Protoplagiopyxis aperta Bonnet, 1974

Diagnosis: Shell large, very elongated, with simple plagiostome type tending towards the simple cryptostome type. In dorsal view, elliptical or oblong shape, more or less regular. In lateral view, ventral sole clearly individualized, flat except at the level of the ventral lip, where it bends moderately towards the inside of the shell. In ventral view, clearly visible pseudostome, located in the anterior 1/3 and often presenting a crescent shape with concavity turned forward, or an elongated kidney-shaped appearance. Dorsal lip not covering the ventral lip which is only slightly sloping. Transparent covering of large, irregular, reworked endogenous siliceous elements, with sometimes uncertain limits. Interstices occupied by very small siliceous elements and fine blackish particles, incorporated in a yellowish or light brown cement finely granular. Flaps of yellowish membrane sometimes adhere to the edge of the pseudostome (remains of epiphragm?).

Dimensions: Length 128-138 µm, width 85-88 µm.

Habitat: Humid and humic soils of gallery forest in the vicinity of backwater beds.