Pinaciophora fluviatilis Greeff, 1873 sensu Penard, 1904
Diagnosis: Cells spherical to ovoid with a diameter ranging from 45-50 µm. The plate-scales are circular, discoid. 4-6 µm in diameter; they are flat and have commonly a distinct hexagonal pattern of large boles. 17-24 in number, mostly arranged in a regular 3-4-5-4-3 or a 4-5-6-5-4 sequence. Smaller perforations are irregularly distributed along the periphery.
Ecology: Fresh water; oligotrophic and mesotrophic watertypes; between water plants and on sediment of shallow waters. In marshes, canals, streams and rivers. Consuming detritus and algae. Reported from Germany Greeff, 1873, Rainer, 1968), Scandinavia (Thomsen, 1978), United Kingdom (Belcher and Swale, 1978), the Netherlands (Siemensma, 1991), Peru, Texas (Gaarder et al., 1976), Antarctica (Takahashi, 1981).
I found it at several locations, e.g. a small fountain fed by a small natural stream (Royal Palace het Loo) and in a large lake, the IJsselmeer, near Kornwerderzand, all in the Netherlands.