Plagiopyxis oblonga var.  cryptostoma (Bonnet, 1959) Thomas and Bonnet, 1960
= Plagiopyxis declivis var. oblonga f. cryptostoma Bonnet (1959)

Diagnosis: The internal constitution of the test converges with that of Plagiopyxis callida, but in the latter species the ventral lip is invaginated deeper into the body. Frontal view and ventral view very similar to those of P. oblonga. The difference lies in the course of the ventral lip. There are two different heights of the ventral lip, depending on whether the test is seen ventrally, pseudostome in front or, on the contrary, dorsally.

Dimensions: Diameter 60 µm; height 40 µm, dorso-ventral (height) 30 µm.

Ecology: Soil. Relatively common in humic alpine soil on granite and in light undergrowth (Font-Romeu, Pyrénées-Orientales).

Remarks: The analogy between the ventral lip of this variety and that of P. callida only seems to result from a simple convergence. The external form of the test, absolutely similar to that of P. oblonga, makes it possible to see here a variety of the latter species.