Nitzschia soratensis

Valves with parallel sides and broadly rounded apices, becoming elliptical in smaller specimens (Figs 277-280). Frustules rectangular in girdle view with the canal raphe and fibulae clearly along one margin. Length: 5.6-15.6; width: 2.4-3.2; striae: 27.5-30 per 10 urn; fibulae: 10-12.5 per 10 urn. Striae parallel and composed of round areolae, which are slightly visible in larger specimens (Figs 253-256 and 277-280). The canal raphe runs along the margin of the valve and a small clear central area distinguished in some specimens (Figs 279). Fibulae com posed of small dots or squares and have an extended base at the valve face interior (Fig. 278).

Remarks. - In the SEM, the areolae are occluded by cribra, which are not frequently observed probably due to effects of treatment. The position of the cribra appears to be mid-way between the outer and inner areolar openings. Each stria from both valve face and valve mantle ends on two areolae as it approaches the canal raphe (Figs 277 and 279). The raphe runs along the margin of the valve at the point of transition between the valve face and valve mantle (Fig 279). The central raphe ends do not bend, whereas the terminal ends curve toward the mantle (Fig 279). Each stria ends in an enlarged areola at the valve mantle on the side opposite to where the canal raphe is located (Fig 280). The fibulae are rectangular and fused finger like projections attach them to the interior of the valve mantle and valve face (Plate 29, Fig. 2). The fibulae at the central area are slightly more separated leaving a small clear central area (Fig. 278). The girdle bands are closed and the valvocopulae have one row of wide poroids, which are not visible under LM (Figs 277, 279 and 280).

• Author
  Morales and Vis 2007
• Length Range
  5.6-15.6 µm
• Width
  2.4-3.2 µm
• Striae in 10µm
  27.5-30