Mastogloia binotata Cleve 1895

Mastogloia binotata (Grunow) Cleve 1895 (Figs 1–8)

Basionym: — Cocconeis binotata Grunow 1863, p. 145, pl. 4 (13), fig. 13a.

Synonym:— Cocconeis binotata var. stauroneiformis Grunow 1863, p. 145, pl. 4 (13), fig. 13b. Orthoneis binotata (Grunow) Grunow 1867, p. 15.

References:— Van Heurck 1880 –1885, pl. 28, fig. 7, as Orthoneis binotata; Van Heurck 1896, p. 284, pl. 29, fig. 815, as Orthoneis binotata; Peragallo & Peragallo 1897 –1908, p. 27, pl. 5, fig. 2, as Orthoneis binotata; Hustedt 1933, p. 470, fig. 889; Hendey 1964, p. 238, pl. 37, fig. 11; Cholnoky 1968, p. 41, fig. 38; Ricard 1973, p. 163, pl. 1, fig. 7; 1975, p. 51, pl. 2, figs 9–11; Stephens & Gibson 1979a, p. 500, figs 2–9; 1979b, fig. 4; Navarro 1983, p. 120, figs 18, 19; Kociolek et al. 1987, figs 1–23; Paddock & Kemp 1990, figs 112, 132; Hein et al. 1993, figs 12, 13; 2008, p. 60, pl. 34, fig. 7; John 1994, p. 192, fig. 18; Witkowski et al. 2000, p. 240, pl. 75, figs 15–18.

Material:— Sample from Calabria, Italy. SEM stub no. DISVAR-ANC59SP43.

SEM morphology:— Externally, the raphe-sternum is slightly transapically dilated at centre into a very thin lanceolate fascia that does not reach the valve margins (Figs 1, 2, 7). The raphe consists externally of two straight branches ending centrally and distally in apically expanded pores (Figs 1–3, 7). Internally, the straight raphe branches are bordered by ribs, which are slightly raised only at the central nodule and the helictoglossae at the poles (Figs 4, 5). The transapical striae (14–18 in 10 µm) are uniseriate and vary from parallel at centre to curved and radiate at poles, and they are crossed by a more or less quincunx pattern which is more evident near the apex (Figs 1, 7). The areolae forming the striae are both externally and internally circular, sunken onto the valve surface and occluded by vela with rotae, decreasing in size at the valve–mantle junction (Figs 1–5, 7, 8). There is only one large, rectangular and central partectum (1.9–2.8 µm in width) (Fig. 4, arrowhead) attached to each side of the valvocopula with a flange consisting in a series of very short costae and biseriate striae (Figs 4, 6, arrowhead). The partecta are ornamented on its surface with uni- to triseriate rows of small pores. Each partectum opens externally in the middle of the valvocopula through a large and elongate partectal pore (Fig. 7, arrowhead), while beyond one row of small pores is present. Length: 19.6– 27.3 µm; width: 11.4–16.4 µm (Table 1).