Plate 35. Ostreopsis siamensis. Figs. 1-6. SEM. Fig. 1. Epithecal view: cell broad and tear-shaped. Thecal surface smooth with scattered pores. Apical pore plate (Po) off-center (arrow). Narrow cingulum with smooth edge. Plate 1' narrow and pentagonal. Fig. 2. Hypothecal view: plate 1p long and pentagonal. Fig. 3. Po: long, curved and narrow. Fig. 4. Large and small pores on thecal surface. Fig. 5. Ventral view: location of ventral opening (arrow), ventral plate (asterisk), and rigid plate (arrowhead) on cingulum. Fig. 6. Hypothecal view: Vo (arrow) and Rp (arrowhead). Fig. 7. LM. Hypotheca. Fig. 8. Line drawing: thecal plate arrangement.