater. Also two marine forms have been 
found in the same samples viz. Amphora acutiusculu and Niteschiella 
longissima. As the shallow ricefields at Lem Dan are situated close 
upon the seacoast it is fairly explicable that such forms belonging 
to brackish water (and even a few marine forms) occur in the 
freshwater collections, but on the other hand is the presence of 
Achnanthes baceata, which I have only seen in samples from 
waterfalls, more difficult to understand. This species is pre- 
