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Guide to Cosmioneis pusilla

(W.Smith) D.G.Mann and Stickle 1990

Cosmioneis pusilla guide
  1. Valves elliptic to elliptic-lanceolate
  2. Apices rostrate to capitate
  3. Striae radiate, punctate
  4. Central area round
  5. Proximal raphe ends expanded

Valves are elliptic to elliptic-lanceolate with strongly rostrate to capitate apices. The axial area is narrow, expanding to rounded central area. The raphe is straight with expanded external central endings and curved terminal fissures. Striae are punctate, radiate and slightly curved. Some striae in the valve middle are shortened.