Quadrulella alata  Gauthier-Lièvre, 1957

Diagnosis: In frontal view, the test is lageniform, with a broadly rounded fundus (subcircular or ovoid) and a wide neck forming about a third of the total height; pseudostome slightly arched and bordered by a very thin chitinoid lip. Shell with a flat but probably not hollow keel which surrounds the test towards the base of the collar. Shell highly compressed in lateral view, claviform with ogival base terminated by a sharp nipple or foam; pseudostome slightly indented. Apical (or basal) elongated ellipsoid view with, at each end of the ellipse, the more or less acute projection of the keel.
Shell colorless or yellowish, very hyaline; covered with fairly large square plates, regularly arranged, juxtaposed or more or less overlapping. The keel is formed by two series (one for each side) of rectangular plates; on top of the fundus some thin plates are inserted in these rows giving in lateral view the appearance of a truncated nipple and not of an acute keel as in apical view. The insertion of the plates forming the keel is often marked by a bead of chitinoid cement.

Dimensions: According to Gauthier-Lièvre (1957): Shell length 140—150 µm; width 70—90 µm; thickness 48—50 µm; collar 15—55 µm high and 33—35 µm wide; aperture 30 µm; keel 5—10 µm wide.

Habitat: Freshwater. Marshy stream on Kalahari sands, rainforest.

Geographical distribution: Rep. of Congo: stream between Ewo and Etoumbi (about 25 km. From Ewo), quite rare, October. Republic of South Africa; Central America: Costa Rica (Kosakyan et al., 2025).