Difflugia pyriformis Perty, 1849
Description: Shell pyriform or sometimes irregular in shape, tapering evenly from the mid-body position to the aperture curving gracefully in the aboral region; shell usually with a rough surface, composed of quartz particles; aperture circular and surrounded by a regular arrangement of smaller quartz particles. A smooth cyst membrane seals the mouth of the aperture in some specimens.
Dimensions: Perty: 140-200 µm long; other workers: length 154-253 µm; breadth 90-153 µm; diameter of aperture 35-56 µm.
Ecology: sediments in ditches, lakes and rivers, also between wet Sphagnum.
Remarks: D. pyriformis is often confused with D. oblonga, but it differs significantly in shape and size. D. pyriformis has a pyriform shape, where D. oblonga is ovoid-elongate. According to Penard's (1902) description of D. pyriformis, he described that the shell was made mainly of angular pieces of quartz often with two or three larger pieces around the junction of the neck and body, that it seldom incorporated sediment or diatoms, and that the materials were joined by a clear cement which was not abundant and allowed the shell to break easily under pressure.