Slide number SZCZ 27553 at the repository of the University of Szczecin.

Sand and rubble of coral reef at Daun, Bawean Island, East Java, Indonesia.

The name of the species was derived from Latin meaning “densely packed.” This species has dense striation in the dorsal area.

The diatom species C.densestriata is found solely on Bawean Island and Tiga Warna Beach in East Java, Indonesia.

Light microscopy (Fig. 9A–M): The frustules are rectangular in girdle view, 1.8 μm deep, joining each other on the valve face (Fig. 9A). Valves exhibit asymmetry and are dorsiventral, characterized by a curved dorsal margin and a straight ventral margin. Some dorsal margins are slightly flat in the middle, as semi-lanceolate (Fig. 9C, G, J, K, M). Valve apices cuneate with dot-like helictoglossae. Raphe slits positioned on the ventral side close to the margin (Fig. 9B–E, H). The terminal raphe ends are closed. Valve length 10.7–17.5 µm, n = 15 and width 1.8–3.5 µm, n = 14. The striae on the dorsal side are indistinct.

Scanning electron microscopy (Fig. 9N–X): Valves semi-lanceolate, dorsiventral, with flat faces transitioning abruptly to dorsal and ventral mantles (Fig. 9N–Q). Short chains formed; plastid unknown. Externally, shallow fine radiate striae visible dorsally, absent ventrally (Fig. 9N). Linear pores present in rows on dorsal and ventral mantles (Fig. 9S, X). Internally, valve face lacks parallel striation; occluded pores as small protruding flaps on dorsal and ventral sides, density 40–50 in 10 µm dorsally, 40–55 in 10 µm ventrally. Raphe slits arcuate, deflected to same side. Internal raphe slightly terminated by indistinct helictoglossae toward dorsal side. Proximal raphe endings more distant internally (mean 1.5 µm, n = 14) than externally (mean 1.26 µm, n = 11). Central nodule indistinct. Girdle bands open, unperforated, comprising at least four cingula.