Mastogloia crucicula (Grunow) Cleve 1895 var. crucicula (Figs 9–14) Basionym:— Orthoneis crucicula Grunow 1877, p. 143. Synonym: — Mastogloia quadrinotata Østrup 1904, p. 149, pl. 2 fig. 33. References:— Hustedt 1933, p. 475, fig. 894; Hendey 1970, p. 145, pl. 1, fig. 8; Ricard 1973, p. 164, pl. 3, fig. 11, non fig. 12; Stephens & Gibson 1979a, p. 502, figs 17–24, 1980, fig. 42; Tomàs 1982, pl. 4, fig. 9; Navarro 1983, p. 120, figs 30, 31; Paddock & Kemp 1990, figs 32, 63, 111, 134; Hein et al. 1993, figs 16, 17, 2008, p. 63, pl. 36, figs 6, 7; John 1994, p. 193, fig. 26; Witkowski et al. 2000, p. 242, pl. 75, figs 3, 14, as M. ovulum. Material:— Sample from Siladen, Indonesia. SEM stub no. DISVAR-ANS7SP4. SEM morphology:— The external valve surface shows a raphe-sternum that is transapically dilated at centre into a narrow fascia that extends almost up to the valve margins (Figs 9, 12, 14). The raphe consists externally of two straight branches which are ending centrally and distally in expanded pores (Figs 9, 10, 14). Internally, the raphe branches are straight and bordered by ribs which are ending at poles in distinct and slightly raised helictoglossae (Figs 11–13). The transapical striae (18–25 in 10 µm) are uniseriate and they vary from parallel at centre to radiate at apices (Figs 9, 12, 14). The external openings of the areolae are rounded with a siliceous more or less crescentic edged-flap covering them (i.e., vola) and facing the valve margin, except for the first longitudinal row bordering the raphe-sternum where the areolae open to the raphe (Figs 9, 10, 14). There are four, sometimes three, bilobed partecta (0.7–1.4 µm in width) which are located in each quadrant of the valve on the valvocopula (Figs 12, arrowhead, 13). Each partectum is ornamented with small pores arranged inwardly in parallel rows (Fig. 11) and communicating with the exterior through an elongate partectal pore positioned opposite to the concave side of the partectal lobe (Figs 13, arrowhead, 14). Length: 10.2–29.1 µm; width: 6.7–11.5 µm (Table 1).

Published as part of Pennesi, Chiara, Poulin, Michel, Hinz, Friedel, Romagnoli, Tiziana, Stefano, Mario De & Totti, Cecilia, 2013, Comparison of two new species of Mastogloia (Bacillariophyceae) with other small members of section Ellipticae, pp. 1-21 in Phytotaxa 126 (1) on page 5, DOI: 10.11646/phytotaxa.126.1.1, http://zenodo.org/record/5085212