From Cavalier-Smith and Von der Heyden, 2007

 

 

Pterocystis devonica Cavalier-Smith and Von der Heyden, 2007

 

Diagnosis: radial scales (4-6 µm) with broad central rib tapering near the tip that has two asymmetric teeth (unlike striata), distally strongly curved to one side, and extending apically well beyond the lateral vanes, which have around 10 transverse ribs, but lack a distinctly thickened rim (unlike pteracantha and striata); base of shaft attached to a transverse thickening as in striata; wings with about 15-20 cross ribs, most resembling P. striata but wings have a different shape (being indented rather than bulging out distally) and extend only about one third up the scale (not over half way as in striata).
Plate scales oval (3-4 µm), sometimes slightly asymmetrical with central axial ridge.
Type locality: sediment, River Exe, Devon, UK.