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Achnanthidium neomicrocephalum Lange-Bert. & F.Staab (Figs 9-13) Süsswasserflora von Mitteleuropa, Bacillariophyceae. 4. Teil Achnanthaceae: 431, pl. 89, figs 1-13 (Krammer & Lange-Bertalot 2004). DESCRIPTION LM (Fig. 9 A-DZ) Frustules slightly arched, with convex RL, concave RV.Valves linear-lanceolate. Margins slightly tapering towards small protracted, capitate poles. Valve margins slightly inflated in valve centre, sometimes more strongly on one side. Valve dimensions (n = 31): length 12-30.5 µm, width at valve centre 2-2.5 µm. On RV, central area small rounded, bordered by 1-2 slightly shortened, more widely spaced striae on each side, or small transverse fascia. Raphe filiform, straight, central pores terminating close to margin of central area. Central area on rapheless valve indistinct. Axial area narrow, linear on both valves, slightly widening towards valve centre. Striae radiate throughout on both valves, 30-32 in 10 µm (RV and RL). SEM (Figs 10 A-H; 11A-F; 12A-H; 13A-D) Raphe located on slightly raised sternum, terminal raphe fissures straight terminating at valve/mantle junction. Internally, central raphe endings shortly deflected to opposite sides. Striae composed of 2-3 areolae (RV and RL). Areolae round or oval adjacent to axial area, sometimes slit-like adjacent to valve margin. Row of transapically elongated areolae on mantle separated from areolae on valve face by hyaline area. |
