Plagiopyxis minuta Bonnet, 1959

Diagnosis: Shell clear, transparent, circular in shape in dorsal view. In lateral view, the ventral membrane shows only a tiny slope, and the dorsal membrane, curved like a visor, covers very little of the ventral membrane. The cryptostomy is therefore very weak. The slit of the pseudostome is extremely narrow and difficult to observe, but its presence is indicated by the limit, often sinuous, of the covering membrane. This membrane is indeed lined with siliceous elements arranged in a rather irregular fashion. Observed cyst ovoid, connected to the wall by rigid filaments.

Dimensions: Diameter 40—45 µm; height 20 µm.

Ecology: Soil. Relatively ubiquitous. In Pyrenean humic soils.

Remarks: The virtual absence of slope on the ventral surface, the irregular outline of the pseudostome. the small dimensions clearly separate this species from Plagiopyxis declivis. The absence of a “pigeon” at the end of the ventral side also distinguishes it from Plagiopyxis penardi, which, moreover, possesses a pseudostome of much less extent.