Cyclopyxis ambigua Bonnet & Thomas, 1960

Diagnosis: Shell chitinoid, light cracked, of general shape reminiscent of that of Geopyxella sylvicola Bonnet & Thomas, with which it may be confused. Pseudostome very slightly invaginated, rarely circular, very often small and irregular. Circular front view. Shell incorporated with irregular siliceous elements and frequently mixed with organic (e.g. fungal) particles as in Trigonopyxis arcula (Leidy).

Dimensions: According to Bonnet and Thomas (1960): Shell diameter 40—55 µm; height 42—45 µm; diameter aperture 10—15 µm.

Ecology: Species found in abundance in soil (granitic arena) under Polypodium sp.

Geographical distribution: Near the pass of the Descargue (Pyrénées-Orientales).

Remarks: Decloitre (1965) describes C. ambigua var. aplanata, which is characterized by its small size (12—15 µm).