Plate P1. Thalassiosira bipora Shiono. 1. Whole valve showing rimoportula (R) (Sample 186-1151A-56R-CC); light microscope (LM). 2. Whole valve showing R (Sample 186-1151A-52R-CC); LM. 3, 4. Sample 186-1150B-5R-CC; scanning electron microscope (SEM); (3) external view of whole valve showing opening of R; (4) central area showing external openings of occluded areola (OC) and central fultoportula (CF). 5, 6, 7. Sample 186-1151A-54R-CC; SEM; (5) internal view of whole valve showing broken process of R; (6) central area showing OC and internal process of CF; (7) internal process of CF with four operculate structures (OP).

Plate P1. Thalassiosira bipora Shiono. 1. Whole valve showing rimoportula (R) (Sample 186-1151A-56R-CC); light microscope (LM). 2. Whole valve showing R (Sample 186-1151A-52R-CC); LM. 3, 4. Sample 186-1150B-5R-CC; scanning electron microscope (SEM); (3) external view of whole valve showing opening of R; (4) central area showing external openings of occluded areola (OC) and central fultoportula (CF). 5, 6, 7. Sample 186-1151A-54R-CC; SEM; (5) internal view of whole valve showing broken process of R; (6) central area showing OC and internal process of CF; (7) internal process of CF with four operculate structures (OP).