Neidium Undulatum Guide
Credit: Loren Bahls
  1. Valves elliptic-lanceolate
  2. Axial area wide
  3. Row of depressions along one side of raphe
  4. Central area diagonal, with depressions near margins
  5. Striae 10-12 in 10 µm

Neidium undulatum has large elliptic-lanceolate valves, 82-110 µm long. The apices are subrostrate. The axial area is wide with a row of depressions along one side of both raphe branches. The central area is diagonal, with disorganized depressions near the margins. Striae are coarse and number 10-12 in 10 µm.