Achnanthes undulorostrata

Valves triundulate with broadly rounded ends, 30.5-35.5 µm long, 8.0-9.5 µm wide. Raphe valve with narrow axial area and a nearly rectangular central area extending to the valve margins. Raphe externally sinuous, with proximal ends deflected slightly in one direction, with distal ends curved strongly towards mantle in opposite direction (Fig. 63). Internal raphe slits with proximal ends slightly deflected to one side (Fig. 64). Rapheless valve with axial area near valve margin. Striae punctate, radiate throughout on raphe valve (Figs 55¬-58), on rapheless valve parallel in the center, becoming radiate with respect to the axial area, slightly to strongly curved at the ends (Figs 59-62, 65-66), 14-15 in 10 µm on raphe valve, 12-13 in 10 µm on rapheless valve. Intemal costae separating striae, wíth oblique ridges in rapheless valve resulting in a spiral pattern visible in SEM (Fig. 66). Puncta 16 in 10 µm on both valves.

• Author
  R.L.Lowe and A.R.Sherwood 2009
• Length Range
  30.5-35.5 µm
• Width
  8.0-9.5 µm
• Striae in 10µm
  14-15 in 10 µm on raphe valve, 12-13 in 10 µm on rapheless valve