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Watanabe, Tsuyoshi, Nagumo, Tamotsu, Sun, Zhongmin, Hasegawa, Kazukiyo, Miyagawa, Tomofumi, Kumada, Misato, Tanaka, Jiro (2013): Morphology and taxonomy of Psammodiscus Round & Mann (Bacillariophyceae: Rhaphoneidales) with a description of the new species Psammodiscus calceatus. Phytotaxa 124 (1): 1-12, DOI: 10.11646/phytotaxa.124.1.1, URL: http://dx.doi.org/10.11646/phytotaxa.124.1.1

Psammodiscus nitidus (Gregory) Round & D.G. Mann (1980: 371) (Figs 1–18) Basionym: Coscinodiscus nitidus Gregory (1857: 499, pl. 10, fig. 45) TYPE:— UK: Scotland, Lamlash Bay (BM 1343, Hendey 1964: 76, syntype). Size and shape: Cells solitary, attached to sand grains (Figs 1a, b). Valves circular to slightly elliptic in valve view (Figs 2–4). Valve diameter 13.5–28.5 µm, 8–9 striae in 10 µm, 8 areolae in 10 µm (Table 1). Plastids and nucleus: Discoid plastids located along valve surface, number ca. 90 (Fig. 5). Nucleus lies at cell centre (Fig.5). Fine structures of valve: Valve face flat (Fig. 6), striae radiate, reaching mantle (Fig. 6). Areola on valve face (Figs 7, 8) and mantle (Fig. 8) occluded by rotae with 2–3 spokes. Internal views of small valves not observed. Larger valves (Figs 9 and 12) originate from same frustule. Striae and areolae of large valves morphologically similar to those in smaller valves (Figs 9–11); occasionally areola abnormalities visible (Fig. 10). Spokes in areolae not observed from internal view (Fig. 14). Rimoportula: Number of rimoportulae 0–2 (Figs 6, 12, 15) per valve. Rimoportula external opening located near valve centre (Figs 6, 7). Some valves lack central rimoportula (Fig. 15). In larger valves, external opening of rimoportula observed near valve margin (Fig. 10). In internal view, two rimoportulae located at opposite sides near valve margin (Figs 12–14). Rimoportula sessile with simple slit surrounded by ridge (Figs 13, 14). Central small pore: Central small pore located near valve centre (Figs 6, 7). Additional small pore: In larger valve, external opening of small pore observed near valve margin (Fig. 10). Additional small pore situated close to rimoportula near margin (Fig. 14). Cingulum: epicingulum consisting of three open bands: valvocopula (VC), second (2B) and third (3B) bands (Figs 17a, b). Valvocopula and second girdle bands open at 180° to each other (Figs 15, 16, 18). VC with two rows of pores (Fig. 16), its opening covered by ligula of 2B (Figs 16, 17a, 17b). 2B with single row of pores (Fig. 17a, b). 3B narrow with single row of triangular non-occluded pores (Figs 17a, b).