FIG. 13 in A study of the morphology and distribution of four Achnanthidium Kütz. species (Bacillariophyta), implications for ecological status assessment, and description of two new European species

FIG. 13. — Achnanthidium neomicrocephalum Lange-Bert. & F.Staab: A, specimen from Loch Tarff, Scotland; B-D, specimens from Llyn y Fan Fawr, Wales; A-D, SEM views of rapheless valves; A, B, SEM external views of valves; C, SEM external view of valve pole; D, SEM external view of valve centre. Scale bars: A, B, 5 µm; C, D, 2 µm.