Difflugia difficilis Thomas, 1954
Diagnosis: Test ovoid, circular in cross-section. Aboral end of the test commonly with a not prominent, but rounded protuberance, sometimes replaced by a foreign body (diatom) which acts as the absent horn. The sides of the test converge towards the pseudostome to end in a short collar; the pseudostome is circular with a diameter varying between one-half and two-thirds of the width of the test. Test hyaline, clear, coated with siliceous particles, arranged regularly. Nucleus vesicular, spherical, with one central nucleolus and a more peripheral layer of granular material.
Dimensions: Length 83-93 µm; width 59-66 μm; pseudostome 20-27 µm; height of the collar, 6-9 μm. My measurements: L 80-117 µm; W 54-78 µm; pseudostome 26-32 µm; collar 4.7-7.4 µm high (n=6); nucleus 18.5-22.9 µm (n=2).
Ecology: Fresh water, sediment; France (1954), Belgium (Chardez, 1956), Africa (Gauthier-Lièvre et Thomas, 1958), the Netherlands (2019).