Amphora delphinea var. minor

Valves have smoothly arched margins, with a slight inflation at mid-valve. Valves at the lower end of the size range are slightly convex on the dorsal side. Apices are bluntly rounded, and positioned toward the ventral side. The axial area is narrow, and parallel to the raphe. The proximal raphe ends are positioned near the ventral margin. The raphe is oblique and runs from near the ventral margin to around the dorsal side passing onto the dorsal mantle. The external proximal raphe ends are slightly deflected to the ventral side. The raphe appears to be simple and straight.

The striae are uniseriate and composed of round areolae. On the dorsal side of the raphe, the striae are nearly parallel to radiate. On the ventral side of the raphe, the striae are scattered and disorganized near the central nodule. Striae are slightly divergent and may be curved. The Voigt discontinuity is distinctly marked by up to several branching striae. Distal to the Voigt discontinuity, the striae are divergent. The fascia extends through the central nodule to at least over the dorsal margin, perhaps further. The fascia is distinctly rectangular and thickened. The fascia is absent on the ventral side.

This taxon clearly belongs to a distinct group of species that should be considered as a new genus, not within Amphora. Members of this group are found in Lake Baikal, Siberia; Japan; Miocene fossil deposits of eastern Europe (Levkov et al. 2009).