Quadrulella longicollis Taranek, 1882
Diagnosis: Much larger than Q. symmetrica and with straight sides, usually without pronounced lips.
Dimensions: c. 150 µm.
Ecology: mosses, fresh water.
Remarks: The specimens below were collected from the Heelsumse Beek, a clear stream near the city of Arnhem. These shells were the only Arcellinida which were found in a thin layer of sediment in this oligotrophic stream, fed by pure groundwater. The shell length ranges from 69-147 µm. The two smaller ones are Q. symmetrica, the largest three are Q. longicollis. Kosakyan et al (2012) found genetic distances, up to 11%, between Q. symmetrica and Q. longicollis.