A–F LM photographs of P. pacificum A–D cleaned frustules showing parallel transverse striae under LM E valve center showing a roundish central area (arrowhead) F funnel-shaped terminal area in apical position G–L SEM photographs of P. pacificum G internal view of the whole valve H internal valve central area showing straight, slight expanded raphe fissures (arrowhead) and nodule bordered by two arched bars I internal raphe fissures terminate in helictoglossae at the apices (arrowhead) J external view of the whole valve showing the terminal fissures curving into opposite directions K external central area of valve showing straight, simple raphe fissures (arrowhead) L terminal fissures (arrowhead). Scale bars: 10 μm (A–F); 5 μm (G, J); 1 μm (H, I, K, L).