— 40 — 



Denticula Ktz. (1844). V. H. Traité p. 351. 



67. D. Van Heurckii Brun. Brim. 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. C. lleiieghiniana Ktz. A. S. Atl. tab. GGXXII, fig. 25. 

 Solitary in a sample from Lem Dan. 



Area: Europe. 



Coscinodiscus Ehr. (1838). V. H. Traité p. 525. 



69. C. lacustris Grim. var. australiensis Grim. Grün. 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 var., then Synedræ 

 and Eunotiœ. 



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, Nitzschia scalaris var., Nitzschia Tryblionella var. and 

 Coscinodiscus lacustris australiensis. The two Nitzschia however may 

 also be met with in freshwater. Also two marine forms have been 

 found in the same samples viz. Amphora acutiuscula and Nitzschiella 

 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 baccata, which I have only seen in samples from 

 waterfalls, more difficult to understand. This species is pre- 



