Difflugia corona Wallich, 1864
Diagnosis: Test sub-spherical to spherical with a variable number (0-20, mean 5) of conical hollow spines inserted from the mid-line to the fundus part. Test composed of fine mineral grains, rounded particles of quartz and parts of diatom frustules, all agglutinated by organic cement. Aperture terminal, circular, with 9 to 15 denticulate lobes.
Dimensions: 140-320 µm (Leidy); 200-250 µm (Penard); 180-310 µm (Awerinzew); 180-230 µm (Cash); 155-200 µm(Hoogenraad & De Groot); 80-380 µm (Lahr & Lopes); my measurements 105-193 µm, mean 156 µm.
Ecology: in sediments, in sphagnum, on waterplants, often very common. This species has been found in icefield lakes high in the mountains (Monti 1906).
Remarks: Sometimes the shell has a tubercular structure as in D. tuberculata. The number of conical spines I counted in Dutch specimen is mostly 4-6.