Pontigulasia elisa Penard, 1893

Diagnosis: Shell pyriform, yellow brown, slightly bend with a constriction of the neck, faintly compressed in transverse section. Shell composed of mineral particles with diatom frustules, bound by a network of organic cement. Mostly some larger mineral grains are attached to the test. Aperture terminal, circular. The test is internally divided into two regions by a narrow bridge between the lateral walls.

Dimensions: Penard  85-120 µm; my measurements 114 µm.

Ecology: Freshwater, detritus

Remarks: observation of the internal bridge is very difficult, because you have to look through the aperture inside the test. That means that you have to manoevre the test in a vertical position with the aperture pointing up. I use a needle to move the test under the cover glass, but you also need some luck. Not seldom the bridge is obscured by particles in the aperture. If the test wall is not to opaque, you can see the bridge in lateral view. I use Aquamount to make the shell less opaque.