Frenopyxis laevigata  (Penard, 1890) Wanner et al., 2025
Basionym: Centropyxis laevigata Penard, 1890

Diagnosis: The shell is approximately hemispherical to subglobular, with a rounded dome whose apex is slightly displaced posteriorly. The aperture is slightly eccentric and situated at the base of a tubular invagination on the ventral side. The tube has irregular, jagged margins, and its distal portion extends into the shell, where it connects with the opposite shell wall via a broad, dark, chitinoid ribbon. At the junction where this ribbon fuses with the wall, it bears several amorphous internal scales that are thicker and sturdier than the surrounding shell. This “bridle” appears to exert tension on the shell wall, pulling it closer to the aperture. The anterior part of the shell, recognizable by the dark ribbon, loses its rounded outline and shifts toward the aperture. In frontal view, the invagination of the buccal membrane continues as a broad ribbon that merges with the membrane at the level of small stones adhered to it. The shell wall is punctuated and composed of yellowish chitin, overlaid with sparse, irregular amorphous scales that rarely overlap or touch.
(translated and adapted from Penard’s 1902 description).

Dimensions: According to Penard (1902), specimens from Bachet-de-Pesay measured 70–83 µm in diameter, while specimens from Tourbière de la Pile measured 120–135 µm.

Habitat: Originally described from Sphagnum near Wiesbaden, Germany. Penard (1902) reported this species mainly in Sphagnum and other mosses, more rarely in marshes.

Remarks: Based on Penard’s descriptions and illustrations, C. laevigata has been transferred to the genus Frenopyxis by Wanner et al. (2025). Many subsequent records of this species in faunal surveys and ecological studies are probably misidentifications. Verification is often impossible due to the absence of accompanying illustrations or micrographs.