A Altergracillima Guide Copy
Credit: Marina Potapova
  1. Valve ends narrowly rostrate to subcapitate
  2. Central area absent on both valves
  3. Striae parallel or slightly radiate throught both valves
  4. Striae 21-25 in 10 μm at valve center, 36-45 in 10 μm at valve apices

Valves linear-lanceolate with narrowly rostrate or subcapitate ends. The axial area is narrow and only slightly widened in the valve center. The central area is absent. The striae are parallel or slightly radiate throughout both valves, 21-25 in 10 μm in the center valve, 36-45 in 10 μm at the valve apices.