Neidium Pfitzer (1871), Cl. Syn. I, p. 67. 
2. N. affine Ehr. var. genuina Cl. forma minor. A.S. Atl. tab. XLIX, 
fig. 23. 
Lem Dan (7 samples). 
Area: the main species: ubiquitous, f. minor: Spitzbergen, Europe, Au- 
stralia. 
3. N. Hitehcockii Ehr. A.S. Atl. tab. XLIX, figs. 35-36. 
Klong Son, Lem Dan (7 samples). 
‘Usually with oblique strie, forming an angle of about 75° to the 
apical axis. 
Area: North America, Europe, Bengal, Australia, New Zealand. 
Frustulia Ag. (1824), Cl. Syn. I, p. 121. 
4. VW. 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 
Munsé and Lem Dan not rare. 
var. saxonica Rabh. V.H. 1. c. fig. 4. 
Mixed with the main species. 
Area: the main species and the var. satonica: America, Europe, Asia, 
Australia. 
Stauroneis Ebr. (1843); enfr. Cl. Syn. 1, p. 141 Navicule 
microstigmatice. 
5. Stauroneis anceps Ehr. var. hyalina Br. & Perag. Heérib. Diat. 
Auv. tab. III, 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), Cl. Syn. I, p. 156. 
6. . gracilis Rabh. cnfr. A.S. Atl. tab. X, fig. 39; tab. nost., fig. 3. 
Klong Prao, Klong Majum, Klong Munsé, Lem Dan. 
I have figured this form because it differs somewhat from the type 
by its gibbous ventral margin. 
Area: Cymb. grac.: Greenland, Europe, Tasmania, New Zealand; according 
to Cleve (l.c. p. 169) especially in alpine regions. 
7. ©, japonica Reichelt. Kunze Rev. Ill, p. 391. 
Klong Prao, Klong Majum, Klong Munsé, Klong Son, Lem Dan. (7 samples). 
Area: Japan. 
. 
