Centropyxis malvinensis Vucetich, 1975
Diagnosis: Test almost circular in outline, somewhat longer than wide. The pseudostome is slightly eccentric. The test is chitinoid, from yellowish to light brown and very transparent. Included in the organic part of the test are abundant siliceous plates, similar to those of C. aculeata, but smaller. On the surface of the test there are also few small exogenous particles with an irregular contour, somewhat more numerous in the posterior region, but they do not protrude from the contour of the test. Its most peculiar feature is the structure of the pseudostome: it is always circular and is surrounded by a rim or thick ring, darker than the rest of the test. From this flange split two very thin flanges that are attached to the side walls of the test. Several specimens were found with oval cysts surrounded by a thick membrane, occupying the entire region between the edge of the pseudostome and the posterior edge of the test. The rest of the individuals found had only vestiges of protoplasm inside them.
Dimensions: Length 76-82 µm; width 73-75 µm; height 30-45 µm; aperture 17-20 µm.
Ecology: Mosses on soil with little humidity. Kidney Island, Falkland Islands.
Remarks: The most similar species is C. laevigata Penard from which it differs for its much smaller height (C. laevigata is hemispherical or sub-spherical) by having a very marked chitinoid ring that borders the pseudostome and by having a less developed buccal tube, whose terminal part does not join with the anterior region of the teak.