Staurosirella leptostauron

Valves are cruciform, 7-19 µm wide and 7-33 µm long. Valves with rounded ends. The central area is broad. The valve face is flat, or slightly undulate due to raised costae. The valve face/mantle junction forms a sharp angle. The abvalvar edge of the mantle is parallel to the valve face/mantle junction. In girdle view, frustules are rectangular. Cells form ribbon-like colonies, joined by linking spines. A cell within a colony is attached to the substratum by a mucilage pad, or cells may be planktonic. The axial area is linear to lanceolate. Striae are distinct, composed of lineolae. Lineolae are greatest in length midway between the sternum and valve mantle, 5-11 in 10 µm. Lineolae bear finely branched volae and may possess siliceous bridges between lineolae. Striae are parallel in the central area, becoming radiate near the valve ends. Striae extend onto the valve mantle. Costae are not as broad as the striae. Spines are flat, spatulate toward their ends and solid. Spines are present along the valve face edge, except at the apices, and are located on the costae between striae. Well-developed, ocellulimbus type, apical pore fields with round poroids are present. Pore fields are located at the junction between the valve face/mantle. Rimoportulae are absent. Copulae, or girdle bands, are closed and do not bear perforations. Valvocopulae are wider than other girdle elements and bear fimbriae (finger-like projections).