Pseudodifflugia terricola  Bonnet & Thomas, 1960 *)
Basionym: Pseudodifflugia gracilis Schlumberger var. terricola Bonnet & Thomas, 1960

Diagnosis: Shell small, generally twice as long as wide, with a circular cross‑section giving the appearance of a classic Difflugia but of reduced size. Pseudostome circular, acrostome. Inside the shell, brownish membranous patches frequently occur, partly limiting or even apparently closing the aperture like an epiphragm; these structures likely represent remnants of cysts, which are common in this variety. Shell covering composed of heterogeneous siliceous granules: large stony plates mixed with very fine elements. Refringence low; the shell is often visible mainly because of its colour.

Dimensions: shell length 23–35 µm; width 15–20 µm.

Ecology: humus of Ericaceae throughout the subalpine zone of the Pyrenees.

Remarks: Bonnet & Thomas place this form in Pseudodifflugia rather than Difflugia, although pseudopodia were not observed. Their reasoning is based on the strong resemblance to Pseudodifflugia gracilis, the improbability of strictly terricolous Difflugia, the small size, and the frequent occurrence of cyst formation, which is more typical of Filosa acrostomes than of Lobosa acrostomes.

*) Taxonomic note: Pseudodifflugia gracilis var. terricola is changed to Pseudodifflugia terricola.
Because the name was published before 1961 using the abbreviation var., it is deemed subspecific under Article 45.6.4, unless explicitly proposed as infrasubspecific. As a species-group name, it is simultaneously established at both species and subspecies rank under the Principle of Coordination (Art. 46.1), with identical authorship, date, and type. Accordingly, when treated at species rank, the valid name is Pseudodifflugia terricola Bonnet & Thomas, 1960.