Diagnosis: Shell pyriform, circular in oral view, with a clear broad neck; shell covered with sand- or quartz-grains embedded in an organic cement; aperture circular; internally at the junction of the neck with a perforated diaphragm, with two holes.
Dimensions: Length 198-312 µm.
Ecology: In sediment of mesotrophic water bodies, Netherlands.
Remarks: It’s difficult to get a clear view of the diaphragm. Most often the diaphragm is obscured by debris in the neck.