Sulcatae

Lobban, Christopher S., 2015, Benthic marine diatom flora of Guam: new records, redescription of Psammodictyon pustulatum n. comb., n. stat., and three new species (Colliculoamphora gabgabensis, Lauderia excentrica, and Rhoiconeis pagoensis), Micronesica 2015 (2), pp. 1-49 : 8

Section Sulcatae

Ref. illus.: Hustedt 1931 –1959, fig. 983; Witkowski et al. 2000, pl. 83, figs 5, 6; Loir & Novarino 2013, pl. 19c

Sample: GU52P-1, GU52P-9

Dimensions: Length 10–17 µm, width 5.5–6.5 µm; striae 27 in 10 µm, radiate

Diagnostics: Small valves, elliptical-lanceolate with slightly rostrate apices; central area extended into an H-shaped hyaline area. In our small cells, 1–2 large partecta in the middle flanked by 1–2 tapering partecta on each side and the H-shaped hyaline area is not evident externally.

Comments: These small specimens have chambers much like M. sergiana Pennesi & Poulin ( Lobban et al. 2012, pl. 36, figs 7, 8 and pl. 37 figs 1, 2), M. manokwariensis Cholnoky ( Lobban et al. 2012, pl. 32, figs 1–3), M. pusilla var. subcapitata Hustedt ( Hustedt 1931 –1959, fig 1002e, Loir & Novarino 2013, pl. 20b), and M. urveae Witkowski, Lange-Bertalot & Metzeltin ( Witkowski et al. 2000, pl. 84, figs 22, 23, Loir & Novarino 2013, pl. 24a, 27b). However, the elliptical valve outline and the distinct lyrate hyaline area distinguish it from each of these. M. urveae also differs in having parallel striae ( Witkowski et al. 2000). Larger size ranges for M. pumilla were given by Hustedt (1931 –1959) (20–20 x 5–9 µm) and Loir & Novarino (2013) (17.5–25 x 6.5–7.5 µm).