Figs 20–24 in Four new monoraphid diatom species (Bacillariophyta, Achnanthaceae) from the Maritime Antarctic Region

Figs 20–24. Achnanthes kohleriana Kopalová, Zidarova & Van de Vijver sp. nov. Scanning electron micrographs of the type population from Deception Island (South Shetland Islands, Antarctica). 20. SEM girdle view of an entire frustule. 21. SEM external view of a raphe valve. 22. SEM external detail of the areolae with the typical cribrate structure. 23. SEM external detail of the apex with the typical terminal orbiculus. 24. SEM internal view of an entire rapheless valve. Arrows show the rapheless sternum. Scale bars represent 10 µm for Figs 20, 21 & 24, 1 µm for Fig. 22 and 5 µm for Fig. 23.