FIGURES 145–152. SEM micrographs with details of the type material of Achnanthes minutissima Kütz. (isotype material, Kützing's Algarum Aquae Dulcis Germanicarum, Decade VIII, no. 75, Kützing 301). 145. Apice of a rapheless valve in girdle view, with the slit-like areolae in the mantle. 146. Apice of a rapheless valve in external view, with the rounded areolae in the apice and transapically elongated areolae in the valve margin. 147. Central area of a rapheless valve in external view. 148. Central area of a rapheless valve in internal view, with the areolae covered by hymenes. 149. Central area of a raphe valve in external view, showing the straight proximal raphe pores. 150. Central area of a raphe valve in a tilted internal view, with the proximal raphe pores slightly deflected in opposite directions. 151. Apice of a raphe valve in external view, with the distal ending slightly deflected. 152. Apice of a rapheless valve in internal view, with the areolae covered by hymenes. Scale bars = 1 μm.

Published as part of Novais, Maria Helena, Jüttner, Ingrid, Vijver, Bart Van De, Morais, Maria Manuela, Hoffmann, Lucien & Ector, Luc, 2015, Morphological variability within the Achnanthidium minutissimum species complex (Bacillariophyta): comparison between the type material of Achnanthes minutissima and related taxa, and new freshwater Achnanthidium species from Portugal, pp. 101-139 in Phytotaxa 224 (2) on page 110, DOI: 10.11646/phytotaxa.224.2.1, http://zenodo.org/record/13636829