1–4 Achnanthidium minutissimum (6955, 6956, 6957) 5 Planothidium lanceolatum (6958) 6, 7 Psammothidium helveticum (6959) 8 Eucocconeis laevis (6956) 9 Eucocconeis alpestris (6956) 10, 11 Achnanthidium gracillimum (6956) 12 Eunotia valida (6956) 13, 14 Eucocconeis flexella (6957) 15–19 Cocconeis placentula var.? (6956, 6957, 6958) 20–26 Eunotia arcus or Eunotia arcubus Nörpel-Schempp & Lange-Bertalot (6957). Scale bar: 10 µm.