Amphora ovalis (Kützing) Kützing 1844, p. 107; pl. 5, fig. 35, 39 Kützing, F.T. 1844 [ref. 000595]. Die Kieselschaligen. Bacillarien oder Diatomeen. Nordhausen. 152 pp., 30 pls.
Valves dorsi-ventral with a smooth and convex dorsal margin, a slightly concave ventral margin, and rounded apices. Length 30-105 µm, breadth 17-50 µm. Dorsal striae slightly radiate, composed of elongated areolae of various lengths. Striae number 10-13/10 µm. The areolae of the dorsal striae in the center of the valve next to the raphe are especially long. In valve view, the elongated areolae of the mantle can be observed along the dorsal margin of the valve, and the juncture of the valve face and mantle in this region appears as a narrow hyaline area. Ventral striae strongly radiate in the center of the valve, becoming parallel and eventually converging at the apices. Raphe eccentric, lying close to the ventral margin, filiform, and dorsally arched. Proximal and distal raphe fissures expanded and deflected toward the dorsal margin. Axial area narrow and follows the contour of the raphe. Central area or expanded fascia is present on the ventral side of the raphe only.