— 29 — 



Neidium Pfilzer (1871), CI. Syn. I, p. 67. 



2. N. afliue Ehr. var. geniiina CI. lorma minor. A. S. Atl. tab. XLIX, 

 iig. 23. 



Lem Dan (7 samples). 



Area: the main species: ul)iquitous. f. minor: Spitzl)ergen, Europe. Au- 

 stralia. 



3. N. Hitclicocliii Ehr. A. S. Atl. tab. XLIX, figs. 35-36. 

 Klong Son, Lem Dan (7 samples). 



Usually Nvith oblique strife, forming an angle of about 75° lo the 

 apical axis. 



Area: North America, Euiope, Bengal, Australia, New Zealand. 



Frustulia Ag. (1824), Gl. Syn. I, p. 121. 



4. ¥. rhomboides Ehr. V. H. Syn. tab. XVII, figs. 1—2. 



Found in many (20) of the samples. In some of them e. g. from Klong 

 Munse and Lem Dan not rare. 



var. saxouica Rabh. V. H. 1. c. fig. 4. 



Mixed with the main species. 



Area: the main species and the var. saxonica: America, Europe, Asia, 

 Australia. 



Stauroneis Ehr. (1843); cnfr. Gl. Syn. I, p. 141 Navicuke 

 microstigmaticce. 



5. Stauroneis anceps Ehr. var. hyalina Br. & Perag. Herib. Diat. 

 Auv. tab. Ill, fig. 19. 



Solitary in two samples from Lem Dan and Lem Ngob. 



Area: Europe (fossil), Australia. 



In a sample from Lem Dan I have found a Stauroneis, in its out- 

 ward form like St. anc. Ehr. var. amphicephala Ktz. (V. H. Syn. tab. IV, 

 fig. 5) but without any visible striation. 



Cymbella Ag. (1830), CI. Syn. I, p. 150. 



0. €. gracilis Rabh. cnfr. A. S. Atl. tab. X, fig. 39; tab. nost., fig. 3. 



Klong Prao, Klong Majum, Klong Munse, Lem Dan. 



I have figured this form because it diifers somewhat from the type 

 by its gibbous ventral margin. 



Area: Ci/mb. grac: Greenland, Europe, Tasmania. New Zealand; according 

 to Gleve (1. c. p. IfiO) especially in alpine regions. 



7. C. japonica Reichelt. Kunze Rev. Ill, p. 391. 



Klong Prao, Klong Majum, Klong Munse, Klong Son, Lem Dan. (7 samples). 



Area: Japan. 



