Physochila cratera (Wailes, 1912) Kosakyan et al. 2023
Basionym: Nebela cratera Wailes, 1912

Diagnosis: Shell of moderate size, not compressed, pyriform, neck small and parallel; aperture bordered by a prominent collar semicircular in section. Normal plasma and pseudopodia.

Dimensions: Length 120-135 um; diameter 74-80 µm; neck about 30 µm in diameter and 30-35 µm in length. Aperture 25-35 µm in diameter; collar 30-40 µm in diameter.

Habitat: Submerged sphagnum. New Jersey, USA.

Remarks: This species belongs to the group of which p. tenella and P. griseola are the other members, but it exceeds them in size and is of quite distinctive shape. The test is formed of angular plates mixed with a few circular plates and diatoms; it is of a dark color, more or less opaque, and is very fragile. It is circular in transverse section.