Arcella mitrata Leidy, 1876
Diagnosis: Shell balloon-shaped or polyhedral; height more or less the same as the diameter of the base; aperture circular, crenelated and usually averted within inverted funnel; protoplasmic body spheroidal, with ‘neck’ to aperture and cytoplasmic strands to test; six or more slender lobopodia.
Dimensions: Shell 100-162 µm high, 100-180 µm in diameter. My measurements: height 80-200 µm (mean 139 µm), 119-218 µm in diameter (mean 144 µm).
Ecology: Freshwater, in submerged Sphagnum and Utricularia. Rare.
Remarks: I have found this species in oligothrophic and mesotrophic shallow ponds, the bottom covered with sand and/or Sphagnum. Earlier reports for the Netherlands were given by Hoogenraad and De Groot, 1940.
Dutch locations: Groeneveld, Baarn; Hilversum, Bluk; Loofles, Harskamp; Diepveen, Dwingeloo; Fochteloërveen; Haaksbergerveen; Nunspeet, fen; Huizen, fen; Strabrechtse heide, Eindhoven (Wim van Egmond).