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Guide to Planothidium joursacense

(Hérib.) Lange-Bert. 1999

Planothidium Joursacense Guide
Credit: Ian Bishop
  1. Valves elliptic
  2. Striae radiate
  3. Cavum present on rapheless valve
  4. Axial area rhombic on rapheless valve
  5. Central area bounded by 1-2 short striae

Valves are elliptic to elliptic-lanceolate, with broadly rounded ends. On raphe valve, striae are radiate throughout. The central area is bounded by 1-2 short, widely spaced striae. On the rapheless valve, striae are also radiate throughout. The axial area is rhombic and a cavum is present.