Neidiopsis Guide
Credit: Ditmar Metzelin
  1. Longitudinal lines present
  2. Proximal raphe ends straight or unilaterally deflected
  3. Distal raphe ends simply curved
  4. Striae uniseriate or biseriate

Valves are linear, linear-lanceolate, or linear-elliptic with variously protracted and obtusely rounded apices. A longitudinal, hyaline line runs from apex to apex along each side of the valve, interrupting the striae. Outer raphe branches are filiform. The proximal raphe ends are either straight or deflected to the same side. The proximal raphe ends are not expanded. Distal raphe ends are simply curved, rather than bifurcate. In some taxa, striae near the axial area are biseriate. The girdle is composed of a few perforated bands.

Neidiopsis contains the former Navicula levanderi Hustedt and its allies. Species within the genus are found in oligotrophic and low-conductivity lakes and ponds in northern and alpine regions. Representative species have been reported from the Northern Rocky Mountains, the Great Lakes, and the northeastern United States, as well as Arctic Canada, Greenland, and Siberia.

Neidiopsis differs from Neidium in the absence of longitudinal canals. Other features of Neidiopsis not shared by species of Neidium are simply curved (not bifurcate) terminal raphe fissures, unilaterally deflected proximal raphe ends and biseriate striae.