Distomatopyxis couillardi Bonnet, 1970
Diagnosis: In dorsal and lateral view, it resembles a Cyclopyxis species. The ventral area invaginates into a wide vestibule with at the end an elliptical pseudostome with a short neck. The chitinous buccal skeleton comprises:
a. A double lower ring surrounding the base of the vestibule. Its two constituents clash in the plane of symmetry to form the support of a permanent diaphragm, of the same substance as the test, elliptical or circular, partially closing the entry of the vestibule. The latter communicates with the outside by two kidney-shaped openings giving the impression of a double pseudostome (diplostomy) and which can be obstructed at rest by a hyaline substance acting as an epiphragm (Figures L and S).
b. An elliptical ring, simple, reinforcing the edge of the pseudostome itself masked by the diaphragm.
c. A system of oblique flanges included in the wall of the vestibule and connecting the double lower ring to the upper ring.
The structure of the pseudostomal region gives the test a bilateral symmetry. Test covered with remodeled siliceous elements.
Measurements: Diameter of the test, measured on 30 individuals: 125 ± 2 µm; dorso-ventral distance: about 2/3 of the diameter; depth of the vestibule: 1/3 to 1/2 of the dorso-ventral distance.
Ecology: Soil. Philippines, Japan, Korea, North- and Central-America, Venezuela, Spain.