Difflugia scalpellum Penard, 1899
Diagnosis: Shell bilateral symmetrical, cylindrical, gradually swelling from the aperture for about two-thirds of the body length to the broadest diameter and then tapering in the last third of the body length to a bluntly or sharply, asymmetrically shaped apex. Test composed of quartz particles and diatom frustules, giving it the appearance of a regular smooth surface. Aperture usually circular. Nucleus vesicular with central nucleolus.
Dimensions: Penard: length mean 220-300 µm; my measurements: 212-242 µm.
Ecology: in oligotrophic and mesotrophic ponds, between sphagnum; rare.
Remarks: this species was described and pictured by Ogden as Difflugia venusta Penard 1902, but his photomicrographs are quite different from Penards drawing and description.