Progonoia musca (Gregory) Schrader (1971: 922)

Lobban, Christopher S., 2015, External ultrastructure of Progonoia diatreta sp. nov. (Bacillariophyta, Scoliotropidaceae) differs from P. musca and P. intercedens comb. nov., Phytotaxa 234 (3), pp. 246-254 : 247-248

Progonoia musca (Gregory) Schrader (1971: 922) ( Figs 1–4 )

Basionym: Navicula musca Gregory (1857: 476) non Donkin

Synonyms: Caloneis musca (Gregory) Cleve (1894: 65) , Oestrupia musca (Gregory) Hustedt (1935: 17)

The detail of the areolae ( Fig. 4 ) confirms that there is no break (neither a space, nor a longitudinal line) in the coarsely porate striae as seen in LM, in contrast to the distinct longitudinal line in P. intercedens ( Fig. 5 ) and the wider, sculpted line in P. diatreta sp. nov. ( Fig. 6 ) (details below).

Type:— UNITED KINGDOM. Arran. A micrograph of one of the two marked valves on BM 1557 is shown in Fig. 3 .

Reference illustrations:— Gregory 1857, pl. 9, fig. 6 (as Navicula musca ) (reproduced as Fig. 1 ); Schmidt 1874 –1959, pl. 160, fig. 10 (reproduced as Fig. 2 ); Schrader 1971, pl. 1, figs 1–3, pl. 2, figs 1–4, pl. 3, figs 1, 2, 9; Round et al. 1990, pp. 550–551, figs b–d (not identified to species).

Figures

FIGURES 1–3. Navicula musca. 1. Greville’s drawing in Gregory 1857. Photo from an original copy courtesy of Friedel Hinz.2. Drawing from Schmidt’s Atlas, pl. 160, fig. 10, captioned ‘N. musca Greg. “typus!”’ Photo by C. Lobban from the reprinted edition. 3. Specimen from BM 1557 marked by Greville as being N. musca (DIC). Scale bar on C = 10 μm.

FIGURES 4–6. Comparison of stria detail in differential interference contrast illumination, focus on the outer surfaces of the valves. 4. Authentic Navicula musca from BM 1557 (detail of 3); arrow indicates the large pores. 5. Progonoia intercedens from Guam; arrow indicates the large pores in the striae and arrowhead the rib separating the two alveoli. 6. Progonoia diatreta from Guam (detail of holotype); arrow indicates the rings of small pores around the edges of the alveoli, and arrowhead the wide, sculpted rib between the two alveoli. Scale bars = 2 μm.